Best Bets for Brown Garden Snail Management

Brown garden snails (Cornu aspersum) can reach incredible population densities in California citrus orchards if left unmanaged. More than 1,000 snails per tree have been documented in some cases, according to Mark Hoddle, University of California, Riverside biological control specialist.

To help growers deal with this problem, Hoddle recently participated in a Citrus Research Board webinar. He presented information on biology and management of the brown garden snail.

Hoddle said increased use of pre-emergent herbicides/no-till weed control may have increased snail populations because the soil is not disturbed. Therefore, nests with snail eggs and adults on the ground are not destroyed.

While the pest may be of little significance in drought years, outbreaks are observed in high rainfall years, especially when there are warm spring rains, noted Hoddle.

Young trees are at risk of significant foliar damage from snail feeding. Fruit damage can range from 40% to 90% due to snails feeding on the flavedo, Hoddle added.

CHEMICAL CONTROLS

Hoddle recommended applying baits containing metaldehyde and iron chelates (sodium ferric EDTA and iron phosphate) spread on the ground under or between tree rows when snails are active. He advised that small pellets offer better efficacy, and that bait applied to the edge of the canopy draws snails out from moist areas and increases mortality due to desiccation.

Various molluscicides can also serve as chemical control options, in accordance with manufacturer recommendations.

CULTURAL CONTROLS

Hoddle said a key cultural control is prevention — keeping snails out of new plantings.

Trunk barriers in the form of copper or plastic shields placed below scaffold branches at least 12 inches wide and out of the sprinkler zone can be a highly effective strategy.

Another cultural control Hoddle mentioned is skirt pruning to prevent snails from moving from the ground to the canopy. He also recommended weed and debris management under trees to remove favorable snail habitat.

Hoddle said the decollate snail has been observed as a predator of the brown garden snail but has not been proven as an effective biological control. He summed up his presentation by advising that an integrated approach using a combination of chemical and cultural controls is a grower’s best bet for managing brown garden snails.