Yard and Garden: July 7, 2017

Yard & Garden for blog, 2017

This is the Q&A for the Yard and Garden show for July 7, 2017. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through July 28, 2017. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.

Guest Host: Bob Henrickson, Assistant Director of the Nebraska Statewide Arboretum

If you enjoy reading my Q&A from the show each week, take my quick survey at: http://go.unl.edu/44qr and be entered to win a free plant book or some free UNL gifts.

1.The first caller of the day has 10 lilacs growing in a lawn which are now getting a gray film on the leaves. What is causing this problem?

A. This is due to powdery mildew. This is a common problem on lilacs. Lilacs often get this disease if they are planted too closely together reducing air flow or if they are planted in heavy shade. If these plants are not growing in either of these environments, it is likely due to the wet spring we saw this year. Fortunately, this disease is not very damaging to the plants and there is no need to treat for it.

2. A caller has many American elm trees growing in his pasture that seem to suddenly be dying this year after the leaves turn brown and curl up on the branches.

A. Unfortunately, this is likely due to Dutch Elm Disease, which is still present and active in Nebraska. Many of our trees can grow for a few years and then the trees get large enough and conditions become conducive, that it shows up and kills the trees fairly quickly. The only management strategy is to remove and destroy the infected trees to reduce the spread to other trees.

chicory, Joseph M Ditomaso, Univ of CA-Davis, bugwood

Photo of Chicory from Joseph M DiTomaso, University of California-Davis, Bugwood.org

3. What are the blue flowers blooming along the roadside now and can the seed be purchased somewhere?

A. That is chicory, a non-native plant often used in roadside mixes. The seed can be found in some roadside mixes or at local seed sources.

4. A caller has a sunset maple with leaves that are curling and falling off the tree. What could be wrong with the tree?

A. This could be due to herbicide drift. Trees stressed by herbicide drift will often lose their leaves and push new growth. As long as they are producing new leaves that are not curled, the tree will likely be fine. However, many years of damage from herbicide drift can cause more stress and even possibly death.

5. This caller has voles in their yard. How can these be controlled?

A. Snap mouse traps can be placed in the runs perpendicular to the runs. These traps will catch and kill the mice. Here is a guide on vole control

6. A caller has a copper-colored beetle in her elm trees that are causing holes in the leaves. What would this be and how can they be controlled?

A. This could be a Japanese Beetle, an invasive insect from Japan. It is a green beetle with copper-colored wings. These beetles need to be controlled as they can do a lot of damage quickly. They chew on the leaves causing a skeletonization of the leaves as they leave behind the leaf veins. They can be treated with a insecticide containing imidacloprid.

7. A caller has a grass that grows in her lawn. The grass grows in a large circle about the size of a dinner plate and tends to turn brown in any kind of drought when the rest of the lawn does fine, but thrives in higher moisture content. What would this be and how can she make her lawn look more uniform?

A. This could be a cool season weedy grass species. They are often found in our lawns growing in a large circle. I would recommend spot spraying the areas of this different type of grass and then reseeding. This would be best done this fall. Be sure to spray the spot while it is still green and actively growing and use a product such as glyphosate. Overseed the areas in September.

8. This caller has hollyhocks with brown spots on the leaves. What could this be from?

A. This is likely due to hollyhock rust, a common fungus of hollyhocks. Remove the leaves as they develop the disease and destroy the leaves and plant parts removed in the fall cleanup. Fungicides can be used if necessary, such as a liquid copper fungicide.

9. A caller has peach trees that have developed some insects in the peaches making them unedible. What can be done about that?

A. There are a lot of different insects that feed on the fruits of peaches. The oriental fruit moth is one. For any fruit tree, either deal with some insect and disease damages throughout the years or keep your trees on a spray program. Spray every 10-14 days throughout the growing season with an Orchard fruit tree spray that contains two insecticides and a fungicide. Avoid spraying during full bloom. For more information, visit food.unl.edu/local-food-production

10. This caller has a sycamore that has shed some leaves and is now shedding bark. What is wrong with the tree?

A. The shedding bark could be normal. Sycamore trees have an exfoliating bark that is normal to give it the camouflage bark appearance. It may have been hit earlier this spring with anthracnose causing the leaves to drop. Anthracnose is a minor, but common, disease of sycamore trees. It is more prevalent in wet weather, such as this spring. There is no control for it, but the tree should be fine.

11. A caller has been trying to seed grass where a septic tank was and can’t get it to grow. What is wrong?

A. At this point in the year, it would be best to wait until fall to plant grass seed due to the heat, humidity, and lack of rain. However, if you have been trying in the spring and fall and can’t get it to grow, I would recommend getting a soil test done of the soil where this problem is occurring. This will help tell if the soil has other problems because of the septic tank or what was put back into the hole. It was also determined that this is an area around a large tree with a great deal of shade, if the area is too shady for grass, try a groundcover or a carex species that will grow better in more shade.

12. When is the best time to spray for bagworms?

A. Now would be a good time since the bags have emerged. Make sure you spray before the bags are 1 inch in length for best control. You can use any general insecticide for controlling bagworms such as sevin, eight, bifenthrin, tempo, or Bt can be used for a safer control method. Bt will not harm bees and other beneficial insects.

13. A caller has a Norway Spruce that is 8 feet tall. It has been drying up since this spring and looks like it is dying. The tree has been planted here for 5-6 years and is watering slowly every 2 weeks since the trees were planted. What is causing it to die?

A. This could be due to overwatering. The roots of the trees need to breathe in between waterings. If the caller is filling a moat around the trees with water every 2 weeks for this many years, it would be excessive.

14. The final caller of the day wondered if the yard could be sprayed to help with chiggers? He also wondered when the time was to use sedgehammer on the lawn?

A. Nothing can be sprayed on the lawn to entirely help with chiggers. The best defense against chiggers would be to use insect repellent that contains DEET and to wear light colored clothing. Sedgehammer is best used before June 21st or the longest day of the year to help reduce the populations of nutsedge for next year. However, it can still be used this late in the year to kill what is in the lawn this year.

Advertisements

Leaf Spot Diseases

Rainbow

Spring rains are always great for our plants. It helps to replenish our lakes and streams and helps bring the soils back to a point of good saturation after a dry winter and before a dry, hot summer. However, when we see many days with a lot of rain and overcast skies, this can also be detrimental to our plants.

This year we are seeing a lot of fungal leaf spot diseases that look terrible on our trees. These leaf diseases are causing the leaves of many of our deciduous trees to get brown spots, turn yellow, and eventually fall off of the tree. As damaging as this looks, it is actually a minor disease and does not cause major stress to the trees. The diseases we have been seeing include anthracnose, ash rust, cedar-apple rust, apple scab, and other leaf spots.

ash anthracnose, Jason Sharman, Vitalitree, bugwood

Ash Anthracnose Photo by Jason Sharman, Vitalitree, Bugwood.org

Anthracnose is a fungal leaf spot disease that can occur on many different host trees and shrubs. There are a number of fungi that cause anthracnose and typically they are host specific. What this means is that there are a lot of different trees that are affected by anthracnose, but oak anthracnose is only found on oak trees, ash anthracnose is only found on ash trees, and so on. So, the disease won’t spread between tree species but multiple fungi may be present in a landscape.

The symptoms of anthracnose include small brown or dead spots on the leaves, dead leaf margins and tips, large dead blotches between the leaf veins and premature defoliation may also occur. If premature defoliation occurs early in the growing season, the tree should put on new growth, so don’t be too concerned if many leaves fall off the tree this spring. This is often a problem on the lower and inner leaves and branches most heavily while the top of the tree and outside ends of branches will show little to no symptoms.

Anthracnose is a disease that thrives in cool, wet weather like what we saw this spring. The disease is less of a problem if the temperature is above 60 degrees when the buds begin to break dormancy in the spring. Anthracnose overwinters in diseased leaves and branches that are left on the ground. Be sure to always rake and destroy fallen leaves around susceptible trees. Because this disease is not very damaging to the plants, there is no need to use pesticides for control. In the summer heat the disease will fade out.

Ash rust is another disease we will be seeing soon if we haven’t already seen it in our ash trees this spring. This shows up as orange spots on the leaves. On the underside of the leaves, finger-like protrusions may develop, for the spores to spread. As with Anthracnose, this is not a harmful disease to the tree. It is best to discard all of the fallen leaves each fall and maintain mulch around trees.

We are also seeing a problem right now called Hackberry decline. Many of our hackberry trees in the area are losing most of their leaves and it looks like fall. This decline is due to many stressors to the tree such as herbicide injury, drought, poorly drained soils, and weather extremes. All of these problems have been occurring to our trees over the past few years and the combination of these problems is starting to cause problems to our trees. This is something that the tree should overcome and there is no control for it.