Berseem Flower Weevil
Tychius breviusculus
📖 Description
Tychius breviusculus, the Berseem Flower Weevil, is a specialist curculionid pest of berseem (Trifolium alexandrinum) seed crops in India. Berseem is India’s most important winter fodder crop, grown on over 2 million hectares primarily in the north-western plains — Punjab, Haryana, western Uttar Pradesh, Rajasthan, and parts of Madhya Pradesh and Gujarat. The crop provides high-quality green fodder for dairy animals from November to April and is the foundation of north-India’s winter dairy economy. While most berseem is harvested for forage, a portion is grown specifically for seed production to supply the next year’s planting — and this seed crop is the target of T. breviusculus. The female weevil uses her slender rostrum to chew a small hole in the developing flower bud or young pod, then lays an egg inside; the emerging larva feeds on the developing seeds, destroying them entirely. A single larva can destroy 3–5 seeds during its 14–18 day development. The pest is particularly damaging in late-maturing varieties (like ‘Mescavi’) which flower over a longer window, providing extended oviposition opportunity. The weevil is endemic to the Mediterranean and West Asia but is now established across all of India’s berseem-growing tracts. IPM packages developed by IGFRI (Indian Grassland and Fodder Research Institute) Jhansi emphasise early sowing, forage cutting before peak flowering in seed fields, and targeted insecticide applications at the bud-initiation stage as the core management tactics.
⚠️ Symptoms to watch for
- Adults chew small round holes in flower buds and young pods — the diagnostic 'shot-hole' damage; larvae feed inside the developing seeds, destroying them; infested pods are shrivelled, light, and contain frass instead of healthy seed. In berseem seed crops in Punjab (Ludhiana, Bathinda), Haryana, western Uttar Pradesh, and Rajasthan, heavy infestation can reduce seed yield by 30–50 %. The pest is particularly damaging in late-maturing berseem varieties grown for seed rather than forage.
🩹 Treatment
- Cultural: cut the berseem crop for forage before peak flowering to reduce adult oviposition sites; rogue out and destroy infested plants before larvae exit pods to pupate in soil. Mechanical: install yellow sticky traps at 8/ha to monitor adult activity. Biological: apply Beauveria bassiana at 5 g/L on the foliage; spray Metarhizium anisopliae at 5 g/L on the soil surface to target emerging adults. Chemical: spray lambda-cyhalothrin 5 EC @ 0.5 ml/L or acephate 75 SP @ 1 g/L at the bud-initiation stage, repeated at 10-day intervals until pod-fill.
🌿 Organic treatments
- Spray neem oil (Azadirachta indica) at 3 % emulsion at 7-day intervals from bud initiation; apply Beauveria bassiana at 5 g/L on the foliage; install yellow sticky traps at 8/ha for adult monitoring; cut the crop for forage before peak flowering to disrupt oviposition.
🧪 Chemical treatments
- Lambda-cyhalothrin 5 EC @ 0.5 ml/L, Acephate 75 SP @ 1 g/L, Quinalphos 25 EC @ 1.5 ml/L. Apply at the bud-initiation stage and repeat at 10-day intervals until pod-fill. Pre-harvest interval 14 days; avoid spraying during peak pollinator activity.
🛡️ Prevention
- Cut the berseem crop for forage before peak flowering in seed-production fields — this disrupts adult oviposition; adopt a 2-year rotation with non-legume cereals to break the soil-borne pupal stage; deep summer ploughing to expose soil-borne pupae to desiccation and bird predation; remove wild Trifolium hosts around field margins; install yellow sticky traps at 8/ha to detect adult emergence and time sprays precisely; in seed-production fields, adopt early sowing (early October) so the crop completes seed set before the spring adult peak.
🪴 Affected plants
- Berseem (Trifolium alexandrinum) — primary host; also reported on other Trifolium species and occasionally on lucerne (Medicago sativa) and Persian clover (Trifolium resupinatum).
🦋 Natural predators
- Predatory anthocorid bugs (Orius spp.) that attack eggs and neonate larvae in the buds, predatory mites on the foliage, spiders (Thomisidae), and ground beetles (Carabidae) that consume pupae in soil.
🌱 Host plants
- Trifolium alexandrinum (berseem — primary), other Trifolium spp., Medicago sativa (lucerne — minor), Trifolium resupinatum (Persian clover — minor).
🔄 Lifecycle
- Adult female lays 40–100 eggs singly inside flower buds or young pods.
- Egg stage 5–7 days.
- Larva feeds inside the pod on developing seeds for 14–18 days through three instars.
- Mature larva exits the pod and drops to the soil, where it pupates in an earthen cell; pupal stage 8–14 days.
- Adult longevity 30–60 days.
- Total lifecycle 30–45 days.
- Three to four overlapping generations per berseem season (October–April).
📅 Season
- Active November–April across the north-Indian berseem belt; peak infestation February–April during the flowering and seed-set period.
- Adults over-summer in crop debris and soil, emerging the following October–November when the new berseem crop is sown.
🔎 Appearance
- Adult is a tiny greyish-brown curculionid weevil with a long slender rostrum (snout) about half the body length; the elytra are mottled with darker brown patches and a pale mid-line stripe; legs are reddish-brown.
- Larva is a legless, C-shaped white grub with a dark-brown head capsule, found inside the developing seed pods.
- Pupa is creamy-white, found in a small earthen cell in the soil.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Medium
🗺️ Geographic regions
- Indian Subcontinent (Punjab
- Haryana
- western UP
- Rajasthan
- Madhya Pradesh
- Gujarat)
- Mediterranean basin
- West Asia
- parts of North Africa.
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