Temperature and Relative Humidity Affect Weed Response to Vinegar and Clove Oil

Abstract

Nonsynthetic herbicides offer a potentially useful addition to the suite of weed management tools available to organic growers, but limited information is available to guide the optimal use of these products. The objectives of this research were to (1) evaluate the efficacy of clove oil– and vinegar-based herbicides on weeds across multiple states, and (2) assess the potential role of temperature, relative humidity (RH), and cloud cover in explaining inter-state variations in results. From 2006 to 2008, a total of 20 field trials were conducted in seven states using an identical protocol. Seeds of brown mustard were sown and herbicides applied to both mustard and emerged weeds when mustard reached the three- to four-leaf stage. Treatments included clove oil at 2.5, 5, 7.5, and 10% v/v concentrations at 54 L ha−1, and vinegar at 5, 10, 15, and 20% v/v concentrations at 107 L ha−1. Results varied widely across trials. In general, concentrations of at least 7.5% for clove oil and 15% for vinegar were needed for adequate control of mustard. Both products were more effective at suppressing mustard thanAmaranthusspp. or common lambsquarters. Poor control was observed for annual grasses. No significant effects of cloud cover on the efficacy of either product were detected. In contrast, RH was positively correlated with control of brown mustard by both clove oil and vinegar with improved control at higher RH. Temperature had no detectable effect on the efficacy of clove oil, but higher temperatures improved control of brown mustard by vinegar.

Pelargonic Acid for Weed Control in Organic Vidalia® Sweet Onion Production

“…Herbicides derived from natural sources have been investigated for weed control in certified organic crop production with many reports focused on the evaluation of performance on warm-season weeds. These studies evaluated commercial products, rates, times of application, and combinations with mechanical weed control in many cropping systems and regions Brainard et al, 2013;Curran et al, 2004;Johnson et al, 2012). Common conclusions drawn from these studies were that none of the essential oil herbicides provided any residual weed control, small weed size was critical for maximum efficacy, monocots were not controlled, environmental conditions affected herbicide performance, and rates necessary for maximum efficacy made the treatment costly.…”

Plant protection means used in organic farming throughout the European Union

“…Some of them, however, may also have other applications. For example, vinegar is also being used as a herbicide …”

Early physiological response of broccoli leaf to foliar application of clove oil and its main constituents

“…Clove oil shows a contact action on weeds, particularly annual weeds. Its effect is strongly dependent on the species of plant (Boyd and Brennan, 2006), its development phase, thickness of the cuticle on the leaf surface (Bainard et al, 2006), and atmospheric conditions at the time of application (Brainard et al, 2013). All of the aforementioned factors modify the effectiveness of clove oil applied in field conditions (Brainard et al, 2013;Johnson et al, 2013).…”

“…Moreover, it is of interest to determine the dynamics of the herbicidal action induced by clove oil, i.e., the timing of the appearance of the first visible changes on leaves, as well as the rate of deterioration. This timing may be of importance during the foliar application of clove oil, which can be modified by weather conditions, i.e., lower relative humidity causes a decrease in the herbicidal potential of clove oil (Brainard et al, 2013). Modern analytical equipment makes it possible to monitor the course of early changes in plants, both at the level of total metabolism, as well as at a level of specific physiological processes.…”