Rutgers Cooperative Extension
Cucurbit downy mildew has been confirmed on cucumber in Salem County, New Jersey. This is the first report of cucurbit downy mildew in the state this growing season. The pathogen has also been found on watermelon in DE and MD and on cucumber in PA.
All cucurbit growers should consider adding a downy mildew specific fungicide to their weekly fungicide program. For more information on the control please see the 2015 Commercial Fungicide Recommendations Guide.
Anthracnose and Alternaria leaf blights are showing up in cucurbit crops. Weather conditions in the region continue to be ideal for disease development across all vegetable crops. The regular rainfall and high humidity that have plagued the region only acts to exacerbate problems. All cucurbit growers should be on high alert for foliar diseases such as anthracnose and Alternaria as well as downy mildew. Anthracnose and Alternaria produce distinct circular spots on infected leaves, and in most cases, symptoms begin on the older leaves.
Symptoms of anthracnose on infected cucumber leaf.
With Alternaria, diagnostic concentric black rings will be develop within the spots. With Anthracnose, black setae (hair-like projections) will develop on the veins of infected tissue on the underside of leaves.
Anthracnose and Alternaria are easily controlled with weekly protectant fungicides such as chlorothalonil and mancozeb as long as they are applied prior to the arrival of the pathogen. Control of downy mildew will require downy mildew specific fungicides. As long as these weather conditions persist all growers need to remain on strict weekly protectant fungicide programs and be scouting on a daily basis. Organic growers can apply copper and other labeled products to help suppress development of these diseases.
Complete foliar coverage is critically important for the control these diseases.
For more information on the control of anthracnose and Alternaria leaf blight in cucurbit crops please see the 2015 Commercial Vegetable Production Guide.
Look for it in the Vegetable Crops Edition Sidebar (shown right).
As with Rutgers, other universities in the mid-Atlantic region share important information with vegetable growers in their respective states. Much of this information is extremely useful for conventional and organic vegetable growers in New Jersey. All of this information is shared, along with our own, through our Plant and Pest Advisory website! Important disease alerts and information is fed into our Plant and Pest Advisory from Delaware, Pennsylvania, and Virginia through the links that appear in the right side bar. All you need to do is click on the link!
Cucurbit downy mildew has been found on cucumber in Southeastern Pennsylvania in Berks county. Cucurbit downy mildew has also been reported in cucumber in Western NY as well as Eastern MD and DE on watermelon this past week. Weather conditions in the region have been ideal for its development. All cucurbit growers who have not initiated a weekly protectant fungicide program should do so immediately and consider adding downy mildew specific fungicides. For more information on the control of downy mildew in cucurbit crops please see the 2015 Commercial Fungicide Recommendations Guide.
Late blight (US-23) has been found on two tomato fields near Chester and Long Valley in Morris County, New Jersey. This is the first report of late blight in the state and region to date. All tomato (and potato) growers should immediately scout their fields looking for the diagnostic symptoms of the disease on leaves (Fig. 1) and/or fruit (Fig. 2). Tomato growers (and potato) who have not initiated a regular weekly protectant fungicide program should do so. The prolonged, wet weather we have experienced and are expected to have this week are ideal conditions for late blight development. For more information on the control of late blight on tomato and potato please see the 2015 Commercial Fungicide Recommendations Guide.
Late blight on tomato leaves.
Late blight on green tomato fruit.
Bacterial brown spot (Pseudomonas syringae pv. syringae) was found on lima bean in southern New Jersey this past week. Bacterial brown spot is unusual and tends to show up under prolonged wet conditions. The bacterium is spread from the soil to the lower canopy by splashing rain and wind. Working in fields and cultivating during wet conditions can also help spread the bacterium. The symptoms that develop on the leaves look similar to a fungal infection. Copper applications may help to suppress the spread of the disease.
Bacterial brown spot of lima bean. Symptoms look like a fungal infection.
(Photo by Michelle Infante-Casella)
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