Introducing beneficial insects to protected cropping systems helps reduce our reliance on pesticide applications and assists with our anti-resistance strategies, however these mini pest controllers are not cheap and, in many cases, they are actually much more expensive than conventional pesticides. Therefore, it is critically important that we maximise their chances of survival and success.
Identifying the features of aphid corpses allows us to monitor the effect of each release of beneficial insects and then adjust further introductions dependent upon results in the field.
Aphidius colemani
The adult female parasitic wasp lay’s her eggs in multiple aphid hosts, the larva then hatches and consumes the aphid from the inside causing the aphids body to swell and harden into a leathery golden-brown shell. Approximately 2 weeks after introduction the emerging adult wasp cut’s a symmetrical round hole at the rear end to escape from the mummified aphid corpse.
The perfect circular “rear hatch” cut by the emerging parasitic wasp
Unfortunately, even the predators sometimes become prey themselves! Hyper-parasites lay their eggs inside aphids which have already been parasitised by Aphidius colemani which then develop and feed on the immature parasitic wasp killing it before it can hatch. This is difficult to identify in the early stages however the shape of the exit hole is a simple sign of who emerged first. The hyper-parasite will leave a jagged edged escape hatch where Aphidius colemani will always cut a perfect circular shaped exit.