|WOODS, JOANNA - Oregon State University|
|JAMES, D - Washington State University|
|Gent, David - Dave|
Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2011
Publication Date: 10/22/2011
Citation: Woods, J.L., James, D.G., Lee, J.C., Gent, D.H. 2011. Evaluation of airborne methyl salicylate for improved conservation biological control of two-spotted spider mite and hop aphid in Oregon hop yards. Experimental and Applied Acarology. 55(4):401-416.
Interpretive Summary: Spider mites are important pests are numerous horticultural and agronomic crops. Conservation of natural enemies of spider mites can provide substantial control of these pests, but often sufficient numbers of natural enemies are not present at densities needed to prevent crop outbreaks from causing crop. In this study, we evaluated deployment of a volatile compound (methyl salicylate) that is attractive to natural enemies of spider mites and hop aphid as a means to enhance biological control. Across both years, there was a trend for reduced (40 to 91%) mean seasonal numbers of spider mites in five of the six farms where studies were conducted. Mite eating ladybeetles, key spider mite predators, tended to be more numerous in the plots baited with methyl salicylate. Variability among farms in suppression of spider mites and attraction of natural enemies suggests that the use of methyl salicylate to enhance biological control of spider mites in commercial hop yards may be influenced by site-specific factors on each farm or seasonal effects.
Technical Abstract: The use of synthetic herbivore-induced plant volatiles (HIPV) to attract natural enemies has received interest as a tool to enhance conservation biological control (CBC). Methyl salicylate (MeSA) is a HIPV that is attractive to several key predators of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and hop aphid, Phorodon humuli (Schrank) (Homoptera: Aphididae). A two-year study was conducted to evaluate the use of MeSA in hop yards in Oregon. Slow-release MeSA dispensers were stapled to supporting poles in 0.5 ha plots and these plots were compared to a paired non-treated plot on each of three farms in 2008 and 2009. Across both years, there was a trend for reduced (40 to 91%) mean seasonal numbers of T. urticae in five of the six MeSA-baited plots. Stethorus spp., key spider mite predators, tended to be more numerous in MeSA-baited plots compared to control plots on a given farm. However, mean seasonal densities of hop aphid and other natural enemies (e.g., Orius spp., Anystis spp., etc.) were similar between MeSA-treated and control plots. Variability among farms in suppression of two-spotted spider mites and attraction of Stethorus spp. suggests that the use of MeSA to enhance CBC of spider mites in commercial hop yards may be influenced by site-specific factors related to the agroecology of individual farms or seasonal effects. The current study also suggests that CBC of hop aphid with MeSA in this environment may be unsatisfactory.