Management of phytophthora blight (Phytophthora capsici) on vegetables in Ontario: some greenhouse and field aspects
2015
Cerkauskas, Raymond F. | Ferguson, Gillian | MacNair, Craig
Phytophthora blight (Phytophthora capsici) affecting greenhouse vegetable production in Canada is reported for the first time. Aspects of the epidemiology and management of P. capsici in relation to greenhouse and field vegetable production in Ontario are discussed. Identification of the pathogen was based on cultural, morphological and molecular approaches, the latter using primer set PC1/2. The pathogen caused 10% plant population losses in a greenhouse pepper operation in Leamington, ON in 2006–2007, and 5%, 5% and 10% losses in commercial greenhouse tomato operations at sites in 2007, 2008 and 2011, respectively, with 1000 greenhouse tomato plants affected in 2012. Phytophthora blight occurred in 2006 in Haldimand-Norfolk and Essex counties on field cucumber and pepper, respectively, and in Essex county in 2007 on field pepper, squash and tomato. The disease was not observed on field pepper, tomato or cucumber plants in fungicide efficacy trials near Harrow, ON in 2005–2006 or near St. Williams, ON in 2007 where the disease had occurred previously. Symptom development was most rapid on greenhouse cucumber and least rapid on greenhouse tomato. Virkon ® disinfectant at 0.25%, 0.5%, 1% and 2% commercially formulated product was 100% effective in preventing zoospore germination of P. capsici while Chemprocide ™ disinfectant was not fully effective at 0.04%, 0.4% and 4%, and Virucidal Extra ® was intermediate in efficacy. The fungicides fluazinam, mandipropamid, cyazofamid and fluopicolide were effective in controlling P. capsici on greenhouse tomato, cucumber, and pepper plants for at least a 14-day period. Metalaxyl was less effective, possibly due to partial resistance in the fungus to this chemical.
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