With harvest starting on some early maturing varieties, soybean yields are on a lot of growers’ minds. This year Illinois experienced a large feeding frenzy by Bean Leaf Beetle in many areas that called for late application of insecticide, but what else could explain loss in yield? Apart from June planted beans, little can be done at this point to help retain yield, but there are a few things to scout for in order to help explain some problem areas that you might encounter this fall or possibly next year.
  1. Insects & diseases
  2. Final stand counts
  3. Stressed areas
Soybean scouting calendar

1. Insects and diseases: You might be wondering what happened to your almost perfect bean crop when the combine tells a different story than what you heard all year long. Once a soybean crop passes the R6 growth stage spraying for bugs or disease is impractical, but scouting can still tell us a lot. Scouting can show why yield might have been lost from defoliation (20% threshold) or pod damage (5% threshold) and why a field maybe should have been sprayed.

Any defoliation to soybeans can hurt yield, but during reproductive stages it is more critical than ever. Pests we cannot see, like Soybean Cyst Nematode (SCN), can slow crop growth in vegetative stages and stunt the plant, overall producing fewer pods and seeds per pod. If something seems off, a soil SCN test should be done for that field. Outside of physical damage to leaf and vascular tissue, most diseases will overwinter in debris and come back next year.
Making a preharvest scouting trip can give you a heads up for next season. Some diseases you cannot see from the road its important to look in the lower canopy or split stems open to observe damage. Scouting for disease will also help evaluate standability, which fields to harvest first. The big picture when it comes to late season scouting is just to get out there and see what you have before the busy harvest season hits and you don’t have time to evaluate a field.
2. Final stand counts: Lots of early season problems led to lower stand counts that didn’t quite reach levels that called for replant. This creates a couple of opportunities for growers to find out ROI at the populations they are not used to planting. Soybeans have the awesome ability to adapt and react to stresses by branching and adding flowers/pods when conditions are favorable. So, establishing a real final stand vs. what the planter read might give some insight and help give some comfort when deciding to lower the soybean seed population next year.
Satellite imagery showing low,
medium, and high vegetation

3. Stressed areas: Most growers know their fields very well, but in the past couple years I have heard many say that their worst fields did better than their best. Satellite imagery cannot tell what is wrong with parts of a field, but it can show you that there is something wrong in general. This is a great resource to save you time scouting and give you a starting point. It is also a reminder of saturated pockets of the field from springtime floods or weedy spots, that can help explain why a yield map may be disappointing. Outside of satellite imagery, drone images can show a lot from angles beyond our reach. Many times patterns show up we cannot see from ground level, which help piece a puzzle back together. Technology is a great tool that should not be overlooked. Most platforms are getting simpler and easier to use and are a great resource for all types of operations.

In most situations, a lot of the problems we face year to year are out of our control. Disease and insect pressure fluctuate with temperature and humidity, emergence is dependent on rain received in the spring, and stressed areas are the result of several of these things combined. Preventative measures and scouting are some of the best procedures to combat what Mother Nature throws at us and avoid future problems.

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About the Author: Cody Pettit

Currently, Pettit is a field agronomist for the Pioneer brand with Corteva Agriscience, covering the east central part of Illinois. Prior to his current role, he was a district sales manager in the seed industry after graduating from the University of Illinois, where he earned a bachelor’s degree in crop sciences. Pettit has a passion for understanding new practices and solutions employed on a variety of farm operations, and is excited for the ever changing future of the agricultural industry.