For this week’s article, I am going to tell you about two common garden/landscape problems about which I received calls in the last two weeks. Maybe you have seen these problems and were wondering what they were and what to do about them.
The first is Downy mildew on cucumbers. This is a problem many home gardeners experience on cucumbers, watermelon and cantaloupes.
Pumpkins are susceptible as well, and it is usually evident on plants by mid to late August.
Symptoms first appear as light green areas on the upper surface of leaves on plants near the center of the row. Soon after, there is a fine whitish gray downy growth on the lower leaf surface at these light green areas.
Downy mildew is caused by the fungus Pseudoperonospora cubensis and is spread by wind currents, water splashed from rain or irrigation, or from gardener’s hands, clothing and tools. It lives and thrives in humid, cool to moderately warm temperatures, but will tolerate hot days. Long hot, dry periods can repress the spreading of this disease. This problem does not overwinter in Delaware; spores are blown north each growing season as favorable conditions arrive.
To protect for cucumbers and cantaloupes, grow resistant varieties for this area and practice crop rotations in the garden. Provide good growing space between plants and rows. Grow vigorous plants that will repel or be able to withstand attacks from pests. When irrigating, be careful and maintain proper soil fertility. Keep surrounding garden areas mowed and clear of weeds that may be susceptible hosts to Downy mildew.
For more information and/or a list of resistant varieties see Virginia Cooperative Extension’s publication, visit http://pubs.ext.vt.edu/450/450-707/450-707.html
The second question regarded garden tomatoes that crack and/or split. Cracking is a physiological disorder and is caused by soil moisture fluctuations. The most common cracking occurs in a circular pattern around the stem. Splitting may also occur on the tomato between the stem and the blossom end. These problems occur as your tomato begins to reach the mature green stage and water to the plant is reduced or cut off due to drought or no irrigation, causing the tomato to ripen. The thin outer surface of the tomato begins to thicken to protect the tomato during and after harvest. If the water is restored after ripening starts the plant will translocate nutrients and moisture into the fruit. This causes the fruit to enlarge, which causes the thin outer skin to crack. It may occur anytime during fruit is growth. The earlier the fruit cracks, the bigger and uglier the cracks get. Some tomato varieties are more susceptible than others to cracking and splitting.
When the tomato cracks or splits, it exposes the fleshly meat of the tomato to insect pests and diseases.
