verticillium wilt In raspberries

Asked June 9, 2018, 11:04 AM EDT

Hello, I’m very concerned that my raspberry bush may be exhibiting signs of verticillium wilt. What worries me more is that is planted near blueberries and a new akebono cherry tree. I’m not sure what can or should be done to save my other plants. Can you please advise? I live in Southeast Corvallis and I’ve included photos. Many thanks. Chrysanthemum

Benton County Oregon home horticulture

1 Response

Thanks for your question.

I’m not sure this is verticillium wilt, mainly because the usual progression in raspberries is that new canes are affected in mid-late summer. The foliage wilts and takes on a scorched appearance from the bottom up, leaving a tuft of green leaves at the tip. Often just one side of the plant is affected, but not always. The entire plants often suddenly die.

Also, verticillum wilt is particularly serious in black raspberry but rarely attacks red raspberry. So if you have red raspberries, you probably don’t have verticillum wilt.

There’s an easy way to determine if you do have verticillium wilt. In raspberries, you will see bluish stripes or ribbons of infected tissue that extend up the canes from the ground. I’ve included two photos. The first shows the outside of a first-year cane with verticillium wilt. The second, with several canes, shows the bluish streak on the inside where the bark is peeled back. To check inside the cane, cut off an affected cane at the base and peel the bark back near the base. You may not see anything further up the cane.

If you don’t see the characteristic blue streaks, then something else is affecting your raspberries.

I suggest these other problems:

Phytophthora Root rot—(This is my first choice for your problem.) wilting and death of canes from early spring to late summer. Wilting often coincides with the onset of warmer, drier conditions. Leaves on infected canes may turn yellow or bronze, wilt, and develop scorch symptoms before dying. Dead leaves usually remain on the stem. Floricanes (second-year wood) often start to die just as the fruit begins to ripen in June, causing the fruit to be undersized or to wither before ripening. Primocanes (the new canes this year) usually begin to wilt from the tip down. Primocane tips bend over, exposing the silvery undersurfaces of the leaves forming a shepherd's crook. In many cases, one or a few canes of a plant may die while the rest remain healthy.

This is an environmental problem usually due to heavy soils and the roots standing in water. The raspberry will eventually die from it. Don’t replant in the same place. It’s helpful to put raspberries in a raised bed to avoid the problem.

Raspberry crown borer –(This is my second choice for your problem.) Look for two rows of girdling holes near the bottom of the canes affected. I’ve attached a photo. A raspberry cane borer laid eggs in the cane between the two rows of holes. Any cane with these holes should be cut at the base. Put the portion of the cane between the holes into a plastic bag, tied it closed up and throw it in the garbage. It’s important to control the cane borer as soon as you notice it, because they can quickly infest all your raspberries.

Armillaria root rot-- the disease is most common in newly established raspberry fields that are planted on land recently cleared of native vegetation. However, sawdust or wood chips can be a source of infection, especially if it is used as a deep mulch.

The first visible disease symptom is a decline and dieback in which leaves turn yellow, wilt, and die. This may occur only on one side of the plant or in one or two canes. You can diagnosis this by digging down about a foot below the soil line and use a pocketknife to remove thin layers of bark from the root collar. Mycelial fans are thick, white layers of fungus that adhere to the root bark and/or the wood beneath the bark. (This will probably kill your plant, so it’s really only practical for someone with a field of raspberries.)

There is no treatment available to the home gardener. Do not replant raspberries or blackberries in the same spot.

cane blight—This is unlikely unless the raspberry canes were damaged last year. A fungus invades wounds on canes stubs or pruned canes.

Finally, although I don’t think you have verticillium wilt, I’ll answer your question about verticillium wilt, cherries and blueberries. Cherry trees are very susceptible to verticillium wilt. If you have verticillium wilt, the cherry tree will die. Do not try to move the tree, since you will just contaminate the new spot you put it in. Blueberries are not affected by verticillium wilt.

Please write again if you have any questions about any of this, or anything else.