Effect of Host Plant of Aphididae, Plant Structure and Aphid Alarm Pheromone on Oviposition by Ladybirds

Abstract

In the class Insecta, the chemistry of the oviposition site is crucial element for offspring survival. Thereby, females tend to choose specific sites on the specific host plants that offer better nutrition and support for larval development. Alarm pheromones, released in response to predation, serve as chemical cues influencing predator behaviour. The present study investigates the effects of aphidhost plant associations, plant architecture, and aphid alarm pheromone on oviposition behaviour in four ladybird species, viz. Coccinella septempunctata, Coccinella transversalis, Menochilus sexmaculatus and Propylea dissecta. The effect of these associations were found to be species-specific.
Females laid the highest number of eggs on Aphis gossypii- Lagenaria vulgaris and Aphis craccivora-Dolichos lablab aphid-plant complexes. Lowest oviposition was reported on A. gossypii-Solanum melongena and A. craccivora-Vigna unguiculata complexes. Among plant structures, maximum oviposition was observed on bean pods and young leaves, whereas old leaves were the least preferred oviposition site. The presence of alarm pheromone from Acyrthosiphon pisum significantly enhanced oviposition in all four ladybird species. These findings highlight the importance of tri-trophic interactions in shaping oviposition decisions and suggest potential strategies for enhancing biological control through habitat manipulation.