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Articles on Organic & Sustainable Farming
(June 24, 2010)


Cucurbit downy mildew spore counts increase in Monroe County - fungicide sprays recommended for all cucumbers across the state, by Mary Hausbeck, Plant Pathology, MSU
posted on June 22, 2010

The spore trap tapes from last week are being counted and show an increase in Monroe County. This increase in spore counts and the finding of downy mildew in a Canadian field require immediate action by all Michigan cucumber growers. Spray downy mildew fungicides now! See fungicide recommendations accompanying this article.

Michigan pickle growers have battled downy mildew, incited by the water mold, Pseudoperonospora cubensis, for five consecutive years. Downy mildew is well-known for causing catastrophic losses in a brief period of time. Unprotected foliage can become completely infected and appear to be frosted within 10 days of initial infection. This downy mildew pathogen is resistant to commonly used fungicides including Ridomil Gold-based products and the strobilurin fungicides (i.e. Cabrio, Quadris, and Flint). Results from our 2005-09 research identified a limited number of fungicides that are effective, but must be applied every five to seven days when the weather favors disease.

To view entire article and read more on research being done on this topic visit the MSU Vegetable CAT Alert newsletter. Visit, http://ipmnews.msu.edu/vegetable/ to read the entire article. The pdf is also available.


Onion downy mildew confirmed in the state, by Mary Hausbeck, Plant Pathology, MSU
posted on June 22, 2010

Downy mildew on onion has been confirmed in Michigan. Although the disease was detected on only one plant, this pathogen can multiply rapidly and spread through a growing region if left untreated.

Downy mildew of onion is caused by the pathogen, Peronospora destructor, and first infects older leaves, occurring as pale, elongated patches that may have a grayish-violet fuzzy growth. Symptoms of the disease are best recognized when dew is present in the morning. Infected leaves become pale green, then yellow and can fold over and collapse. Premature death of onion leaves reduces bulb size. The downy mildew pathogen initiates infection during cool temperatures (less than 72F) and wet conditions. Multiple infection cycles can occur in a season. Spores are produced at night and are easily blown long distances in moist air. They can germinate on onion tissue in one and a half to seven hours when temperatures are 50F to 54F. High daytime temperatures and short or interrupted periods of humidity at night can prevent sporulation. Overwintering spores, called oospores, can form in dying plant tissue and can be found in volunteer onions, onion cull piles, and in stored infected bulbs. Oospores have thick walls and a built-in food supply so they can withstand unfavorable winter temperatures and survive in the soil for up to five years.

To view entire article and read more on research being done on this topic visit the MSU Vegetable CAT Alert newsletter. Visit, http://ipmnews.msu.edu/vegetable/ to read the entire article. The pdf is also available.


New articles are published on the MSU Fruit CAT Alert newsletter. Visit our web site, http://ipmnews.msu.edu/fruit/ to read the articles. Weve also posted the printable pdf version.

Topics include:

Controlling Japanese beetles in fruit crops
Tree fruit news
Emerging pest alert: The apple flea weevil Control of American brown rot
Management of bacterial spot on peach and nectarines
Michigan Cider Makers Guild summer meeting
Small fruit news
Protect grape clusters from all major grape diseases at this time
Other news
Regional reports
Weather news
If you would like to access a searchable archive of the all the previous Mich-Organic listserv postings copy this URL and paste in your browser address field http://list.msu.edu/archives/mich-organic.html