Pesky pest

Vintner Hubert Pauly combs through the vines on his land in the Ahr valley, a paradise for red wine in Germany. Pauly is on the lookout for grapes blighted by the grapevine moth - a pest of serious concern for grape growers. "Normally, when you spray the fields with pesticide you take care of the problem. Then you just have a grapevine moth now and again," Pauly says.

On the vineyards dotting the slopes of the picturesque Ahr valley, the grapes are nearly ripe. Pauly lets his hand glide over the vines. To his relief, there's no sign of the fruit-filching bug. He plucks a few shriveled grapes that are split open on the side. "This here is from the hail but the destruction caused by the European grapevine moth looks similar," he says.

There are two types of wine moth, known scientifically as lobesia botrana, and both are some of the worst enemies of grape growers. They have a similar reproduction cycle - once the adult moths have mated, the female lays her eggs on the vines. The larvae that emerge burrow into the grape and feed on the fruit pulp. They pupate and finally morph into adult butterflies. This cycle is repeated by each moth type two to three times a year.

Pauly explains that it's not the larva itself that's the problem. Rather, the damage it causes to the grape opens the door to all kinds of viruses. "The grape then begins to rot and all the other grapes around it are affected too," Pauly says. The grape-chewing bug can cause significant economic damages.

Confuse rather than kill

This year, however, grape growers have gained the upper hand with vineyards in the Ahr valley practically free of the dreaded pest. "In August we went along the rows of grapevines together with specialists to see just how much infestation there is," Pauly explains. "And in a huge area, we only found two small worms where you would normally find hundreds."

So, what's the secret to their success? The answer lies in brown, plastic pipes - about seven centimeters long - which are hung in the grapevines every few meters. The devices emit synthetically created female pheromones into the air, creating a cloud of fragrance over the vineyard.

The sex pheromones are an important factor in mating in moths. Once the female releases chemicals, it triggers the mate search and the male moths begin their upwind motion toward their potential partner. But with the devices all emitting female pheromones, they trick the males into a fruitless search for sex that ultimately results in death.

An eco-friendly solution

"It's a substance that the pests produce themselves," Karl-Josef Schirra, a pest control expert in the wine industry says. The good thing, he adds, is that it's a very selective method. That means the pheromones of both types of grapevine moths only react to the odor of their respective species so there's not much that can go wrong.

"Even other organisms are immune to it," Schirra explains. "So pheromones have a positive impact on the entire fauna in the ecosystem of the vineyard." According to him, about 80 percent of the winegrowing area in the Rhineland-Palatinate, where the Ahr Valley is located, is now covered by pheromones.

Others point out that they have the potential to edge out toxic insecticides that are still used by grape growers.

"In the 1990s, we tried to fight the grapevine moth with ME 605, a really extreme kind of poison," Steffen Christmann, president of the Association of German Quality Wine Estates, in the Palatinate region remembers: "and even then, we only managed to get about 60 to 70 percent of the pest," he says. Grape growers also need to spray insecticides several times a year at exactly the point where the female moth begins to lay eggs.

The success rate of the pheromone method lies at 99.9 percent, Christmann says, "and that in a totally natural and organic manner."

Pulling together

Synthetic grapevine moth pheromones have been on the market since the 1990s. But, it's often difficult to use them on a mass scale over a large area. Another downside is that they are about 20 to 30 percent more expensive than using insecticides. "It costs about 250 euros per hectare," Christmann says. "Spraying is a bit cheaper."

In order for it to work, it's not enough to just equip the vineyards with the pheromone devices. Even surrounding forest areas, for instance, need to be covered. Otherwise, the moths can easily mate outside the vineyard and the female can lay her eggs on the vines oblivious to the pheromone devices. For exactly that reason, all wine growers in a region need to use the method.

"It's about creating a cloud of fragrance and everyone needs to pull together," Hubert Pauly says. That's easier said than done. But Pauly says this year all the vineyard owners in the Ahr valley have decided to join forces and opted for the pheromone method instead of insecticides.

The strategy seems to be working. But Christmann warns that even if one grape grower decides to opt out, the whole community can suffer. "We have a community in the Palatinate region where the grape growers could not agree on the pheromone method," he says. "Last year, they had to struggle with huge damages and crop losses of up to 40 percent."

"No man is an island," English poet John Donne once wrote. That apparently applies just as well to keeping out pests on vineyards.