NOMINATING PARTY: The United States of America

DATE: APRIL 4, 2013 

BRIEF DESCRIPTIVE TITLE: Response to questions from the U.S.G and MBTOC

bilateral of April 3, 2013 on strawberry fruit

SITE NAME (OPEN FIELD): Strawberry Fruit 

The USG thanks MBTOC for bringing to our attention the Zveibil (2012) and Noling and Cody 

(2012b) studies for control of Macrophominia phaseolina. While there is suggestive evidence 

that alternatives could meet the needs of California strawberry growers, the U.S. government 

believes that the considerations presented to you during our presentation on April 3, 1013 merit 

the present Critical Use Nomination for 2015 as prepared.

The California strawberry researchers have noted the metam-sodium research work on 

Macrophominia from Florida and Israel (Noling and Cody 2012 and Zveibil 2012) and are 

planning dose response or rate finding studies this year with metam sodium. While the research 

work looks promising we would like to recommend caution in weighing these studies because 

there is an extensive body of research that demonstrates that metam-sodium is not effective 

under California conditions. 

The research of Zveibil looked at the viability of Macrophomina based on buried sclerotia and 

strawberry stolons. The study did not look at crop yield or natural populations of 

Macrophominia in the soil. Without yield data it is hard to determine the season long control of 

the different treatments. The Macrophomina research in Florida by Noling and Cody in 2012 

had the number of dead plants/40 foot of row it did not have yield data. Without yield data it is 

hard to determine the season long control of the different treatments. In addition, the treatments 

with Telone C-35 showed statistically similar number of dead plants compared to methyl 

bromide:chloropicrin while we know that under field conditions in California the Telone C-35 is 

treatment is not effective. In Florida, a single cultivar, ‘Festival,’ was tested in a single trial and 

it’s pathogen resistance is unknown under California conditions. The impact of California 

production practices, environmental conditions and cultivars is still unknown when comparing 

these treatments. 

Research in California suggests that metam-sodium may not be effective under local conditions. 

H. Ajwa (personal communication April 3, 2012) stated “In our experiments, we need over 630 

lbs/ac of Na-methyldithiocarbamate to control Macrophomina phaseolina. This is equivalent to 

150 gal/ac of metam sodium (1 gal of metam-Na contains 4.22 lbs a.i). These results are from 

laboratory dose-response experiments using infested plant materials placed in 250 g soil in 

closed jars over 24 hours at 22 oC. The actual LC90 was over 4300 umol a.i/kg soil.” This 

U.S. government would like to point out that this rate is almost twice the legal maximum rate of 

350 lb ai/acre allowed in the U.S. 

Earlier research indicated that metam-sodium did not provide consistent efficacious control

under California conditions. Ajwa and Trout (2004) published work showing that drip applied 
metam-sodium did not provide strawberry fruit yield equivalent to MeBr:chloropicrin. “The 

market yield from the Vapam HL [metam-sodium] treatments relative to MB:CP [67:33] 

treatment ranged between 67% to 86% in Watsonville and between 78% to 99% in Salinas.” 

However, disease in Salinas was very low (<2%); Watsonville had varying incidences of 

Verticillium depending on season (out of 3 seasons). For this study (2004 was prior to the 

“emergence” of Macrophomina in California) the authors conclude that “In our studies, the 

simultaneous drip application of Vapam HL and InLine or CP EC in years 1 and 2 did not 

control verticillium wilt in the severely infested Watsonville soil.” The summary by Nelson et al 

(2000) showed that bedtop applications of metam-sodium were not effective. Shaw and Larson 

(1999) also summarized data to demonstrate that metam-sodium was not effective.

The U.S. is planning further work to test the efficacy of metam-sodium on Macrophomina under 

California conditions. We also plan to gather data on efficacy of the high rate of chloropicrin 

under TIF and its ability to control Macrophomina, Fusarium and Verticillium in commercial 

field applications over time on California strawberries and will apprise MBTOC of its findings.

As you know, regulatory uncertainty is another challenge. County Agricultural Commissioners 

in California will need to render their opinion on whether these high rates of straight chloropicrin 

can be used safely without harm to workers and by-standers. Future regulatory requirements by 

the California Department of Pesticide Regulation (CDPR) for chloropicrin add further to our 

uncertainty. As stated yesterday, CDPR may also change Telone's regulations.

CITATIONS

Ajwa, H. and T. Trout. 2004. Drip application of alternative fumigants to methyl bromide for 

strawberry production. HortSci 39(7):1707-1715. Accessed online on April 4, 2013 at 

http://hortsci.ashspublications.org/content/39/7/1707.full.pdf

Nelson, M. B. Olsen, B. Johnson, and J. Norton. 2000. Results from 1999-2000 USDA IR-4 Trials MBA 

Field Trials in CA and FL strawberries. Accessed online on April 4, 2013 at

http://www.mbao.org/altmet00/3nelson.pdf

Noling, J. W. and Cody, M. 2012. USDA ARS South Atlantic Areawide Project: Large scale field 

demonstrations demonstrations in Florida strawberry 2011-12. Annual International Research 

Conference on Methyl Bromide Alternatives and Emissions Reductions (2012). 

http://mbao.org/2012/Proceedings/27NolingJ%20AreaWide%202012.pdf 

Shaw, D.V. and K.D. Larson 1999. A meta-analysis of strawberry yield response to preplant soil 

fumigation with combinations of methyl bromide-chloropicrin and four alternative systems. 

HortSci. 34(5): 839-845. Accessed online on April 4, 2013 at 

http://hortsci.ashspublications.org/content/34/5/839.full.pdf

Zveibil, A., Mor, N., Gnayem, N., and Freeman, S. 2012. Survival, Host-Pathogen Interaction, and 

Management of Macrophomina phaseolina on strawberry in Israel. Plant Disease 96:265-272. 

http://www.apsnet.org/publications/plantdisease/2012/February/Pages/96_2_265.aspx (link is to 

abstract only).