Yard and Garden: April 8, 2016

Yard & Garden for blog

This is the Q&A for the Yard and Garden show for April 8, 2016. 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 August 5, 2016. 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 Hosts: John Fech and Jonathan Larson, Nebraska Extension Educators for Douglas/Sarpy Extension

1. This caller has rye grass that is turning yellowish-brown after it was already greened up this spring. What is causing this brown coloration?

A. Take a look at the roots of the turf in these brown areas, see if they have dried out. Also, rye grass is more susceptible to winterkill than tall fescue or Kentucky bluegrass is and with these inconsistent temperatures and fluctuations we have been seeing this year, there is more chance that this turf was damaged from the winter conditions. Overseed the lawn now with a better suited turfgrass for Nebraska and delay crabgrass control until Memorial Day.

2. A caller has seed potatoes that he will be planting. How long should the sprout be on those potatoes?

A. This is not an issue, there is no need to worry about the length of the sprout. The issue with planting potatoes is to make sure that there is at least 1-2 eyes on each potato you plant.

3. Would it work to put a patio heater near a pear tree to protect it from damage from the freeze that is predicted for tonight?

A. This would not be feasible to keep the entire tree warm enough to protect it from a freeze occurrence. There is also a fire hazard issue I would be concerned with. For trees that are already blooming, there is really no way to stop the damage to the fruit formation that will come from freezing temperatures overnight.

4. This caller planted his potatoes on St. Patrick’s Day, as the old saying goes. However, they still have not emerged this spring. Is this a concern?

A. This year, St. Patrick’s Day may have been too early. The soils are still quite cold and wet which may cause concern for these potatoes. We would suggest digging up one of the potatoes to see if it is still viable or if it has started to rot in the ground.

5. The previous caller also asked whether a barrier spray with sevin around the garden might help reduce cucumber beetles in the garden?

A. This could work to catch some of the overwintering insects as they move into the garden. It may help to reduce the overall population in the garden.

6. A caller was wondering about the fate of their perennials and flowering shrubs with this freeze warning for tonight, mainly peonies, iris, and daylilies?

A. These plants are more adapted to Nebraska climates so they should be fine. This weather may cause them to lose some buds or cause some black coloration to the blossoms or leaves, but for the most part these will survive. If it is a concern for you, you may want to cover these plants with a sheet or blanket overnight tonight, but remove this during the day.

7. This caller has grass that is green but has large patches of yellow or straw coloration throughout the yard. What is causing this and how can it be fixed?

A. This sounds like a warm-season, grassy weed called nimblewill. This should be controlled in your lawn as it will take over. It can be sprayed with a glyphosate product, such as roundup, and then overseeded. This would need to be done in the fall so that you can spray the nimblewill when it is green and the fall is a good time to overseed. You can also purchase a product called Tenacity to control the nimblewill and harm the grass. Or you can call a lawncare company to control it for you.

8. A caller has apple trees near a cedar tree windbreak. Last year, the apple trees got rust disease. How can this be controlled? Should the cedar trees be removed?

A. Don’t cut down the cedar trees. The spores for cedar-apple rust can spread up to 2 miles and in Nebraska it is very difficult to get that far away from a cedar tree. It would be best to start with newer varieties of the apple trees that are resistant to cedar-apple rust. You can also spray your trees for cedar-apple rust. There is a very good Nebguide on Cedar Apple rust from Amy (Ziems) Timmerman found at: http://extensionpublications.unl.edu/assets/pdf/g1907.pdf

Twig Girdler Insect
Damage from Twig Girdler

9. This caller has 2 Linden trees in his front yard. With the windy days lately, many small twigs have blown out of the trees and it looks like an insect cut the branch off. What is causing this and what can he do about it?

A. This would be a small insect called a twig girdler. They will chew around the branches and make it fall off from a smooth cut. There is no insecticide necessary for this insect, it is best to just collect the branches and dispose of them.

2016-04-08 11.03.23
Greenbriar plant

10. A walk-in client was wanting an identification on a very thorny, green stemmed plant they have found growing up their trees and throughout their property.

A. This is a plant called greenbriar. It can be cut off repeatedly or in areas that are not in flower or vegetable gardens a brush killer product can be used.

11. A gentleman has a 5 year old azalea plant that isn’t blooming, what can he do to improve the blooms?

A. This is a plant that is inconsistent in our environment, we are on the edge of their growing zone. They also like more acidic soils and more protection than what we can often give them. It would be best to move it to a location of morning sun and afternoon shade. You can also add some fertilizer for acid loving plants, similar to what would be applied to blueberries or hydrangeas to give them a blue flower.

12. This caller has a black walnut trees in an old windbreak. Can they grow pampas grass or trumpet vines in close proximity to these black walnuts without detrimental effects?

A. Grasses are not usually affected by the juglone that is produced by the black walnut trees to deter other plants from growing near them. This juglone is produced to naturally reduce competition from the black walnuts with other plants. Trumpet vine should be tolerant because they are a tough plant.

 

Fall Insects & Weeds

fall landscapeWith fall coming right around the corner, many things are going on in our landscapes. There are many weed species creeping their way through our trees and lawns. We are also having a great deal of problems with many nuisance insect pests in our trees. The following are the horticultural pests I have had the most calls on over the past couple of weeks that I feel the majority of the public is trying to deal with.

2015-07-30 17.00.35We are seeing wild cucumber covering up trees in our windbreaks. This weed is very similar to cucumber vine that you grow in your vegetable garden and it grows up and over our trees, especially through windbreaks. If left on the tree, most often the tree will survive, but in some cases, this vine can smother the tree from sunlight and cause death. It is very easily pulled and can be treated with general herbicides, such as 2,4-D, but only as a stump treatment or carefully painted on the leaves.

Another problem that many people are facing this year is the issue with high populations of crabgrass in lawns. With all of the spring rains we had this year, many weeds are taking over our lawns. Crabgrass is a warm season annual so it germinates early in the spring and dies with the first frost of the year. What is in your yard now, does not need to be controlled as it will die in the next couple of weeks. Just remember to apply a crabgrass pre-emergent herbicide in the spring next year.

Damage from Twig Girdler
Damage from Twig Girdler

I have had numerous calls lately on small branches on the ground all around large trees. This is most likely due to a couple of beetle insects, the twig girdler or the twig pruner. These are two very similar insects that cause similar damage to trees. These insects will chew small branches of trees causing them to fall out of the tree on windy days. The twig pruner causes branches to have a jagged edge where it tears from the tree after the inside is chewed. Twig girdler causes branches to have a very smooth cut on the outside of the branch, like it was pruned off with a pair of pruning shears. Both of these insects cause minimal damage, it is mainly an aesthetic nuisance to the tree. Chemical treatments are not necessary or recommended for treating twig girdler or twig pruner.

Fall Webworm photo by G. Keith Douce, University of Georgia, Bugwood.org
Fall Webworm photo by G. Keith Douce, University of Georgia, Bugwood.org

One thing that we all see as we drive around Nebraska right now, is fall webworm. Fall webworm is the immature form of a medium-sized white moth. The caterpillars form webbing at the ends of branches of many deciduous trees in the fall. This webbing entangles and kills the leaves within it, and causes no further harm to the tree. They are not necessary to control with chemicals and it is not effective to get chemicals through the webbing. If they are not wanted in your tree, for aesthetic reasons, they can be pulled out with a broom and put into a burn barrel (where permitted) or a bucket of soapy water.

Twig Girdler & Twig Pruner Insect

Leaves on the ground in the FallIt’s fall now, so we are seeing all of the leaves fall to the ground off of our deciduous trees.  However, be alert as some of these leaves may be a portion of your branch that was removed from the tree by an insect.  Fall is the time of the year when we tend to see the damage from twig girdler and twig pruner insect.  I found the damage from twig girdler in in my yard when I went to look closer at all of the leaves on the ground around my cottonwood trees.  Many of the leaves I found were actually branches that looked like they had been pruned off my tree.

Twig girdler and twig pruners are two insects that tend to do similar types of damage to the tree.  Most of the time they work through “pruning” the tree during the late summer, but the damage isn’t seen until the fall when the branches fall out of the tree due to wind.

Twig Girdler InsectTwig girdler is a cerambycid beetle, or longhorned beetle.  This insect will chew a v-shaped groove in a circle all the way around the twig, girdling it.  Often times, the center of the twig will be jagged while the outer edge is smooth.  These will feed from August through October allowing the branches to fall over that time or shortly after due to wind.  After creating the groove in the wood, the female will lay an egg in the portion of the branch that eventually falls to the ground.  The larvae cannot feed on healthy wood, so it is able to feed on the dead branch after it falls to the ground.  These larvae will then overwinter in the dead branch on the ground.  In the spring they will pupate in that branch and develop into adults to start the process over again.

Twig pruner is another type of cerambycid beetle, or longhorned beetle.  The lifecycle of the twig pruner is very similar to that of the twig girdler; however they will usually chew on the small branches from the inside out.  Twig girdler insects will drill a small hole into the branches in the spring and then grow throughout the summer.  In the late summer, the full grown larvae will chew rings through the branch until they have made it through the whole branch, except for the bark layer.  The larvae then move into the portion of the branch that eventually falls to the ground or hangs in the tree, dead.  The pupae overwinter in the dead portion of the branch and emerge the next year to start the process over again.

Capture

The damage from twig girdler and twig pruner is not very damaging to the tree itself, but mainly looks unsightly for the homeowner, and makes for a large mess in yards that we have to clean up.  Control for both of these insects is very easy.  The best control method would be to pick up the fallen branches and destroy them by burning them prior to emergence of the insects in the spring.  Any broken branches should also be removed before the spring in case they are infested.  Chemicals are not usually necessary or recommended.