Are pre-spraying growing conditions a major determinant of herbicide efficacy

• Published in: Weed research Vol. 47; no. 5; pp. 415 - 424
• Main Authors: RIETHMULLER-HAAGE, I, BASTIAANS, L, KEMPENAAR, C, SMUTNY, V, KROPFF, MJ
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-10-2007; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Biological and medical sciences; Brassica napus; Chemical control; Chenopodium album; dose-response curve; environmental-factors; Fundamental and applied biological sciences. Psychology; glyphosate; growth; light-intensity; Parasitic plants. Weeds; Persicaria maculosa; Phytopathology. Animal pests. Plant and forest protection; rates; Senecio vulgaris; Solanum nigrum; uptake; weather; weather conditions; Weeds; wheat; Persicaria maculosa; dose- response curve; Environmental factor; Physical environment; Compositae; Dose activity relation; Absorption; Cruciferae; Dicotyledones; Weed science; Angiospermae; Solanaceae; Senecio vulgaris; Atmospheric condition; weather conditions; Weed; uptake; Determinant; Treatment efficiency; Spraying; Pesticides; Herbicide; Chenopodiaceae; Chenopodium album; Solanum nigrum; Brassica napus; Spermatophyta; Oil plant (vegetal); Chemical weed control
• ISSN: 0043-1737; 1365-3180
• DOI: 10.1111/j.1365-3180.2007.00584.x

To evaluate the effect of pre-spraying growing conditions on herbicide efficacy, two years of experimentation were conducted in which Persicaria maculosa plants were exposed to different light intensities for 1-4 days before metribuzin treatment. Specific leaf area, rather than plant growth rate or plant size, was the only parameter that correlated well with herbicide efficacy in both years of experimentation. The negative relationship between the ED₅₀ and the specific leaf area indicates that leaf characteristics might be an important determinant of herbicide efficacy, for instance through an effect on herbicide uptake. In the third year of experimentation this hypothesis was further investigated by raising six cohorts of weed plants at a 1-week interval and thus exposing them to a range of weather conditions. Clear relationships between uptake and herbicide efficacy were found for a combination of four plant species (Solanum nigrum, Senecio vulgaris, Chenopodium album and Brassica napus) and two herbicides (phenmedipham and bentazone). For phenmedipham, uptake was negatively correlated with global radiation and positively correlated with relative humidity. For the herbicide bentazone the opposite was found. These results were not species-specific. This study shows the importance of the sensitivity of herbicide x species combinations and indicates that pre-spraying weather information is relevant for the development of reduced dose rate recommendations.