Plant Disease Management Handbook

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Potato (Solanum tuberosum) - Early Blight

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Tomato (Solanum lycopersicum) - Common Mosaic of Tomato (Internal Browning of Fruit)

Cause A combination of tobacco mosaic virus and potato virus X. Workers or equipment mechanically transmit this disease. Virus strains, plant age, and day length influence symptom severity.

Cause Fungi or fungus-like microorganisms, including Pythium spp., Phytophthora spp., Fusarium spp., and Rhizoctonia solani, can attack young seedlings of many vegetables including tomato. Seedlings are susceptible to infection before or after emerging from soil. If seedlings are affected before emerging, it presents as poor germination.

Cause The beet curly top virus, which also infects a wide range of crops such as bean, beet, cucurbits, spinach, squash, and pepper. The virus is disseminated by the beet leafhopper, Circulifer tenellus. There are no reports of seed transmission. The disease may be severe in central and eastern Oregon and Washington. It occurs in the Willamette Valley, especially the northern end when winds blowing through the Columbia Gorge transport the beet leafhopper from eastern Oregon.

Cause Physiological problem that occurs to some extent wherever large, fresh-market tomatoes grow. Some varieties are more likely to show catfacing than others. Growth disturbances during blossoming are thought to be the cause. Prolonged unseasonably cool weather may be involved. Excessive nitrogen fertilizer may aggravate the problem. Catface also may follow exposure to growth-hormone-type herbicides such as 2,4-D. Some fruit of 'Oregon Spring' is affected by catface every year.

Cause A localized calcium deficiency due to any soil or growing condition that affects calcium uptake. This physiological problem is common, especially in home gardens and can typically affect tomato, peppers, eggplant, watermelon, pumpkin, and squash. Drought, salinity and high temperatures have been found to promote blossom-end rot. If too little calcium is in the soil or if the soil is high in salts, calcium uptake will be impeded, especially under periods of sudden drought stress.

Cause The bacterium, Clavibacter michiganensis subsp. michiganensis, is carried in or on seed and survives in infected tomato debris, weed hosts, volunteer tomatoes, or on contaminated stakes or equipment. Handling seedlings and normal watering may spread the bacterium in seed flats. In the field, handling or pruning plants, using contaminated equipment, cultivation, and rain or irrigation water may spread the bacterium. Plants may be infected at any growth stage.

Cause Colletotrichum coccodes, C. dematium, and C. gloeosporioides cause anthracnose on tomato; C. coccodes is the most prevalent, but anthracnose is not common in the Pacific Northwest. The fungus overwinters as microsclerotia, often in association with plant debris. Solanaceous crops and weeds are all hosts. Seed may also be infected.

Cause Although this plant is considered relatively disease free, a few fungal leaf spots are reported from Southeastern States. These include Elsinoe leucospila (spot anthracnose), Cercospora sp., and Phyllosticta sp. Most of these are favored by rainy moist weather conditions.

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Yew (Taxus spp.)