Estimating ladybird predation of aphids in the presence of foraging ants in lab bioassays

Authors: Riddick, Eric; Wu, Zhixin; Chen, Jian

Submitted to: Entomological Society of America, Southwestern and Southeastern Branch
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Foraging or tending ants often disrupt ladybird beetle predation of aphids on crop plants. In this study, we assessed the foraging behavior of the red imported fire ant (Solenopsis invicta) and tested the hypothesis that foraging ants disrupt ladybird predation. We setup experiments in the laboratory using potted barley plants, the bird cherry oat aphid (Rhopalosiphum padi), ladybird beetle (Coleomegilla maculata) larvae and worker fire ants, foraging freely between an artificial nest and aphid-infested or un-infested plants. The number of ants migrating across a "bridge" from nest to barley plants was determined over time. The number of ladybird larvae eaten by fire ants over time was determined and ladybird predation of aphids estimated. The results indicated that fire ants moved from nest to potted barley plants, then investigated the plants and aggregated at the substrate-root interface of un-infested plants. Fire ants were attracted to aphid honeydew on barley leaves and never attacked aphids. Ladybird larvae were readily killed by fire ants. Ladybird predation of aphids on barley plants was less than 5% in the presence of fire ants. This study suggests that C. maculata predation of aphids (on crop plants) will not be possible when fire ants are foraging in the vicinity or tending aphids. Attempts to curb fire ant aggression against defenseless ladybird beetle larvae (and perhaps adults) must be sought.