Many species of aphids or plant lice occur on ornamental trees and shrubs. Certain species feed on foliage, others on twigs and branches, flowers or fruit, and some on roots. Aphids live on several distinct hosts, spending part of their seasonal development on one host and the remainder on another. They feed on both coniferous and deciduous plants. Effective control of aphids has been a problem to homeowners and landscape managers for years. Some of the more common aphids include the green peach aphid, melon aphid, tuliptree aphid, giant bark aphid, white pine aphid, and rose aphid.
Description: Aphids constitute a large group of small, soft-bodied insects. They may measure up to six mm in total length. Aphids have piercing-sucking mouthparts that enable them to remove plant fluids from a host. Aphids generally can be recognized by their pear-like shape, a pair of cornicles (tube-like processes) at the posterior end of their body, and fairly long antennae (Fig. 1). The cornicles secrete a defensive fluid which warns aphids of predators and other enemies. Aphids vary in color from green, yellow, red, purple, brown, or black.
Damage: Aphids are common, persistent, and sometimes key pests of ornamental plants. Most aphids cause damage to host plants by the removal of plant fluid, by the toxic action of their salivary secretions injected during feeding, and by serving as vectors of plant diseases that are harmful to key plants. Feeding by aphids can stunt plant growth, deform leaves and fruit, or cause galls on leaves, stems, and even roots. Many aphids also excrete a sticky, sugar-containing substance from their anus known as “honeydew.” This material will drop onto the leaves, twigs, and fruit of a plant. A black, sooty mold soon begins to grow on this sugar-rich substrate. This mold decreases the aesthetic appearance of the plant, but when abundant, will also reduce the food-making process of a plant known as photosynthesis.
Chinch Bugs (Blissus leucopterus hirtus)
Hairy chinch bugs can be frequent pests of home lawns in Pennsylvania. They are often associated with open, sunny areas and may be as numerous as 150 to 200 insects per square foot. Chinch bug populations frequently go unnoticed because of their small size and coloration, which blends in with turfgrass and thatch. Chinch bug damage may be masked during periods of drought.
Description: An adult hairy chinch bug is about 1/6 inch long, has a gray-black body with fine hairs, white wings, and reddish legs. The outer margin of each forewing has a small, black, triangular spot. The wings of the adult are folded flat over their backs. Some populations of chinch bugs have adults with short wings. Young nymphs are about half the size of a pinhead, and start out as being brick-red with a transverse white band across the back. As the young mature, they turn gray and then black with wing pads developing as they mature into adults.
Damage: Hairy chinch bugs prefer feeding on red fescues, perennial ryegrass, bentgrass, and Kentucky bluegrass. Chinch bug infestations frequently occur in turfgrass with thick thatch that is exposed to full sunlight during periods of hot, dry weather. Chinch bug damage is often less noticeable during the spring and early summer. Damage frequently appears from early July through late August when the insects are actively feeding. Chinch bug nymphs and adults cause significant feeding damage by removing plant fluids and by injecting a toxin that causes the grass to yellow, turn reddish brown, and eventually die. Chinch bug damaged areas often coalesce into large patches of dead, brown grass.
The eastern tent caterpillar has been observed in the United States since 1646. Outbreaks frequently occur at eight to ten year intervals. The presence of this pest in the spring is usually recognized by their conspicuous nests or tents constructed in the forks and crotches of a tree. Before gypsy moth outbreaks in the 1970s, some experts considered this pest to be a significant defoliator of deciduous shade trees in the northeastern United States.
Description: The egg mass of this species encircles small twigs and appears to be varnished. The egg mass may be nineteen millimeters. Small larvae spin fine strands of silk wherever they crawl. As the larvae grow, so does the size of the tent. Fully grown larvae are about two inches long, generally black with a white stripe down the middle of the back. Mature caterpillars will leave the host tree to search for a suitable place to spin their pale yellowish cocoons. During late June and July the reddish-brown adult moths with two oblique, white bands on the forewing emerge from their cocoons. After mating, the female deposits eggs in a mass around small twigs on a host plant.
Damage: The preferred hosts of this pest are cherry, crabapple, and apple. The eastern tent caterpillar occasionally attacks other deciduous ornamental shrubs, shade, and forest trees. The silky tents spun by the caterpillars make landscape trees unsightly, and the caterpillars are annoying when searching for food or a suitable place to spin their cocoons.
The caterpillars do not feed within their webs, but congregate there during the night and rainy weather. When caterpillars are abundant, they frequently eat all the leaves on a tree which weakens it, but seldom kills it. The foliage on the host tree may be stripped from all the twigs within a distance of three feet from the nest(s).
Japanese beetles and northern masked chafer grubs are the predominant damaging white grub species associated with home lawns. Several other white grub species including Asiatic garden beetle, European chafer, green June beetle, May and June beetles, and Oriental beetle are occasionally observed in home lawns and may cause significant damage.
Description: Grubs are dirty white, soft bodied, and robust with a brown head and six well-developed legs, with exception of green June beetle grubs, which do not have well-developed legs. When the turf is lifted to expose the grubs, they usually will be lying on their sides in a C-shaped position (Fig. 2). The size of a white grub varies with the species and its age. Full-grown third-instar Japanese beetles and northern masked chafer grubs average slightly over one inch in length. White grub species can be distinguished by examining the grub’s raster pattern. The raster is a grouping of definitely arranged hairs, spines, and bare spaces on the underside of the last abdominal segment in front of the anus.
General Life History: With the exception of the common May or June beetle, which has a three-year life cycle, the life history of the beetles mentioned above is completed in 12 months (Fig. 5). The adult beetle lays its eggs in the ground during the summer. As soon as the grubs hatch, they start feeding on the roots until cold weather drives them two to eight inches deeper into the soil where they overwinter. When warm weather arrives in the spring, the grubs move up from the lower soil regions and resume feeding near the surface until they become mature and pupate (Fig. 6) from May through early-June.
Damage: Heavy white grub infestations can destroy grass roots, causing the affected area to become spongy, which allows the sod to be rolled back like a piece of carpet. Evidence of grub damage, including patches of dead or dying turf, are visible during spring (April and May) and late summer and fall (September and October) A good indication of a grub infestation is the presence of skunks, crows, or moles feeding on turf. However, remember that moles also feed on earthworms or insects living on shallow tree roots.
Sod Webworm (Toumeyella liriodendra (Gmelin)
Description: Adult moths at rest often face downward on a grass stem and wrap their wings around their abdomen. Sod webworm adults have siphoning (straw-like) mouthparts, are dull-colored moths with a wingspan of ¾ to 1 inch, and their front wings frequently are whitish, dull gray to tan-brown, often with longitudinal stripes and other markings. The adult is easily recognized by a pair of projections arising from the front of the head, resembling a snout. The mature larva is about ¾ inch long, brown to green with darker spots on the surface of its body, and has a long setae rising from the dark spots and mottled brown head capsule.
Damage: Sod webworm larval damage often is observed as brown patches up to the size of a baseball in the lawn. In some instances, the brown patches are punctured with pencil-sized holes a result of birds searching for the webworm burrows. Feeding damage from sod webworm larvae frequently goes unnoticed during periods of drought. The most severe damage usually occurs in July and August. Larvae chew off leaves and stems just above the crown. As webworm larvae continue to grow and feed, the injured areas enlarge and coalesce into big, brown patches.
Spruce Spider Mite (Oligonychus ununguis Jacobi)
The spruce spider mite is considered one of the most destructive spider mites in the United States. It injures the foliage of spruce, arborvitae, juniper, hemlock, pine, Douglas-fir, and occasionally other conifers. Dwarf Alberta spruce, Picea glauca 'Conica', is one of this pest's preferred host plants.
Description: After hatching, the young, pale green mites called larvae resemble adults except they are smaller and have only three pairs of legs. As the mites mature, they shed their skins three times before becoming adults. Adults and nymphs have four pairs of legs and are dark green to nearly black with the body surface clothed with salmon pink-colored spines. The adult's legs are also salmon pink.
Damage: This species damages host plants by sucking plant fluid from needles as they feed. Infested trees at first have a speckled, yellowish appearance, and lack rich green color. After prolonged feeding, needles turn rusty colored and may drop prematurely. Mites usually attack older needles located in the lower and inner parts of the plant. Damage may spread as the season progresses. This species also produces silken webs on the needles.