Selection for zoophagy influences biocontrol efficacy and fruit damage by Dicyphus hesperus in greenhouses

Abstract

The zoophytophagous predator Dicyphus hesperus Knight (Hemiptera: Miridae) is effective in the biological control of whiteflies in greenhouses, but it can also cause damage to fruits and plants. Artificial selection on foraging behavior allows the development of more zoophagous lines that have the potential to be both more effective and less likely to cause damage. Moreover, highly zoophagous lines could affect other biological control agents through increased intraguild predation or competition. This study tests the biological control efficacy against tobacco whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and damage by highly and lowly zoophagous lines of D. hesperus in tomato greenhouses. The effect of these lines on Encarsia formosa Gahan (Hymenoptera: Aphelinidae) parasitoid wasp populations was also tested. In cage tests, we introduced D. hesperus from lowly or highly zoophagous and non-selected lines. In half of the cage, E. formosa was introduced. The ability of predators and parasitoids to reduce B. tabaci populations was monitored for 12 weeks. Tomatoes produced were harvested and graded according to damage by D. hesperus. Highly zoophagous lines had a rapid and lasting impact on pest populations. Lowly zoophagous lines take longer to achieve the same level of pest control as highly zoophagous lines. Introductions of E. formosa also reduce populations, but without interacting with D. hesperus. Dicyphus hesperus did not affect E. formosa abundance. Lowly zoophagous lines generated higher proportions of damage. The results show that artificial selection based on zoophagy produces more efficient and less damaging lines in the greenhouse tomato crop. Over time, lines with low zoophagy compensated for low individual efficiency by increasing their numbers. Highly zoophagous lines are compatible with parasitoid wasps, which were little affected by D. hesperus.