R. L. Cooper

Interaction of planting times following the incorporation of a living, green cover crop and control measures on seedcorn maggot populations in soybean

Abstract The impact of delaying soybean [ Glycine max (L.) Merr.] planting following the incorporation of a living, green cover crop and using various insecticide management practices on seedcorn maggot [ Delia platura (Meigen)] populations was evaluated. Phorate soil insecticide in a 15.8 cm band and Agrox D-L Plus seed treatment [a mixture of diazinon (0.33% w/w), lindane (15.0% w/w), and captan (14.67% w/w) were applied at planting immediately after, and 1.5 or 3 weeks after, cover crop incorporation that occurred in early May. Seedcorn maggots were sampled with adult emergence traps, and subsequent soybean injury to plumules was estimated. The number of days following tillage that soybean was planted had little effect on maggot numbers collected, but injury was lowest on soybean planted 3.5 weeks after incorporation of the cover crop. Thermal unit accumulations indicated that seedcorn maggot oviposition occurred at the time of tillage, and that the majority of insects were nearing or entering the non-feeding pupal stage at the time of the last planting, resulting in less plant injury. Phorate treatments provided the largest reduction of maggot numbers. Plant injury was least, however, when soybean was protected by an Agrox seed treatment, especially when the seed and the Agrox were mixed in a bucket before use. These reductions were observed at all three planting times, although the percentage reduction from the control differed among the three planting dates. When spring tillage incorporates a green, living organic matter into the soil in the spring, plant injury can be reduced if a grower waits for 2.5–3 weeks after tillage until planting, when ∼250 thermal units (base of 3.9°C) are accumulated and the majority of insects are in the pupal stage. If planting is done immediately or shortly after tillage, it is recommended that soybean seed be protected with a seed treatment, preferably one that ensures complete coverage of the seed.

Field Resistance of Two Soybean Germplasm Lines, HC95–15MB and HC95–24MB, Against Bean Leaf Beetle (Coleoptera: Chrysomelidae), Western Corn Rootworm (Coleoptera: Chrysomelidae), and Japanese Beetles (Coleoptera: Scarabaidae)

Abstract Two recently released, Mexican bean beetle, Epilachna varivestis, Mulsant, resistant soybean, Glycine max (L.) Merrill, germplasm lines, HC95–15MB and HC95–24MB, were examined for foliar and pod feeding resistance to adult bean leaf beetles, Cerotoma trifurcata (Förster), western corn rootworms, Diabrotica virgifera virgifera LeConte, and Japanese beetles, Popillia japonica Newman. Both lines were planted along with a susceptible control cultivar in 18 by 30-m plots and separate 0.8-ha size fields. Insects were sampled on a weekly basis with a sweep net. In late summer, defoliation ratings were recorded along with data on percentage pod feeding. Although a few significant differences in insect densities were obtained among the soybean lines on some sampling dates, no specific trends were observed in the ability of the resistant germplasm to reduce insect numbers. Insect population densities were similarly on all lines. However, both resistant lines were able to reduce defoliation during the growing season. Conversely, percentage pod feeding was similar among all the soybean lines, with no differences observed. The resistant germplasm lines appear able to lower levels of defoliation, and thus, offer a potential management tactic where leaf feeding, i.e., defoliation, is of concern. However, their ability to greatly reduce beetle population densities, and for the bean leaf beetle, to reduce pod feeding, appears limited.

Registration of 'Vertex' soybean.

Phialophora gregata (Allington & D.W. Chamberlain) W. Gams]. It is also susceptible to iron deficiency chlorosis. Breederseed of Sandusky will be maintained by OARDCOSU with the cooperation of Ohio Foundation Seeds, Inc. A small sample of seed for research purposes can be obtained from the corresponding author for at least 5 yr. Protection for Sandusky under the U.S. Plant Variety Protection Act is pending.