Time of Emergence of Eight Weed Species

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Abstract
Under irrigated field conditions at Prosser, WA, Russian thistle [Salsola kali (L.) var. tenuifolia Tausch. ♯3 SASKR] began to emerge by mid-March each year and usually had completed its emergence by May 1. Common lambsquarters (Chenopodium album L. ♯ CHEAL) was the next to appear, usually during the third or fourth week of March. Barnyardgrass [Echinochloa crus-galli (L.) Beauv. ♯ ECHCG], redroot pigweed (Amaranthus retroflexus L. ♯ AMARE), hairy nightshade (Solarium sarrachoides Sendt. ♯ SOLSA), black nightshade (5. nigrum L. ♯ SOLNI), eastern black nightshade (S. ptycanthum Dun.), and cutleaf nightshade (S. triflorum Nutt. ♯ SOLTR) generally began to emerge during the first 2 weeks of April and emergence generally peaked mid-April to mid-May. Russian thistle and cutleaf nightshade had the most restricted emergence patterns, whereas seedlings of common lambsquarters, redroot pigweed, hairy nightshade, and black nightshade emerged each month from April through September. Shallow tillage at monthly intervals increased the overall emergence of common lambsquarters, redroot pigweed, black nightshade, and eastern black nightshade; decreased the emergence of barnyardgrass; and had no effect on the emergence of Russian thistle, cutleaf nightshade, or hairy nightshade.