Nitrogen Fertilizer Affects the Severity of Anthracnose Crown Rot Disease of Greenhouse Grown Strawberries

The influence of nitrogen, phosphorus, and potassium on the severity of anthracnose crown rot was evaluated in three greenhouse studies. Strawberry plants were fertilized three times weekly with a modified Hoagland's Nutrient Solution containing the treatments and inoculated eight weeks after treatment applications began with a conidial suspension of the causal pathogen, Colletotrichum fragariae. Disease severity was rated 30 days later on a scale of 0 (no symptoms) to 6 (plant dead). In the first study, the effect of N, P, and K levels was evaluated using 16 treatments: eight N levels with either low P and K or high P and K. Disease severity ratings and percent foliar N increased as N level increased but were not influenced by the level of P and K. In two other experiments, seven N sources were each evaluated at three levels. Plants receiving 160 ppm N had higher disease severity ratings than plants receiving 0 or 40 ppm N. Among plants receiving 160 ppm N, those treated with Ca(NO 3 ) 2 had the least disease. When N fertilizer is applied to strawberry plants as Ca(NO 3 ) 2 , anthracnose crown rot severity should be less severe than when N is applied in ammonium forms. Accepted for publication 13 April 2009. Published 9 June 2009.