Submitted to: Pacific Northwest Vegetable Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2002
Publication Date: 12/1/2002
Citation: BOYDSTON, R.A. MANAGING NIGHTSHADE IN GREEN PEAS WITH SULFENTRAZONE AND FLUMIOXAZIN. PROCEEDINGS OF THE PACIFIC NORTHWEST VEGETABLE ASSOCIATION, PASCO, WA, P. 10-14. NOV 2002. Interpretive Summary: Nightshade berries contaminate processing peas reducing quality and increasing processing costs. Nightshade berries are similar in color, density, and size to peas, making them difficult to separate from peas during processing. Nightshade control in peas is erratic with currently labeled herbicides. Two new herbicides, flumioxazin and sulfentrazone, were tested alone at five rates and in combination with pendimethalin or metolachlor for preemergence nightshade control in peas. Both herbicides caused stunted growth and leaf necrosis, and pea injury increased as herbicide rate increased for both flumioxazin and sulfentrazone. Pea injury was greater when either herbicide was tank mixed with metolachlor. Flumioxazin did not reduce pea yields. Sulfentrazone applied at 0.125 lb ai/a or less was safe on peas and maintained yields equal to hand-weeded checks. All herbicide treatments controlled nightshade greater than 91%. A simple model is being developed to predict hairy nightshade berry contamination in harvested peas, which could assist growers in decisions on whether to apply a postemergence herbicide for nightshade control. The model utilizes growing degree days (GDD40) of the pea variety, and calculates growing degree days required to produce a nightshade berry of a selected diameter that is not easily separated from peas. When the heat units required to mature the peas are greater than the heat units required to produce nightshade berries of 6 mm diameter then a decision to spray with a postemergence herbicide is made.
Technical Abstract: Nightshade berries can contaminate processing peas reducing quality and increasing processing costs. Nightshade control in peas is erratic with currently labeled herbicides. A model was developed to assist growers in making decisions for postemergence herbicide applications to prevent nightshade contamination in harvested peas. The model utilizes heat units required to mature peas, grower scouting for nightshade emergence, and local weather data. Hairy nightshade emerging from early May to mid June required approximately 1120 GDD40 to produce 6 mm diameter nightshade berries. Flumioxazin and sulfentrazone were tested alone at five rates and in combination with pendimethalin or metolachlor for PRE nightshade control in peas. The trial was located on a Quincy sand soil containing 0.5% organic matter near Paterson, WA. Pea emergence was delayed with all herbicide treatments except the lowest rate of flumioxazin (0.03 lb ai/a) and sulfentrazone (0.094 lb ai/a). Both herbicides caused stunted growth and leaf necrosis at higher rates. Pea injury was greater when flumioxazin or sulfentrazone was tank mixed with metolachlor. No treatments containing flumioxazin reduced pea yield, but sulfentrazone above 0.125 lb ai/a reduced pea yield. Most herbicide treatments delayed pea maturity compared to untreated checks. Both herbicides controlled hairy and black nightshade, pigweed, and common lambsquarters well.