Cucumber Leaf Spot: Treating Angular Leaf Spot In Cucumbers

QA Pseudomonas syringae cucumber e1502820671492
QA Pseudomonas syringae cucumber e1502820671492
(Image credit: GKH Q&A via wsdoin)

Cucumber is a popular vegetable to plant in home gardens, and it often grows without issue. Sometimes though, you see bacterial leaf spot symptoms and have to take action. When you notice small circular spots on the leaves, you are probably dealing with cucumber leaf spot. Read on for information about this disease and how to start treating angular leaf spot in cucumbers.

About Cucumber Leaf Spot

Cucumber leaf spot is also called angular leaf spot of cucumber. It is caused by the bacterium Pseudomonas syringae pv. lachrymans. You’ll find pseudomonas syringae on cucumbers but also on other vegetable including zucchini squash and honeydew melon.

Bacterial Leaf Spot Symptoms

Pseudomonas syringae on cucumbers causes dark spots on the leaves. Look closely and you’ll find that they are water-soaked lesions. In time they will grow into large, dark blotches. These blotches stop growing when they encounter major veins in the leaves. That gives them an angular appearance, which is why the disease is sometimes called angular leaf spot. If the weather is wet, these spots will be covered over by a white substance. It dries into a white crust, tearing the foliage and leaving holes.

Treating Angular Leaf Spot of Cucumber

Pseudomonas syringae on cucumbers proliferate during wet weather and disappear when it is dry. There lies your best course in treating angular leaf spot of cucumber: prevention. Since cucumber leaf spot disappears with a couple weeks of dry weather, it would be nice to be able to control the weather. While you can’t go that far, you can adopt the best cultural practices for your cucumber plants. That means to irrigate them in a way that doesn’t wet their leaves. In addition, don’t work with your cucumbers in wet weather or harvest the vegetables in wet weather. You could be spreading pseudomonas syringae on cucumbers to other cucumbers or other vegetable plants. It also helps to buy resistant cucumber varieties and keep your garden free of fallen leaves and other debris. Limit nitrogen fertilizer and don’t grow the same veggies in the same place for more than a few years. You can also apply a recommended bactericide when you notice the first bacterial leaf spot symptoms. This will help you in treating angular leaf spot of cucumber.

Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.