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Garden Help Desk: Speculation surrounds death of walnut trees

By Usu Extension - | Jun 12, 2021
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English walnut trees throughout Utah Valley have poor leaf-out and bare branches. Not all the branches that look dead are dead. Give the trees good care, remove branches that are truly dead, and give any branches with green tissue under the bark more time to recover.

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It's common for the oldest leaves on lettuce to be yellowed, brown or shriveled. Other mature leaves may be scorched at the edges.

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Once faded or scorched leaves are trimmed from garden lettuce, the rest of the head will be fine.

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English walnut trees throughout Utah Valley have poor leaf-out and bare branches. Not all the branches that look dead are dead. Give the trees good care, remove branches that are truly dead, and give any branches with green tissue under the bark more time to recover.

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English walnut trees throughout Utah Valley have poor leaf-out and bare branches. Not all the branches that look dead are dead. Give the trees good care, remove branches that are truly dead, and give any branches with green tissue under the bark more time to recover.

We’ve been getting several calls and emails each day about walnut trees that seemed to look fine last year and now look either dead or dying.

You’ve probably seen struggling walnut trees when you’ve been out and about. Is it a walnut tree apocalypse? A walnut plague? You may have heard about a “new” walnut disease and wondered if that’s the problem.

It’s true there is a serious fungal disease, Thousand Cankers Disease, affecting black walnut trees and occasionally English walnut trees. Black walnut trees are very susceptible to the disease, but English walnut trees are only slightly susceptible.

The disease is spread by a small beetle called the walnut twig beetle. Once the fungus is in the tree, small cankers develop under the bark where the beetles have entered. Repeated infestations lead to tree decline and death. Preventing beetle infestation of black walnuts is important because there is no treatment for the disease. Infected trees generally die within a few years of showing symptoms.

Most of the walnut trees you’re seeing now with dead branches are English walnut trees and very few of the trees with dead branches have the disease. So, what exactly is going on with all these walnut trees?

The short answer is, we don’t exactly know, but we hope to know more as the season progresses.

The most likely explanation is that the dead-looking branches were caused by an environmental event.

Our extended mild autumn last year followed by a sudden, frigid shift to winter may have caused some damage to trees and shrubs. This has happened a few times in the past 10 years or so. Some branches may die and the leaf-out on other branches can be delayed for weeks. If this happened to your tree, some of the branches may just need extra time to leaf out this year.

There is also speculation that our dry winter and early, dry spring may have stressed the trees. The long, warm autumn plus sudden winter weather is probably the more likely explanation. In any case, just give your tree more time for now. Extra (frequent) watering or fertilizing isn’t recommended.

A branch isn’t necessarily dead just because it hasn’t leafed out. You can tell if a branch or twig is truly dead by scratching into the bark to check for green tissue under the bark. If there is green, the branch is still alive. A branch that looks dead but still has green tissue under the bark should be given several more weeks to recover from whatever happened. Truly dead branches should be removed.

If you have an English walnut tree that started out the year with dead-looking branches, give your tree good care with deep, infrequent watering and give it time.

Question: I’ve tried to grow lettuce for two years now and it never looks like the lettuce at the grocery store. A lot of my lettuce leaves are either yellow or they have lots of black edges. How can I get better lettuce?

Answer: Lettuce is a great garden veggie. It’s delicious, comes in many different colors, sizes, shapes, and leaf forms and thrives in cool spring weather before it’s safe to plant tomatoes, peppers or other warm-season plants. Because you start it in early spring, you have something to enjoy while you wait for those tomatoes and peppers to mature.

Planting at the right time and consistent, even watering are the most important strategies for preventing scorched leaf edges on your lettuce but even with even watering, scorch on the leaf edges is almost inevitable once we start having hot days like the ones we’ve had recently. When summer heat arrives it’s time to get your lettuce harvested and into the refrigerator.

Another reason why your lettuce in the garden doesn’t look like the lettuce in the grocery store is because the lettuce in the store has been “groomed” as it goes out from field to packing house to store and may get trimmed a little more before it goes from packing box to store shelf. You never get to see any old or scorched leaves the lettuce may have had in the field.

Your lettuce might have a little more leaf scorch than lettuce grown commercially, but once you clean off the old or damaged leaves it will look nice.

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