Metolachlor Effects on Peanut Growth and Development

Abstract

Growth and yield responses of peanuts (Arachis hypogaea L.) to preplant incorporated applications of metolachlor [2chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide] herbicide were studied at two locations in Georgia. At Sycamore, GK-7 peanuts which received 3.8 cm irrigation immediately following herbicide incorporation and planting were generally stunted and yielded less than non-inigated peanuts. Metolachlor rates from 2.2 to 6.7 kg ai/ha reduced early and late season growth of irrigated peanuts in 1985 and 1986 but non-irrigated peanuts recovered by mid-August. Yields were suppressed only at the highest rate of metolachor in 1985, but there was no yield response in 1986 or 1987. At Tifton, emergence of Florunner peanuts was delayed and canopy height and width were reduced by metolachlor. Initial flower, peg and pod production were reduced in a linear response to metolachlor rate, resulting in differences in pod development 95 days after planting. There was a rate response for pod yield in 1985 but not in 1986 and grade did not differ either year. In general, emergence and growth were delayed and reduced by preplant incorporated metolachlor when rainfall or irrigation followed application, but yields were not reduced at labeled rates.

Weed Control and Peanut (Arachis hypogaea L.) Response to Acetochlor Alone and in Combination with Various Herbicides

“…Visible injury from metolachlor does not always result in lower peanut yield compared with yield of non-treated peanut under weed-free conditions when applied at rates recommended in by the manufacturer (Cardina and Swann, 1988;Clewis et al, 2007;Grichar and Dotray, 2012). In a study similar to the one reported in this article, Grichar et al (2015) observed in Texas that peanut yield and market grade characteristics were not affected by acetochlor rate or application timing (PPI, PRE, EPOST, POST).…”

“…Peanut stunting and delayed emergence with Smetolachlor has been noted in previous studies (Cardina and Swann, 1988;Clewis et al, 2007;Grichar and Dotray, 2012). Grichar and Dotray (2012) reported peanut stunting from 0 to 15% with S-metolachlor alone and in combination with paraquat, and stunting increased as application timing was delayed to 28 d compared to 7 d after peanut cracking.…”

“…Grichar and Dotray (2012) reported peanut stunting from 0 to 15% with S-metolachlor alone and in combination with paraquat, and stunting increased as application timing was delayed to 28 d compared to 7 d after peanut cracking. Peanut injury by S-metolachlor and the racemic form of metolachlor is dependent on combinations of factors, including herbicide rate, moisture conditions at planting, soil temperature, and rainfall (Cardina and Swann, 1988;Grichar et al, 2004). Cardina and Swann (1988) reported that peanut growth suppression was related to higher metolachlor rates followed by irrigation after planting.…”

“…Peanut injury by S-metolachlor and the racemic form of metolachlor is dependent on combinations of factors, including herbicide rate, moisture conditions at planting, soil temperature, and rainfall (Cardina and Swann, 1988;Grichar et al, 2004). Cardina and Swann (1988) reported that peanut growth suppression was related to higher metolachlor rates followed by irrigation after planting. Although some level of injury was reported in peanut from metolachlor, negative effects were not observed on peanut market grades and yield unless rates higher than those recommended by the manufacturer were applied.…”

Weed Control and Peanut (Arachis hypogaea L.) Cultivar Response to Encapsulated Acetochlor

“…They also reported that POST applications of metolachlor followed by irrigation within 24 h could be effective for yellow nutsedge (Cyperus esculentus L.) control and reduce the chance of peanut injury from soil applications of metolachlor. Combinations of factors, such as herbicide rate, moisture conditions at planting, soil organic matter, and pH may affect peanut injury by chloroacetamide herbicides, such as acetochlor and S-metolachlor (Cardina and Swann, 1988;Mueller et al, 1999;Osborne et al, 1995;Wehtje et al, 1988). Cardina and Swann (1988) reported that metolachlor often delayed peanut emergence and reduced peanut growth when irrigation followed planting.…”