Scouting

There are many ways to tell if you have a problem in your soybeans. By far the best way to tell if you have a problem is scouting the field. I recommend that you set up a scouting schedule for your soybean fields. You should make it routine to visit each field at least once a month during the growing season. During these visits you should take a quick walk through the field and look for symptoms of problems. Some of the symptoms that you should look for are:

• Stunted growth of plants
• Discoloration of leaves
• Spots or holes on leaf or stem
• Slow seedling emergence
• Lack of seedling emergence

Once you have completed scouting the field you must establish what is causing the problems that you have found. Sometimes this can be the difficult part of the process. Many times the symptoms of a disease are very similar to those of nutrient deficiency so you must distinguish between the two. Most diseases symptoms will occur during specific growth stages. To distinguish what disease is causing the problem you must note what the symptom is as well as the growth stage that the symptom observed.

For help with soybean growth stages visit the University of Minnesota or Purdue University.

When you are in the field scouting you will notice that there are many things going on. The primary things that you should be looking for that would indicate a disease problem are listed bellow. This list is not all inclusive but it outlines the major things that you should be looking for. If you see any of these symptoms you will know with reasonable certainty that you have a disease problem.

• Small angular water soaked spots on leaves
• Large blighted areas that might drop off giving a tattered appearance
• Irregular light-brown lesions on leaves, stems, petioles and pods
• Black specks in rows on dead stems and poorly-developed pods
• Pale green to yellow spots on upper leaf surface
• Chlorosis and wilting of leaves
• Dark brown discoloration on lower stem
• Seed rot and pre-emergence damping-off
• Damping-off of post-emergence seedlings
• Reddish brown lesions on larger seedlings and young plants at the soil line and taproot
• Wilting and death of plant with dead leaves that remain attached to stems
• Tan and whit lesions at nodes
• Sudden discoloration of leaves
• Brown tissue between vains with green tissue along leaf vains
• Browning of pith inside stem
• Light brown to gray discoloration in internal taproot tissue
• Slow to close canopy
• Root decay
• Cysts on roots
• Curved stem terminal
• Lateral buds browned and dropping off
• Deformed leaves
• Stunting, mottling and curling of leaves
• Stunted and Curved pods
• discolored seeds in pods

As you can see many of the symptoms can be seen just by looking at the plant however when you see a something that looks suspicious I suggest that you dig up a few plants and look at the roots. Sometimes it is even necessary to cut the stem and root in half to see how the pith and inter root look. If they are discolored that is a good indication that the plant is diseased.