Penicillium (penicillium ear rot)

Penicillium rot occurs primarily on ears with mechanical or insect injuries. Seedlings infected by species of Penicillium turn yellow and growth is retarded. Ears show a blue-green powdery growth on and between kernels; this growth also forms on the cob surface, usually near the tip. Seeds may be bleached and streaked. In storage, the fungus fruits below the pericarp in the germ, giving the condition known as blue eye. Blue eye may also be caused during storage by Aspergillus glaucus, which can grow at grain moisture content as low as 14.5% (Payne, 1999). Roots of seedlings may also be infected but symptoms (hyphae within vessels and plasmolysed cells) are not apparent (Johan et al., 1931). If the grain is stored at high moisture levels (greater than 18%), the fungus may invade the grain and discolour the embryo. 

Penicillium ear rot of maize commonly occurs in association with insect damage, such as insect borers which attack the stem, but losses are minor (Koehler, 1960; Jimenez, et al., 1985). Rotting of seeds due to high moisture storage is more important, particularly if the blue eye condition develops. Humidity above 80% after grain fill leads to increased disease severity (CIMMYT, 2004). The fungus was detected in 7% of 1940 samples from grain elevators (silos) in the USA (Sauer et al., 1982). Mycotoxins that can have detrimental effects on animal or human health are produced by species of Penicillium. Of these, only ochratoxin A and B and citreoviridin have been shown to be natural contaminants of grains (Diener, 1976; Chambers, 1987; Adebajo et al., 1994).

Seedling blights of maize caused by species of Penicillium are occasionally severe (Zhukovak, 1957; Mohamed et al., 1968; Satula, 1969). P. oxalicum has been associated with serious stunting and blighting of maize cv. Jubilee seedlings (Halfon Meiri and Solel, 1990a).