By Jan Wrede
Guest Columnist

The spring caterpillars are here again—out there raining down from the trees, brushing across my face and getting tangled in my hair. If you have an infestation in your yard, you know what I am talking about.

Spring is the messy time of year to live in the shade of live oak trees. They drop their old leaves, shed millions of wormy blossoms and often are invaded by thousands of caterpillars.

There is nothing we can do but clean up after the leaves and blossoms, but what about the annual caterpillar invasion? How much damage do the caterpillars do to our trees? What is the best way to control them? Do they have any useful role in nature?

Our trees may be invaded by several species of caterpillars that become small moths. The good news is that all are a nuisance but none are a serious threat to the health of our trees.

And more good news is that the caterpillar’s life cycle is brief.

When repelling down on their invisible threads, they are finished eating and on their way to the ground where they will disappear until next year.

And even better news is that the caterpillars are a huge source of food for hungry songbirds. These spring outbreaks are at the perfect time for nesting birds. Baby birds get fat fast on juicy caterpillars! The caterpillars also are easy eating for inexperienced fledglings at the most vulnerable phase of their lives.

Even with a serious infestation, the caterpillars do not seriously harm our trees. When the caterpillars are most pesky, this means that they will soon be gone. Songbirds thrive on caterpillars. So, perhaps we just need to be patient and let the birds eat their fill.

Or if you must do something, you have two choices that are recommended by Texas entomologists and foresters. When the young caterpillars are still feeding in the trees, you can spray the organic control B.t. (Bacillus thuringiensis Kurstaki Strain).

Caterpillars consider this product food and readily consume it.

The disadvantage here is that this treatment is not effective when the caterpillars are near their full size and raining down into your yard—because they are finished eating. Both the caterpillar damage and nuisance are nearly over and this spray is a waste of time and money.

Another product is Spinosad that does not have to be ingested. It works through direct contact with the worms and can be effective even after they are plentiful. Remember, however, if you use this, you will be killing many other insects on the sprayed trees.