Over-informed on IPM - Episode 024: Predicting BMSB Outbreaks

If 2020 wasn’t bad enough already, the stars seem to be aligning for New Hampshire’s first brown marmorated stink bug (BMSB) outbreak in fall-harvested fruit crops. Anna takes a break from stopping people on the street to warn them and talks to some BMSB experts in this multi-part series on monitoring and control of this invasive stinker.
Brown Marmorated Stink Bug

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More information: stopBMSB.org

The best way to trap stink bugs in your house

 

Transcript

Hey there! We’re thinking a whole lot about brown marmorated stink bug here in New England these days. For those of you who live in areas hit hard by brown marmorated stink bug, it might sound quaint that we are just starting to see agricultural problems with this invasive pest insect in the northeast. Luckily for us, there has been an army of entomologists and crop protection specialists working out the details of how to protect our crops from these invasive insect. I’ve chatted with a whole bunch of them and I’m geared up to over-inform you over several podcast episodes. So buckle up!

Before we get into the details of monitoring, let’s cover a few basics with someone who knows this system better than most other entomologists on the planet, as freshly minted PhD in this field.

Nicole Quinn

Nicole: People know brown marmorated stink bug as the bug that gets in their house in the fall. It’s a nuisance pest in that sense. What a lot of people don’t realize or what a lot of the public don’t realize is that it’s actually an important crop pest as well, all sorts of stuff. Pretty much with some exceptions most things with a fruit, I would say, anything from like, apples and peppers and corn. Just anything with a fruit, they’re seen on basically. I think they’re up to 150 things that it will attack now. 

It has mouthparts that are kind of like a straw basically. It uses that to poke into the fruit and it injects a bunch of saliva and enzymes and things like that and kind of liquefies it a little bit and then sucks it back out. The fruit is still edible in humans after this, but it just doesn’t look good. It has these little, they call it corking, these kind of depressions. When you peel back the skin of whatever it is, it will kind of look like cork, with these brown, dead spots. It can also make the fruit a weird shape, things like that. So all of these things make the fruit not marketable and as a result, results in monetary losses for the grower. From an economic standpoint, that’s the real issue with the stink bug, not that it’s annoying how it gets in your house. 

Anna: So an important aspect of recognizing BMSB damage in your crop – something to keep in mind -  there is no different between the damage done by native stink bugs and the invasive species. You may find the errant bump or bruise from stink bug feeding here and there from year to year. There are a few other things that can cause a single depression with some corking that could be mistaken for stink bug damage too. The major difference here is in the sheer scale of potential population build up. Overwintered adults come out and lay eggs by June & July. Without natural enemies to control the number of bugs out there, those nymphs grow up to cause feeding damage in fruit and vegetable crops by August and September. Thinking about late season apple injury, you would be seeing multiple feeding injuries on one fruit and large numbers of fruit being affected. We have not seen this in NH yet.

In part one of this series, I chatted with a few entomologists about whether or not we should be alarmed about the rise in numbers we’re seeing in our regional trapping efforts and whether or not this is a sign of serious crop losses to come. I’m going to return to this topic of pest status with someone a little closer to home. I chatted with Peter Jentsch at the Hudson Valley lab to get some perspective as these pest outbreaks move north.

Anna: What would you be looking for that would make you freak out?

Peter: So we haven’t seen early season injury to pome fruit. We have seen it at the lab where they’re on peaches earlier like in July. Earlier in July we just haven’t seen.

Now, by the time that peppers get going, and jalapeno peppers are sort of my go to vegetables for what they prefer. Then there’s green peppers, you know, of course there’s sweet corn and other things, but you know the organic producers of jalapeno peppers are the ones that really get hammered. 

Even at that when we saw economic injury to jalapeno, it didn’t occur until the middle of August, and that was the onset of it. By the time that we get to the first week of September, we had put up pheromone based light trap using sprayed netting. And we had these halogen lights run by our little Honda generators you know and it was something out the early 1900s. And yeah, we were catching hundreds and hundreds of them a day and I think in total for a three week catch we had over thirteen thousand of them, thirteen five or something that we had accumulate in that one field in that one location. So there were a lot of them. 

Anna: And that was in July?

Peter: No this was in the beginning to middle of August. 

Anna: Oh, okay. 

Peter: When we got the traps set up it was September and so the next three weeks in early September is when we really had them. That exponential increase in the population seemed to be always causing all of our damage. And what freaked us out is in Red Delicious in the middle of August and in in Empire, we just saw 15% of injury on fruit by the end of August during harvest of those two varieties. And then moving toward Pink Lady, as more and more of the apples are removed from the orchard, the feeding intensity grew. You know they had gone into that feeding frenzy prior to over wintering and then from the middle of September on, Pink Lady were decimated. We saw Golden Delicious, Pink Lady had like 21-22% injury. That was scary. That’s when we realized that—okay, we’re in this for the long haul. So I’m not really sure you know, where you put the barometer, but it seemed to me that the jalapenos were the red flag, you know. The canary in the coal mine passes out. 

Anna: That makes a lot of sense though, because that indicates to you that first, I guess the nymphs, that nymphal outbreak is on the move. And if they’re coming down to find vegetables to hang out on, and then you know that  they’re in a population that’s sizeable enough early on enough in the season.

Peter: Well, the jalapeno site had, on the east side of the block, so it was probably a five acre block of jalapeno. And to the east of that there was a grove of locust trees black locust. And to the west of that there was a knoll of ailanthus. So it was like, a perfect scenario, you know. Icebergs, titanic, everything’s lining up for this bloody disaster.

The inverse of that though, at Campbell Hall where we had these high percentages of damage, there were oaks, you know, there were hardwoods, you know, that were late seed producing plants, you know. It just doesn’t seem like it was in line with the host trees that were available for the jalapeno infestation of brown marmorated. So that’s always been a bit of a problem. You know where you don’t have solid indicators to say, oh yeah we’ve the locust here we’ve got ailanthus. Of course this is going to be an issue so we’re going to put the traps out here. In the Campbell Hall side we were blindsided by all of that. They could have just as easily been in trees a mile away and had decided that they were headed in that direction and they found what they needed to find because they are pretty decent fliers from what I understand.

There was one guy, I wasn’t sure if I believe him or not, but now I think I do. There was a guy on Staten Island, he worked as like a park ranger, and he said he saw thousands of these crossing the Hudson River. I just sort of envision the Revolutionary Army on their boats. And these things were flying  en masse. And he saw them land and he looked and low and behold they were brown marmorated stink bug. 

Anna: So what do you need to know here? We aren’t too worried about early season crop injury. We are getting to be worried about late season crop injury. We will get more worried about tree fruit if we start hearing reports of stink bug injury in vegetable crops like pepper.

There a lots of approaches to monitoring and trapping stink bugs in your orchard. These bugs are attracted to light. This is really the best way to trap them in your house. I’ll include a link to the best trap for your home but lets talk about predicting risk in apple.

The best way to know if there is an army of stink bugs moving in and out of your orchard is to monitor orchard borders with pheromone-baited traps. However, these aggregation pheromones are a little different than the lures we might be used to working with. If you have ever monitored for sweet corn pests or for codling moth, you were using a sex pheromone. A chemical that one sex will use to find members of the other sex and these insects can hone right into a point source of that pheromone and into a trap. These stink bug aggregation pheromones are different – they are chemicals that males and females respond to and they create big stink bug parties. The method of capture – the visual cues of black pyramid traps or the awesome stopping power of a sticky card – these traps are sampling a portion of the bugs that were lured into a zone of aggregation or zone of arrestment around that point source. Some of us call it the party zone.  I wanted to return to a previous conversation I had with someone who did some terrific work in at the Leskey Lab, a lab that really knows how to throw a BMSB party

Rob Morrison, USDA-ARS

Rob: One of the experiments I did during my post doc, we looked at black pyramid traps spaced at regular intervals going out in four directions from a center point. At the center point we had a pheromone-baited trap and the other ones were passive. We found that BMSB aggregate in a 2.5 m radius around the pheromone source. And this was in a background of mowed grass – kind of a “food desert” kind of area. That really indicates to me that they’re not really responding to the point source of the pheromone.

Anna: So if you’re using pheromones in the orchard that zone of aggregation is probably the trees on either side of the trap?

Rob: So obviously it depends on the density of the planting for the orchard but we did some commercial attract and kill trials where we put a high dose of pheromone in a centrally baited tree. We had tarps under the surrounding trees, which we sprayed, and looked at how many BMSB were there – what’s the natural area of aggregation in an orchard. We found that the majority of individuals were confined to that central baited tree.

Anna: And what are your feelings on recruitment? How much do you’re think you’re pulling them in?

Rob: That’s good question and, by the time I left the lab, we didn’t have a good handle on that. There has been some follow up work since then looking at how far they follow a pheromone source. Basically, if you have a pheromone source in one location and you release bugs from certain distances away, how many will you pull into that pheromone source? From what I understand that distance of pull is very small. You are likely not pulling individuals from great distances and having them all clobber your orchard. Rather, if they’re already moving in that area, they’ll got to that trap and be removed from the population.

Anna: All right so for those of you who want to predict outbreak populations in your orchard as you are nearing harvest time, get yourself some pheromone baited pyramid traps or sticky card traps. The pyramid traps are more sensitive than the sticky traps but the pyramid trap are a bit more cumbersome to haul around and set up. You’re going to get worried when you start catching more than 10 stink bugs per trap in the pyramid traps or more than 4 bugs per trap in the sticky cards. If you’re in New Hampshire, I’ll send you some traps! Just give me a holler!

We will pick up where we left off next time with what to do if you find a BMSB outbreak on your farm but that’s it for now. Thank you to Nichole Quinn (of Virginia Tech now USDA-ARS), to Peter Jentsch (at the Hudson Valley Laboratory) and Rob Morrison (of USDA-ARS).

Cover Image: BMSB Susan Ellis, Bugwood.org 

Music:By permission and Creative Commons