Influence of weather on the efficacy of dichlorprop‐P/MCPA and trihenuron‐methyl

Abstract

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 ED80 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 ED80 dose of dichlorprop‐P/MCPA, whereas the ED80 dose of tribenuron‐methyl increased. For both herbicides, precipitation and high soil temperature increased the ED80 dose, which reflects the importance of rain on herbicide uptake and the effect of soil temperature on plant growth. The R2 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 ED80 doses for Brassica napus L., Chenopodium, album L. and Stellaria media (L.) Vill. generally resulted in increased R2 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.

Temperature‐mediated responses of flumetsulam and metosulam on Raphanus raphanistrum

“…The conclusions will need to be validated in field experiments before commercial adoption, but we expect the findings to be conservative as differences of herbicide activity in growth cabinet studies are often less pronounced than in the field ( Merritt, 1984; Nalewaja & Woznica, 1985). Certainly field experiments by Minkey & Moore (1996) and Lundkvist (1997) conducted over three seasons both found an order of magnitude range in the effective herbicide rate required to achieve weed control, which they attributed to variation in seasonal climatic conditions.…”

“…More effective targeting of dose is a method of reducing the amount of herbicide used while maintaining the level of weed control. It has been shown that, for some herbicides, weather can significantly affect the level of activity ( Hallgren, 1989; Minkey & Moore, 1996; Lundkvist, 1997) and temperature, in particular, has been identified as an important climatic factor affecting herbicide activity ( Caseley, 1987). Controlled environment experiments have demonstrated a strong influence of temperature on the activity of many herbicides including MCPA+dichlorprop ( Jensen & Kudsk, 1988; Kudsk & Kristensen, 1992), chlorsulfuron ( Nalewaja & Woznica, 1985), thifensulfuron ( Kudsk et al ., 1990 ) and ioxynil ( Merritt, 1984).…”

Response of imidazolinone‐tolerant and ‐susceptible volunteer oilseed rape (Brassica napus L.) to ALS inhibitors and alternative herbicides

“…It was not possible to standardise radiation and humidity completely during the trial period. A certain influence of these factors on sulfonylurea performance is reported,26, 27 and may have contributed to the variation observed.…”

Fatores ambientais que afetam a eficácia de herbicidas inibidores da ACCase: revisão

“…De fato, é complexo o entendimento do melhor horário de aplicação e das causas que afetam a eficá-cia dos produtos em campo, em comparação com experimentos realizados com condições controladas (Lundkvist, 1997;Skuterud et al, 1998;Fornarolli et al, 1999;Fausey & Renner, 2001;Penckoswi et al, 2003;Sellers et al, 2003;Cieslik, 2012).…”

“…Especialmente no verão, com o decorrer do dia a radiação global e a temperatura do ar se elevam e a umidade relativa do ar diminui (Lundkvist, 1997;Skuterud et al, 1998;Cieslik, 2012). Em razão dessas interações, deve-se atentar para uma condição de aplicação na qual o conjunto das variáveis ambientais seja favorável a um maior desempenho do herbicida nas plantas daninhas.…”