Louis S. Hesler

Direct effects of soybean varietal selection and Aphis glycines-resistant soybeans on natural enemies

The direct effects of three soybean parentages, each represented by an Aphis glycines-resistant and susceptible isoline, on the fitness and performance of two key predators (Orius insidiosus and Harmonia axyridis) were evaluated in the laboratory. Predators were reared from hatch through adulthood in Petri dishes with cut trifoliolate leaves of the designated soybean variety, using eggs of Ephestia kuehniella as surrogate prey to eliminate prey-mediated effects of the host plant. Preimaginal survival and development, sex ratio, adult longevity, fecundity, and size were compared among treatments and a no-plant control. An additional experiment compared life-history parameters of predators caged with soybean versus Ipomoea hederacea (ivyleaf morning glory). Aphid resistance reduced the adult longevity of H. axyridis, but O. insidiosus was unaffected by resistance traits. However, adult O. insidiosus lived longer on soybeans with Group C base genetics than the other soybean varieties. Other parameters were not affected by soybean base genetics or resistance, but both predators generally performed worse on soybean than on I. hederacea or no-plant controls. The results suggest that soybean varietal selection, particularly with respect to A. glycines-resistance, may directly affect biological control agents. Also, implications of the generally poor suitability of soybean for natural enemies are discussed within the context of current crop production practices.

Volatile Semiochemicals Increase Trap Catch of Green Lacewings (Neuroptera: Chrysopidae) and Flower Flies (Diptera: Syrphidae) in Corn and Soybean Plots.

This study reports on the attractiveness of volatile chemicals to green lacewings (Neuroptera: Chrysopidae) and flower flies (Diptera: Syrphidae) as measured by catch on yellow sticky traps within corn [Zea mays L. (Cyperales: Poaceae)] and soybean [Glycine max (L.) Merr. (Fabales: Fabaceae)] plots. Green lacewings were attracted to eugenol-baited traps in two tests in soybean plots. Follow-up testing 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 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 6-wk experiment in soybean, green lacewings were attracted to eugenol-baited traps in 5 of 6 wks but to traps baited with structural analog methyl eugenol in only 1 wk. Flower flies were attracted to 2-phenylethanol in initial tests in corn and soybean plots. Subsequent testing in soybeans with 2-phenylethanol and structural analogs confirmed attraction to 2-phenylethanol and also showed attractancy of 2-phenylacetaldehyde but not benzylamine. A 6-wk 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 their use are discussed.

Lady Beetle Assemblages (Coleoptera: Coccinellidae) in Western South Dakota and Western Nebraska and Detection of Reproducing Populations of Coccinella novemnotata

ABSTRACT n Recent detections of adults of three previously common, native species of lady beetles [Coccinella novemnotata Herbst, Coccinella transversoguttata richardsoni Brown, and Adalia bipunctata (L.); Coleoptera: Coccinellidae] during surveys at several sites in western South Dakota and western Nebraska provided impetus for additional sampling of lady beetles in that region. The current study systematically sampled for lady beetles among three dominant habitats in the region in 2010 and 2011. Four techniques (sucrose-baited and nonbaited yellow sticky traps, sweepnetting, visual searches) sampled 4,036 adult and 830 larval coccinellids comprising 10 species. Coccinella septempunctata L., Hippodamia convergens Guerin-Meneville, Hippodamia parenthesis (Say), and Brachiacantha albifrons (Say) were the most common species. C. novemnotata ranked fifth in abundance, with 94 sampled in small grains, 20 in alfalfa, and 5 in grassland pasture; 58 larval C. novemnotata were sampled primarily in small-grain fields. Abundance of C. novemnotata negatively correlated with proportion of vegetative cover in fields, whereas this characteristic did not correlate with abundances of H. convergens, H. parenthesis, and C. septempunctata. Abundance of these three species negatively correlated with vegetative species richness and diversity in fields, whereas C. novemnotata abundance was not related to these indices. Fourteen C. transversoguttata richardsoni, 30 C. novemnotata, and several other coccinellids were observed on roadside vegetation near sample fields. A. bipunctata was not sampled in this study. Results suggest that sparsely vegetated small-grain fields may favor reproducing populations of C. novemnotata in relatively arid areas of the north central United States.

Genome-Wide Association Mapping of Host-Plant Resistance to Soybean Aphid

Soybean aphid host‐plant resistance is needed to reduce damage from soybean aphid. Genome‐wide association mapping is effective for finding insect resistance loci. We found single nucleotide polymorphisms associated with soybean aphid resistance for multiple aphid biotypes.

Laboratory Evaluation of Soybean Plant Introductions for Resistance to Aphis glycines (Hemiptera: Aphididae)1

Abstractu2003 The soybean aphid (SA), Aphis glycines Matsumura, is a major pest of soybean in the north-central United States and south-central Canada. It is controlled primarily with insecticides, but the development of aphid-resistant soybean cultivars may provide an alternative management tactic. The viability of this management tactic depends on a diverse set of resistance sources in order to counter various resistance-breaking biotypes of SA, and the identification of new sources of resistance necessitates additional testing of soybean germplasm. The current study used no-choice tests to identify SA resistance in seven early maturing (maturity group I) soybean plant introductions (PIs) that had been advanced from free-choice screening trials. The tests showed PI 437353 and PI 612759 C had an intermediate level of resistance against avirulent SA, whereas PI 437282, PI 437658, PI 437733, PI 548417, and PI 548530 exhibited no significant resistance. Additional research is needed to determine if the source of resistance in PI 437353 and PI 612759 C is due to novel resistant genes, which would help diversify resistance to SA in soybean. Screening and follow-up tests of additional soybean germplasm is warranted in order to ensure the development of durable, SA-resistant cultivars.