EASTERN BLACK NIGHTSHADE

Abstracts:

• Effect of Pre and Postemergence Herbicides for Eastern Black Nightshade (Solanum Ptycanthum Dun.) Control in Soybeans. E. L. Werner, W. S. Curran, J. O. Yocum and M. J. VanGessel, 1997. Proc. NEWSS 51:64.

Effect of Pre and Postemergence Herbicides for Eastern Black Nightshade (Solanum Ptycanthum Dun.) Control in Soybeans. E. L. Werner, W. S. Curran, J. O. Yocum and M. J. VanGessel, 1997. Proc. NEWSS 51:64.

Season-long control of eastern black nightshade(Solanum ptycanthum Dun.) hasbeen difficult due to sporadic emergence and the lack of effective soybean(Glycine max) herbicides. Research conducted at Penn State on current available and experimental herbicides for the control of eastern black nightshade may give producers added options.

Small plot field research was conducted in southeastern Pennsylvania in 1995 and 1996 and Townsend, Delaware in cooperation with the University of Delaware for the 1996 growing season. Soybeans were planted to 30 inch rows for the southeastern PA locations and in drilled rows in DE. Preemergence treatments were applied shortly after planting with a CO₂ backpack sprayer. In 1995, postemergence treatments were applied when nightshade was 1 to 2 inches in height. In 1996, early postemergence treatments were applied when nightshade was less than 1 inch tall, while postemergence treatments were applied at 2 inches or greater in height. Crop phytotoxicity, visual weed control ratings, crop yield, and eastern black nightshade biomass and berry production were measured. Greenhouse research was conducted to evaluate the efficacy of several corn and soybean herbicides, and to support eastern black nightshade field studies.

Field studies indicated that application timing had no effect in southeastern PA, however in DE, better control was achieved with the early postemergence application. The lack of control from the later post treatments was probably due to early canopy closure and poor spray coverage from the late treatment. Lactofen, acifluorfen, imazethapyr, and fomesafen offered the most consistent season-long nightshade control of all the postemergence herbicides examined. Chlorimuron + thifensulfuron offered little to no control at all locations, however the addition of lactofen offered excellent season-long control.

Results with preemergence treatments were variable between study years and locations. In 1995, metolachlor, alachlor, dimethenamid, sulfentrazone, imazethapyr and fluamide + metribuzin all gave 90 to 100% control by the end of the season. Imazaquin, chlorimuron + metribuzin and fluamide all offered 80 to 90% control. In 1996 at the southeastern PA location, metolachlor, sulfentrazone and imazethapyr provided 80 to 90% control by the end of the season. All other preemergence herbicides tested had less than 50% control. No soybean injury was observed at the PA location. Early season ratings for the DE location indicated excellent nightshade control with all preemergence herbicides tested, however, CGA277102II, dimethenamid and chlorimuron + metribuzin provided only 60 to 80% control. Due to the sandy soils at this site, significant soybean injury was observed with several preemergence herbicides.

Research at Penn State indicated that postemergence herbicides were overall less active under greenhouse conditions. Ratings 1 WAA indicated activity with most of the herbicides, however, dry weights 3 WAA indicated nightshade regrowth for most of the treatments. Results from the preemergence greenhouse study support field studies with sulfentrazone, metolachlor, dimethenamid and alachlor providing 80 to 100% control 8 WAA. However, some herbicides including imazethapyr and imazaquin were not as active under greenhouse conditions.