The interaction between host plant resistance & insecticide control of Maruca testulalis Geyer (Lepidoptera: Pyralidae) on Lima-bean

Abstract

The main objectives of this research work were to study the biology and controlling methods of pests of Lima-bean. As the first step in this research, the life cycle of Maruca testulalis (Geyer) was studied. The life span of M. testulalis was about 21 - 25 days at 28 - 30°C and 80.2 - 82% relative humidity. It had five larval instars while life cycle o[ Lampedes boeticus spanned nearly 20 - 24 days. It had five larval in stars as well. The next step was to test the interaction between host plant resistance in different Lima-bean and insecticidal control of Maruca testulalis Geyer (Cowpea pod borer) in laboratory-' conditions. The larvae of M. testulalis feeding on 'Bushita’ showed reduced Relative Growth Rate (R.G.R.) and fecundity compared with larvae feeding on 'Polon-maa' 'Bushita’ and ‘Polon-maa’ were selected as relatively resistant and relatively susceptible varieties, respectively. M. testulalis also showed reduced final body weight and higher first instar larval mortality and may contain higher levels of secondary plant substances on resistant variety (Bushita) than when on susceptible variety (Polon-maa). These characteristics arc known to affect the susceptibility of M. testulalis to insecticides.