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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Emerging Pests and Pathogens Research » Research » Publications at this Location » Publication #298392
Title: Biological control outcomes using the aphidophagous predator Aphidoletes aphidimyza (Diptera: Cecidomyiidae) under multi-prey conditions: Effect of crop stage, within-plant aphid distribution and apparent competition

Author
item JANDRICIC, SARAH - Cornell University
item Wraight, Stephen
item GILLESPIE, DAVID - Agriculture And Agri-Food Canada
item SANDERSON, JOHN - Cornell University

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2016
Publication Date: 12/14/2016
Citation: Jandricic, S.E., Wraight, S.P., Gillespie, D.R., Sanderson, J.P. 2016. Biological control outcomes using the aphidophagous predator Aphidoletes aphidimyza (Diptera: Cecidomyiidae) under multi-prey conditions: Effect of crop stage, within-plant aphid distribution and apparent competition. Insects. 7(4):15.

Interpretive Summary: The green peach aphid (GPA) and foxglove aphid (FGA) are two of the most important greenhouse pests in North America and can co-infest crops in the same greenhouse. These aphids exhibit many biological and behavioral differences, including preferences for different feeding sites on their host plants; FGA tends to feed on bottom leaves of pre-flowering plants, but prefers top leaves or buds/flowers of flowering plants. GPA prefers new growth in the tops of plants regardless of plant age. Previous short-term tests showed that the aphid-predatory midge Aphidoletes aphidimyza prefers to lay its eggs among aphids on new growth of plants, leading to unbalanced attacks against GPA and FGA in mixed infestations. Here, we conducted longer-term tests to assess the efficacy of this biocontrol agent against mixed aphid infestations and during different crop stages. When both GPA and FGA were present, control of GPA was consistent at all stages of plant growth. In contrast, control of FGA was inconsistent in the presence of GPA. Best control of FGA was seen when plants were in the budding stage, apparently due to migration of this aphid from cryptic sites on the undersides of lower leaves to buds and other exposed sites in the tops of plants. These tests confirmed also that control of FGA by A. aphidimyza was significantly greater in the absence of GPA. This study illustrates how variations in distribution of aphids on their host plants can substantially affect the efficacy of a biocontrol agent and underscores the need for growers to take this into consideration in planning their pest scouting and control programs, especially in systems where pest complexes are common.

Technical Abstract: Previous short-term trials with the aphidophagous midge Aphidoletes aphidimyza (Diptera: Cecidomyiidae) indicated that this natural enemy prefers to oviposit on aphids colonizing new growth of plants, leading to differential attacks against aphid species with different within-plant feeding-site preferences. Here, we used longer-term greenhouse trials to determine biological control outcomes using A. aphidimyza under multi-prey conditions and during different crop stages. When both Myzus persicae and Aulacorthum solani were present, control of M. persicae by A. aphidimyza was consistent at all stages of plant growth. In contrast, control of A. solani was inconsistent in the presence of M. persicae. Best control of this aphid was consistently seen when plants were in the budding stage, which was the apparent result of a large proportion of the aphid population moving from cryptic sites on the undersides of leaves at the bottoms of plants to the more exposed growing points. Greenhouse trials provided the first evidence that late-instar larvae of A. aphidimyza are able to move down compact plants to aphid colonies present on lower leaves when food becomes scarce at their natal location, and that control of A. solani by A. aphidimyza was significantly greater in the absence of M. pericae than in its presence. This study not only illustrates how variation in within-plant distribution of aphid pests can affect the level of biological control, but also that apparent competition between prey species can negatively influence biological control programs in systems where pest complexes are common.