Morpho-molecular characterization and bioecology of leaf folder, Pycnarmon cribrata (Fabricius) on nirgundi (Vitex negundo): an aromatic medicinal shrub from India

Abstract

The occurrence of leaf folder, Pycnarmon cribrata (Fabricius, 1794) (Lepidoptera: Crambidae) on the medicinal plant nirgundi, Vitex negundo Linn. has been observed in West Bengal, India. The pest damaged the foliage by folding the leaflets, feeding within and ultimately making the foliage dry and papery. However, the identity of the pest species was confirmed through morphological characteristics of male and female genitalia as well as sequence amplified product of Cytochrome c oxidase subunit I (COI) gene (GenBank No. ON545929). Biological studies revealed that the entire life cycle of the moth completed in 29.90 ± 2.42 days on average, while the range was between 25-34 days. The peak larval incidence was noticed in 16th SMW (Standard Meteorological Week) and 24th SMW with population of 12 and 15 larvae per plant during 2021 and 2022, respectively. The percent plant incidence levels ranged from 15 to 100% during the first year i.e. 2021 and 30 to 100% during the second year i.e. 2022. The correlation of mean larval population (r = −0.66) and percent plant incidence (r = −0.71) with weather parameters indicated a highly significant negative association with the maximum temperature and a significant positive correlation with maximum and minimum relative humidity. The parasitization of Choeras sp. (Braconidae: Hymenoptera) (GenBank No. OP293230) was observed on old age larvae of P. cribrata and the natural parasitization was recorded as 26% during the study period. This study provides a comprehensive information on the occurrence, nature of damage, biology, morphometry, seasonal incidence and natural enemy fauna associated with P. cribrata which will be helpful for implementation of Integrated Pest Management (IPM) strategies to curtail the pest problem on V. negundo, a valuable medicinal plant.