Aphids are small, soft-bodied insects with long, slender mouth parts with which they pierce stems, leaves, and other tender plant parts to suck out plant fluids. Almost every plant has one or more aphid species, which occasionally feed on it. Many aphid species are difficult to distinguish from one another; however, identification to species is not necessary to control aphids in most situations. Aphids may be green, yellow, brown, red or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface. All are small, pear-shaped insects with long legs and antennae. Adult aphids are generally wingless, but most species also occur in winged forms, especially when populations are high or during spring and fall. The ability to produce winged individuals provides the pest with a way to disperse to other plants when the food source gets scarce. Left untreated, Aphids can cause serious damage to ornamental plants.
Bagworms disfigure evergreen trees and shrubs by feeding on leaves and needles and girdling twigs. As worm-like larvae they spin silken bags around themselves, to which they attach pieces of the leaves they are eating. They carry this bag with them as they feed. A fully developed bag is about two inches long. These tough, spindle-shaped bags hang from the branches of infested trees like holiday ornaments, so they are easy to spot. Bagworms are the larvae of moths. Full-grown, these worms measure 1 to 1 1/4 inches. Their bodies are brown with that portion inside the bag lighter than the rest. Adult male moths have black wings, but the females are wingless. The females lay their eggs in fall, and the eggs hatch the following May or June. As the young worms begin to feed, they start doing their damage to tree and shrub foliage. They will continue eating for several months, maybe as late as August in the North. Proper insecticide use will effectively control their damage.
Emerald Ash Borers
Emerald Ash Borer (EAB) – Emerald Ash Borers are exotic beetles that have been wreaking havoc in the Midwest region since 2002, primarily in Michigan but have now found their way to Illinois. The adult beetles are a slender, elongated insect about 1/3 – 1/2 inch long and nibble on ash foliage but cause little damage. However, the larvae feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. Without intervention these very destructive insects will disrupt the tree’s circulatory system and cause the premature death of the infected trees due to the loss of water and nutrient flow throughout the tree. These pests can only be controlled by a systemic insecticide injected directly into the base of the tree using an Arborjet pump system. These injections can be done throughout the year whenever the need arises.
Fall Webworms create white hair-covered egg masses contain several hundred light yellow eggs. Young larvae are pale yellow with 2 rows of black marks along their bodies. When fully grown, they are covered with whitish hairs that originate from black and orange warts. Larvae vary as to their coloring and markings, but are usually greenish with a broad, dusky stripe along the back with a yellow stripe along the side. The pupal stage is brown. Adult coloration varies considerably from pure white to white with black spots with a wingspread of about 32 mm. This pest over winters as a pupa in a cocoon that is concealed in ground litter, cracks and crevices, or in the soil. Adults first appear in mid-June but may continue to emerge in small numbers during most of the summer. Females usually deposit their egg masses on the undersurface of the leaves. Larvae hatch in approximately 7 days. They immediately begin to spin a small silken web over the foliage on which they feed. As they grow, they enlarge the web to enclose more and more foliage (Image 2). The remains of these nests may persist through winter. These webs may sometimes surround 2-3 feet of infested branch. Larvae are gregarious and feed together until the last molt, after which they may feed independently. Larvae mature in about 6 weeks. Mature larvae leave the web and pupate on or in the soil. There may be one or two generations each year, depending on the geographic location. Proper insecticide use will help to control these type of insects.
Japanese Beetles as an adult are a colorful beetle 1/3 – 1/2 inch long with a shiny metallic green color and coppery brown wing covers. There is a row of five tufts of white hair along each side of the abdomen and two additional tufts on the top of the abdomen tip. The larvae are white grubs that take on a grayish cast from the accumulation of soil and fecal matter in the hindgut. They have a characteristic “C”-shaped form, grow to about one inch long, and may be separated from other turfgrass feeding grubs by their characteristic “V”-shaped pattern of spines on the underside tip of the abdomen. The bottom of the V points toward the head and may be seen with a hand lens. The Japanese beetle has a one year life cycle, spending about 10 months as a grub in the soil. In late June, the first adults emerge with most present in July and August. Some may still be found in early September. Throughout the summer, adult beetles feed on a wide range of plants and deposit eggs in the soil. Eggs hatch about two weeks later and grubs feed on decaying matter and roots until temperatures cool in the fall. They move downward and over-winter as a partially grown grub and resume some feeding activity in spring. Pupation occurs in late spring and adults begin emerging in late June. Japanese beetles are chewing insects that destroy leaves, flowers and fruits of more than 276 plants. These beetles can completely skeletonize leaves, feed on corn silk and corn ear tips and are especially destructive to grapes, peaches and other members of the rose family. The grubs feed on grass roots in lawns, and repeat the life cycle until properly controlled.
Lace Bugs (Plant Bugs) use their sucking mouth parts to feed on plant sap. Damage ranges from many small white spots on the leaves to distortion or destruction of plant tissue, depending on the pest and host plant. Some feed on many different types of plants while others feed only on a narrow range or single species. Fourlined plant bugs feed on many herbaceous and woody ornamentals including currant, rose, forsythia, sumac, and viburnum. The nymphs are bright red or yellow, adults is yellow to yellow green. Both stages have four distinct black lines running the length of the body, hence their name. This plant bug can be very destructive, especially to herbs and mint. It feeds first on the upper, tender foliage leaving distinct reddish-brown spots. These spots, the plant’s reaction to enzymes injected into the leaf by the insect, can range from white to almost black depending on the host. Feeding by large numbers of plant bugs can produce large brown blotches and/or leaf distortion. Females cut slits into the host plant and lay six to eight eggs inside. There is one generation a year. It occurs during a six-week period from late May through June. Honey locust plant bugs, are 3/16″ long, light green insects that cause honey locust and black locust foliage to become discolored, stunted, or deformed. These insects do their damage early in the spring but the symptoms persist through the season. Severe infestation can even cause twig dieback. Adults occur from late May to early July. There is one generation occurs per year, eggs are laid in the woody tissue and overwinter there. On problem trees, watch carefully for signs of activity in the spring. Examine terminal foliage for presence of the insects. Treatment when leaves first open with the proper control will achieve the best results.
Leaf Hoppers consist of any of the small, slender, often beautifully colored and marked sap-sucking insects of the large family Cicadellidae (Jassidae) of the order Homoptera. They are found on almost all types of plants; however, individual species are host specific. Although a single leafhopper does no damage to a plant, collectively they can be serious economic pests. Their feeding may injure the plant in any of several ways: by removing sap, destroying chlorophyll, transmitting diseases, or curling leaves. The host plant is also punctured during egg laying. Most leafhoppers are several millimeters long; some may grow to 15 mm. They excrete honeydew, a sweet by-product of digestion, and are responsible for hopperburn, a diseased condition caused by the insects’ injection of a toxin into the plant as they feed. Control is best achieved with the proper treatment of a contact insecticides applied at the correct time.
Scale Insects are parasites of plants, feeding on sap drawn directly from the plant’s vascular system. A few species feed on fungal mats and fungi, e.g., some species in the genus Newsteadia in the family Ortheziidae. Scale insects vary dramatically in their appearance from very small organisms (1–2 mm) that occur under wax covers (some look like oyster shells), to shiny pearl-like objects (about 5 mm), to creatures covered with mealy wax. Adult female scales are almost always immobile (aside from mealybugs) and permanently attached to the plant they have parasitized. They secrete a waxy coating for defense; this coating causes them to resemble reptilian scales or fish scales, hence the name. Scale insects feed on a wide variety of plants, and many scale species are considered pests. Scale insects’ waxy covering makes them quite resistant to pesticides, which are only effective against the first-instar nymph crawler stage. However, scales are often controlled with horticultural oils, which suffocate them, or through biological control. Proper identification and early intervention is the key to controlling these pests.
Spider Mites are common plant pests. Symptoms of injury include flecking, discoloration (bronzing) and scorching of leaves. Injury can lead to leaf loss and even plant death. Natural enemies include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs and predatory thrips. One reason that spider mites become a problem is insecticides that kill their natural predators. Irrigation and moisture management can be important cultural controls for spider mites. Spider mites develop from eggs, which usually are laid near the veins of leaves during the growing season. Most spider mite eggs are round and extremely large in proportion to the size of the mother. After egg hatch, the old egg shells remain and can be useful in diagnosing spider mite problems. There is some variation in the habits of the different mites that attack garden plants, trees and shrubs. Outdoors, the two spotted spider mite and honey locust spider mite survive winter as adults hidden in protected areas such as bark cracks, bud scales or under debris around the garden. Other mites survive the cool season in the egg stage. As winter approaches, most mites change color, often turning more red or orange. This habit may be why they are sometimes called “red spiders.” Most spider mite activity peaks during the warmer months. They can develop rapidly during this time, becoming full-grown in as little as a week after eggs hatch. After mating, mature females may produce a dozen eggs daily for a couple of weeks. The fast development rate and high egg production can lead to extremely rapid increases in mite populations. Other species of spider mites are most active during the cooler periods of the growing season, in spring and fall. This includes the spruce spider mite and most of the mites that can damage turfgrass. These cool-season spider mites may cease development and produce dormant eggs to survive hot summer weather. Dry conditions greatly favor all spider mites, an important reason why they are so important in the more arid areas of the country. They feed more under dry conditions, as the lower humidity allows them to evaporate excess water they excrete. At the same time, most of their natural enemies require more humid conditions and are stressed by arid conditions. Furthermore, plants stressed by drought can produce changes in their chemistry that make them more nutritious to spider mites. Regular plant monitoring and miticide applications are crucial to controlling these pests.
Tent Caterpillars attack several kinds of broadleaf trees and shrubs and produce unsightly webs, or tents, which detract from the home landscape. Trees with substantial defoliation will have reduced growth and vigor. Caterpillars also can be very common and thus a nuisance as they move around the exterior of a home. The key to eliminating tent caterpillar problems is early detection and use of appropriate cultural or chemical control measures. In late spring or early summer, female moths deposit an egg mass encircling small twigs or on tree trunks. Egg masses are present on trees during most of the summer, fall and winter. The adult moth uses a sticky, frothy substance called spumaline as an adhesive to attach eggs to bark or twigs. Spumaline also is used as a hard protective covering around the egg mass. Caterpillars, or larvae, hatch from the eggs in early spring about the time host plants leaf out. The eastern tent caterpillar and western tent caterpillar feed on new leaves, forming small webs within a few days after hatching and enlarging the webs as they grow. The web or tent is most often in a crotch of small limbs, and serves as a refuge for the larvae during the night and during rainy spells. Larvae move from the tents to feed on leaves, so damage can be found for some distance around the web. Tent caterpillars feed in groups, and thus concentrate their defoliation.