Think Out Loud

Oregon facing threats from invasive vine mealybugs

By Rolando Hernandez (OPB)
July 17, 2023 4:16 p.m. Updated: July 24, 2023 8:39 p.m.

Broadcast: Monday, July 17

Aerial shot of workers in a vineyard.

File photo from March 28, 2023. The vine mealybug was first spotted in 2021 in Jackson County. The pest can cause damage to Oregon's vineyards by affecting fruit quality and crop yield. New funding from state lawmakers will help address the threat the bug could bring.

MacGregor Campbell / OPB


An invasive vine mealybug was found in Southern Oregon in 2021 and since then, vineyards have been fighting to eradicate the insect. The pest can cause significant damage to Oregon’s grape vines, affecting fruit quality and mold growth. State funding from SB 5506 will invest more than $400,000 to monitor, research and suppress the insect before it becomes widespread in the state.

Brian Gruber is the president of the Oregon Winegrowers Association. Greg Jones is the vice chair on the Oregon Wine Board’s board of directors. And Vaughn Walton is a professor at Oregon State University’s horticulture department . They join us now to share how this bug can potentially affect Oregon’s vineyards and the potential impact of the funding to address the threat it poses.

Note: This transcript was computer generated and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. The vine mealybug has been a serious problem for California’s wine industry for about three decades. It can cause significant damage to grapevines, affecting fruit yield and size and causing the growth of mold. Given that the bug can be found throughout the Golden State, Oregon’s grape growers have been fearing its arrival. In 2021, their fears were realized – the vine mealybug was found in Southern Oregon. Now, Oregon’s wine industry will have more resources to contain and potentially eradicate the pest. On the last day of the legislative session, lawmakers allocated nearly half a million dollars toward this effort.

Joining me now to talk about the situation are Brian Gruber, he is the president of the Oregon Winegrowers Association and a winemaker at Irvine & Roberts Vineyards in Ashland. And Greg Jones, he’s the vice chair of the Oregon Wine Boards Board of Directors and the CEO of Abacela Vineyards and Winery in Roseburg. Welcome to you both.

Brian Gruber / Greg Jones: Thank you.

Miller: Brian Gruber, first. What went through your mind when you heard that vine mealybugs had finally been found in Oregon?

Gruber: Well, it’s one of those situations where we’ve been looking for them as early as 2010. So we knew that they could come. It wasn’t a shock that they got here. I think the biggest thing was, well, I’m glad we’ve been watching, because now we know we have something to work on, as a challenge. But it’s also something that we believe is manageable. So it was more about, well, I guess it’s time to get down to work.

Miller: What have these bugs meant in California?

Gruber: Yeah, they’ve spread, like you mentioned earlier, they spread through California over many decades. I guess the important thing about this is it’s not a disaster. It’s a pest that can be managed. It’s a pest that doesn’t affect wine quality in most situations. It’s about yield and economics and it’s important for us to address them and manage them. The biggest risk we face is that they can spread some kind of diseases of the grapevines that would reduce our yields over time.

So we were watching because we knew that was happening in California. [As a ] Southern Oregon wine industry where we border on California, we knew that they could potentially spread here. And when something like this comes along, it’s really important to be ahead of it and understand it while it’s still small and something you can address rather than wait for something big to happen.

Miller: Greg Jones, it seems like an important point that Brian just mentioned, that we’re not largely here talking about wine quality, we’re talking about yield, about how much wine you can make and how many grapes you have to make wine with. But in terms of the worst case scenarios here, I mean, if there weren’t monitoring, if there weren’t efforts to control the spread, what would it mean?

Jones: Well, first of all, I’m very proud of how the industry has been proactive with this, as Brian said, we’ve been watching and I think any agri-business should be prudent looking at regional issues and how they may come to our industry here in Oregon. I think we’ve been ahead of the curve with this and we’ve done some really good things to put ourselves in the right position to better understand, what are the overall numbers that we’re seeing? How can we best combat the issue over time? I don’t think the threat is so immediate that it affects this vintage per se. But I think over the long term, we just need to be very, very cautious, make sure we’re doing the right things in terms of monitoring eradication. And the work that all of our advocacy agencies are doing in the state, along with the state government supporting us, I think will go a long way to helping.

Miller: What role does education play in this?

Jones: Oh, this is huge. I’m actually standing in a field right now where part of the conversation is about education, trying to understand, what do we know? What do we [not] know? And how can we help growers who may not be familiar with either this pest or the potential measures that we can use to help control it, to give them some insights. And so education is critical for helping everybody get a better handle on what we have in front of us and how to best manage it.

Miller: Because even though, as you said, that some people in Oregon have been really focused on this for more than a decade now, you get the sense that there are some grape growers or winemakers who still need that education?

Jones: Well, yes. And of course, in this case here, we have a situation where the likely spread of this pest is from the south to the north. But we arguably don’t know that completely. And so that’s why having the state support us and the ODA and OSU doing some of this work will give us a better handle on that. But right now, the grape growers in the Northern and Eastern part of the state are not very familiar with this. And so educating people either in the areas we have the most concern with, or those areas that potentially could have some concern is really important so that we’re all ready when we need to be.

Miller: And I should say that we are actually gonna be talking with a professor from Oregon State University’s Department of Horticulture, an expert on this particular bug, in just a few minutes, after we talk with the two of you. Brian Gruber, what kinds of questions have you been getting from grape growers since the bug was actually discovered in Oregon?

Gruber: It’s really interesting. First and foremost, I think we have a lot of support and I think Greg mentioned it. I want to talk about it really quickly because this is a great partnership. So it’s a wide array of people and organizations that support our industry. It’s not just growers. Big, big help from the Oregon Department of Agriculture and the Oregon State University and their Extension Service. And I think one of the great things we have right now is the Southern Oregon Research and Extension Center doing a lot of the education that Greg mentioned, who is at their facility today. They’ve been fielding a lot of the questions about this because they’re, they’re the experts. You mentioned you’re gonna talk to Doctor Walton later today. He’s an expert in this as well.

So it’s great because we have experts and we have educators working to help us make this something that we all can understand and wrap our heads around and understand what to do. But a lot of the questions are things like what are they? A lot of people had no idea what a vine mealybug was. It’s a really small white fuzzy insect you can see with the naked eye. Oftentimes it lives under the bark of a tree or the grape vines and rarely do you actually see it if you have it going on in your vineyard. So that’s a big piece of it. So, the next question is, ‘Well, how do I know if I have it?’ And that’s where we get into trapping and monitoring. That’s what we’ve been doing for the last decade – is monitoring and putting traps out trying to catch these insects to prove that there is a positive identification. It wasn’t until 2021 that we found one, after many years of looking. But people wanna know what they look like, how do I find them?

I guess the last big question is what’s the impact, what do they do? I think, like we’ve talked about a little bit, that the majority of the problem that they create is they feed on plants and as they feed on the plants, they can spread disease among plants. If you have that disease in your vineyard, you could spread it more widely. It can come in from other places and that can really impact your yields in the vineyard.

So, really, wanting to understand: What are they? How do I find them? Do I have them? And what do they do? [These] are the big questions we’ve received. But we’ve got a lot of people out there helping provide education.

Jones: I was just gonna add to it. As Brian said, I’m out in the middle of the Southern Oregon Research and Extension Center where we have quite a few growers here. We’re learning more about quite a few different things, but one of the vine mealybug  components that we’re learning about is about how it spreads. And while we can’t control every potential way it spreads, for growers to be much more aware of how the spread can potentially happen, we can keep it from occurring to the degree that it might otherwise. And so part of that education component includes everything Brian mentioned, plus this idea of understanding how it gets from place to place.

Miller: Also more issues that we’ll take up with our expert,

the Horticulturalist from OSU, in just a few minutes. But Brian, back to you, the state lawmakers, as I noted at the beginning, they allocated close to half a million dollars on the last day of the session to combat this bug. Were you thinking that that money was actually going to be allocated?

Gruber: Well, that’s a great question, and I think it’s an interesting piece of how we found the funding for this. And it actually starts back at the Oregon Wine Board, where Greg is the chair of the research committee. Back in 2022, when the first identification of this happened, we started trying to find ways to address the problem. And the first $50,000 last year and another $55,000 this year, money was allocated by the industry to the Wine Board to start working on this problem. But we realized it was a bigger problem than that we could address on our own as an industry with our own funds and asked the state for help.


I guess what I’d say about the legislators, we had really strong support from the legislature on day one. We brought this problem to them, our professional organizations like the Oregon Winegrowers Association that I’m the president of the board for, but also the Oregon Wine Council, Rogue Valley Vintners, Willamette Valley Vineyards, brought this issue to our legislatures and they had a great support for us on day one. I’d say, Speaker Rayfield and Senate President Wagner made it a priority. Representative Gomberg initiated a legislator letter asking for support. We had a lot of support from day one, so we felt that if there was funds possible from the state budget, that they would make it happen.

I guess the biggest question was, was there enough revenue in the state? And when the final revenue forecast came back, looking favorable, we certainly had exceptionally strong and unified support to make this happen. So we felt good about the support. It was just a question of whether the money would be there and we were really pleased that it came to fruition in the last day.

Miller: Brian Gruber and Greg Jones, thanks very much.

Jones: Thank you for having us.

Gruber: Thank you.

Miller: Brian Gruber is the president of the Oregon Winegrowers Association and the winemaker at Irvine & Roberts Vineyards in Ashland. Greg Jones is the vice chair of the Oregon Wine Board and the CEO of Abacela Vineyards and Winery in Roseburg.

For another perspective on vine mealybugs, I’m joined by Vaughn Walton. He is a horticultural entomologist at Oregon State University who has studied this pest for a number of years.  Welcome to the show.

Vaughn Walton: Thank you so much.

Miller: Thanks for joining us. So, as we just heard, these bugs can damage vineyards in a variety of ways, both directly and as vectors. But let’s start with the direct harm. What do they do, themselves, to grape vines?

Walton: So these bugs feed on the vines. They have a lot of moisture go through their body and some of the extra moisture and sugar coming from the vines are being excreted in the form of honeydew. That honeydew,  late in the season, if the bugs are on clusters, can land on the clusters themselves, it can also land on  leaves and then you have these other microorganisms like sooty mold starting to grow on those, honeydew which can reduce photosynthesis.

In addition, you will have ants starting to form that honeydew protect the mealybugs against natural enemies. And so you’ve got ants on the clusters, honeydew on the clusters, sooty mold on the cluster is itself as well. And then in severe cases, you can have decline of vines because these bugs have such a rapid life cycle as opposed to the other mealybug species that we have here in Oregon.

Miller: And then, in addition to all that, there are also vectors for certain diseases?

Walton: Yes. Vine mealybug is one of several insect vectors of the vine leafroll virus. And there are various strains of these viruses. There’s been a lot of research done on these viruses also here in Oregon, starting around 12, 13 years ago. These viruses can impact the quality of the crop itself. And so if you have the combination of vine mealybug, some viruses in vines, those vine mealybugs will spread those viruses around within vineyards, between vineyards and that those viruses might negatively impact the quality of vines, because of the impact that it has on the photosynthesis of the vine itself.

Miller: How long have you been working on the issue of vine mealybugs?

Walton: Wow. I started working on vine mealybug in the previous century, 1996. [Laughing]

Miller: It sounds like a long time ago when you put it that way. Well, I’m curious, how much has our understanding of these particular bugs changed over the course of that time? It’s nearly three decades.

Walton: It’s been a while. So back in those 1990s, we did not have a pheromone. We did not have pheromone traps. Growers did not know how to monitor for it. And usually the problem would only be seen by the growers as soon as mealybugs were really well established within vineyards. And so even in South Africa, where I’m originally from, growers really felt that they wanted a tool that could help them monitor for it.

There were scientists here in the United States, at the University of California Riverside, who identified and synthesized those Pheromones. And it turned out that those pheromones are extremely sensitive, where we can now pick up these problems way before it’s actually a big issue within the vineyard itself. And so we can nip the problem in the bud much, much more effectively now, which is what we’re doing here in Southern Oregon. We’ve got these monitoring tools which we didn’t have back then. We have chemistries, systemic insecticides, which are extremely effective, which we didn’t have back then – two tools that are really useful.

In addition, we also are able to now use mating disruption. And that’s another tool that we’re using here in Southern Oregon. We’re treating the vineyards firstly with the systemic insecticide,

which can also kill the mealybugs on the root systems and in hidden places. And then we add mating disruption over the top of that and that just provides an additional layer of control. And that’s a tool that no one really had back about 20 or so years ago.

Miller: We’ve had a recent conversation about natural wines in Oregon. In the past, we’ve talked about biodynamic wines or organic wines, the various labels for putting less stuff into final wines or as you’re growing grapes. Could vine mealybugs force more grape growers to use pesticides or insecticides?

Walton: So, when you’re an organic grower or a biodynamic grower, you still have tools. And one of those is mating disruption that I just mentioned a few minutes back. It’s a very powerful tool. We can also use some of these older chemistries, oils in the late dormant period, soaps, washing the mealybugs out of the vine during the late dormant period.

The difficulty with biodynamic and organic is that these tools are not quite as effective. But generally speaking, the most effective tool that we as human beings have is our ability to use an integrated approach, where we’re monitoring more efficiently, growers can still use that same monitoring method. Even though they’re organic or biodynamic, they can still use mating disruption. And generally speaking very often with organic growers, they will deal with the problem earlier. It’s a little bit more difficult, tools are not quite as effective, but it can be done.

Miller: Are we now entering a phase where stuff involved in the growing of grapes and the making of wine is gonna have to stay closer to where it is to the vineyard to prevent the spread of these bugs?

Walton: Yeah. So what I think we’re realizing is that it’s a list of actions that we can take. And I think Greg said that very clearly earlier on. You use the low hanging fruit first, pick those first, figuratively speaking, being a little bit more vigilant, when plant materials are procured, make sure that the correct treatments of those have been done so that you firstly don’t get your mealybugs into a newly planted vineyard, and then use your monitoring tools which can be very efficient. And generally speaking, I think we’ve got some good tools. We can still produce very, very good quality grapes. We’re benefiting from all of the work that had been done in other countries, in South Africa and Europe, here in California and so on, and we better understand the biology of the insect.

Generally speaking, I think that this is just a growing pain for our industries. Our industry has grown significantly over the past several decades.

Miller: Vaughn Walton, thanks very much for joining us.

Walton: Thank you so much.

Miller: Vaughn Walton is a horticultural entomologist in the College of Agricultural Sciences at Oregon State University.

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