Downy Mildew

Progression of disease

Downy mildew is a wind-transmitted pathogen that affects all cucurbits. It spreads fast and can completely defoliate susceptible varieties within weeks of arriving on your farm.

There are currently no commercially available cucumber varieties that are resistant to strains of the pathogen that occur in the Eastern US, and new strategies are needed.

Research is being performed by Chris Smart, at Cornell University's Geneva campus, assessing pathogen diversity and testing new breeding lines for resistance. Working with this pathogen can be challenging since it can only survive on living plant tissue. Smart’s lab is studying 15 isolates collected across NY (from Long Island to Lake Erie) during the 2012 and 2013 growing seasons, keeping the pathogen alive on seedlings in the greenhouse. They are assessing the diversity in the DNA of these isolates, and also using them to look at host plant resistance. This winter, plant resistance is being evaluated by making a cocktail of these isolates and inoculating both commercially available and newly-developed breeding lines of cucumber, squash and melon. Results should be available by spring 2014.

On the CDM-IpmPIPE, we can observe the disease patterns as downy mildew moves up the coast with tropical storms, and with winds from the west. CDM-IpmPIPE relies on reports from growers like you to track the movement of downy mildew. The more people use this resource, the more accurately users can anticipate the disease’s arrival and determine when to start using OMRI-approved pesticides.

Peter Ojiambo at North Carolina State University is working to make this system even better and more accurately forecast chemical control needs. Nevertheless, the more farmers utilize this resource, the more effective it will be. With that, we encourage you to watch out for and report downy mildew on your farm.

In addition to proactive planning and management strategies like the CDM-IpmPIPE and directly evaluating varieties for resistance, we will perform trials inside high tunnels to test drier environments that are less hospitable to the disease. You’ll have access to information about these control strategies as we pull together the data from our trials.