Incidence of the Mango Mealybug Rastrococcus invadens Williams on Different Mango Varieties in two Local Government Areas in Benue State, Nigeria
Ukwela M.U.
Department of Crop Protection, University of Agriculture, P.M.B 2373 Makurdi, Benue State, Nigeria.
Email: muukwela@yahoo.com
Accepted on September 10, 2007
Abstract
Survey of five human settlements in Gboko and Buruku Local Government Areas, Benue State, showed the presence of eight mango varieties; Local, Julie, Gesha, John, Dabsha, Pittir, Germer and Hindi. Ten leaves per stand of each mango variety were sampled every month for 24 months. Numbers of different stages of mango mealybug, Rastrococcus invadens Williams and mummies were monitored. R. invadens field population per cm2 leaf area varied significantly among eight varieties of mango. While Gesha, Julie and Local varieties favoured significant field population growth of R. invadens John, Dabsha and Germer contributed significantly less. Population of R. invadens on Gesha, Julie and Local followed the same trends and peaked in May, 2000. Population of the mealybug declined sharply along with its parasitoid Gyranusoidea tebygi Noyes on each variety during October, 2000 due to combined forces of wind and rainfall. Contribution to changes in R. invadens population by both biotic and abiotic factors were significantly higher (P<0.05) on Gesha (r2 = 60.8%) and Pittir (r2 = 59.7%). G.tebygi, though low in number, is well established on its host R.invadens in the zone of study. Mango varieties had significant (P<0.05) influence on the sex ratio of the mealybug with the male population higher than the female in each variety.