Bugs, Bugs, Bugs August 2008

This month we are seeing a plethora of caterpillars on several trees. Most are not that important except they cause concern for the homeowners, although a couple look very menacing.

1. Walnut caterpillar – This caterpillar can be found on walnut, butternut, pecan and hickory trees. The larvae feed in clusters and initially skeletonize the foliage, then they consume all but the main rib or vein. They are very mobile and will be on one branch one day and on a different part of the tree the next. The caterpillars are reddish-purple in color with white stripes and long gray hairs on the body. At maturity, the larva is black with the long gray or white hairs. The larvae periodically move to the trunks and branches where they will molt. The mature larvae fall or migrate to the ground and dig cells in the soil for pupation. They overwinter as pupa and emerge in late spring. There are usually two generations each year. The easiest way to control them is to shake the branch vigorously to knock them off, then step on them. Figure 1.
2. Yellow-neck caterpillar – A common species in the South, this caterpillar is noted by the bright orange-yellow shield behind the head. The caterpillar is yellowish-brown with white stripes and long gray or white hairs. Like the walnut caterpillar, they feed in clusters on a wide variety of plant materials, including deciduous fruit, nut and shade trees. The moths emerge from overwinter pupal cells in the ground in June and July and begin laying eggs in cluster of 25 to 100 on the foliage. Larval stages remain for four to six weeks before pupation. There are two generations per season. There are several natural enemies such as birds, parasitic flies and predatory insects. Infestations may be shaken from the trees and stepped on for management. Figure 2.
3. Yellow/orange-striped oak worm – Pupa overwinters in the soil, and adults emerge in late spring or early summer. The larvae are black with several orange-yellow stripes the length of the body. Two elongated, antenna-like structures protrude from the second thoracic section, and several rows of black spines run down the length of the body but do not sting. Occurs from Minnesota east and south to Texas. One generation occurs in late July to October. Hosts are primarily oaks, but they can be found on chestnut, birch, hazel, hickory and maple. Young larvae tend to skeletonize the foliage, and older larvae eat all but the mid rib. They feed in clusters until late instars and then tend to move about individually. At maturity they move down the trees and may travel considerable distances before finding a suitable site to burrow into the soil to pupate. While in clusters they may be shaken from the trees and stepped on. They are occasionally parasitized by icheumonid wasp. I have only had one instance where they required spraying because of the density of the population. Figure 3.
4. Red-striped oak worm/spiny oak worm – Coloration is very variable from orange to yellow-brown to black with many small white spots on derm. Characteristics on the body are the same as the orange-striped oak worm. There are two generations in Louisiana each year, with caterpillars observed from June through October. Egg clusters are generally smaller than other oak worms, but the feeding, pupation and overwintering characters are about the same. Figure 4.
5. Pink-striped oak worm - Pretty pink-and-black-striped caterpillar with numerous small white spots on the body. Spines on body may be smaller than the other oak worms. Found from Nova Scotia to Louisiana. Has one generation in the North but two to three in the South. Eggs may be laid several hundred in a cluster. The same feeding habit as previous caterpillars. Figure 5.
6. Green-striped maple worm/ rosy maple moth – This pale green larva with blue-green to white stripes is found primarily on maple but may also be found on oak or box elder. The body characteristics, overwintering habits and feeding characteristics are the same as the previous caterpillars. It has two to three generations a year in the South with mature caterpillars found from June through October. Figure 4.
7. Redheaded azalea caterpillar – A serious defoliator of azaleas, this caterpillar is limited to the southeastern United States – but occasionally as far north as Maryland. Eggs are laid in clusters of 80 to 100. The larvae are gregarious and feed by skeletonizing the leaves, but at maturity they devour the entire leaf. Small plants can be defoliated over night from just a few caterpillars. The larvae are reddish-purple and hairy when small, as they grow they change to black with yellowish-white stripes and black with a broken white strip at maturity. They have a bright red head, belly, legs and back end. The mature larvae migrate to the ground and pupate in cells in leaf litter or the soil. There is one generation a year that occurs in late August through October. Population may be shaken from plants and stepped on or sprayed with a pyrethroid, Orthene, Spinosad or a Bt. Figure 7.
8. Hickory horned devil – This large, fierce-looking worm is harmless. Although up to 7 inches long with several orange, black-tipped horns 2 inches long on the thorax and a series of black short spines on the body, this caterpillar does not sting or cause any pain at all. The horns are to fight off birds that try to make a meal of it much like cows fight off coyotes. When the bird wins, its biggest problem becomes the carcass because the bird will probably not be able to fly. These larger, lime-green worms feed on a variety of tree foliage, particularly pecan, hickory and walnut. They are occasionally found under trees or on the foliage in late summer or early fall. No treatments are needed as it is one of the giant silk moths and will cause no damage except to frighten people who have not seen them before. Figure 8.
9. Chinch bugs – This grass-feeding pest can cause serious damage during hot, dry conditions. The piercing, sucking mouthparts puncture the rhizoids of the grass and cause a gradual yellowing and death of the grass in patches. The feeding disrupts the water flow in the plants, causing damage that resembles drought but does not respond to watering. The immature forms are black with a light band on a pinkish abdomen. They gradually develop wings and at maturity are gray-black and 1/6 inch long with white wings with a black spot in the middle. The damage is sometimes confused with brown patch, which occurs during cool wet seasons. One can check for chinch bugs by cutting both ends out of a large can, sinking it in the ground, filling it half full with water and checking the insect that float out of the grass. Or you can drench a square-foot area with a solution of one gallon of water and 1 tablespoon of lemon soap. This will flush the insect to the surface to see if it is there. Figure 9.
10. Fall armyworm/parasites – We are still seeing fall armyworms in turf and pastures. However, at this time of year we are getting some assistance from some parasitic flies that are parasitizing the caterpillars. Where the armyworm population has any number of these larva with the parasite eggs attached (as shown in the figure), there is no need to treat because that population will stop feeding shortly and the parasites will complete development. This will also occur in the spring in pastures and grass field and occasionally lawns. If these populations are sprayed, we lose the parasite population and allow the next generation to go on with reduced pressure from parasites. Figure 10.

Until next month,

Dale

Figure 1. Walnut caterpillar and adult. Figure 2. Yellow-necked caterpillar and adult. Figure 3. Orange/yellow striped oak worm Figure 4. Rosy or spiny oak worm and adult. Figure 5. Pink-striped oak worm and adult.

Figure 6. Green-striped maple worm and adult. Figure 7. Red-headed azalea caterpillar and adult. Figure 8. Hickory horned devil and adult. Figure 9. Chinch bug family -- several stages. Figure 10. Paratisized armyworm.