Fumonisin contamination of maize hybrids visibly damaged by Sesamia

Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae), is the major insect pest of maize cultivated in the Mediterranean areas, causing increase of broken plants, yield reduction and decline of grain quality. An investigation of Sesamia attacks and fumonisin accumulation on 25 maize hybrids sown as a second crop after wheat has been performed under field conditions in Central Italy, in 2000. The hybrids tested in this study showed a different degree of insect damage, ranging from 12% to 57% damaged ears per hybrid. Over 50% of the tested hybrids showed a strong insect damage with more than 30% of harvested ears visibly damaged by Sesamia. Fungal contamination by Fusarium verticillioides and F. proliferatum, two well-known producers of fumonisins, was detected in both symptomless or insect damaged samples. Fumonisin analysis of healthy looking and insect damaged ear samples of each hybrid showed 100% incidence of positive samples, with fumonisin contents ranging from 0.01 mg kg-1 to 20 mg kg-1 for healthy looking ears and from 27 ± 32 mg kg-1 to 287 ± 221 mg kg-1 for insect damaged ears. Extremely high levels of fumonisins were found in ear samples visibly damaged by Sesamia with individual values up to 694 mg kg-1, and average values exceeding 100 mg kg-1 in more than 50% of the hybrids. A good correlation (r = 0.749) was found between fumonisin contamination and the degree of insect damage by Sesamia of the tested hybrids, calculated on the basis of percent of ears visibly damaged by insects and with more than 5% kernel loss. This finding leads to the conclusion that insect damage by Sesamia on maize could be used as an early indicator of fumonisin contamination.