Ponderosa Pine Bark Beetle Control
Bud Franklin, Horticulturist
June 26, 2003
Arizona is currently experiencing an infestation of bark beetles that are contributing to the demise of hundreds of thousands of pine trees. The two beetles responsible for this attack are the Pine Engraver Beetle and the Western Pine Beetle. Although many species of pine are being attacked, the Ponderosa and the Pinyon seem to be taking the heaviest losses. These beetles are always present in nature. A healthy and vigorous tree usually has the ability to pitch out attacking beetles thus preventing colonization. The reason we are seeing the tremendous loss this year is because of the drought, which we are currently experiencing. In a normal year the pines would be metabolizing, moving water and nutrients up the xylem and carbohydrates down the phloem. Because of the lack of moisture in the root zone this process has been completely shut down or nearly so. In fact, there are those who are beginning to believe that many of the losses are caused as much by a lack of water and nutrients as by the beetle itself. However, it is true that in this state of near dormancy the plant becomes totally unable to fight off an attack.
The focus of any control program must be to return the tree to a healthy and vigorous state. Your first line of defense is to act now and try to eliminate as many points of stress as possible. This can be achieved using the following steps:
1. Watering: It is extremely important to initiate a watering program that will replenish the moisture in the feeder root zone. This is an area that encompasses twice the diameter of the drip zone to a depth of anywhere from 2 feet to 15 feet depending on the size and age of the tree as well as the soil characteristics. This watering program should replenish the moisture in this zone at least once a month throughout the entire year. There are numerous ways to accomplish this depending on the availability of water, the topography and the soil. If water is in short supply the following technique seems to accomplish this task with the least amount of water. Using a 4” diameter perforated PVC pipe 4 ft long (optimum) bury vertically at 5 ft intervals below the drip line. Fill the pipes with pea gravel. Using a hose fill the pipes with water until saturation occurs once a month. Another method is to dig a trench 4” deep and 6” wide around the drip zone and run water until saturation. The easy method is to use a lawn sprinkler under the drip zone and beyond and allow to run for 6 to 12 hours. This method is the least effective use of water because of evaporation and runoff. Drip irrigation techniques are typically not effective because of the limited application area as well as low water output unless left on for a very long duration.
2. Implants: Trunk implants should be used to address two issues: 1) nutrient deficiency and 2) insecticide placement. Because the plant is near stress induced dormancy, it is unlikely that it has the ability to uptake the adequate amount of nutrient via the root system. By using an injectable fertilizer, it is possible to bypass the stressed root system as well avoiding any problems associated with soil chemistry. I recommend Medicap MD 3/8” implants containing a complete fertilizer with an analysis of 12-4-4 with Iron, Zinc and Manganese. This application technique has been documented to last in the tree for periods of 24 to 36 months while providing all the elements necessary for vigorous plant growth.
As far as the insecticide is concerned, by injecting, it is possible to maximize control with the minimal amount of chemical, eliminate concerns for over spray or spray drift which could negatively impact wildlife, and container disposal issues. Acecap 97 is recommended because of numerous factors. First, the active ingredient is Acephate, a proven insecticide with both contact and systemic action. It has been shown to be active in pines for periods up to a year. Secondly, it is one of the safest insecticides on the market as far as the LD50. This product is non-restricted and can be used by the homeowner.
• Application Technique: When applying both Medicap MD and Acecap 97 simultaneously it is recommended that an implant is placed every 2 ½ inches to 3 inches around the circumference in a stair step fashion. See manufacturers label for additional information.
3. Sanitation: Remove all dead and dying plants. These plants are breeding grounds and will become a source of additional infestations next spring.
4. Thinning: Thin unwanted vegetation around pines. This will eliminate other plants from competing for water and nutrients.
ACT NOW! Once a tree has been colonized in all likelihood it will die. Address every issue which could be causing undue stress to the plant and make every effort to eliminate the cause. Use tree implants for fast, efficient and safe results. Remove dead plants and plant material from the immediate area. Thin area of unwanted vegetation to eliminate competition.
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