Effect of neem azal and neemol on survival, longevity, and development of cocoa shield bug, Bathycoelia thalassina (H.-S) (Heteroptera: Pentatomidae), attacking cocoa in Ghana

Abstract

The study assessed the biological activity of neem azal and neemol against nymphs and adults of the shield bug, Bathycoelia thalassina, in the laboratory at the Cocoa Research Institute of Ghana. Toxicity of the neem products and their effect on moulting, nymphal survival, development time, adult longevity, and oviposition of the bug were determined at 2.0, 2.5, 3.0, 4.0, 5.0, 7.0 and 10.0 per cent v/v concentration. At 10 per cent v/v concentration, neem azal and neemol shortened the longevity of adult B. thalassina to 34 and 49 days, respectively. Neem azal delayed oviposition of the bug until after 26 days, but neemol did not have this effect. Egg laying was generally reduced by both neem products to as low as 12 eggs per female at 10 per cent v/v. Furthermore, neem azal and neemol extended the incubation period of the eggs by 4 days, and reduced percent egg hatchability by 30 and 17 per cent, respectively, compared to the control. Eggs that did not hatch gradually shrivelled and turned black. The neem products disrupted moulting, and nymphs emerging from neem-treated cocoa pods had flexed wings. Development time was prolonged and adult emergence was reduced. All insects exposed to 10 per cent v/v neem azal died after an extended period in the third and fourth instar stages. This study shows that neem azal and neemol can be used to effectively disrupt growth processes in B. thalassina, and may have great potential as a component of integrated management of the pest in cocoa production.

Ghana Journal of Agricultural Science Vol. 38, 2005: 3-12