Perhaps you've had the heart-sinking experience of rounding a corner in your yard and discovering that one of your landscape shrubs has been chewed to pieces by insects. Maybe your shrubs have slowly lost vigor, and you learned that an insect was to blame. In many cases, maintaining healthy plants and garden environments can be the best protection against insect pests.
Insect prevention can take many forms and largely depends on the insect pests most likely to affect a particular plant in your area. Generally, preventing bugs on plants requires bolstering the natural defenses provided by the shrub or its environment. In circumstances where natural controls fail, preventative insecticide applications may be warranted.
Keeping shrubs healthy is a positive first step toward preventing and minimizing the impact of insect infestations. As the Texas Agricultural Extension Service notes, most wood-boring insects that affect shrubs are attracted to plants that are already weakened or diseased. The extension recommends choosing good sites for shrubs, assuring that they receive proper water and fertilizer, pruning correctly, removing dead branches and protecting shrubs from lawnmower injury. Be sure to destroy all leaves or branches from infected plants.
Entomologist Diane Alston of the Utah State University Extension recommends biological control as another method of preventing bug infestations of landscape plants. She suggests planting a variety of species with your shrubs, especially those that produce nectar and pollen, and will attract beneficial insects. Some of these, such as ladybugs and certain species of wasps, are natural predators of insect pests.
According to Alston, systemic insecticides provide another option for preventing insects on shrubs. Systemics are taken in by the plant's roots and distributed throughout the plant. This limits the amount of insecticide residue left on the plant and its contact with people. She recommends selecting a long-lasting insecticide. As always, follow instructions on the label when using any chemical product, and do not apply insecticides to any plant not listed on the label.
Most gardeners would agree that preventing an infestation is better than dealing with the headache of treating one. According to the University of Tennessee Extension, most gardeners treat insect problems in shrubs that may affect the appearance of the plant, but do not affect the plant's health. When contemplating aggressive or chemical preventative measures, learn the risk of the pest to your plant's health and improve cultural conditions whenever possible.