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Sunday, August 16, 2015

Identifying Their Damage and Controlling Borers

Q. I am having a problem with a bug infesting my trees. I haven't identified the pest but I wanted to first ask how did this infestation happen or if it's common in the Vegas Valley and second how is the cycle of reproduction of this bug?

Flat headed borer taken from tree
A. Thanks for sending the pictures. You have taken the larva or “worms” of a beetle from this tree. These larva or worms are called borers. You can notice the flattened head of this worm so it is commonly called a flat-headed borer.

I think it is either the Flatheaded Apple Tree Borer or Pacific Flat Headed Borer. I have been following this insect and its damage for many years in this valley. The adult of this “worm” is a beetle about ½ inch long.
Borer damage on Apple when first seen

The adult female beetle flies around searching for a mate so that it can lay its eggs. It finds a male by “smelling” the male’s pheromone it releases. Most likely this happens any time from about April through August. Once the female mates and prepares to lay eggs, she searches for suitable woody plants that are injured or unhealthy.

Extensive borer damage to Locust
This insect is part of an “ecological recycling cycle” helping plants that are on the decline continue in a downward spiral toward death. However, I have found this insect in trees that appear to be very healthy as well. The female laden with fertilized eggs searches for suitable plants through her sense of “smell”. One of the “smells” she identifies is damage of plants from sunburn.

Discoloration and canker to scaffold limb because of sunburn
High light intensity of our desert sun shining directly on the bark of trees that are thin and don’t provide much insulation become damaged and frequently die in the damaged area. Death in localized areas of the branches and trunk of woody plants leaves behind a “canker” in the surface.

Sunburn damage to Japanese blueberry
The smells and aromas of damaged plants attract the egg-laying of flat headed borers. She lays her eggs in the general vicinity of the damage but on top of healthy tissue. The very tiny worm or larva “hatches” from this egg and tunnels inside the plant just under the bark.

Borer damage to flowering plum
The wood just under the bark is laden with wet, sugary juices from the plant which the flatheaded borer feeds upon. As this flat headed borer feeds, it inches slowly forward just under the bark making a convoluted tunnel. At the beginning of this tunnel is the flattened head and it leaves a trail of sawdust and feces behind it as it feeds, moves and creates the tunnel. I can sometimes push on the bark covering the surface of these tunnels and feel a difference in the “hardness” of the stem.

Borer feeding under the bark inside peach tree limb
This borer matures (pupates or turn into an adult) inside the tree, exits the tree as a winged adult and searches for a mate to repeat the lifecycle. Sometimes, if it is late in the season, this borer will tunnel into the center of a limb to survive the winter and exit as an adult the following spring.

Borer feeding just under the bark of peach tree limb
Borers attack dozens of different trees and shrubs, many in the Rose family. This includes many of our fruit trees, landscape plants in the Rose family like Pyracantha and flowering plum and numerous others as well.

What to do?

Dig it out. Using a sharp and sanitized knife and laying it almost parallel with the branch, I will cut away the surface of the branch to expose the tunneling. I will remove all of the surface bark where there is damage. I will clean the surface bark all away until I have nothing but fresh wood remaining. In this way, I expose the tunneling and the source of protection for the boring insect. This exposes the hiding place to predators of this soft bodied “worm”.

Borer control using a sharp, sanitized knife
Prune it out. If the damage is more than 50% of the branch, I will remove the branch. If removing the branch seems excessive, I will not remove it and give it a chance to heal.

Using insecticide. In a last ditch effort I will use is a soil applied systemic insecticide. I never use these on fruit bearing trees but on ornamentals only. I will use these on non-flowering ornamentals because it is suspected that this systemic may impact bees visiting the flowers. If the tree produces flowers, I time the application of the insecticide just after the time of flowering.

One of the insecticides containing imidicloprid systemic for borer control
Whitewash to prevent. Whitewashing the upper surfaces of limbs, scaffold limbs and the trunk reduces sunburn which should also reduce problems from borers. I make the whitewash by mixing white latex paint 1:1 with water. You can also buy commercial whitewash. In the old days, it was made from lime.
Whitewashing fruit trees in the winter to help prevent sunburn

Pyracantha Does Not like Rock Mulch

Q. I have a hedge of pyracantha on the northeast corner of my property. It is 16 years old.  It grows underneath three large pine trees.  It does not get much sun. The soil, if you can call it that, is mostly just rocks. The plant is thinning and getting bare in the center. The top is still fairly green. The amount of berries in the winter has been decreasing. I dug around the roots as much as I could and amended the soil with Paydirt. I added about a cup of sulpher and some bone meal to the amended soil. I plan to add fertilizer in a couple of weeks. What more would you suggest?  By the way, there is very little yellow on the leaves.

A. Pyracantha is in the Rose family and so it likes soils that are similar to fruit trees in the Rose family. This includes apples, pears, peaches, apricots and the like. It is also susceptible to some of the same problems as fruit trees in that family. It isn’t terribly fond of desert landscapes and rock mulch.

Dwarf pyracantha in winter hedge sheared
Without seeing it I am guessing it is a combination of light as you mentioned, lack of soil improvement, perhaps irrigation, maybe improper pruning and borer problems. Pyracantha needs a lot of sun but it is thin-barked so it sunburns easily if it’s canopy is open. Sunburn leads to borer problems. It is not a desert plant so it likes improved soils and wood mulches. It would like surface mulches made of wood that can decompose. Rock mulch will mineralize the soil over time and it does not like this.

Pyracantha fruit in winter. Pyracantha or Firethorn is in the Rose family.

Pruning is a little tricky but should result in shading any exposed trunk or major branches. From your description it sounds like it has been a hedge pruned; pruned with a hedge shears not pruners. It hedges nicely but I don't recommend this unless you plant it as a hedge. As far as borers, you would see the trunk or major limbs with bark coming off and some darkened areas because of sunburn. Borers can be active for a couple of years and cause no obvious visual damage. There is an insecticide you can apply to the soil that gives the plant season-long control of borers if it is a problem.

Pyracantha in bloom in the spring
So what to do? Check the irrigation and make sure it's getting enough water or increase the amount it gets. I would not increase how often but the amount it receives each time. Pull rocks away from the plant and put down 3 to 4 inches of compost and wood mulch. When pruning, be very careful you don’t open the canopy up too much which might allow sun burning the trunk and limbs. Fertilize once a year in the spring with a fertilizer formulated for flowering woody plants. You can substitute a rose fertilizer which will work. Apply a soil insecticide as soon as you start to see new growth. I hope this helps.

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Hibiscus Blooming but Leaves Too Small

Q. My hibiscus plant, which I planted from a pot to my outdoor flower bed, is blooming like it should.  The problem is, that the leaves are not getting any bigger than 1 - 1½" long and ¾" wide.  The new leaves also only get to that size.  I water and fertilize if with Miracle Grow regularly, but that does not help.  Any suggestions?

A. The appearance of plants will be different when growing in different climate zones. Appearance can also be impacted by your management practices. Let's cover a few of these.
Red hibiscus growing on our farm, Moca Family Farm, in the Philippines
Climate and Microclimates. Plants growing under high light intensities will have a different appearance then plants growing under lower light intensities. The principal differences are in leaf size, color and thickness. 

Leaves growing under higher light intensities, provided they are getting enough water and nutrients, will be dark green, they will be smaller, thicker or tougher and develop a thicker waxy coating on the leaf surface. The same plant growing under lower light intensities will have larger and thinner leaves with a waxy coating that is not as thick. 

If light intensities get extremely high then we will see leaf discoloration, yellowing or bronzing, on some plants because the light intensity is actually damaging the leaves. If the same plant does not receive enough light then the plant will become “leggy” with large distances between the leaves and thin stems that will not support its own weight. The plant will become "floppy".

Our job as a manager of this plant is to find the right location in our landscape, the right microclimate, that will give it enough light so that it will flower and have an appearance close to what we expect. Because we are in a desert, Hibiscus might not look exactly the same as it does in semi tropical or tropical climates but we can approach that look if we are careful where we plant it.

Fertilizer. The selection of the right type of fertilizer and amount of fertilizer will, to a large degree, influence the type of growth we get from a plant. We know for instance that phosphorus fertilizers are very important for flowering, fruiting, root development and production of oils in plants. 

If not enough phosphorus is present for the plant to use it will impact this type of growth. If too much is present, it can also impact growth of plants by "messing up" the soil chemistry. If fertilizers are applied to the soil, we generally do not need to apply phosphorus frequently.

Nitrogen is a different animal. Nitrogen is important for developing dark green color in leaves and stems and for "pushing" new growth. It is important in producing good leaf size and in the number of leaves and supporting stems produced. 

The nitrogen in soils available to plants are in "salt" form. Applying too much nitrogen can result in leaf burning or scorching along the edges and even plant dieback or death if excessive amounts are applied. Unlike phosphorus, nitrogen is removed from the soil fairly quickly unless it is in organic form. 

The nitrogen will be depleted in 4 to 6 weeks through plant uptake and removal from the soil by the irrigation water and "evaporating" into the air. Organic nitrogen is removed much more slowly and gives the plants a "steady feeding" of nitrogen over a longer period of time.
In your case you want to make sure that nitrogen is applied regularly through the growing season to maintain dark green color and "push" new growth. Combined with moderate amounts of shade, nitrogen will encourage more leaves and larger leaves.

Soil. Organic matter such as compost mixed into the soil at the time of planting and applied at least annually to the surface of the soil surrounding the plant will encourage more leaf production and larger leaves on those plants which have it in their genetics to produce this kind of growth. I have seen this numerous times on a number of plants particularly in parts of the plants that are shaded such as lower leaves.

What do you need to do? Understand that if your hibiscus is in a very hot, bright location that this location will limit the plants ability to produce larger leaves. Moderate amounts of shade will encourage larger leaf development, particularly in a microclimate that gets morning sun but afternoon shade. 

Get some compost and dig it into the soil surrounding the plant as much as you can. Apply about 1 inch of compost to the soil surface after you are finished and thoroughly wet the soil deeply immediately after you apply. At least once a year apply compost to the soil surface surrounding the plant and water it in thoroughly. 

Apply phosphorus either to the soil or to the foliage as a foliar spray at least once a year after it is finished flowering for the season. Apply high nitrogen fertilizers to the soil surrounding the plant in early spring, early summer and late summer. Winter tender plants should not be fertilized with high nitrogen fertilizers after August 1.

The three overall factors that will determine the leaf size: 
  • what it's capable of producing genetically (if you know this plant can produce much larger leaves but it is not doing it), 
  • soil improvement, and 
  • application of nitrogen fertilizers.

Oleander Leaf Scorch Disease a Rarity in Las Vegas

Q. We are thinking of putting in a new oleander bush/tree.  But we are concerned about oleander leaf scorch affecting our new plant in the near future.  We've read where the disease has killed oleander in California and Arizona. Has it been found here in the Las Vegas and/or Nevada as a whole?  If not here now, is it wise to put in a new plant?

Oleander with leaf scorch
A. I rarely see any problems on oleander here. Oleander leaf scorch usually occurs in Southern California and not in southern Nevada. I know our state plant pathologist has been watching for it here and is taken several samples looking for it. 

There has been some debate about whether this disease in oleander can be transferred to grapes and cause a similar disease and appearance called Pierce’s Disease. The researcher is pretty firm that it does not.

For more information on oleander leaf scorch I would refer you to the University of California website. If you are convinced that your oleander may be diseased with leaf scorch, contact the Nevada State Department of Agriculture.

Freeze damage of oleander and recovery in the spring
 Diseases are very rare but do happen occasionally. Nothing to worry about. Keep the plants healthy with plenty of water and mulch the soil with organic mulches when possible. Some oleanders are more tender during winter freezes than others. When oleanders become overgrown and woody, cut them within a couple of inches of the ground in the winter and let them grow back from these stumps.

Salt Cedar Removal from Landscapes Is Difficult

Q. What is the best way to remove Salt Cedar, mature trees and the seedlings that are sprouting all over the yard?  Would appreciate any advice you might be able to offer.

A. You should consider getting rid of it but I will warn you it will be difficult. Salt cedar, or tamarisk, produces hundreds if not thousands of seeds every year. The seeds will germinate easily even floating on water or submerged in flooded soils.
Salt cedar is a problem because it uses so much water and kills other plants growing close to it by pulling salt out of the soil, concentrating it in its needle-like foliage and dropping this salt load on the soil surface.
The salt concentrations are so high, very little will grow in these areas. The other problem is that it suckers easily from its roots so just cutting it down will cause it to sucker in many other places.
The most effective way has been to cut it down as close to the soil as possible and apply weed killers to the fresh surface of the cut. Another method is to drill holes in the trunk close to the soil and inject weed killers into these fresh wounds. The two most effective weed killers have been Roundup (glyphosate) and Garlon (tyriclopyr).
The label will tell you the concentration you should use. The best time for treatment is in the fall months just before plants are preparing for winter, not the spring. In our climate this would be October and perhaps early November.
After the tree has been injected and begins to die, you will probably see suckers growing from the roots in a last ditch effort to stay alive. Cut these suckers close to the ground and daub on the fresh cut ends with the same solution.
Do not make the mistake of thinking that a greater concentration of the chemical will give a better kill. Use the labeled concentrations. These were established by the manufacturer and tested in the field.
Seeds from the mother plant may continue to germinate for a long time after the tree is dead and been removed. When these seedlings emerge from the soil, kill them immediately. They can grow 1 foot or more every month during summer. Their roots grew first before the top so it will be deep. 
All of these years I have been working near and around salt cedar and I have no pictures of it. If any of you have some that are yours, send it to me and I will post it here.

Peach Tree Life Limited by Borers

Q. I have a peach tree that has produced magnificent fruit for over 15 years- for the past two seasons I have seen no production or at best tiny fruit that doesn't mature- I have studied your blog and believe that my tree has peach tree borer damage. I live in southern California- zone 9. Should I try to save the tree or is it a lost cause and if so what applications can I use to restore it? I prefer organic methods.

A. I am more familiar with the problems in the Mojave Desert but I would probably agree with you that it is some type of borer. 
Peach trees can be fairly short-lived in many locale because of borers. This includes other countries I have visited. The borers are different but the result is the same. At our orchard in North Las Vegas peach trees that are 15 years old are getting up there in age and a 20 year old tree is old. 
All that being said you can always find someone who has a peach tree that is 40 years old but it is rare and they were lucky or possibly the variety but trees that old are usually not productive any more. 
I would remove it and replace it with another this fall if you can find a variety you like. If you are in a very temperate part of southern California like the San Diego area or along the coast you could do it any time. In the hot desert area, wait until it cools off.