Cucumber downy mildew is caused by Pseudoperonospora cubensis (P. cubensis), a parasitic oomycete or water mold (not a fungus). It does not overwinter on dead tissue, as it needs living tissue to survive. This disease can infect all cucurbits, but does the most damage on cucumbers and melons.
Infection on cucumber leaves looks like angular pale green or yellow spots that are contained in the leaf veins. The underside of the leaf may show darker brown or gray spots. These infections can result in reduced foliage and therefore reduced yields, misshapen fruits, and/or plant death. Downy mildew especially affects high humidity areas where the disease can spread more rapidly.
There are several ways to prevent, delay or combat downy mildew. One way is to utilize varieties selected for downy mildew resistance. Cornell Cooperative Extension has conducted downy mildew variety trials to verify and evaluate the levels of resistance of several varieties. The most recent trial has demonstrated the strength of Tokita varieties in the face of this disease.
The trial report can be found here: Evaluation of Cucumber Varieties Resistant to Downy Mildew, 2021.
This trial at the Long Island Horticultural Research and Extension Center (LIHREC) was organized to compare new varieties including TSX-CU231AS (Tokita variety) to both DM resistant and susceptible varieties. By evaluating fruit quality and yield on top of disease resistance, the trial sought to share possible new options with growers.
Notable quotes from the trial results:
“fruit of TSX-CU231AS received the highest average for all ratings for fruit quality”
“TSX-CU231AS and DMR401 yielded the most”
From past results at University of Massachusetts: “TSX-CU231AS and two other Tokita experimentals (TSX-CU234AS and TSX-CU236AS) exhibited the best resistance when tested (2020).”
LEVELS OF RESISTANCE
In our variety descriptions, we describe three levels of resistance:
Susceptible: varieties with no resistance. Tokita varieties in this category include TSX-208AS. Suitable for environments without downy mildew pressure.
Intermediate Resistance (IR): varieties with resistance, though may become infected in severely affected areas and seasons. Examples include TSX-201AS, TSX-203AS
High Resistance (HR): varieties with very strong resistance, and there is a significant difference between the 2nd and 3rd group. This includes TSX-231AS and several upcoming varieties currently in trial.
Visit our cucumber products page to learn more about our cucumber offerings.
If you are interested in conducting trials with us, please reach out via firstname.lastname@example.org.
Other downy mildew resources:
CDM IPM PIPE: Forecasting tool to visualize where in the US it has been observed
You can find a list of disease resistant vegetable varieties here: https://www.vegetables.cornell.edu/pest-management/disease-factsheets/disease-resistant-vegetable-varieties/