ASHS Press Releases

American Society for Horticultural Science

  • Increase font size
  • Default font size
  • Decrease font size
Home HortTechnology Brassicaceae Cover Crops Tested as Methyl Bromide Alternative
E-mail Print

EAST LANSING, MI—When environmental awareness increases in agriculture, regulations change. In 2005 the use of methyl bromide to manage soilborne diseases was phased out. It is, however, still being used based on critical use exemptions, but it these exemptions will not last forever. For production of many vegetables, particularly cucurbit crops of muskmelon and cucumbers, environmentally safe alternatives are not readily available, and growers continue to rely on the critical use exemptions.

Researchers Victoria Ackroyd and Mathieu Ngouajio conducted a 2-year study in southwestern Michigan to determine the impact of using cover crops from the Brassicaceae family on 'Athena' muskmelon crops. With a grant funded in part by the U.S. Department of Agriculture's Methyl Bromide Transitions Program, the scientists examined the effects of using oilseed radish, oriental mustard, and yellow mustard as green manures on muskmelon and cucumber germination and stand counts. "Cover crops in the Brassicaceae family have been shown to decrease plant pathogens populations in the soil, while cover crops in general provide added benefits in a production system, decreasing erosion, aiding nutrient cycling, and preserving soil quality and weed suppression," explained Ngouajio.

In their field studies, the researchers found that the use of the three cover crops reduced the direct-seeded muskmelon stand count as well as the rate of transplant survival. The control and methyl bromide stand counts were greater than 85% while the cover crop treatments were less than 41%. Oilseed had the greatest effect with 0% muskmelon stands in both years. Using transplants improved development but was still unacceptable at 45% to 50% stand count.

Lab studies on muskmelon, cucumber, and honeydew seeds exposed to extracts of oilseed in both dehydrated and non-dehydrated form showed varying results, with all three crops with muskmelon being least sensitive, followed by cucumber and honeydew. The non-dehydrated extract had greater impact on germination than the dehydrated extract.

The research team concluded that for muskmelon production under Michigan growing conditions, spring-planted oilseed radish and mustard cover crops will not fit well into the cropping system. "Cover crop residue will typically require more time to release phytotoxic compounds before cash cropping," they wrote, noting that an alternative to spring planting of the cover crops could be late summer or fall planting.


The complete study and abstract are available on the ASHS HortTechnology electronic journal web site:

Founded 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


Original Article:

Brassicaceae Cover Crops Affect Seed Germination and Seedling Establishment in Cucurbit Crops
Victoria J. Ackroyd and Mathieu Ngouajio
HortTechnology 21:525–532. [Abstract][Full Text][PDF]

Corresponding author. E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it