Other than shrub diseases and yearly problems, your landscaping can be easily overtaken by many various insects. Herbi-Systems’ Expert Tree and Shrub program is designed mainly to prevent infestations. We begin the year with dormant oil and continue prevention through deep root feeding twice a year with a systemic insecticide. It’s always easier to maintain beautiful landscaping with proper prevention techniques. Let’s look at some specific pests that may damage your trees and shrubs throughout the year. Shrub pests are listed alphabetically for your convenience.
- Cane Borer
- Crape Myrtle Bark Scale
- Japanese Beetle
- Lace Bugs
- Leaf Cutter Bee
- Leaf Miner
- Spider Mite
- Spittle Bug
- White Flies
The number one insect enemy in the rose garden is the rose aphid (often referred to as greenfly), a small, green, soft-bodied insect (about 1/16 inch long) often found in large colonies, particularly on the first lush spring growth, sucking the sap from stems. Control by washing off the stems with water or spraying with an insecticide containing acephate or malathion.
Bagworms are caterpillars that make distinctive spindle-shaped bags on a variety of trees and shrubs. They attack both deciduous trees and evergreens, but are especially damaging to juniper, arborvitae, spruce, pine and cedar. Large populations of bagworms can strip plants of their foliage and eventually cause them to die. Infestations often go unnoticed because people mistake the protective bags for pine cones or other plant structures. If only a few small trees or shrubs are infested, picking the bags off by hand and disposing of them may afford satisfactory control. This approach is most effective during fall, winter or early spring before the eggs have hatched. When many small bagworms are infesting evergreens, an insecticide may be needed to prevent serious damage.
This insect is the maggot of the eggs laid by sawflies or carpenter bees in the freshly-cut cane of the rose after pruning. The telltale sign is the neatly-punctured hole visible on the top of the cane. To remove the pest, cut several inches down the cane until there are no more signs of the maggot or pith-eaten core. Seal all pruning cuts with pruning sealer.
Crape Myrtle Bark Scale
The crape myrtle bark scale steals nutrients from the trees’ bark and leaves a black moldy residue on the bark and anything under the tree. The pest is not fatal for the tree. Some homeowner treatment is possible, and Herbi-Systems’ tree and shrub program can control the scale.
See our Crape Myrtle Bark Scale page for full details.
A beetle that will indiscriminately eat parts of the foliage and sometimes the flowers. Pick beetles off the bush by hand or spray foliage and flowers with an insecticide containing acepate or malthion.
Lace bugs are usually detected when injury to the leaves on the host plant becomes evident. The young bugs and adults live on the lower leaf surface and suck up the plant cell contents through slender, piercing mouthparts. This feeding produces numerous yellow or whitish spots on the upper leaf surface. As the insects feed, they deposit their hard, black, varnish-like excrement on the leaf, commonly referred to as “tar spots.” Lace bugs have several generations a season as long as the host plant supports them, so when numbers become high and feeding extensive, leaves will turn brown and drop. To manage lace bugs, periodically inspect plants that have been attacked in the past or are known hosts of lace bugs, and treat as soon as plant injury is apparent. Plants under stress are more susceptible to severe infestations, so evaluate the site and culture for infested plants. In fact, azaleas are less likely to become infested with azalea lace bugs if they are grown in their preferred site—morning sun and afternoon shade.
Leaf Cutter Bee
As its name implies, this very small yellowish-green insect jumps on the undersides of foliage to feast, often leaving its white skin behind. The damage caused by this insect can often result in defoliation. Use an insecticide containing acephate or malathion to prevent it from establishing a strong colony.
This insect is easily spotted on the foliage by the appearance of irregular white chain-like blisters containing its grub. Remove foliage and discard it to prevent further infestation.
When you detect new foliage with a skeletonized pattern, indicating the foliage has been eaten (but not the vein structure), chances are the roseslug has been at work. Remove the infected foliage, and spray with insecticidal soap or an insecticide that contains acephate.
Scale insects feed by piercing plant tissues and feeding on the sugary sap. Excess sap, ‘honey dew,’ is excreted, and falls on foliage below the insects’ feeding site. Sometimes shiny spots of honey dew are visible on plant leaves. These feel sticky when touched. Often it is a sooty, black mold, growing on the sugary drips, which is the first symptom noticed. Scale insects are easily mistaken for brown ‘flecks,’ especially when they are young and among variegated foliage. Search on both sides of the leaves, particularly along main veins. ‘Flecks’ which can be moved with a fingernail are adult scales. In severe cases, stems and veins of plants will be plastered with scales overlapping each other.
The spider mite establishes huge colonies underneath leaves, giving the appearance of salt-and-pepper particles. As mite numbers increase these white speckles will increase in number, the leaf will take on a bleached appearance and die. If the problem is detected early enough, you can control it chemically with insecticides containing acephate or malathion; direct the spray to the underside of the leaves. If you prefer, apply a fine misting of water to the undersides of the foliage to wash the mites to ground level; they are unable to fly, so they will die on the soil surface.
This small, greenish-yellow insect always hides inside a circular mass of white foam on the surface of new stems, usually during the development of the first bloom cycle in early spring. Spray a strong jet of water to remove the foam and the insect.
Adult thrips are about 1/16-inch long and usually have dark bodies with four fringed wings. Their small size makes them difficult to detect in the garden. They mainly attack tender young leaves, flower stalks, and flower buds. Spray young foliage, developing buds, and the soil around the bush with an insecticide containing acephate (such as Orthene or Isotox).
White Flies are small winged insects which look more like moths than flies. They have a powdery wax which both protects them and is key to identification. They are active in all parts of the world and will thrive year round in the South but go dormant during the winter in northern states. Whiteflies are a problem because they have piercing mouth parts which allow them to suck plant sap. This behavior is what they do to feed and host plants are prone to many problems during such feeding. There are many problems that feeding whiteflies cause including: 1) Leaf damage. 2) Sap drainage. 3) Whiteflies excrete honeydew which lures other nuisance insects onto the host plant.
If you have further questions concerning pests, please do not hesitate to contact us.