Fumigant dosages below maximum label rate control some soilborne pathogens

Abstract

The activity of commercial soil fumigants on some key soilborne pathogens was assessed in sandy loam soil under controlled conditions. Seven soil fumigants that are registered in California or are being or have been considered for registration were used in this study: dimethyl disulfide (DMDS) mixed with chloropicrin (Pic) (79% DMDS and 21% Pic), Tri-Con (50% methyl bromide and 50% Pic), Midas Gold (33% methyl iodide [MI] and 67% Pic), Midas Bronze (50% MI and 50% Pic), Midas (MI, active ingredient [a.i.] 97.8%), Pic (a.i. 99% trichloronitromethane) and Pic-Clor 60 (57% Pic and 37% 1,3-dichloropropene [1-3,D]). Dose-response models were calculated for pathogen mortality after 24 hours of exposure to fumigants. Overall, the tested fumigants achieved good efficacy with dosages below the maximum label rate against the tested pathogens. In this study, Pythium ultimum and citrus nematode were sensitive to all the fumigants and Verticillium dahliae was resistant. For most fumigants, California regulations restrict application rates to less than the maximum (federal) label rate, meaning that it is possible that the fumigants may not control major plant pathogens. This research provides information on the effectiveness of these alternatives at these lower application rates. The results from this study will help growers optimize application rates for registered fumigants (such as Pic and 1,3-D) and will help accelerate the adoption of new fumigants (such as DMDS) if they are registered in California.C hemical fumigants control soilborne pathogens and weeds in many crop production systems. Methyl bromide (MBr) was the most commonly used preplant soil fumigant during the last 40 years. The California strawberry industry -valued at approximately $2.6 billion in 2014 (California Strawberry Commission 2016) -was highly dependent on MBr soil fumigation to control various soil pests and to maintain high productivity, as there are no disease-resistant strawberry varieties. MBr effectively controls a wide range of soilborne pathogens, diffuses through soil effectively and dissipates from soil rapidly. However, MBr has been phased out under the Montreal Protocol because it is an ozone-depleting compound.As a result of this phaseout, which began in 2001, the use of alternative fumigants such as 1,3-dichloropropene A dose-response study of soil fumigants found that some soilborne pathogens can be controlled at application rates that are lower than the maximum label rate.

Impact of Cover Crop Usage on Soilborne Diseases in Field Nursery Production

“…Chemical fungicides have been the most reliable line of defense to prevent losses due to soilborne pathogens [10]. For over 40 years, soil fumigation with methyl bromide was the standard pre-plant treatment for management of soilborne pathogens in a wide range of agricultural crops [11]. When methyl bromide was phased out in the early 21st century, metam sodium or sodium N-methyldithiocarbamate fumigants and post-planting fungicides had to be used to manage soilborne diseases [12].…”

Fire Ant Venom Alkaloids: Possible Control Measure for Soilborne and Foliar Plant Pathogens

“…Chemical fungicides [13] and bactericides [12] are the primary methods used to control plant pathogens in cropping systems globally. Additional techniques available to manage losses to plant pathogens include proper sanitation [14,15], use of resistant varieties/cultivars [14], incorporation of cover crops [3,15], soil solarization [7], biofumigation [16,17], organic amendments [3], soil fertility enhancement [18], soilless culture [19], and biological products [20][21][22][23][24]. The use of a single approach to plant pathogen management is rarely effective.…”

Method Validation and Dissipation Behaviour of Dimethyl Disulphide (DMDS) in Cucumber and Soil by Gas Chromatography-Tandem Mass Spectrometry

“…Soil-borne disease and pests are becoming a significant issue in vegetable production worldwide [1]. In the vegetable production system, chemical fumigants have been used to control soil-borne disease and pests for a long time [2]. Methyl bromide (MeBr) was the only chemical fumigant that was used extensively in the past 40 years to control soil-borne disease and pest in agriculture [3,4].…”