ABSTRACT

As part of efforts to cope with the destructive challenge posed by the cassava mealybug, Phenacoccus manihoti Matfie Ferrero (Horn., Pseudococcidae), field studies were conducted on P. man/hoti during the dry and wet seasons of 2004 to 2005 in parts of Mbaitoli L.G.A, Imo Stato of Nigeria. Only cassava mono-cropped farms of varying sizes belonging to peasant farmers were studied. The choice of farms was unbiased. Population data on the mealybug were collected during this survey of 100 farms and evaluated in simple bar chart while the rate of farm infestation was evaluated in pie chart. 40% (mean value) of all farms studied were infested, leaving 60% uninfested. Mean cassava mealybug populations were relatively low (about 20 per shoot) compared with peak populations in excess oi 1,500 per shoot in the early 1980s. However, it is concluded that biological control achieved by Epidinocarsis /0pe4 the major control agent of the cassava mealybug (in Nigeria at least) is successful in preventing stunting of cassava plants in most fields, though bugs persisted and still caused certain degree of economic damage. Findings from this study have successfully established the factors that affect the distribution/spread of cassava mealybugs. These factors are (1) colonization/distribution of natural enemies of the mealybugs (ii) soil moisture content/sources (iii) agronomic factors (iv) location/site of farms (v) level of insecticide usage and (vi) cassava planting spacing adopted. Moreover, to keep the cassava mealybugs under check, regular release of the proven natural enemy coupled with cultural practices of say mulching and use of resistant cultivars are recommended. In addition, these resistant cultivärs should not only be used but also should be distributed in sufficient number all over cassava growing areas by concerned groups. These and other biological findings have provided further interest in the cassava mealybug, P/enacoccus manihoti.