Age-related Feeding by the Parthenium Beetle Zygogramma bicolorata on Sunflower and its Effect on Survival and Reproduction

Freshly emerged adults of Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), introduced for biological control trials against the noxious weed Parthenium hysterophorus , were seen to feed and lay eggs on sunflower leaves under confined conditions in the laboratory. The time taken for initiation of feeding was found to be positively correlated with adult age, while survival after feeding on the crop was negatively correlated. However, adults that had fed on sunflower even for 1 day on P. hysterophorus were incapable of ovipositing, and young larvae could not feed on the crop. Under field conditions, newly emerged adults were only attracted to feed on plants that were treated either with a crude aqueous extract of leaves or pollen grains of P. hysterophorus , indicating that the chances of Z. bicolorata becoming a pest of sunflower are negligible. Age-related Feeding by the Parthenium Beetle Zygogramma bicolorata on Sunflower and its EVect on Survival and Reproduction