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Influence of weather on the efficacy of dichlorprop‐P/MCPA and trihenuron‐methyl
Author(s) -
LUNDKVIST A.
Publication year - 1997
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1046/j.1365-3180.1997.d01-58.x
Subject(s) - mcpa , environmental science , forestry , biology , geography , pesticide , agronomy
Summary The influence of weather on the efficacy of dichlorprop‐P/MCPA and tribenuron‐methyl on annual weeds in spritig barley was studied in the field during 4 years at six locations in southern Sweden. The herbicides were applied at one‐eighth to three‐quarters of the full dose at three application times with approximately 6‐day intervals. Weather stations, placed in the experiments, recorded climatic data, Maximum herbicide efficacy was obtained when spraying 1 week after the cotyledon stage with half or three‐quarters of the recommended dose. Dose‐response curves were estimated and the ED 80 doses were calculated. On average, the herbicide dose required to obtain an effect of 80% was about 40% of the recommended dose. The influence of weather was analysed for seven different periods: 7 and 2 days before and after herbicide application, 1 day before and after application, and the day of herbicide treatment. The most pronounced eftects of weather were found for the day of and the day before herbicide application, revealing the strong influence of weather on herbicide uptake and plant metabolism. High air tetnperature and low global radiation during the day of treattnent reduced the ED 80 dose of dichlorprop‐P/MCPA, whereas the ED 80 dose of tribenuron‐methyl increased. For both herbicides, precipitation and high soil temperature increased the ED 80 dose, which reflects the importance of rain on herbicide uptake and the effect of soil temperature on plant growth. The R 2 values were higher in the analyses of dichlorprop‐P/MCPA than of tribenuron‐methyl, indicating that the effect of dichlorprop‐P/MCA was more weather‐dependent than that of tribenuron‐methyl. Separate analyses of the ED 80 doses for Brassica napus L., Chenopodium, album L. and Stellaria media (L.) Vill. generally resulted in increased R 2 values. but otherwise gave results similar to those for the total weed population. Although the analyses revealed significant effects of indivtdual weather factors on herbicide efficacy, it was not possible to discern a consistent and causal relationship between weather and herbicide performance.