Response of processing carrot to metribuzin on mineral soils in Nova Scotia

Abstract

. 2004. Response of processing carrot to metribuzin on mineral soils in Nova Scotia. Can. J. Plant Sci. 84: 669-676. Metribuzin was examined as an alternative to linuron and prometryn when prometryn-treated processed carrot in Atlantic Canada in the 1990s could not be exported to the United States, where prometryn was not registered for this crop. Field studies demonstrated that 280 g ha -1 metribuzin applied after the three-leaf crop stage resulted in only minor injury and no yield loss for both a metribuzin-tolerant (Caro-Choice) and -sensitive (Dominator) cultivar. Metribuzin applied either pre-or postemergence controlled two Matricaria species, chickweed [Stellaria media (L.) Vill.] and shepherd's-purse [Capsella bursa-pastoris (L.) Medik.], equivalent to approved prometryn and linuron treatments. Controlled environment studies were conducted to examine the effect of crop growth stage, temperature and soil pH on metribuzin injury to carrot. Differential tolerance between the two cultivars occurred only up to the three-leaf stage. Under controlled environment conditions, carrot injury to metribuzin increased threefold as soil pH increased from 6.5 to 7.4. There was little injury when metribuzin was applied postemergence under cool temperatures (15/10°C), but injury increased from 25 to 85% under 20/15°C and 30/25°C regimes. Lower temperatures and naturally low pH soils contribute to carrot tolerance to metribuzin under Nova Scotia conditions. Based on this research, metribuzin at 280 g ha -1 applied after the three-leaf stage of carrot was approved for use in the Atlantic provinces. Medik.] comme le font la prométryne et le linuron. Les auteurs ont effectué des études en milieu contrôlé pour vérifier les effets du stade de croissance, de la température et du pH du sol sur les dommages que la métribuzine cause à la carotte. La différence entre les deux cultivars au niveau de la tolérance ne se manifeste que jusqu'au stade de la troisième feuille. En milieu contrôlé, le relèvement du pH du sol de 6,5 à 7,4 triple les dommages imputables à la métribuzine. L'application du pesticide après la levée par temps frais (15/10°C) entraîne peu de dommages, mais ceux-ci augmentent de 25 % à 85 % aux températures de 20/15°C et de 30/25°C. Une température plus basse et un faible pH naturel du sol concourent à accroître la tolérance de la carotte à la métribuzine dans les conditions normales en Nouvelle-Écosse. Compte tenu de ces résultats, on a approuvé l'application de 280 g de métribuzine par hectare au stade de la troisième feuille de la carotte dans les provinces de l'Atlantique.

Selectivity of Metribuzin in Postemergence of Culture of Carrot

“…Studies have shown that tolerance to metribuzin may vary with genotypes cultivated and with edaphoclimatic conditions (Bellinder et al, 1997;Jensen et al, 2004). Possibly, cultivar Nantes is tolerant to the tested doses of the herbicide.…”

“…The most widely used method for weed control in large-scale carrot crops has been the application of herbicides (Konieczka et al, 2009;Sasnauskas et al, 2012) and linuron is the main product recommended (Jensen et al, 2004). However, this herbicide has not shown good control of some weed species, which has encouraged producers to seek new alternatives, such as metribuzin, which has a broader range of action.…”

“…Metribuzin doses must vary according to the soil type and pH (Oukali-Haouchine et al, 2015), as well as the temperature, which increases the degradation of this molecule (Zhang et al, 2014) and the cultivars tolerance (Jensen et al, 2004). In addition, the time of application of the herbicide may vary according to the stage of the plant.…”

“…In addition, the time of application of the herbicide may vary according to the stage of the plant. These two variables (dose and time of application) are crucial for the presence or absence of intoxication (Jensen et al, 2004(Jensen et al, , 2006Golian et al, 2014). Poisoning caused by metribuzin has been reported mainly when applied in postemergence of the crop and in stages of less than five leaves (Jensen et al, 2004).…”

“…Milder temperatures may increase tolerance to metribuzin in carrot crops, bearing higher doses than recommended (Phatak and Stephenson, 1973;Al-Khatib etal., 1997). As for selectivity, it is variable with the cultivars (Jensen et al, 2004).…”