Olfactory Stimulants Mediated Egg-Laying Preference of Cowpea and Faba Bean Beetles and the Effectiveness of some Aromatic Plant Products as Protective Agents

The chrysomelid beetles, Callosobruchus maculatus (F.), and Bruchidius incarnatus (Boheman) . females showed different degrees of egg-laying preference on the legume grains. C. maculatus females preferred cowpea over soybean and chickpea. While they significantly desired egg-laying on white bean over horse bean and chickpea. While B. incarnatus females showed the highest preference for laying eggs on soybean, they also preferred horse beans over white beans and chickpeas. The ovipositional preference is odor-mediated, whereas C. maculatus females showed greater attraction to cowpea extracts than to horse bean or chickpea. Regarding B. incarnatus, it exhibited the highest attraction to horse bean extract. The efficiency of the crashed plant leaves (rosemary and marjoram), and clove bud flowers in protecting cowpea and horse bean grains from C. maculatus and B. incarnatus was evaluated after 37 days of storage. The growth rates of C. maculatus reared on cowpea treated with marjoram and rosemary were very slow (0.050, and 0.053) in comparison with control (0.397). On the contrary, the lowest growth rate of B. incarnatus reared on horse beans treated with clove was 0.0478 followed by marjoram (0.052),while the growth rate was high as faster on untreated horse bean seeds (0.154). All botanical treatments significantly decreased the oviposition activities of both beetles. Marjoram, rosemary, and clove treatments significantly reduced cowpea damage by (84.1, 80.57, and 75.69%, respectively) against the attack of C. maculatus. While, bud flower clove proved effective against B. incarnatus, it led to a reduction in the rate of horse bean seed damage (57.46%).