Srđan G. Aćimović

The bacterium Erwinia amylovora causes fire blight and continues to threaten global commercial apple and pear production. Conventional microbiology techniques cannot accurately determine the presence of live pathogen cells in fire blight cankers. Several factors may prevent E. amylovora from growing on solid culture media, including competing microbiota and the release of bacterial-growth-inhibitory compounds by plant material during sample processing. We previously developed a canker… Show more

The bacterium Erwinia amylovora causes fire blight and continues to threaten global commercial apple and pear production. Conventional microbiology techniques cannot accurately determine the presence of live pathogen cells in fire blight cankers. Several factors may prevent E. amylovora from growing on solid culture media, including competing microbiota and the release of bacterial-growth-inhibitory compounds by plant material during sample processing. We previously developed a canker processing methodology and a chip-based viability digital PCR (v-dPCR) assay using propidium monoazide (PMA) to bypass these obstacles. However, sample analysis was still time-consuming and physically demanding. In this work, we improved the previous protocol using an automatic tissue homogenizer and transferred the chip-based v-dPCR to the BioRad QX200 droplet dPCR (ddPCR) platform. The improved sample processing method allowed the simultaneous, fast, and effortless processing of up to six samples. Moreover, the transferred v-ddPCR protocol was compatible with the same PMA treatment and showed a similar dynamic range, from 7.2 × 102 to 7.6 × 107 cells mL−1, as the previous v-dPCR. Finally, the improved protocol allowed, for the first time, the detection of E. amylovora viable but nonculturable (VBNC) cells in cankers and bark tissues surrounding cankers. Our v-ddPCR assay will enable new ways to evaluate resistant pome fruit tree germplasm, further dissect the E. amylovora life cycle, and elucidate E. amylovora physiology, epidemiology, and new options for canker management. Show less

Bitter rot, caused by Colletotrichum species, is one of the most devastating summer rot diseases affecting apple production in the Eastern United States. Given the differences in virulence and fungicide sensitivity levels between organisms belonging to the acutatum species complex (CASC) and the gloeosporioides species complex (CGSC), monitoring their diversity, geographic distribution, and frequency are essential for successful bitter rot management. In a 662-isolate collection from apple… Show more

Bitter rot, caused by Colletotrichum species, is one of the most devastating summer rot diseases affecting apple production in the Eastern United States. Given the differences in virulence and fungicide sensitivity levels between organisms belonging to the acutatum species complex (CASC) and the gloeosporioides species complex (CGSC), monitoring their diversity, geographic distribution, and frequency are essential for successful bitter rot management. In a 662-isolate collection from apple orchards in Virginia, isolates from CGSC were dominant (65.5%) in comparison to the CASC (34.5%). In a subsample of 82 representative isolates, using morphological and multilocus phylogenetic analyses, we identified C. fructicola (26.2%), C. chrysophilum (15.6%), C. siamense (0.8%), and C. theobromicola (0.8%) from CGSC and C. fioriniae (22.1%) and C. nymphaeae (1.6%) from CASC. The dominant species were C. fructicola, followed by C. fioriniae and C. chrysophilum. C. siamense followed by C. theobromicola developed the largest and deepest rot lesions on Honeycrisp fruit in our virulence tests. Detached fruit of nine apple cultivars and one wild accession (Malus sylvestris) were harvested early and late season and tested in controlled conditions for their susceptibility to C. fioriniae and C. chrysophilum. All cultivars were susceptible to both representative bitter rot species, with Honeycrisp fruit being the most susceptible and M. sylvestris, accession PI 369855, being the most resistant. We demonstrate that the frequency and prevalence of species in Colletotrichum complexes are highly variable in the Mid-Atlantic and provide region-specific data on apple cultivar susceptibility. Our findings are necessary for the successful management of bitter rot as an emerging and persistent problem in apple production both pre- and postharvest. Show less

BACKGROUND
Spotted-wing drosophila, Drosophila suzukii, is a serious pest of thin-skinned fruits. Alternative methods to control this pest are needed to reduce insecticide use, including new repellents. Previous research demonstrated that D. suzukii adults use odor cues to avoid blueberries infected with the fungal pathogen Colletotrichum fioriniae, which causes the disease anthracnose. To identify novel D. suzukii repellents, we investigated the volatile emission from… Show more

BACKGROUND
Spotted-wing drosophila, Drosophila suzukii, is a serious pest of thin-skinned fruits. Alternative methods to control this pest are needed to reduce insecticide use, including new repellents. Previous research demonstrated that D. suzukii adults use odor cues to avoid blueberries infected with the fungal pathogen Colletotrichum fioriniae, which causes the disease anthracnose. To identify novel D. suzukii repellents, we investigated the volatile emission from experimentally-infected fruit, which were inoculated with C. fioriniae isolates in the laboratory, and from field-collected fruit, which were naturally infected and harvested from a field. We then tested the pathogen-induced volatiles on D. suzukii adult behavior.

RESULTS
Volatile emission was similar between all five C. fioriniae strains, with good agreement between experimentally-infected and field-collected berries. In total, 14 volatiles were found to be more abundant in infected versus uninfected fruit headspace. In multiple-choice bioassays, nine of the 14 volatiles elicited repellency responses from adult D. suzukii. These nine volatiles were further evaluated in dual choice assays, where all nine reduced fly capture by 43–96% compared to the control. The most repellent compounds tested were the esters ethyl butanoate and ethyl (E)-but-2-enoate, which were more or equally repellent to the known D. suzukii repellents 1-octen-3-ol, geosmin, and 2-pentylfuran. Dose–response assays identified concentration-dependent effects on D. suzukii repellency and oviposition when applied individually and consistent aversion observed across doses of a 1:1 blend.

CONCLUSION
We report two repellents from C. fioriniae-infected blueberries that could be useful semiochemicals for the behavioral manipulation of D. suzukii in the field. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. Show less

With the goal to develop management tools to mitigate the severity of shoot blight on pear caused by Erwinia amylovora and prevent fire blight canker development from infected shoots on pear tree wood, we evaluated five preventive treatments in inoculated experiments over 2-years. We focused on foliar spray and trunk injection applications of extract of giant knotweed, Reynoutria sachalinensis (RSE), as a plant resistance activator candidate and on comparisons to antibiotics. Five foliar… Show more

With the goal to develop management tools to mitigate the severity of shoot blight on pear caused by Erwinia amylovora and prevent fire blight canker development from infected shoots on pear tree wood, we evaluated five preventive treatments in inoculated experiments over 2-years. We focused on foliar spray and trunk injection applications of extract of giant knotweed, Reynoutria sachalinensis (RSE), as a plant resistance activator candidate and on comparisons to antibiotics. Five foliar applications of RSE (2.24 L/ha) on 6-year-old trees of cultivar ‘Bartlett’ resulted in 100% control of shoot blight severity and canker incidence in both years of evaluation. The RSE trunk injection in fall of the first year did not control the disease allowing 75% of shoot severity and 38.5% of canker incidence. The opposite happened in the second year, when we injected RSE in spring, providing 85.7% control of shoot blight severity and 89.8% control of canker incidence. Antibiotics oxytetracycline (OTC) and streptomycin (STM) did not provide consistent control in the second year in comparison to the first year. In the first year, both antibiotics, OTC (trunk injection and foliar spray) and STM were effective, providing 94.8%, 100% and 86.3% control of shoot blight, respectively. They also provided 100, 91 and 84% control of canker incidence, respectively. However, in the second they were not effective allowing 69 – 96% of shoot blight severity and 70–92% of canker incidence. Regardless of the inconsistency in the effectiveness of antibiotics, which are not recommended for shoot blight control due to risks of promoting antibiotic resistance, five preventive spray applications of RSE could be used on pear trees to prevent shoot blight and canker development. The RSE spray program we developed could serve as a valuable control tool that could help prevent sudden outbreaks of shoot blight during summer and pear tree death from fire blight cankers with no risk for pathogen resistance. Show less

A devastating outcome of fire blight in apple trees is the infection of rootstock, which leads to canker development. Fire blight cankers are infected zones of dead bark on perennial branches, trunk, or rootstock that develop after fire blight pathogen Erwinia amylovora invades wood. Cankers can girdle the trunk, branches and rootstock leading to tree death. An accurate diagnosis of trunk and rootstock blight is a top challenge for apple growers because fire blight cankers can be visually… Show more

A devastating outcome of fire blight in apple trees is the infection of rootstock, which leads to canker development. Fire blight cankers are infected zones of dead bark on perennial branches, trunk, or rootstock that develop after fire blight pathogen Erwinia amylovora invades wood. Cankers can girdle the trunk, branches and rootstock leading to tree death. An accurate diagnosis of trunk and rootstock blight is a top challenge for apple growers because fire blight cankers can be visually misdiagnosed with cankers caused by less frequent pathogens. In addition, detecting E. amylovora in apple rootstocks is essential because this pathogen also causes asymptomatic infections. Accurate fire blight diagnosis is necessary to inform the complete removal of infected trees from the orchard and help replanting efforts while preventing further pathogen dissemination. To determine apple tree losses caused by fire blight rootstock infections, PCR was used to detect E. amylovora in symptomatic and asymptomatic rootstocks for two years. Rootstock canker incidence and tree death were rated in selected infection foci on seven commercial apple orchards in New York. Each infection focus consisted of central rootstock-blighted tree and the nearest surrounding edge trees showing no rootstock blight. E. amylovora strains collected from these seven orchards and other orchards in New York were characterized. In the first year, most of the orchards showed E. amylovora detection rates of 10.7 – 45.3% in asymptomatic rootstocks on the edge trees immediately surrounding visibly infected i.e. rootstock-blighted central trees. One year later, 20.8 – 56.3% cankered rootstocks were detected on the edge trees and from zero to 35.4% dead edge trees were recorded. However, the PCR from sampled edge rootstocks one year later showed no pathogen detections. E. amylovora rootstock strains showed slight variability in enzymatic activity, copper sensitivity, virulence, and exopolysaccharide production. Show less

The genus Colletotrichum includes nine major clades with 252 species and 15 major phylogenetic lineages, also known as species complexes. Colletotrichum spp. are one of the top fungal plant pathogens causing anthracnose and pre- and post-harvest fruit rots worldwide. Apple orchards are imperiled by devastating losses from apple bitter rot ranging from 24 to 98%, which is a serious disease caused by several species of Colletotrichum. Bitter rot is also a major postharvest rot disease with C… Show more

The genus Colletotrichum includes nine major clades with 252 species and 15 major phylogenetic lineages, also known as species complexes. Colletotrichum spp. are one of the top fungal plant pathogens causing anthracnose and pre- and post-harvest fruit rots worldwide. Apple orchards are imperiled by devastating losses from apple bitter rot ranging from 24 to 98%, which is a serious disease caused by several species of Colletotrichum. Bitter rot is also a major postharvest rot disease with C. fioriniae leading to 2 – 14 % of unmarketable fruit in commercial apple storages. Dominant species causing apple bitter rot in the Mid-Atlantic U.S. are C. fioriniae from the Colletotrichum acutatum species complex (CASC), and C. chrysophilum and C. noveboracense from the C. gloeosporioides species complex (CGSC). C. fioriniae is the dominant species causing apple bitter rot in the Northeastern and Mid-Atlantic U.S. C. chrysophilum was first identified on banana and cashew but has been recently found as the second most dominant species causing apple bitter rot in the Mid-Atlantic. As the third most dominant pathogen, C. noveboracense MB 836581 was identified as a novel species in the CGSC causing apple bitter rot in the Mid-Atlantic.C. nupharicola is a sister group to C. fructicola and C. noveboracense, also causing bitter rot on apple. We deliver resources of 10 new genomes including two isolates of C. fioriniae, three isolates of C. chrysophilum, three isolates of C. noveboracense and two isolates of C. nupharicola collected from apple fruit, yellow waterlily and Juglans nigra. Show less

PATHMAP (Pathogen And Tree fruit Health MAP) is a smartphone application (app) and interactive dashboard developed specifically for support specialists, extension personnel, and university scientists supporting the tree fruit industry. The PATHMAP app collects detailed information about observed diseases, insect pests, and disorders and provides the option to attach photos. The data are then visualized using a graphical interface dashboard displaying an interactive color-coded map. Prior to the… Show more

PATHMAP (Pathogen And Tree fruit Health MAP) is a smartphone application (app) and interactive dashboard developed specifically for support specialists, extension personnel, and university scientists supporting the tree fruit industry. The PATHMAP app collects detailed information about observed diseases, insect pests, and disorders and provides the option to attach photos. The data are then visualized using a graphical interface dashboard displaying an interactive color-coded map. Prior to the development of PATHMAP, abundant tree fruit disorder data were collected each year, but a central interactive repository for archiving data and facilitating communication of field observations did not exist. PATHMAP has been beta tested by university extension personnel, private consultants, and university scientists to ensure usability and functionality. PATHMAP will be used within the tree fruit industry for monitoring known pest patterns, occurrences, and outbreaks of emerging pathogens. It will augment existing extension diagnosis listservs that have value in visual diagnosis but are cumbersome and have no archiving capabilities. Data obtained through the tool can be used in epidemiological meta-analyses and to develop new predictive models, and can serve as a platform to track emerging pathogens, insects, and disorders for a variety of cropping systems. Show less

Erwinia amylovora causes fire blight, a disease responsible for enormous economic losses in the pome fruit-producing areas where it is present. Despite the abundant research on fire blight, information about E. amylovora population dynamics and survival in fire blight cankers and the plant defense responses to this pathogen in the infected bark are limited. In our study, we obtained fire blight cankers in apple, pear, and Asian pear cultivars showing differing resistance to the disease by shoot… Show more

Erwinia amylovora causes fire blight, a disease responsible for enormous economic losses in the pome fruit-producing areas where it is present. Despite the abundant research on fire blight, information about E. amylovora population dynamics and survival in fire blight cankers and the plant defense responses to this pathogen in the infected bark are limited. In our study, we obtained fire blight cankers in apple, pear, and Asian pear cultivars showing differing resistance to the disease by shoot inoculation with E. amylovora. We collected cankers from irrigated and non-irrigated trees every 3 months in two independent field experiments and analyzed samples by viability digital PCR. We also assessed the expression of pathogenicity-related (PR) genes in the bark of selected apple and Asian pear cultivars. A logistic regression analysis revealed the impact of environmental and host factors on E. amylovora detection rates in cankers. The chances of detecting live E. amylovora cells in cankers increased significantly in those collected from irrigated trees, in July, and/or during an experiment performed in a year with an expected average rainfall when compared to samples from non-irrigated trees, collected in January, and/or during an experiment performed under environmental conditions dominated by drought. We found a positive correlation between the pathogen detection rates in cankers and the host resistance to fire blight that might be explained by lower E. amylovora survival rates in more damaged tissues of susceptible hosts. The genes PR-1, PR-2, PR-5, and PR-8 were induced in the bark surrounding apple and Asian pear fire blight cankers. Our study, involving the analysis of more than 800 canker samples, provides new knowledge about the fire blight disease cycle and lays the foundation for improved fire blight management and eradication strategies in pome fruit orchards. Show less

The accurate assessment of Erwinia amylovora live cell populations in fire blight cankers by classic microbiology methods has major limitations. Some of them are the presence of competitive microbiota in samples that inhibit E. amylovora’s growth and the release of toxic compounds by plant material during sample processing, which may hamper the pathogen’s ability to form colonies on solid media. Digital PCR (dPCR) combined with the photo-reactive DNA-binding dye propidium monoazide (PMA) allows… Show more

The accurate assessment of Erwinia amylovora live cell populations in fire blight cankers by classic microbiology methods has major limitations. Some of them are the presence of competitive microbiota in samples that inhibit E. amylovora’s growth and the release of toxic compounds by plant material during sample processing, which may hamper the pathogen’s ability to form colonies on solid media. Digital PCR (dPCR) combined with the photo-reactive DNA-binding dye propidium monoazide (PMA) allows selective detection and quantification of live E. amylovora cells in woody samples while overcoming the constraints of culture-dependent methods. This work describes a reliable viability dPCR procedure to determine E. amylovora live cell concentrations in fire blight cankers from pome fruit trees. This protocol can be adapted for the analysis of other types of plant material and enables investigation of ecological, epidemiological, and management significance of cankers as a relatively underexplored part of the fire blight disease cycle. Show less

Apple orchards with minimal or reduced fungicide inputs in the Mid-Atlantic region of the United States have experienced outbreaks of severe premature defoliation with symptoms that matched those of apple blotch disease (ABD) caused by Diplocarpon coronariae. Fungal isolates obtained from symptomatic apple leaves and fruit produced uniform slow-growing, dark-gray colonies on peptone potato dextrose agar and had conidia. Internal transcribed spacer DNA sequences matched with D. coronariae and… Show more

Apple orchards with minimal or reduced fungicide inputs in the Mid-Atlantic region of the United States have experienced outbreaks of severe premature defoliation with symptoms that matched those of apple blotch disease (ABD) caused by Diplocarpon coronariae. Fungal isolates obtained from symptomatic apple leaves and fruit produced uniform slow-growing, dark-gray colonies on peptone potato dextrose agar and had conidia. Internal transcribed spacer DNA sequences matched with D. coronariae and Koch’s postulates were fulfilled when typical ABD symptoms occurred when reinoculated onto apple leaves and fruit. Spore dispersal in nonfungicide-treated orchards detected with quantitative PCR was low in early spring and dropped to undetectable levels in late May and early June before rising exponentially to highs in July and August, which coincided with symptom development. Only low spore numbers were detected in fungicide-treated orchards and nearby forests. In preliminary fungicide tests, fluxapyroxad, thiophanate methyl, and difenoconazole effectively inhibited mycelial growth of isolates in vitro. When apple cultivars Fuji and Honeycrisp were inoculated with D. coronariae, Honeycrisp showed delayed onset of symptoms and lower disease severity, and the transcription profile of seven host defense-related genes showed that PR-2, PR-8, LYK4, and CERK1 were highly induced in Honeycrisp at 2 and 5 days postinoculation. This is the first report of ABD in the Mid-Atlantic United States, which includes studies of seasonal D. coronariae spore dispersal patterns, preliminary fungicide efficacy, and host defense-related gene expression to assist development of best ABD management practices. Show less

Apple growers in the Mid-Atlantic region of the U.S.A. have reported increased losses to bitter rot of apple. We tested the hypothesis that this increase is because the Colletotrichum population has developed resistance to commonly used single-mode-of-action (single-MoA) fungicides. We screened 220 Colletotrichum isolates obtained from 38 apple orchards in the Mid-Atlantic region for resistance to 11 fungicides in Fungicide Resistance Action Committee (FRAC) groups 1, 7, 9, 11, 12, and 29… Show more

Apple growers in the Mid-Atlantic region of the U.S.A. have reported increased losses to bitter rot of apple. We tested the hypothesis that this increase is because the Colletotrichum population has developed resistance to commonly used single-mode-of-action (single-MoA) fungicides. We screened 220 Colletotrichum isolates obtained from 38 apple orchards in the Mid-Atlantic region for resistance to 11 fungicides in Fungicide Resistance Action Committee (FRAC) groups 1, 7, 9, 11, 12, and 29. Eleven (5%) of these isolates were resistant to FRAC group 1 with confirmed β-tubulin E198A mutations, and two (<1%) were also resistant to FRAC group 11 with confirmed cytochrome-b G143A mutations. Such low frequencies of resistant isolates indicate that fungicide resistance is unlikely to be the cause of any regional increase in bitter rot. A subsample of isolates was subsequently tested in vitro for sensitivity to every single-MoA fungicide registered for apple in the Mid-Atlantic U.S.A. (22 fungicides; FRAC groups 1, 3, 7, 9, 11, 12, and 29), and 13 fungicides were tested in field trials. These fungicides varied widely in efficacy both within and between FRAC groups. Comparisons of results from our in vitro tests with results from our field trials and other field trials conducted across the eastern U.S.A. suggested that EC25 values (concentrations that reduce growth by 25%) are better predictors of fungicide efficacy in normal field conditions than EC50 values. We present these results as a guideline for choosing single-MoA fungicides for bitter rot control in the Mid-Atlantic U.S.A. Show less

To reduce the severity of shoot blight and prevent the resulting development of cankers on perennial apple wood, we evaluated eight fire blight post-infection spray programs of prohexadione-calcium (PCA) alone or with acibenzolar-S-methyl (ASM) over two years. On mature trees of cv. Royal Court, a single application of the high PCA rate (247 mg/L) at 2 to 3 days after inoculation resulted in 89.5 and 69.5% reduction of shoot blight severity after inoculation. Two applications of PCA 247mg/L, 12… Show more

To reduce the severity of shoot blight and prevent the resulting development of cankers on perennial apple wood, we evaluated eight fire blight post-infection spray programs of prohexadione-calcium (PCA) alone or with acibenzolar-S-methyl (ASM) over two years. On mature trees of cv. Royal Court, a single application of the high PCA rate (247 mg/L) at 2 to 3 days after inoculation resulted in 89.5 and 69.5% reduction of shoot blight severity after inoculation. Two applications of PCA 247mg/L, 12 or 14 days apart, with the first one applied 2 to 3 days after inoculation, resulted in 78.8 and 74.5% reduction of shoot blight severity in both years. A 100% control of canker incidence on perennial wood from infected shoots in both years was achieved with a single application of PCA (247mg/L) applied at 2 or 3 days after the inoculation, while three applications of PCA (125 mg/L) + ASM (25mg/L) 12 – 16 days apart, reduced canker incidence by 83.5 and 69% in the two years. The other programs with lower PCA rates and frequencies of application reduced shoot blight severity for 50.8 and 51.8% (PCA) and for 62.6 – 72% and 59.3% (PCA + ASM), over two years, respectively. Reduction of canker incidence on wood by other programs was 66.5% and 69 – 90.4% in the two years, respectively. As fire blight cankers lead to death of dwarf apple trees and serve as primary sources of inoculum, our effective PCA and PCA + ASM programs could serve as viable post-infection management options. These treatments can reduce or prevent canker development and thus significantly abate tree losses in high-density apple orchards after fire blight epidemics occur. Show less

Apple blotch (AB) caused by Diplocarpon coronariae (Dc) has been established in Europe since 2010. AB is a serious apple disease, mostly in low input orchards and in cider production areas in Northern Italy, Switzerland, Austria and Germany. However, the epidemiology and population genetic structure of this pathogen is unknown. We developed twelve Dc-specific microsatellite markers and screened DNA of both pure fungal isolates and infected apple leaves. The marker data of 313 European samples… Show more

Apple blotch (AB) caused by Diplocarpon coronariae (Dc) has been established in Europe since 2010. AB is a serious apple disease, mostly in low input orchards and in cider production areas in Northern Italy, Switzerland, Austria and Germany. However, the epidemiology and population genetic structure of this pathogen is unknown. We developed twelve Dc-specific microsatellite markers and screened DNA of both pure fungal isolates and infected apple leaves. The marker data of 313 European samples of Dc were compared to Dc isolates from Asia (n = 7) and the USA (n = 3). We found 31 distinct multilocus genotypes (MLGs) in European samples, and seven additional MLGs in the Asian and USA samples. The European samples had the typical genetic signature of a recently introduced species including high clonality, a low number of private alleles and one dominant MLG across all the sampling sites. All European MLGs were genetically distant from those MLGs of Asian and USA origin. Based on the lack of linkage disequilibrium observed, there is evidence that Dc undergoes regular cycles of sexual recombination in the European population, although the sexual stage (apothecia) has not been observed in Europe. The twelve newly developed SSR markers reported here provide a useful tool to characterize the population genetic diversity and structure of Dc in Europe. Our study supports the hypothesis that Dc is a recently introduced pathogen in Europe, but of currently unknown origin. Dc has a large effective population size during field epidemics, so we believe that the pathogen has substantial evolutionary potential. Application of the SSR markers to large-scale and diverse Dc samples will help to better understand the epidemiology of AB, which has become a global apple disease, and will help guide effective mitigation strategies based on disease management and resistance breeding. Show less

The brown marmorated stinkbug Halyomorpha halys, is an invasive pest that causes millions of dollars of crop damage each year in the US. A promising biocontrol agent for this pest is the samurai wasp, Trissolcus japonicus, which is a potential long term control method with few negative ecological impacts. However, the wasps’ small size of only 1 mm in length can make it difficult to identify morphologically. We developed a DNA-based approach to determine whether a wasp specimen is T. japonicus… Show more

The brown marmorated stinkbug Halyomorpha halys, is an invasive pest that causes millions of dollars of crop damage each year in the US. A promising biocontrol agent for this pest is the samurai wasp, Trissolcus japonicus, which is a potential long term control method with few negative ecological impacts. However, the wasps’ small size of only 1 mm in length can make it difficult to identify morphologically. We developed a DNA-based approach to determine whether a wasp specimen is T. japonicus using conventional methods of DNA extraction, PCR, and gel electrophoresis. When tested against eight families of Hymenoptera, including three Trissolcus species, our method identified samurai wasp samples with 100% accuracy. Additionally, in silico analyses of various T. japonicus sequences provide evidence that the method will work throughout the US, Europe, and parts of Asia. We expect that this method will be a valuable tool for reliably identifying T. japonicus during distribution and recapture efforts to assess its survival, establishment, and dispersal for biocontrol purposes. Show less

Apple growers in the Mid-Atlantic region of the United States have been reporting an increase in losses to bitter rot of apple and are requesting up-to-date management recommendations. Management is complicated by variations in apple cultivar susceptibility, temperature and rainfall, and biology of the Colletotrichum species that cause bitter rot. Over 500 apples with bitter rot were obtained from 38 orchards across the Mid-Atlantic and the causal species identified as C. fioriniae and C… Show more

Apple growers in the Mid-Atlantic region of the United States have been reporting an increase in losses to bitter rot of apple and are requesting up-to-date management recommendations. Management is complicated by variations in apple cultivar susceptibility, temperature and rainfall, and biology of the Colletotrichum species that cause bitter rot. Over 500 apples with bitter rot were obtained from 38 orchards across the Mid-Atlantic and the causal species identified as C. fioriniae and C. nymphaeae of the C. acutatum species complex and C. chrysophilum, C. noveboracense, C. siamense, C. fructicola, C. henanense, and C. gloeosporioides sensu stricto of the C. gloeosporioides species complex, the latter two being first reports. Species with faster in vitro growth rates at higher temperatures were more abundant in warmer regions of the Mid-Atlantic, while those with slower growth rates at higher temperatures were more abundant in cooler regions. Regional bloom dates are earlier and weather data shows a gradual warming trend that likely influenced, but was not necessarily the main cause of the recent increase in bitter rot in the region. A grower survey of apple cultivar susceptibility showed high variation, with the increase in acres planted to the highly susceptible cultivar ‘Honeycrisp’ broadly corresponding to the increase in reports of bitter rot. These results form a basis for future studies on the biology and ecology of the Colletotrichum species responsible, and suggest that integrated bitter rot management must begin with selection of less-susceptible apple cultivars. Show less

Apple bitter rot caused by Colletotrichum species is a growing problem worldwide. Colletotrichum spp. are economically important but taxonomically un-resolved. Identification of Colletotrichum spp. is critical due to potential species-level differences in pathogenicity-related characteristics. A 400-isolate collection from New York apple orchards were morphologically assorted to two groups, C. acutatum species complex (CASC) and C. gloeosporioides species complex (CGSC). A sub-sample of 44… Show more

Apple bitter rot caused by Colletotrichum species is a growing problem worldwide. Colletotrichum spp. are economically important but taxonomically un-resolved. Identification of Colletotrichum spp. is critical due to potential species-level differences in pathogenicity-related characteristics. A 400-isolate collection from New York apple orchards were morphologically assorted to two groups, C. acutatum species complex (CASC) and C. gloeosporioides species complex (CGSC). A sub-sample of 44 representative isolates, spanning the geographical distribution and apple varieties, were assigned to species based on multi-locus phylogenetic analyses of nrITS, GAPDH and TUB2 for CASC, and ITS, GAPDH, CAL, ACT, TUB2, APN2, ApMat and GS genes for CGSC. The dominant species was C. fioriniae, followed by C. chrysophilum and a novel species, C. noveboracense, described in this study. This study represents the first report of C. chrysophilum and C. noveboracense as pathogens of apple. We assessed the enzyme activity and fungicide sensitivity for isolates identified in New York. All isolates showed amylolytic, cellulolytic and lipolytic, but not proteolytic activity. C. chrysophilum showed the highest cellulase and the lowest lipase activity, while C. noveboracense had the highest amylase activity. Fungicide assays showed that C. fioriniae was sensitive to benzovindiflupyr and thiabendazole, while C. chrysophilum and C. noveboracense were sensitive to fludioxonil, pyraclostrobin and difenoconazole. All species were pathogenic on apple fruit with varying lesion sizes. Our findings of differing pathogenicity-related characteristics among the three species demonstrate the importance of accurate species identification for any downstream investigations of Colletotrichum spp. in major apple growing regions. Show less

Diplodia tip blight (Diplodia pinea) affects mature pines, including Austrian (Pinus nigra) and Ponderosa (P. ponderosa) pines. Infections spread from needle fascicles to branch and, if unchecked, to the entire tree. Efficacy studies of fungicide injections in conifers are limited. Minute vascular tissues and resin exudate, a response to drilling, present impediments to injection. The efficacy of Propizol (14.3% propiconazole) for control of Diplodia tip blight in Austrian pines was evaluated… Show more

Diplodia tip blight (Diplodia pinea) affects mature pines, including Austrian (Pinus nigra) and Ponderosa (P. ponderosa) pines. Infections spread from needle fascicles to branch and, if unchecked, to the entire tree. Efficacy studies of fungicide injections in conifers are limited. Minute vascular tissues and resin exudate, a response to drilling, present impediments to injection. The efficacy of Propizol (14.3% propiconazole) for control of Diplodia tip blight in Austrian pines was evaluated. We evaluated (1) time of year, (2) injection spacing, and (3) fungicide dilution with respect to injection efficiency. Late fall injections expedited uptake, which is consistent with the reduced monoterpene emission rates in autumn and winter reported by Kim et al. 2005 and Lim et al. 2008. The time required for the dose to be administered was recorded for close and wide spacing of injection sites. Close spacing had the greatest impact on reducing the application time, irrespective of time of year. Low volume injections required less time to apply compared to high volume. Regardless of the application method, we observed a significant decrease in disease incidence in Propizol-treated trees. Injections applied in late fall resulted in a mean reduction in infections of new candles in the next growing season. Injections in the following spring, however, did not result in improvement in candle condition until a year later. We believe that these differences are based on whether the fungicide was applied prior to or after infection. Based on these findings, we recommend Propizol prior to infection for optimal results. Show less

Fire blight is a devastating disease of apple and pear caused by the bacterium Erwinia amylovora. One of its main symptoms is canker formation on perennial tissues which may lead to the death of limbs and/or the entire tree. E. amylovora overwinters in cankers which play an important role in initiating fire blight epidemics. However, knowledge of pathogen biology in cankers is scarce, in part due to limitations of classical microbiology methods and the inability of most molecular techniques to… Show more

Fire blight is a devastating disease of apple and pear caused by the bacterium Erwinia amylovora. One of its main symptoms is canker formation on perennial tissues which may lead to the death of limbs and/or the entire tree. E. amylovora overwinters in cankers which play an important role in initiating fire blight epidemics. However, knowledge of pathogen biology in cankers is scarce, in part due to limitations of classical microbiology methods and the inability of most molecular techniques to distinguish live from dead cells. In this work, a viability digital PCR (v-dPCR) protocol using propidium monoazide (PMA) was developed, allowing for the first time the selective detection and absolute quantification of E. amylovora live cells in apple and pear cankers collected in two time periods. Some key factors affecting the v-dPCR performance were the maceration buffer composition, the target DNA amplicon length, the thermal cycle number and the use of sodium dodecyl sulfate or PMA enhancer for Gram-negative bacteria to improve the effect of PMA. In the future, this methodology could shed light on E. amylovora population dynamics in cankers and provide clues on the effect of management practices, host cultivar, host water/nutritional status, etc., on bacterial survival. Show less

With the challenges that negatively impact tree-based agriculture, landscapes and forests, such as climate change, plant pathogen and insect range expansion, invasive species and limited new pesticides, it is important to introduce new and effective tree protection options. In the last 20 years, pathogens that invade wood i.e. vascular tissues of trees causing wilt, yellowing, premature defoliation, cankers and tree death, have been on the rise. Diplodia corticola causes Bot canker of oak… Show more

With the challenges that negatively impact tree-based agriculture, landscapes and forests, such as climate change, plant pathogen and insect range expansion, invasive species and limited new pesticides, it is important to introduce new and effective tree protection options. In the last 20 years, pathogens that invade wood i.e. vascular tissues of trees causing wilt, yellowing, premature defoliation, cankers and tree death, have been on the rise. Diplodia corticola causes Bot canker of oak species which can kill trees diminishing the valuable ecological services they provide and reducing profits from wood and cork production. Since this and similar pathogens have difficult biologies because they reside in wood and cause severe internal damage and tree death, their management is difficult or inefficient with classical pesticide application methods that cannot reach and distribute the active ingredient in vascular wood tissues. As practical management options for this and other vascular tissue pathogens of trees are limited, we evaluated efficacy of several trunk injected fungicides in control of D. corticola and compared it with the efficacy of trunk injection of similar compounds for control of Venturia inaequalis and Erwinia amylovora, as two well-studied apple tree pathogens with different or partially similar lifestyles to D. corticola, respectively. Show less

Coast redwood (Sequoia sempervirens) is among the most widely planted landscape trees in California (CA) but is in decline outside its natural range due to factors including prolonged drought and plant pathogens. We investigated associations of Botryosphaeriaceae fungi with declining coast redwood trees throughout CA. More than 100 samples were collected from 11 coastal and inland locations in CA. Fifty-nine Botryosphaeria-like fungal strains were isolated and 18 were selected for further… Show more

Coast redwood (Sequoia sempervirens) is among the most widely planted landscape trees in California (CA) but is in decline outside its natural range due to factors including prolonged drought and plant pathogens. We investigated associations of Botryosphaeriaceae fungi with declining coast redwood trees throughout CA. More than 100 samples were collected from 11 coastal and inland locations in CA. Fifty-nine Botryosphaeria-like fungal strains were isolated and 18 were selected for further study. Phylogenetic analysis of ITS and EF-1α sequence data confirmed the presence of Botryosphaeria dothidea, Neofusicoccum australe, N. luteum, N. mediterraneum and N. parvum. Pathogenicity testing showed that although the Neofusicoccum species vary in virulence, all are more virulent that B. dothidea. Neofusicoccum australe caused the largest lesions, followed by N. luteum, N. parvum, and N. mediterraneum. Of the species recovered, only B. dothidea has been previously confirmed as a pathogen of coast redwood in CA. These results confirm that multiple Botryosphaeriaceae species are associated with branch decline and dieback on coast redwood in CA, which agrees with similar studies on woody agricultural crops. Accurate diagnosis of fungal pathogens of coast redwood is important for the development of disease management strategies and may help improve horticultural practices in maintenance of urban stands. Show less

DOI: 10.1094/PDIS-01-18-0184-PDN

DOI: 10.1094/PDIS-08-16-1181-PDN

Excessive tree wounding is a common concern regarding the use of trunk injection technology for tree protection purposes in landscapes and urban greening. We investigated the rate of healing of injection ports (points) in apple trees by monitoring parameters such as port diameters, the size of bark cracking, and port depths. We compared drilled injection ports from 4.4 and 9.5 mm drill bits, with latter being sealed with plastic-silicone plug (Arborplug®) or not, and the lenticular port from a… Show more

Excessive tree wounding is a common concern regarding the use of trunk injection technology for tree protection purposes in landscapes and urban greening. We investigated the rate of healing of injection ports (points) in apple trees by monitoring parameters such as port diameters, the size of bark cracking, and port depths. We compared drilled injection ports from 4.4 and 9.5 mm drill bits, with latter being sealed with plastic-silicone plug (Arborplug®) or not, and the lenticular port from a double-edged blade. Depending on port size and type, port closure ranged from one to more than two years. Bark cracking around injection ports was more pronounced longitudinally. On the sealed 9.5 mm port, bark cracking was largely similar to all drilled ports. The depth of port wounds decreased faster on the port from the 4.4 mm drill bit and on lenticular injection port versus the unsealed port from the 9.5 mm drill bit. Plastic-silicone plugs, which simulate removed bark, slowed the healing of 9.5 mm drill port with callus and increased the port depths over time due to callus formation over the top of the plug. From fastest-healing to slowest-healing, on average the injection ports were: lenticular port from blade (70.8%), the unsealed 9.5 mm drill port (44.4%), 4.4 mm drill port (43.9%), and 9.5 mm drill port sealed with plastic-silicone plug (20.4%). Show less

Bark beetles carry a number of associated organisms that are transferred to the host tree upon attack that are thought to play a role in tree decline. To assess the pathogenicity to western white pine (WWP; Pinus monticola) of fungi carried by the mountain pine beetle (MPB; Dendroctonus ponderosae), and to evaluate the potential for systemic prophylactic treatments for reducing fungal impacts, experiments were conducted with WWP seedlings to meet three objectives: 1) evaluate pathogenicity of… Show more

Bark beetles carry a number of associated organisms that are transferred to the host tree upon attack that are thought to play a role in tree decline. To assess the pathogenicity to western white pine (WWP; Pinus monticola) of fungi carried by the mountain pine beetle (MPB; Dendroctonus ponderosae), and to evaluate the potential for systemic prophylactic treatments for reducing fungal impacts, experiments were conducted with WWP seedlings to meet three objectives: 1) evaluate pathogenicity of two MPB-associated blue-stain fungi; 2) evaluate phytotoxicity of tree injection products; 3) evaluate the anti-fungal activity of tree injection products, in vitro and in vivo, toward the associated blue-staining fungi. To evaluate pathogenicity, seedlings were inoculated with Grosmannia clavigera or Leptographium longiclavatum, common fungal associates of MPB. Seedling mortality at four months after inoculation was 50% with L. longiclavatum and 90% with G. clavigera, both significantly higher than controls and thereby demonstrating pathogenicity. Phytotoxic effects of TREE-äge®, Alamo®, and Arbotect® were evaluated by stem injection; no phytotoxic effects were observed. Anti-fungal properties of the same three products were evaluated in vitro against G. clavigera, where Alamo was most active. Co-inoculation of G. clavigera and L. longiclavatum into seedlings after a stem injection of Alamo showed significantly less mortality and lesion formation than either species alone. Results support the hypothesis that MPB blue-stain associates, particularly G. clavigera, promote death of WWP when attacked by MPB. These findings suggest that the administration of a fungicide with insecticide for tree protection against bark beetles may be advantageous. Show less

To optimize the number and timing of trunk injections for season-long control of apple scab (Venturia inaequalis), we evaluated 1-2 and 4 seasonal and cross-seasonal injections of potassium phosphites and synthetic fungicides and quantified residues in leaves and fruit. Phosphites accumulated in the canopy at the highest concentrations, aligned well in time with scab suppression, and gave better leaf scab control of 41.8-73.5% than propiconazole (16.9-51.5%) or difenoconazole + cyprodinil… Show more

To optimize the number and timing of trunk injections for season-long control of apple scab (Venturia inaequalis), we evaluated 1-2 and 4 seasonal and cross-seasonal injections of potassium phosphites and synthetic fungicides and quantified residues in leaves and fruit. Phosphites accumulated in the canopy at the highest concentrations, aligned well in time with scab suppression, and gave better leaf scab control of 41.8-73.5% than propiconazole (16.9-51.5%) or difenoconazole + cyprodinil (5.4-17.4%). More injections of phosphites controlled leaf scab better than fewer (23.7% vs. 48.2%), and more fungicide injections resulted in 21.9-51.1% better leaf scab control than fewer. Leaf scab control with phosphites was 3.2-13.9% better with 4 cross-seasonal compared to 4 seasonal injections, while 1-2 seasonal compared to 1-2 cross-seasonal injections improved scab control for 4.2-22.1%. On shoots, injected phosphites provided comparable or for 4.4-10.5% and 22.3-41.4% better scab control than spray standards. On fruit, injected phosphites slightly improved control compared to sprayed phosphites or the sprayed fungicide standard (33.4-40.8%). Two seasonal injections of phosphites controlled shoot scab 5.7% better than 9 spray applications. Five sprays of difenoconazole + cyprodinil controlled scab better than their injections. Fruit residues of phosphites reached 2.8 ppm and declined in all treatments except in 2 seasonal injections and phosphite sprays. Cyprodinil and difenoconazole fruit residues reached 0.02 and 0.07 ppm and declined sharply towards the end of the season. These were far below the USA, Codex, and EU MRL-s of 1, 0.8 and 0.5 ppm for difenoconazole, and 1.7, 2 and 1 ppm for cyprodinil, respectively. Show less

Trunk injection is a novel delivery method for plant protective compounds in agriculture. It could increase sustainability of fruit production through target-precise disease control. We evaluated trunk-injected antibiotics, copper chelate (CC), and prohexadione-calcium (PC) in control of fire blight on apples. After 1-2 spring injections of oxytetracycline (OX), kasugamycin (KS) and CC, we evaluated inoculated apple trees for blossom and shoot blight incidence. In a separate study, after… Show more

Trunk injection is a novel delivery method for plant protective compounds in agriculture. It could increase sustainability of fruit production through target-precise disease control. We evaluated trunk-injected antibiotics, copper chelate (CC), and prohexadione-calcium (PC) in control of fire blight on apples. After 1-2 spring injections of oxytetracycline (OX), kasugamycin (KS) and CC, we evaluated inoculated apple trees for blossom and shoot blight incidence. In a separate study, after spraying or injection of PC, we evaluated shoot blight severity after inoculation. At a high disease pressure, OX, KS and CC provided blossom blight control of 60.6, 31.7 and 15.5-17.8%, respectively. The same compounds provided control of shoot blight incidence of 60.7, 42 and 24.5-33.9%, respectively. The results indicate that shoots initially accumulate more of the injected compound than flowers, due to their higher transpiration driven by larger green tissue area. Sprayed PC reduced shoot blight severity for 25.6% and caused expected reduction of shoot length, while trunk-injected PC failed to cause any of these effects. This indicates that PC did not translocate into the canopy due to its strong binding in the xylem. With the development and use of injectable formulations, proper dosing, and optimal injection timing, delivered compounds could have more time for accumulation in the canopy and thus provide better fire blight control. Hence, trunk injection could become an effective option for fire blight control on apple trees. Show less

DOI: 10.1094/PDIS-09-15-0994-PDN

http://daten.conventus.de/ippc2015/ippc2015_ID_0459.jpg

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected… Show more

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. In field experiments, after 1–2 apple tree injections of either streptomycin, potassium phosphites (PH), or acibenzolar-S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2, and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy. ASM and PH suppressed fire blight even after cessation of induced gene expression. With the development of injectable formulations and optimization of doses and injection schedules, the injection of protective compounds could serve as an effective option for fire blight control. Show less

DOI: 10.1016/j.cropro.2014.05.017

Dissertation in Plant Pathology

DOI: 10.4172/2161-0983.1000126
Trunk injection technology represents an alternative delivery system to provide crop protection for horticultural crops of commercial and smallholder farmers in the developed and developing world. Field studies, laboratory bioassays, and residue profile analysis were used to determine the seasonal effectiveness of trunk injected insecticides against key apple insect pests. Insecticides formulated for trunk injection, imidacloprid, rynaxypyr, and emamectin… Show more

DOI: 10.4172/2161-0983.1000126
Trunk injection technology represents an alternative delivery system to provide crop protection for horticultural crops of commercial and smallholder farmers in the developed and developing world. Field studies, laboratory bioassays, and residue profile analysis were used to determine the seasonal effectiveness of trunk injected insecticides against key apple insect pests. Insecticides formulated for trunk injection, imidacloprid, rynaxypyr, and emamectin benzoate were injected into semi dwarf Empire apple trees and evaluated for a wide range of insect pests. Imidacloprid controlled piercing and sucking pests, and emamectin benzoate controlled leaf rollers, Oriental fruit moth, and leafhoppers. The residue profiles for insecticides showed that vascular delivery was predominantly to foliage, with fruit residues far below the EPA maximum residue limits These results suggest that trunk injection is a promising delivering system for plant protection materials for control of foliar pests, while minimizing impacts on natural enemies, eliminating spray drift, and reducing the pesticide load in the agro-ecosystem. For smallholder farmers this low-capital investment technology has the potential to significantly reduce the human health risks associated with pesticide use, while protecting high value horticultural crops from pests. Show less

DOI: 10.4454/JPP.V96I1.035

DOI: 10.1002/ps.3747

Trunk injection of Systemic Acquired Resistance (SAR) inducers as an in planta delivery approach could enhance their effect in fire blight control. PR-protein gene expression indicating SAR should be achieved after injection of SAR inducers on mature apple trees. After 1-2 injections of acibenzolar-S-methyl (ASM; Actigard) or two injections of potassium phosphites (PJ; Phosphojet), using 4 replicates per treatment, inoculated Gala trees were evaluated for blossom and shoot blight and for… Show more

Trunk injection of Systemic Acquired Resistance (SAR) inducers as an in planta delivery approach could enhance their effect in fire blight control. PR-protein gene expression indicating SAR should be achieved after injection of SAR inducers on mature apple trees. After 1-2 injections of acibenzolar-S-methyl (ASM; Actigard) or two injections of potassium phosphites (PJ; Phosphojet), using 4 replicates per treatment, inoculated Gala trees were evaluated for blossom and shoot blight and for PR-protein gene expression in leaves and flowers. In year 1, ASM and PJ significantly reduced blossom blight incidence by 37.7-42.2% and 55.9%, respectively. Shoot blight incidence was reduced 70.8% by PJ only. In year 2, ASM and PJ reduced blossom blight by 19.1-21.1% and 25.1%, respectively, and shoot blight by 27-31% and 23.4%, respectively. In year 2, PJ significantly upregulated expression of the PR-1, PR-2 and PR-8 protein genes. ASM upregulated these genes in leaves consistently, in both years. Thus, injected PJ and ASM induce SAR in leaves on mature apple trees but at different times and with different persistence of the effect. SAR activity was not detected in flowers, probably due to reduced accumulation of injected compounds in them, which was driven by their lower transpiration compared to the leaves. With proper dosing and more time for translocation and accumulation in the canopy, trunk-injected SAR inducers could serve as an effective option for fire blight control. Show less

Trunk injection of protective compounds is a target-precise pest control approach which could eliminate negative drift-driven effects of pesticides on the environment. Significant control of leaf apple scab (Venturia inaequalis) should be achieved through trunk injection of systemic biopesticides and fungicides. After 4 injections of 5 biopesticides and 1 fungicide, and a single injection of 1 fungicide, using 4-6 replicates per treatment, naturally infected Red Delicious and Mac Spur apple… Show more

Trunk injection of protective compounds is a target-precise pest control approach which could eliminate negative drift-driven effects of pesticides on the environment. Significant control of leaf apple scab (Venturia inaequalis) should be achieved through trunk injection of systemic biopesticides and fungicides. After 4 injections of 5 biopesticides and 1 fungicide, and a single injection of 1 fungicide, using 4-6 replicates per treatment, naturally infected Red Delicious and Mac Spur apple trees were rated for leaf scab. Spur and shoot scab incidences for water injected controls, propiconazole (Alamo), and spray standards, were 72.2-81.9% and 50.9-54%, 52.5% and 22.5-26.2%, and 15.5-16.7% and 20-20.6%, respectively. After 4 injections, potassium salts of phosphorous acid (PhosphoJet) showed significant reduction of spur and shoot scab with incidences of 39.3-47.7% and 14.3-18.5%, while potassium phosphite, potassium dihydrogen phosphate, potassium bicarbonate and hydrogen peroxide (OxiDate) showed overall reduced spur and shoot scab of 53.5 and 18.4%, 60.4 and 28.1%, 72.4 and 36.5%, and 61.1 and 29.1%, respectively. After a single injection of difenoconazole + cyprodinil (Inspire Super) significant control of spur and shoot scab of 25.9 and 21.2% was achieved. However, spray standard and sprayed Inspire Super were better with spur and shoot scab of 13.9 and 16.6%, and 0.07 and 3.2%. Based on the results, trunk injection could be used for apple disease control. Show less

Trunk injection is a valuable alternative for delivering protective materials which could increase sustainability of tree agriculture by target-precise pest control with no negative effects of pesticides on the environment. Due to a systemic mode of exposure, a significant control of fire blight (Erwinia amylovora) should be achieved through trunk injection of Systemic Acquired Resistance (SAR) inducers. After 1-2 injections of 4 candidate and known resistance inducers and 2 antibiotics, using… Show more

Trunk injection is a valuable alternative for delivering protective materials which could increase sustainability of tree agriculture by target-precise pest control with no negative effects of pesticides on the environment. Due to a systemic mode of exposure, a significant control of fire blight (Erwinia amylovora) should be achieved through trunk injection of Systemic Acquired Resistance (SAR) inducers. After 1-2 injections of 4 candidate and known resistance inducers and 2 antibiotics, using 4 replicates per treatment, inoculated Gala apple trees were rated for blossom and shoot blight, and Kit Jonathan trees for shoot blight. Similarly to streptomycin with blossom and shoot blight incidences of 17.1 and 4%, candidate inducer potassium salts of phosphorous acid (PhosphoJet) provided significant fire blight control with incidences of 20.4 and 6.5% compared to water injected control (46.1 and 22.3%). Imidacloprid (Imajet) was ineffective with incidences of 40.1 and 18.3%. Two doses of SAR inducer acibenzolar-S-methyl with incidences of 26.9 and 20.3%, and 27.7 and 18.5%, significantly reduced only blossom blight. Inducer prohexadione-calcium did not control shoot blight implying no translocation of the active ingredient. Oxytetracycline (ArborBiotic) significantly controlled shoot blight on Kit Jonathan with time severities of 4.7-14.2% compared to water injected control (30.1-68.6%). The results show that trunk injection could be used for apple disease control. Show less

Novel research on using trunk injection of plant medicines for control of apple diseases and pests.

In the period 2007-09 in two localities in Vojvodina (B. Petrovac and R. Šančevi) carried out a review of marigold plants in order to study the health status and determining the causes of disease, to take proper protective measures. During the 2007 on R. Šančevi, at 4 marigold cultivars was studied appearance of powdery mildew. The first symptoms were observed in early July, and rating the infection intensity was performed 19. 07. 2007. Domestic variety Bački Petrovac was the least sensitive -… Show more

In the period 2007-09 in two localities in Vojvodina (B. Petrovac and R. Šančevi) carried out a review of marigold plants in order to study the health status and determining the causes of disease, to take proper protective measures. During the 2007 on R. Šančevi, at 4 marigold cultivars was studied appearance of powdery mildew. The first symptoms were observed in early July, and rating the infection intensity was performed 19. 07. 2007. Domestic variety Bački Petrovac was the least sensitive - infection intensity ranged from 0,1-0,3%, and at the most susceptible variety Plamen plus was 1,9-2,3%. During the 2008 at the site B. Petrovac in the second part of vegetation period observed appearance of wilting and drying of plants. By isolation from the roots and the ground part of stalk was obtained colonies of fungus belonging to the genus Fusarium. In the 2009 on the plants was noticed brown freckles of different sizes, with the note and the concentric circles, mainly on lower leaves. Leaves gradually get necrosis, drying and split up. From diseased leaves was isolated Alternaria sp. In the middle of July, on the plants started to spread intensely powdery, and in mid-August more than 50% leaves was affected by a compact white cover, which is followed by drying plants. Microscopic examination determined the presence of oidiums and cleistotheciums probably of Podosphaera xanthii species. Show less

DOI:10.2298/PIF1004335B
URL 2: http://scindeks.ceon.rs/article.aspx?artid=1820-39491004335B&redirect=ft&lang=en

During the period of 2007-2009, on the territory of Južna Bačka Region (localities Bački Petrovac and Rimski Šančevi), in the trial plots of Institute of Field and Vegetable crops, Novi Sad, survey of medicinal plants was conducted. The aim was to examine health condition of plants, determine the causing agents of diseases and choose appropriate measures of protection. On the basis of periodical surveys of health condition, during past few years, it can be concluded that the most severe disease… Show more

During the period of 2007-2009, on the territory of Južna Bačka Region (localities Bački Petrovac and Rimski Šančevi), in the trial plots of Institute of Field and Vegetable crops, Novi Sad, survey of medicinal plants was conducted. The aim was to examine health condition of plants, determine the causing agents of diseases and choose appropriate measures of protection. On the basis of periodical surveys of health condition, during past few years, it can be concluded that the most severe disease intensity was recorded with powdery mildew of Pot Marigold (Podosphaera xanthii). The stem spotting on the Marshmallow was also present. During 2009, severe intensity of rust (Puccinia absinthii) was detected on wormwood, Alternaria sp. i Fusarium sp. on Pot Marigold and Phomopsis sp. on Fennel Show less

MSc thesis in Phytopathology

Review of scientific papers from XXIV Seminar of Plant Protection in Vojvodina. Year XXXVII, Special issue.

Soybean is highly important and widely spread farming and industrial crop. Soybean acreage is constantly expanding. Along with acreage expansion many soybean diseases have increased in severity, frequency and intensity. Bacterial diseases of soybean can reduce yield significantly, especially in the years with rainy and cool spring and with rainy summer too. In Serbia the causal agent of Bacterial Blight of soybean - Pseudomonas syringae pv. glycinea has the highest significance. It appears… Show more

Soybean is highly important and widely spread farming and industrial crop. Soybean acreage is constantly expanding. Along with acreage expansion many soybean diseases have increased in severity, frequency and intensity. Bacterial diseases of soybean can reduce yield significantly, especially in the years with rainy and cool spring and with rainy summer too. In Serbia the causal agent of Bacterial Blight of soybean - Pseudomonas syringae pv. glycinea has the highest significance. It appears regularly, and in the years with favorable conditions for development and spreading it causes severe damages. Second species Xanthomonas campestrisi pv. glycines, causal agent of Bacterial Pustule of soybean, has been detectet in Serbia but in comparison with P. s. pv. glycinea it has a slightly less economical importance. In favourable conditions this pathogen can reduce yield in some measure. Pseudomonas syringae pv. tabaci, as causal agent of Wildfire of soybean, has not been detected in Serbia but it appears regularly on tobacco as primary host. For all three species of phytopathogenic bacteria detailed survey about: world spread and economical importance, specific symptoms, bacteriological and epidemiological/ecological characteristics, cultivar resistance and recommendations for control has been presented. Show less

BSc Thesis in Plant Protection (now Phytomedicine)