A study of the effects of fungitoxic compounds on Phytophthora cinnamomi in water

Copper and chlorine-releasing compounds were the most fungitoxic of 13 compounds tested in water for inhibition of Phytophthora cinnamomi. Mycelium was killed when immersed for 24 h in suspensions containing copper (13–45 mg/1) or a solution containing free residual chlorine (100 mg/1). Sub-lethal concentrations of these compounds reduced the numbers of sporangia. Exposing zoospores of P. cinnamomi for 60 s to water containing 2 mg free residual chlorine/1 reduced subsequent colony production on agar plates by 96–100%.
Prothiocarb, etridiazole ex. and furalaxyl killed mycelium immersed in solutions or suspensions for 3–6 days at 1500, 1000 and 600 mg a.i./l respectively and suppressed sporangium production at 1000, 500 and 300 mg/1.
Mycelium survived 3 days' immersion in ethyl hydrogen phosphonate compounds at 4000 mg a.i./l but 1000 mg a.i./l suppressed sporangium formation.
1-(2-Cyano-2-methoxyiminoacetyl)-3-ethyl urea and drazoxolon did not kill mycelium at 2000 and 1500 mg a.i./l respectively with a 6-day exposure, but reduced numbers of sporangia produced.