I am seeing some plectosporium blight in a few pumpkin fields this year, not as bad as last year but still there. This disease will probably increase if we continue having frequent rains in some locations.
In the last few weeks several sweet corn fields as well as some watermelon and even a few tomato fields have
been found with sulfur deficiencies (figs. 1 and 2). In sweet corn symptoms often appear as green leaves with
light yellow or green striping on the newer leaves (fig. 1). In watermelon symptoms appear as a light green or
light yellowing of the leaves of newer growth (fig. 2). In tomato unless severe you usually do not see any visible
sulfur deficiency symptoms in the field, but fruit set and quality could be worse
Southern blight is a fungal disease that is most common in the tropics and subtropics, but also is found in the SE United States in the summer. In Maryland we usually find it in the southern part of the state in counties like St.
Mary’s, Charles and Wicomico. It has been found this year in more northern counties such as Frederick, Montgomery and Baltimore.
By this time of the season I usually see pumpkin fields infected with powdery mildew pretty commonly throughout the mid-Atlantic. And while powdery is present in many pumpkin fields it does not seem as bad as in previous years.
I have been seeing some ozone damage to cucurbits and oddly to tomatoes over the last 2 weeks or so, which is not unusual with the hot hazy conditions we are having. Ozone is the most common air pollutant in the eastern United States.
Growers may already be seeing leaf symptoms on their cantaloupe plants that are often misdiagnosed as a foliar
disease. However, these leaf symptoms described below indicate manganese (Mn) toxicity which is related to
low soil pH.
One of the main things a grower can do to ensure a good quality pumpkin is to be sure they
maintain their fungicide applications for as long as they continue to harvest fruit. Maintaining
good foliage cover for your pumpkins results in pumpkin handles that are dark green stout and
firm (fig. 1).
Gummy stem blight (GSB) was found in an Eastern shore muskmelon field in the last few weeks. It is a cucurbit disease caused by the fungal pathogen Didymella bryoniae. This fungus is favored by cool to warm, rainy weather. It can infect a host at any stage of growth and affects almost all parts of the plant including leaves, stems and fruits.
I do not have to tell you that these frequent and heavy rains we have been having over the last 2-3 weeks have
really increased the amount of foliar and at times soil diseases in our vegetable crops. In cucurbits foliar diseases
such as Alternaria, gummy stem blight and an odd one Cercospora (figs 1a, 1b) all have been found causing moderate
to severe defoliation in some fields that are heavy with fruit.