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

Abstract

Corn inbreds are often more sensitive to herbicides than hybrids. Field experiments were conducted with three corn inbreds to (1) evaluate inbred sensitivity to the acetamide herbicides acetochlor, dimethenamid, flufenacet, and metolachlor, (2) compare the effects of various crop safeners in combination with acetochlor and metolachlor, and (3) measure the effect of herbicide microencapsulation on acetochlor injury. Herbicides were applied preemergence at the registered rate and at two, three, or four times the registered rate in corn. Injury ratings, plant population, and the percentage of plants showing acetamide injury symptoms were used to measure herbicide effect. The inbreds ‘Mo17’ and ‘Great Lakes 15’ (GL15) were sensitive to acetamide injury. Reductions in plant population and increases in the injury rating and the percentage of injured plants were caused by acetochlor, dimethenamid, flufenacet, metolachlor, and flufenacet + metribuzin when applied at three times the registered rate. The inbred ‘B73’ was not injured. The safeners benoxacor and dichlormid reduced injury caused by metolachlor. The percentage of plants injured by metolachlor 15 days after treatment (DAT) was lower when benoxacor was the safener compared to dichlormid. By 28 DAT, plants treated with safeners recovered from injury, and there were no differences between the treatments. The safeners dichlormid and furilazole reduced, but did not always eliminate, injury caused by acetochlor applied at three times the registered rate. Microencapsulation of acetochlor reduced injury to GL15. When the safeners dichlormid or furilazole were included in an acetochlor formulation, microencapsulation did not further reduce corn injury.

Screening of some South African maize (Zea maysL.) cultivars for acetochlor tolerance

“…The different categories of these maize cultivars may be proof that tolerance to acetochlor in maize is genetically controlled. This is in agreement with the findings of Bernards et al (2006) that the variable response of hybrids to acetochlor was probably due to genetic inheritance. These results may be a true reflection of what may happen under field conditions, a result that was noted by Kanyomeka (2002) on his research on sensitivity of inbreds and hybrids to selected herbicides.…”

“…Breaux et al (2002) rated maize as being highly tolerant to acetochlor, although they only worked with a single genotype. Bernards et al (2006), on the other hand, demonstrated differential tolerance to acetochlor in three inbred maize lines. No published information on the tolerance of South African maize cultivars to acetochlor could be found.…”

“…This differential tolerance among cultivars has been reported for various herbicides and in a number of different crops. Various researchers have reported cultivar response differences in a number of crops to herbicides within the acetamide group of herbicides (Voges & Nel, 1974;Narsaiah & Harvey, 1977;Bernards et al, 2006;Allemann & Ceronio, 2007;2009) . Bernards et al (2006) reported that the greatest factor in acetamide injury to crops may be sensitivity of inbred lines or cultivars to the herbicide.…”

Herbicide Safeners Increase Waxy Maize Tolerance to Nicosulfuron and Affect Weed Control

“…The waxy maize was treated with the different safeners listed in Table 1. Higher than label rates are often used in order to further understand relative crop safety and to evaluate the potential interactions between safeners and maize hybrid sensitivity [14,15]. Nicosulfuron effects were evaluated at 90 g/ha with or without safener at 15 g/ha.…”

Response of Eight Sweet Maize (<i>Zea mays</i> L.) Hybrids to Saflufenacil Alone or Pre-Mixed with Dimethenamid-P

“…Dimethenamid-p can provide season long control of a broad spectrum of grass and broadleaved weeds such as barnyardgrass (Echinochloa crusgalli), autumn panicum (Panicum dichotomiflorum), giant foxtail (Setaria faberi), green foxtail (Setaria viridis), yellow foxtail (Setaria glauca), large crabgrass (Digitaria sanguinalis), smooth crabgrass (Digitaria ischaemum), witchgrass (Panicum capillare), redroot pigweed (Amaranthus retroflexus), American black nightshade (Solanum americanum), and eastern black nightshade (Solanum ptycanthum) [2,7]. Dimethenamid-p at the registered application doses has been shown to cause little or no injury in field maize [8,9]. Saflufenacil plus dimethenamid-p can provide an effective broad spectrum herbicide option for the control of troublesome species in sweet maize.…”