Diseases of truck crops Diseases of truck crops / Ralph E. Smith diseasesoftruckc119smit Year: 1940 66 California Agricultural Extension Service [Cir. ho become infected and, when used for seed, perpetuate the trouble by pro- ducing diseased plants and also by contaminating the cutting knife and spreading the organism, Erivinia atroseptica, to healthy tubers. Pota- toes in storage may develop a soft rot from this cause, usually starting near the stem end. The bacteria which cause blackleg may survive in the soil from one season to another. They are also spread by certain insects from diseas
Diseases of truck crops Diseases of truck crops / Ralph E. Smith diseasesoftruckc119smit Year: 1940 66 California Agricultural Extension Service [Cir. ho become infected and, when used for seed, perpetuate the trouble by pro- ducing diseased plants and also by contaminating the cutting knife and spreading the organism, Erivinia atroseptica, to healthy tubers. Pota- toes in storage may develop a soft rot from this cause, usually starting near the stem end. The bacteria which cause blackleg may survive in the soil from one season to another. They are also spread by certain insects from diseased to healthy tubers. Where blackleg is serious, diseased plants should be rogued from the Fig. 31.—Blackheart of potato. field, care being taken to remove and destroy any tubers which have formed. Seed treatment for other diseases like scab and rhizoctonia, to- gether with crop rotation, will help to control this. Dry Rot.—Potatoes in storage often show a dry, powdery or leathery type of decay which usually starts from bruises on the surface. High temperature and humidity and poor ventilation favor this, since these conditions are favorable to the fungus, a species of Fusariuni, which causes dry rot. Careful handling, cold-storage rooms at a temperature between 36° and 40° Fahrenheit and with good ventilation, and control of other tuber-rotting diseases, help to reduce losses from dry rot. Early Blight.—Brown, circular, dead areas develop on the leaves, blighting and killing them and defoliating the plants. This fungus dis- ease, caused by Alternaria solmii, is sometimes seen in California but is not often serious.
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