Nozzle Selection and Adjuvant Impact on the Efficacy of Glyphosate and PPO-Inhibiting Herbicide Tank-Mixtures

Abstract

PPO-inhibiting herbicides in combination with glyphosate for postemergence applications is a common approach to manage glyphosate- and ALS-inhibitor-resistant weeds. PPO-inhibitors can reduce glyphosate translocation when applied in tank-mixtures, but adjuvants may be used to overcome this effect. Additionally, optimal droplet size may be affected by tank-mixtures of different herbicides and it can be crucial to herbicide efficacy. Field and greenhouse studies were conducted to investigate the impact of nozzle selection and adjuvants on weed control and interactions when applying PPO-inhibitors (fomesafen or lactofen) alone or in tank-mixture with glyphosate to five weed species using six nozzle types. Ultra-coarse droplets were just as effective as medium droplets regardless of the spray solution, but have a lower likelihood of off-target movement. Tank-mixtures applied were consistently antagonistic to common lambsquarters, horseweed, and Palmer amaranth. Only fomesafen was antagonistic to kochia whereas synergistic interactions were observed when glyphosate plus lactofen were applied in combination with COC, DRA + COC, or NIS. Separate applications are advisable with herbicide- and weed-specific situations to avoid antagonism, which is necessary to achieve optimum weed control and maintain the effectiveness of PPO-inhibitors. Future research should continue to look at these important interactions across a wide range of weed species.

Efficacy of Metribuzin Doses on Physiological, Growth, and Yield Characteristics of Wheat and Its Associated Weeds

“…According to Rizwan et al (2018) , the application of herbicide increases the number of spike-bearing tillers (m –2 ) significantly. Our findings are further supported by Moraes et al (2021) who stated that herbicides applied with adjuvants either at full or reduced doses significantly decreased the weeds infestation than herbicides used alone and resultantly improved the spike-bearing tillers with concomitant reduction of non-spike-bearing tillers by supplying more space, light, and nutrients to crop plants. Further studies suggested that optimum weed control was based on the selection of herbicide and adjuvants along with weed-specific situations ( Javaid et al, 2012 ; Moraes et al, 2021 ).…”

“…Our findings are further supported by Moraes et al (2021) who stated that herbicides applied with adjuvants either at full or reduced doses significantly decreased the weeds infestation than herbicides used alone and resultantly improved the spike-bearing tillers with concomitant reduction of non-spike-bearing tillers by supplying more space, light, and nutrients to crop plants. Further studies suggested that optimum weed control was based on the selection of herbicide and adjuvants along with weed-specific situations ( Javaid et al, 2012 ; Moraes et al, 2021 ). Similarly, Khalil et al (2010) also revealed that greater numbers of spike-bearing tillers were obtained with the application of carfentrazone-ethyl + isoproturon as compared with weedy check treatment.…”

“…Metribuzin, an effective postemergence triazine group herbicide with the mode of action of photosynthesis inhibition ( Shah et al, 2009 ; Štěpánová et al, 2012 ), is often applied to restrict the broadleaf and annual grass weeds in wheat, potatoes, and tomatoes ( Majumdar and Singh, 2007 ). The efficiency of herbicides that are used after emergence can be enhanced by adding adjuvants ( Javaid et al, 2012 , 2020 ; Moraes et al, 2021 ). Adjuvants help to reduce herbicide dose and improve its biological activity by altering the surface tension of spray solution, increasing absorption, translocation rate, effect on atomization, and enhanced penetration ( Hamouda et al, 2021 ).…”

Use of Ultra Coarse Droplets at Different Spray Volumes to Control Weeds With Dicamba and Glyphosate Herbicides

“…Example of the coverage obtained (blue spots) in one of the experimental plots with the application of ultra-coarse droplets at a volume of 58 L ha -1 . Moraes et al (2021) studied the control of weeds with glyphosate, fomesafen, and lactofen using different droplet spectra at a spray volume of 187 L ha -1 . They concluded that ultra-coarse droplets had similar control results to medium droplets.…”

Rapid weed adaptation and range expansion in response to agriculture over the last two centuries

“…The importance of chemical inputs in shaping weed agricultural adaptation is clear in that the most significant agriculturally associated SNP (raw p-value = 8.551x10 -11 , [FDR corrected] q-value = 0.00062) falls just 80 kb outside the gene protoporphyrinogen oxidase (PPO)-the target of PPO-inhibiting herbicides (Fig 2B). PPO herbicides were widely used in the 1990s, but have seen a recent resurgence to control and slow the spread of glyphosate resistant weeds (25,26). Other genes with the strongest agricultural associations include ACO1, which has been shown to confer oxidative stress tolerance (27); HB13, involved in pollen viability (28) as well as drought and salt tolerance (29); PME3, involved in growth via germination timing (30); CAM1, a regulator of senescence in response to stress (31,32); and both CRY2 and CPD, two key regulators of photomorphogenesis and flowering via brassinosteroid signaling (33)(34)(35)(36) (Table S2).…”