Two beneficial Trichogramma wasp species including Trichogramma minutum and Trichogramma pretiosum have potential to use as biological control agents to suppress the populations of grape berry moth, Endopiza viteana. Both of these wasps are known as egg parasitoids because they parasitize the eggs of many Lepidopterous insects including grape berry moth, Endopiza viteana.
What are grape berry moth, Endopiza viteana?
The grape berry moths are scientifically called as Endopiza viteana and they belong to an insect order called Lepidoptera. The grape berry moth occurs naturally on wild grapes in North America i.e. in Canada and eastern parts of the United States. As name implies, these moths are one of the most serious pests of wildly, commercially and home grown grape berries. Only larvae/ caterpillars of this moth feed on florets and berries and adult moths are harmless. Larvae can feed on both small and large fruits. Damaged small fruits turn purple in color and drop off the vine whereas large infested fruits generally rot on the vines. The grape berry moths overwinter as pupae in the cocoons and emerge as adults early in the spring. Adult emergence generally coincides with blooming of grapes. Adults are brown in color with purple color band across the forewings and brown head. Females lay cream colored and circular eggs on different plant parts including twigs. leaves, flowers and small fruits. Eggs hatch into small yellowish creamy colored larvae but it turns green as it grows and at maturity it becomes completely purple in color. Mature larvae are about 9-10 mm long. Generally, first generation larvae of grape berry moth feed on flowers and small berries whereas the second generation larvae feed on mature fruits internally. Small berries infested by first generation moth larvae will drop off the plants but mature grapes infested by second generation larvae are webbed together and rotted eventually in the intact grape bunch.
Biological control of grape berry moth, Endopiza viteana
Chemical pesticides may be effective in controlling grape berry moth, Endopiza viteana but these chemicals may have detrimental effects on human health as well as the environment. Recently, many researchers have investigated use of beneficial insects including Trichogramma minutum and Trichogramma pretiosum wasps as biological control agents to manage the populations of grape berry moth, Endopiza viteana (Nagarkatti et al., 2002; 2003; Seaman et al., 1990) .
What are Trichogramma minutum and Trichogramma pretiosum wasps?
These two beneficial Trichogramma wasp species are tiny insects belong to an insect order called Hymenoptera and recognized as egg paratoids of many Lepidopterous insects including grape berry moth, Endopiza viteana. These two wasps are stingless, about 0.2 to 1.5 mm long and naturally occur in a wide variety of habitats. It has been reported that both Trichogramma minutum and Trichogramma pretiosum wasps in nature can parasitize over 40% eggs of grape berry moth in nature (Dozier et al., 1932; Nagarkatti et al., 2002; 2003; Seaman et al., 1990).
How Trichogramma minutum and Trichogramma pretiosum wasps can kill grape berry moths?
As both Trichogramma minutum and Trichogramma pretiosum wasps are recognized as egg parasitoids, their females using ovipositor, lay their eggs inside the grape berry moth eggs. Inside the grape berry moth eggs, wasp eggs hatch into small larvae that immediately starts feeding on the embryos and kill the developing of grape berry moth larvae also called as caterpillars. While feeding on the host embryos, wasps develop through immature stages and emerge as adults to seek and parasitize new batches of eggs laid by grape berry moths. Thus these wasps can help to suppress the population of grape berry moths and reduce the damage caused by them to grapes.
- Dozier, H.L., L.L. Williams and H.G. Butler, 1932. Life history of grape berry moth in Delaware. Delaware Agricultural Experiment Station Bulletin 176: 147.
- Nagarkatti, S., Muza, A.J., Saunders, M.C. and P.C. Tobin. P.C. 2002. Role of the egg parasitoid Trichogramma minutum in biological control of the grape berry moth, Endopiza viteana. BioControl 47: 373-385.
- Nagarkatti, S., Tobin, P.C., Saunders, M.C. and Muza, A.J. 2003. Release of native Trichogramma minutum to control grape berry moth. Canadian Entomologist 135: 589-598.
- Seaman, A.J., Nyrop, J.E. and Dennehy, T.J.1990. Egg and larval parasitism of the grape berry moth (Lepidoptera: Tortricidae) in three grape habitats in New York. Environmental Entomology 19: 764–770.