PP-604 rate andAvena fatuadensity effects on seed production and viability inHordeum vulgare

Abstract

High Avena fatua control costs have caused some Hordeum vulgare growers to use reduced rates of herbicides without fully understanding the consequences. Field studies near Moscow and Genesee, ID, were conducted to determine the effect of A. fatua density and PP-604 rate on A. fatua seed production in H. vulgare and on H. vulgare yield. PP-604 treatments were 25, 50, 100, 150, and 200 (minimum labeled rate) g ha−1, and five A. fatua densities ranged from 0 to 386 plants m−2. Visual A. fatua control was greater than 85% with 100 g ha−1 PP-604 at all locations. Data from 1998 were used to construct nonlinear exponential decay and parabolic models to describe the effect of reduced herbicide rates on viable A. fatua seed production and relative H. vulgare grain yield, respectively. At A. fatua densities of 42 to 138 plants m−2, 46 to 71% of the minimum labeled rate of PP-604 reduced seed production 95%. However, an estimated 140 to 235 seeds m−2 were produced at this level of control, which may not ensure a decline in the A. fatua population over the long-term. Hordeum vulgare grain yield was maximum when 70 to 85% of the minimum labeled rate was applied to A. fatua densities of 42 to 138 plants m−2. A higher rate of PP-604 likely will be required to ensure a decline in A. fatua populations over the long-term than needed to obtain maximum H. vulgare grain yield in a single growing season.

Influence of variable rates of imazamethabenz and difenzoquat on wild oat (Avena fatua) seed production, and wheat (Triticum aestivum) yield and profitability

“…The efficacy of reduced graminicide rates may be greater at relatively low wild oat infestations (Wille et al 1998;Belles et al 2000;. However, several other factors including water quality, carrier volume, wild oat growth stage and/or location, year and environmental factors also influenced the efficacy of low rates of several graminicides (Spandl et al 1997;Stougaard et al 1997;Stougaard 1999;Stevenson et al 2000).…”

“…Only a few studies have investigated the relationship between reduced herbicide rates and wild oat seed production, most often with wild oat in barley (Hordeum vulgare L.) (Wille et al 1998;Belles et al 2000;O'Donovan et al 2001). In a recent study with wheat (Triticum aestivum L.), wild oat seed production, in most cases, increased considerably when the rate of tralkoxydim was reduced to 50% of recommended (O'Donovan et al 2003), suggesting that the practice may not be without longterm risk.…”

Produção de sementes por picão-preto e guanxuma em função de densidades das plantas daninhas e da época de semeadura da soja

“…Diante dos resultados obtidos nesta pesquisa e objetivando diminuir a produção de sementes por plantas daninhas, é importante limitar não somente a densidade de plantas daninhas, mas também sua produção de massa (Figuras 3 e 4). Nesse contexto, a adoção de estratégias de manejo de plantas daninhas, como arranjo apropriado de plantas da cultura (Norris et al, 2001), emprego de cultivares com maior habilidade competitiva (Mortensen et al, 2000) e uso de doses reduzidas de herbicidas (Belles et al, 2000), influencia negativamente tanto o acú-mulo de fitomassa pelas plantas daninhas como a formação de estruturas reprodutivas. Em conseqüência, essas práticas podem neutralizar os efeitos decorrentes do aumento das reservas de sementes no solo, causado pela adoção do manejo de plantas daninhas com base em NDE.…”

Effect of reduced doses of mesosulfuron + iodosulfuron to control weeds in no-till wheat under Mediterranean conditions

“…Below-labelled herbicide doses in combination with some mechanical weed control have proven to be an effective way of reducing herbicide input in agricultural systems (Hamill and Zhang, 1995). Belles et al (2000) have reported that a 50% dose of tralkoxydim controls more than 85% of wild oat (Avena fatua L.) in barley (Hordeum vulgare L.). O'Donovan et al (2001) has also found that tralkoxydim at belowlabelled doses often provides good control of wild oat.…”