Conditions Favoring
Aflatoxin Development

          The causal fungi Aspergillus flavus and A. parasiticus are very common and widespread in nature. These fungi can infect corn kernels through invasion of the corn silks or in association with insect damaged kernels. The spores of the fungus are not able to germinate and grow on green silks but thrive on silks in the yellowish-brown stage and use them to grow down to the kernel . Brown silks can serve as a food source for A. flavus but do not serve as a channel for the fungus to reach the kernels. Broken kernels and those with cracked pericarps (seed coats) are more prone to A. flavus infection.

 
          Periods of drought and heat stress, especially during pollination and kernel maturation, predispose the plants to increased A. flavus infection and aflatoxin production in the field. Corn damaged by insects or weather factors may also be predisposed to increased infection. In grain, the fungus seems to grows best at about 17 to 20 % grain moisture. Research data vary considerably as to the upper limit of grain moisture for A. flavus growth and aflatoxin development, ranging from approximately 30 to 50%. When grain moisture is below 13%, fungal growth and aflatoxin production virtually stops. A. flavus grows best at high temperatures from 80 F to 100 F, given favorable moisture.




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