Trichogramma Egg Parasitoid
Trichogramma chilonis Ishii [and other Trichogramma spp.]
📖 Description
Trichogramma Egg Parasasitoid (Trichogramma chilonis and related Trichogramma species) is one of the most important natural enemies of lepidopteran (moth and butterfly) pests in Indian agriculture and the most widely used augmentative biological control agent in India. Trichogramma are minute wasps (0.3-0.6 mm long — among the smallest insects known) that parasitise the eggs of over 400 lepidopteran pest species — including Helicoverpa armigera (the most destructive pest of Indian agriculture — causes over ₹10,000 crore in crop losses annually across cotton, pigeonpea, chickpea, tomato, chilli, and other crops), Spodoptera litura (the tobacco caterpillar — major polyphagous pest), Pectinophora gossypiella (the pink bollworm of cotton), Earias spp. (the spotted/spiny bollworms of cotton), Chilo partellus (the spotted stem borer of maize and sorghum), Scirpophaga incertulas (the yellow stem borer of rice), Sesamia inferens (the pink stem borer of maize and rice), Maruca vitrata (the pod borer of pulses), Plutella xylostella (the diamondback moth of cabbage and cauliflower), Pieris brassicae (the cabbage butterfly), Achaea janata (the castor semilooper), Leucinodes orbonalis (the brinjal shoot and fruit borer), Ostrinia furnacalis (the Asian corn borer), and many other caterpillar pests. India has one of the world’s largest Trichogramma production and release programmes — over 5 lakh hectares of crops are treated annually with Trichogramma releases, particularly in cotton (for bollworms), sugarcane (for borers), rice (for stem borers), maize (for stem borer), pigeonpea and chickpea (for Helicoverpa pod borer), vegetables (for diamondback moth, fruit borers), and fruits. The wasp is unusual among biological control agents because (a) it is an egg parasitoid — it kills the pest before the pest can damage the crop (the pest egg never hatches into a damaging caterpillar), (b) the female wasp lays 1-3 eggs inside a single lepidopteran egg — the wasp larva develops inside the pest egg, pupates inside the egg, and the adult wasp emerges through a small hole cut in the egg — the entire development takes 7-10 days, (c) a single female wasp can parasitise 50-100 pest eggs in her 5-10 day lifespan — providing effective pest suppression, (d) Trichogramma is mass-reared commercially in India on Corcyra cephalonica (rice moth) eggs — production is done by NBAIR (Bengaluru — National Bureau of Agricultural Insect Resources), state agricultural universities, and over 100 private biocontrol companies — Tricho cards (cards with parasitised eggs) are commercially available at ₹50-100 per card, (e) the wasp is released as Tricho cards @ 50,000 wasps/ha at 7-10 day intervals — based on pheromone trap monitoring of adult moths (first release 7-10 days after first moth catch; repeat for 4-6 releases per crop season), (f) parasitism rates of 60-90% are achievable with mass releases — providing effective biological control, (g) Trichogramma has 30-50 overlapping generations per year in tropical India — allowing rapid population buildup in response to pest outbreaks, and (h) the wasp is sensitive to most broad-spectrum insecticides — IPM programmes must use selective insecticides (Bt, Spinosad, Emamectin, Chlorantraniliprole, Indoxacarb) to conserve Trichogramma populations. Conservation biological control (enhancing Trichogramma populations through flowering border crops, intercrops, refugia, and avoidance of broad-spectrum insecticides) is the most cost-effective way to maintain healthy Trichogramma populations in agricultural and horticultural crops. Augmentative biological control (mass-rearing and release of Trichogramma) is particularly effective against Helicoverpa armigera — the most destructive pest of Indian agriculture. The wasp is a particular asset for Indian farmers because (i) it provides free biological control of Helicoverpa armigera — the most destructive pest of Indian agriculture, (ii) it is native to India — well-adapted to Indian agroecological conditions, (iii) it is mass-reared commercially in India — Tricho cards are commercially available at ₹50-100 per card, (iv) it is the most widely used augmentative biological control agent in India — over 5 lakh hectares treated annually, (v) it is highly effective against multiple lepidopteran pests (Helicoverpa, Spodoptera, Pectinophora, Earias, Chilo, Scirpophaga, Sesamia, Maruca, Plutella, Pieris, Achaea, Leucinodes, Ostrinia), and (vi) conserving Trichogramma populations through IPM is essential for sustainable agriculture in India.
⚠️ Symptoms to watch for
- Not applicable — this is a beneficial insect that should be conserved, not controlled.
- Parasitism symptoms (visible in pest eggs): parasitised lepidopteran pest eggs turn black (instead of the normal yellowish-cream colour) due to parasitoid pupal formation inside the egg
- parasitised eggs fail to hatch (no caterpillar emerges — instead, adult Trichogramma wasps emerge through a small hole cut in the egg).
- Parasitism rates of 60-90% are achievable with mass releases of Trichogramma — providing effective biological control of target lepidopteran pests.
🩹 Treatment
- Not applicable — this is a beneficial insect that should be conserved and released, not controlled.
- Mass-rearing: Trichogramma is mass-reared on Corcyra cephalonica (rice moth) eggs in laboratories — commercial production is done by NBAIR (Bengaluru), state agricultural universities, and private biocontrol companies.
- Release: Trichogramma is released as 'Tricho cards' (cards with parasitised Corcyra eggs containing Trichogramma pupae) — each card contains about 20,000 parasitised eggs
- cards are stapled to crop leaves at 50,000/ha rate
- adult wasps emerge from cards in 2-3 days and parasitise pest eggs in the crop.
- Release timing: based on pheromone trap monitoring of adult moths — first release 7-10 days after first moth catch
- repeat at 7-10 day intervals for 4-6 releases per crop season.
🌿 Organic treatments
- Not applicable — this is a beneficial insect that should be conserved and released, not controlled.
- Trichogramma is itself an organic biological control agent.
- Mass-release procedure: order Tricho cards from NBAIR (Bengaluru), state agricultural universities, or private biocontrol companies — cards are delivered with parasitised eggs about to emerge.
- Store cards in cool dark place (15-20°C) for up to 5 days before release.
- Release @ 50,000/ha (about 2-3 Tricho cards per hectare) — staple cards to crop leaves at 50-100 locations uniformly distributed across the field.
- Release timing: based on pheromone trap monitoring — first release 7-10 days after first moth catch
- repeat at 7-10 day intervals for 4-6 releases per crop season.
- Avoid irrigation or heavy rain for 24 hours after release.
- Conserve natural enemies by avoiding broad-spectrum insecticides.
🧪 Chemical treatments
- Not applicable — this is a beneficial insect that should be conserved and released, not controlled.
- When pesticide application is necessary for other pests, use selective insecticides that are relatively safe to Trichogramma: Bacillus thuringiensis (Bt) @ 1 g/L, Spinosad 45 SC @ 0.2 ml/L, Emamectin Benzoate 5 SG @ 0.4 g/L, Chlorantraniliprole 18.5 SC @ 0.3 ml/L, Indoxacarb 14.5 SC @ 0.5 ml/L — AVOID broad-spectrum insecticides (organophosphates like Chlorpyriphos, Quinalphos, Dichlorvos, Monocrotophos; carbamates like Carbaryl, Methomyl; pyrethroids like Lambda-Cyhalothrin, Cypermethrin, Deltamethrin; neonicotinoids like Imidacloprid, Thiamethoxam, Acetamiprid — these kill Trichogramma and other natural enemies).
🛡️ Prevention
- Not applicable — this is a beneficial insect that should be conserved and enhanced, not prevented.
- To enhance Trichogramma populations in agricultural and horticultural crops: plant flowering border crops and intercrops (marigold, buckwheat, mustard, sunflower, coriander, dill, phacelia — provide nectar for adult Trichogramma — adult wasps need nectar to live longer and parasitise more eggs), provide refugia (perennial vegetation, hedgerows, cover crops, fallow strips — provide overwintering and resting sites), avoid broad-spectrum insecticides (organophosphates, carbamates, pyrethroids, neonicotinoids — these kill Trichogramma and other natural enemies), use selective insecticides when pesticide application is necessary (Bt, Spinosad, Emamectin, Chlorantraniliprole, Indoxacarb — these are relatively safe to Trichogramma), apply insecticides in the early morning or late evening when Trichogramma are less active, apply insecticides only when pest populations cross the Economic Threshold Level (ETL) — not as a routine preventive spray, practice crop rotation with diverse crop species (provides diverse host eggs for Trichogramma), maintain some weed diversity in field borders (provides alternative host eggs and habitat — but control weeds within the crop to avoid competition), implement Integrated Pest Management (IPM) that prioritises biological control over chemical control, mass-release Trichogramma chilonis @ 50,000/ha at 7-10 day intervals based on pheromone trap monitoring (most widely used augmentative biological control in India — over 5 lakh hectares treated annually), conserve native Trichogramma populations by avoiding any unnecessary pesticide application, support IPM programmes that integrate Trichogramma releases with pheromone-based monitoring and selective insecticide use.
🪴 Affected plants
- Not a plant pest — a beneficial egg parasitoid of lepidopteran (moth and butterfly) pest eggs.
- India has one of the world's largest Trichogramma production and release programmes — over 5 lakh hectares of crops are treated annually with Trichogramma releases, particularly in cotton, sugarcane, rice, maize, pigeonpea, chickpea, vegetables, and fruits.
- Trichogramma chilonis is the most widely used species in India.
🦋 Natural predators
- Spiders (capture adults in webs), predatory bugs (limited).
- Trichogramma has few natural enemies due to its minute size and concealed development inside pest eggs.
🌱 Host plants
- Not a plant pest — Trichogramma is a beneficial egg parasitoid of lepidopteran pest eggs.
- Found wherever lepidopteran pest eggs are available as hosts — over 400 lepidopteran species across all major crops.
🔄 Lifecycle
- Adult female wasp lays 1-3 eggs inside a single lepidopteran pest egg (using her ovipositor to pierce the pest egg chorion).
- Wasp egg hatches in 1-2 days.
- Larva feeds on the pest egg contents, developing through 3 instars over 3-5 days.
- Larva pupates inside the pest egg (the pest egg turns black — diagnostic for Trichogramma parasitism).
- Pupal stage 2-4 days.
- Adult wasp emerges through a small hole cut in the pest egg.
- Adult lifespan 5-10 days (females mate and lay eggs in 50-100 pest eggs during her lifetime).
- Total life cycle 7-10 days at 25-30°C; 30-50 overlapping generations per year in tropical India.
- Adult wasps feed on nectar (flowering border crops and intercrops provide nectar — extending wasp lifespan and parasitism rate).
📅 Season
- Active year-round in tropical India; peaks Mar-Oct (warm conditions most favourable for wasp reproduction, and lepidopteran pest populations are highest during this period).
- Wasp activity is lowest during the cool dry winter (Dec-Feb) when temperatures are too low for wasp flight and pest populations are at their lowest.
🔎 Appearance
- Adult is a minute, yellowish-brown wasp (family Trichogrammatidae) with red eyes, short antennae, and fringed wings (hairs on wing margin — characteristic of Trichogrammatidae); body compact; legs yellowish.
- So small (0.3-0.6 mm) that it is barely visible to the naked eye — requires 20× hand lens to see clearly.
- Females are slightly larger than males.
- Eggs, larvae, and pupae develop inside the host egg (lepidopteran pest egg) and are not visible without dissecting the host egg.
- Parasitised host eggs turn black (diagnostic for Trichogramma parasitism).
- Distinct from other parasitoids by minute size and occurrence inside lepidopteran eggs.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- Southeast Asia
- Cosmopolitan in Tropical
- Subtropical
- and Temperate Regions Worldwide
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