Growth response of velvetleaf to three postemergence herbicides

Abstract

Knowledge of how reduction in the rate of herbicide application or rotation of their mode of action influences weed growth will provide insight into how successful these practices will be in an integrated weed management program. Field experiments were conducted in 1996 and 1997 to quantify velvetleaf growth response to three postemergence herbicides, each with a different mode of action. A monoculture of velvetleaf was treated with halosulfuron, dicamba, and flumiclorac at 0, 0.10, 0.25, 0.50, 0.75, and 1.0 ϫ the labeled rate for weed control in corn. Percent plant mortality increased with rate of application; the greatest mortality occurred in flumiclorac treatments in 1996 and in halosulfuron and flumiclorac treatments in 1997. Growth rate temporarily decreased as application rate increased. Maximum height decreased as rate of application increased, with the dicamba treatment resulting in the greatest (27%) reduction. Early-season leaf area index decreased with increasing rate of application, the greatest reduction occurring with halosulfuron (1997) and flumiclorac (1996 and 1997) treatments. The number of leaves produced per plant was temporarily reduced by all treatments, but treatment with dicamba later resulted in larger numbers of small leaves. The number of velvetleaf seed capsules produced per surviving plant was not reduced by any treatment, but the number of capsules per square meter was reduced by the 0.5 ϫ rate of flumiclorac (1996) and the 0.5and 1.0 ϫ rates of halosulfuron (1997). Research is needed to evaluate whether the temporary suspension of velvetleaf growth after herbicide treatment is sufficient to prohibit crop yield reduction and velvetleaf capsule production.

Weed Management in Beans Using Subdoses of Fluazifop-P-Butyl + Fomesafen

“…Similar results demonstrated the efficiency of reduced doses to control a mixed population of black-jack and sida when applying 75% of the recommended dose of acifluorfen + bentazon (Rizzardi and Fleck, 2004). It is worth mentioning that even if a certain herbicide, applied at lower doses than the recommended ones, does not cause complete weed death, it can suppress its growth, and this effect will negatively affect its competitive ability with the crop (Murphy and Lindquist, 2002).…”

Dose econômica ótima de acifluorfen + bentazon para controle de picão-preto e guanxuma em soja

“…Esses resultados demonstram que os acréscimos em controle e rendimento de grãos obtidos com as doses de 1,75 e 2,0 L ha -1 do herbicida Doble não foram suficientes para compensar o maior custo do controle. Possivelmente, com doses menores do que 1,75 e 2,0 L ha -1 tenha ocorrido diminuição na habilidade competitiva das plantas daninhas que sobreviveram ao produto, a exemplo do relatado por Murphy & Lindquist (2002). Para esses autores, o efeito dos herbicidas no crescimento da planta daninha varia com a dose de herbicida utilizada, e a supressão no crescimento da planta daninha afeta negativamente sua habilidade competitiva com a cultura.…”

Nitrogen supply affects root:shoot ratio in corn and velvetleaf (Abutilon theophrasti)

“…While market prices have continued to decline in recent years, input costs for nitrogen fertilizer and weed control measures continue to rise, leading to a decreased profit margin (Liebman et al 2001). Along with increasing control costs, factors such as herbicide resistance and heightened environmental awareness have led to ecologically based weed management programs that focus on how components such as climate, edaphic properties, and resource availability affect crop and weed competitiveness (Murphy and Lindquist 2002).…”