The ichneumonid parasitic wasp Lathrolestes ensator is an important natural enemy of apple sawfly. The parasite often regulates the pest on unsprayed garden trees where almost cyclical flare-ups of the sawfly are controlled by attacks of the parasite in subsequent years.
- The parasite only attacks late first and second instar sawfly larvae.
- The comma-shaped, black eggs of the parasite can be seen through the skin of the sawfly larva. However, the parasite egg does not hatch until after the sawfly larva has entered the soil to form a cocoon.
- Feeding and development of the sawfly larva continues normally until that time.
- The parasite has only a narrow window of opportunity to parasitise its host and unfavourable weather conditions at this time greatly limit its effectiveness.
Another parasitic wasp, Aptesis nigrocincta, is an important parasite of larvae and pupae in the soil.
Ground beetles
It is probable that larvae moving over the surface and into the soil are vulnerable to attack by predatory ground beetles, especially larger species. However, whether or not ground beetles are able to locate larvae in cocoons deep in the soil is not known.