A nematode, fungus, and aphid interact via a shared host plant: implications for soybean management

Abstract

Soybean, Glycine max (L.) Merrill (Fabaceae), is an introduced crop to America and initially benefited from a small number of pests threatening its production. Since its rapid expansion in production beginning in the 1930s, several pests have been introduced from the native range of soybean. Our knowledge of how these pests interact and the implications for management is limited. We examined how three common economic soybean pests, the nematode Heterodera glycines Ichinohe (Nematoda: Heteroderidae), the fungus Cadophora gregata Harrington & McNew (Incertae sedis), and the aphid Aphis glycines Matsumura (Hemiptera: Aphididae), interact on soybean cyst nematode‐susceptible (SCN‐S) and soybean cyst nematode‐resistant cultivars carrying the PI 88788 resistance source (SCN‐R). From 2008 to 2010, six soybean cultivars were infested with either a single pest or all three pests in combination in a micro‐plot field experiment. Pest performance was measured in a ‘single pest’ treatment and compared with pest performance in the ‘multiple pest’ treatment, allowing us to measure the impact of SCN resistance and the presence of other soybean pests on each pest’s performance. Performance of H. glycines (80% reduction in reproduction) and A. glycines (19.8% reduction in plant exposure) was reduced on SCN‐R cultivars. Regardless of cultivar, the presence of multiple pests significantly decreased the performance of A. glycines, but significantly increased H. glycines performance. The presence of multiple pests decreased the performance of C. gregata on SCN‐S soybean cultivars (20.6% reduction in disease rating).

Soybean Aphid (Aphididae: Hemiptera) Population Growth as Affected by Host Plant Resistance and an Insecticidal Seed Treatment

“…Five, mixed-age apterous aphids were manually transferred with a Þne camel hairbrush (Winsor & Newton, Piscataway, NJ) to the underside of the uppermost fully expanded trifoliate (McCarville et al 2012a). Aphid populations inside cages were allowed to increase for 9 Ð12 d with populations assessed every 3Ð 4 d. Aphid populations were assessed by opening nets and counting all aphids (both nymphs and adults) on each caged plant.…”

Heterodera schachtii Nematodes Interfere with Aphid-Plant Relations on Brassica oleracea

“…There are few studies on Heterodera -aphid interactions, mostly done with soybean. In those studies, the presence of aphids and nematodes has additive effects on soybean yield (Hong et al 2010, 2011; McCarville et al 2012). Alate aphids preferred plants without nematodes over nematode-infested plants (Hong et al 2010), but a mechanistic explanation is lacking.…”

Performance and prospects of Rag genes for management of soybean aphid

“…Although individual soybean cultivars with Rag1 or Rag2 alone may harbor low population density of soybean aphid that occasionally rises to economically relevant levels, at least two factors favor the adoption of aphid‐resistant soybeans as a proactive means of managing soybean aphid. First, the premium for aphid‐resistant soybean lines has been lower than the cost of foliar insecticides (McCarville et al., ,b). In addition, a large proportion of soybean fields in northern production regions are scouted for soybean aphid (Hodgson et al., ).…”