The Top 4 problems impairing trees and shrubs in Southern Utah

Conifer Suffering from Bore Beetles | Photo by Joyce Kuzmanic for St. George News

SOUTHERN UTAH – With spring well in play, there is no time like the present to make assessment of the health and needs of trees and shrubs in our yards.

Mark Hodges, owner of Arbor Tech, who sits on the city of St. George’s Shade Tree and Beautification Board and the Utah Community Forestry Council, among other roles, identifies his “Top Four” list of problems afflicting and sometimes killing trees and shrubs, adding his prevention and treatment suggestions.

These are: 1) overwatering; 2) root fungus; 3) bore beetles; and 4) abuse of chemicals.


Hodges said 60-70 percent of the problems he addresses stem from overwatering. Nutrient deficiencies result from overwatering, the most common indicator being yellowing leaves.

“When you overwater it binds up iron in the soil and the plant struggles, its leaves yellow and brown because the leaves are losing pigment, which causes them to burn in the sun.

“These plants are acclimated to the desert climate and are used to building root systems to find water.

“Look at what survives in the yards of the foreclosed houses in our area despite the water being shut off. Think about the pioneers whose main method of watering was through gutters, flood irrigating similar to rice paddies!”

Hodges recommends a deep soak once or twice a week in most cases rather than a 10-minute daily watering, based upon consistent temperatures.  Specifically:

  • Below 60 degrees, no watering is required. Plants do not move water unless they get over 60 degrees.
  • Consistent temperatures in the 60s and 70s  justify once-a-week watering.
  • Consistent temperatures in the 80s and 90s necessitate twice-weekly deeper watering.
  • Temperatures rising higher demand closer attention. Hodges suggests you respond to your plants as you would cut flowers: If you have wilting cut flowers, you put them in water and they perk up. The same goes for wilting trees and shrubs in yards.

“Dig down 6 inches into the dirt, see whether it is moist or dry,” Hodges said. “If it is moist, it is premature to water. Trees and shrubs need a time of drying out to get oxygen to the root systems; the same goes with grass – you can train your grass to send roots down deeper.”

Root Fungus

Root fungus attacks the root system and rots away the roots. Indicators of root fungus are also yellowing leaves as well as dropping leaves in the summertime. These result from the tree not being able to draw the nourishment it needs because the rotting root system can’t keep up, Hodges said. Overwatering does not cause but will make conditions ripe for root fungus.

Bore Beetles 

There are about 10 different varieties of bore beetles in the St. George area, but they all do the same thing, Hodges said. They eat the inside of the tree.

One obvious indicator of a bore beetle infestation is dying spires and branches of a conifer species (all kinds of cedars, spruces, firs and junipers).

Hodges likens the problem to a sick gnu on the plains of Africa: “Where there’s a sick gnu, the lions attack,” he said. The bores and beetles are a secondary problem to a tree first becoming malnourished or stressed.

“Bore beetles are like termites, they eat the wood on the inside and are very detrimental. Once they are there and start chewing on a stressed tree, they send out pheromones which attract even more of their kind.”

Treatments for infestations may include an external foliar spray and systemic treatments, combined with trimming off the affected areas to the extent possible. Similarly, preventions include proper watering and systemically offered nutrients.

Abuse of Chemicals 

The two most abused chemicals are the 2 4-D broad leaf herbicide and soil sterilants, Hodges said. Both usually occur through owner and landscaper mistakes.

Two 4-D includes weed and feed, bush begone, dandelion killers and the like. These are popular products which kill dandelions, spurge and weeds in the lawn without killing the grass.

“But the problem is our trees and shrubs are broad leaf also, like the weeds we seek to kill,” Hodges said. “The 2 4-D products often reach our trees and shrubs by overspray and by volatilization (evaporation) in high heat. When either happens, the chemical goes right into the stomata of the leaves and kills the plants.

“Soil sterilant is an even more powerful chemical that kills weeds for 10 years. It should never be used in an urban environment.”

Soil sterilants appeal to people’s frustrations with fighting weeds, he said, because they promise and deliver death to weeds for 10 years.

“The problem is, once it is introduced into the soil there is nothing you can do to remove it. Tree root systems will extend three-five times the length of the limbs, thereby reaching the ‘sterilized’ (contaminated) soil.”

As a result of both abuses of chemicals, Hodges said, neighbors are often guilty of harming and killing each other’s plants, sometimes affecting entire neighborhoods.

“I am called out on about 10 cases each year to assess cases of someone stressing or killing their neighbors’ trees.”

It is not uncommon for these to give rise to claims and lawsuits, not to mention general hostility between neighbors.

Hodges recommends a certified arborist or nursery professional familiar with these problems be consulted when they arise.  His own company, Arbor Tech in St. George, offers such service and can be contacted at 435-632-0972. He suggests Star Nursery and Backyard Garden Nursery as knowledgeable and able to address and provide products for these issues. Both of these also put on periodic educational seminars which Hodges said he finds worthwhile.

Email: [email protected]

Twitter: @STGnews

Copyright St. George News, LLC, 2011, all rights reserved.


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1 Comment

  • Tyler January 4, 2014 at 4:24 pm

    Excellent article. Get educated, people and quit wasting water in the desert!!

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