Timely diagnoses of crop problems have always been an important component of well-managed cropping systems. Early-season crop problems, in particular, demand timely diagnoses because crucial evidence often disappears by the end of the cropping season. As today's agriculture moves increasingly toward more site-specific crop management, timely crop diagnoses will become increasingly important also.
Purdue's Plant & Pest Diagnostic Laboratory (PPDL) offered up guidelines in the April 23 issue of the P&C Newsletter (http://www.entm.purdue.edu/Entomology/ext/targets/p&c/P&C99/P&C5.99.pdf) relative to the submission of samples to the laboratory for diagnosis by campus specialists. This week I offer additional suggestions from an agronomist's perspective relative to good field troubleshooting techniques.
Do your homework, preferably before the season begins. Take the time to
"bone up" on crop growth and development plus the common problems
that can occur early in the season. If you are aware of what could happen, you
won't be surprised when it does.
Good references include How a Corn Plant Develops (Sp. Rpt. 48, Iowa State Univ.), How a Soybean Plant Develops (Sp. Rpt. 53, Iowa State Univ.), Corn & Soybean Field Guide (ID-179, Purdue Univ.), Field Crops Pest Managment Manual (IPM-1, Purdue Univ.), Purdue's CD-ROM program: Corn Growth, Development and Diagnostics - Germination to Knee High (CD-AY-1), Modern Corn Production (Samuel R. Aldrich, Walter O. Scott, Robert G. Hoeft), and Modern Soybean Production (Walter O. Scott & Samuel R. Aldrich). The latter two books are out of print, but may be available via the Web at http://www.amazon.com, an online book store.
Also check out the following sites on the Web. These Web sites offer not only agronomic information from Purdue specialists, but also from other sites around the Midwest.
For timely information from around the Midwest, check out
Document thoroughly every operation and input applied to each field. Organize previous years' records, including custom application records, so that they are easily accessible when historical information is required for crop problem diagnoses. Lack of such documentation is often the most frustrating part of troubleshooting crop problems. Even the best troubleshooter can be stumped if the crucial piece to the puzzle is missing. Consider using the MAX software program, developed at Purdue University, for your crop record-keeping needs. The program (688 kb) can be downloaded from the Web at http://www.agry.purdue.edu/t2000/maxsoft.htm
Once you have done your homework and organized your records, there is no substitute for walking your fields and monitoring crop progress. Ideally, producers should do the walking themselves since they have the most vested interest in the outcome of the growing season. If you do not favor that form of exercise, then hire a crop scout that you trust will do a thorough job. Regardless of who actually does the walking, begin at the time of crop emergence and continue regularly throughout the early season.
As soon as possible after a crop problem is recognized, diagnose the cause(s). Diagnostic evidence often disappears quickly, especially with early season problems. Plant parts decompose, insects disappear, soil conditions change, damaged plant parts become masked by new growth, etc. If you cannot make the diagnosis, then bring in the "hired guns" as soon as possible to make their determinations. Potential "hired guns" include industry agronomists, industry technical representatives, private crop consultants, county Extension staff, and university Extension specialists. If you want to ensure unbiased diagnoses, then concentrate on the latter three categories of "hired guns". Lists of Purdue campus specialists can be found at ...
Don't hesitate to document the evidence and accompanying situations when you first recognize that a crop problem exists. Good tools for documenting symptoms include still cameras (instant, regular, or digital), video cameras, tape recorders and notepads. Remember to document not only the symptoms themselves,but the timing of their occurrence, their relative position in the field, the appearance/development of unaffected plants, the pattern of their occurrence, obvious presence and identity of insects, and any other factor that may be important to the diagnosis of the cause(s) of the problem. If you have access to GPS mapping technologies, use them to not only record the occurrence of the problem, but their actual position in the field.
If you intend on submitting samples to Purdue's Plant & Pest Diagnostic Laboratory (PPDL) for diagnosis, remember the guidelines suggested in the April 23 issue of the P&C Newsletter. As a reminder, the P&PDL can be contacted at 1155 LSPS, Purdue University, West Lafayette, IN 47907-1155; phone # 765-494-7071; Web site at http://www.ppdl.purdue.edu/ppdl/
Timely diagnoses of crop problems will facilitate timely development and implementation of any rescue or corrective treatments for the current crop. Additionally, timely and accurate diagnoses will help the producer develop management strategies for future cropping seasons to prevent or avoid the problem that occurred this year.
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