Preliminary studies of positive and negative effects of brown lacewings on the control of foxglove aphids by parasitoids in sweet pepper

ROCCA M.; MESSELINK G.

Pucón

Simposio; 4th International Symposium on Biological Control of Arthropods; 2013

IOBC

The use of natural enemy complexes in agricultural systems has been a controversial subject in the management and biological control of pests. Understanding how interactions among natural enemies affect herbivore populations is crucial for biological pest control. Natural enemies can act by different positive and negative mechanism; examples of these are predator facilitation and intraguild predation (IGP). Many aphids drop off the plant as defensive tactic against predators and parasitoids. But, if aphids drop off the plant after being parasitized this may also facilitate IGP, and the interaction could be antagonistic. We investigated two mechanism that contradict each other, dropping behaviour (+) and IGP (-), between two natural enemies used to control Aulacorthum solani (Hemiptera: Aphididae) on sweet pepper in greenhouses, Aphidius ervi (Hymenoptera: Braconidae) and Micromus variegatus (Neuroptera: Hemerobiidae). Two experiments were conducted, one to see the effects of both natural enemies on the dropping behaviour of A. solani, and another to evaluate the preference of the lacewing for unparasitized versus young parasitized aphids and mummies (IGP). The dropping behaviour experiment shows that in presence of the parasitoid the proportion of dropping aphids was higher. This can be explained by the spatial niche partitioning and the foraging rates and time required to find, manipulate and consume the prey. The IGP experiment shows that adult lacewings had a small preference for young parasitized aphids over unparasitized aphids, but they preferred unparasitized aphids more than mummies. So, it could be that the IGP was not strong enough to disrupt the suppression of aphids, and both species act additively. The challenge now, based on these studies, is to study the combined effects of A. ervi and M. variegatus on foxglove aphids in greenhouse conditions to observe the interaction results on the control of A. solani. The results of this study show the importance of understanding the various types of interactions than can occur between predators and parasitoids when assessing their value for biological control, especially in greenhouse systems where biodiversity can be managed.