Disease Management Next Year Depends on Good Sanitation Practices This Fall

Wow what a year it has been for plant diseases. Late blight in tomatoes and potatoes, angular leaf spot in strawberries, Scab in apples and downy mildew in almost every vegetable and fruit crop grown in the province, has kept growers busy this year. Fruit and vegetable growers have not been able to park their sprayers for a minute this summer. Fortunately despite the heavy disease pressure experience this year, damage caused by some foliar diseases has been minimized in many fruit and vegetable crops with the use of integrated pest management strategies including the timely applications of fungicides. Regardless of our best efforts, some foliar diseases can still be observed in many fields, orchard or vineyard. Diseased leaves, fruit or branches left in the field or orchard can become a source of the pathogen for next year's crop. Therefore, implementing good sanitation practices this fall after harvest will go a long way in preventing or minimizing disease levels next year.

Sanitation practices involve the removal of a source of the disease and include burning, or burying infested crop debris. Burying crop debris through deep cultivation provides a barrier that will prevent the release of spores and makes it more difficult for the pathogen to spread to susceptible plants by wind or rain splashing next year. Burying infested debris will also expedite the decomposition of infected crop residue that will reduce or even eliminate the probability of pathogen survival. Burying infested crop debris is more effective for managing foliar pathogens than it is for soilborne pathogens since the latter are often well adapted to survive in the soil for long periods of time.

Unfortunately burying infested crop debris may not be possible for all crops. For example, tree fruit growers who have been battling foliar diseases in their orchards this past summer may not be able to bury diseased leaves because of established grass pathways. However, racking and then chopping the diseased leaves with a flail mower will hasten leaf decomposition and reduce the level of pathogen carried over to next year. Research has shown that applying urea either in the fall or early next spring to chopped leaves infested with apple scab will also hasten diseased leaf decomposition and reduce the primary scab inoculum for next season. Pruning and removing diseased branches or cankers during the winter or early next spring is another sanitation practice that will reduce or eliminate certain pathogen from the orchard.

Sanitation also involves cleaning equipment such as tractors, mowers, sprayers and other implements to remove soil or debris that could be harbouring pathogens. A power washer with enough pressure to wash off chunks of mud, soil and debris from equipment and tools will be a prerequisite for disease management next year. Some pathogens such as bacteria can adhere to surfaces and may not be easily removed even with a high powered pressure washer. Washing benches, trays, tool, warehouses, storage facilities including storage crates with an ammonium based product or a ten percent solution of bleach and water will further reduce the level of certain pathogens that can survive on surfaces.

Remember, a successful disease management strategy for next year should start with good sanitation practices this fall.