|Jandricic, Sarah -|
|Gillespie, David -|
|Sanderson, John -|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2013
Publication Date: February 14, 2013
Citation: Jandricic, S.E., Wraight, S.P., Gillespie, D.R., Sanderson, J.P. 2013. Oviposition behavior of the biological control agent Aphidoletes aphidimyza (Diptera: Cecidomyiidae) in environments with multiple pest aphid species (Hemiptera: Aphididae). Biological Control. 65:235-245. Interpretive Summary: The green peach aphid and foxglove aphid are two of the most important greenhouse pests in the U.S., U.K., and Canada and can co-infest crops in the same greenhouse. These aphids exhibit many biological and behavioral differences, including preference for different parts of their host plants: foxglove aphids tend to feed on older, bottom leaves of pre-flowering plants, whereas green peach aphids prefer new growth in the tops of plants. The effects of these differences on efficacy of many currently used biocontrol agents is not known; however, if a biocontrol agent were to show a preference for one aphid over the other, then releases of that agent for biological control of mixed aphid infestations could result in unbalanced attack and potentially inadequate control of the less attractive pest. In a series of small-scale tests, we investigated the capacity of the commercially available predatory midge Aphidoletes aphidimyza to seek out and attack foxglove aphids in research greenhouses co-infested with green peach aphid. Experiments revealed no significant preference for one aphid prey over the other when the two aphids were confined to the same location on potted pansy plants. However, when the aphids were allowed to naturally distribute themselves, Aphidoletes adults deposited much larger numbers of eggs in colonies of green peach aphids established on the upper leaves and growing points of plants than in foxglove aphid colonies on bottom leaves. These findings underscore a need for further testing of this predator under simulated and actual commercial production conditions to assess its potential to control simultaneous outbreaks of multiple aphid pests.
Technical Abstract: Natural enemies are constantly faced with oviposition decisions that have potential fitness consequences. We investigated the oviposition behavior of the aphidophagous midge Aphidoletes aphidimyza (Diptera: Cecidomyiidae) when faced with multiple prey choices, i.e. plants infested with Myzus persicae or Aulacorthum solani (Hemiptera: Aphididae). When location of aphid patches on plants was controlled for, aphid density was a significant factor in A. aphidimyza oviposition, but species was not. When location was uncontrolled, differences in within-plant distribution patterns of the two aphid species were observed. Along with aphid density, species and location of aphid patches on plants became significant (as were 2 and 3-way interactions with location). Myzus persicae aggregated on plant meristems (67% of the population) and these prey patches received the largest number of A. aphidimyza eggs. Aulacorthum solani were mainly found distributed among lower leaves (55%); plants infested with this aphid received significantly fewer eggs. Giving A. aphidimyza a choice of 2 patch locations as oviposition sites, aphid species was again unimportant, and a greater correlation with aphid density was seen with aphid colonies located on younger plant tissue vs. old. These results suggest that, for A. aphidimyza, perceived quality of an aphid patch as an oviposition site is influenced more by density and location of the aphid patch on the plant than by the species of aphid within the patch. Given that aphid species can have differing within-plant distributions, this behavior could have important implications for the efficacy of A. aphidimyza as a biocontrol agent for aphids in multi-species environments.