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Title: Field responses of predaceous arthropods to methyl salicylate: a meta-analysis and case study in cranberries

Author
item RODRIGUEZ-SAONA, CESAR - Rutgers University
item KAPLAN, IAN - Purdue University
item BRAASCH, JOSEPH - Purdue University
item CHINNASAMY, DURAIRAJ - Tamil Nadu Agricultural University
item Williams, Livy

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2011
Publication Date: 6/7/2011
Citation: Rodriguez-Saona, C., Kaplan, I., Braasch, J., Chinnasamy, D., Williams Iii, L.H. 2011. Field responses of predaceous arthropods to methyl salicylate: a meta-analysis and case study in cranberries. Biological Control. 59: 294-303.

Interpretive Summary: Plants damaged by insect pests produce odors that function as ‘distress signals’ to attract beneficial insects that attack the pests. However, the odors responsible for this phenomenon, and the magnitude and type of effect, may vary with the type of plant, pest, and other conditions. Thus, understanding the interactions between pests, plant distress signals, and attraction of beneficial insects is a challenge, but one that has important implications for pest control. We conducted a statistical analysis of previously published studies to determine the magnitude of beneficial insect response to a relatively common plant odor (methyl salicylate) that has shown potential in attracting beneficial insects to crop fields. The results of this analysis documented significant attraction and the magnitude of this attraction did not differ between different types of beneficial insects. We also conducted field experiments to evaluate whether or not methyl salicylate baited traps were attractive to beneficial insects in cranberry bogs. Our results showed that baited traps were more attractive to beneficial insects and that some types of beneficial insects were strongly attracted to point sources of the odor. We also documented the duration of effectiveness of commercial methyl salicylate lures under field conditions. Our findings indicate that beneficial insects are broadly attracted to methyl salicylate in agricultural fields, including in cranberries; yet, whether this behavior can be manipulated to improve biological control needs further investigation.

Technical Abstract: Methyl salicylate (MeSA) is an herbivore-induced plant volatile (HIPV) that has shown potential in attracting natural enemies. Here, we conducted a meta-analysis to evaluate the magnitude of natural enemy response to MeSA in the field, and tested its attractiveness to insect predators in commercial cranberry bogs. Eighteen experiments from 14 publications were used in the meta-analysis, resulting in 91 total observations. Of these, 41 documented significant attraction and the magnitude of this attraction response was not significantly different across predator and parasitoid taxa. Insect predators were monitored in cranberries using MeSA (Predalure)-baited and unbaited yellow sticky traps. MeSA-baited traps caught greater numbers of adult hoverfly, Toxomerus marginatus (Diptera: Syrphidae), lady beetles (in particular Coccinella septempunctata) (Coleoptera: Coccinellidae), and green lacewings (Neuroptera: Chrysopidae) compared with unbaited traps. In another field experiment, predator abundance was monitored using traps placed near the MeSA lure (0 m), as well as at 2.5, 5, and 10 m away from the lure. Adult T. marginatus, the dominant predator species, showed a clear attraction to the point source but not to the other distances. In complementary studies we showed that MeSA emissions from Predalures dropped quickly soon after deployment in the field but remained relatively high for over four weeks; flowering, but not vegetative, vines were a primary source of MeSA in cranberries; and, exposure to Predalures triggered elevated MeSA emissions from vegetative vines. In conclusion, we find strong evidence that insect predators are broadly attracted to MeSA in agricultural fields, including in cranberries; yet, whether this behavior can be manipulated to improve biological control needs further investigation.