Bio-ecological Studies Of Mango Weevil, Sternochetus Mangiferae F. In The Coast Of Kenya (Coleoptera: Curculionidae)

Abstract

Laboratory investigations were carried out on pre-oviposition, oviposition and the life history of mango weevil Sternochetus mangiferae Fab. from egg stage to adult emergency. Effect of feeding on longevity of male and female adult weevils was also studied. The experiments were conducted at 30+1°C and 73 per cent relative humidity Field experiments were conducted to investigate susceptibility of Apple, Ngowe and Boribo cultivars to mango weevil. Distribution of infestation in the three mango cultivars within an individual season, variation of infestation in each cultivar within the five mango seasons and weekly distribution of infestation per cultivar within seasons were considered. The results revealed that S.mangiferae oviposited in an incision on the skin beneath the skin of mango fruit. . Pre-oviposition period was 24.8SE+.085 days and an average of 187~3.75 eggs were laid in 74.6+95- days. The developmental periods for egg, larval and pup~ stages were 5.83+.0127; 23.05+.2 and .6.8+.042' days respectively. Fully

developed larva constructed pupa cell where it pupated. Damage was caused by the weevil puncturing the fruit which resulted in a flow of sap on the surface of the fruit. This provided a media for growth of anthracnose and other fungal agents. The larva fed on the seed destroying it in the process. There was a significant difference between the fed and non-fed weevils. Distribution of infestation by mango weevil in Apple, Ngowe and Boribo within the same season showed no significant difference. Hence infestation was not cultivar specific. Variation of infestation within seasons was significantly different; Seasons one and four had the lowest weevil infestation. There was no difference in infestation within weeks. However, there were fluctuations and conspicuous peaks in the number of weevils within weeks in each cuifivar.