What Japanese Beetles are doing to your soybeans and how to stop them

Japanese Beetles are once again a threat to our soybean fields.  They have been significant vermin in all our fields every season in recent memory and this year seems to be no different. In an earlier article, we discussed where they come from and why they are so prevalent in our neck of the woods, which you can read here. To sum it up, Japanese Beetles are an invasive species that have forced our way into our ecosystem. Without any natural predators, they have been able to reproduce exponentially and wreak havoc on farms across the Midwest.  This article will focus on what these beasts from the east are doing to your beans and how to stop them. We will also cover some other notable pests that are often found in soybean fields in Missouri.

Damage to the foliage

The most noticeable way that Japanese Beetles affect our soybeans is by munching on the foliage (leaves). A trademark visual sign of Japanese Beetles is the mesh look of the leaf being eaten down to the “skeleton” of the leaf. This is not only unpleasant to the eye but can be quite detrimental to the health of your soybean plants. Soybean leaves are very important when it comes to feeding the plant. Without that green surface area on the leaves, sufficient sunlight cannot be captured for soybeans to create chlorophyll, which is essential to making food for the plant. This means that the more leaves that are eaten through, the less food that the soybean plant can make for itself. If the soybean plant cannot make enough food, then it will abandon blooms and pods, and therefore yield potential. Losing leaves can definitely cause yield loss, so it should not be taken lightly.

Damage to blooms and pods

While damage to the blooms and pods is not the first thing you notice Japanese Beetles eating, they are the most vital. If these pests go after soybean blooms and pods, then they are directly attacking the part of the plant that produces the fruit, which directly decreases your yield. In that sense, Japanese Beetles are literally going after your money-maker. The truly unfortunate part of this is that the soybean pods are the meal of choice to these varmints. That’s why it is very common to see Japanese Beetles make their way from the top of the plant to the canopy when soybeans move into their reproductive stages.

How do we stop them?

There is only one effective solution to get Japanese Beetles out of our fields and that is to use insecticide. Insecticide, if used properly, can be the difference between an infestation and a brief hiccup.  There are two types of insecticide you can use on soybeans that I will simply refer to as “contact-killing insecticides” and “residual insecticides”.  Contact-killing insecticides, such as Warrior II, will kill insects as soon as it touches them if enough product reaches them. Residual insecticides, such as Endigo ZC, are designed to be absorbed by the plant and be effective for an extended period of time.

Contact-Killing Insecticides

Using a contact-killing insecticide has some clear disadvantages to residual insecticides here. Most obviously, contact killers generally don’t have a long period of effect. They usually knock insects out of the field for a few days to a week. This can be sufficient depending on the spray timing and season, but you may run into problems if your soybeans’ reproductive period lasts longer than you expected. This often happens if you get periodic and advantageous rains during the season and your soybeans keep adding new growth and potential to produce more beans. This is generally a good thing as it raises your yield potential, but it also makes a band-aid solution like a contact-killing insecticide insufficient to keep the bugs out.

Residual Insecticides

This is where residual insecticides can close the gap. Residual insecticides are absorbed by the plant and will kill insects that eat a small amount of it. This provides a solution that does truly kill the pests that dare take a bite out of your profit. These residual insecticides last in the plant until the plant grows large enough that the insecticide is dispersed throughout the plant at a non-lethal dose. This generally buys you 2-3 weeks and is more likely to get you through the crucial reproductive stages of your beans when they are at their most vulnerable.

Other Notable Insects

There are other notable insects that should be monitored in soybeans. One of the first that you’ll notice are Bean Leaf Beetles. These beetles, as their name suggests, are foliage-feeders and can eat through enough leaves to impact your yield in severe cases. Another big player is the infamous grasshopper. These guys generally start hitting their peak activity as Japanese Beetles hit their decline in early to mid-August. Grasshoppers are not nearly as numerous as Japanese Beetles, but they do a lot more damage per insect. Grasshoppers have a strong appetite, and one small grasshopper can easily and quickly devour a pod by itself. Fortunately, all of these insects can be dealt with in the same manner as Japanese Beetles.

Conclusion

While Japanese Beetles in soybeans are an annoyance, they are a manageable annoyance. With guidance and the right product, you can be rid of these pests at the time when it matters most and ensure your yield is not affected by them.

If you wish to talk to a professional regarding an insect problem in your soybeans and want further insight on how to deal with them, Service and Supply Cooperative has the expertise and tools to give you what you need.  Our dedicated staff has years of experience dealing with these cretins and can guide you towards a strong plan of protection against them.

If you wish to get in touch with us at Service and Supply to seek help or get on the fungicide/insecticide list for soybeans, please use one of the contact links below and we will make sure you get the best service and products possible for your situation. Also, ask us about the different application methods available for insecticide and fungicide application.