Investigations Of The Biology Of The Pest Aphid Aulacorthum Solani (Kaltenbach) (Hemiptera: Aphididae) And Of Biological Control Agents For Control Of Multi-Species Aphid Outbreaks In Greenhouse Floriculture Crops.
Foxglove aphid, Aulacorthum solani (Kaltenbach), has recently become a significant pest of greenhouse crops in the north eastern U.S., Canada, and the U.K. Given its previous status as an occasional pest, little was known about its biology or ecology. Using a North American population, development time and life table statistics of A. solani were investigated at 6 temperatures. Aulacorthum solani developed fastest (6.9 ± 0.29 d) and had the highest intrinsic rate of increase (rm = 0.25) at 25 °C; limited development was seen at higher temperatures (rm = -0.24 at 30 °C). A study of 10 different greenhouse crops showed that these aphids generally distribute to bottom leaves of vegetative plants, but move upwards when plants are reproductive. Biological control of A. solani using the generalist aphid predator Aphidoletes aphidimyza (Rondani) was assessed in a series of greenhouse experiments. Here, the green peach aphid, Myzus persicae (Sulzer), was also included because aphid pests can co-occur. Experiments showed that A. aphidimyza perceives aphid colonies located on new growth of plants (meristems or top leaves) to be of higher value as oviposition sites compared to other plant locations. Aulacorthum solani-infested plants, with aphids primarily present on lower leaves or flowers, received fewer eggs than M. persicae-infested plants. In trials using a single innundative release of the predator, this translated to more variable control of A. solani compared to M. persicae (12-80% vs. 78-95%, respectively; tested across several stages of plant growth). This is likely partially attributable to apparent competition, since control of A. solani was significantly improved in the absence of alternate prey. Entomopathogenic fungi were assessed as another biocontrol option against aphids, including the melon aphid, Aphis gossypii Glover. Novel isolates of fungi originally collected from aphid hosts were sought to potentially increase pathogenicity. However, no isolate tested, commercial or novel, resulted in acceptable mortality of 1st instar aphid nymphs, with all LC50 values >700 conidia/mm2 under ideal lab conditions. Control options for A. solani and multi-species aphid infestations are discussed in light of the results presented in this thesis.
Aulacorthum solani; Aphidoletes aphidimyza; Biological control
Sanderson, John Philip
Thaler, Jennifer S.; Wraight, Stephen Paul; Nyrop, Jan Peter
Ph. D., Entomology
Doctor of Philosophy
dissertation or thesis