Cicada killer wasps emerging in Central Texas

Over the past week I've been getting questions on large wasps that people are seeing emerging from the ground.  They want to know what they are and be reassured that they are not the Asian giant hornet.  These wasps are known as cicada killers and are aptly named.  Cicada killers are large wasps, reaching around 1.5 inches.  They have a rusty colored head and thorax with a black and yellow patterned abdomen.  The wings are also rusty in color, but transparent.

Cicada killer wasps are solitary, but multiple wasps may be seen in the same area at times.  Males are known for aggressively defending their territory and patrolling burrows created underground. While males dive bomb someone who walks into their territory, they are incapable of stinging.  Female cicada killers are capable of stinging, but generally reserve their stinger for paralyzing prey and tend to only sting in defense.

Adult wasps feed on nectar and tree sap while immatures feed on cicadas.  Adult female wasps locate a cicada, sting it causing the cicada to become paralyzed and then carry it back to the tunnel created in the ground.  She drags the cicada into the tunnel and to a nesting chamber.  Each chamber is provisioned with 1-2 cicadas before the female lays an egg on the leg of the cicada and seals up the chamber.  Once the egg hatches, the wasp larva eats the provided cicadas, overwintering in the ground as a mature larva, and pupating the following year to emerge again when cicadas are available.

Tunnels are about a foot deep and about 2 feet long with 3-4 chambers off to the sides for provision cicadas for larvae.

These wasps are considered to be beneficial, so no control is recommended.  If you feel that you need to manage them, you can:
1. Use clear plastic tarp over the tunnel area to solarize
2. Sprinkle and insecticidal dust around the tunnel opening and tamp it down with your foot

Webworms and a garden visitor

Webworm caterpillar.

This week-- tomorrow (May 3, 2014)- is the Travis County Inside Austin Gardens Tour.  The AgriLife Extension Demonstration garden is on the tour so our Master Gardener group has been working diligently to get things in top condition (and the garden looks great!).  A group was here on Tuesday and they asked me to come out into the garden to give a quick bug talk.  After we went on a field trip across the street to see a harvester ant colony and a leaf cutting ant colony I headed back to my desk.  Fortunately, a volunteer came in and asked me back outside to see what they found.

Webworm webbing.

In one of the trees, they had discovered webworms (see below for more information on webworms).  Not only were there webworms, but there was a Texas Spiny lizard sitting on top of one of the webs eating the caterpillars.  It was so incredibly cute!

The lizard after its meal.

Webworms are caterpillars that defoliate trees and cause large, unsightly webs on the tips of tree branches.  There are 2-4 generations of webworms that occur each year.  The first generation appears now and the last generation occurs in late fall.  The last generation tends to be the most damaging.

Webworm larvae, or caterpillars, are about an inch long when fully grown.  They are pale green to yellow with tufts of long hairs projecting from their body.  Most people notice webbing that they create on branches.  Webworms feed with in the webbing and use it as protection from predators.  When the caterpillars need new foliage to feed on, hey expand the web.

To manage webworms, try the following:

• prune eggs masses off before the caterpillars emerge (egg masses are on the underside of leaves and are covered with hairs from the adult moth)
• prune out small webs when they begin to form in the spring
• knock webs out of the tree with a stick or a high pressure jet of water; you can also open the webs with a stick or water to allow predators into the web
• look for products with active ingredients such as Bacillus thuringiensis var. kurstaki, spinosad, azadirachtin
• even when using a pesticide, you first must open the web to get the pesticide to where the caterpillars are located

Mantids...predators of the garden

Since I covered a "creepy" bug last week, I decided to go with one that everyone generally likes to have around.

Mantids are easily recognized by their elongated thorax and specialized, raptorial front legs that are use to capture prey. They also have large compound eyes and a neck that can swivel 180 degrees. Mantids are generalist predators that will capture and eat a wide variety of small prey. They really don't differentiate between "good" and "bad" bugs, so they are best to conserve when you see them in the garden, but augment the population as they are cannibalistic and will also often bee seen eating honey bees.

After mating, females lay eggs in a frothy egg case on twigs, vines or other locations. The frothy egg case eventually hardens which will help protect the eggs throughout the winter. In the spring, small mantids (nymphs) will emerge from the egg case. It's actually rather interesting to watch as the first mantid out gets a meal delivered to them when the next nymph comes out of the egg case.

If you have kids who like bugs, or are interested yourself, you can either collect an egg case that you find or buy one from the store to watch the little guys and gals come out. If it's warm enough outside, you can release them into the backyard to have a go at it. If it's too cold outside for them to survive, you can keep them in a 10 gallon fish tank and feed them insects (pinhead crickets work great while they're small). Remember, they are cannibalistic, so don't forget to feed them!