Garden bugs sometimes turn into common garden pests, causing problems, both in the garden and on trees and shrubs. You will find information on many common pests, such as, aphids, galls, lacebugs, leaf miners, scale, spider mites, tent caterpillar, and wood borers. Also, a description and treatment plan of each pest will be given.
Aphids are sapsucking insects that come in many colors and textures from red, yellow, green, purple, brown, and black to whitish because of a light all-over secretion. You will find some with wings and some without wings. You will find many of them together on the lower surface of leaves.
What they have in common is their tiny size, pear-shaped bodies, long legs, and long antennae. They tend to be group feeders on leaves and stems, but you will occasionally see them alone. Aphids probably won’t destroy your trees and shrubs, but sooty mold can turn the sticky honeydew they release black. You may also notice the foliage wilting, yellowing, or distorting.
Cause: Regular infestations
Treatments: Tree and shrub damage is usually more visual than life threatening. So unless they are so severe or life threatening for the plant, you can just hose the foliage and stems down with a powerful stream of water to displace them. If you want something more, spray your plants with insecticidal soap or horticultural oil.
Many beneficial insects such as ants, lady beetles, and parasitic wasps will destroy aphids if you don’t destroy them first. You should encourage natural predators in your garden. You should, however, skip heavy-duty insecticides because they kill not just the bad guys but also the good ones.
Mites, wasps, aphids, and midge flies can all bring about galls. The insects that make galls are most active when trees leaf out in the spring.
Galls are abnormal growths of plant tissue on leaves, twigs, and bark of trees. Oaks host most galls, but they also appear on other trees and shrubs. There are many types of gall and they appear differently on different plants.
Treatment: Hold off on chemical sprays. Sometimes tolerating a pest is the best thing to do. If the infestation is severe, you can simply cut out ugly twigs.
Lacebugs get their name from their decorative wings and hood adorned with a lacy pattern of veins. These sapsucking pests about 1/8” long come in many species that affect a multitude of woody plants. They live on leaf bottoms, where they excrete spots of dark crud as they eat. Minor lacebug damage looks like yellowy white dots on the upper leaf surface.
Heavier, damage is unsightly and leads to blistered yellow leaves and eventually early leaf drop. Repeated severe infestations can kill a plant. Different species attack evergreen and deciduous plants, but damage is most common on evergreens. Shrubs, such as azaleas and rhododendrons may become infested with lace bugs.
Cause: Incorrect planting sites encourage some infestations of lace bugs. You can set some vulnerable plants such as, azalea and andromeda, in the shade since lacebugs like being in the sun.
Treatment: in early spring, start checking under the leaves for eggs, newly hatched numphs, and adults. Keep checking every couple of weeks, since several generations may hatch in one year. Dealing quickly with infestations prevents ugly damage from occurring. As with aphids, you can set upon lacebugs with a hose and give them a hard spray to displace and kill nymphs (immature insects) in spring. Encourage beneficial insects that prey on lace bugs by avoiding chemical insecticides. Instead, drench leaves (especially the bottoms) with insecticidal soap or horticultural oils to control the nymphs when they hatch.
Leaf miners are similar to borers except that the latter go deeper into the plant. The larvae of leaf miners live inside leaves and their damage is visible as an irregular narrow whitish trail on the leaf surface. Most attacks are visible at the beginning and end of summer in mature foliage. Most woody plant families are susceptible to leaf miners.
Cause: Adult beetle and moths looking for suitable host for their larvae to develop. Preventive measures include trying to avoid stressing trees and shrubs with too much or too little water, and provide desirable growing conditions.
Treatment: Chemicals do not work because the larvae are inside the plant. They usually do not cause permanent damage to most trees and shrubs.
Scale insects feed on the sap of both evergreen and deciduous trees and shrubs with mouth parts up to 8 times longer than their bodies. Scales hug their bodies tight to their food source and can be found on leaves, twigs, branches, and trunks. They can weaken and eventually kill the plant they infest, though that is not typical. Two kinds of scales exist, hard and soft. The soft makes honeydew while the hard scale does not.
Cause: Scale appears on trees and shrubs when they are stressed.
Treatment: Maintain healthy trees and shrubs that can survive an attack of scale. Give your plants adequate water and nutrition, especially when stressed by injury or drought. Avoid chemicals that harm lady beetles (lady bugs) and parasitic wasps, their natural predators.
Treatment: Rub them off by hand or prune off severely infested branches. Because adults have a waxy coating that shields them from insecticides, you have to control them when they are overwintering or immature crawlers. Dormant oils work in early spring before trees and shrubs leaf out.
Mites are in the spider family. These teeny red, brown, or spotted sapsuckers damage leaf tissues. Fine webbing will appear on deciduous trees with large infestations. Leaves become spotty, yellow, and then brown before dropping. Common hosts include spruces, arborvitaes, raspberries, roses, crabapples, and shrubby cinquefoils. To see if you have mites, tap a branch while holding a sheet of white paper under it. If you see moving dots, you have spider mites.
Cause: Hot, dry, and dusty conditions help the growth population of spider mites, and wet or humid weather lower them. To prevent them, try to keep your plants healthy, because they like stressed plants.
Treatment: While infestations are light, you can control them by spraying plants with hard jets of water. Do this whenever mite damage is apparent and repeat it weekly for at least 3 weeks. Use repeated applications of insecticical soap or horticultural oil to further lower mite populations.
You have seen them, those ugly, white, larvae-holding, silken webs or tents hung up in tree branches. The caterpillars eat the leaves of deciduous trees. They attack many kinds of trees but like rose, alder, birch, willow, ash, and apple more than most. Although they don’t kill trees, they can weaken them and make them vulnerable to other problems. Vigorous trees withstand an attack and releaf quickly.
Treatment: Eliminate egg cases from trees. They are made of a foamy-looking gray to brown hard substance and are about 11/2 inches long. Remove the cases with pruners or by hand. Get rid of hatched caterpillars by eliminating their nests from the limbs.
These insects, typically moths and beetles, grow under the bark of trees and shrubs, mining the inner bark in an immature, larval state. Most borers are drawn to dead, stressed, or dying trees. The beetles are dark brown, black, or red with with tiny hard bodies. Many species attack conifers but the European elm bark beetle is a transmitting agent for the Dutch elm disease fungus that decimated the American Elm.
Other borer examples are long-horned beetles and carpenter worms, which become moths. Sawdust on the ground and sap mixed with sawdust oozing from little holes are signs that bark beetles have emerged from the trunk of conifers.
Causes: Trees stressed by drought, disease, and physical damage are more prone to wood borers than are robust trees and shrubs. Some prevention can be applied by keeping shrubs and trees in tiptop health. Plant pest-resistant species and take good care of landscape shrubs and trees. Don’t over or underwater them, and make sure their growing conditions are conducive to maximum vigor.
Cut off and get rid of infested branches to prevent the spread of the beetles. If the trunk show lots of beetle damage, you may have to dispense with whole trees to save nearby trees. Any pruning of diseased branches show be advised by a certified arborist.