Natural enemies

IPM components

Trichogramma

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

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. These are mass produced and sold to farmers as small cards, which contain hundreds of parasitized eggs.

This Korean stamp shows a Trichogramma wasp.
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 Trichogramma. Eggs of Rice moth (Corcyra sp.) are used as a host. These eggs are glued on small cards and then female Trichogramma 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.

A signboard at the Trichogramma rearing facility of DOAE's bio-center in Chiang Mai.
A signboard at the Trichogramma rearing facility of DOAE's bio-center in Chiang Mai.

 

Cards with parasitized eggs in a Trichogramma rearing facility.
Cards with parasitized eggs in a Trichogramma rearing facility.

Tricho cards are placed in a sugarcane field. A piece of paper protects the parasitized eggs from direct sunlight.
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.