Over-informed on IPM - Episode 026: Integrating Chemical and Behavioral Control of BMSB (part 3)

We’re returning to BMSB management in this episode so, if you haven’t already listened to part one on whether or not we should be freaking out, or part two on predicting outbreaks, you should listen back before you join us on this one. 

All right so, I’ve heard some rumors that you can’t control BMSB with chemical insecticides. And that’s totally false. You can totally control BMSB with chemical insecticides. It’s just really hard to control BMSB with chemical insecticides. There’s many reasons and they’re all a real kick in the pants.

First of all, the feeding injury caused by stink bug feeding takes a little while to show up in fruit. They stick their proboscis in there and spit in enzymes and suck out all the good stuff. The corking and depressions that ruin the fruit can take weeks to show up, sometimes this happens when fruit is sitting in storage. That’s bad.

Good news is that up here in the northeast, BMSB populations surge pretty late in the season. We didn’t see peak numbers until the middle of September last year, so late maturing varieties are really the only ones that saw a lot of action. However, the materials that are the most effective for BMSB also have the longest pre-harvest intervals. So you’re looking at that window 2-3 weeks ahead of harvest to see if BMSB is moving in. During those couple of weeks before harvest, you’re limited in terms of effective materials with appropriate PHIs. That’s bad.

More bad news is that, even if they do move in to the orchard during a period of time that you can knock them back, there’s probably another wave in the bordering woods that are about to move in after that residual efficacy has worn off. Again, you’re stuck with those meh materials with short PHIs. That’s bad.

Also, truth be told, these are big bugs with lots of fat body (think insect livers) with a pretty remarkable ability to detoxify common insecticides. I don’t like to admit this - it’s rare, but from time to time - a bug who looks like they’ve been killed by a broad-spectrum neurotoxin, actually recovers and walks away. That’s not good. Just another lesson that spray coverage is important and don’t mess around with moderate label rates for these bugs.

That being said, we’re talking about pesticides in this one so I have to remind you the label is the law. Read your labels.

But I talked to few experts in this area about using pesticides to control BMSB in vegetable crops and in fruit crops and how we can integrate chemical and behavioral controls to avoid crop injury. It’s not all bad news.

Tom Kuhar, Virginia Tech

You know we have some of the highest populations here in Virginia. They have been since the bug was established. We had a crisis in 2009 and 2010. We just weren’t ready for this pest. I think tree fruit was hit hardest. It is a tree-loving bug. But it definitely attacks fruiting vegetables. There’s no doubt.

A lot of conventional vegetables were already being sprayed with pesticides that are efficacious on stink bugs. Pyrethroids are cheap. There going in there to protect those fruit from a lot of things. Pyrethroids can help clean up a lot of pests. So because of that, I think tomatoes weren’t hit as hard. Same thing with sweet corn. Peppers maybe don’t conventionally get those pyrethroid sprays so they may have suffered some damage that was out of the ordinary. Because pyrethoids are cheap the answer was easy. Now, you could flair secondary pests like green peach aphid. They can take off, now you have to deal with the aphids. You’ve shot yourself in the foot.

But the biggest problem is organic farms. There are very few tools that work well when the pressure is high. Another thing about organic farms is that they tend to be smaller, on a patch of land surrounded by woods. Its just the perfect recipe for stink bug problems. So those are the instances where I think the damage has been the highest.

I will say that we had a student work on organic insecticides. None of the popular organic insecticides work, at least not in the field.  We could get some good control in the lab but, when we took it to the field, none of these control pressure that was high. Kaolin clay, in the product Surround, it’s basically a mined silicate clay, this bug hates it. And its got some advantages for fruiting vegetables. It protects against sun scald. It’s got a few other benefits. It’s something growers were using already. We got very good control when we sprayed Surround on peppers, tomatoes. Among the organic options, that was the best.

Anna: All right! So some good news there. Stink bugs hate kaolin clay. It makes them so unhappy they leave peppers alone. But back to tree fruit and this tree-loving bug. What do we do there? What do we do during that period right before harvest when we’re too close for missiles? What guns can we switch to? Peter Jentsch has been playing around with some biorationals.

Peter: So this is not an IPM conducive insect. Bottom line. Tough pill to swallow. The bifenthrin, that’s the material you should use if you want to kill them. But the down side – originally we were looking for 4 day-to-harvest materials. So here you are, you’ve put your bifenthrin out and its working really well and you’ve got 10 days till harvest. All of a sudden at 4 days till harvest, you start seeing the population build and you are done. You’re done spraying. You’re just crossing your fingers and praying. That’s when a lot of the injury occurs.

So the idea with Venerate, you put this stuff on. Maybe in multiple applications. You’ve got zero days-to-harvest. That’s the material to go to when all else fails. Assail is out. All the other 7 day materials, you can’t use.

Anna: If you look at the company website, the product Peter mentions Venerate XC is bioinsecticide, Burkholderia spp. strain A396, that features multiple modes of action, effective against a wide variety of chewing and sucking insects and mites. Truth be told, this material is not good at killing insects. But there’s more than one way to avoid injury in IPM. Back to Peter.

Peter: As we’ve moved through iterations of these field efficacy studies, as well as the laboratory bioassays, it’s been really interesting to see these new chemistries. One of them is this Marrone Bio product called Venerate. The reason I picked up on this one is there was some talk about this being an organic option. I think Anne Nielsen may have brought this to the lime light. She didn’t follow up with it but she mentioned that she may have seen some reduced feeding injury on the fruit.

So we followed up and looked at Closer, a Dow product, Venerate, Bifenture, and an untreated control. We sprayed the trees, waited 24 hours, then placed bugs onto treated fruit in a cup – kind of a screened cage with a rubber band. It was about the most fun I’ve had since kindergarten.

We also circled the arena with a sharpie, of course. Fourteen days after we removed the insect, we brought the fruit back to the lab. Then we skinned all the fruit. We looked at the surface of the fruit for depressions and discolorations. Those were two categories. Then we had the category of corking underneath the arena. All of that to say, the Venerate provided us with as good if not better control than any other product.

Anna: More good news? Peter also mentioned that topical application directly to these bugs also resulted in reduced feeding so not a straight forward feeding deterrent like the kaolin clay but something I really look forward to hearing more about!

How about some more good news? How about an IPM resuscitation in New Jersey?

Anne Nielsen, Rutgers University

Anne: IPM CPR is a tactic that we’ve been developing in my lab since 2012. We first did this in peaches and we’ve also done this in apple.

So IPM CPR stands for integrated pest management crop perimeter restructuring. And we came up with that because we were trying to resuscitate our IPM programs but we’re doing it through a behaviorally based approach. And we’re, it is an IPM tactic because we’re integrating multiple pests into this. So we’re trying to bring back IPM tactics that growers dropped after BMSB invaded. Because when BMSB invaded, the only management tool that was available were broad spectrum insecticides. And unfortunately because that was the only tool, and because of the long period of time that BMSB is present in the orchards, our insecticide use went up fourfold. And it caused some downstream effects. One of those was that our growers who were using the behaviorally based management tactic, mating disruption, for our internal worms, they stopped that tactic because the number of sprays that are needed for BMSB were at least they thought, were controlling these other pests. They dropped just timing of insecticides because BMSB constantly available. So they dropped a lot of key IPM tactics, but what we knew about BMSB at least in peaches is that they come in form the edge of the orchards. So they actually stop at the orchard edge and stay there for about a week before they move inside. 

So we wanted to exploit that behavior, that perimeter driven behavior. And so we started off by doing border sprays which is where is when you just spray the edges of the orchard, not the surrounding trees, just the peaches themselves. And that’s about 25% of a 5 acre orchard, which is a good sized normal block. And we did that on a weekly basis, so we’re still are on our weekly sprays . But we did initiate the sprays based on the degree day model that I developed, so we weren’t spraying immediately post bloom. We were spraying a couple of weeks after that when we knew BMSB was starting to come into the orchard. So we’re basing this approach based off of multiple things. And we were also looking at, we also reintegrated mating disruption into our orchards for our moth pests.

So what we found was that we were spraying significantly less insecticide, our moth pests were being managed by the mating disruption, and we were seeing equal or sometimes less stinkbug injury in our peaches. And that’s really exciting because again, we’re using 25% less insecticide. And we didn’t, the data for natural enemies in terms of whether or not we’re seeing more natural enemies just in overall abundance, the diversity of our natural enemies, or their impact is a little variable. In some years we see higher impacts, some years we see higher diversity, but the one interesting thing we have seen is that we’ve been able to identify the egg parasitoid of brown marmorated stink bug, which is its primary mortality agent naturally. We’ve been able to identify that in commercial orchards that are using this technique. So we think it’s compatible with these border sprays. We’ve also done the same thing in apples, integrating the threshold with border sprays and we’re seeing similar results. 

Anna: Oh that’s awesome that you’re seeing the parasitoid. That leads into my next question – obviously there’s this benefit of saving natural enemies by spraying less. Where do you see that going?

Anne: So two things: The next steps for our IPM CPR program are to get away from the weekly border sprays. So we can start integrating in predictive models so that we can just target BMSB when they’re actively migrating into the orchards. That’s a key step in order to further reduce insecticide use. In terms of your question about biological control, right now they’re, we’re only seeing about 1% control or mortality due to our natural enemies. With the sentinel egg masses due to the parasitoid. Overall we know that about 14% probably of BMSB are controlled by generalist predators. So the numbers are still pretty low and that’s based off of gut content analysis, but numbers are low. I think that if we can, I think that IPM CPR is compatible with biological control; however, our parasitoids also likely come in from the edges too. So one thing that we’re going to start looking at, my lab, is whether or not we can use insectary strips, or flowering plants, to help sustain the parasitoids, provide an alternative food source and a refuge for them. And then they can move on and kill all of the stink bug eggs in the orchard. 

Anna: Holy macaroni. Did you hear Anne mention that New Jersey tree fruit needs to be protected from BMSB when it moves into the orchard after petal fall! Yeeesh. At least we don’t have to worry about pest pressure that high up here in the northeast… and aren’t we lucky that there’s this army of entomologists to the south of us who have figured out what we need to do if we do get into hot water!

That’s a good place to stop for now as I hope you will join us for part of 4 on biological control of BMSB next time. Thanks to Tom Kuhar (of Virginia Tech), Peter Jentsch (at NY’s Hudson Valley Laboratory), and Anne Nielson (of Rutgers University). And of course, special thanks to Jason Lightbown who wrote and performed our theme music.