Fall armyworms and webworms, cicada killers arrive early this year

In the plant and insect world, this has been an unusual year.

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First of all, most of our flowering plants were three to four weeks behind normal. Now, it seems many of the late-season insects are showing up early.

Three species showing up earlier than normal are fall armyworms, fall webworms and cicada killers.

Fall armyworms (Spodoptera frugiperda ) are a tropical species that survives in warmer climates along the Gulf Coast or South Florida. They infest plants in South Florida beginning in February and move north as the weather warms. They tend to reach our area about the last week of August or first week of September, and they can last until frost.

In this area, fall armyworms are pests of bermuda grass, millets and fall vegetables. Calls have started coming in because of damage to hay fields and pastures, and I expect to start receiving calls that armyworms are attacking home lawns.

Armyworms get their name from the large number of caterpillars that can be in an area. The adult stage is a moth. The female moth lays about 400 eggs in a mass. These eggs are laid at night on plants, flagpoles, stones or anything that is close to the food source. When the caterpillars are small, they chew on the bottom of the leaf and usually don't consume the whole leaf. As the caterpillar grows, it will consume the entire leaf or plant.

When the food source is used up, the entire population of caterpillars will move together to a new food source. I have seen a lawn that measures 2,000 square feet have tens of thousands of armyworms. This many caterpillars can eat a lawn this size during the night.

Armyworms can be treated with Bacillus thuringiensis (Bt, Dipel), carbaryl (Sevin) or various pyrethroids found in garden centers. Watch for them until frost. This year, there could be up to four generations.

Fall webworms are here a few weeks early. They can have up to four generations in a year, with most of the activity occurring in late summer and early fall. The larvae or caterpillars are hairy with distinct paired spots on each segment of the back. They can be variable in color, but the primary color in our area will be whitish-yellow to pale green with white hairs. The caterpillar will be about an inch long when mature, and it will twitch and jump about when disturbed. This is done to deter potential predators. The caterpillars will turn into a moth that is satiny white with a wingspan of 11/2 inches.

The moth lays egg masses on the underside of leaves. They prefer pecan and hickory trees. When the eggs hatch, the young larvae feed together.

They will skeletonize the leaf and then start to form their web on the end of limbs. The web is made of silk, and into this is incorporated leaves and branches into the web. The young larvae do all of their feeding inside of the tent. When they run out of food, they make the tent larger.

The best way to control fall webworms is to remove the web from the tree. A pole pruner can be used to reach them and remove the portion of the limb that has the web on it. Because fall webworms don't feed outside of the web, removing the web will remove all of the caterpillars. There are insecticides that can be used, but they can be hard to apply because most of the webs are high in trees. Burning the webs is not recommended; it will damage the tree and is a fire hazard.

The third insect showing up early is the cicada killer. This insect doesn't harm plants or animals. These wasps are predators of cicadas.

This intimidating insect can measure 11/2 to 2 inches in length and is black or brown with colorful yellow markings on the abdomen and a quarter-inch stinger.

Cicada killers typically fly 16 to 20 inches above the ground. As frightening as these insects might appear, they typically are not aggressive and are actually considered to be beneficial. These wasps will not sting unless cornered or accidentally touched or stepped on. In this case, a cicada killer's sting can be very painful.

These insects pose a real threat where people, especially children, congregate or play. If there is a need to control, pesticides that are used to control wasp and bees can be spread on the soil surface. This will kill the wasp when they come in contact with the pesticide.

Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at cphillipshort@comcast.net.