Castor Semilooper
Achaea janata
📖 Description
Castor Semilooper is the most destructive pest of castor across the Indian subcontinent, particularly in Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, Rajasthan, and Odisha. Adult female moths lay eggs on the underside of leaves. Newly hatched larvae feed gregariously on leaf tissue, eating round holes; older larvae disperse and eat entire leaves, often defoliating plants from the top down. Heavy infestation can completely defoliate castor fields within days, severely reducing capsule and oil yield. The pest’s high reproductive rate (each female lays 400-800 eggs) and multiple generations per season (5-7) allow populations to explode rapidly. The pest also attacks Croton weeds, which serve as alternate hosts. Handpicking larvae in small plots, biological control with NPV and Bt, and judicious chemical rotation are key management strategies. Light trapping is also valuable because adults are strongly attracted to light.
⚠️ Symptoms to watch for
- Round holes in leaves, defoliation starting from top, only midribs and petioles remaining in heavy infestation, complete defoliation in severe cases, stunted plants, reduced capsule and yield formation, yield loss 30-50%
🩹 Treatment
- Handpick larvae in small plots, apply neem oil 5ml/L, spray Bacillus thuringiensis @ 2g/L, use recommended insecticides at early larval stage, set up light traps @ 1/ha
🌿 Organic treatments
- Handpick larvae in small plots (drop into kerosenated water), spray neem oil 5 ml/L with sticker, apply Bacillus thuringiensis @ 2 g/L in evening, apply 5% NSKE, set up light traps @ 1/ha for adult monitoring, apply NPV @ 250 LE/ha, release Trichogramma chilonis @ 50,000/ha, apply Beauveria bassiana
🧪 Chemical treatments
- Emamectin benzoate 5 SG @ 0.5 g/L, Indoxacarb 14.5 SC @ 1 ml/L, Spinosad 45 SC @ 0.5 ml/L, Chlorantraniliprole 18.5 SC @ 0.3 ml/L, Lambda-cyhalothrin 5 EC @ 1 ml/L (apply at early larval stage)
🛡️ Prevention
- Plant early to escape peak moth activity, inspect crop weekly for egg masses and young larvae, handpick larvae in small plots, set up light traps for adult monitoring, deep plough after harvest to expose pupae, balanced fertilizer use, conserve predatory bugs and birds, remove alternate host (Croton) around fields
🪴 Affected plants
- Castor (Primary), Croton, Pomegranate, Citrus, Rose, Some Ornamentals
🦋 Natural predators
- Spiders, Predatory Bugs, Birds, Frogs, Parasitic Wasps, NPV virus
🌱 Host plants
- Ricinus communis, Croton spp., Punica granatum, Citrus spp., Rosa spp.
🔄 Lifecycle
- Female lays 400-800 eggs singly on the underside of leaves.
- Eggs hatch in 3-5 days.
- Larvae feed for 12-20 days, passing through 5-6 instars.
- Pupation occurs in soil or leaf litter, lasting 7-12 days.
- Adults live 7-15 days.
- Total life cycle 25-40 days; 5-7 overlapping generations per year.
📅 Season
- Year-round, peaks Aug-Nov during castor growing season
🔎 Appearance
- Adults are medium-sized greyish-brown moths with distinctive wavy lines and a black spot on each forewing; hindwings have a black band with white spots.
- Larvae are slender, smooth, greenish-yellow semiloopers (looping caterpillars) with white longitudinal stripes, growing up to 50 mm.
💥 Damage level
- High
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- Southeast Asia
- East Asia
- Africa
- Australia
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