Insect Field Scouting - September 2013
Insect Field Scouting – September 11, 2013
[Gus Lorenz, Extension Entomologist. Field Scouting, September 11, 2013. U of A University of Arkansas Division of Agriculture Research and Extension University of Arkansas System, Arkansas Soybean Promotion Board. Video shows Gus Lorenz standing in a soybean field.]
Hi, I’m Gus Lorenz Extension Entomologist with the University of Arkansas. What you see behind me is a soybean field. You know, it’s mid-September, it’s that time of year. We have a late crop this year of soybeans and what goes along with a late crop is obviously are insects. And, we have a lot of pressure in this field today.
This is actually outside Marianna at the Lon Mann Cotton Branch Experiment Station in some of my plots. But I want to show you some of the damage and some of the things we’re seeing out here right now.
[Video shows 2 people using a sweepnet to check for insects in the soybean field.]
So what we got going on in this field, there is several things. [Video shows insects collected in the net.] You can see the immature brown stink bug nymph, and it’s distinctive from the green stink bug that you see beside it here. And then here is the brown stink bug adult between my thumb and my forefinger, just to show you the different stages we have out here right now. [Video shows Lorenz showing the different types of stink bugs captured, the brown stink bug nymph, adult and a green stink bug.]
And here’s what is causing the defoliation that we’ve been looking at. That’s called the bean leaf beetle. And it’s characterized by it may or may not have those spots on the back, but they all have the little triangle behind the neck. Here is a red one with no spots on it, but again it still has the black triangle right behind the neck. So they come in several different colors. [Video shows Lorenz showing two different types of bean leaf beetles captured in the net.]
We not only have bean leaf beetles and stink bugs; but we also have soybean loopers coming in the field. The Soybean looper is characterized by the two pairs of prolegs. Loopers are the only species that have two pair of prolegs. [Video shows Lorenz showing soybean loopers captured in the net.]
[Slide – Bean Leaf Beetle. Pictures of bean leaf beetles.]
Bean leaf beetles will often times cause extensive defoliation in the upper part of the plant, but what you need to look at is not just the top part of the plant, but you need to look down through the canopy and look at the level of defoliation across here. [Lorenz shows soybean plants with various levels of defoliation in soybean plant leaves.] When I look at this leaf here in particular. Our threshold is 25 to 30% defoliation, and what I see here, we have exceeded that threshold. But, on this leaf right here you know we are only at about 10%. So when you are looking at defoliation and trying to make a decision on whether or not you’ve reached that threshold of 25% defoliation you need to look at the entire plant and not just that part up in the top.
[Slide – Soybean Loopers. Picture of a soybean looper.]
The thing about loopers is they are just the opposite of bean leaf beetles. They like to start down in the lower part of the canopy on the older tougher leaves and then they work their way up into the new growth. So, you have loopers working their way up from the bottom, and bean leaf beetles coming in from the top.
[Slide – Stink Bugs. Picture of a stink bug.]
The thing is, if we come in and treat these stink bugs with a parathyroid to get them under control, what it actually does is destroy the beneficial complex, kills all the parasites and predators, and opens the door then for the loopers to blow-up.
[Slide – Recommendations. Pictures of a stink bug, a bean leaf beetle, and a soybean looper.]
[Gus Lorenz, Extension Entomologist. U of A University of Arkansas Division of Agriculture Research and Extension University of Arkansas System, Arkansas Soybean Promotion Board. Video shows Gus Lorenz standing in a soybean field.]
So, what you have seen out here today is a combination of pests. And in that situation at this time of year it’s going to take more than one insecticide to clean up this mess out here. [Video shows sprayers being hooked up to equipment.]
In the case of the stink bugs and the bean leaf beetles, you know probably a product of choice might be for those two would be Bifenthrin, which a trade name would be like Brigade®, Fanfare®, Discipline®, Sniper®, there is several different brands. At a rate of somewhere around a gallon per 25 to 30, or something like that, just to get those under control. But, as I mentioned earlier, if you spray a parathyroid out here the chances of you blowing that looper complex up, the loopers that are out here is pretty great, because you are also wiping out your beneficial complex. [Slide – Recommendations for stink bugs and bean leaf beetles – Bifenthrin.]
So in that case, you have a few options for products on loopers that you would tank-mix with that Bifenthrin. Prevathon®, Besiege®, Belt®. Another that might be a little cheaper alternative would be Intrepid®. So, those are the products that have proven to be very effective for loopers. [Slide – Recommendations for loopers – Prevathon®, Besiege®, Belt®, Intrepid®.]
So you’ve got to tank-mix with one of those. And for that situation it’s a pretty expensive treatment when we get into trying to control more than one pest species. And there is not just one product that gives good control. [Video shows field being sprayed for pests.]