J. Steele of New Boston, TX asks,

We have two pecan trees in back yard. caterpillows, cut worms or something is making nests and harming trees. IS THERE ANY WAY TO GET RID OF THEM WITHOUT USING DANGEROUS CHEM.?

J - I’ll start off by suggesting you bring out an arborist or horticulturist in your area to get a correct diagnosis. Many trees and shrubs can withstand infestations for a few years, but they sure look (and feel) awful when they go under attack. My guess (and again, only a guess here folks) is that you may have a tent caterpillar infestation. If indeed you do have tent caterpillars there are a few options out there.

It’s been about 3 years in Seattle since we’ve had big infestations of tent caterpillars. For about 7 year cycle we had annual infestations, and they were horrible. I was pruning trees and burning branches. I was trying to apply BT to knock them out.  I was scratching egg masses off branches. Still, they showed up and assulted a wide array of trees in my area — oaks, cherries, apples, pears, birch, peach and more. Then, they were gone. I imagine after a few years they’ll be back. Such is their cycle.

First, its important to understand the lifecycle of a tent caterpillar. These caterpillars were laid as eggs last year on the stem of the tree. The egg masses are tiny and often very difficult to see on the branches of a tree. In the spring, when the tree has leafed out, the egg masses mature, releasing caterpillars that travel into the tree gorging themselves on tasty new-growth leaves and buds. Then, they begin forming huge tent nests where they go into the next phase from which their flying and breeding moth form emerges.

So, by knowing how they function you can then work on getting rid of them:

•  All the time: Reduce your overall use of pesticides so you encourage a strong population of positive natural enemies like parasitic wasps and flies.
• Fall/Winter/Early Spring: Inspect trees for tiny raised areas with lots of dots. If you find them, scratch them off the bark and destroy. These are egg masses.
• Spring/early Summer:
  • Continue to inspect tree for the tiny raised areas which will start swelling and releasing caterpillars.
  • If you see caterpillars begin destroying by hand. Keep an eye out early for them. They are best eradicated BEFORE you see the tents. Ways to eradicate caterpillars include:
    • BT applications: BT is a a biological pesticide that essentially causes the insides of the caterpillar to explode. It will only affect caterpillars. The caterpillar must eat the BT in order for it to work. So, it must be applied while the caterpillars are actively feeding. Applying it when they are in their nests, in their egg forms or as adults won’t help a bit.
    • Cutting out nests: When you can reach the nests, cutting out smaller branches and burning them can eradicate large populations. They can also be placed in large, sealed plastic bags to suffocate them.

 More great information on Tent caterpillars is available at the WSU website in this article.

Again, please get proper identification of your pest locally before applying any type of chemical control.  And, good luck.