Decreased reproductive fitness of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoreidae) in response to hexane leaf extract of Ocimum sanctum Linn. (Lamiaceae)

Reproductive fitness of Dysdercus koenigii Fabricius as influenced by the Ocimum sanctum Linn. leaf hexane extract was assessed by observing mating behaviour, fecundity and fertility of the adults developed from the treated fifth instar nymphs. O. sanctum leaf hexane extract affected the mating behaviour of both males and females of D. koenigii. The male exhibited reduced sexual activity which resulted in decreased percent successful mating. There was a decrease in the number of males attempting mounting and the number of mounting attempts; an increase in time taken in order to mate successfully was also reported. The females showed drastic changes in the mating receptivity; in most of the cases, the treated females were non-responsive to the courting males. They often showed mate rejection behaviour which was characterized by shaking of their abdomen and kicking to the courting males with the help of hind legs. Maximum aberration in mating behaviour was seen in the mating pairs, where both the mating partners were treated. Also, the O. sanctum leaf hexane extract impaired oviposition and egg hatchability in a dose-dependent manner. There was a decrease in the number of egg batches and eggs laid by the treated female. Although, the females laid fertile eggs, a significant decrease in the percent egg hatchability was reported in the treated females. The present studies indicated that the O. sanctum leaf hexane extract drastically reduced the reproductive fitness of D. koenigii, and hence potentially may be used in ‘integrated pest management’ of D. koenigii and similar heteropteran insect pests.