The Twenty Questions of Crop Diagnosis

Diagnostics is one of the most interesting and challenging aspects of crop production. Crop damage arises from any number of sources, and the symptoms are often remarkably similar.  Technologies such as digital cameras, text messages, twitter and email all help to make finding the problem (and a solution) quicker and easier.  However with these technologies, the background information about a field or a crop is not always readily available. This information is often a crucial step in making accurate decisions about the crop and its management.

Crop symptoms are the obvious place to start. The more information you can gather the better. Try to catch the symptoms early.  It is almost impossible to accurately diagnose a completely dead plant! Look at both the leaves and the roots in several different locations in the field.

When collecting samples for disease diagnosis, include as much plant material as you can.  If a fertility problem is suspected, take soil and tissue samples from both the problem and unaffected areas of the field.  Unless otherwise specified, keep samples in the fridge or a cool location until they can be delivered to an agronomist or a laboratory.

Use the following list to help narrow down problem areas in your crop.  When talking to an agronomist, be sure to provide him/her with as much of this information as possible.

Symptoms:

1. What are the symptoms?  (yellowing, wilting, spots, insects, lodging, failure to emerge?)
2. When did they first appear?
3. Where do they occur on the plant (upper leaves, lower leaves, roots, stem?)
4. Where do they occur in the field (is there a pattern to the damage or is it randomly scattered?  Is it wide spread, or in an isolated section?)

Chemicals:

5. What has been applied to the field and when? This includes historical spray data for the previous 2-3 years.
6. Were tank-mixes or other tank additives used and are they compatible?
7. What were the weather conditions at the time of application?
8. What fertilizer products have been use and what was the rate and placement?

Sprayer:

9. When was the sprayer last calibrated and nozzles replaced?
10. When was the last thorough cleaning?  What chemicals have been used since then?

Seed:

11. Was it from a reliable, certified source?  How old was it?
12. What is the variety?  Are there any specific varietal susceptibilities or tolerances?
13. Was the seed treated?  With what?

Planting:

14. What were the weather conditions at the time of planting?
15. What was the planting depth?

Soil:

16. What are the soil test levels (including macro and micro nutrients)?
17. What is the pH?  Is this level compatible with any chemicals applied?
18. What is the soil texture and organic matter level?  Are these compatible with chemicals applied?
19. Does the soil structure or moisture differ in the affected areas? Is there a hard pan limiting root growth, water movement and aeration?

Environmental:

20. Any unfavorable weather conditions? (excessive heat, cold, dryness, wetness, winds, ozone/air pollution?)