Response of Eastern Black Nightshade (Solanum ptycanthum) to Low Rates of Imazethapyr and Metolachlor

Abstract

Eastern black nightshade is a problem weed in soybeans primarily due to interference with harvesting operations and reductions in crop quality. Field and greenhouse studies were conducted in 1990 and 1991 at Harrow, Ontario, to determine whether sublethal rates of imazethapyr and metolachlor could suppress growth and berry production by eastern black nightshade. In the greenhouse, plants treated with metolachlor PRE at 0.8 kg ai ha−1or imazethapyr POST at 30 g ai ha−1(1/3 to 1/2 the labelled rates) produced significantly fewer berries in the first flower cluster, with fewer seeds per berry, than untreated plants. When a surfactant was added to the imazethapyr, almost all flower buds in the first cluster were aborted. Treated plants recovered from the damage, however, and did not differ significantly from control plants in dry weight or berry production 110 DAP. In the field, application of 50 g ai ha−1imazethapyr POST (2/3 of the lowest labelled rate), with or without a surfactant, resulted in delayed flowering, abortion of most of the flower buds in the first cluster, and greatly reduced growth and total berry production between soybean leaf abscision and harvest. Application of metolachlor + metribuzin PPI in the field at 2/3 of the labelled rate (1.6 + 0.25 kg ai ha−1) was not sufficient to reduce nightshade growth and berry production after soybean leaf abscision. Sublethal rates of imazethapyr and metolachlor did not reduce seed viability in either the greenhouse or the field.

ALS-Inhibitor Resistance in Populations of Eastern Black Nightshade (Solanum ptycanthum) from Ontario

“…These results indicate that there was no cross-resistance in the R population to chloroacetamide herbicides. Chloroacetamide herbicides have been reported to provide adequate to excellent control of eastern black nightshade (Ogg 1986;Ward and Weaver 1996). Our results show that these herbicides could serve as effective alternatives for control of ALS inhibitor-resistant eastern black nightshade populations in Ontario.…”

“…ALS-inhibiting herbicides are commonly used to control eastern black nightshade in soybean fields (Milliman et al 2003;Ward and Weaver 1996). However, repetitive use of these herbicides has selected for resistant populations of eastern black nightshade in Wisconsin (Volenberg et al 2000) as well as Illinois and Indiana (Milliman et al 2003).…”

Tolerance of White Beans to Postemergence Broadleaf Herbicides

“…Expansion of the registration of these POST herbicides will provide white bean growers with additional control options for broadleaf weeds. Research has shown that tolerance of dry beans (Phaseolus vulgaris) to various herbicides is largely dependent on rate, cultivar, and environmental conditions (Bauer et al 1995;Blackshaw and Saindon 1996;Renner and Powell 1992;VanGessel et al 2000;Vencill et al 1990;Ward and Weaver 1996;Wilson and Miller 1991). The objective of this research was to determine the tolerance of two white bean cultivars to POST applications of imazamox plus fomesafen, imazamox plus bentazon, cloransulam-methyl, thifensulfuron, chlorimuron, and bromoxynil for possible Canadian registration of these herbicides in white bean production in Ontario.…”

Tolerance of Black Beans (Phaseolus vulgaris) to Soil Applications ofS-Metolachlor and Imazethapyr1

“…), lambsquarters (Chenopodium album L.), annual nightshades (Solanum spp. ), ladysthumb (Polygonum persicaria L.), wild mustard (Sinapis arvensis L.), and common ragweed (Ambrosia artemesiifolia L.) (Arnold et al 1993;Bauer et al 1995;OMAFRA 2002;Ward and Weaver 1996).…”

“…Tolerance of dry beans to S-metolachlor and imazethapyr is generally attributed to application method, application rate, cultivar, and environmental conditions (Blackshaw and Saindon 1996;Renner and Powell 1992;VanGessel et al 2000;Vencill et al 1990;Ward and Weaver 1996). More information is needed on the tolerance of black beans to S-metolachlor and imazethapyr alone or in tank mixture for selective weed control in Ontario.…”