The lepidopteran pest complex infesting menthol mint in India: Distribution during the crop development, species composition and associated parasitoids

Menthol mint, Mentha arvensis L. is an important aromatic and medicinal herb cultivated as an industrial crop for its essential oil in the Indo-Gangetic plains of India. The commercial production of menthol mint suffers due to defoliation caused by lepidopteran pests and currently becoming a serious constraint for its clean cultivation. The information on occurrence of lepidopteran caterpillars defoliating menthol mint in the region is limited. In this study, we assessed the occurrence and injury caused by lepidopteran pests from seven major menthol mint growing districts of the Indo-Gangetic plains of India. Further, the species composition of lepidopteran pests and their associated parasitoids were also reported. The survey revealed that seven lepidopteran pest infestations were recorded on different phenological growth stages of menthol mint in the Indo-Gangetic plains of India. The larval population density of lepidopteran pests was significantly different between the districts, species and phenological stages of menthol mint. The larval population density of the lepidopteran pest varied between 0.41 ± 0.31 to 2.37 ± 1.43 larvae/m2 across the locations. The higher occurrence of Spodoptera litura (Fabricius), Spilarctia obliqua Walker and Thysanoplusia orichalcea (Fabricius) was recorded in menthol mint. The higher incidence of lepidopteran pests was recorded at the mid-vegetative growth stage of menthol mint. This study found eight parasitoids parasitizing egg and larval stages of lepidopteran pests. The parasitism rate of egg parasitoids, Trichogramma chilonis Ishii and Trichogramma achaeae Nagaraja and Nagarkatti was 23.53–35.31% and 27.78% to the eggs of Helicoverpa armigera and T. orichalcea, respectively. The larval parasitoids caused a total of 5.78% larval parasitism to the various lepidopteran pests of menthol mints. This information provides a current pest status of lepidopteran pests infesting menthol mint in Indo-Gangetic plains of India. This baseline information could be used for the development of management strategies against lepidopteran pests for sustainable menthol mint production.