🐞 Predators and Parasitoids as Biocontrol Agents

Biocontrol agents reduce pest pressure naturally and form a central pillar of integrated pest management in field and horticultural crops.

---

Predators in Biological Control

Predators are free-living organisms that kill and consume multiple prey individuals during their lifetime. They play a critical role in naturally regulating pest populations in agricultural ecosystems.

Ladybird Beetles (Coccinellidae)

Ladybird beetles are among the most well-known and effective predators of soft-bodied insects. Both adults and larvae are voracious feeders on aphids, mealybugs, scale insects, and whiteflies. A single larva of Coccinella septempunctata (seven-spotted ladybird) can consume 200-300 aphids during its development. Cryptolaemus montrouzieri (Australian ladybird beetle) is mass-reared and released for the biological control of mealybugs in grapes, citrus, coffee, and guava orchards across India. It was one of the earliest successful classical biocontrol introductions in Indian agriculture.

Green Lacewings (Chrysopidae)

Chrysoperla zastrowi sillemi (formerly identified as C. carnea in India) is a highly effective generalist predator. Its larvae, known as "aphid lions," feed on aphids, thrips, whitefly nymphs, lepidopteran eggs, and mites. A single larva can consume over 500 aphids during development. Chrysoperla is commercially mass-reared on factitious hosts (Corcyra cephalonica eggs) and released as eggs or second-instar larvae in cotton, vegetables, and pulse crops at rates of 50,000-1,00,000 per hectare.

Spiders

Spiders (Order Araneae) are generalist predators abundant in rice paddies, cotton fields, and vegetable ecosystems. Important families include Lycosidae (wolf spiders), Araneidae (orb-web spiders), and Oxyopidae (lynx spiders). Rice fields in Asia may harbour 100-400 spiders per square metre, providing substantial pest suppression of planthoppers, leafhoppers, and stem borers.

Other Important Predators

Reduviid bugs (assassin bugs) prey on caterpillars and other soft-bodied insects. Syrphid flies (hoverflies) have larvae that are effective aphid predators. Dragonflies and damselflies capture mosquitoes, midges, and small moths in flight.

Parasitoids in Biological Control

Parasitoids are insects whose immature stages develop on or within a single host, eventually killing it. Unlike parasites, parasitoids are lethal to their hosts. They are classified as egg, larval, or pupal parasitoids based on the host stage attacked.

Trichogramma Species

Trichogramma spp. are minute egg parasitoids (family Trichogrammatidae) that are the most widely used biocontrol agents globally. They parasitize eggs of lepidopteran pests by inserting their own eggs inside. Important species include T. chilonis (used against sugarcane internode borer, rice stem borer, and cotton bollworm) and T. japonicum (rice stem borer). Trichogramma is mass-produced on Corcyra cephalonica (rice moth) eggs in laboratories and released as parasitized egg cards at the rate of 1-1.5 lakh per hectare, with 4-6 releases at weekly intervals.

Bracon Species

Bracon brevicornis and Bracon hebetor are larval ectoparasitoids of lepidopteran borers and storage pests respectively. Bracon hebetor parasitizes the larvae of stored grain pests like Corcyra cephalonica and Plodia interpunctella, making it useful in integrated management of warehouse pests.

Cotesia Species

Cotesia flavipes is a gregarious larval endoparasitoid introduced into India for the biological control of sugarcane internode borer (Chilo sacchariphagus indicus) and spotted stem borer (Chilo partellus) in sorghum. Multiple parasitoid larvae develop inside a single host caterpillar and emerge to pupate in characteristic white cocoon clusters on the host body.

Other Key Parasitoids

Aphelinus mali is used against woolly apple aphid. Chelonus blackburni is an egg-larval parasitoid of cotton bollworms. Goniozus nephantidis parasitizes coconut black-headed caterpillar. National Biocontrol Laboratories and State Biocontrol Laboratories across India mass-produce and supply these agents to farmers under IPM programmes.

---

Summary Cheat Sheet

• Predators consume multiple prey and provide broad pest suppression.
• Parasitoids are host-lethal and stage-specific (egg, larval, pupal).
• Trichogramma, Chrysoperla, Cotesia, and Bracon are major field agents.
• Release timing and compatibility with pesticide use determine success.

References

1 source • [1]

[1]

Standard biological control references used for lesson preparation.