2005 Cucurbit downy mildew alert for PA
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Downy mildew of cucurbits has appeared much earlier than usual in 
southern New Jersey (Cumberland Co.), now is present in Gloucester 
county, and is suspected to be widespread in southern New Jersey at 
this time.  It appears that inoculum was introduced on transplants 
grown in Florida.  It was first reported June 13 in the one planting 
grown from the transplants.  On June 24, the disease was detected 
in another planting about 1 mile northeast of the original planting, 
and on June 29 in a planting about 12 miles east of the first field.

For growers in southeastern Pennsylvania, I suggest application of 
fungicides effective against downy mildew.  A mixture of two 
fungicides with one of them having translaminar systemic activity 
would be best.  Materials and rates are included in the 2005 
Commercial Vegetable Guide.  Translaminar materials that are listed 
for cucurbers include Tanos, Previcur Flex, Cabrio, Pristine, and 
mefenoxam (Ridomil Gold and Flouronil).  Remember that the three 
materials that contain some strobilurin (Tanos, Cabrio and Pristine) 
should be alternated with materials that do not contain a strobilurin.

In all my years at Penn State I have never heard of cucurbit Downy 
Mildew being present this early in the season.  And in New Jersey, 
it is 2 weeks earlier than in 2004.  I expect that growers will 
remember that this disease was a major problem throughout the 
southeast, Mid-Atlantic, and Pennsylvania areas last year.  

Downy mildew symptoms include yellowish to brown angular spots 
that can appear first on crown leaves.  However, younger leaves can 
also be affected and in some cases, entire plantings can be affected 
so quickly (within a few days) and so severely that growers 
frequently report that the fields appear to have symptoms of "frost" 
injury.

Alan MacNab, Plant Pathology Dept., Penn State Univ.
June 30, 2005.