While outside enjoying the beautiful weather of early June, inspect your landscape ornamentals for insect pests. Azaleas bloomed beautifully in the spring. Notice the leaves for presence of azalea lacebug, which turns the leaves white. Also, notice plants for bagworms. Early detection makes managing these pests easier.
Azalea lacebugs, which are about one-eighth inch long with light brown bodies, feed on the underside of the leaves. The adults have lacy, clear wings with dark brown to black markings across them. The nymphs are black and spiny. They prefer evergreen azalea varieties but attack deciduous varieties and mountain laurel as well. Sap removal by the sucking, piercing mouth parts of the adults and nymphs causes a spotting visible on the upper leaves. In heavy infestations, leaves may be white and drop prematurely. Black spots of their tarry excrement accumulate on the undersides of the leaves indicating they have been there. The goal is to protect the new green leaves.
Populations are greatest in mid to late summer as the second generation appears. Adults fly readily and are often gone before symptoms appear. Their injury is light to moderate and widely distributed. In contrast, the immature or nymphal stages are wingless and can move only by walking. Injury builds slowly but can become very intense as the insects mature.
Check for infestations so treatment can be applied before the plants are disfigured by the pest. Insecticides such as insecticidal soap or summer horticultural oils may be used, depending on the plant species or cultivar. Always read product labels carefully. Look for information on phytotoxicity that can occur on sensitive plants or under some environmental conditions, such as high temperature. Repeated treatments may be needed to control these pests effectively. Thorough treatment of the undersides of the leaves is needed for best results.
Bagworms, on the other hand, are major pests of needle evergreens such as juniper, arborvitae, cedar, pine and spruce. Numerous bagworms feeding on these plants can strip the foliage and cause them to die. The key is to continue checking these plants before bagworms are able to defoliate them.
By understanding their lifecycle, management is easier. Bagworms overwinter as eggs inside the brown bag that contained the female adult. In late May or early June, the eggs hatch. Small, blackish larvae crawl from the bottom of the bag. Larvae cover themselves with pieces of leaves and bark from the plant as protection over their hind part while they feed. They are hard to notice until small pieces of branch begin to wiggle. They add on to the bag as they grow, making it large enough to withdraw into when disturbed. Bags reach 1.5 to 2 inches long by early September.
Adult males emerge in September. The creamy white, wingless adult females attract the males by releasing a sex attractant pheromone. When the male finds a female, he mates with her through the bottom of the bag.
The fertilized female lays 500 to 1000 eggs, which fill the bag, forcing her to drop from the bag and soon die. The eggs remain in the bag until they hatch the following May.
Bagworms have a single generation per year.
Hand removal of bags during the fall through the spring may be sufficient to minimize the problem if small numbers are present. Since pulling off the bag strips the needles from the branch, remove the bag by cutting it off close to the branch where it is attached.
When numerous small bagworms are attacking evergreens, insecticides are needed to prevent serious damage. The best time to apply an insecticide is before the bags are a half-inch long. This is usually in late June or early July. If the bag is larger than a half-inch, control with an insecticide is very poor.
The recommended insecticides that are easy to handle and only target the larvae are products containing the bacterium Bacillus thuringiensis (Bt). Bt is considered a biological control. It is not toxic to birds and beneficial insects. The Bt bacteria produces a protein toxin that disrupts the stomach lining of the larvae; therefore, the toxin must be eaten. The insect may not die for several days, but the feeding stops. It is important to remember Bt is effective on young larvae only. Dipel and Thuricide are two products containing Bt, but there are others. Read the label carefully.
Insecticides containing pyrethroids as the active ingredient can be used for managing bagworms up to a half-inch in length. Read the label to make sure the product lists the type of plant you want to spray; otherwise, you may injure the plant. In addition, follow the label instructions for application.
For more information about azalea lacebugs and bagworms, contact the Daviess County Cooperative Extension Service at 270-685-8480 or through email at firstname.lastname@example.org
Take advantage of beautiful weather by weeding the garden and landscape. Removing smaller weeds is easier and keeps them from maturing and producing seeds for the years to come.
Owensboro Regional Farmers’ Market, at 1205 Triplett St, is open from 8 a.m. to noon or sell out on Tuesday and Thursday. New this year is a Thursday evening market from 4 p.m. to 7 p.m. The Saturday market is from 8 a.m. to noon. The market is arranged to protect both the customer and the vendor while providing access to locally grown produce, flowers, and meats as well as local baked goods, jams and jellies.
Annette Meyer Heisdorffer is the Daviess County extension agent for horticulture. Her column runs weekly on the Home & Garden page in Lifestyle. Email her at email@example.com.