Factors in Alachlor and Metolachlor Injury to Corn (Zea mays) Seedlings

Abstract

Growth chamber experiments were conducted to determine if certain genetic, environmental, and chemical factors or their interactions promote chloroacetamide herbicide injury to corn seedlings. Greater chloroacetamide injury occurred with ‘Pioneer 3320’ than with ‘Pioneer 3780’ hybrid corn, with 15 C than with 30 C soil temperature, with soil moisture at 105% field capacity (FC) than at 75% FC, with alachlor than with metolachlor, and with a herbicide rate of 2.2 kg/ha than with 1.1 kg/ha. Covering the plant containers with clear plastic until seedling emergence caused alachlor to be more phytotoxic to corn than metolachlor. Most factors evaluated increased the injury to corn in an additive manner.

Inbred Corn Response to Acetamide Herbicides as Affected by Safeners and Microencapsulation

“…Although injury was observed in all 4 yr, injury ratings, the percentage of injured plants, and plant populations were more affected in 1996 and 2000. There was no obvious pattern between precipitation and injury, even though high soil water content has been linked to increased injury from metolachlor and alachlor (Boldt and Barrett 1989). Soil organic matter was higher in the fields used in 1996 and 2000 (Table 1) and may have increased soil water content.…”

“…In 2000, daily high temperatures 8 to 14 DAT were cooler than during the same period in 2001 (Table 1). This cooler weather may have slowed emergence and increased corn uptake of acetochlor, flufenacet, and dimethenamid (Boldt and Barrett 1989;Viger et al 1991b). However, cooler temperatures 0 to 14 DAT in 1997 did not increase injury compared to 1996.…”

“…Injury symptoms include twisting, curling, or distortion of the leaves; stunting; enlarged stems; failure of true leaves to emerge from the coleoptile; and in severe cases, plant death (Leavitt and Penner 1978a;. Environmental conditions that favor acetamide injury are high soil moisture, cool soil temperatures, and high herbicide rates (Boldt and Barrett 1989;. The greatest factor in acetamide injury may be inbred or hybrid sensitivity.…”

Sweetpotato [<i>Ipomoea batatas</i> (L.) Lam.] Response to <i>S</i>-Metolachlor and Rainfall under Three Temperature Regimes

“…Environmental factors such as rainfall and temperature have a major impact on crop growth and development, as well as how the crop responds to herbicides in the chloroacetamide family [32]- [35]. Rainfall occurring shortly after an S-metolachlor application can result in movement of the herbicide into the root zone leading to increased absorption and severe sugarbeet (Beta vulgaris L.) injury [36].…”

“…Rainfall occurring shortly after an S-metolachlor application can result in movement of the herbicide into the root zone leading to increased absorption and severe sugarbeet (Beta vulgaris L.) injury [36]. In a growth chamber experiment, low soil temperature (15˚C) increased metolachlor injury to corn and delayed plant emergence 1 to 2 days as well as the time needed to reach the first leaf stage by 2 days compared with plants grown in a 30˚C soil environment [32]. Increased soybean and dry edible bean injury have been reported with increasing soil moisture and PRE applications of dimethenamid and metolachlor at high rates [33] [37].…”