Trichogramma – Egg parasitoid

Trichogramma
Trichogramma wasps are very tiny insects, usually smaller than the eggs of butterflies or moths in which they lay their eggs.

The name Trichogramma refers to a number of tiny wasps belonging to the family Trichogrammatidae. They are stout-bodied, minute wasps, which can hardly be seen without a hand lens or microscope. Trichogramma is an important bio-control agent as they are egg parasitoids, mainly of Lepidopteran eggs. Up to three wasp larvae may develop in each Lepidopteran egg. Most trichogrammatid species will attack a range of host species. When a lepidopteran egg is parasitized the eggs turn black as the parasitoid develops inside. From these darkened eggs the adult wasps will eventually emerge.

Egg parasitoid species of the genus Trichogramma have been studied and used in agriculture for a long time. For example sugarcane stalkborers have been controlled for the last 40 years by using Trichogramma egg parasitoids. The parasitoids are mass produced and sold to farmers as small cards (Tricho cards), which contain hundreds of parasitized eggs.

Trichogramma stamp
A stamp showing an adult Trichogramma wasp.

In Thailand, the bio-centers of the Department of Agricultural Extension (DOAE) have set up mass rearing units to produce “Tricho cards”. Eggs of Rice moth (Corcyra sp.) are used as a host. These eggs are glued on small cards and then female parasitoid wasps will parasitize these eggs. These Tricho cards then contain hundreds of parasitized eggs. Cards can be temporary stored in refrigerators before taking them to the farms.

Bio-control signboard
A signboard at the rearing facility of DOAE’s bio-center in Chiang Mai.
Tricho cards
Cards with parasitized eggs in a Trichogramma rearing facility
Trichogramma release
Tricho cards are placed in a sugarcane field. A piece of paper protects the parasitized eggs from direct sunlight. The emerging adult wasps will disperse in the field and parasitize the eggs of sugarcane borers.