Hunt County Master GardenersTexas A&M AgriLife Extension Service

Brown Patch

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Brown Patch by Charles Bohmfalk

It is that time of the year when we are now entering the fall season that brings cooler weather and humid, rainy conditions.  These conditions when the overnight temperatures are below 70° F and the daytime temperatures are in the 75° F to 85° F range can lead to many problems in the lawn.  Brown patch is one of the lawn diseases that becomes a real problem in our lawns during the cooler and more humid weather conditions in the fall and early winter months.  A number of popular lawn grasses are susceptible to brown patch: Berumda, Carpetgrass, Centipede, Fescue, Kentucky bluegrass, St. Augustine and Zoysia.  Other grasses may be infected as well.  Brown patch may be identified as circular or irregular shaped patches of light brown, thinned grass.  The grass may appear yellowish and have a smoke ring on the outer edge.  Leaf sheaths become rotted and a gentle pull on the leaf blade will easily separate the leaf from the runner.   Most fungicides will do an effective job if used as a preventive treatment.  Brown patch may be harder to control once the fungus is established.  The Texas A&M website (aggieturf.tamu.edu/answers4you/disease/brownpatch.html) lists some of the more effective fungicides.  There are other fungal infections that may resemble brown patch.  The same fungicide may control that problem as well.

I recently had a brown area in my lawn.  Brown areas caused by grub worms will show a browning or the appearance of a lack of water in the area.  The damage may be a small spot or cover a large area and is caused by white grub worms, the larvae of the May or June bugs.  The larvae feed one to two inches below the surface and destroy part or most of the root system of the lawn.  Damage usually appears in late July through early August.  If the damage is heavy, the sod can be easily lifted up or rolled up.  To verify that the problem is grub worm damage, dig one square foot sections to a depth of 4 inches.  Treatment with an insecticide is necessary if more than four grubs are found per square foot.  Since my lawn damage was in an area where I have had a problem with grub worms before, I treated the area with an insecticide.  The grass is already showing good signs of recovery.  If left unattended in the fall, the grub worm will survive over winter and become very active in the early spring.  By this time, the grubs have done more significant damage to the grass roots and large areas of the lawn may not survive the winter.

Cinch bug damage appears as irregular patches in sunny areas, usually along driveways, sidewalks and house foundations.  The grass first turns yellow and eventually dies and turns brown.  To identify a chinch bug infestation, remove both ends of a metal can and twist it into the grass.  Fill the can with water and a little detergent.  In a few minutes, the chinch bugs will float to the surface.  They are black with white wings folded over the body.  Treat with an insecticide that has cinch bugs listed on the label.  Read the label and carefully follow the directions when using any fungicide or insecticide.

Rose Rosette Disease

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Rose Rosette Disease by PJ LaRue Smith

Rose rosette disease (rose witches broom) has been getting more press the last several years in the Dallas/Ft. Worth area due to the increased infection rate noted at several homes and public gardens.  This disease is particularly devastating in that (a) there is no cure, (b) infected bushes must be removed/destroyed, and (c) all roots of infected plants must be dug up before replanting roses in the same location.

Symptoms of rose rosette disease include witches broom formation of new growth, twisted flowers and leaves, excessive leaf growth, excessive thorniness, red and/or mottled discoloration, lateral shoot elongation, flattened stems, and enlarged stems. Not all symptoms may be noted on affected plants, and can differ amongst rose types.

What causes the disease?  In 2011, a research group from the University of Arkansas reported the detection of a virus, specifically an Emaravirus, in symptomatic roses. They were able to detect this virus in 84 out of 84 symptomatic plants that were tested (Laney et al, 2011). This study also resulted in a genetic (PCR) test to detect the virus. However, the procedure can be tedious and is currently undergoing further modifications to simplify for ease of use.

How does the disease get into, or transfer from, plant to plant?  Evidence from mite transmission studies suggest that the eriophyid mite (Phyllocoptes fructiphilus) carry/transmit some disease causing agent from the diseased plant to healthy ones.  (There has not been any published study that clearly demonstrates that the eriophyid mite actually carries the rose rosette virus itself, however.)

How do you know that a rose has this virus?  Symptomology as described above, once other factors such as herbicide damage (especially products containing 2,4D), abiotic environmental conditions (i.e. sunlight, temperature, wind patterns, precipitation) and damage by other insects have been ruled out. Presence of the eriophyid mite along with the symptoms listed above further substantiate the conclusion of rose rosette disease.  Electron microscopy and other molecular tests can detect the virus, but are typically not done in the average home garden.

Can the rose rosette affected plant be left in the garden?  Most of the time, this disease will damage the rose plant to the point where it simply dies.  However, the infected plant can serve as a virus reservoir for transmission by the eriophyid mites to healthy bushes.  So removing/destroying the plant is the best option for further spread of the disease.

What is the best management practice when this disease is discovered in a garden?  According to Texas A&M AgriLife Extension Service publication E-PLP-010 (August 15, 2013):

1. Removal of confirmed and/or symptomatic plants early after observation.

2. Treatment of adjacent plants with miticide to reduce probability of transmission by eriophyid mites. (Please note: this will not stop the virus, if it is already in the plant.)

3. Constant monitoring (weekly) for symptoms and rapid action when and if symptoms are observed.

4. If desiring to replant with roses, it is advisable to remove all diseased plant roots from the soil before replanting in same area. (This is a prudent precaution even though it is unlikely that the virus would spread this way.)

Hopefully, this disease will never visit your garden.  If you suspect that your roses may have this disease, please contact the Extension Office at 903-455-9885 for further information.

Preventing Oak Wilt

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Preventing Oak Wilt by Byron Chitwood

There are many diseases and insects that attack Oak Trees in Texas.  .   One of the most devastating of the diseases is Oak Wilt.  Hunt County has managed to dodge the Oak Wilt problem even though it is as close as Collin County.  Oak wilt will be discussed later in this article but first it is important to recognize some of the more prevalent conditions that attack Oaks and some other trees in our area.

The prolonged drought has been an enabler for many of the diseases and insects to attack our Oak Trees.  One of the ones that have been the most devastating in our area is Hypoxylon Canker.  Hypoxylon is a wind borne fungus that attacks the trees by entering through wounds in the bark.  Hypoxylon Canker attacks the cambium layer under the bark and at the same time, white rot attacks the sap bearing wood under that layer.  Both grow and expand causing the bark to peel and fall to the ground around the base of the trunk of the infected tree.  Presently, there is no cure for this disease and trees that reach this state will eventually die.  The only safe treatment is to keep the high value trees in the urban lawn well watered.  Healthy trees have the ability to resist Hypoxylon Canker.

Oak Tree Decline is also a fungus that we do see some of in this area.  The fungus gradually stops the flow of liquids to the top branches which dieback.  This disease gradually kills the infected tree over a period of time.

Borers usually attack unhealthy and stressed trees.  They are not the cause of death of many trees but are a symptom of other problems.  High value trees can be sprayed with an insecticide that will at least kill the borers.  A proficient Arborist should be contacted if treatment is desired.

One problem that we see in this area is from Oak Twig Pruner and Oak twig girdler.  The symptom of this problem is a multitude of very small branches fall from an otherwise healthy tree.  Both insects lay eggs in a small branch.  The eggs only hatch after the branch dies.  The best suggestion for this problem is too keep all the fallen branches picked up and destroyed or put in a secure trash bag and dispose of them.

 

Oak Wilt develops from a fungus spread by the Nitidulid Beetle. They feed on the sap of Oak Trees.  Unfortunately, some of these trees they feed on are infected by Oak Wilt.   They then transport Oak Wilt fungus to otherwise healthy trees.  Since the Nitidulid Beetle is a sap feeder, the most convenient dinner table for them is a very recently trimmed tree that is oozing sap.  The oak wilt fungus can only survive in a very narrow temperature range that occurs between early spring and the hottest part of the summer.  Therefore, limit trimming oak trees to only the coldest and hottest months of the year, namely February and August.  Even then, paint the trimmed ends of branches with a pruning solution or latex paint.

One of the major ways Oak Wilt has been spread is through the purchase of firewood that comes from an area that already has Oak Wilt.  Only purchase fire wood that has been well seasoned.

If Oak wilt is a suspect in one of your trees, please contact the Texas A&M AgriLife at 903-455-9885. A specialist will contact you to assess the symptoms and advise the next steps to take.

Cool Weather Lawn Problems

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Cool Weather Lawn Problems by Charles Bohmfalk

We are now entering the fall season that brings cooler weather and humid, rainy conditions.  Lawn diseases become a bigger problem with these conditions that are more pleasant for us.  Brown patch is one of the lawn diseases that becomes a problem in our lawns during the cooler and more humid weather conditions in the fall and early winter months when night time temperatures are below 70° F and the daytime temperatures are in the 75° F to 85° F range.  Most turf grasses are susceptible, especially St. Augustine, zoysiagrass and centipede grasses.  Brown patch doesn’t normally kill the affected grass, but it can weaken the affected grass and make it more susceptible to further damage by the approaching freezing and sometimes dry winter conditions.  Brown patch is a fungal disease problem that can easily be confused with grub worm, armyworm, sod webworm, cutworm and chinch bug damage.  Proper diagnosis is necessary to treat and remedy the problem.

Brown patch has circular to irregular shaped patches of brown or yellowing grass that is less than one foot to several feet in diameter.  The outside of the circle may have a “smoke ring” appearance that is caused by the spreading fungus.  In this area, the leaves of the grass may be easily pulled from the stolens or stems.  Inside the infected area the grass may remain green that leaves a “frog-eye” appearance.  Leaf sheaths in the infected area also become rotted and water-soaked to the point that a gentle tug of the leaf blade easily separates it from the runner.  To prevent this disease from attacking your lawn, pay close attention to your watering habits, thatch accumulation, and your nutrient management program.  Fungicides that are easily obtained at your local garden center can be used for the prevention and control of brown patch.  Read the label and carefully follow the directions when using any fungicide or insecticide.

Brown areas caused by grub worms will show a browning or the appearance of a lack of water in the area.  The damage may be a small spot or cover a large area and is caused by white grub worms, the larvae of the May or June bugs.  The larvae feed one to two inches below the surface and destroy part or most of the root system of the lawn.  Damage usually appears in late July through early August.  If the damage is heavy, the sod can be easily lifted up or rolled up.  To verify that the problem is grub worm damage, dig one square foot sections to a depth of 4 inches.  Treatment with an insecticide is necessary if more than four grubs are found per square foot.

Cinch bug damage appears as irregular patches in sunny areas, usually along driveways, sidewalks and house foundations.  The grass first turns yellow and eventually dies and then turns brown.  To identify a chinch bug infestation, remove both ends of a metal can and twist it into the grass.  Fill the can with water and a little detergent.  In a few minutes, the chinch bugs will float to the surface.  They are black with white wings folded over the body.  Treat with an insecticide that has cinch bugs listed on the label.  Read the label and carefully follow the directions when using any fungicide or insecticide.

Oak Tree Diseases

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Oak Tree Diseases by Byron Chitwood

Probably the most dreaded disease problem that attacks oak trees in Texas is Oak Wilt.  Fortunately, we do not have that problem in Hunt County.  However, it is as close as Collin County to the west of us so be vigilant and take precautions to prevent this disease from attacking your oak trees.  It can attack any variety of oak trees but seems to be one that infects Live Oaks.  One of the easiest precautions that can be taken is to buy only seasoned fire wood, preferably from this immediate area.  Also, do not trim any of your oak trees except in the hottest and coldest month: August and February respectively.  The spoor that causes oak wilt is transmitted by a small beetle that feeds on the sap of trees and can smell a newly cut tree from over a mile away.  In order for the oak wilt spoor to infect a tree it must be transmitted in a fairly mild temperature range.

The disease that has been the most prevalent in this area for the last several years is Hypoxylon Canker.  This disease is transmitted by windblown spoors from an infected tree to other ones especially those in a distressed state such as we have been witnessing as a result of the extended drought.   Post oaks are the variety most affected by this disease. This area has a lot of post oaks, especially in sandy areas.  Post oaks have a relatively shallow root system which does not hold water very well.   Drought conditions dry out the topsoil very quickly and leave the trees in a very distressed and vulnerable condition.  If there is Hypoxylon canker infected trees in the area, the spoors are transmitted by the wind and can infect ones that are not already infected.

The first signs of Hypoxylon canker are peeling of bark from the infected tree.  These spoors have somehow gotten under the bark and feed on the trees vital fluids.  The canker grows under the bark creating pressure causing the bark to burst and fall off.  The tree cannot survive if the tree is “girdled” and will very quickly die.  There is no known cure for a tree in this condition.  The best way to prevent trees from contacting the disease is to keep the “high value” ones watered.  These are the ones in yards and close to homes.  If a large acreage is involved, there is not much that can be done economically to prevent the disease from occurring.

Post oaks are very sensitive to root damage.  Do not grade or fill with topsoil on the root system.  Do not park vehicles on the root system.  If a tree dies from Hypoxylo0n canker, cut it down and stack away from other trees.  Cover with a clear plastic sheet and the heat will kill the active spoors.  It can be safely burned without transmitting the disease.

There are too many tree diseases to describe them all in this article.  If you do have a tree problem, contact the Texas A&M AgriLife office at 903-455-9885 with a description of the tree problem and the variety of tree if available.  The office will alert one of the local Master Gardeners and you will be contacted with advice on what the problem is and how to handle it if there is a solution.