Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
1/21/02
Contacts:
Barbara Ambruzs, Plant Pathology, (515) 294-1741, ambruzs@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the Week Beginning January 25, 2002
What Can I Spray?
By Barbara Ambruzs
Plant Pathology
Iowa State University
There seems to be a "just fix it" mentality in our society regarding disease. When people get sick they want a pill to make them feel better. Similarly, when plants get sick we expect medicine for them too. The first question asked by many is, "What can I spray?"
Plant health care, like human health care, begins with growth and development under the best conditions possible. Children raised in unhealthy conditions are at greater risk of developing illness. The same applies to plants. To remain healthy, plants need adequate moisture, light, fertility, air quality, temperature and good soil.
If a plant spends the early part of its life in ground that is too wet, it is likely to have problems throughout its life. Then you buy it, take it home, carefully plant it, give it all the right care and it still dies. It's tempting to think a fungus or bacterium killed it, rather than the poor treatment it received early in life.
A number of factors can contribute to plant health problems and often there are clues that will lead you to the cause. Sometimes the problem is related to site conditions. Is it planted too deep? Is the soil compacted? Was there construction in the area during the last five years or so? Are there buildings, walkways or roads nearby? Are animals feeding on the stems or trunk? If it's a potted plant, is there a crusty layer on the soil? Are the roots outgrowing the pot?
Unless you start plants from seed or cuttings yourself, it is difficult to know what the early growing environment was for plants you purchase. Before buying a plant, check for leaf spots, discoloration, mold, crust on the soil and wounds on the stems or leaves. Look at the roots if possible. They should be white and not potbound.
Next consider where the plant will be living. Can it survive Iowa weather? Will it tolerate disease? What type of soil does it prefer? Will the ground be too dry or wet? Will it get the right amount of sunlight? Also, proper planting is important if the plant will be transferred into a garden or landscape.
If disease is involved, determining the exact cause of the problem will help determine how to treat it. If you need help diagnosing the cause of a plant problem, you can contact your county extension office or the Iowa State University Plant Disease Clinic. The clinic charges a $10.00 fee per sample.
If you have a sick plant, you may be able to nurse it back to health. Start by improving growing conditions and removing diseased plant parts such as fallen infected leaves or branches.
If you use pesticides, the law requires that you follow the rates described on the label. Research shows that chemicals will be most effective if used properly. Correct timing for pesticide use is crucial. If you use a pesticide at the wrong time, the disease organism might not be there or may be at a life stage during which it can tolerate pesticides.
It may be easier to spray a chemical or take a pill than do manual labor or wait for healing. Most of us want to see results now. Health is something that happens over time. When you use all tools at your disposal to grow healthy plants with the least toxic pest control methods you are using Integrated Pest Management (IPM). Following IPM techniques will benefit not only your plants, but the environment as well.
There's a growing trend toward managing plant health rather than trying to control plant diseases. You can join this trend by asking, "What can I do to keep my plants healthy?" rather than, "What can I spray?"
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