by Andrew Chalk
How many bats do you want in your vineyard? That is a question that has exercised Xavier Buffo, General Manager of Château de la Rivière in the Fronsac AoP of Bordeaux, and Anne Biscaye, owner of Château Lapelletrie in Saint-Émilion, AoP. They know the answer, with the help of researchers who found the average bat consumed 2,000 insects each night. The insect that occupies their attention is the grapevine moth (also called Eudemis or Cochylis) which is a pest that encourages the botrytis bunch rot in grapes.
At Château Lapelletrie Anne Biscaye has established conditions in which the bat population can thrive and, in particular, feed itself outside the grapevine moth season. Bat boxes dot her property.
Château de la Rivière has been a Natura 2000 site for the maintenance and protection of bats since 2006. Both producers have eliminated the use of the insecticides previously used to control the grapevine moth.
I asked Anne and Xavier about the use of bats at their Châteaux:
1) When did you start working with bats as part of the ecology of your Château?
Xavier: Bats have been living in the Château de La Rivière since the underground cellars were dug in the 19th century. But it's only in the last 15 years that we've been really concerned about them
Anne: There have always been bats in our countryside. But in Lapelletrie, we started observing them in 2017 in partnership with the Bird Protection League which studies them.
2) What first inspired you to invest in this rather than other avenues of pest control?
Xavier: I became interested precisely because there was no need to invest. Just understanding and caring.
Anne: Ensuring that bats feel good in our vines does not require a financial investment. And that is always nicer than working with products even if they are organic. We have just modified the organization of certain work in the vineyards.
3) Which specific types of moths (or other insects) do bats contain?
Xavier: It has been proved that bats eat Eudemis and Cochylmis, which are moths that are harmful to vines.
Anne: European bats mainly eat flying insects. Their preferences depend on bat species. Studies have shown that some bats adore Eudemis (butterflies that can cause damage in grapes).
4) Do they control any other species?
Xavier: Yes of course, like mosquitoes for example.
Anne: I don’t know so far.
5) What type of bats and how do you get them?
Xavier: The cellars of the Château de La Rivière are home to 10 different species of bats out of the 13 that exist in the region.
Anne: There are between 5 and 7 different species at our Château, it depends on the season and the years. We only make observations of population and not of reintroduction of individual species. So we do not choose our species.
6) Are there any negatives of having bats in the vineyards?
Xavier: There is absolutely no problem with having bats in the vineyard. On the contrary. It is a very beautiful representation of biodiversity.
Anne: For the moment, I have not noticed any negative aspect to the presence of bats in the vineyard.
7) How have you assessed (measured) the success of this experiment?
Xavier: We participated in a scientific experiment for 3 years. The objective was to quantify and count bats, and to measure their presence at night in the vineyards. Then it was necessary to prove that they ate the harmful butterflies. This was proven by analyzing bat droppings which contain the DNA of the moths.
Anne: We have had the Eudemis for almost 20 years. We have always had low population rates. I can't certify that it's only because of the bats but I think so. Maybe the technicians of the Bird Protection League have quantified studies.
Xavier and Anne’s findings are likely to be important to other grape growers in Bordeaux and beyond, and possibly for farmers of other crops. In particular the low costs and moth consumption date. Moth damage is a global pest problem for grape growers and bats may offer a more effective, economic, and less invasive alternative to chemical insecticides in combating this pest.
