Influence of insect infestation on aflatoxin contamination of stored maizein four agroecological regions in Benin

Insect species and damage levels were evaluated and related to aflatoxin co ntent in maize sampled from farmers' stores in four agroecological zones ov er a two-year period in Benin, West-Africa. In 1993, no aflatoxin was detec ted in maize that was free of insect damage. In the same year, in maize wit h more than 70 % of cobs damaged by insects 30.3 % were aflatoxin-positive, with a mean aflatoxin contamination of 77.8 ppb (parts per billion or mug/ kg). Grain moisture increased with damage levels. The mean aflatoxin conten t of maize infested with Carpophilus dimidiatus Fabricius (Coleoptera: Niti dulidae) was significantly higher than maize free of this pest (F = 5.05, P less than or equal to 0.05). In 1994/95, the density of Mussidia nigrivine lla Ragonot (Lepidoptera: Pyralidae), was significantly higher in the North ern Guinea Savanna than in the other zones, and the presence of this pest w as positively correlated with the cob area visibly infected with Aspergillu s flavus Link (Deutoremycetes: Monoliales) (r = 0.239, P less than or equal to 0.05) early in storage. Six months later, damage levels due to insects were significantly lower in the Sudan Savanna than in the other ecozones. T he infestation level of the most common storage pest, Sitophilus zeamais Mo tschulsky (Coleoptera: Curcilionidae) decreased from the south to the north . After six months of storage aflatoxin level was positively correlated wit h the cob area damaged by Sesamia calamistis Hampson (Lepidoptera: Noctuida e) (r = 0.25, P less than or equal to 0.05), the number of Cryptophlebia le ucotreta (Meyrick) (Lepidoptera: Tortricidae) observed on maize (r = 0.26, P less than or equal to 0.05) and cob area damaged by S. zeamais (r = 0.22, P less than or equal to 0.05).