247: Can Area Wide Management Eradicate Vine Mealybug?

If you are dealing with vine mealybug in your vineyard, you are not alone. Kent Daane, Cooperative Extension Specialist at the University of California Berkley studies different types of mealybug populations across the globe.

Kent covers organic and conventional strategies, ways to increase the presence of generalist and specialist natural predators, and the importance of establishing refugia for beneficials.

His latest work focuses on area-wide management tactics. Looking to the European Grapevine Moth eradication program as an example, Kent sees an opportunity to decrease vine mealybug populations through neighborhood-driven monitoring, trapping, coordinated sprays, and mating disruption.

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Transcript

[00:00:00] Craig Macmillan: Welcome to Sustainable Wine Growing with Vineyard Team. Our guest today is Kent Daane. He is a Cooperative Extension Specialist with the University of California, Berkeley, and he works primarily out of the Kearney Agricultural Research and Extension Center. And today we're going to talk about a number of topics.

Thanks for being on the podcast, Kent.

[00:00:17] Kent Daane: Craig, thanks. I'm happy to be here.

[00:00:20] Craig Macmillan: Let's dive in on one pest that everybody's interested in, continuing to be interested in, and you may have some new insights or newer insights on this. Let's start with mealybug management. Kind of what's the state of the art in that topic right now?

[00:00:33] Kent Daane: Yeah, that's been the number one question I've been getting for many, many years now. It is an invasive pest. We know it came in, probably being brought in by a grower down in Coachella Valley. It has since spread into the San Joaquin Valley, Central Coast area where you are, Napa Sonoma, and it's been found now in Oregon.

Just like Napa, Oregon has attempted an eradication program. And probably just like Napa, most likely it's not going to work. It's a very, very difficult insect to kill 100%. I mean, I can come up with all kinds of different programs, soft programs, hard programs, expensive programs, inexpensive programs, where I can suppress that insect pest. It's very difficult to remove it from a vineyard. And that becomes important when you think about the kinds of damage we're worried about in Central Coast wine grapes.

Pretty much anywhere where they're looking at grape quality. But especially in the cooler regions. So, this insect, this mealybug, is one of many mealybug species. that is a vector of grape leaf roll associated viruses. And this is the primary reason it grows to such high pest status. So for the most part, the growers can knock its levels down far enough that it's not in the grape clusters or it's rarely found in the grape clusters. That's more of an issue for table grape growers. It's a cosmetic pest. When you look at some of the Regions in the San Joaquin Valley where they're growing a lot of table grapes Kern, Tulare, Kings, Fresno, counties, there's enough heat accumulation and these grapes are harvested early enough in the season that they can still build up their Brix. They can still get a very good grape to market. Even when there's some vinely bug on the vine, they just don't tend to be as impacted by this leaf roll pathogen as our wine grapes.

When you get into regions like San Luis Obispo, Napa, Monterey, Oregon, where they really are trying to hold those grapes on the vine for a longer period of time, trying to build up the bricks levels. That's where this. pathogen causes so much damage.

[00:03:06] Craig Macmillan: most of our growers are already going to be familiar with this, but what kind of damage does the vine mealybug cause? It's so, so terrible.

[00:03:12] Kent Daane: So the vine mealybug, besides being a vector of this pathogen, is also a direct pest of the grapevine. It can feed on the roots, on the trunk, on the leaves, and in the fruit. When this first hit California, we were working on it primarily as a San Joaquin Valley pest. growers that were putting on, you know, the products of the day dimethylate, lanate. If they were missing , the, target window where that pest was exposed, we would see thousands and thousands of mealybugs, not just per vine, but sometimes a thousand millibugs per leaf. It was causing defoliation. It was causing the berries to raisin on the vine. In South Africa, populations were getting so heavy. It was killing the vines themselves.

How many people out there 20, 30 years ago were spraying so many neonics as we're saying today? We weren't doing that. now really, we were spraying for leaf hoppers as our number one pests followed by mites in case there was a flare up. It changed what we were doing in terms of pest management. In fact there's a group of us working internationally. Not just on the vine mealybug, but other mealybug species, because we've seen vine mealybug, grape mealybug, citrus mealybug, all becoming more problematic over the last decade. And we're, asking that question, why? What has gone on? And one of the thoughts we've got, not yet shown, but one idea is that we just sprayed so many of these, these newer chemicals that the mealybugs are developing resistance, The natural enemies are not, and we're seeing an escape of some of these mealybug species in now a, to them, a pesticide lessened environment.

[00:05:10] Craig Macmillan: speaking of biological control, so this is an invasive pest, came from outside the U. S. That's the kinda the classical biological control problem. the pest comes, but its natural enemies don't come with it. there are some natural enemies of vine mealybug in the United States.

[00:05:24] Kent Daane: Yes, they are, and I don't want to go too deep in the weeds on this, but this is new, very exciting to me. I did an importation program, that's a classic biocontrol program, where we go to the pests, origin, we look for natural enemies and we bring those back to the United States. Growers can't do that.

It's got to go into quarantine. We have to study those natural enemies. Sometimes for years to make sure that they're not going to do any harm.

The classic example people think about is I've got a problem with rats. And so I bring in a weasel, the weasel kills all the rats, and then starts going after my chickens.

We don't do that anymore. Classic biocontrol is now much more modern. We've got all kinds of protective barriers against making a mistake. In fact, I think that we've gone a little bit too far. I think we're overly cautious.

Bringing this back to the Vine melaybug, I imported material from Europe, from Israel, from Egypt, and from South Africa. We were finding mostly the same species in most of these different regions. The two most important species at that time were called Anagyrus pseudococci, which is The well known parasitoid that you can purchase from insectaries. The other one is Coxydoxinoides peregrinus, no common name on these insects. Both are established in California.

When I did this work, we noticed a difference between the anagyrus near species Pseudococci that we were getting in Sicily and Spain with the material that we were getting that had already been established from Israel

and what we're finding in northern Italy. Working with a taxonomist, Sergei Trapitsin he found some significant differences between these. And later on after both were imported in the United States determined that these were two species, one still Anagyrus pseudocoxi and one Anagyrus vladimiri. So sometimes you'll see insectaries selling Anagyrus vladimiri and you think, Oh, I want that.

That's different. It is different, but both are established in California. We're actually going to do a followup study. now in collaboration with this international group to find out what we've got in California. I suspect we've got both. Now, why is this exciting? Because at the time we were doing this work, we felt like the parasites were different, and we felt that these different groups that we were importing, maybe one had co evolved with the citrus mealybug, And the other with the vine mealybug. And we had already done some work with the vine mealybug, molecular work, looking at its relationship to each other around the world. and their names are, scientific names would be citrus mealybug, planococcus citri. Vine mealybug, we knew as planococcus ficus, which means, Ficus tree, fig tree. And we were showing that this group was, they had an outlier and ours was the outlier. And then working with this international group, they said, look, back in the fifties, there was a planococcus vitis. And I think what you've got, what we've got on vines, is the vine mealybug. But not in Iran and Iraq at that time.

And, and maybe in that Mediterranean region Israel, Egypt, Iran, Iraq, Turkey the Mesopotamian region, I think is what it is. Maybe there are some parasites there that we didn't have. Certainly, my colleague in Egypt and more parasites than we were finding in Europe. We just weren't able to get them all to establish in colony in quarantine. So it opens up the window that, that maybe there's something still out there. At this point in time, I say in all the countries where vine mealybug is reported as a problem, that's most of Europe Mexico, South America South Africa. We have the best of those parasites.

We just want to delve deeper into what are we seeing in Turkey? How does that match up with what we know is in Egypt? And I do have colleagues in Iran. It's just harder for me to go there.

[00:10:09] Craig Macmillan: right, of course. so this makes me think, is it possible that we have mixed populations of these mealybugs in California on the same plant, so it's different areas?

[00:10:17] Kent Daane: So that's the project we're working on with this international group. What we decided to do in a three part approach is to first find out what everyone's got.

The assumption is that in South America, In the United States, North America, we have got single invasion events. Our guess is that it arrived in the U S in Coachella and Mexico at the same time. We're pretty sure that the population they have in Peru is from California Yeah, they were bringing nursery wood in and lo and behold, they found vine mealybug. We went down to look at a nomatode problem to be honest with some UC California researchers. And we found that they had some mite problems at the same mites that we've got in North American California. So they were probably not being very cautious in what they were importing. So we're assuming that South America's got this California group which came from Israel. We know Israel and Egypt have something very similar, but it's different than most of Europe. South Africa is similar to Portugal and Spain, which makes sense with the trade routes that were going on in the 1960s. What we're guessing is that The European groups, there probably are, there's reported failures of vine mealybug mating disruption in some European areas. And we think that probably is this other mealybug that is probably in Turkey. So it's all very exciting to me, kind of delving deeper into the weeds on this. But the first part of this international group, again, a great group of people, Europe, South America our first part is what do we all have? Our second part is what we're doing a grower survey that we actually sent to the vineyard team and they spread out to some growers as well.

What are, what are growers using to control the mealybug? Because maybe with some of the, we find out what it is and maybe growers are working harder to control our vine mealybug than say that the fig millebug which appears to be what they've got in most of Europe.

Remember when I started the foreign exploration when I was in Spain growers would tell me yeah we've got the vine millebug but it really is not much of a pest. Citrus millebug on vines is more of a pest. Well they probably have that fig mealybug but

[00:13:01] Craig Macmillan: Ah,

[00:13:01] Kent Daane: You know, taxonomically, it looked to us like the vine mealybug.And I hope I'm not throwing all these things out and it's confusing.

So, second part, that is, the survey. What do you have and what are you using to control it? And if it matches up that, yeah, what we've got is the one that's more difficult, that fills in a lot of boxes. Third and fourth part are now looking at the natural controls.

What parasites are you getting coming off of this? What parasites are in your region? And how do they respond to the pheromones that we know are out there? So if they're not, if they're responding to both citrus and vine, maybe that's an indication that it's this other group. If they're not responding at all, or weakly, yeah, we've, we've got three or more distinct species. And we can't tell them apart, but maybe the parasites can.

[00:13:56] Craig Macmillan: this is kind of a practical question. hoW do you monitor parasitic wasps? They're tiny. They live in refugia. They then come out and plant their eggs in their host. that seems like a really hard thing to do.

[00:14:10] Kent Daane: That's an absolute fantastic question. So let's look at that most common parasite, Antigyrus Pseudococci slash Vladimiri. So what we found over the years is that it does a great job on mealybugs that are exposed in the fruit, on the leaves, on the cane. By the end of the season, if you're not putting on a lot of contact chemicals, you're getting greater than 40 percent parasitism. Very easy to see,

[00:14:43] Craig Macmillan: Right.

[00:14:43] Kent Daane: doesn't do very well against the mealybugs under the bark, because it's got this searching behavior where it's got to get on top of the mealybug, determine how big it is, do I want to put a an egg that's not fertilized in that, which would be a male, and they need smaller mealybugs for that. Do I want to put an egg which is fertilized? In that, that will become a female parasite that needs larger host.

[00:15:09] Craig Macmillan: the same insect, the same parasite has the ability to do either.

[00:15:13] Kent Daane: Yes.

[00:15:15] Craig Macmillan: Wow.

[00:15:15] Kent Daane: again, this is really a neat subject and I hope I don't bore the audience too much. But, a lot of these parasites that become important for mealybugs they have this little sac, so you've got your oviduct going to your ovarioles, in the female.

And right around the oviduct area, before it splits into the two ovarioles, you've got this little sac called the spermatheca. unlike humans, where the sperm goes in and Seeks out the eggs and fertilizes it. The sperm go in and the female parasite stores them in the spermatheca. And then as the eggs are mature and ready to go down, oviduct and get ready to be oviposited into the mealybug, the female decides to fertilize the egg or not fertilize it.

And if it's fertilized, it becomes a female. If it's not fertilized, it becomes a male. And that allows her to determine what the host size is, because the females are bigger than the males. And so she will walk up and down. and size that mealybug and say that this, this mealybug is a good enough size that this is worthy for me to put a fertilized egg in and that will become a female.

Or a second in store mealybug, she'll say, this really isn't that good of a mealybug host. So I'm going to put An unfertilized egg, and that will become a male. And that was, going back to this Anagyrus Vladimiri versus Pseudococci, that was the most important difference that we found in this Sicilian and Spanish group of Anagyrus, was that they would oviposit and put females in smaller hosts than the male. earlier parasite which probably evolved on the citrus mealybug.

So going back to this question because I do go off on different tangents. How do you sample for these things? So it's really easy to find a mummified mealybug on a leaf. But remember what we're doing. We're spraying now a lot of Movento and we're spraying a lot of the Neonics regardless of its Admire, Platinum, or generic derivative. They're all good materials. and maybe you're putting on an IGR like a plot, again, all good materials, Assail, all good materials. What they tend to do is work really good against the mealy bug, which is exposed on the leaves. Our systemic materials are really good at going out to the leaves. Our contact materials, our IGRs, the neonics, that are contacts kill the mealybug that's exposed. All of these materials do less of a good job with the mealybug underneath the bark.

we're not getting a true indication of what these parasites can do because we're killing the host that's the best location for them to attack. So that means to really find out what's going on, you got to strip bark oftentimes. So now you're looking at parasitism in that region of the vine that the parasite doesn't like to be. Now, if we add to this, this other good parasite, which is the coccidoxoenoides peregrinus, we really liked to bring this in because it attacks the very, very small stages of the mealybug, the first and the second instar. It's sometimes a small third, but really it's focused on the second instar.

[00:19:05] Craig Macmillan: Got it.

[00:19:06] Kent Daane: It's in California. You can find it, but it's really hard to find out what impact it's got because it will parasitize the mealybug and will cause the parasitized mealybug to die. to feel sick and to seek out some area for protection because the anagyrus if you see that mealybug parasitized on the leaf causes that mealybug to kind of glue itself down to the leaf You have to flip that thing to get it off the leaf.

A mummy is a dead mealybug which sticks to the leaf. The coccydox anoides causes the mealybug to find a place of protection because it doesn't stick it to the leaf. So it often times goes to the trunk, or goes to the stem, and eventually falls off the vine, and will pupate down into the ground.

And so to sample for that one, you have to collect them as first or second instars live, bring them back to the insectary, and rear them out to the parasite, which is just really a lot of work hard to do. so these things are far more difficult to do. Sample four, then going out and counting, you know, aphid parasites, which are just out there as little brown mummified aphids.

[00:20:29] Craig Macmillan: it sounds like this would play a role in my timing of my insecticide applications, whether it's Spirotetramat or Neonic or One of the programs that I think is common is to have spirotetramat on top and have a myothiamethoxam soil applied. Does that sound right?

[00:20:47] Kent Daane: Yeah, that sounds right. I mean, they're both good products and they're doing what they're supposed to do. they're killing the mealybug. And when the timing is right, they're getting out there before the mealybug. So as the mealybug is going out towards the leaves. You know, they're probably doing a better job than the parasite will do on its own.

Now, if you are an organic grower and you can't use those materials, then timing does become a little bit more critical because you're putting on, oftentimes, organic materials every 10 to 14 days because they've got a shorter residual. So on those you may want to, you know, work your timing around to avoid to give it a window of opportunity some of these natural enemies. There you're looking on the leaf, you're looking for mummified mealybugs. You know, are, do I have some of these good natural enemies in the field? You're looking for the mealybug destroyer, or one of the other beetles. Green lancelings are also doing a pretty good job. So you're monitoring those. And maybe you're deciding, I've got a lot of good activity maybe I should wait to put on pyganic or one of the other materials, which is broad spectrum give the other parasites a chance, a cycle, to see what their impact's going to be on that millibug population. Or maybe you're going to leave every fifth row unsprayed to let the parasites come back in and then hit that row later. So you've got a chance for those natural enemies to move the just sprayed vines.

[00:22:22] Craig Macmillan: That was going to be my next question is what is the refugee situation for these parasites? Do they come into the vineyard, do their thing and then leave? Do they come in when there is host and then they hang out in the vineyard for the rest of the season? Do we know? I'm just thinking about ways that I can preserve, conserve those parasites as much as possible so that they're there when I need them.

[00:22:45] Kent Daane: That's a great question, Craig. And let's break this apart into two different areas. Let's talk about First, the generalist predators that I just mentioned, the green lacewings, a good mealybug predator against the smaller mealybug stages. A lot of the things we do to enhance natural enemies will enhance generalist predators.

So that's where your cover crops come in. That's where your pollen and nectar come in. You'll increase generalist predators. Ladybird beetles, green lacewings, minute pyre bugs, those can all attack and kill. That same group of cover cropping that brings in the gentleness predator may have little impact on the specialized parasitoids.

Things like the anagyrus and the coccidocsinoides, what they want is the mealybugs. And not all mealybugs will do. They really want the mealybugs that are better hosts for them. So, they tend to get everything they need out of that pest population. They can host feed. They can stick their ovipositor into a mealybug, turn around and feed on some of that exudate, some of what's being bled.

The mealybug creates honeydew. That honeydew, instead of trying to plant a cover crop for honeydew, that honeydew serves as a food to increase the longevity of those parasitoids.

And as the mealybug density goes down, the parasite numbers should go down as well. Now there are different kinds of food sprays that we hope to look at that oftentimes do help increase both generalists and perhaps specialist natural enemies.

[00:24:46] Craig Macmillan: Hm.

[00:24:46] Kent Daane: The number one thing you do to to enhance beneficial insect numbers is to watch the broad spectrum insecticide sprays or to time them where you're not spraying, you know, all 100 acres at the same time, but you're leaving a refugia so they can move back in.

[00:25:08] Craig Macmillan: Interesting. So, I might be looking at something and saying, okay, I am going to have to take some action here. I'm hitting an action threshold but not pull the trigger on the whole thing. leave one area for a little bit, and then can you come back and treat that later, so that you're preserving some of these folks, and then they can come back on the other side, and find a balance between the chemical and the biological.

[00:25:31] Kent Daane: Right. A balance, a delay might just be 10 days, might be 20 days. We don't want to miss our spray window, but remember, Most of the natural enemies are winged as adults, whereas the female mealybug is never winged.

Fairly slow, fairly thestle. So that allows for those beneficials to come back in. And if you're a large grower this just happens over over the course because you can't spray 100 acres in a day.

[00:26:07] Craig Macmillan: Right. Right. Fascinating. Are growers starting to adopt, in your experience with the folks that you work with, are growers starting to adopt these kinds of timings and techniques and methods?

[00:26:19] Kent Daane: I think growers are constantly adopting, improving, changing one of the common misconceptions when I talk to students or people who just don't don't know how to farm or farmers is that farmers really don't want to spray.

Spraying costs money. it is an added expenditure, added time, added worry. So they'd much rather, you know, go back 50 years when we didn't have all these invasive insects from Vine mealybug to Virginia Creeper growers are always seeking out how to improve the insecticide materials they've got, how to reduce the insecticide applications they have to make. And that does include natural enemies, mating disruption. What it comes down to is just costs. So oftentimes there's a trade off.

If you're going to use mating disruption, you may not be doing three applications of an insecticide for vine mealybug. Maybe it's one insecticide plus vine mealybug mating disruption. If you're organic and you're releasing beneficial insects and spraying every other week. Maybe you don't have the cost for mating disruption. So these are all decisions that individual growers have to make. Obviously we've got some growers in some regions can spend 300 per acre for mealybug control. Other growers simply cannot do that because of the value of, their product at the very end.

[00:28:03] Craig Macmillan: Right.

This is kind of a natural lead in to something I wanted to touch on, and that is the Virginia Creeper leafhopper that's found on the North Coast. That also an invasive, correct? Came in from outside.

[00:28:15] Kent Daane: It is invasive to some extent. It is not invasive like the vine mealybug is from. The Mediterranean region Virginia creeper most likely is, is North American. But yes, it was never really a California leafhopper pest. It was, no England, Canada. Pest that then went into Washington, then went into Oregon, that then came into California. interestingly, the, leafhopper that I worked on for so many years the variegated grape leafhopper probably North American, probably had a different avenue, probably came up from the south, from Mexico, Texas, to Arizona, to California. So Some of our invasives are close relatives.

[00:29:07] Craig Macmillan: Interesting. what's the difference in damage that's caused by the Virginia creep leaf hopper and the the variegated leaf hopper.

[00:29:17] Kent Daane: So they're, they're very similar.

I think that the grape leafhopper is the one we've been dealing with for the longest time and has been relatively mild compared to the other two.

The variegated grape leafhopper When it first came into the San Joaquin Valley, it could defoliate vines. It had three to four generations per year.

[00:29:42] Craig Macmillan: Oh, wow.

[00:29:43] Kent Daane: It seemed to be much more damaging than the grape leafhopper.

Virginia creeper leafhopper, now in northern California, making its way south. So it's gotten to the middle of the state. It's in Napa, Sonoma, Sacramento. I have not seen it. Heard it reported in the Fresno area. Oh, it has been reported in Fresno.

But I'm not saying it causes much damage here. We really don't get many leaf hopper reports for damage here, except for organic growers. And that's because all the sprays for vine mealybug.

Most of those vine mealybug sprays are very good against the leaf hoppers. Where I have seen it as a pest. It's been mostly in wine grapes. Mostly in the cooler regions of the state. Mostly controlled by conventional insecticides. There are programs organic materials registered for Virginia creeper that I think have done a fairly good job. But it, it does get out of hand. And I think for all these leaf hoppers with organic materials, what happens is that The organic products tend to not work well , against the leaf operant in the egg stage or the leaf operant in the adult stage.

So timing is very important. You want to get those materials on. when egg hatch is nearly complete and when you've got mostly first and second instars out there. That's because most of our organic products tend to impact these pests by either being a desiccant like the soaps that dry it out or a suffocant like the oils that clog the spiracles. And so the the, adults just fly away from that tractor rig as it's coming down.

The eggs are protected inside the leaf itself, in their little clusters for the Virginia Creeper. And the larger insects can, they're just more mobile. So it's hard to kill them. So timing becomes relatively critical with these insects. I've not worked directly with Virginia creeper other than hosting Houston Wilson did his graduate work in my lab and really focused on, on the parasites of this insect.

Lucia Varela, now retired, did focus on looking at the different insecticides and she's got a nice summary article which is on Monica Cooper's website. It talks about the different insecticides, U C cooperative extension Napa County.

And she's got a website that goes into materials for organic growers for Virginia creeper leaf hopper. I think that's where I saw. that information posted. And what Houston did was he just looked at and tried to improve the Enneagrus. So we get those two confused. The Lilybug parasite is Anagyrus. The Leafhopper parasite is Enneagrus.

The two names sound pretty similar, but one is an inserted family and one is a Mimerit. Or a fairy fly, fairy winged fly. They're some of the smallest insects known. So,

[00:33:03] Craig Macmillan: Wow.

So, we are continuing to look at these new parasites, how they're performing, we're learning a lot more about them, and we're learning a lot more about timing of different kinds of sprays around their life cycle.

[00:33:17] Kent Daane: Yeah, what Houston was trying to do was to understand why parasitism against the Virginia creeper leafhopper was against all the leafhoppers. Why parasitism was relatively low. So I was working with Danny Gonzales and Sergei Tripitsin,

And just mentioning to the taxonomist, Sergei, that it seemed like there were differences amongst these Enneagris samples that we were releasing.

And I had happened to save all of the material that had died. So I sent that to Sergei, and Sergei looked at these things closely and then said, look, we've got a complex of parasites. And he named Enneagris erythronureae. After the species that was most commonly attacking variegated grape leafhopper, which is Erythronere variabilis. There was another one, and he called a Negris tryptocova, which was named after his wife's father's family and he said that was the better looking one of the group. And there was one that just didn't do that much. And he named that after me, a Negris Dana. And so that one we thought was the one attacking the western grape leaf hopper most commonly. And it was being found more commonly in the riparian zone. So that's 20 years ago, fast forward to our new invasive leaf hopper, the Virginia creeper leaf hopper, which is again coming down from Canada to Washington to Oregon to California. Well, it ends up that the Enneagris deni is very important attacking that leaf hopper.

So Houston was working out the relationship of these three parasites against these three leaf hoppers and trying to understand if he could manipulate their numbers to improve biocontrol. He looked at hedgerows, he looked at augmentative releases or inoculative releases, and we're still curious to see if that can't be improved even.

[00:35:30] Craig Macmillan: That's fantastic. Another topic that I wanted to touch on, because it's a really cool idea, and I think we'll have applications across a lot of things eventually, and that is area wide pest management strategies. And I know that you've done a lot of work in this area from the beginning, really, of kind of the concept.

What is an area wide pest management strategy? Management program. What does it look like? What can it what is its goal? How does it operate? What kind of success we've seen so far?

[00:35:59] Kent Daane: Yeah, that's a fantastic question. It's a topic I'm really excited about and let's think about it when we think about the European grapevine model. that was another invasive insect,

It was found in California, it was found in Chile around the same time. So you've got this invasive insect, and the state of California deemed this important enough to have an eradication program.

[00:36:22] Craig Macmillan: Oh and just real quick. What kind of damage does grapevine moth do?

[00:36:26] Kent Daane: So the European Greenvine Moth it'll feed on the vine, but it gets in the fruit clusters. think of the omnivorous leaf roller One of those, one of our tortricid pests that can really cause damage to the grape a number of generations per year, a lot of different possibilities where it might come from in terms of a host plant material.

So it can be very problematic. It would require a spray every single year, an additional spray for a tortricid pest, if it were to establish.

[00:37:00] Craig Macmillan: one the big issue here is that it attacks the berries directly

[00:37:03] Kent Daane: absolutely.

[00:37:04] Craig Macmillan: Okay. So that's a, that's a serious problem.

[00:37:07] Kent Daane: No, no, the, it, it causes mold and rot and everything else once it gets in there. So, you know, two or three doesn't seem like a lot. You just think, well, berry can go to crush, but that berry will get all kinds of bunch rot.

not a good fruit. So when you think about the eradication program, where there was monitoring everywhere in the state. When you think about the eradication program, where when they found this pest through pheromone traps, and then they did a ground search to find out where it was. And then there was a coordinated investigation. Effort to spray the right materials, to use mating disruption, to go after it in all of the adjoining areas. those eradication programs are very intense. Area wide control programs.

So, let's think about Vine mealybug, which is now in most vineyards. We're still approaching this on an individual grower basis.

We might have one grower using mating disruption, because they're going to go organic, and a next door neighbor doing nothing. There's going to be constant movement of that pest into that grower's. field We might have two growers, one using Movento every other year, and another using Platinum every other year. Those males are going back and forth between those vineyards, sharing whatever genetic resistance that they're developing.

And so really, if those growers are switching, one's using Movento, one's using Platinum that insect is moving between those vineyards all the time. And it's not a resistance management program,

or you might have a small five acre grower deciding to put out mating disruption. Mating disruption works better blanketing the whole area. So an area wide program, and then you bring into it the idea of roguing leaf roll diseased vines.

there are two things I just mentioned in this last 30 seconds that are so important for area wide management of mealybug and leaf roll that are the killers to those programs.

The first is mating disruption still costs more money than a pesticide application. It's a fantastic tool. It is a tool that works better the lower and lower the mealybug density gets.

So you use insecticides to really drop the mealybug population down, but there gets to be a point where the mealybugs are now on the bark. There are little populations here and there, and we know the insecticides are never 100 percent. Mating disruption works better. The lower the milli buck density is.

[00:40:05] Craig Macmillan: Got it.

[00:40:06] Kent Daane: But there's a cost to it. So we start with insecticides. The next part is the rowing of the infected vines.

That's very important on an area wide basis because if you're planting, you've had, vineyard is old, it's not productive, it's had leaf roll. You pull it out, but it's right next to a block that's got 80 percent infected vines. You're always going to have new infections showing up over and over and over again.

Unless that grower next to you is just doing this bang up job of applying insecticides all the time to keep mealybugs from going into your vineyard. you can make area wide control work for the pathogen. and the pest.

But in the best world, let's say you're in control of a thousand acres, pull out every vineyard that's infected and replant and then pull out every new infection in it. And people just can't afford this.

[00:41:06] Craig Macmillan: Right.

[00:41:07] Kent Daane: if you're managing 200, 300 acres and Your vineyard with leaf roll that's at 30 percent is still profitable. it's hard to pull out those 30%.

It's just hard to do. I get it. But something that I wish we could get, you know, government subsidy for to, to have them help us come in, pull out the infected vines, start clean again. But it does work. It's worked in South Africa. It's worked in New Zealand. It's worked in Napa. It just comes at a cost that may be prohibitive in some regions, in some areas. So the best we can do is to manage mealybug and the disease incidence in an area wide manner.

[00:41:52] Craig Macmillan: if I remember correctly, I mean, the work has been done now that, demonstrates roguing is your best strategy overall long term, but it's expensive short term. and that is the issue. That's the tricky bit.

[00:42:06] Kent Daane: There are two tricky bits to it. The first tricky bit is the expense you just talked about. The second tricky bit is that in most of the regions where we know it's worked They have not been dealing, perhaps, with our vine mealybug. They've been dealing with the grape mealybug, long tail mealybug, obscure mealybug. we've got I think the worst mealybug. And maybe that mealybug is just better at surviving on root remnants.

You know, you hear all the time from growers, I r I've been removing 10 percent of my vineyard every single year for five years. And when I looked at The south African data, they removed 20%. Second year, 5%. Third year, 3%. Fourth year, 1%. And after that, it was always 1%.

[00:42:54] Craig Macmillan: last piece of this puzzle in my mind is you have to get your neighbors to cooperate. That's the area wide bit. You have to get people to get on the same page in terms of what they're doing. And it sounds to me like they don't necessarily have to be doing exactly the same thing. They just have to be sensitive to what somebody else wants to do.

Does that sound right?

[00:43:15] Kent Daane: There are areas where it has worked well. It can work in the Central Coast. It can work in Lodi. We may not see, you know, eradication of diseased vines. We may not see a reduction of vine mealybug to a point where we can treat every other year. We might be treating every single year. for this, but we can improve what we're doing through communication right now.

In the central Valley, we're working with a great group of growers where we're just mapping out the vine mealybug and we're sharing with the growers where the melaybug populations are. It's their decision. What? What to use, what to do for control. It's their decision. Can they rogue or not rogue?

But what we're trying to do is to help foster communication amongst the different growers that are neighbors, because we're a third party, which I think helps a little bit. it would be fantastic if we could have someone hired as a scout or PCA, where we work with. PCAs in the region and everyone shares data. We're trying a new computer program this year, which we at the end of the season, we'll launch with our collaborating growers where they can log on in real time. and see what the trap counts are as we count those trap counts. And that will help them make a decision, we hope, on what to do in terms of control measures. But again, the best thing might be that we're opening up communication, just as the Vineyard team is doing through podcasts, through field days, through the website.

[00:44:55] Craig Macmillan: Well, let's hope. And I, and there's a number of other organizations too. the, the group in Lodi has done a fantastic job from what I understand. Fostering communication and sharing information. like you said, I think that's probably one of our, our, our best hopes. Is working collaboratively as an industry and getting communication between the experts like PCAs and the extension community. .

[00:45:15] Kent Daane: And of course, anyone can always reach out to me with questions as well.

[00:45:18] Craig Macmillan: Fantastic. And we'll put your information in the show notes. I want to thank you for being on the podcast. fantastic. Very helpful and very, very exciting. I think I was feeling a little more dismal about this whole topic coming into this interview than I am now. I think there's maybe more potential than I was kind of giving credit.

I, you know, I come from a time back in the 90s when Vine Mealybugs showed up in the Central Coast. And it was a lot of gnashing of teeth and pulling of hair, and we did not know what to do, and the damage was insane. I mean, I saw stuff that was just blood curdling, and I think we've come a long way.

We've come a long way, and that's from the efforts of folks like you, so I really appreciate it. I want to thank our guest, Kent Daane. He is a Cooperative Extension Specialist with the University of California, Berkeley. he works primarily out of the Kearney Ag Research Extension Center. And, thanks so much for being on the podcast.

This is great.

[00:46:10] Kent Daane: Thank you very much. Enjoy the harvest time coming up.

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