Timing is important.
Catching problems early, especially the emergence of insect pests, makes them easier to manage.
Two insect pests to monitor for in the spring include the azalea lacebug and bagworms.
Azalea lacebugs damage azalea leaves by turning them white. Bagworms feed on the needles of evergreen trees and shrubs. Looking for them early avoids major damage to these woody plants.
For azalea lacebugs, remember to look underneath the azalea leaves. Azalea lacebugs, which are about one-eighth inch long with light brown bodies, may be found there feeding.
The lacy, clear wings of the adults have dark brown to black markings. The nymphs are black and spiny. They prefer evergreen azalea varieties but attack deciduous varieties and mountain laurel as well.
Sap removed by the sucking, piercing mouth parts of the adults and nymphs causes spotting, which is visible on the upper leaves. In heavy infestations, leaves may turn white and drop prematurely.
Black spots of their tarry excrement build up on the under sides of the leaves indicating they have been there.
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 intense as the insects mature.
Checking now for infestations allows for treatment before the plants are disfigured. Insecticides such as insecticidal soap or summer horticultural oils may be used depending on the plant species or cultivar.
Always read product labels carefully and 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 coverage of the undersides of the leaves is needed for best results.
Bagworms 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 throughout the year before bagworms have a chance to defoliate them.
Understanding the lifecycle of bagworms makes management easier. Bagworms overwinter as eggs inside the brown bag that contained the adult female. 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.
You don’t notice them 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 1,000 eggs, which fills the bag, forcing her to drop from the bag and soon die. The eggs remain in the bag until hatching 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. Cut the top of the bag off near the branch where it is hanging to avoid stripping needles when pulling the bag off.
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 target the larvae only 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 which 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. Remember that Bt is effective on young larvae only. Dipel and Thuricide are two products containing Bt, but there are others. Read the label carefully.
Also, 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 instructions on the label for applying the product.
For more information about azalea lacebugs and bagworms, contact the Daviess County Cooperative Extension Service at 270-685-8480 or firstname.lastname@example.org.
Annette’s TipWatch vegetables and other plants for an insect pest called aphid. Aphids suck nutrients from plants. Their soft bodies can be green or rose-red. Ladybugs and other beneficial insects will help control small numbers of aphids.
Insecticidal soap also controls aphids as long as the spray contacts the insects. Read the label to make sure the product controls aphids and is labeled to use on the affected plant.
Ongoing EventBeginning June 1, Owensboro Regional Farmers’ Market adds Tuesday and Thursday hours from 8 a.m. to noon or sell out and Thursday evenings throughout June and July from 4 to 7 p.m. at 1205 Triplett Street.
Annette Meyer Heisdorffer, PhD, is the horticulture extension agent with the Daviess County Extension Office. She can be reached by calling 270-685-8480.