Effect of Insect Damage to Maize Ears, with Special Reference to Mussidia nigrivenella (Lepidoptera: Pyralidae), on Aspergillus flavus (Deuteromycetes: Monoliales) Infection and Aflatoxin Production in Maize Before Harvest in the Republic of Benin

Abstract

Maize infection by Aspergillus flavus Link and subsequent aflatoxin contamination as affected by insect damage to maize ears before harvest was studied with surveys in farmers' fields and in a field trial in the Republic of Benin, West Africa. The most important pest species was the lepidopteran earborer Mussidia nigrivenella Ragonot. Percentage of grain infected by A. flavus and of samples contaminated with aflatoxin, as well as the mean aflatoxin content of samples, increased with increasing borer damage. Ears with 10% damage) had an average aflatoxin of 514.6 and 388.2 ppb in 1994 and 1995, respectively. In 1994 only, coleopteran species such as Sitophilus zeamais Motschulsky and Carpophilus sp. significantly increased levels of aflatoxin in grain samples. In a field trial using M. nigrivenella infestation and A. Flavus inoculation treatments, the presence of the insect feeding resulted in increased kernel infection and aflatoxin contamination. Artificial infestation with M. nigrivenella larvae increased aflatoxin content of maize by an average of 45 ppb, whereas inoculation with A. flavus spores increased the toxin level by 517 ppb. The significant interaction between infestation and inoculation indicated that higher levels of aflatoxin B1 were found when the fungus was associated with borers than with the fungus alone. M. nigrivenlla was the major field pest connected with A. flavus infection and subsequent aflatoxin production in preharvest maize in Benin.