Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2003
Publication Date: 9/7/2004
Citation: Boydston, R.A., Peachey, E. 2004. Predicting hairy nightshade berry production in peas and beans based on time of emergence and heat units. Western Society of Weed Science Meeting Proceedings. 57:55.
Technical Abstract: Hairy nightshade, Solanum sarrachoides, berries are similar in size, density, and color to processed peas and often contaminate peas and green beans reducing quality and increasing processing costs. Processors are able to remove nightshade berries smaller than 5 to 6 mm diameter by sieving. Studies were conducted in 2002 and 2003 at Paterson, WA and in 2003 in Corvallis, OR to determine the effect of hairy nightshade emergence date on potential for nightshade to produce berries larger than 5 to 6 mm diameter. In Washington, hairy nightshade required approximately 621 and 676 GDD base 4.4° C in 2002 and 2003, respectively, from emergence to produce berries 6 mm diameter. Emergence date had little effect on growing degree days (GDD) base 4.4° C required to produce 6 mm diameter berries. Germinable nightshade seed was obtained from berries of all size classes (< 3.5, 3.5 to 4.5, 4.5 to 6, 6 to 7, and > 7 mm diameter) collected at pea harvest. However, hairy nightshade berries in the three smallest size classes averaged only 0.2, .3, and 0.7 germinable seed per berry. In Oregon, hairy nightshade required 659 GDD base 4.4° C from emergence to produce berries 5 mm diameter. Bean planting date from May 7 to June 17, 2003 had little effect on GDD base 4.4 C required for hairy nightshade to flower or to produce 5 mm diameter nightshade berries. Lack of control of hairy nightshade season long did not reduce pea or green bean yield at the weed densities present in these studies. A simple 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 date, and local air temperature data.