Contact: Michael W. Neff
American Society for Horticultural Science
Methyl bromide alternatives for California strawberry nurseries
Researchers find alternative fumigants effective in weed control
SALINAS, CA—Since around 1960, methyl bromide
(MB) has been the foundation for soilborne disease and weed control in
California strawberries. MB, classified as a Class I stratospheric
ozone-depleting chemical, has been phased out since 2005, but is still
being used in strawberry production under a critical-use exemption.
Strawberry production is important to California's economy; the state
leads the U.S. in strawberry production. In 2006, the fruit harvest
yielded a value of $1.2 billion, and accounted for 79% of the total
U.S. gross sales.
diversity of climates in California along with the use of this
fumigant, permits the production of high-quality runner plants, which
are propagated in virus-free growing facilities called "screenhouses".
Plants are reared first in a low-elevation facility during the warm
early season, and then moved to higher-elevation facilities for cool,
late-summer conditions. This process ensures that strawberry plants
will be ready to transplant into fruit fields by early fall.
A research study published in the American Society for Horticultural Science journal
evaluated the effectiveness and cost efficiency for weed control in
lower- and higher-elevation nurseries with MB-alternative fumigants.
Steven A. Fennimore, Milton J. Haar, Rachael E. Goodhue, and
Christopher Q.Winterbottom noted that weed control in strawberry
nurseries is more difficult than in fruiting fields. "Because weed
control methods such as mulches used in fruit fields can't be used in
nurseries, fumigants are one of the most important weed control tools
available for strawberry nursery fields", the team explained.
weed control in the study consisted of three methods: weed seed
viability, weed density counts, and timing of hand-weeding inputs by
crews. Strawberry and weed seed samples were treated with the
alternative fumigants to determine the potential for strawberry and
weed seed to survive in the nursery fields. Fumigant effectiveness was
studied in fields treated with the combination of MB plus Pic,
iodomethane (IM) plus Pic, and control fields. Additional treatments
tested were 1,3-dicloropropane (1,3-D) plus Pic followed by dazomet,
and Pic followed by dazomet. Overall, there were few to no differences
in weed control between IMPic, 1,3-D Pic followed by dazomet, Pic
followed by dazomet, and MBPic. Relative to the control fields,
hand-weeding times were reduced in all fields that had been fumigated.
main difference between fumigating with the different methods was
material cost. The researchers explained that, because current prices
were used to calculate hand weeding and treatment costs, these prices
will change over time and may become more equitable given different
The study results showed that that fumigating
with MB is currently much cheaper than using IM. On the basis of weed
control, all of the alternative fumigant treatments were acceptable
replacements for MB.
The complete study and abstract are available on the ASHS
HortSciencehttp://hortsci.ashspublications.org/cgi/content/abstract/43/5/1495 electronic journal web site:
in 1903, the American Society for Horticultural Science (ASHS) is the
largest organization dedicated to advancing all facets of horticultural
research, education, and application. More information at: http://ashs.org