Trichogramma evanescens is a very small wasp, barely visible to the naked eye. It has been used for some years now for the control of European stem borer in corn and for caterpillar control in cotton. Over the past few years there have also been successes with the use of this parasite in greenhouses. Trichogramma lays its eggs inside the eggs of moths preventing the moth egg from hatching into a caterpillar. This prevents the damage caused by the feeding caterpillars, and also breaks the life cycle of the pest, effectively preventing the pest from reproducing.

In some species of moth up to 5 parasitic eggs may be laid in each moth egg depending on the size of the moth egg. As the parasite develops within the egg, it turns black, and after about 10 days, an adult Trichogramma emerges. Under laboratory conditions at 23°C, a female Trichogramma parasitizes an average of 60 eggs in 7 days.

Trichogramma is active above 15°C, with an optimum temperature range of 23-25°C with 75% humidity. At higher temperatures activity declines and at 32°C the wasp is no longer effective. Adult Trichogramma can live for up to 14 days after emergence.

Although Trichogramma is minute, it can search for moth eggs over considerable distances. In these crops parasites from a single release site will effectively search an area of 100 m², and in low crops this may be extended up to 800 m². Moths which lay their eggs in clusters are more easily controlled as less time is spent by the parasites in searching.

Trichogramma is supplied in capsules each containing 500 pupae. When properly kept in cold storage the pupae will keep for a long time, but once in the warmth of the greenhouse they hatch within a week. The newly emerged adult parasites leave the transport capsules through small holes. The transport capsules also act as an effective barrier to ants and other predators which would otherwise feed on the parasitised moth eggs.

Trichogramma attacks the eggs of a wide range of moth pests including Turkey moth (Chrysodeixis chalcites), tomato moth (Lacanobia oleracea), cabbage moth (Mamestra brassicae)and silver y moth (Autographa gamma). In order to quickly obtain adequate control, it is important to introduce sufficient parasites.

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