Correct diagnosis is the first step to effective disease management

The quality of the sample, the information in the submittal form and the shipping time are important for an accurate health plant analysis. Follow this checklist to get it right!

April 3, 2014 - Author: Lina Rodriguez Salamanca, Michigan State University Extension

The key to effective disease management in vegetable crops starts with the correct diagnosis of the causal agent. Yellowing, necrosis or plant tissue death, stunting, patterns in the foliage and browning can be symptoms of a disease or a disorder.

When symptoms are caused by pathogens such as bacteria, viruses, fungi and fungal-like pathogens or water molds, then the symptoms are characteristic of a disease. Some symptoms can be caused by abiotic factors such as a nutrient deficiency or toxicity, or an injury caused by the environment or crop protection material. In that case, the symptoms are considered to be a disorder. Nutrient imbalances can be caused by inadequate pH and soluble salt content in soil media and irrigation water. For more information, read the following Michigan State University Extension articles on diagnosing plant problems and nutrient mobility.

Plant health diagnosis takes an experienced diagnostician and a skilled sampler and submitter. Follow this checklist when collecting and submitting plant samples for health plant analysis at the MSU Diagnostic Services lab.

1. Sampling

Collect samples with symptoms representative of what you are seeing in the field.

Include pictures via email to pestid@msu.edu of the symptoms in the field. Quality pictures are needed. Avoid sending blurred pictures; use the macro option in your camera (tulip icon in most cameras and smart phone cameras). Attach the picture into an email and in the subject include submitter last name, crop and sample submission date. Example: Miller-pepper-6/20/13.

Collect several samples:

  • Look closely at symptoms and symptomatic plants. Select plants from areas where symptoms are starting, developing and developed. Avoid plants with advanced symptoms. A completely wilted or dead plant is not a good subject to submit.
  • Seedlings: whole plug trays, leave the plugs in the tray.
  • Whole plants: Collect three to 12, depending on size. Dig around the roots instead of pulling the plants. Shake most of the soil off the roots. Bag the roots and seal at the soil line with a twist tie or a rubber band. Use another bag for the aerial plant parts, but do not cut the root ball off the above-ground plant parts.
  • Fruit: Collect two to five, depending on size.

Use the submission form while sampling to take note of as much details as possible.

2. Submission forms

Provide as much information as possible in the spaces provided:

  • Information on cultural practices in the field prior to symptom development (soil, crop protection used, previous crop, herbicides used, etc.).
  • Any pattern observed in the field? Low spot or high spot? Prevalence?
  • Crop: plant stage, variety, parts affected etc.

Use the reverse side of the submission form to include additional information relevant to the samples.

In the diagnostic laboratory, the diagnosticians will put together all the pieces of the puzzle that you provided.

3. Packaging

Samples should be enclosed in boxes or other crush-proof packaging. Do not send samples in flat envelopes because in most cases the sample integrity is compromised during transit.

Do not include wet paper towel inside the bags with the sample. The additional moisture can result in rapid decay of the sample.

There is no need to add ice to the packages. Ice will either melt and leak or freeze the plant material that is in contact with it, rendering the sample useless.

4. Shipping

Send samples to the diagnostic lab with overnight or at least priority mail service. Never send samples on a Friday.

When possible, deliver the sample to the diagnostic lab directly. MSU Diagnostic Services is located at:

Center for Integrated Plant Systems Building
578 Wilson Road, Room 107
East Lansing, MI 48824

Do not assume your MSU Extension county office can mail samples; check with the office staff for specific instructions ahead of time. Your MSU Extension county office staff can provide you this checklist and the electronic address to obtain the submission form or a printed copy of the form. Most offices are not allowed to mail samples for you. All offices are not allowed to accept payment. An invoice will be sent to you with the results and instructions to pay for the service.

Communication with MSU Extension educators

MSU Extension educators are available to help you in this process and after you receive the results. Use the find an expert tool to find the appropriate educator in your area. Educators can guide sample collection and once you receive your results from the diagnostic lab, interpret the results and connect you with a campus specialist for recommendations to implement appropriate disease management tactics in your operation.

Extension educators with vegetable responsibilities are:

For additional guidance on submission of other crops to the diagnostic clinic, visit MSU Diagnostic Services sampling instruction page.

To learn how to submit insect specimens to MSU Diagnostic Services, see the article on tips on submitting insects for identification.

Tags: agriculture, msu extension, organic agriculture, pest management, vegetables


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