Posts Tagged ‘basil downy mildew’

Downy Mildew Infecting Basil

Friday, July 20th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Basil downy mildew has been reported in Maryland this last week in a home garden (it was previously in other mid-Atlantic states). Growers in the region should check their plants carefully for disease symptoms. Products that are labeled for Basil Downy mildew are Pro-Phyt, Fosphite, and K-Phite. These products have demonstrated some efficacy on this disease in trials. One organic option is Actinovate, which is OMRI approved.

Downy mildew infected basil: lower leaf sporulation and yellowing on the upper leaf surfaces.

Vegetable Disease Update – September 16, 2011

Friday, September 16th, 2011

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

Lima bean downy mildew was found by a CCA and confirmed on Wednesday from a field of ‘C-elite’ near Galena, MD. Growers need to be scouting carefully and applying fungicides as needed. If seen in the field apply either Ridomil Gold/Copper 2.0 lbs/A or ProPhyt (3.0 pts/A). See the 2011 Delaware Commercial Vegetable Production Recommendations for other fungicide choices as well as last week’s WCU for more detailed information.

Basil downy mildew was found in New Castle County this week. Any specialty crops growers might want to protect basil with one of the phosphorus acid products, such a ProPhyt, at this time.

Powdery and downy mildew are widespread in cucurbits especially pumpkins and winter squash at this time. Maintain fungicide programs until fruit develop fully.

Unfortunately Phytophthora fruit rot is very prevalent on a number of cucurbits especially pumpkin at this time. The excessive rainfall just made a bad problem worse. A few growers have asked about dipping fruit in a 5-10% bleach solution or using Zerotol to prevent fruit rot. My experience has been that is not effective if the fruit are infected in the field. You may get reduced spread in a bin but it will not control Phytophthora fruit rot.

There were a few reports of late blight in New York and Connecticut this week, but nothing in the Mid-Atlantic to worry tomato growers so far. To track the progress of late blight in the US you can go to http://usablight.org

Vegetable Disease Updates – August 5, 2011

Thursday, August 4th, 2011

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

Basil Downy Mildew
Basil downy mildew has been seen in nearby NJ. Any sweet basil growers should be scouting for this disease. Phosphite fungicides such as Prophyte have shown the best efficacy for controlling basil downy mildew.

Cucurbit Downy Mildew
Cucurbit downy mildew continues to be seen at low levels in commercial cucumber fields. The dry hot weather has been helping the fungicides to keep it in check. So far we have not seen it move into other cucurbits such as pumpkin. Keep scouting and check the 2011 Commercial Vegetable Productions Recommendations for fungicide suggestions. Once the cooler weather returns, and hopefully some rainfall, look for this disease to increase. Keep up with preventative fungicide applications.

Late Blight
We just received a confirmed report of late blight from Ann Arundel County in MD and in New Brunswick, Canada. Keep on the lookout for this disease on tomato and potato.

Watermelon
Cercospora leaf spot was diagnosed on watermelon last week. Cercospora leaf spot symptoms occur primarily on foliage, but petiole and stem lesions can develop when conditions are highly favorable for disease development. Fruit lesions are not known to occur. On older leaves, small, circular to irregular circular spots with tan to light brown lesions appear. The number and size of lesions increases, and eventually they coalesce and cause entire leaves to become diseased.

Lesion margins may appear dark purple or black, and may have yellow halos surrounding them. Severely infected leaves turn yellow, senesce, and fall off. On watermelon, lesions often form on younger rather than older foliage. Cercospora leaf spot can reduce fruit size and quality, but economic losses are rarely severe. Fungicides such as chlorothalonil (Bravo) and mancozeb including Gavel, as well as the triazole fungicides such as Inspire Super and strobilurins (Cabrio and Quadris) should provide good control of Cercospora leaf spot. As wilthall vine crops be sure to apply in enough water to get good coverage, usually a minimum of 15 gal/A.

Downy Mildew on Basil

Friday, July 1st, 2011

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Basil downy mildew has been reported in two locations in Maryland this week. It was confirmed in Ellicott City, and we received a separate report in Calvert County. Growers should check their plants carefully for disease symptoms. Products that are labeled for Basil Downy mildew are Pro-Phyt, Fosphite, K-Phite, and Quadris. These products have some efficacy on this disease in trials.

 

Downy mildew infected basil: lower leaf sporulation and yellowing on the upper leaf surfaces

 

Downy Mildew Updates – June 24, 2011

Friday, June 24th, 2011

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Basil Downy Mildew
Downy mildew on basil has been confirmed in Dunkirk, MD (Calvert County between the DC metro area and Southern Maryland). The infected plants are in a homeowner’s yard, but commercial growers should be on the lookout.

Cucurbit Downy Mildew
As a result of slightly more favorable conditions, Downy mildew on cucurbits is moving northward. Within the last week there have been three reports of downy mildew on CUCUMBER in North Carolina, including one on the border of Virginia. The Cucurbit Downy Mildew forecaster says that disease spread is possible in the mid-Atlantic region, including areas in southern Maryland, the eastern shore, and in Delaware. Scout plants rigorously and monitor the CDM website http://cdm.ipmpipe.org/

Lower leaf surface of a cucumber leaf infected with downy mildew. Courtesy of Gerald Holmes, Valent USA Corporation, Bugwood.org

Downy mildew symptoms on upper leaf surface of cucumber.

Downy mildew symptoms on watermelon, note the differences.

 

Basil Downy Mildew Found in Delaware

Friday, August 14th, 2009

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

Herb growers should be on the lookout for basil downy mildew. It is now showing up in the region, including Delaware. There was some found earlier in the summer on transplants but now it is spreading by airborne spores called sporangia. Often the symptoms appear in the upper canopy as light yellow blotches and it is difficult to see in the early stages. These light blotches continue to turn yellow, brown then black. The fungus can be seen on the lower leaf surface as fine tufts of fungus growth as well as the sporangia that blow in the wind and spread the disease. The only fungicides that are labeled are the phosphorus acid or phosphonate fungicides that have herbs on the label which include Prophyt and K-Phite. Increase air circulation and remove badly infected plants. There is more info on the Plant Clinic website http://ag.udel.edu/extension/pdc/index.htm. The following photos are courtesy of Meg McGrath, Cornell University, Riverhead Long Island.

basil downy mildew on upper leaf surfaceYellowing on upper leaf surfaces

basil downy mildew on lower leaf surfacePathogen growth and spores on lower leaf surfaces.

basil downy mildew sporulationClose-up of pathogen growth.