Italian White Snail on the Move in San Diego County
The Italian white snail aka white garden snail (WGS)(Theba pisana) has been in San Diego County for about 100 years. However, it has rarely caused significant damage to crops or gardens. Historically, it climbs up on weeds like mustards or fence posts in the day and during hot periods of the year and does not really move too far from abandoned fields or other relatively undisturbed areas.
In 20 years in my job here, I got a total of 1 call about it. However, about 6 weeks ago I went to a site in Escondido that bordered a weedy fallow field. That area had not been reported to have the WGS but they were clearly established there. The problem was that the snails had traveled to the adjacent property and were on almost all of the citrus and peach trees and groundcover. The avocado grove across the street was also impacted. WGS were on the tree trunks and leaves and this worried me more since they are not really a crop of choice for the more common brown snail. I thin drove down the street and observed small numbers of snails on walls and posts up to about 1/2 mile away. They are clearly expanding.
About 4 weeks later, I was at another small farm in Carlsbad and they asked me to the take a look at a snail problem. I expected it to be the brown snail and was shocked to it was also the WGS on their fruit trees. Even worse, that farm is next to cut flower growers who may be impacted not only from direct damage but restricted shipping since WGS is a B-rated pest.
B-rated pest (CDFA Pest Ratings): An organism of known economic importance subject to: eradication, containment, control or other holding action at the discretion of the individual county agricultural commissioner.
An organism of known economic importance subject to state endorsed holding action and eradication only when found in a nursery.
I am in the process of writing an advisory for ornamental plant growers. I am also doing some limited tests to see what can be done to reduce its impact. However, I wanted to get this out ASAP so people can be on the lookout. If you see it drop me a line here of by email (email@example.com). I am very concerned that this snail will have a bigger impact on production and landscapes than the brown snail.
Description: White or light tan, about the side of a dime or nickel when full grown (sorry - I only had a quarter when I took the photo). May or may not have brown markings on the outside. Inside shell color of opening is light colored (milk snail looks similar but has a dark inside shell).