Soybean Semilooper

📖 Description

Soybean Semilooper (Chrysodeixis acuta), also called Green Semilooper or Soybean Pod Feeder, is an important defoliator pest of soybean across the Indian subcontinent, particularly severe in the major soybean-growing belts of Madhya Pradesh (Indore, Ujjain, Dewas, Shajapur, Bhopal, Vidisha, Sehore — India’s largest soybean-producing state with over 50% of national area), Maharashtra (Nagpur, Wardha, Amravati, Latur, Osmanabad), Rajasthan (Kota, Bundi, Baran, Jhalawar), Telangana (Adilabad, Nirmal, Kumuram Bheem), Andhra Pradesh (Anantapur, Kurnool), Karnataka (Belgaum, Bidar, Kalaburagi) and Gujarat (Vadodara, Panchmahal) where India is the world’s 5th largest producer of soybean (over 12 million hectares cultivated, producing over 13 million tonnes annually — soybean is a critical oilseed and protein crop for India, with the residue (deoiled cake) a major export). The pest is particularly damaging because (a) it has a very short life cycle (28-35 days) allowing rapid population buildup — a single female can lay 300-700 eggs, (b) the larvae feed gregariously in early instars (1st-3rd) and can defoliate entire patches of the field in 7-10 days during outbreak, (c) later instars also feed on pods (chewing into pods and consuming developing seeds) causing direct yield loss, not just defoliation, (d) the pest has a very wide host range (soybean, mungbean, urdbean, cowpea, groundnut, tobacco, cotton, sunflower, tomato, brassicas) allowing populations to persist between soybean crops via weeds and other crops, (e) the adult moth is a strong flier capable of long-distance migration allowing rapid colonization of new fields, and (f) the pest has developed resistance to many older insecticide classes (organophosphates, pyrethroids) in many parts of India due to repeated spraying. IPM with pheromone trap monitoring (most critical for early detection — adult moth activity peaks before larval outbreak), biological control (NPV of Plusiinae is highly specific and effective, Bt on young larvae, Trichogramma egg parasitoid releases), neem-based sprays, and need-based insecticide rotation (apply on young larvae for best efficacy) provides effective and sustainable control. The pest is a particular concern for Indian soybean growers because of the rapid defoliation potential — entire fields can be defoliated in 7-10 days during outbreak — making early detection through pheromone trapping essential. Climate change with warmer conditions is allowing the pest to expand its range into previously cooler soybean-growing regions of northern India.