During August of the 2000 growing season, Aphis glycines Matsumura, an aphid native to Asia, was found colonizing soybean plants in Illinois. Accepted for publication 1 February 2001. Published 5 February 2001.

Summary: The absorption and loss of four chloro‐s‐triazines was investigated in excised roots of four Setaria taxa. Different taxa absorbed the various triazines at different rates. In general, triazine absorption was greater at 2°C than at 22.5°C, and absorption rates were linear functions of external concentrations. Efflux studies showed marked differences in the rate of loss of 14C‐atrazine, 14C‐simazine, and 14C‐propazine from root sections of robust white foxtail (Setaria viridis var. robustaalba Schreiber). The roots lost 14C‐atrazine very quickly, and the loss was similar in either water or 12C‐atrazine. Atrazine appears to be restricted to the apoplast of the root. 14C‐atrazine was lost more rapidly than either 14C‐simazine or 14C‐propazine to water or to solutions containing the unlabelled herbicide. Efflux of 14C‐simazine was greater than that of 14C‐propazine to solutions of CaCl2. From the pattern of efflux, it was concluded that 14C‐simazine and 14C‐propazine accumulated in the root symplast. Furthermore, the decreases in chloro‐s‐triazine absorption in the presence of metabolic inhibitors (dinitrophenol, sodium arsenite) may suggest that 14C‐simazine and 14C‐propazine entered the symplast by an energy‐dependent process.

Redroot pigweed (Amaranthus retroflexusL.) and robust foxtail [Setaria viridis(L.) Beauv. var.robusta-albaSchreiber (RWF) orSetaria viridisvar.robusta-purpureaSchreiber (RPF)] were investigated regarding their ability to interfere with soybean [Glycine max(L.) Merr. ‘Amsoy 71′] at different weed densities and soybean row spacing throughout two growing seasons. Final weed densities for each species tended to reach a common value because of intraspecific interference regardless of the initial density. With cultivation, a narrow soybean row spacing (38 cm) resulted in less weed growth than did a wide row spacing (76 cm) but with no cultivation, the trend was reversed. Soybeans provided less interference to foxtail than to pigweed during both growing seasons. Interference from foxtail adversely affected soybean yield components and soybean seed yield more than did pigweed interference. Water-stress conditions in 1976 increased the intensity of weed interference and reduced soybean seed yield more severely than in 1975 when moisture was adequate throughout the growing season.

Four starch-encapsulated formulations of EPTC(S-ethyl dipropylthiocarbamate) and of butylate(S-ethyl diisobutylthiocarbamate) were prepared and evaluated by comparison with their respective emulsifiable concentrate formulations for their slow-release capabilities and efficacies. Chemical and biological evaluation indicated that difference in controlled-release could be achieved by the selection of the starch xanthate and oxidant used in the formualtion process. EPTC and butylate released slower when formulated as starch-encapsulated granules than when formulated as emulsifiable concentrates under soil conditions that favored rapid release. The initial release was adequate for weed control and slow enough for desired residual activity. Repeated seeding and harvesting the treated soils and bioassays of treated soils generally produced release rate anticipated from short term dry and wet chemical tests.