Volatile semiochemicals increase trap catch of Green Lacewings (Neuroptera: Chrysopidae) and Flower Flies (Diptera: Syrphidae) in corn and soybean plots

Authors: Hesler, Louis

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2016
Publication Date: 8/17/2016
Citation: Hesler, L.S. 2016. Volatile semiochemicals increase trap catch of Green Lacewings (Neuroptera: Chrysopidae) and Flower Flies (Diptera: Syrphidae) in corn and soybean plots. Journal of Insect Science. 16(1):77. doi:10.1093/jisesa/iew057.

Interpretive Summary: The interplay between plants and beneficial insects arises largely from chemical cues that plants use as natural attractants. A better understanding of which attractants are the most important may lead to practical means of enhancing the services that beneficial insects provide for plants. This may be especially valuable for agricultural crops, which typically depend upon pollinators to enhance seed set and insect predators to protect against plant pests. This study showed how particular plant-based chemicals were attractive to predatory green lacewings and flower flies based on their increased catch on yellow sticky traps within corn and soybean plots in eastern South Dakota. Green lacewings were attracted to eugenol-baited traps in two initial tests in soybean. Follow-up testing in corn and soybean showed that catch of green lacewings increased when traps were baited with eugenol, either of two chemical analogs known as isoeugenol and methyl eugenol, or 2-phenylethanol. Another structural analog named 4-allylanisole was not attractive to green lacewings. Flower flies were attracted to 2-phenylethanol in initial tests in both corn and soybean. Subsequent testing in soybeans confirmed flower fly attraction to 2-phenylethanol and also to an analog known as 2-phenylacetaldehyde, but not to the analog benzyl amine. A six-week test in soybean found that flower flies were also attracted to traps baited with either eugenol or methyl eugenol. This is the first report of green lacewing attraction to eugenol and isoeugenol and the first report of flower fly attraction to eugenol. These attractants may be used in developing strategies to lure green lacewings, flower flies and other beneficial insects into corn and soybean fields to fight plant pests. The differences in attraction among analogs shows that subtle differences in chemical structure may be important in choosing particular attractants of beneficial insects.

Technical Abstract: Knowledge about beneficial insects’ responsiveness to plant-produced volatiles may improve understanding of insect chemical ecology and lead to practical means of enhancing ecosystem services. This study reports on the attractiveness of various volatile chemicals to green lacewings (Neuroptera: Chrysopidae) and flower flies (Diptera: Syrphidae) as measured by catch on yellow sticky traps within corn and soybean plots. Green lacewings were significantly attracted to eugenol-baited traps in two initial tests in soybean plots. A follow-up test in corn showed that catch of green lacewings was enhanced when traps were baited with eugenol, its structural analog isoeugenol, or 2-phenylethanol; trap catch of green lacewings was greater with these compounds than with the structural analog, 4-alllylanisole. In a follow-up test in soybean, more green lacewings were caught on traps baited with isoeugenol than with 4-allylanisole. Catch did not differ among traps baited with eugenol, isoeugenol, or 2-phenylethanol or among those baited with eugenol, 2-phenylethanol or the ethanol control. In a six-week experiment in soybean, green lacewings were significantly attracted to eugenol-baited traps in five of six weeks but were attracted to traps baited with the structural analog methyl eugenol in only one week. Flower flies were attracted to 2-phenylethanol in initial tests in both corn and soybean plots. Subsequent testing in soybeans with 2-phenylethanol and two structural analogs confirmed flower fly attraction to 2-phenylethanol and also showed attractancy of 2-phenylacetaldehyde but not benzyl amine. An additional six-week test in soybean found that flower flies were also attracted to traps baited with either eugenol or methyl eugenol. This is the first report of green lacewing attraction to eugenol and isoeugenol and first report of flower fly attraction to eugenol. Structure-activity relationships among attractants and practical aspects of using these volatile compounds are discussed.