CORVALLIS, Ore. – What to do about garden pests, including insects, plant diseases and weeds, can be a challenge for homeowners who want to effectively manage the pests and do the least possible damage to the environment and human health.
The question-and-answer series below illustrates a strategy called Integrated Pest Management, a systematic approach to identify pests and use tactics that are cultural, physical, biological or chemical. The least toxic methods are always considered first, according to Oregon State University researchers Andy Hulting, a weed control specialist, and Gail Langellotto-Rhodaback, an entomologist.
Q: How do I know if I have pest problems in my garden?
A: Check your plants regularly for pest damage such as missing leaves, flowers or fruit or changes in color, texture or size. Most plant problems in home gardens are caused by poor growing conditions, temperature extremes, poor water management or compacted soil. Look under leaves and use a flashlight after dark, which is when many insects are active.
Q: How do I identify what is causing the problem?
A: Often it's not a pest, but another problem such as sun scald or nutrient deficiencies. "Don't apply pesticides without understanding the problem you are trying to solve," Langellotto-Rhodaback advised. "Many insects are beneficial and do no damage." Some insect pests can be dislodged with simple methods such as shaking the plant or spraying with a high-pressure stream of water.
Your local OSU Extension office and its Master Gardeners can help correctly identify the culprit and at what point in the pest's life cycle it is most susceptible to control measures.
Q: What pest management tool should I use?
A: Integrated Pest Management utilizes a combination of methods to keep pest populations at an acceptable level, with the least toxic first. Cultural methods: Buy healthy plants that are not prone to pest problems, plant them where they will grow well and rotate where annuals are planted to avoid build up of disease populations.
Physical methods: pull or dig weeds and trap pests. Row covers designed to extend the gardening season have been found to also keep insect pests away from plants.
Biological methods: Garden plants can attract beneficial insects, such as parasitic wasps and green lacewings, to help keep pests at bay. Some of the more common ones are alyssum, goldenrod, yellow coneflower, coreopsis and sunflower.
Q: When and how should I use chemical methods?
A: Use chemical methods only if other techniques do not work; chemicals can affect human safety and be toxic to other organisms. Chemicals also can cause problems with leaching, disposal and residue on food crops.
"Avoid broad-spectrum insecticides," Langellotto-Rhodaback said. "They are easily identified at the store by marketing labels such as 'kills 40 different types of insects,' but they also kill any insect they contact, including beneficial ones."
Q: What precautions should I take with chemical pesticides?
A: If you decide to use a chemical, check the label to make sure your intended use or site is included on the label. Then choose one that is least harmful to the environment and to the applicator, specific to the pest and least harmful to beneficial organisms.
Pesticides labeled "Caution" are the least toxic to humans, "Warning" are more toxic and "Danger-Poison" (with a skull and crossbones), are the most toxic. The law requires that you read the label. Be sure to wear protective clothing, especially eye protection, gloves and long pants.
Pesticides are more concentrated than they used to be, according to Hulting, and are made for very specific uses. "You might need only a fraction of an ounce to treat a large area or number of plants, perhaps less than in previous years," he said. "Don't use more product than the label specifies. More is not better."
Q: Where can I get more specific information?
A: For fact sheets, frequently asked questions and podcasts on pesticide use, check online at http://npic.orst.edu/ or call the National Pesticide Information Center at OSU at 1-800-858-7378.