Identification of conditions for successful aphid control by ladybirds in greenhouses

Authors: Riddick, Eric

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2017
Publication Date: 3/28/2017
Publication URL: http://handle.nal.usda.gov/10113/5661759
Citation: Riddick, E.W. 2017. Identification of conditions for successful aphid control by ladybirds in greenhouses. Insects. 8(38):1-17.

Interpretive Summary: Aphids and other small insects continue to cause damage to crop plants grown in greenhouses and glasshouses throughout the world. Aphids also transmit devastating plant diseases between plants. Methods of managing aphids on crop plants without using pesticides has been challenging. One strategy to manage aphids in greenhouses could involve using ladybird beetles (i.e., lady beetles), which have a rich history of suppressing aphid populations in agricultural fields. The utilization of ladybird beetles to help manage aphids in greenhouses was reviewed and strategies to increase their effectiveness were highlighted. Strategic use of ladybird beetles must incorporate knowledge of (1) crop plant defenses against aphid attack, and whether these defenses have detrimental effects on ladybird performance, (2) the most effective ladybird life stage (eggs, larvae, or adults), (3) aphid population size at the time ladybirds are released, and (4) the presence of ants, which could interfere with ladybird performance. In addition, the utilization of ladybirds along with aphid parasites (parasitic wasps) could have a net positive effect on the health and survival of crop plants in greenhouses. Strategic use of ladybird species to manage aphid populations in greenhouses is encouraged.

Technical Abstract: As part of my research on the mass production and augmentative release of ladybirds, I reviewed the primary research literature to test the prediction that ladybirds are effective aphid predators in greenhouses. Aphid population reduction exceeded 50% in most studies and ladybird release rates usually did not correlate with aphid reduction. The ratio of aphid reduction/release rate was slightly less for larvae than adults in some studies, suggesting that larvae were less effective (than adults) in suppressing aphids. Some adult releases were inside cages, thereby, limiting adult dispersion from plants. Overall, the ratio of aphid reduction/release rate was greatest for ladybird adults of the normal strain (several species combined), but least for adults of a flightless H. axyridis strain. The combined action of ladybirds and hymenopteran parasitoids could have a net positive effect on aphid population suppression and, consequently, on host (crop) plants. But ladybird encounters with aphid-tending or foraging ants must be reduced. Deploying ladybirds to help manage aphids in greenhouses and similar protective structures is encouraged.