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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

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 http://list.msu.edu/archives/mich-organic.html