Managing Insects & Related Pests

Insect species number in the millions worldwide. Although they make their livings in a variety of ways, a great many do so by consuming vegetation. It is not surprising, therefore, that insects constitute one of the major pest groups of turf and ornamentals. Mites, another group of serious plant pests, are related to insects but more closely to spiders. However, it is convenient to include them with insects when discussing control measures. Other plant pests—such as snails, slugs, millipedes and centipedes—fall into other groups. The one thing these groups have in common is that they are all invertebrates. We’ll deal with several kinds of invertebrate pests in this chapter. However, in practice, the vast majority of invertebrates with which you must deal in landscapes will be insects and mites.

Recognizing damage is an important step to managing insects and mites, because you usually see these signs before you actually spot the pest itself. When you do see the signs of infestation, they often tell you the general type of pest present, if not the exact one. Then you’ll know where to look further, if necessary.

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Insects generally feed by either chewing plant tissue or piercing the plant tissue and sucking out plant fluids. An insect’s mouth parts and its method of feeding determines the type of injury it causes. For example, an insect with biting/chewing mouth parts damages plants by physical removal of plant tissue, such as pruning roots, notching out leaves or hollowing out crowns and stems. Insects with piercing-sucking mouth parts, on the other hand, damage plants more subtly by leaving the plant intact and removing fluids. This is an important distinction because of the implications it has for control measures as well as diagnosing damage to determine which pest is responsible.

The keys to controlling insect pests are:

  • Identify the pest.
  • Understand its life cycle.
  • Select and apply an appropriate control method.

The following sections describe important landscape pests. Because insect pests, insect damage symptoms, microenvironments and control strategies differ among turf and ornamentals, we will discuss turf insect pests and ornamental insect pests in separate sections.

TURF INSECTS

Turf insects can be broadly divided into three separate groups depending on the environment in which they are found: soil, thatch, or leaves and stems. Those in soil generally feed on turfgrass roots. Thatch-inhabiting insects live in thatch and feed on turfgrass leaves and stems. Leaf-/stem-inhabiting insects are found almost solely on leaves and stems.

SOIL-INHABITING INSECTS

--White grubs. White grubs, the larvae of several closely related species of scarab beetles, are perhaps the most common and troublesome soil-turf pests on a national basis. The species involved vary from one region to another, but several characteristics remain constant. The grub typically is cream-colored with a brown head capsule, has three pairs of legs and often curls into a “C” shape. It ranges from 0.125 inch long when young to 0.5 to 1 inch long when fully grown, depending on the species.

• Life cycles. Most white-grub life cycles fall into one of two patterns. The most common is the 1-year cycle. The insect spends the winter just below the frost line as a full-grown grub. In the spring, as soil temperatures begin to warm, the grub migrates upward, back to the root zone, where it feeds on roots for 6 to 8 weeks (April to June). In late spring, the grub pupates and emerges as an adult about 1 to 3 weeks later.

The adults of the various species differ in appearance and habits. Some, like the Japanese beetle, are active during the day and feed on the foliage of ornamental plants. Others, like the European chafer, are active at night. Adults mate and females begin to lay eggs in the soil (June to August). These eggs hatch into tiny grubs that immediately begin to feed on grass roots. The grubs molt twice as they feed and grow. They reach the third (largest) stage by September and feed into October or November before migrating downward in the soil for the winter.

Some species have a 2- or 3-year cycle, particularly in the cooler regions. In these cases, the insect spends an extra year or two in the grub stage, feeding throughout the growing season and moving deeper into the soil each winter.

• Symptoms. Damage typically is most obvious in September and October and again in April and May, when the grubs are largest and hungriest. Grub damage is more obvious when turf is under stress.

Turf first appears wilted even under irrigation. Upon closer examination you’ll find that the turf can be pulled up like a carpet due to the grubs’ root feeding. Skunks, birds, moles and even armadillos often feed on grubs and tear up turf in the process.

• How to identify white grubs. The best characteristic to use for grub identification is the rastral pattern—the arrangement of the small hairs and spines on the raster, the ventral side of the grub’s posterior end (see illustration). This patterning is characteristic for most species. You can view it with a 10x eyepiece, available from many suppliers and surplus outlets.

Although numerous kinds of grubs exist, a relatively small number are responsible for most damaging infestations. On page 119, we show the most important species you’re likely to encounter. To find out which species is damaging your turf, match the rastral pattern you see to one of those shown on the previous page.

--Mole crickets. Mole crickets (see illustration) are relatives of grasshoppers that are well adapted to burrowing in soil. They have an enlarged thorax (shoulder region) that pushes soil and strong, thrusting hind legs. The front legs are enlarged and act like spades for digging and like scissors for cutting small roots. The body is light brown and usually is covered with light brown, velvety hairs. Adults are 1.0 to 1.5 inches long. Immature mole crickets resemble adults except that they are smaller and have very small wing pads. All stages feed on grass roots and tunnel through the soil, often causing the turf to dry out.

Mole crickets are most common in the Southeast and can cause significant damage on a variety of warm-season turfgrasses. The Changa and Southern mole crickets are the most common and troublesome species in the Southeast. The Northern mole cricket occurs much less frequently.

Mole crickets spend the winter months as adults. In the spring, the adults burrow several inches into the soil and lay up to 35 eggs in a cell. Eggs hatch in 2 to 3 weeks, usually in May or early June, and the nymphs (immatures) begin feeding on the roots of various plants. Most individuals complete their development by late fall and spend the winter as new adults, deep in the soil. Mole crickets tend to be most active at night and can cause a nuisance in the spring when adults are attracted to lights during mating flights.

--Wireworms. Wireworms (see illustration) are the larvae of click beetles and occasionally occur in large numbers among turfgrass roots. They are slender, shiny, relatively hard-shelled, about 0.5 to 1-inch long and usually dusty brown.

Wireworms have a long life cycle. Adults often live for nearly a year and lay eggs near grass roots. Wireworm larvae hatch and spend 2 to 6 years in the soil, depending on the species. Generations often overlap, so adults and larvae are present at the same time. Adults are not particularly mobile, so populations can build to significant levels over the years.

Wireworms seldom cause serious turf damage, even when they are present in large numbers. Damaged turf has irregular dying or dead patches in which roots are partially eaten.

--Billbugs. Several species of billbugs (see illustration) damage turfgrass throughout the United States. Some of the more common species are the hunting billbug on zoysiagrass, the Phoenix billbug on bermudagrass and the bluegrass billbug on Kentucky bluegrass.

Billbug larvae are small (0.25 to 0.375 inch), legless and cream-colored with brown heads. They often have a gray or black patch in the middle of the back, and the mid-section usually is noticeably broader than the head. Billbug adults are weevils (beetles with long snouts). The body is black, appears somewhat pointed at each end and is relatively broad in the shoulder region.

Most billbug species overwinter as adults in protected areas. In the spring, the adults begin to move around, and you often can find them on driveways or sidewalks adjacent to turf. Adults lay eggs in May and June. The eggs hatch in about 2 weeks, and the young larvae feed inside the grass stem for a while before moving down the stem to feed on the crown. The larvae pass through several molts, feeding as they grow, and end up feeding in the root zone.

In northern regions, larvae are most abundant in July and August. They complete their development in August, pupate and emerge as adults. You may find these new adults in large numbers on driveways and sidewalks in September and October. As cooler weather approaches, the billbugs find shelter in hedgerows or other protected areas and prepare for winter.

You readily can pull billbug-damaged turf out by hand because the stems break off at the crown. Often larvae feeding in the root zone leave behind a fine white material that looks like sawdust. The sawdust-like material is a good indication of billbug activity.

Usually, by the time billbug damage becomes noticeable, it is too late to get satisfactory control with pesticides. Successful control depends on anticipating the problem. Watch for billbug adults on nearby sidewalks in the spring. If more than five billbugs are observed during a 5-minute period, consider applying an insecticide to the affected turf areas. Make the application on newly mowed turf (generally in June or early July) and water it in lightly to move the material into the thatch, where the young grubs are active.

--Black turfgrass Ataenius. The black turfgrass Ataenius (BTA) (see illustration) is a close relative of white grubs, but the life cycle is markedly different. The grub resembles the white grub (cream-colored, three pairs of legs, C-shaped), but it is much smaller—only 0.25 inch long when fully grown.

BTA overwinters as adults in protected areas, such as clumps of tall fescue or ground covers, and migrates to turf areas in early spring. Adults mate, and females lay eggs in May or early June. Grubs hatch in about a week and begin feeding. They pass through two molts and reach the largest grub stage in June or July. These grubs then pupate, emerge as adults and usually lay eggs to produce a second generation of grubs. This generation feeds on turf roots in August and early September, pupates and emerges as adults in September. These adults migrate to overwintering sites later in the fall.

Damage is most apparent in July, particularly if the weather is unusually warm, and again in August. Damage resembles drought stress and can cover large turfgrass areas, such as an entire fairway, if the insect population develops unchecked.

The best time to control BTA is when adults are laying eggs in the spring. Timing is critical but should be correct if your applications coincide with the flowering of Vanhoutte spiraea or black locust. Lightly water these applications in because the adults reside in the thatch. Do not water so heavily that you wash the insecticide past the thatch and into the soil below.

Another control alternative is to treat the soil to kill young larvae as they hatch. Make these applications from late May on, depending on the local weather and grub activity. Timing is not as critical, but you must water these applications into the soil thoroughly for them to be effective. In general, once damage is evident, control won’t be effective. This is because grubs have already finished feeding and will not be affected by the insecticide.

--Ground pearls. Ground pearls (see illustration) are tiny scale insects that attack the roots of many warm-season grasses, particularly bermudagrass and centipedegrass. The life cycle of ground pearls is not well understood. Apparently mature females emerge from their protective shells, move a short distance and lay eggs in the soil. Nymphs hatch and attach themselves by their mouth parts to nearby roots and remain for the duration of their development. Nymphs suck nutrients from the roots, begin to grow and produce a hard, pearl-like shell that may become as large as 0.19 inch in diameter. A typical generation (egg to adult) takes at least 1 year to complete and may take 2 or 3 years. Damage from ground-pearl activity is caused by the pruning of fibrous roots and removal of plant fluids. Turf turns yellow, resembling drought stress, and eventually brown. Damage appears in irregular patches. Insecticidal control is extremely difficult, partly because the insect spends virtually all of its life cycle protected by a hard, waxy shell that insecticides cannot penetrate. Furthermore, ground pearls may develop at depths up to 10 inches. The best approach to their control is to provide optimum growing conditions, particularly in terms of irrigation and fertilization, to enable the turf to tolerate ground-pearl activity.

THATCH-INHABITING INSECTS

--Chinch bugs. Chinch bugs (see illustration) are small, white-and-black insects about 0.20 inch long when fully grown. They suck plant juices from grass plants. Severe feeding causes yellowing of the turf in spots. These spots often turn brown and die. In many instances, damage takes place without the chinch bugs being observed.

Several different species of chinch bugs occur in the United States, but only a few are known to cause damage to turf. One species, the southern chinch bug, infests St. Augustinegrass and other grasses. The hairy chinch bug, commonly found in the Northeast and Upper Midwest, feeds on bentgrasses, fescues and Kentucky bluegrass.

Life cycles are similar between the two species. The black-and-white winged adults overwinter in taller grass and debris. The Southern chinch bug continues to be active during winter in the South, but its development is slow. In spring, adult chinch bugs move from hibernating sites to growing turfgrasses where they feed and mate. The female chinch bugs lay about 100 to 500 eggs over a 3- to 4-week period.

Eggs hatch into tiny, red-and-white nymphs about half the size of a pinhead. These nymphs feed on plant juices and continue to grow. As they enlarge, they shed their skins four times before becoming a winged adult. With each shedding, the nymph increases in size, becoming black with a small white area between the wings. The wings of the adult are white.

In the northern United States, two generations of chinch bugs generally hatch each year; in Florida, Louisiana and other Southern states, the Southern chinch bug may have overlapping generations. In late summer, the population in turf can build up to 200 to 300 per square foot. Both adults and nymphs are found in sunny areas in uneven clusters or patches, not distributed uniformly over the lawn. When chinch bugs are numerous, you’ll find them on sidewalks, driveways and even on the sides of houses.

To determine if chinch bugs are causing damage, it often is necessary to flood them out of their feeding sites. A simple method is to remove the bottom of a metal coffee can and drive the can into the soil at the periphery of the damaged area. Fill the can with water and check for chinch bugs floating in the can for the next 5 minutes or more.

--Sod webworms. Sod webworms (see illustration) are the larvae (caterpillars) of a number of moth species. Of those species attacking turf, the vagabond webworm, silver-striped webworm, bluegrass webworm, tropical sod webworm, and the lawn or large sod webworm are most damaging.

One sign of sod webworms is the presence of small buff-colored or almost-white moths flying just above the grass in a zigzag pattern in the early evening hours. These moths collect around lights and screens after dark. When at rest, the moths are tubular in shape because of how the wings wrap around the body. Most sod webworms pass the winter as larvae, tightly coiled in a closely woven silk case covered with particles of soil. In the spring, the webworms change into pupae within cells in the soil. Adult moths soon emerge to mate and lay eggs. Eggs are laid by the female sod-webworm moths while flying low over the turf in the evening hours. Eggs hatch after about a week, and the young webworm larvae begin feeding on turfgrass leaves. Sod-webworm damage results from feeding larvae—the adult moths do not feed. Sod webworm larvae construct silken-lined burrows or tunnels in the thatch. Their feeding consists of clipping off the grass blades just above or at ground level and eating them. Most feeding occurs at night and in the early morning. The larvae hide in their burrows during the day.

In healthy turf, a considerable number of webworms are necessary to cause visible damage—in most instances, at least six webworms per square foot of turf. Usually, the first generation of sod webworms in early summer are not numerous enough to cause damage. But in each succeeding generation, 6 to 8 weeks later, the number of webworms can greatly increase. The caterpillars have bigger appetites as they grow larger, reaching a full size of 0.75 to 1 inch long. They are gray to dusky-green with a dark brown head and brown spots over the body. Most areas of the United Sates have 2 or 3 generations a year.

Sod-webworm feeding first causes small, irregular areas of dead or dying turf. These small patches merge as they enlarge from continued webworm feeding. If the number of webworms in the turf is high, they can severely damage the turf in a few days. Badly damaged turf has many ragged, uneven patches of dead grass. Pencil-sized holes are produced by birds digging webworms out of their silken burrows. Much of this bird feeding occurs in early morning.

--Cutworms. Cutworms (see illustration) that damage turf include several types: black cutworm, variegated cutworm and bronzed cutworm. Cutworms are a group of thick-bodied, dull-brown, gray or dull-black caterpillars up to 1.5 to 2 inches long. These caterpillars usually live in the soil or just under the soil surface during the day and feed on the turfgrass at night. Some species eat only grass leaves, while others cut off plants at the soil surface. When you find cutworms resting in the soil during the day, they commonly are in a curled position—the same posture they assume when disturbed. Adult cutworm moths are active at night and common around lights and on windshields. They are dull-black, gray or brown with a wing span of about 0.5 inch.

--Armyworms. The armyworm (see illustration) commonly overwinters as a larva or pupa. The worms are green with black stripes down the center of the back and along each side. They measure about 1.5 inches long when fully grown. Adult moths are bright brown with a white spot near the center of each front wing. The moths often appear in large numbers around street and building lights in summer. The eggs are greenish-white and laid in rows on the lower leaves of grasses. Three generations of armyworms commonly hatch each year.

Armyworms cause damage by devouring grass, usually in circular patches. An “army” of worms hatching from egg clusters in a concentrated area can completely eat the grass from a small area before migrating to other areas in the lawn. These insects feed more commonly at night but do not hide completely during the day.

LEAF-INHABITING INSECTS

--Aphids. Aphids, or plant lice (see illustration), are soft-bodied, usually wingless, slow-moving insects. Certain species, such as the greenbug or the oat-bird cherry aphid, have been observed feeding on turfgrass, especially bluegrasses. Aphids form a “crowd” on turfgrass leaves and stems and suck juices from them.

The damage caused by aphids is similar to that of other sucking insects such as chinch bugs. Infested areas are circular with the grass turning yellow or dying. These patches are common in the shaded areas under trees. Close examination of the outer edge of the damaged area will reveal aphids massed on the grass leaves.

--Mites. Mites (see illustration), which are relatives of insects, are small and difficult to see without a hand lens or magnifying glass. Mites are eight-legged, wingless and usually oval-bodied. They feed by sucking sap from grasses, causing mottling or blotching of the leaves. Severe feeding by high populations of mites can kill turfgrass.

Several species of mites can occur in lawns anywhere in the United States. Spider mites are yellowish or greenish, often with two or more dark spots on the body. They feed on many plants including grasses. The white, worm-like bermudagrass mite feeds on bermudagrass in the Southwest. Another important species is the clover mite. These greenish to reddish-brown mites feed on clovers and other plants in addition to turfgrasses. They are more of a household pest, however, migrating up the exterior walls of homes. They often find their way inside homes in late fall, winter and early spring, crawling on window sills, drapes and the insides of windows.

Mite control with chemicals is not often necessary. Only when many mites are feeding on each grass plant will you observe damage. Mite numbers are usually kept in check by insects and predatory mites. Sometimes the predator population is absent, reduced by insecticides or not numerous enough to keep the pest mites in check.

--Scales. Scale insects (see illustration) are mobile only in the young, immature stages. After that, they settle in a location on the leaf or stem, feed with needle-like mouth parts and usually cover themselves with an armored or shell-like protective covering. These tiny, globular or oval insects are easily overlooked when you examine turf.

Two species of scale insects feed on turfgrass leaves: Rhodesgrass scale and bermudagrass scale. The Rhodesgrass scale is found in the Gulf states and other southern states toward California. It attacks turfgrass crowns causing infested plants to wither and die. The Bermudagrass scale infests bermudagrass, especially in shady areas.

Both scale insects begin as nymphs, or crawlers, that move around on the plants before constructing their armored or shell-like covering. The covering of the Rhodesgrass scale is dark purplish-brown with full-grown insects about 0.125 inch in diameter. Bermudagrass scales are white when mature and 0.06 inch long. Infested crowns have a moldy appearance.

When numerous, scale insects produce dead areas in turf, especially in the shade. Detection is difficult because of their small size and lack of activity on the crowns of turfgrass.

ORNAMENTAL PESTS

Insect pests of ornamentals often are host-specific, and larval stages (which often are not highly mobile) usually remain on the host as they develop. Therefore, accurate plant identification is an important part of diagnosing insect problems. As we mentioned earlier, insects possess either biting/chewing mouth parts or sucking/piercing mouth parts. Let’s look at important examples of each.

• Chewing insects. Most damaging chewing insects are the larval stages of insects. Beetles, butterflies and moths, grasshoppers and related insects, and wasps feed on foliage during their immature stages, and, in some cases, as adults as well. Roots also are commonly attacked. Leaf-feeding damage usually is quite easy to spot. Parts of leaves are chewed off, or in some cases, entire branches are stripped bare. In other cases, insects feed on layers of leaf tissue without consuming the entire leaf. Thus, they leave thin leaf “skeletons” behind. Leaf miners leave peculiar trails or pockets in the leaf.

Another common strategy of many leaf feeders is to live among the young leaves of a shoot tip, often binding them together with silk. Other caterpillars do this with older leaves as well, creating tunnels or nests in which to live. These are the leaf folders, leaf rollers and leaf tiers. Some caterpillars live in groups and build large webbed nests that are quite conspicuous. These are the tent caterpillars and webworms.

As this discussion shows, leaf feeders can leave a variety of signs and include many types of insects. They all ultimately do the same thing: They consume foliage. Sometimes you will never find the feeding insect itself. Often this is because the damage was caused by a generalized feeder, such as grasshoppers. These insects, unlike host-specific insects, are mobile and often feed and then move on. Thus, you see the damage but do not find the insect. This type of damage is often difficult to distinguish from feeding due to caterpillars.

• Sucking/piercing insects. This group includes aphids, scales, whiteflies and mites, among others. These pests cause damage different from that of chewing insects. On leaves, speckling is a common symptom. Each small, light-colored spot is a point at which the pest inserted its mouth parts and withdrew plant fluids. This is typical of mites and leafhoppers. Insects such as scales simply stay attached to one site, and so the insects themselves are what you’re likely to spot.

Aside from foliar discolorations, sucking insects cause cupping, curling and other distortions of leaves and shoots. These result, in part, from toxins that the insects inject while feeding. Another sign of sucking insects is the growth of sooty mold. This fungus lives on honeydew excreted by sucking insects. Though unattractive, sooty mold is harmless to plants and is an excellent means of spotting infestations. The most serious damage of sucking insects results from the withdrawal of sap. This can amount to a great proportion of the plant’s resources if pest populations are large. Lack of vigor and dieback often result.

BEETLES (COLEOPTERA)

As with turf, beetles pose some of the most serious problems for ornamentals. Often it is the larval (grub) stage that inflicts the most serious damage, but adults can be harmful as well. Damage includes foliar feeding, root feeding and wood boring, depending on the pest.

--Japanese beetle. Japanese beetles (see illustration) were introduced into the United States early this century and have spread through much of the country since then. Both adult and grub stages cause damage to plants. The grubs are damaging to turf but also can harm ornamentals with their root feeding, especially on nursery stock. However, adults cause extensive feeding damage to flowers and foliage, and this is the most common reason ornamentals require treatment for Japanese beetles.

The most favored host is the rose, but numerous other ornamentals are subject to attack as well. The shiny green thorax and brown wing covers of Japanese beetles are distinctive.

Foliar insecticides provide some protection from adult feeding, though repeat applications usually are necessary to protect newly emerging growth. One strategy is to reduce grub populations in nearby turf, which usually harbors the largest populations of developing Japanese beetle grubs. While this may reduce populations in the immediate area, it will not eliminate them entirely because Japanese beetles are excellent fliers and will move in from other areas.

--Leaf beetles. Leaf beetles (see illustration) include several species that consume the foliage of various tree and shrub hosts. The larval stages do the most serious damage, but adults often feed as well. Leaf-beetle larvae have an appearance unlike that of caterpillars, appearing more like grubs (but usually more colorful). Feeding often leaves foliage skeletonized, and the larvae usually live in large groups for at least part of their development.

Elm leaf beetles are one of the more familiar leaf-beetle problems. Foliar or systemic insecticides are effective against leaf beetles.

Many other leaf-feeding insects attack ornamentals in landscapes. Many caterpillars, unlike those discussed above, live solitary lives and do not create nests or produce highly visible damage. Often, the damage is not even noticed. When control measures become necessary, foliar insecticide sprays are almost always effective for foliar pests.

--Root weevils. Root weevils include several species that attack a variety of woody ornamentals. The black vine weevil (see illustration) and the strawberry weevil are two of the most injurious species, feeding on broad-leaved evergreens (notably azaleas and rhododendrons) and conifers (especially yews). The larvae feed on roots, causing severe damage that can lead to plant death. Also, the larvae sometimes feed on stems just above the soil surface, often girdling them completely. Affected plants frequently decline rapidly and die. This is often attributed to other causes because the damage can be inconspicuous. However, a close inspection of feeder roots and stems near the soil line usually reveals feeding damage if these insects are present. Feeding notches on foliage (from adult weevils) are another indication, but other, less-injurious weevils may be responsible. Foliar notching on Taxus (yews) is diagnostic of black vine weevils, however.

Soil-applied insecticides control root-weevil larvae, while adults are susceptible to foliar applications. Even though adults do not inflict serious damage, controlling them reduces subsequent larval populations.

--Borers and bark beetles. The larvae (grubs) of certain beetles that bore into the wood of trees and shrub are borers (see illustrations). The adult beetles lay their eggs on the host plant. When they hatch, the larvae bore into wood, on which they feed, and cause decline and dieback of the affected plant. When they complete their larval stage (which may take one or several seasons, depending on the borer species), borers pupate within the host plant, eventually emerging as adults.

Entrance holes, sawdust-like frass (droppings) on branches, swollen limbs and branch dieback are other typical symptoms of borers. If you cut into wood near entrance holes, you may be able to spot tunneling within the wood or perhaps the borer itself. The difficulty of treating borers is due to the protection they receive by living inside the wood of the host plant.

Bark beetle grubs feed on tissue just inside the bark and on vascular tissue beneath it. The feeding usually occurs in interesting patterns—the larvae tunnel outward from main tunnels creating feeding galleries (see illustration). The gallery patterns are sometimes diagnostic. As the tissue underneath the bark dies, the bark may slough from the plant.

Though a great many plants are vulnerable to many species of borers and bark beetles, the more common and serious pests include:

  • Dogwood borer
  • Shothole borer on cherries, peaches, plums and other trees
  • Elm bark beetles (which spread Dutch elm disease)
  • The bronze birch borer
  • The willow-and-poplar borer
  • The flatheaded appletree borer, which attacks many ornamental species
  • Pine bark beetles, which rapidly infest stressed pines.

Traditional treatments consist of spraying insecticides on the bark of trunks and branches of susceptible species to provide a chemical barrier against newly hatched borers trying to gain entrance. This means you must time the applications to coincide with egg laying and hatch. Extension services sometimes announce treatment windows based on borer hatch times, which often occur in spring or early summer. Products developed relatively recently provide control of some borers with parasitic nematodes. The advantage of these products is that they can provide control of borers even after they’re inside the plant. Thus, timing may not be so critical with these products, though control is not always consistent.

Pruning operations should take place at some time other than when prevalent borers are laying eggs. Apparently, open wounds allow easy entrance for some borers and may even attract them. Many borers lay eggs in spring or early summer, which are not typical times to prune, so this should not constitute a major scheduling adjustment.

Because borers are an ongoing threat, a good practice is to use non-host ornamentals. This avoids the need to treat every year for the same pest. Also, many borers and bark beetles detect stressed trees and attack them preferentially.

Thus, good cultural care also reduces infestations.

BUTTERFLIES AND MOTHS (LEPIDOPTERA)

We are all familiar with the larvae of butterflies and moths—caterpillars. A huge number of species feed on plants, but relatively few become pest problems in landscapes.

Most cause noticeable damage with foliar feeding, though a few are wood borers.

--Tent caterpillars and webworms. These caterpillars are the immature stages of moths and use silk to create nests. Several species have this habit, and host plants include a range of ornamental species. The most common of these pests include the Eastern and Western tent caterpillars and the fall webworm. The nests, which can be large and conspicuous, are not difficult to spot. However, careful inspection of trees that have been affected in past years may allow you to spot the caterpillars before their nests become too visible. Control is usually easy and effective with several insecticides, though occasionally nests are high up in tree crowns and you must use a forceful spray to reach them.

--Bagworms. Bagworms (see illustration) are common pests in large parts of the country, especially the Eastern half. They feed on well over 100 species of plants, including both broadleaf and coniferous types. Bagworm damage consists of foliage consumption, though the familiar “bags” can be unattractive. Bagworm caterpillars live inside these structures throughout their development. These pests can build up high numbers on individual plants because the females cannot fly and must lay their eggs on the same plant.

On isolated plants, it sometimes is practical to simply pick bagworms off by hand. They are so conspicuous, it’s hard not to spot them. If this is not practical, several insecticidal products provide adequate control with foliar sprays.

Entrance holes, sawdust-like frass (droppings) on branches, swollen limbs and branch dieback are other typical symptoms of borers. If you cut into wood near entrance holes, you may be able to spot tunneling within the wood or perhaps the borer itself. The difficulty of treating borers is due to the protection they receive by living inside the wood of the host plant.

Bark beetle grubs feed on tissue just inside the bark and on vascular tissue beneath it. The feeding usually occurs in interesting patterns—the larvae tunnel outward from main tunnels creating feeding galleries (see illustration). The gallery patterns are sometimes diagnostic. As the tissue underneath the bark dies, the bark may slough from the plant.

Though a great many plants are vulnerable to many species of borers and bark beetles, the more common and serious pests include:

  • Dogwood borer
  • Shothole borer on cherries, peaches, plums and other trees
  • Elm bark beetles (which spread Dutch elm disease)
  • The bronze birch borer
  • The willow-and-poplar borer
  • The flatheaded appletree borer, which attacks many ornamental species
  • Pine bark beetles, which rapidly infest stressed pines.

Traditional treatments consist of spraying insecticides on the bark of trunks and branches of susceptible species to provide a chemical barrier against newly hatched borers trying to gain entrance. This means you must time the applications to coincide with egg laying and hatch. Extension services sometimes announce treatment windows based on borer hatch times, which often occur in spring or early summer. Products developed relatively recently provide control of some borers with parasitic nematodes. The advantage of these products is that they can provide control of borers even after they’re inside the plant. Thus, timing may not be so critical with these products, though control is not always consistent.

Pruning operations should take place at some time other than when prevalent borers are laying eggs. Apparently, open wounds allow easy entrance for some borers and may even attract them. Many borers lay eggs in spring or early summer, which are not typical times to prune, so this should not constitute a major scheduling adjustment.

Because borers are an ongoing threat, a good practice is to use non-host ornamentals. This avoids the need to treat every year for the same pest. Also, many borers and bark beetles detect stressed trees and attack them preferentially.

Thus, good cultural care also reduces infestations.

BUTTERFLIES AND MOTHS (LEPIDOPTERA)

We are all familiar with the larvae of butterflies and moths—caterpillars. A huge number of species feed on plants, but relatively few become pest problems in landscapes.

Most cause noticeable damage with foliar feeding, though a few are wood borers.

--Tent caterpillars and webworms. These caterpillars are the immature stages of moths and use silk to create nests. Several species have this habit, and host plants include a range of ornamental species. The most common of these pests include the Eastern and Western tent caterpillars and the fall webworm. The nests, which can be large and conspicuous, are not difficult to spot. However, careful inspection of trees that have been affected in past years may allow you to spot the caterpillars before their nests become too visible. Control is usually easy and effective with several insecticides, though occasionally nests are high up in tree crowns and you must use a forceful spray to reach them.

--Bagworms. Bagworms (see illustration) are common pests in large parts of the country, especially the Eastern half. They feed on well over 100 species of plants, including both broadleaf and coniferous types. Bagworm damage consists of foliage consumption, though the familiar “bags” can be unattractive. Bagworm caterpillars live inside these structures throughout their development. These pests can build up high numbers on individual plants because the females cannot fly and must lay their eggs on the same plant.

On isolated plants, it sometimes is practical to simply pick bagworms off by hand. They are so conspicuous, it’s hard not to spot them. If this is not practical, several insecticidal products provide adequate control with foliar sprays.

--Cutworms. Cutworms (see illustration) are the larvae of several moth species. These caterpillars spend most of their time in burrows underground and emerge at night to feed on plants. Although the caterpillars consume leaves and flowers, they also have the habit of chewing through stems at or near the surface, often severing the plant entirely. Thus, they destroy far more than they actually consume, making even small populations destructive to herbaceous plantings. Because cutworms feed at night, they are seldom seen. However, plants with severed stems lying on the ground or wilting plants that show stem damage near the ground are telltale signs of cutworms. Foliar applications of insecticides or granular baits are the customary control measures.

--Borers. The larvae (caterpillars) of certain moths invade shoots, branches and trunks of trees and shrubs. Damage and symptoms are essentially the same as those of beetle borers—as are treatment strategies—though you should identify the specific pest and obtain appropriate treatment information. A significant wood-boring pest is the lilac borer (or banded clearwing ash borer—they’re the same species of moth) which attacks lilac, ash and other members of the ash family. This insect often leaves pupal cases protruding from exit holes in the trunk when the adults emerge. Another serious pest is the dogwood borer (see illustration), also a clearwing moth.

APHIDS, SCALES, WHITEFLIES (HOMOPTERA)

This group of insects contains a large number of plant pests, including some of the most damaging and difficult-to-control insects. All possess sucking/piercing mouth parts. The serious pests in this group often build to enormous populations that withdraw large amounts of plant fluids, seriously degrading plant vigor.

--Aphids. Aphids (see illustration) are some of the most-recognized plant pests. They are small, soft-bodied insects that may or may not possess wings. Some species have woolly or waxy surfaces. A large number of species exist, attacking nearly every kind of plant. They pierce soft leaf, stem or flower tissue and feed on plant sap. Cupping, curling and other growth distortions are common symptoms of leaves and shoots. Aphids may be visible on young shoots, but they often reside on the undersides of leaves, as well. Some aphids even feed on roots, but aboveground infestations are those which most often require treatment.

Much has been made of biological controls for aphids—parasitic wasps, ladybugs, lacewings—and these are effective in many cases. However, aphids often are able to build to damaging populations in spring or summer before predators can increase to effective levels. Thus, chemical control measures may be necessary. Because aphids often prefer to feed on succulent young shoots, repeat applications may be necessary to protect new growth during growth flushes. Systemic insecticides are useful against aphids.

--Scales. Scale insects (see illustrations) are some of the most difficult-to-control pests. They actually are soft-bodied insects, but the hard covering many species possess provides good protection. These types are called armored scales. Other types lack hard coverings and, therefore, are called unarmored or soft. Several other families are of importance and include mealybugs and cottony cushion scales. Altogether, a great many species occur, and most plants are susceptible to some type of scale. Scales anchor themselves to stems and leaves (or even bark) and suck plant fluids. Because they are essentially immobile, armored scales effectively seal themselves off for protection beneath their hard coverings. This is why they can be so difficult to control. Fortunately, scale parasites offer good natural control of many scales. When they do not, scales can cause extensive damage to plants. A side-effect of scale infestations is the secretion of honeydew, which then gives rise to sooty mold on leaf surfaces. The occurrence of this is a good sign that scales (or other sucking insects) have infested a plant.

The stage most vulnerable to control measures is the crawler stage. Crawlers are immature scales that move to new feeding sites. When they find a suitable site, they settle down and assume the typical scale lifestyle. Until then, they do not possess a protective covering and so are more susceptible to pesticides. Unfortunately, the crawler stage does not last long, so timing is critical and sometimes difficult to gauge accurately. Extension services sometimes announce applications windows, and pheromones also are available as monitoring tools.

Another option applicators use is spray oil (sometimes mixed with a pesticide), which is useful against some scales. Effectiveness depends completely on the degree of coverage, so high-volume applications are typical of oil applications for scales.

--Whiteflies. Whiteflies (see illustration) cause symptoms similar to aphids, to which they are related. Several species are of some importance, but the greenhouse whitefly is the most important. It attacks many plant species, including outdoor landscape ornamentals. Whiteflies are small insects but easily visible to the naked eye. The adults are winged, but the immature stages—found on the undersides of leaves—resemble small scale insects. Various whitefly species attack a great many plant hosts by piercing soft plant tissue and sucking plant sap. This causes curling and cupping of leaves. Further, whitefly infestations often produce copious amounts of honeydew, which causes sooty-mold growth and creates a nuisance for cars parked underneath infested trees.

Persistent control measures are necessary for whiteflies, and even then control may not be adequate. Adult whiteflies are good fliers and spread rapidly, often re-infesting treated sites from nearby areas. In some regions, the deliberate introduction of parasites has dramatically reduced whitefly problems.

WASPS, BEES AND ANTS (HYMEN OPTERA)

Most members of this group are considered beneficial, because they prey on other insects. However, several species can cause problems for the landscape manager.

--Sawflies. Several kinds of sawflies (see illustration) are pests of ornamentals. Sawflies, though they look like caterpillars, are the larval stages of wasps. Often, their posterior ends are curled in a peculiar fashion. Sawflies feed on numerous plant hosts, but each species usually is specific to one or a few types. Birch, pine and rose are some of the more commonly attacked ornamentals.

Several foliar insecticides control sawflies. However, you often can pick off limited infestations by hand because the larvae often congregate in dense masses that are easy to clip out and discard.

--Ants. Ants seldom consume plants directly, but they still can become serious pests in landscapes. Some ants are known to farm aphids, moving them around to different plants and providing them with some protection from natural enemies. Of course, many people consider ants a “nuisance” pest, which they certainly can be. Fire ants are a more serious problem because of the serious reaction people have to their stings, and their mounds can become quite large and disruptive in turf and shrub areas. Several products are formulated specifically for fire-ant control.

Carpenter ants nest in tree trunks. They do not actually consume wood for food. They simply hollow out spaces for the use of the ant colony. Some colonies become large enough to weaken trunks or large branches, creating hazardous trees.

MITES

--Mites. Mites (see illustration) pose serious control challenges to landscape managers. These tiny creatures live on leaf surfaces (usually the undersides). They also commonly create webbing that may be conspicuous when infestations are heavy. Initially, it often is easier to spot the feeding damage than to find the mites themselves. Mites often cause spotting or speckling on leaves that is visible on the upper leaf surfaces. These mark the points where mites have pierced the leaf tissue to feed and should prompt you to inspect the leaves closely. Though tiny, most mites are visible to the naked eye. A 10x or 20x magnifier is a great aid, however. On some plants, conifers for example, feeding may not be noticeable as such. Look for browning and tip dieback, as well as webbing. Other symptoms, depending on the plant, may include purpling, leaf cupping or curling and leaf death. A method some use to inspect for mites is to hold a sheet of white paper beneath a shoot and strike or shake it. If mites are present, some will fall onto the paper, where you can see them crawling around.

If certain plants have a history of mite infestation, monitor them closely—you’ll want to take control measures before populations become heavy. Mites are notorious for rapidly rebounding from control applications. The key to successful mite control is to repeat applications 7 to 10 days after the first one. This way, you’ll kill mites that hatch from eggs laid before the first application (most miticides do not kill the eggs). Complete coverage, especially on the undersides of leaves is essential. Mites reproduce rapidly, so they are able to develop resistance to pesticides relatively easily. Thus, it is important to rotate chemicals when you must make repeat applications for mites.

Mites typically thrive in hot weather. Thus, damage tends to show during summer. Dusty conditions also seem to encourage mites, so dust-control measures sometimes reduce mite populations.

SNAILS AND SLUGS

These familiar pests feed on foliage of many ornamental species, though they clearly prefer some plants over others. When populations are high, serious damage can result. The shiny slime trails snails and slugs leave behind are the surest way to distinguish their feeding from that of other pests. Although several home remedies have long been used—such as beer in a pan or salt granules— pesticidal baits are very effective and fairly inexpensive.

CONTROLLING PESTS

The most important part of controlling pests in landscapes is to provide proper cultural practices for the plants growing there, whether they be turfgrasses or ornamentals. Some insects (for example, pine bark beetles or bronze birch borers) are noted for their ability to detect stressed plants, which are less able to resist attacks. In addition, vigorous plants tolerate higher levels of pests without showing serious symptoms (for example, grubs in turf) and more rapidly outgrow damage that does occur. Proper cultural care does not mean that pest problems will disappear, but in general, they should be less frequent and less severe when plants are healthy.

A range of control products and techniques exists for controlling infestations. Your choice will depend on the pest, the host plant and other site factors. Many pests can be tolerated at low levels, from which only minor damage will result. It is the large populations that require attention. Predators are a vital part of pest control in landscapes, but natural control obviously is not sufficient if damaging outbreaks are occurring. Thus, chemical controls also are a necessary part of maintaining landscapes in acceptable condition. In some cases, introducing predators can substitute for chemical controls. However, this should be thought of as longer-term solution—if immediate control is needed, chemicals often are the only effective option.

Providing good cultural care, encouraging natural predators, using plant species not preferred by prevalent insect pests and judicious chemical applications are all aspects of integrated pest management (IPM). All the aspects of IPM are important for maintaining healthy landscapes and making efficient use of available resources.

Insects come into contact with insecticides in various ways. Contact insecticides are applied as sprays to surfaces, usually foliage, where the target pests reside. Often, it is enough for the insect simply to walk across the treated surface and contact the insecticide with its feet. Leaf-feeding insects ingest foliar-applied chemicals when they feed on treated leaves; this is a typical means of control for many chewing insects. Soil-inhabiting insects contact the pesticide when it is washed down into the soil after an irrigation. Piercing-sucking insects, thought they are susceptible to contact products when directly contacted by them, do not consume foliage, so they do not ingest contact products.

However, several insecticides have systemic qualities, meaning that plants take the chemical into their tissues. When sucking insects feed on sap, they also ingest some of the insecticide with it. Thus, systemic products are especially useful for pests such as aphids, mites, whiteflies and some scales. Granular formulations are effective for treating soil addition, vigorous plants tolerate higher levels of pests without showing serious symptoms (for example, grubs in turf) and more rapidly outgrow damage that does occur. Proper cultural care does not mean that pest problems will disappear, but in general, they should be less frequent and less severe when plants are healthy.

A range of control products and techniques exists for controlling infestations. Your choice will depend on the pest, the host plant and other site factors. Many pests can be tolerated at low levels, from which only minor damage will result. It is the large populations that require attention. Predators are a vital part of pest control in landscapes, but natural control obviously is not sufficient if damaging outbreaks are occurring. Thus, chemical controls also are a necessary part of maintaining landscapes in acceptable condition. In some cases, introducing predators can substitute for chemical controls. However, this should be thought of as longer-term solution—if immediate control is needed, chemicals often are the only effective option.

Providing good cultural care, encouraging natural predators, using plant species not preferred by prevalent insect pests and judicious chemical applications are all aspects of integrated pest management (IPM). All the aspects of IPM are important for maintaining healthy landscapes and making efficient use of available resources.

Insects come into contact with insecticides in various ways. Contact insecticides are applied as sprays to surfaces, usually foliage, where the target pests reside. Often, it is enough for the insect simply to walk across the treated surface and contact the insecticide with its feet. Leaf-feeding insects ingest foliar-applied chemicals when they feed on treated leaves; this is a typical means of control for many chewing insects. Soil-inhabiting insects contact the pesticide when it is washed down into the soil after an irrigation.

Piercing-sucking insects, thought they are susceptible to contact products when directly contacted by them, do not consume foliage, so they do not ingest contact products. However, several insecticides have systemic qualities, meaning that plants take the chemical into their tissues. When sucking insects feed on sap, they also ingest some of the insecticide with it. Thus, systemic products are especially useful for pests such as aphids, mites, whiteflies and some scales.

Granular formulations are effective for treating soil insects, especially in turf. These must be irrigated to wash them into the soil where they can contact soil-inhabiting pests. In some cases, granular insecticides, after being irrigated into the soil, are taken up by the plants, which then gain systemic protection from the product. Recently, soil or trunk-injected systemic insecticides have become a more popular means of treating trees. The advantages of their over traditional sprays are obvious and provide a level of control not usually possible with sprays on large trees.

Baits are useful for mobile insects, insects that do not reside on the host plant (cutworms, for example) and other pests such as slugs and snails. Using baits that attract these pests is more efficient than spraying an entire landscape just to ensure the pest ingests some insecticide. Horticultural oils are not traditional insecticides. They work by literally suffocating insects. Thus, complete coverage is essential for good control with oils. In hot weather, some oils pose a risk of burning foliage, so this type of application is best suited to winter and spring applications for many oil products. Winter-applied oil treatments are referred to as dormant sprays and control insects overwintering on the plant.

Insect growth regulators (IGRs) are a relatively recent development in pest control but show much promise. These chemicals mimic natural hormones that control the life cycle of insects and interrupt the normal development process. Manufacturers already have introduced a few IGR products, and more are being developed for both turf and ornamental uses. IGRs are highly specific to the target pest, so their use does not harm predator populations.

Predators and parasites are used successfully by many landscape managers. Unfortunately, many customers demand more immediate results than predators can offer. When they fit into a pest-control program, however, predators can cost-effectively and successfully control a number of pests. Parasitic nematodes, wasps and flies—as well as predatory insects such as ladybugs, lacewings and mantids—are available from suppliers. Much more remains to be learned about using natural controls in turf and ornamental sites, so this is an actively evolving field.

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