Uzi Fly

📖 Description

Uzi Fly (Exorista bombycis) is the most serious parasitoid pest of silkworms across the Indian subcontinent, causing estimated annual losses of ₹150-300 crore to the Indian silk industry. Particularly severe in the major silk-producing belts of Karnataka (Ramanagara, Chamarajanagar, Kolar — India’s largest mulberry silk producer contributing over 50% of national production), Andhra Pradesh (Anantapur, Chittoor), Tamil Nadu (Dharmapuri, Krishnagiri, Salem), West Bengal (Murshidabad, Malda — famous for Murshidabad silk), Assam (Kamrup, Goalpara — muga silk belt), and Jharkhand (Ranchi, Khunti — tasar silk belt). India is the world’s second largest silk producer (after China) with over 35,000 tonnes of silk annually, and the only country producing all four commercially important silks: mulberry (over 80% of production), tasar, eri, and muga (exclusive to Assam). The pest is unusual among silkworm parasitoids because (a) the adult fly is a strong flier and can locate silkworm rearing houses from kilometres away by detecting silkworm odours (kairomones), (b) a single female fly lays 300-1000 microtype eggs (0.2 mm each — among the smallest insect eggs) on the body of 4th-5th instar silkworm larvae or on mulberry leaves that larvae eat — eggs hatch when ingested or on contact, and maggots penetrate the silkworm body wall, (c) maggots feed internally on silkworm tissues for 5-7 days, often without immediately killing the silkworm — the silkworm may even spin its cocoon before being killed, resulting in a ruptured valueless cocoon, (d) the pest is most damaging during the rainy season (Jun-Oct) when fly activity is maximum and when silkworm rearings are most common, (e) the pest attacks all four silkworm species (mulberry, tasar, eri, muga) but is most damaging to mulberry silkworm (Bombyx mori — over 80% of Indian silk production), and (f) the pest has developed resistance to several insecticides in some regions due to overuse — and silkworms are extremely sensitive to insecticides (cannot use most chemical insecticides inside rearing houses). IPM with screened rearing houses (most effective prevention — 1 mm nylon mesh), age-disguise nets, UV light traps, diflubenzuron (Uzicide — chitin synthesis inhibitor that kills uzi maggots without harming silkworm), Trichopria hyperparasitoid releases, neem-based repellents, Vitex negundo (nirgundi) plantings around rearing houses, rearing house hygiene, synchronous rearing, and sericulture crop rotation provides effective and sustainable control. The pest is a particular concern for Indian sericulture because (i) India is the world’s second largest silk producer and silk is a major rural employment generator with over 80 lakh people involved in sericulture, (ii) much Indian sericulture is done by small and marginal farmers with limited access to IPM knowledge and screened rearing houses, (iii) traditional rearing houses are often open sheds that do not exclude uzi fly, (iv) the rainy season (Jun-Oct) — most favourable for uzi fly — is also the main silkworm rearing season in many parts of India, and (v) silkworms are extremely sensitive to insecticides — limiting chemical control options.