Red hairy caterpillar (Amsacta albistriga) in groundnut Photo: L. Shyamal · CC BY 2.5 · source ↗

Red hairy caterpillar (Amsacta albistriga) in groundnut

Red hairy caterpillar (RHC), Amsacta albistriga Walker (Lepidoptera: Erebidae, formerly Arctiidae), is a sporadic but extremely damaging defoliator of rainfed groundnut, castor, sunflower and pulses in peninsular India. Outbreaks track the southwest monsoon — the moth emerges within days of the first heavy rain — and on bad years it can defoliate a whole groundnut block in three to four nights of larval feeding. Anantapur, Kurnool, Mahabubnagar, Bellary, Chitradurga and Tumkur are recurring outbreak districts.

Identification

Adult moths are stout, 35-50 mm wing-span, with cream forewings carrying a prominent red-orange transverse stripe and red abdomen with black dorsal spots. Eggs are pale yellow, laid in clusters of 500-1000 on the underside of leaves of host or non-host plants. Newly emerged larvae are gregarious, pale and feed superficially. Later instars are red-brown to black with long tufts of reddish-brown hairs all over the body; full-grown larvae reach 40-50 mm. They are conspicuous and easy to identify in the field.

Hosts and lifecycle

RHC has a wide host range — groundnut, castor, sunflower, redgram, blackgram, sorghum, pearl millet, sesame and many weeds. The pest spends 8-10 months in soil-bound pupae and emerges synchronously after the first 25-50 mm of monsoon rain. Females mate on the night of emergence and start laying within 24-48 hours. Larval period is 25-35 days through six instars, followed by pupation in the soil at 5-10 cm depth. There is a single generation per year, but emergence may be staggered over 2-3 weeks. Older larvae are voracious, eat leaves to bare petioles, and disperse to neighbouring fields in marauding bands.

Economic impact

Because emergence is synchronous and the larvae are gregarious, a single outbreak event can defoliate 50-80 percent of a young groundnut crop. Surveys by ICAR-CRIDA and ANGRAU in Anantapur have recorded yield losses of 25-60 percent in outbreak years, with worst-affected fields harvested only as fodder. The pest aggregates strongly in pheromone-monitored hotspots and follows a roughly 4-5 year cyclical outbreak pattern tied to good monsoon onset after dry years.

Management

Community light traps: synchronous moth emergence makes mass trapping highly effective. Erect one light trap per 4-5 ha at field bunds and village commons for the first 15-20 days after monsoon onset (see Solar Light Traps). One trap can catch 200-500 moths per night during peak.
Cultural: deep summer ploughing exposes pupae to predators and sun; bonfires of dry trash on emergence nights kill flying moths; egg-mass collection and destruction is feasible because eggs are conspicuous and clustered.
Biological: NPV (Nuclear Polyhedrosis Virus) of Amsacta at 250-500 LE/ha controls early instars; conserve predators (reduviid bugs, Bracon parasitoid).
Chemical: at first sign of gregarious early-instar feeding (within 7-10 days of moth emergence), spray chlorantraniliprole 18.5 SC at 0.3 ml/L or flubendiamide 480 SC at 0.25 ml/L. Late-instar control with dichlorvos 76 EC at 1.5 ml/L combined with poison bait (10 kg rice bran + 1 kg jaggery + 100 g monocrotophos / 200 g chlorpyrifos in 5 L water) placed at field corners at dusk is also recommended.

Sources

Red hairy caterpillar management. ICAR-Directorate of Groundnut Research, Junagadh.
Amsacta albistriga. CABI Compendium.
IPM Package for Groundnut. ICAR-National Centre for Integrated Pest Management.