Trichogramma Release Techniques


Release on cards

Release as adults


Trichogramma are shipped (as pupae) inside of grain moth eggs ready to emerge as adults. They can be loose or glued to perforated cards. Loose eggs can be divided into paper cups or other containers; there are approximately 20,000 eggs in a cubic centimeter (ml). The alternative of moth eggs glued on cards with 100,000 Trichogramma per card (up to 120,000) has benefits and limitations. Each card is broken into 30 hangable units with approximately 3,300 parasitized eggs to hang on twigs allowing ease of distribution especially in trees and vines.

Tricho Cards

There are approximately 100,000 Trichogramma per card. Each card can be broken into 30 squares with 4,000 parasites per square inch -- this permits even distribution in fields and orchards. Loose eggs can be divided into paper cups; there are approximately 20,000 eggs in a cubic centimeter.


Trichogramma card with nominal 100K parasitized moth eggs. The card is perforated to cut into 30 tabs (3/4 X 2 inch), each with a door hanger style hook on one end. Each tab has a nominal 3,300 egg


Trichogramma wasps emerge from cards in two to five days, depending on temperature, which should ideally be 80º to 90º F. Emergence can be delayed by holding parasitized moth eggs at cooler temperatures (not less than 40º F). Emerging wasps are usually seen in the morning. To maximize pest fighting time, don't delay release after adult wasps emerge. Keep Trichogramma cards in the shade, out of the hot sun.

Packaging tab of a Trichogramma card in a paper wedge cup.


Release as adults


For those who want to consider using loose Trichogramma wasps at a small discount, the advantages are superior percentage emergence and survival in the field. The wasps emerge in two to five days, depending on temperature, which should ideally be 80º to 90º F. Emergence can be delayed by holding parasitized moth eggs at cooler temperatures (not less than 40º F). There could be some loss of emergence or searching ability after cold storage. Emerging wasps are usually seen in the morning, first males sitting quietly, then females and mating activity, then the males die. Don't delay release after adult wasps emerge. Keep Trichogramma in the shade, out of the hot sun.


Loose parasitized eggs can be incubated in a variety of containers (preferably glass or paper over plastic). Jars or vials, bags or cups can be used. Loose eggs are divided into roughly equal amounts among containers. Large containers can be opened at randomly spaced rows or trees releasing more where moth activity has been greater.


Glass Jar Incubation Containers
Any size jar will work from pint to gallon according to convenience and size of release. Use a tight-fitting lid. If using shredded paper or confetti as a vehicle, use a wide mouth jar. Use more jars when you are doing this method the first time so you can get a feel for how the wasps behave. Putting shredded paper, yarn, string or thin strips of cloth in the container makes it easier to lift the live Trichogramma adults to the tree. If you don’t use shredded paper and they do not fly out of the jar easily, wrap the jar in a jar cloth or bag so they will be attracted to the mouth of the jar. The benefit of using a jar is a little more ability to see the wasps and the proportion that remain to be released.


Paper Bag Incubation Containers
Any size paper bag will work from a lunch bag to a grocery bag, but it should not have holes in it. Again, put some material like shredded paper, short pieces of string or other material in the bag. If the bag and other material are white or light colored it is easier to see the moving specks that are the wasps. The benefit of using a paper bag is ease of handling and Trichogramma that is not walking on the paper shreds will be more likely to leave the bag than a clear jar.


Paper Wedge Cup Incubation Containers
“Ajax” paper drinking cups can be used for packaging Trichogramma using the following diagram.

Fold the mouth of the cup closed (folding over twice), and fold back the two corners like dog ears. Remember when doing the release to either open the cups or poke exit holes in it to allow wasps to escape. A dissecting needle or small knifeblade is a good tool for poking holes in the paper. Poking small holes is to prevent ants and earwigs from getting in and eating the parasitized moth eggs before they emerge from the moth egg. Once the Trichogramma adults begin emerging and swarming, cups must be set out. Punctured cups can be broadcast on and around plants or vines, set in branches or stapled to leaves. Any paper container can be used in the same way.

Honey Streak or Paper Gives Wasps an Energy Boost
A source of honey that is dry enough so the wasps cannot get stuck in it helps them do a better job. The simplest method is to use a tool with a sharp point like a dissecting needle to make a very thin streak of honey inside each incubation container. Don’t put too much or more will be likely to get stuck in it. A more complicated method is ‘honey paper’ put in with Trichogramma in jars or cups for dispersal. The wasps can access the honey without getting stuck in it. Mix a couple a drops of honey with a couple drops of water on a sheet of waxed paper. Fold and cut the waxed paper roughly 1/4 inch wide. Separate strips by pressing between thumb and fore finger. Place a pinch of loose Trichogramma or a cardstock tab or piece of a tab of Trichogramma card. This gives emerging wasps energy to go out foraging for moth eggs, they may live up to four times longer and lay more eggs.


More Tips for Releasing Adults
Releasing adults is ideal when you can be ready to release when they are emerging. One limitation is that it is hard to predict how long it will take for all the wasps to emerge. A feature of the paper cup method is that you can leave the paper cup with puncture holes in the field (or stapled to a leaf). They are not vulnerable to predators in the pupa stage while you are waiting for all of the adults to emerge.


If you release from a jar or bag, the majority of wasps will be emerged, swarming and mating. If shredded paper is used, they will be evenly distributed on shreds that can be placed on trees. Otherwise, a a wand of twisted paper can be used to pick them up and wave them into the foliage. Contents of jars or bags can be combined and kept for another 24 hours and released in an area of higher pest pressure. Place Trichogramma card pieces or loose eggs into the container, add strip of honey paper (optional), and close. Hold in a warm place, 70 - 80 degree F, 60% RH, for 1 - 4 days until they are hatching. The males emerge first and wait for the females to emerge later in the day. Wait for the day after first seeing the first wasps. Take the vials out to the field in a cooler with some ice packs - to keep them from overheating. Avoid placing vials directly on the ice - use some crumpled newspaper to separate from the ice. Wasps can get stuck to condensation on the inside of the vials.


In the field, open a vial next to a tree or area of plants. Allow some of the wasps to fly away. Move onto another tree or area. Release more wasps. Use a 1 – 2 foot length of rubber hose to blow the remaining wasps from the vial, or leave the vial in the field for the rest of the wasps to fly out.


Since Trichogramma prefer to attack freshly deposited moth eggs (up to 4 days old), the time to release Trichogramma is when moths are flying and laying eggs. Begin releases as early in the season as field and row crops provide shade for the parasites, e.g. when tomatoes are 12-28 inches high. It is better to start releases early, as Trichogramma populations have the potential to grow geometrically each 7-10 days, and a long headstart on pests is more likely to tip the ecological balance in favor of biological control. A few minor pest situations must be tolerated to obtain a natural enemy complex that controls major pest problems.


Release rates depend on the species and strain and other factors, but some examples are:
Corn 1/10 card/acre 3 tabs/acre 150 mg loose sito/acre
Avocado ½ card/acre 15 tabs/acre 750 mg loose sito/acre
Orchard crops 1 card/acre 30 tabs/acre 1.5 g loose sito/acre

Trichogramma catalog section

Trichogramma bulletin

Trichogramma species