Category: Cooperative Extension
How to Save Money on Field Crops This Year
March 06, 2025 Written by: David Owens, Agricultural Entomology Extension Specialist. Photos by: Jackie Czachorowski
I’m sure many of us are more than happy to close the 2024 season and pray for more timely rains in 2025. This year, margins are looking to be just as, if not tighter, than last year. Over the last couple of months, talking with many farmers and sending and receiving insect pest loss surveys, I think I can find ways to save a little bit of money in 2025. What I propose below is not going to make or break an operation. You might even be tempted to scoff at some of it. After all, what I propose may only add up to a nice dinner date or a small trip, but it’s important to save where we can.
Soybeans
Going across a soybean field? Take a couple of minutes before mixing and loading the sprayer to look at it. My 2024 soybean pest loss survey suggests that the average field on the Delmarva peninsula received 1.4 insecticide applications. Insects of concern last season included corn earworm, stink bugs, seedcorn maggot, spider mites, and slugs (though not technically insects). However, half of these applications to the average field were ‘automatic’, ‘prophylactic’, or ‘insurance’ applications. The most common insecticide tank mixed with a herbicide or a fungicide is lambda-cyhalothrin, which costs roughly $1.50 - $2.25 per acre. While it does a decent job on green stink bug, it does not control corn earworm. Early in the vegetative stages, soybeans can take a real beating without suffering a yield hit. We have had fields lose almost half of their intended stand and still yield fine. Instances of significant insect pest activity at the time a post-emergence herbicide application is typically applied are very rare. This is one application that can be skipped.
Are the beans flowering? Tank mixing lambda-cyhalothrin or bifenthrin (roughly $6.00) with a fungicide is a bit more of a judgment call, and you should spend a few minutes scouting the field first. If a field averages 3 + stink bugs, it's probably justified to add it, but if not, save your spray! Pyrethroids do a poor job on corn earworm and have limited residual activity. They also are good at killing pollinators. Recent research suggests upwards of 10% of our soybean yield is due to insect pollination. Don’t shoot yourself in the foot!
Corn
But what about corn? This one is even worse. Survey responses that came back suggest that almost ¾ of the corn crop receives a fungicide tank mixed with an insecticide. Now, this seems a bit high to me (and I hope it is), but if it seems high to you, please fill out my corn pest loss survey at the end of the 2025 season. Let’s say, for argument’s sake, that it is high and should be closer to 40%. The fungicide application typically goes out around silking. This is TOO late to reap the full benefit of an insecticide application targeting brown stink bug. If brown stink bugs are going to cause problems, they really need to be hit just before tassel push. About a third of folks are using lambda-cyhalothrin, which does a modest job at best of controlling brown stink bug. So not only are we using inappropriate chemistry, but we are also going out too late.
Still, worried that leaving it out of the sprayer is a bad idea? Walk into the field, about 5 rows and look at the stems of 100 corn plants where the ear is emerging. Is it silking yet? How many stink bugs did you see? If you saw nearly 28 in silking corn, go in another 10 rows. You probably won't see them anywhere near that number.
What about an early spray going after stink bugs only at V14/ VT? Your target is 10. That’s a big difference. By not scouting and tank mixing with a fungicide, we are either 1. Letting stink bugs damage the crop, or 2. Wasting money on poorly timed sprays and even with improper pyrethroid selection. The only caveat is the Japanese beetle. Last year, there were fewer of them, but in the literature, they’ve been the cause of some pollination troubles. You would need a bunch of them before pollination and significant silk clipping. It might happen in small spots in the field, but I think it is less likely. Again, get out and look at the edge of the field, then go in a few rows, and then a few more rows.
Why is brown stink bug harder to control with pyrethroids? Some entomologists think it's because of wheat. Brown stink bugs use wheat as an early nursery crop (they are not a pest of wheat). It’s been common practice to tank mix a pyrethroid with a fungicide in the spring. Last year, cereal leaf beetle and fall armyworm were nearly non-existent. This timing is too late to be of much benefit from an aphid control standpoint if aphids were to be over-abundant, which they weren’t last year. But now we've given brown stink bugs a dose and selected those that survive the insecticide. By and large, we don’t need this application. My lab runs armyworm traps each spring in 6-8 locations across the state to give you a heads-up if any of our thinking changes.
Watermelon
The final crop I want to discuss is watermelon. We have evidence that pyrethroids used for striped cucumber beetle may have reduced benefits. Recent bioassays, observations, and spray trials suggest that beetles are moving away from treated foliage until residue breaks down, but relatively few beetles are dying from the spray. Some great work in Indiana shows that these insecticides also reduce pollinator visits to flowers and result in less fruit set and yield.
Are pyrethroids cheap? Yes. But even a few bucks an acre over an operation adds up to a tidy sum. And with prices where they are at that tidy sum is sure better than nothing. And your bees, butterflies, lady beetles, and pirate bugs will also thank you by pollinating more flowers and eating more small pests. And before you think I’m an insect-hugger at heart, I do get inspired and love my job whenever I walk into my pesticide storage room when there’s a ‘glorious’ pest population that we need product efficacy data for. Saving bugs, killing bugs, saving money. That’s what extension entomologists try to do for you.