Looking for insect pests early in the year on landscape shrubs and trees makes it easier to manage them and reduces stress on the plants.
Bagworms feed on the needles of evergreen trees and shrubs. Azalea lacebugs damage the azalea leaves turning them white. Early detection of these common insect pests prevents major damage.
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 it.
Understanding the lifecycle of bagworms makes managing them 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. 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 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. Cut the top of the bag off near the branch where it is hanging to avoid stripping needles when pulling on the bag.
When numerous small bagworms are attacking evergreens, insecticides are needed to prevent serious damage to the plant. The best time to apply an insecticide is before the bags are a half-inch long. This usually is 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. An important point to remember is 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.
Remember to look at the underneath side of the azalea leaves, too. Azalea lacebugs, which are about one-eighth inch long with light brown bodies, may be found there feeding on the leaves. 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 removal by the sucking, piercing mouthparts 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 build up on the undersides 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 very intense as the insects mature.
Check for infestations so that 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.
For more information about bagworms and azalea lacebugs, contact the Daviess County Cooperative Extension Service at 270-685-8480.
Watch 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 the aphids as long as the spray contacts the insects. Read the label to make sure the product controls aphids and are labeled to use on the affected plant.
Owensboro Regional Farmers' Market adds Tuesday and Thursday hours from 6:30 a.m. to noon or sells out at 1205 Triplett Street on June 2.