|The Tardis (photo by Zir, Wikimedia Commons)|
|Dalek image by Nelo Hotsuma from Rockwall [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]|
|Lobesia: European Grapevine Moth image by Jack Kelly Clark, University of California Extension|
Now the thing is that this wasn’t just another moth. The caterpillar stage of this bug would do a lot more damage to the grape clusters than the other moth species and that would mean nice things like “frass” or insect poop on the grapes or later the raisins. To make matters worse, the feeding opens the way for fungi that rot the grapes and that kind of infection can spread from berry to berry throughout the cluster. This would make it a lot harder for the raisin growers to have a high quality product, it would mean a lot more food waste even all the way to the consumer level for the table grapes. Moldy grapes definitely don’t make for high quality wine!
|Rotting grape image by Andrea Lucchi, University of California|
Now of course there wasn’t an extraterrestrial “Doctor” to lead this campaign, but even Dr. Who drafts a team of regular humans to help defeat the aliens.
In this case the team comprised representatives of the grower communities, university experts and government employees from the relevant state and federal departments. They held an emergency meeting and decided that they wanted to see if they could come up with a way to not only stop the spread of the pest, but if at all possible to completely eradicate it from California. Eradicate! Doesn’t sound quite as harsh as “exterminate!” but it’s essentially the same idea.
In order to see what they were up against, sixty thousand “Sticky traps” were distributed state wide at a density of 39 per square kilometer in vineyards and 10 per square kilometer in residential areas. In the next 2010 growing season they found 100,000 moths in several California counties. This was going to be a big challenge! Only a comprehensive strategy with broad participation would give any hope of winning. So the team developed a multi-prong strategy:
Those sticky traps continued to be used to monitor progress, but they were careful to use red colored traps because they are much less likely to accidentally trap honeybees.
It was important to find ways to limit further spread of the aliens. The adult moths can fly, but they don’t tend to fly too far as long as they can find the grapes they want. Quarantine rules were set up to prevent fruit, farm equipment, recycled fence or grape posts, or other things that might allow the pest to hitch-hike long distances. It turned out that the moth larvae could survive the stemming and crushing and even pressing of wine grapes – so it was critical not to move around those by-products of the winemaking process.
They also used an approach called “pheromone confusion” that was set up on an area-wide basis where the Lobesia had been found. This involves putting up emitters of the specific sex hormone for this moth so that the males are getting so many “scent trails” that they rarely actually find a female to actually mate.
There were lots of outreach programs to get everybody up to speed on the situation and to know their role. This included grape growers, wineries, and fruit or raisin packers, and pest control advisors. The outreach also had to include on the order of 3,000 homeowners because they also needed to cooperate, especially if they had backyard grapes, as many did. The coordinated task force would help those owners to treat their grapes or remove their fruit so that they didn’t become a reservoir to then fan out into the commercial vineyards. Not only were there public meetings to reach all these groups, there was a Facebook page and a website at www.bugspot.org.
The researchers developed a sophisticated “degree day model” to predict when each of the 3-4 new generations of moths would be coming out so that insecticide sprays could be timed just right, not only to protect the crop, but to prevent the moth numbers from really blowing up as they would if not strategically checked this way. Almost all of this spraying was done on a voluntary basis at the grower’s own cost. In Napa and Sonoma in 2012 the growers treated more than 12,000 acres. The organic growers also sprayed using the insecticide options that are allowed under their rules.
The combination of the quarantines, the pheromone confusion and the well-timed insecticide sprays achieved what is called an “allee effect” in population biology lingo. This is when the population size gets down to the point where there are too few of the pests in a given area to successfully mate.
|Historical progress towards eradication of EVGM from California. University of California.|
This massive, voluntary, cooperative effort was highly coordinated across the different counties of the state and it began to pay off. In 2011 there were 2,335 acres quarantined because of the presence of the moth. By 2014 that number was down to 446 acres. By 2016 the pest was officially declared to have been eradicated.
|Victory Lap! (University of California)|