Willow problems could be from drought, disease or bugs | NevadaAppeal.com
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Willow problems could be from drought, disease or bugs

JoAnne Skelly

With Labor Day only a week away, summer is drawing to a close. The average first frost date is Sept. 15, which means some of us will have freezes as early as Sept. 1.

Some years, we get lucky and don’t have a freeze in September, but don’t count on it. Plan on watching the weather forecast each night, so if needed, you can cover your cold-tender plants, such as tomatoes, peppers, squash, cucumbers, and basil.

Pay attention, and if the night is still and clear, expect a freeze.

After a dry, hot, windy summer, plants are showing the effects of stress. Sharon at Greenhouse Garden Center said a number of people have been coming in about problems with willows.

They are noticing branches dying back and limbs and trunks oozing a wet brown goop. Willows are known to have a number of problems, many of which can be solved by increasing irrigation.

The causes of die-back can be lack of water, diseases such as cytosphora canker, borers or other insects. The oozing is usually a bacterial disease called “bacterial wetwood,” “alcoholic flux” or “slime flux.” There are no real cures for either cytosphora canker or slime flux, other than keeping the tree healthy all year. The good news is that trees can survive with these diseases for years.

With both of these diseases, when pruning, sterilize your pruning shears with either a 10-to-1 ratio of water to bleach or a spray of rubbing alcohol (isopropyl). This will prevent the spread of the disease to other parts of the same plant and to other plants.

To improve the health of the tree, give it more water. Willows thrive with “wet feet” for at least six months of the year. If the soil doesn’t stay moist, they become stressed and susceptible to flare-ups of cytosphora and wetwood. This also means you need to increase the water you apply in dry autumns, winters and springs. To learn more about wetwood, refer to the fact sheet at http://www.unce.unr.edu/publications/files/ho/2003/fs0333.pdf.

Various kinds of borers attack weakened willows. There are long-horned beetles and metallic wood borers, either flatheaded or roundheaded. Clearwing moths also attack willows. Some weevils and carpenter worms also damage willows.

If you suspect a borer, bring a sample of the insect or the dying piece of wood to your local University of Nevada Cooperative Extension office for identification. There are some insecticidal sprays for controlling borers, but not all insecticides work on every kind of borer. So, correctly identifying the pest is essential for successful control.

Even with their susceptibility to many diseases and pests, willows are hardy plants. With enough water, they resist diseases and insects. A spring and fall application of fertilizer and lots of water all year will keep them healthy.

For more information, e-mail skellyj@unce.unr.edu or call me at 887-2252. You can “Ask a Master Gardener” by e-mailing mastergardeners@unce.unr.edu or call your local University of Nevada Cooperative Extension office. Check out many useful horticulture publications at http://www.unce.unr.edu.

• JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.