TITLE:
Influence of Water Quality, Formulation, Adjuvant, Rainfastness, and Nozzle Type on Efficacy of Fomesafen on Palmer Amaranth (Amaranthus palmeri) Control
AUTHORS:
Vijay K. Nandula, William T. Molin, Jason A. Bond
KEYWORDS:
Adjuvant, Fomesafen, Formulation, Nozzle, Palmer Amaranth, Rainfastness, Soybean, Water Quality
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.9 No.8,
July
19,
2018
ABSTRACT: Protoporphyrinogen
oxidase (PPO) inhibitors are one of the few remaining postemergence herbicide
options for controlling Palmer amaranth in soybean growing areas of
Mississippi, USA. Most Palmer amaranth populations in Mississippi are resistant
to both glyphosate and acetolactate synthase inhibitors. Resistance to PPO
inhibiting herbicides in Palmer amaranth has very recently been reported in
Arkansas, Tennessee, and isolated pockets of Mississippi. A significant
proportion of reports of PPO inhibitor failures in Mississippi are not
considered to be resistance-related at this time. Therefore, the objective of
this research was to evaluate factors affecting the efficacy of fomesafen on
Palmer amaranth including: quality of spray carrier (water), formulations,
adjuvant, rainfastness, and nozzle type. All water samples and formulation
combinations provided >95% control of Palmer amaranth 3 WAT. Some
combinations of water samples and formulations did not result in complete
control of the treated plants, with one or two individuals surviving 3 WAT.
Formulation 1 provided 99% control compared to 95% from formulation 2.
Irrespective of combinations of herbicide, adjuvant and height, control of
Palmer amaranth was ≥91%. Formulation 1 provided 94% control compared to 88%
from formulation 2. The adjuvant x height interaction was significant, owing to
a 10% reduction in control of larger plants (86%) compared to smaller plants
(96%) in presence of COC. COC provided better control (93%) than NIS (88%). Simulated
rainfall applied ≥60 min after herbicide application did not adversely affect
efficacy on Palmer amaranth when formulation 1 was applied in combination with
NIS, with control ranging from 94% to
100%. Formulation 1 with COC provided ≥93% control at all rainfall application
times, except 30 min after herbicide treatment, which resulted in 79% control.
Formulation 2 provided better control with COC (79% to 100%) than NIS (71% to
90%), in general, across the rainfall treatments applied at various times
following herbicide application. All nozzle and weed height combinations
resulted in 89% or better control of Palmer amaranth. In summary, water
quality, formulation, adjuvant, rainfastness, or nozzle type did not affect the
activity of fomesafen under optimal application conditions in the greenhouse.