Comparison of fungicide, systemic acquired resistance inducers and monopotassium phosphate as control measures for seedling diseases of muskmelon, cucumber, and tomato

Recent research has shown that many plants have an immune system that natur ally counteracts pathogenic attack. This natural systemic resistance is acq uired by treatments that cause mild oxidative stress in plants. Resistance of muskmelon seedlings to Pythium was compared following: osmotic seed prim ing in 0.35 M monopotassium phosphate (MKP), -1.0 MPa polyethylene glycol, or 0.35 M MKP with systemic acquired resistance activators experimental com pound X and Y added. Compound X, Y, and MKP were also compared with the com mercial fungicide Bayleton (1-(4-Chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-tr iazol-1-yl)-2-butanone) or Brave Weather Stik (tetrachloroisophthalonitrile ) for their control of powdery mildew on cucumber or rate bright on tomato transplants in a greenhouse. Maximum emergence of untreated seeds was less than 20%. Priming in MKP alone increased seedling emergence by 19% in Pythi um infected soil Il d after seeding. The percent emergence was 80% for seed s primed in MKP + X, the highest of any treatment tested. Washing seeds aft er priming in MKP + X decreased the percent emergence to 47%. The emergence of seeds primed in MKP + Y was 44% after 11 d. Fungicide provided the most effective control of both powdery mildew and late blight. Monopotassium ph osphate or compound Y had little effect on the spread of either disease. Sp ray treatments of X applied to cucumber and tomato seedlings improved resis tance to powdery mildew and late blight, respectively.