Many insect herbivores rely on symbiotic bacteria for their survival. These ‘hidden players’ residing in insect tissues can affect fitness of the insect host. For example, some insect species show increased resistance to natural enemies when certain ‘protective’ symbiotic bacteria are present, which could make it more difficult to control pest infestations.
Under favourable conditions, parasitoid wasps can be effective natural enemies of aphids and they are frequently deployed to control infestations in glasshouses and polytunnels. Parasitoid wasps insert their eggs into the aphid body, from which a larva emerges that consumes and eventually kills the aphid. However, in the presence of certain protective symbionts, the parasitoid egg fails to develop.