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Reports on Plant Diseases

RPD No. 914 - Cloudy Spot of Tomato Fruit

October 1988

[ Symptoms ] [ Control ]

Cloudy spot of tomato fruit is caused by the feeding punctures of stink bugs. The symptoms are believed to be due to a toxin injected into the fruit when stink bugs (Pentatomids spp) feed on the fruit. This is one of the most common problems found in home gardens in Illinois.

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On the green fruit, the symptoms appear as whitish areas with indistinct borders. Isolated spots may be from 1/16 to over 1⁄2 inch in diameter; or, the spots may emerge and involve a large portion of the fruit surface. On ripe fruit the spots are light yellow (Figure 1). Peeling back the skin shows the discolored areas as superficial, shiny, somewhat spongy masses of tissue composed of silvery white cells. The cloudy spots may be cut out by the processor if top-quality, canned, whole tomatoes are desired.

The condition is most common from late July or early August until the end of the season, coinciding with the activity and feeding of the stink bugs (Figure 2). These insects may be so few in number that they go unnoticed. However, only a few are necessary to cause the appearance of cloudy spots on most tomato fruit in a home garden. The problem is most prevalent where weeds have not been adequately controlled favoring high populations of stink bugs.

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Figure 1. Cloudy spot on ripe fruit - note light yellow spots on fruit. (Courtesy Kansas State University)

Figure 2. Stink bug feeding on green leaf.






Stink bugs are difficult to control. Weedy areas, such as fencerows and ditch banks, are the most common source of these insects. Commercial growers may spray fencerows using 2 pounds of 50-percent carbaryl (Sevin) wettable powder in 100 gallons water. Home gardeners should spray weedy areas with 2 tablespoons of 50-percent carbaryl (Sevin) wettable powder in 1 gallon of water. While tomatoes are still small, commercial vegetable growers may apply1 pound of actual carbaryl (Sevin) per acre as a wettable powder. This treatment should be applied with sufficient water to thoroughly cover the foliage. Sevin dust may be used applying 1 pound of actual carbaryl per acre. At least 7 days should elapse between treatment and harvest. Wash all fruit before use.

Home gardeners may use 2 tablespoons of 50-percent carbaryl (Sevin) wettable powder or 2 teaspoons of 50- percent malathion liquid concentrate in 1 gallon of water. Spray the foliage of the plants thoroughly. Wash all fruit before use.

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Information concerning insecticides, weed control, varieties, and other recommendations can be found in the Illinois Homeowners' Guide to Pest Management, available at your nearest Extension office.

University of Illinois Extension
College of Agricultural, Consumer and Environmental Sciences
Crop Sciences | Entomology
Natural Resources & Environmental Sciences
Illinois Natural History Survey
Illinois C-FAR SRI

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