Angular leaf spot is a significant disease of the cucumber family that leads to reduced yields and fruit of poor quality. You may first notice the disease after a period of warm weather accompanied by rainfall. Treat Super leaf spot with a combination of good garden sanitation, fungicides and keeping the plants as dry as possible.
Angular leaf spot on members of the cucumber family is caused by the Pseudomonas syringae pv. lachrymans bacterium. It’s spread by wind, insects, machinery and people who handle the plants and harvest the fruit while the vines are wet. The bacterium survives on plant debris and in the soil, and it can dash from the soil on the plant by overhead watering and heavy rains. In addition, it spreads through seeds gathered from infected plants.
The damage begins as water-soaked places on the plants’ leaf. The affected areas later dry and turn gray or tan. A yellow halo may surround a damaged area, or spot, at first. With the years, the centres of the spots fall out, leaving holes in the leaves. The patches are confined between the veins in the leaves, giving them an angular shape. Lesions on the cucumber fruits begin as small, delicate water-soaked spots. They become dry, chalky and cracked.
Fantastic garden sanitation is a vital part of controlling the illness. Clean up plant debris regularly, and remove and destroy plant debris in the end of the season. Wait at least two years before planting members of the cucumber family in the same location. That practice applies to squash, pumpkins and melons as well as cucumbers. The illness spreads easily when foliage is wet. So using soaker hoses is useful because they water the soil around plants without obtaining the plants moist. It is ideal to avoid the plants when they are moist to prevent spreading the disease in your hands and clothes.
Fungicides containing copper might help control angular leaf spot in cucumbers. The spray is most successful once the temperature is above 75 degrees Fahrenheit and the leaf is wet. Spraying on a hot afternoon once the leaf is dry can injure the plants. Weekly spraying may be required to accomplish control of this disease. Always read and follow the package directions when using copper fungicides. Store unused parts of the fungicides in their original containers and out of the reach of children.