Abstract

Among the numerous insect pests infesting cashew in Nigeria, the cashew trunk and root borer, Plocaederus ferrugineus L. (Coleoptera: Cerambycidae) is fast becoming the most dreaded because its infestation results in the sudden death of the tree within weeks. Observations at Ochaja in 1999/2000 and at Ibadan in 2005 of “sudden death” of mature cashew trees within few weeks of infestation were indications of emergence of new pest of cashew in Nigeria, which needs urgent investigation. Frass and gum exudates were collected from the trunk base of dead plants before they were cut down and exhumed carefully from the soil. Soil samples were collected from beneath the excavated roots. The bored holes on the trunk and roots were excised to ex-pose their frass and gum contents. Both the frass and gum exudates collected from the base of the cashew trunk and those from excised trunk and roots together with the soil samples from beneath the excavated roots were thinly spread out in the laboratory to search for the various life stages of the beetles. Brief description of the beetle’s life stages and parts of the infested/dead stands were made. The rate of infestation of cashew trees at Ibadan was 18.13%, resulting in a death rate of 1.88% of trees, while the infestation rate at Ochaja was 13.3% with a death rate of 6.38%. The eggs were conspicuously absent at the time of this assessment as they had all emerged and developed into larvae, pupae and adults. The control of the pest at advanced stage of the larval development was very difficult; hence control measures were recommended to be initiated at early stage of infestation. Strict cultural practices gave desired results.

Key words: Infestation, beetles, borer, frass, exudates, larvae, pupae, adults.