TITLE:
Herbicidal Effects of Fungicides on Arable Weeds
AUTHORS:
Henning Nordmeyer, Tobias Koch
KEYWORDS:
Chenopodium album; Dose Response; Epoxiconazole; Fungicide Treatments; Lamium purpureum; Nontarget Effects; Plant Bioassay; Weed Species
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.1,
January
9,
2014
ABSTRACT: In the present study, the herbicidal effects of
two fungicides with the active ingredients expoxiconazole, fluxapyroxad, pyraclostrobin and fenpropimorph on the
two arable weeds Lamium purpureum L.
and Chenopodium album L. were
investigated. The experiments were conducted in a climate chamber under defined
conditions. Sowing pods were prepared and plants at the cotyledon leaf stage
were pricked out in test pods. Fungicides were applied at six application
rates: 0%, 12.5%, 25%, 50%, 100% and 200% of the maximum registered dose rate
in Germany. Seven days after application, the first assessment was conducted,
regarding growth stage, quantity of plants and visible plant damage. Fourteen
days after application, the second and final assessment was conducted,
regarding growth stage, quantity of plants, visible plant damage and the fresh
weight of the plants. There were herbicidal effects of the fungicides, which were presumably due to the active ingredient
epoxiconazole. Epoxiconazole has effects on enzymes that are dependent on
cytochrome P-450 and inhibits sterol biosynthesis and probably gibberellin
synthesis. By doing so, these fungicides have similar effects to plant growth
regulators. Weed species showed differential sensitivities, contractions and
growth inhibition and ED50-values were calculated. Notwithstanding
the probably minor relevance of the present results in agricultural practice,
some effects on arable weeds might result if fungicides are applied at an early
growth stage in the field. In some cases, the crop-weed competition could be shifted to the benefit
of the crop. Nevertheless, the results are interesting for the field of weed
research and for the assessment of the ecotoxicology of fungicides.