Description
Trichogramma is a minute parasitic wasp that attacks the eggs of over 150 species of moths. Adults are tiny, less than 1mm long, and yellowish-brown in color. Larvae develop entirely inside moth eggs, which darken when they are parasitized. Trichogramma populations can increase rapidly since they have more generations per year than their hosts. Trichogramma are native to north America and are found naturally in orchards, gardens and landscapes.
Application Rates
In orchards, release at the base of infested trees and release a few upwind to encourage their natural spread throughout the orchard.
- 1-2 per sq. ft, weekly during moth flight
- 50,000 to 100,000 per acre, weekly during moth flight
Target Pests
Lepidopteran pests such as tomato hornworm, corn ear worm, codling moth, cabbage looper, diamond back moth, oriental fruit moth, tobacco budworm, cabbage worm and more.
Life Cycle
Trichogramma undergo complete metamorphosis, with four stages: egg, larva, pupa and adult. A complete life cycle takes 14 days at 70°F. Larvae take 10 days to develop within the moth egg, which turns brown or black as the larvae pupate. Adults emerge within 2–3 days at 68–81°F and >60% relative humidity by chewing an exit hole through the host egg. Trichogramma overwinter as mature larvae within host eggs.
Males emerge first and await female emergence for mating. Adults feed on nectar, honeydew and pollen. Each female can parasitize about 100 host eggs and may also eat the host eggs to help fuel egg production. Trichogramma can live up to two months, depending on environmental conditions and the species of moth that they parasitize, with up to 30 generations per season.
Use in Biological Control
Optimum conditions for Trichogramma release are temperatures between 68-81°F with >60% RH. Moth species that lay their eggs in clusters can be more effectively controlled with Trichogramma than species that lay eggs individually.Timing is important to ensure moth eggs are available for parasitism, and all releases should be made at first sign of moth flight.
Trichogramma are weak flyers and must be well distributed throughout the crop for successful control. Use Bt (Bacillus thuringiensis) to control caterpillars until Trichogramma are well established. Avoid use of broad spectrum and persistent pesticides as these are toxic to Trichogramma wasps and other natural enemies.
Commercially Available Trichogramma Species
- Trichogramma brassicae – native to Europe for lepidopteran pests (European corn borer) in orchards and vegetable production, especially Cole crops (broccoli, cabbage, kale, mustard) and garlic and onion.
- Trichogramma minutum - native to eastern North America to control grape berry moth, cabbage looper, and codling moth in ornamentals, orchards, grape production, and forests.
- Trichogramma platneri - native to western North America used for control of codling moth and leafrollers in avocados, ornamentals, grapes, orchards and tall crops.
- Trichogramma pretiosum – native to North America for lepidopteran cotton and vegetable pests (bollworms and budworms). Use for greenhouse crops.
Recommendations for Farmers
A full sheet of 100,000 eggs at an application rate of 2/sq. ft. means that one sheet will easily cover an acre. People often release more, as it takes a little energy to distribute them effectively. They are routinely released weekly by growers to coincide with the egg laying and hatching of their target pest.
Hanging them immediately upon receipt might be the easiest method, but for years organic farmers have found great efficacy by putting the fresh egg tabs into a jar (and during cooler weather with slower hatching) adding a think streak of honey to the inside if the jar. The tiny wasps can then hatch and get a little energy drink. Cover with a little window screen on the top of the jar to keep predators out.
Upon hatching the Trichogramma can then fly out through the screen. If they are placed on the ground, slugs, snails or other predators can quickly wipe out them out.
Product Information
Trichogramma are shipped as parasitized moth eggs fixed to cardboard sheets. Each sheet holds about 125k. The sheets are perforated into 30 small squares, each with 4,000 to 5,000 Trichogramma. Carefully tear the sheets along the perforations and distribute immediately or hold in containers with food until the adults begin to emerge.
To increase the effectiveness of this parasitoid, provide an area for them to mate and feed before releasing.
- Enclose each square of cardboard in a small, screened paper cup along with a small piece of cotton moistened with dilute honey or fruit juice.
- Hold for 2-10 days at 76-78°F. When the Trichogramma begin to emerge, uncover and place the cups throughout the crop.
Further Resources
Trichogramma Parasitoids – UC IPM
Trichogramma Wasp – NC State Extension
Trichogramma Wasps – askIFAS
Trichogramma ostriniae and the European Corn Borer – Cornell
Effective Use of Trichogramma to Control the European Corn Borer - CABI