Diagnosing plant health problems may seem like a straightforward endeavor, but often it is a complicated process that can end in a less-than-certain answer. Plant health problems may be caused by a number of different factors - infectious diseases, insect infestations, herbicide injury, site-related stresses, environmental extremes, and improper care practices. And in many cases, more than one factor may be contributing to the decline of a plant. Also, the most obvious symptom on a declining plant may not be an indication of the true cause of the overall poor plant health. For example, raised, black spots on the leaves of a declining maple tree may only be a minor annoyance to the plant, and the primary problem may be that the tree was planted many inches too deep.
Because plant health problems may have multiple or not-so-obvious causes, it is important when submitting samples to the Iowa State University Plant Disease Clinic to include detailed background information, a sample that shows a range of symptoms (from fairly healthy to very sick), and pictures of the entire plant and the surrounding site conditions. When possible, be sure to include the entire plant.
The Iowa State University bulletin Pm 1542, Tips for Providing Plant and Insect Samples to ISU is a good reference for clients who need information on collecting and submitting plant samples. PD 31, Plant Disease Identification Form should be completed and submitted with plant samples.
Once a diagnosis is formulated, a Plant Disease Clinic Report is mailed to the person listed under "submitted by" on form PD 31. In many cases, this is the county extension office. There is a box on the form that can be checked if the report should be mailed directly to the owner. Cardboard boxes of various sizes, a bubble packet, and mailing labels can be ordered from Extension Distribution. There is a $10 fee for most plant samples submitted for plant disease problem diagnosis.
Please contact the Plant Disease Clinic at 515-294-0581 if you need assistance in diagnosing a plant health problem, or if you have any questions on collecting and submitting a sample.
This article originally appeared in the 6/11/2004 issue.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on June 11, 2004. The information contained within may not be the most current and accurate depending on when it is accessed.