Efficacy of methyl iodide and synergy with chloropicrin for control of fungi

Abstract

Efficacy of soil fumigation with methyl bromide and methyl iodide against Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Gliocladium virens, Phytophthora citricola, Phytophthora citrophthora, Pythium ultimum, Rhizoctonia solani and Verticillium dahliae was determined in laboratory experiments in closed fumigation chambers. Pythium ultimum was the most sensitive fungal species with EC50 values for methyl bromide and methyl iodide of 15.5 and 8.6 µM, respectively. R solani was the least sensitive with EC50 values of 253.4 and 161.4 µM for methyl bromide and methyl iodide, respectively. Relative potency ([methyl bromide]/[methyl iodide]) values ranged from 5.2 for P citricola to 1.5 for F oxysporum. Methyl iodide was 2.7 more efficacious than methyl bromide averaged over all fungal species. Methyl bromide/chloropicrin and methyl iodide/chloropicrin applied jointly were 2.2 and 2.8 times more efficacious, respectively, against F oxysporum than when the compounds were applied singly. Combining methyl bromide and methyl iodide with chloropicrin resulted in a significant synergistic increase in activity against F oxysporum. © 2000 Society of Chemical Industry

Enzyme activities in agricultural soils fumigated with methyl bromide alternatives

“…Iodomethane (Midas) can be as effective as MeBr, and it is not as likely to deplete ozone because Midas is photolyzed before it reaches the stratosphere (Solomon et al, 1994). The dilution of Midas with CP can decrease costs for this fumigant and increase efficacy due to synergy with CP (Hutchinson et al, 2000).…”

Fumigant dosages below maximum label rate control some soilborne pathogens

“…The largest slope at the inflection point of the curve (b value) indicated that F. oxysporum and R. solani have greater susceptibility to pure MI (MI:Pic, 98:2) than to the other fumigants (table 2). Early doseresponse studies evaluated the efficacy of pure MI and MBr to control a range of soilborne pathogens and found P. ultimum to be the most sensitive and R. solani to be the least sensitive (Hutchinson et al 2000;Ohr et al 1996), and only partial mortality of F. oxysporum and V. dahliae was achieved with these fumigants. Other studies have reported that MI and MBr controlled nematodes, including citrus nematode (Becker et al 1998;Hutchinson et al 1999;Luo et al 2010).…”

“…Most MBr efficacy studies have assessed the dose response using pure MBr (98%) and found this compound very effective against a wide range of pests; however, the analog compound, MI, was found to be as effective as or more effective than MBr (Becker et al 1998;Hutchinson et al 1999;Hutchinson et al 2000;Ohr et al 1996;Zhang et al 1997). In this study, the mixed fumigants MBr:Pic (50:50) and MI:Pic (50:50) both controlled T. semipenetrans, P. ultimum and F. oxysporum, but MI:Pic was more effective in controlling R. solani compared to MBr:Pic (tables 3 and 4).…”

“…Laboratory dose-response studies -which determine the relationship between the amount of fumigant and its effect on an organism -have indicated that MI is as effective as or more effective than MBr to control soilborne pathogens and weeds (Becker et al 1998;Hutchinson et al 1999;Hutchinson et al 2000;Luo et al 2010;Ohr et al 1996). MI has a synergistic relationship with chloropicrin under controlled conditions, similar to the relationship between MBr and chloropicrin (Hutchinson et al 2000). However, in March 2012, all MI registrations were withdrawn by the manufacturer.…”

“…Commercial fumigant formulations may contain several active ingredients; however, the efficacy rate is typically determined for a single active ingredient for a specific target pathogen (i.e., control of certain fungal pathogens, nematodes and weeds) and specific crops. However, the synergistic relationship caused by mixing two fumigants can enhance efficacy compared with fumigants applied alone (Hutchinson et al 2000).…”