The following diseases have been confirmed by Nancy Gregory: Alternaria Leaf Blight Caused by the fungus Alternaria cucmerina, is a pathogen that can occasionally damage cucurbits in Delmarva.
In drip Irrigated systems, M. Vines with stem lesions have yellowing and death of leaves photo 3. Fruit may also become Infected, resulting In a firm, dark-colored decay.
There are no control measures currently recommended for charcoal rot. Cultural practices such as rotation, deep plowing and Diseases of melon of soll moisture have not been effective. There has been little or no effective disease control using solarlzatlon or fumigation. Charcoal rot may be found In the same fields at the same time as Monosporascus vine decline, and control measures recommended for Monosporascus vine decline may also be beneficial In reducing charcoal rot see Monosporascus vine decline.
With sufficient moisture in the foliage, disease progresses rapidly. Plants of all ages are susceptible. Early infections cause yellow spots on leaves that coalesce, and the leaf turns brown.
When humidity is very high, especially early in the morning, a white to light purple growth is visible on the underside of leaves, which consist of asexual spores. Older leaves are usually infected first. In areas where disease has been previously confirmed, it is important to watch for he initial symptoms and signs of disease so that fungicides can be applied as soon as possible.
Protectant fungicides such as chlorothalonil and mancozeb should be applied in rotation with fungicides of other modes of action such as Gavel, Ranman, Previcur and Tanos. Repeat applications of fungicides may be necessary if conducive weather conditions persist.
Alternating different chemicals is important to avoid development of resistance. Monosporascus vine decline Monosporascus vine decline is caused by the fungus Monosporascus cannonballus.
Plants may be infected when they are young, but symptoms usually do not appear until vines are mature and fruit are developing photo 1. Foliage may have necrotic areas in the leaves and a progressive decline in the entire crown photo 2.
Tan lesions are often observed on roots, and, in the later stages of disease only, small black specks appear photo 3. These specks are the sexual reproductive stage of the fungus that contain large black spores — thus the species name cannonballus photo.
These spores are commonly found in many different soils, and the fungus seems to be indigenous to certain semiarid soils. There is no resistance in melons, but some varieties are much more susceptible than others. Caravelle and Desert Mark are among the most susceptible. The presence of spores in soils can be determined in laboratory assays, but to date there has been no direct correlation between the numbers of spores in soil samples and the incidence or prevalence of disease.Watermelon Foliar Diseases For a larger view and narrative of each disease please click on the photo.
Photos provided by Tom Isakeit, Department of Plant Pathology, Texas A&M University. • Cucurbits (muskmelon, watermelon, cucumber, pumpkin and squash) • Alfalfa, lettuce, bean (Phaseolus vulgaris), alkali mallow (Sida hederacea) and Wright's groundcherry (Physalis wrightii). * • Transmission tests demonstrated that lettuce, snap bean, alkali mallow, Wright's groundcherry, and buffalo gourd (Cucurbita foetidissima).
For melon growers, a few of the top diseases to be on the lookout for this season include Fusarium wilt, angular leaf spot, and powdery mildew. Fusarium Wilt According to Amanda Gevens, assistant professor and Extension plant pathologist in potatoes and vegetables at the University of Wisconsin, Fusarium wilt has the potential to be the most problematic.
• Cucurbits (muskmelon, watermelon, cucumber, pumpkin and squash) • Alfalfa, lettuce, bean (Phaseolus vulgaris), alkali mallow (Sida hederacea) and Wright's groundcherry (Physalis wrightii).
* • Transmission tests demonstrated that lettuce, snap bean, alkali mallow, Wright's groundcherry, and buffalo gourd (Cucurbita foetidissima).
Watermelon Foliar Diseases For a larger view and narrative of each disease please click on the photo. Photos provided by Tom Isakeit, Department of Plant Pathology, Texas A&M University.
Disease is found anywhere cantaloupe, honeydew and other melons are grown in Arizona; it is favored by moderate to high humidity and low light intensity.
A white powdery growth on the leaf surface starts out as small spots, often on the lower leaf surface, and gradually covers the entire leaf (photo 1).