How can you control pine beetles in a small grove of trees?
Edgecombe County North Carolina
Often the first indication you have of pine beetles is a dead tree. Sometimes you catch the tree as it turns an off green color. In either case, there is nothing you can do about that particular tree. Generally, the pine beetles have already left. There is no rush to remove or destroy this tree.
On some trees, you may notice a small popcorn size resin coming out of the tree. If you catch this first thing you may be able to spray and kill the beetles. More than likely the beetles have already been successful in killing the tree. Even if you control them one time they will be back again and again over the next few years. Neither pine trees nor anything else lives forever. A better control measure may be to remove that tree and spray adjacent trees.
Most of the beetles we see are either the Ips beetle or the Southern Pine beetle. You can tell which one by the shape of the tunnels under the bark. Identifying exactly which one is not important for the homeowner since control measures are the same. Occasionally, you can take the bark off a dying tree and find some dead beetles. Homeowners are frequently surprised by the small size of this insect. It does its damage because it cuts across the layer where new cells are formed.
There is another insect called the turpentine beetle that also jumps on pine trees. When this beetle attacks it will leave a huge area of resin seeping out of the tree. It will be down near the bottom of the tree. This beetle will take 4 or 5 years to kill the tree. It lives straight underneath the sap so you can kill it by hitting the resin with a hammer. Don't get too wild or you will create additional injury.
The only real method of control for these insects is to keep the pines trees as healthy as possible. There are two major ways to do this. The first thing to keep in mind is to avoid injury. Grading, filling or compacting the soil around the roots all injures the tree. The second thing to consider is looking at competition. As the trees get bigger and compete for nutrients, sunlight, and water, they don't have the ability to walk to a better environment. If you have several pines you can select some and remove the others. This will let the remaining trees get more nutrients, water, and sunlight. This will keep them healthier and they will live longer. One way to tell if the pines are too close is by the percentage of green limbs on the tree. In a forest situation, the rule of thumb is to thin by the time the pines have shaded 70% of their height.
Actually, the foresters use a mathematical formula and angular measurements. If you hear about a technique called penny thinning, this is also an angular measurement. This states if you hold a penny at arms length, turn in a complete circle and measure 13 pine trees larger than the penny, some should be removed. This rule of thumb is not an official recommendation. I would suggest getting advice for thinning from your county forest ranger.