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Emerging Vegetable Diseases in Illinois

Cucurbit yellow vine disease, Phytophthora blight of cucurbits, bacterial fruit blotch of watermelon, and virus diseases of cucurbits are newly emerged vegetable diseases in Illinois.

Cucurbit yellow vine disease. Yellow vine, caused by the bacterium Serration marcencens, is a serious disease of cantaloupe, pumpkin, squash, and watermelon. Leaves near the crown of the plant or entire plant turn bright yellow. Yellowing and leaf death generally progress outward from the crown. Eventually, entire plant is killed. The diagnostic feature for yellow vine is a light brown discoloration of phloem visible in cross section of the lower stem and roots. The distribution of the disease in the fields is patchy. Squash bug is a vector of S. marcescens. At present, there are no satisfactory measures available for control of this disease. Controlling squash bug provides some degree of disease control.

Phytophthora blight of cucurbits. Phytophthora blight, caused by Phytophthora capsici, has become one of the most serious diseases of cucurbits, eggplants, peppers, and tomatoes. P. capsici causes seedling damping-off, root and crown rot, leaf spots, foliar blight, and fruit rot. The pathogen survives between crops as oospores or mycelium in infected tissue. The most effective approach in controlling Phytophthora blight of vegetables is to prevent the disease from becoming established in the field. The following measures help to manage Phytophthora blight in the fields. Select field with no history of Phytophthora. Select well-drained field. Clean farm equipment of soil between fields. Avoid excessive irrigation. Do not work in wet field. Do not leave cull fruit in the field. Scout field for symptoms routinely, especially after major rain and particularly in low areas. When symptoms are localized in a small area of the field, disk the area. Discard infected fruits. Do not place fruit on infested soil. Plant resistant varieties, if available. Seed-treatment with Apron XL LS or Allegiance FL is effective in preventing seedling death. Spray applications of Acrobat 50WP plus a copper compound are effective against foliar blight and fruit rot of cucurbits.

Cucurbit yellow vine disease in a cantaloupe field

Fig. 1. Cucurbit yellow vine disease in a cantaloupe field. (Courtesy B.D. Bruton)

Cross section of a watermelon vine showing phloem discoloration caused by yellow vine disease

Fig. 2. Cross section of a watermelon vine showing phloem discoloration caused by yellow vine disease. (Courtesy B.D. Bruton)

Phytophthora blight of pumpkin

Fig. 3. Phytophthora blight of pumpkin.
A. Crown infection
B. Anewly infected vine
C. A fully-developed lesion
D. Agirdling lesion affecting a part of a vine

Phytophthora fruit rot

Fig. 4. Phytophthora fruit rot.
A, Cucumber
B. Processing pumpkin
C. Acorn squash
D. Watermelon

Mohammad Babadoost
Department of Crop Sciences,
University of Illinois, Urbana, IL 61801
(217) 333-1523; babadoos@illinois.edu

Department of Crop Sciences
College of Agriculture, Consumer and Environmental Sciences
University of Illinois Extension
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