Twig Girdler Insects

Limbs on Ground Under Tree May Be Due to Twig Girdler Insect

Tom Ingram: Ask a Master Gardener

Sunday, October 14, 2018

Q: I have been finding the tips of branches underneath my trees that look like they have been chewed off. What is causing this? DK

A: The culprit is likely an insect called a twig girdler. Adults are long-horned beetles ranging from 1/2 to 5/8 inches in length. They are grayish brown with antennae typically at least as long as the body. The larvae are whitish, cylindrical, legless grubs that grow to about 3/4 inch in length.

Twig girdlers typically prefer pecan, hickory, persimmon and elm. But, they will also enjoy oaks, honey locust, hackberry, poplar, dogwood, and various fruit trees.

This time of year it is not unusual to see these chewed off branches on the ground around trees the twig girdlers call home. Preferred branches tend to be 1/4 to 1/2 an inch in diameter.

Adult twig girdlers emerge from late August to early October and begin to feed on the tender bark found near the branch ends. While feeding they find a mate and the female deposits her eggs underneath the bark.

There are typically three to eight eggs deposited in each twig, but they may contain up to 40 eggs.

The females live around six to 10 weeks and repeat this process several times laying up to 200 eggs that begin to hatch in about three weeks.

Eggs cannot survive in a living twig, so the girdler chews almost all the way through the branch causing the branch to die. It then typically falls to the ground due to its weight or from the wind.

After hatching, the larvae overwinter in the dead twig, feeding on the woody portion of the branch.

After a 12- to 14-day pupation period during August and September the following year, the adult chews a hole in the bark to escape and the process begins again.

It is not uncommon to see the ground almost covered with twigs in heavily infested trees. Young trees can take on a deformed appearance over the years due to a twig girdler infestation. This girdling not only affects the beauty of the tree but can also reduce yields in fruiting trees.

If you are finding these chewed off branches under your trees, your best strategy is to pick up those twigs and throw them away. This removes the insect from your yard and prevents the larvae from maturing and doing damage again next year.

Garden tips

• Plant container-grown trees and shrubs this month. Fall is generally the best time to plant. At this time the plants have no energy drain to produce leaves and can concentrate on growing a root system until the soil gets cool in winter. They are better prepared for spring growth if planted in the previous fall.

• Check and treat houseplants for insect pests before bringing inside. Look at the roots and re-pot those, which are root bound. Irrigate the soil thoroughly before bringing inside.

• There is still time to plant radishes and mustard in the fall garden.