Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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AMMONIUM PELARGONATE AS A BIOHERBICIDE FOR PEPPER ROW MIDDLES.
B.A. Scott and M.J. VanGessel, Univ. of Delaware, Georgetown.
ABSTRACT
Weed control in the area between rows of plastic is critical for maximum yield of
fruit and vegetables in plasticulture. A non-selective herbicide plus residual herbicides
are often used to control existing vegetation in "row middles". Since bioherbicides are
non-selective, their utility in plasticulture for this use needs to be investigated. A study
was established to determine the efficacy of ammonium pelargonate for weed control in
peppers grown with black plastic and to determine the necessity of residual herbicides.
This study was arranged as a randomized complete block with four replications.
Treatments consisted of ammonium pelargonate or pelargonic acid applied alone or
with residual herbicides (halosulfuron and metolachlor) applied 3 weeks after pepper
transplant (WAPT). Ammonium pelargonate plus clethodim was also applied at 3
WAPT. Also, ammonium pelargonate was applied alone at 2, 3, or 4-week intervals. A
treatment of paraquat applied at 3-week intervals, a weed free, and an untreated check
were included for comparisons. Treatments were applied at 327 l/ha. Weed heights
were measured prior to individual treatment applications, and pepper injury was
evaluated after each application. Weed control ratings were noted at 4, 8, and 10
WAPT. Pepper harvest was based on the maturation of the weed-free check, and
treatments were harvested at 8 and 11 WAPT.
Addition of residuals herbicides to a single application of ammonium pelargonate
resulted in a significant improvement in weed control and increased yield as compared
to a single application of ammonium pelargonate alone. Antagonism did not result from
the addition of clethodim. Ammonium pelargonate applied at 2-week intervals resulted
in increased broadleaf control and increased yield as compared to the 3 and 4-week
interval treatments. Although overall weed control was greater with the 3-week interval
paraquat treatment than the 2-week interval ammonium pelargonate treatment, yields
did not differ.
Applications of ammonium pelargonate applied at 2-week intervals or a single
application of ammonium pelargonate with residual herbicides is needed in order to
provide effective weed control and prevent yield loss. Grass control with the
bioherbicides alone is minimal unless multiple applications are used.
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