Diversity and Seasonal Incidence of Insect Pests of Broccoli (Brassica oleracea var. italica L.) and their Relationship with Abiotic Factors

Abstract

Background: Broccoli is a nutrient-rich cole crop gaining importance in India due to its high dietary and economic value. However, its productivity is severely constrained by the infestation of several insect pests, particularly aphids and lepidopteran borers, which cause considerable yield losses. Aims: To study the diversity and seasonal incidence of insect pests infesting broccoli (Brassica oleracea var. italica) and to determine their relationship with key abiotic factors. Study Design: The experiment was conducted using a Randomized Block Design (RBD) with three replications under natural field conditions. Place and Duration of Study: The study was carried out at Ummulong, West Jaintia Hills, Meghalaya, during Rabi season from December 2020 to March 2021. Methodology: Broccoli was grown following standard agronomic practices in plots of 2.2 m × 2.2 m. Five plants per plot were randomly selected and tagged for observations. Weekly monitoring of insect pests was conducted from 7 days after transplanting until harvest. Different sampling techniques were employed based on pest feeding habits. Meteorological data (temperature, relative humidity, and rainfall) were recorded, and correlation and regression analysis were performed to assess their influence on pest incidence. Results: A total of 12 insect pest species belonging to five orders and ten families were recorded. Among them, the green peach aphid (Myzus persicae) and Indian cabbage white butterfly (Pieris canidia) were identified as major pests. The peak population of M. persicae (34.17 aphids per plant) was observed during the last week of December, while P. canidia reached its maximum (2.57 larvae per plant) in the third week of January. Correlation analysis revealed a significant negative relationship between pest population and both maximum and minimum temperatures, whereas relative humidity and rainfall showed non-significant relation. Conclusion: The study demonstrated that temperature is a critical factor influencing the incidence of major insect pests in broccoli, with lower temperatures favoring pest buildup. These findings emphasize the importance of weather-based pest forecasting for timely and effective implementation of integrated pest management strategies to reduce yield losses.