Should I apply a fungicide?
 

• Doing on-farm trials with fungicide applications is one way to determine if fungicides are providing a yield benefit that pays for the application. Iowa State University research farm agricultural specialists are available to help set up and analyze results from on-farm strip trials.
  
  The Iowa Soybean Association also has a large database of on-farm research trials and further information on setting up your own on-farm strip trials. 
  • For example, in their 505 on-farm trials for fungicide in soybean in the state of Iowa since 2005, the average yield response across all trials was 1.9 bu/ac.
  • In their 537 on-farm trials for fungicide in corn in the state of Iowa since 2006, the average yield response across all trials was 3.3 bu/acre. 
     
• Unlike insect pests were we have more clear cut economic thresholds on when it pays to spray an insecticide or not, we don't quite have that for diseases. Instead, we need to consider if the pathogen is present, the crop suspectability, and if we have favorable environmental conditions for disease development. The University of Illinois recently published this blog post titled "Tips to help you make fungicide decisions" that does a nice job discussing factors to consider when deciding whether to spray a fungicide or not. 
   
• Take time to scout and see what diseases, if any are present; where they are located at in the crop canopy; consider the hybrid and/or variety susceptibility; and look at the weather outlook to help determine if a fungicide application is warranted. 

Insects out in field crops

Insects are out in field crops again this year and the only way to know if treatment is necessary is to scout!

Japanese Beetles: Keep your eyes open for Japanese beetles as they are starting to appear in corn and soybean fields. With these insect pests, leaf feeding on soybean and corn silk clipping (before pollination) are of concern.
 

Adult Japanese Beetles are metallic bronze and green with white tufts around the side of their abdomen. 
 
ISU Extension Entomologist, Erin Hodgson has a good article on Japanese beetle thresholds and management in corn and soybean, which can be found here. Be careful not to confuse Japanese Beetles with another similar looking beetle called a chafer. 

Bean leaf beetles: The first of the first generation bean leaf beetles will soon be emerging and showing up in soybean fields again. The next generation (2nd) will likely be of most concern for potential feeding in soybean fields, but those emerging in July can be monitored to give us an indication of what to expect for late August and September. Here's a good resource from 2016 on scouting for these pests.

Potato Leafhoppers: For those with alfalfa, don't forget to continue to keep scouting for Potato Leafhopper. The dry conditions can often magnify feeding injury from potato leafhoppers. Here's a good resource for scouting and managing for potato leafhoppers. 

Herbicide drift in soybeans

I'm just starting to get the first phone calls on suspected herbicide drift (dicamba) in soybeans. Thankfully, most cases I've investigated so far have not been from drift onto soybeans but rather "cases of mistaken identity." The University of Wisconsin has developed a nice fact sheet on identifying dicamba injury that you can find here.

Common symptomology known as "cupping" associated with dicamba physical drift, volatility, misapplication, or tank contamination. These show several different ways the injury may present from typical upward cupping, to a crinkle and strapped appearance, to a much slighter puckering/cupping of the leaf. This injury is usually symmetric on leaves (all three leaflets affected similarly).


Common symptomology from POST applications of HG 15 products applied to soybean fields (Warrant, Outlook, Dual, etc.). We often refer to this as "drawstringing" as it looks like the leaf veins at the tips of the leaves stop developing or even appeared pulled back toward the center of the leaf (heart-shaped). This is often not perfectly symmetric.


If you believe you have herbicide drift on your crops, please do not hesitate to call me to discuss the issue. If you need someone to document evidence for a possible settlement, consider hiring a professional agronomist (crop consultant, certified crop advisor, or other well trained agronomist). ISU Extension is in the business of education, but we do not assess entire field situations or get involved with settlements (we are not available as hired expert witnesses). Practical Farmers of Iowa has a really nice pamphlet regarding how to prevent drift and steps to take if you suspect your property or crops have been drifted on.

You can also reach out to the Iowa Department of Agriculture and Land Stewardship Pesticide Bureau at 515-281-8591 to report the drift. The pesticide bureau has a group of employees who investigate drift and their website has several helpful resources for those who are interested, including FAQ about pesticide drift, information about enforcement and investigations, and a list of private labs who do pesticide residue testing in Iowa. 

Another thing to be aware of is that while the Pesticide Bureau can test for herbicide in plant material or you can send in material yourself for testing, dicamba is often no longer detectable in plants within a few weeks after application. So not detecting the chemical during an investigation does not mean that there was no drift. Be sure to document physical signs of problems as soon as possible after an event is noticed. Do the same with agreements between both parties as to where yield checks in fall should be made; and if drift was on home gardens, consider all produce to no longer be viable for those crops not labeled for a dicamba application.

In the end, communication is key to both preventing and resolving issues, so be a good neighbor and don't be afraid of having the discussion about pesticide applications or potential drift to resolve issues quickly.