More recent landscape questions and answers

Horticulture

Walnut leaf gall

What causes reddish-purple tumors about 4 by 6 milimeters in size on the stems of young, black walnut tree leaves? Some leaves are breaking off at the base close to the trunk.

This sounds like a gall, probably caused by an insect or mite. Usually these galls do not cause a great deal of tree stress and do not require treatment unless at very high levels.

For a certain identification of the problem and more specific treatment information, I suggest taking some photos or collecting a sample and submitting to the Plant Diagnostic Clinic. Please see the online image submission instructions and then click on the image link for insect images submission at the right side of the screen to submit photos and required background information to the clinic. You can find more information about the clinic, fees and how to submit physical samples on the Web.

Simeon Wright
Plant Diagnostic Clinic Coordinator

Stop leaf rust

What do I need to spray on my apple tree to stop the spread of leaf rust?

If your tree is infected with cedar apple rust, I suggest reviewing G6010, Fruit Spray Schedules for the Homeowner which will tell you what to spray and when you need to spray it to protect your apple tree.

For a certain identification of the problem and more specific treatment information, I suggest taking some photos or collecting a sample and submitting to the Plant Diagnostic Clinic. Please see the online image submission instructions and then click on the image link for plant disease images submission at the right side of the screen to submit photos and required background information to the clinic. You can find more information about the clinic, fees and how to submit physical samples on the Web.

Simeon Wright
Plant Diagnostic Clinic Coordinator

Yellow and brown tips on my junipers

What is causing the yellow and brown tips on my junipers?

The Plant Diagnostic Clinic often receives samples and calls about junipers with browned branch tips in the spring. I have observed a lot of this damage in central Missouri starting late last winter. There are several reasons this damage may occur. In some cases, it might be weather fluctuations or other sources of plant stress such as spider mite feeding. However, many healthy-looking junipers with just the terminal 2 to 6 inches of branch affected, the problem is Kabatina tip blight, caused by the fungus Kabatina juniperi.

Kabatina tip blight Generally, when you look closely at blight affected branch tips, there will be a distinct gray stem lesion where the dead, discolored foliage begins. Beyond that gray lesion area, the branch is usually green and healthy looking. If you have a hand lens, you might be able to see small black blisters in the grey area. Those are spore-producing bodies of the fungus, and their presence can help diagnose this disease. Often, other types of damage such as winter injury appear as a gradual yellowing and browning with no clear demarcation of tissue or grey lesion area.

Although plant pathologists believe the primary infection period is in the fall, the symptoms don’t usually become apparent until late winter. Blighted branch tips eventually fall off in May and June as new growth begins, and no new symptoms develop until the following winter. This disease does not usually cause extensive dieback or tree death, and control measures are not often necessary. However, there are some varieties that are more resistant to the disease, and by avoiding injuries to the branches in the fall, you may be able to reduce some of the infection. There are no fungicides labeled for control.

We see other juniper disease problems in Missouri, however Kabatina tip blight is seen most commonly in late winter and early spring affecting last year's growth. For more information about the disease, you can visit our Web site.

Simeon Wright
Plant Diagnostic Clinic Coordinator

Sycamore leaves fall in spring

Do you know what is wrong with the sycamore trees this spring? Mine have dropped a lot of leaves. Most are green and I noticed up in the trees there are quite a few dead leaves. Is it a freeze problem or insects? Will they recover? I think some of them are getting new leaves.

The problem with the sycamores is being caused by a fungal disease called anthracnose. The disease attacks sycamores every year, but tends to be worst in years when there is a cool moist period in spring. Although our spring was fairly dry this year, recent rains have allowed the fungus to attack the new leaves of the sycamore and cause them to collapse. Generally, once the temperature gets hot and the rains are less frequent, the disease stops working until the following spring.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Compost confusion

I am a novice at making compost. I have a few questions based on my six-by-four-foot compost pit that will consist mostly of shredded dried leaves:

Because I don't use grass clippings or any other natural nitrogen source, how much blood meal that is 20 percent nitrogen should I add to the pile?
If I add a compost starter additive, do I still need to add a layer of soil because the starter will have various microorganisms in it?
What is the ideal ratio of carbon to nitrogen in a compost pile? MU Extension states it's 30:1. Another Web site stated 4:1.

Assuming that 100 pounds of dried leaves is about 50 percent carbon and contains about 1 percent nitrogen (50:1), you would need to add about 1.5 pounds more of nitrogen to get a 20:1 ratio. This would require about 8 pounds of blood meal per 100 pounds. It will compost a lot better because you shred the leaves.

If you add soil, you should not need compost activator.

A material with a carbon-to-nitrogen ratio of 4:1 has way too much nitrogen and would be likely to create a foul odor if composted directly. A carbon-to-nitrogen ratio of somewhere between 20:1 to 40:1 should compost well without causing odor problems.

Chris Starbuck
State Extension Specialist
Woody Ornamentals