1) Downy mildew is a fungal disease that affects maize crops. Several fungi can cause downy mildew, including Peronosclerospora philippinensis, P. maydis, P. sorghi, P. sacchari, and Sclerophthora rayssiae var. zeae.
2) Symptoms include yellow or brown stripes on leaves, a white fungal growth on the underside of leaves, stunted growth, malformed tassels, and cob formation without grains. Yield losses of up to 63% are reported.
3) The pathogens survive in crop residues and seeds. Spread occurs through seed transmission. Warm, wet conditions favor disease development.
1. COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore-3)
Kullapuram (Po),ViaVaigai Dam, Theni-625 562
Downy mildew of maize
Student Course teacher
S.JAMUNA Dr. S. Parthasarathy
2016021014 Assistant Professor (Plant Pathology)
2. • Number of fungi downy mildews are
• Peronosclerospora philippinensis,
• Peronosclerospora maydis,
• Peronosclerospora sorgi
4. • Peronosclerospora heteropogan is reported
from Rajastan.
• Dangerous species are
P.philippinensis,
P.sacchari,
S.rayssiae var. zeae
P.sorghi
5. • It is mostly occurred in South Asian, South
East Asian and Pacific region.
• In India, the disease is more in Tarai regions of
Himalayas.
6. ECONOMIC LOSS
• Yield loss is caused upto 63% due to this
disease.
• In the states of Karnataka,Tamilnadu,Andhra
Pradesh causing yield losses of 30% and
higher.
9. SYMPTOM
• It appear on leaves as long, broad, yellow,
brown and chlorotic stripes.
• Under surface of the leaf shows wooly white
growth of the mycelium.
• Internodes get shortened and plant becomes
stunted.
10. • Tassels are malformed.
• Cob may not be formed, if formed they are
without grains.
• The infected plants may often die.
• The plants are systematically infected in case of
Philippines downy mildew.
13. Downy mildew of maize caused by P.sacchari ,
the continuous yellowish stripes.
14. Systematic position
Domain Eukaryota
Superphylum Heterokonta
Phylum Oomycota
Order Sclerosporales
Family Sclerosporaceae
Genus Peronosclerospora
Species P. sorghi
Authority (W. Weston & Uppal )
C.G.Shaw,(1978)
15. PATHOGEN CHARACTER
• Conidiophores of P. sacchari emerge through
stomata singly or in groups of 2, rarely 3.
• They are massive and wedge shaped, short,
stout stuctures widening gradually towards
the upper portion.
16. • The conidia are thin walled, hyaline, elliptial,
cylindrical or ovate oblong with rounded apex.
• Oogonia are reddish brown, irregularly
elliptical.
• Oospores on maize leaves are typically round,
thin walled.
17. • Conidia and Oospores germinate by germ tube.
• The germ tubes are hyaline and slender,
aseptate.
• They develop from one or both ends of the
conidium or from its lateral side.
18. • P.philippinensis and P.sachhari are
morphologically identical but differ from each
other in that the former does not produce
Oospores.
• Conidia of this species are mostly barrel
shapped but variable on different hosts.
19. • Sporangiophores of S. rayssiae var. zeae are
quite distinct from Conidiophores of the above
species.
• They are determinate, unbranched and short.
• They arise from hypae congregated in the
substomatal space.
20. • They produce Sporangia sympodially in
groups of 2-6.
• These Sporangia are hyaline, ovate, elliptical,
smooth.
• Germination is by production of 4-8
Zoospores.
22. EPIDEOMOLOGY
• Mode of survive:
The pathogen mostly survives as
oospores present on/in maize seeds or crop
depris .
The fungus may also survive in many
host like S.spontaneum (Kans grass), S.bicolor,
S.halepense and Digitaria sanguinalis.
23. • Mode of spread:
The pathogen spread through seeds.
Seed-borne presence of P.phillipinensis
was mentioned in DM of maize while mycelium
is present in all parts of the seeds,70% embryos
contained oospores and 80% in P.sorghi.
24. FAVOURABLE CONDITIONS
• The optimum temperature for the production
and germination of conidia/sporangia is about
25°C and free water on leaf surface is essential
for formation and germination of
conidia/sporangia.
26. MANAGEMENT
• Resistant maize cultivars,
Hybrids- Ganga5,Ganga9,
Composites, Kisan, Tarun, Naveen,
Sweta, Kanchan.
• Plant maize at least a fortnight before the onset
of rains. Incidence of the disease becomes less
if planting is done during dry season.
27. • Select well drained fields for maize planting or
arrange proper drainage to drain out the excess
rain water.
• The disease can be minimized by spraying the
foliage with fungicides such as metalaxyl or
mancozeb ( 0.3%).
28. • Burn the crop residue after the harvest.
• Practice three year crop rotation to minimize
the initial inoculum load in the field.