Role of the insect vector, Pseudotheraptus devastans, in cassava anthracnose disease development

The aim of this study was to investigate the role of Pseudotheraptus devast ans in cassava anthracnose disease transmission and development. P. devasta ns, Dist (Het. Coriedae) insects were collected from cassava (Manihot escul enta Crantz) field plots at the International Institute of Tropical Agricul ture, Ibadan, Nigeria and reared in large cages. The insects were separated at different developmental growth stages of eggs, first to fifth instar ny mph, and adults. The different stages of P. devastans showed the presence o f Colletotrichum gloeosporioides both externally and internally. Isolates o f C. gloeosporioides derived from the insects produced cassava anthracnose disease symptoms (necrotic lesions, wilt and defoliation) 8 weeks after ino culation on two cassava clones. Re-infectivity of cassava plants by the ins ect-derived fungus established that P. devastans was a potential vector in anthracnose transmission. Except for the first and second instar nymphs, al l nymph stages and adult insects produced significant anthracnose symptoms on cassava plants. Defoliation and lesion diameters were greatest using fif th instar nymphs and adult insects. The association between P. devastans fe eding and C. gloeosporioides f.sp. manihotis, showed that feeding by P. dev astans followed by fungal inoculation and vice versa resulted in more sever e anthracnose symptoms than insect feeding or fungal inoculation alone. It was also observed that the influence of P. devastans damage/infection on th e development of anthracnose depended on cassava cultivar resistance to bot h the fungus and the insect feeding.