Posts Tagged ‘pythium pod rot’

Vegetable Disease Update – August 26, 2011

Friday, August 26th, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

With the impending hurricane we will probably see large amounts of rainfall. For vine crops fields with a history of Phytophthora fruit rot it will mean more Phytophthora fruit rot if any marketable watermelon or cantaloupe remain but it will really threaten the pumpkin crop. No fungicide will protect fruit from fruit rot if we get huge amounts of rainfall. Standing water in the fields will be the biggest indicator of possible fruit rot damage. There would be some benefit to protecting foliage with fungicides before the storm arrives if there is time and there is no history of Phytophthora fruit rot. This would be true for many vegetables including vine crops, tomatoes, and others. If there is no Phytophthora fruit rot present in a pumpkin field, fungicides such as Presidio, Ranman, Revus or Forum plus a fixed copper could be considered to suppress Phytophthora fruit rot, if Phytophthora spores moving in water from other fields should be introduced. Fruit have to be covered for the materials to have a hope of having an effect.

For other vegetables such as tomatoes, peppers and other fruiting vegetables that may be planted for late harvest fungicide applications should be made before the rains arrive not after. Prevention is the key to control. If the label allows, adjuvants that help products adhere to the plants should be considered. Spreader-stickers would be encouraged if the crop and label warrant it.

In crops where cottony leak caused by Pythium could cause crop loss, such as snapbeans and lima beans, application of one of the phosphonate fungicides such as ProPhyt or Phostrol would be suggested at maximum rates, or Ridomil Gold/Copper on snapbeans only. There is a 24c label for Ridomil Gold/Copper (2.0 lbs/A) in DE, MD and VA for cottony leak on snapbeans. Lima bean growers will want to scout carefully once this storm clears out for downy mildew. Wet soil and cool temperatures will favor downy mildew infection.

Cucurbit downy mildew is present on pumpkin now in the sentinel plot in Newark in New Castle County. This is the first report of downy mildew on pumpkin. It has probably been there for several days. Growers should continue to apply fungicides for leaf diseases including downy mildew.

 

Sweet Corn and Lima Bean Disease Update

Friday, September 4th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Sweet Corn
See the article on stalk rots in this issue for pictures of Diplodia ear rot on sweet corn. Nothing to do for it except work in the corn stalks at the end of the season. Chalk this one up to wet weather.

Lima Beans
Pythium pod rot can be a problem when we have wet, warm weather, like what occurred last week and the week before. Pythium is soil born and moves into pods that are touching the soil and can then spread to other plant parts under ideal conditions. It can be more of a problem in snap beans but does occur sporadically in lima beans as well. It is extremely hard to predict when and where it will occur unless the field has a history of Pythium problems. Ridomil Gold/Copper has a 24c label for use on snapbeans in DE, MD and VA. Application should be made before the pods develop and touch the soil surface. The phosphorus acid fungicides that are labeded on beans, such as Prophyt, would be another product to try if the situation warranted it.

Pythium pod rot on lima bean

Pythium pod rot on lima bean. Note the white cottony growth.

New Product Labeled for Lima Bean Downy Mildew
I just received notice that BASF labeled Forum (dimethomorph), formerly Acrobat, for use on succulent beans for downy mildew. This was a surprise and I had to look at my data to see how it did. It was tested in 2001 and performed very well. It controlled downy as well as the standard Ridomil Gold/Copper. I have the opportunity to look at it again this year since I just applied the treatments for a downy mildew test in Georgetown on Wednesday and have included Forum. Forum is also very active on Phytophthora capsici, which causes lima bean pod rot and is another problem that has been troublesome for lima bean growers. The rate is 6 fl oz/A for downy mildew which is also the recommended rate for Phytophthora capsici fruit rot control on cucurbits. I’m not sure how much material is available, but Forum is another tool in the toolbox. That gives us Ridomil Gold/Copper, Phostrol and other phosphorus acid fungicides, Headline, and Forum for use on baby limas for downy mildew.