Cashew Blossom Webber
Macalla plicatalis
📖 Description
The Cashew Blossom Webber (Macalla plicatalis) is one of the most damaging yet underappreciated pests of Indian cashew — a crop on which India was historically the world’s largest producer (until recently overtaken by Côte d’Ivoire) and remains the largest processor, with annual raw nut production of 0.7–0.8 million tonnes across 1.0 million hectares concentrated in Kerala, Karnataka, Goa, Maharashtra, Andhra Pradesh, Odisha, and West Bengal. The pest’s damage is devastating precisely because it attacks the flowering panicle — the single organ that determines the entire season’s yield. A cashew panicle is a complex indeterminate structure that flowers over 2–3 months and can carry 100+ individual flowers, of which only 5–15 % set fruit under normal conditions. The blossom webber’s silken web destroys all of these potential fruits in a single infestation event, and because cashew flowers only once per year (January–March in peninsular India), the damage is irrecoverable for that season. The pest is particularly severe in the high-rainfall West Coast tract (Kerala, Karnataka, Goa) where the humid microclimate supports rapid larval development; in the drier Vidarbha and Andhra Pradesh tracts pressure is moderate. India’s cashew industry employs over 500,000 people (largely women) in processing factories, and the cashew export trade was worth ₹6,000 crore in 2022–23 — making the blossom webber a significant threat to rural employment in coastal India.
⚠️ Symptoms to watch for
- Dense silken webbing enclosing the entire flowering panicle — the diagnostic symptom. Inside the web, flowers and young nuts are chewed and skeletonised; frass (small greenish-black pellets) accumulates in the web. The infested panicle fails to set nuts or produces shrivelled, empty nuts. A single caterpillar can web and destroy an entire panicle bearing 80–150 potential fruits; severe infestations reduce nut yield by 30–60 % in the critical January–March flowering window.
🩹 Treatment
- Cultural: hand-pick and destroy webbed panicles before the larva pupates — effective in smallholdings and the cheapest control. Mechanical: shake the lower branches to dislodge larvae onto a sheet, then collect and destroy. Chemical: spray lambda-cyhalothrin 5 EC at 0.5 ml/L or chlorpyrifos 20 EC at 2 ml/L at the first sign of webbing, ensuring the spray penetrates the silken shelter; add a non-ionic surfactant (0.1 %) to break the surface tension of the web.
🌿 Organic treatments
- Manual removal and destruction of webbed panicles (the single most effective organic practice, 60–80 % control); spray neem oil 5 % emulsion with 0.1 % soap solution at 7-day intervals from panicle emergence to fruit-set; release Trichogramma chilonis at 50,000/ha to parasitise eggs; apply Bacillus thuringiensis var. kurstaki at 1 kg/ha — Btk must be ingested to be effective, so spray it on adjacent un-webbed foliage where young larvae will feed.
🧪 Chemical treatments
- Lambda-cyhalothrin 5 EC @ 0.5 ml/L, Chlorpyrifos 20 EC @ 2 ml/L, Emamectin benzoate 5 SG @ 0.4 g/L, Spinosad 45 SC @ 0.5 ml/L, Novaluron 10 EC @ 1.0 ml/L. Pre-harvest interval 21 days; avoid spraying during peak pollinator activity (10 am–2 pm).
🛡️ Prevention
- Prune the cashew canopy in October–November (post-monsoon) to improve air circulation and expose overwintering larvae to predators; remove and burn all webbed panicles weekly during the flowering season; plant cashew varieties with loose open panicles (e.g. Vengurla-7, Bhaskara) which are less preferred for oviposition than compact-panicle types; maintain a clean, weed-free basin; intercrop with pigeonpea or cowpea to boost generalist predator populations.
🪴 Affected plants
- Cashew (Anacardium occidentale) — primarily the flowering panicles; occasionally on Mangifera indica (mango) and Semecarpus anacardium (marking nut) when cashew is not in bloom.
🦋 Natural predators
- Trichogramma chilonis (egg parasitoid — 40–60 % natural parasitism in unsprayed orchards), Apanteles sp. (larval braconid parasitoid), predatory ants (Oecophylla smaragdina, Dolichoderus sp.), predatory pentatomid bugs (Eocanthecona furcellata), spiders (Salticidae and Thomisidae), lacewing larvae (Chrysoperla zastrowi sillemi), and insectivorous birds.
🌱 Host plants
- Anacardium occidentale (primary host — cashew), Mangifera indica (mango — when cashew is not flowering), Semecarpus anacardium (marking nut), Spondias spp. (hog plum).
🔄 Lifecycle
- Adult female lays 80–150 small pale-yellow, scale-like eggs singly or in small groups on cashew panicles and young leaves.
- Egg stage 4–6 days.
- Larva passes through 5–6 instars over 18–28 days, webbing the panicle progressively as it grows.
- Pupation occurs inside the web or in rolled leaves on the ground; pupal stage 10–14 days.
- Adult longevity 7–12 days.
- Total lifecycle 35–55 days; 3–4 overlapping generations per year, with peak activity coinciding with the January–March cashew flowering season.
📅 Season
- Peak infestation during the cashew flowering season (January–March in peninsular India; March–May in eastern India).
- Low activity during the post-harvest and monsoon months (June–December).
🔎 Appearance
- Adult is a small pale-straw to buff-coloured pyralid moth with darker wavy transverse lines on the forewings; at rest the wings are held tent-like over the body.
- Larva is a slender, semi-translucent greenish-yellow caterpillar with a shiny black head and sparse pale setae.
- The diagnostic behaviour is webbing — the larva ties together cashew panicles, flowers, and young leaves with dense silken threads, forming a messy shelter inside which it feeds concealed.
💥 Damage level
- Severe
🔁 Reproduction rate
- Medium
🗺️ Geographic regions
- Indian Subcontinent (Kerala
- Karnataka
- Goa
- Maharashtra
- Tamil Nadu
- Andhra Pradesh
- Odisha
- West Bengal)
- Sri Lanka
- Southeast Asia (Myanmar
- Thailand
- Vietnam
- Indonesia)
- tropical Africa (introduced range).
Have an Insect to Identify?
Upload or take a photo of an insect on your plant and our AI will identify it and recommend treatments.
📷 Diagnose from Image