Glyphosate plus 2,4-D Deposition, Absorption, and Efficacy on Glyphosate-Resistant Weed Species as Influenced by Broadcast Spray Nozzle

Abstract

The introduction of 2,4-D–resistant soybean will provide an additional POST herbicide site of action for control of herbicide-resistant broadleaf weeds. The introduction of this technology also brings concern of off-site movement of 2,4-D onto susceptible crops such as sensitive soybean and tomato. The 2,4-D formulation approved for use in 2,4-D–resistant soybean restricts application of the herbicide to nozzles that produce very coarse to ultra-coarse droplet spectrums. The use of larger droplet spectrums for broadcast applications can reduce herbicide deposition onto target weeds and thus influence herbicide efficacy. Field experiments were conducted to evaluate the influence of nozzle design on herbicide deposition onto target plants and the resulting efficacy of a POST application of 280 g ha−1glyphosate plus 280 g ha−12,4-D. The TTI11004 nozzle produced an ultra-coarse droplet spectrum and reduced coverage and deposition density on spray cards as compared with the XR11004 and TT11004 nozzles that produced medium droplet spectrums. The AIXR11004 nozzle also reduced deposition density on spray cards but did not reduce coverage. Herbicide solution deposition onto glyphosate-resistant Palmer amaranth, tall waterhemp, giant ragweed, and horseweed ranged from 0.28 to 0.72 µl cm−2and was not influenced by nozzle design. Herbicide efficacy was reduced by the TTI11004 nozzle on Palmer amaranth and horseweed compared with the AIXR11004, TT11004, and XR11004 nozzles when applications were made to either high densities of plants or plants exceeding the labeled height. The use of the AIXR11004 and TTI11004 nozzles that are listed as approved nozzles for glyphosate plus 2,4-D applications on 2,4-D–resistant soybean did not reduce herbicide deposition onto four of the most troublesome broadleaves and did not reduce herbicide efficacy when applied in conjunction with lower weed densities and smaller weeds.

Performance of Postemergence Broadleaf Herbicides Applied with Novel Lawn Care Application Equipment

“…While Wolf et al (1992) cautioned that high concentrations of 2,4-D in large droplets, such as those sprayed from Z-Spray and PermaGreen sprayers, have potential to reduce herbicide translocation and should be avoided, our weed control results were equivalent across spray droplet sizes. Our results are also consistent with a recent report of glyphosate + 2,4-D efficacy with medium to ultra-coarse droplets at 10 gal/acre (Legleiter et al, 2017).…”

Carrier Volume and Nozzle Effect on 2,4-D and Glufosinate Performances in Hazelnut Sucker Control

“…Drift-reduction nozzles have provided similar efficacy for weed control. The efficacy of 2,4-D with the TTI nozzle, among other drift-reduction nozzles, was not different from the flat-fan nozzle when weed density and size were low (Legleiter et al, 2018). In this study, equivalent efficacy was likely the result of high carrier volumes.…”

“…It is important to note that the height of suckers at the time of treatment was within the recommended size on the herbicide label. The size of the target or its canopy structure can impact herbicide performance (Legleiter et al, 2018). One might observe different results when larger suckers are treated.…”

Influence of establishment timing on growth and fecundity of two itchgrass (Rottboellia cochinchinensis) biotypes grown in Louisiana

“…Generally, it is not advantageous to treat sugarcane using trifloxysulfuron or asulam during summer months, because these herbicides may reduce sugarcane biomass, a critical component determining final sucrose yield. Slower initial growth reported with Louisiana-2 would allow more time for growers to treat emerged plants with POST herbicides, and if plants are treated when small, there is an increased likelihood of plant death from optimal spray coverage (Legleiter et al 2018). Larger R. cochinchinensis plants treated with asulam and or trifloxysulfuron are often injured less than smaller-sized plants.…”