சுருக்கம்

Field Observations of the Populations, Morphology, Behaviour and Natural Enemies of a Very Important Pest, Cassava Mealy Bug

Luke C Nwosu and Mark C Eluwa

Biological studies on the cassava mealy bug were carried out in mono – cropped cassava fields in Mbaitoli Local Government Area, Imo State, Nigeria during the dry seasons of 2006 and 2007. Population surveys of the mealy bug in the nine towns of the L.G.A. were conducted with the aid of a tally counter while behavioural, morphological and other biological studies of this notorious pest were achieved by thorough observations in the field. Even though 41% of the farms surveyed were infested with the cassava mealy bug, current mean mealy bug populations were relatively high (about 38 bugs per cassava shoot) compared with populations of less than 20 bugs per shoot observed in most fields after the establishment of the biological control programme in the late 1980s. High mealy bug populations recorded in the study stands to pose a serious threat to food availability, at least in the area. The study established Ferrisia virgata and Phenacoccus manihoti as the predominant mealy bug species in the area. The victims of F. virgata were observed to suffer general symptoms of weakening but not conspicuous distorted growth while P. manihoti was found to specialize in the infliction of distorted growth on the cassava host. Investigations in the origin, nature and significance of the mealy bug wax among others, showed that the wax is adaptive in function. Observations on the activities of predators and other enemies encountered amidst bug’s populations and the nature of bug’s interactions with other pests showed that the coccinellid beetles and wingless ants made impact on the mealy bugs and bugs coexisted with the cassava green spider mite. Morphological studies on the different stages of the mealy bug showed differences in size, colour, mobility and shape. The study recommends regular release of the proven natural enemy of the mealy bug (Epidinocarsis lopezi) as a pest management strategy.