Description
Trichogramma is a minute parasitic wasp that attacks the eggs of over 150 species of moths and other insects, including cabbage looper, codling moth, oriental fruit moth, twig borers and fruit worms. Adults are less than 1 mm long. Larvae develop entirely inside the eggs of moths, which darken when they are parasitized. Trichogramma naturally occur in orchards, gardens, landscapes and wild areas, wherever eggs of their insect hosts are found.
Trichogramma minutum - native to Eastern North America and used for control of grape berry moth, cabbage looper and codling moth in ornamentals, orchards, grape production and forests.
Trichogramma platneri - native to Western North America and used for control of codling moth, leafrollers in avocados, ornamentals, grapes, orchards and tall crops.
Trichogramma brassicae - native to Europe and used to control lepidopteran vegetable pests (bollworms and budworms) in vegetable, orchard and field crops, especially Cole crops (broccoli, cabbage, kale, mustard) and leek, garlic and onion.
Target Pest
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 undergoes complete metamorphosis: egg, larva, pupa and adult. A complete life cycle takes 7-14 days. Sex ratio in the population is about equal. Mated females lay 60-70 eggs in moth eggs over a period of 1-2 weeks. Most Trichogramma eggs are laid within 1-2 days of mating. Larvae take 10 days to develop within the moth eggs, which turns brown or black as the larvae pupate. Trichogramma overwinter as mature larvae in host eggs. In mild winters they can be active throughout the year.
Adults begin to emerge within 2-3 days at 68-81°F and over 60% relative humidity. They chew a small hole in the moth egg to emerge. Males emerge slightly earlier and await female emergence for mating. Adults feed on nectar, honeydew and pollen.
Trichogramma numbers can increase rapidly because these beneficial insects have a quicker life cycle than their hosts, having more than 30 generations per season.
Total live span may up to a month, depending on temperature, relative humidity and species of moth parasitized.
Use in Biological Control
Several different species of Trichogramma are used in North American crops. Optimum conditions are moderate temperatures of 68-81°F and relative humidity of 60%. Moth species that lay eggs in clusters are more easily controlled using Trichogramma than those species that lay single eggs.
Product Information
Trichogramma are shipped as parasitized moth eggs fixed to cardboard sheets. Each sheet hold about 125,000 Trichogramma. The sheets are perforated into 30 small squares, each with 4,000-5,000 Trichogramma. Carefully tear the sheets along the perforations and either distribute them immediately throughout the crop or hold them in containers with food until the adults begin to emerge.
Incubation Method significantly improves the rates of emergence and provides an area for the Trichogramma to mate before release.
- Enclose each square of cardboard in a small vial or 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 until Trichogramma begin to emerge, and then place containers throughout the crop.
Introduction Rates
General Rates - 2 Trichogramma/sq. ft. (22/sq.m) weekly until caterpillar populations are controlled, or 22,000 wasps/10,000 sq. ft. (1,000/sq.m) weekly.
Greenhouse Rates - 2 Trichogramma/sq. ft. All releases should be made weekly at the first sign of moths, ensuring the Trichogramma are distributed evenly throughout the greenhouse. Continue regular weekly releases for at least 4 weeks or until control is achieved.
Outdoor Crops - Releasing Trichogramma on a regular basis ensures that mated females are always present to attack moth eggs. Releases should start as soon as moths are first detected (either seen flying or trapped in pheromone lure traps).
- Field Crops - 100,000 -300,000/acre over 3 weeks or evenly spread out over the egg-laying period of the target pest. Trichogramma can be released in large numbers using aircraft or drones. Release in early morning or late afternoon.
- Codling moth in orchards - 50,000-100,000/acre spread over three weeks, as soon as moths are detected in traps. In orchards, place some Trichogramma at the base of each infested tree. Releasing a percentage of the Trichogramma upwind may encourage their natural spread though the orchard.
- Home gardens - 12,000/week for 3 weeks.
Using Chemicals
Because Trichogramma are weak flyers, they must be well distributed throughout the crop. Use Bacillus thuringiensis (Dipel, Javelin, ZenTari) to control caterpillars until Trichogramma is well established.
Trichogramma wasps are generally sensitive to most insecticides as well as some fungicides and herbicides. The toxicity varies depending on the life stage exposed to the pesticide and the rate of application. Plastic covering or flooring used in greenhouses may harbor residues at levels that are harmful to this parasite for over 6 months. For more information, contact a member of the Sound Horticulture team.
