Pitan, O.O.R. 2008 Variations in the population of the mango mealybug Rastrococcus invadens (Homoptera: Pseudococcidae), and its parasitism, in relation to smoke pollution.. International Journal of Tropical Insect Science 28(3): 119-125
Notes: A survey was conducted in Ibadan, Nigeria, between 1 November and 30 December 2000 to examine the mango mealybug Rastrococcus invadens Williams infestation. Results obtained prompted another study in which the population of R. invadens and its parasitism were monitored from January 2001 to December 2005 on smoke-polluted infested mango trees after relocation of smoke sources. A third study was conducted between January and April 2007 in Ibadan, Nigeria, where mealybug-infested mango trees were searched for and the levels of pollution around them characterized using a derived rating scale. The survey results showed that only 7.5% of a total of 489 mango trees examined in 2001 were infested with mango mealybug and were located in exhaust, car park, motorway or converging environments. In study 2, the mango mealybug population significantly (P < 0.05) declined, and parasitism significantly increased on trees from where pollution sources were relocated. All the 86 mango mealybug-infested trees scouted for in study 3 were located in smoke-polluted areas. Significantly higher numbers of infested trees and mealybug population, and significantly lower parasitism levels were found on mango trees in exhaust areas, compared with others. Pollution level was correlated with mealybug population (positively) and parasitism (negatively) in 2000 and 2007. Whereas mealybug population gradually built up on hitherto clean trees where pollution sources were relocated, parasitoid activity seemed to be enhanced by the relocation of smoke sources. The effectiveness and conservation of the parasitoids may therefore depend on the air quality around the infested trees.