Efficacy and Phytotoxicity of Glufosinate and Glyphosate on Weeds Under Banana, Guava, and Lychee Grove Conditions at the Tropical Research and Education Center

Abstract

Weed pressure under south Florida’s warm, marine subtropical climate is intense, especially during the summer months
when high temperatures and frequent rainfall occur. A 0.14-acre ‘Grand Nain’ banana, a 0.37-acre ‘Barbie Pink’
guava, and a 0.16-acre ‘Sweet Heart’ lychee grove were used to investigate the efficacy and fruit crop phytotoxicity
of herbicides from 14 May through 7 Oct. 2018. Treatments included non-treated control, low-rate glufosinate plus
CLING (pinene polymer, nonionic surfactant and polydimethylsioxane; Diamond R Fertilizer, Ft. Pierce, FL); high-
rate glufosinate plus CLING; low-rate glufosinate + glyphosate; and high-rate glufosinate + glyphosate arranged in
a completely randomized design. Twenty-five different weed species were identified in these groves before the initial
herbicide application. Percentages of the ground surface area covered with weeds ranged from ~20 to 100% prior to
the first application. In general, all herbicide treatments significantly reduced the percentage of the ground covered
with weeds compared to the non-treated control. The low- and high-rates of glufosinate and CLING and high-rate
glufosinate + glyphosate performed better than the low-rate glufosinate + glyphosate treatments. There were no sig-
nificant differences in crop phytotoxicity among the treatments or crops tested. Minor leaf necrosis and cupping was
occasionally noted on a few lower canopy banana leaves. The percent ground covered by weeds was significantly lower
for all herbicide treatments up to 58 days after the third application. However, by 86 days after the last application,
the percent weed cover was similar among all treatments in the banana, lychee, and guava plantings. Treatments of
glufosinate and glufosinate + glyphosate controlled 25 weed species under south Florida conditions.