I received a question from reader Myra C., asking about a particular pest that was setting up shop on her roses. The pest was a Japanese beetle, and roses are one of their favorite snacks. This leads us to this week’s common gardening question: How do I deal with insect pests on my plants?
The best place to start would be to identify which insect you are dealing with. Not all insects are pests. Most insects are helpful, while just a few are deemed harmful. Some insects are pollinators necessary for food crop production, while others are the natural predators of the insects that are pests, so we don’t want to harm those guys.
It can be difficult to determine which pest is doing what unless you catch the culprit on your plant, as Myra did. However, there are a few characteristics of both the insect and the damage it causes that can help you narrow it down.
The feeding habit of pests is the first telltale sign once damage has occurred. Pests are either chewers or suckers. Chewers have mouth parts called mandibles that move side to side like a hedge trimmer. Shrubs, bark, foliage or other plant parts that appear to be chewed may have been damaged by chewing pests such as beetles, caterpillars, dragonflies or grasshoppers.
Suckers have mouth parts that resemble a needle or straw, and feed on plants by piercing the tissue and sucking out liquid. Foliage that appears bronzed, spotted or blotched, stunted or dropping could be the work of sucking insects. Aphids, squash bugs, box suckers, spider mites and scale are all examples of sucking insects.
Just as we have foods that we favor over others, so do insects. The Japanese beetle, for instance, has an appetite for roses, raspberries, grapes and apples. However, they have been known to feed on more than 300 species of plants. Tea scale insects are notorious for sucking on camellias, bagworms enjoy arborvitae and juniper, while azalea lace bugs are mainly found on, you guessed it, azaleas.
Early detection can prevent serious plant damage. The Extension offices of Alabama A&M and Auburn University have a monthly “to-do” calendar which includes the following pest management plan:
• March — Roses: Watch new growth for aphids. Begin a spray or dust program.
• April — Fruits and nuts: Start spray program for all fruits; Other: Spray camellias, hollies, etc. for scale insects.
• May — Fruits and nuts: Continue spray program; Shrubs: Do not spray with horticultural oils when temperature is above 85 degrees Fahrenheit; Roses: Spray or dust for insects and diseases; Other: Watch for insects on day lilies.
• June — Fruits and nuts: Continue spray program; Shrubs: Lace bugs may be a problem on azaleas, pyracanthas, dogwoods, cherry laurels and other shrubs. If scale insects continue on shrubs, use materials other than oils; Annuals and perennials: Monitor for insects; Bulbs: Watch for aphids and thrips on summer bulbs.
• July and August — Keeping flowers, shrubs, trees and lawns healthy is a major task this month. Observe closely for insects and diseases.
• September — Shrubs: Check early camellia varieties for insect damage. Roses: Protect fall crops of blossoms from aphids and thrips. Keep plants healthy. Other: If oil spray is needed, do not use in freezing weather. Monitor house plants for insects before moving them indoors. Treat as needed.
• October — Spray with oils before freezing weather to kill scale, mites, etc.
• December — Fruit and nuts: Put on dormant oil spray for scale.
Effective pest control is a combination of strategies that make up “Intelligent Plant Management.”
Early and proper identification, cultural and biological considerations, application timing, using the correct application methods and monitoring plants all work together to reduce damage done by pests.
Understanding the pest, its life cycle and habits will lead you toward effective management options. Treatments are most effective during an insect’s younger stages and knowing when the insect is most active gives you the ideal opportunity to control it when it is present and vulnerable.
Although insecticides can be useful in insect pest management, they should be used with caution and according to the label instructions. Beneficial natural predators of insect pests are essential to keep the pest population down, so using products designed to rid the garden of unwanted insects without diminishing the good bug residents is optimal. The use of soft insecticides, including horticultural oils and insecticidal soaps, rarely harm beneficial insects when used properly and can be used to preserve the presence and activity of these good guys.
Thank you, Myra, for the great question. If you have a gardening question that’s bugging you, send it to me and I’ll be happy to answer it. Until next week, happy gardening.
— Irland, a member of the Limestone County Master Gardeners, can be reached at firstname.lastname@example.org. Visit http://mg.aces.edu/limestone for more information on the Limestone County Master Gardeners.