Vineyard Snail Control

vineyard

Description

Throughout the world, vineyards cover around 8 million ha. Depending on location, grapes are grown for winemaking, table grapes and drying.

Historically, Europe has accounted for the largest share of vineyard area, with Spain, France, Italy and Portugal accounting for the majority of European production. Asia accounts for an increasing amount, with Turkey second only to China in vineyard acreage. South Africa has around 100,000ha under vine, one-tenth of the Spanish area, while New Zealand vineyards continue to increase their area, reaching 36,000ha in 2013.

Susceptibility to Slug Damage

Snails are significant vineyard pests. Typically, damage arises either through contamination (the snails being present on the fruit at picking) or, more likely, the snail having damaged the skin of the fruit, allowing fungal infection to take hold.

During summer, snails enter a period of hibernation known as aestivation, which last until the early autumn rains. Vines provide the snails with an ideal habitat for this process, the consequence being that they’re either in the vines at harvest, or beginning to feed on the grapes as they make their way back to the soil.

For control, growth stage of the vine is less important than the time at which bait is applied.

 

 

 

Species of Concern

The species of greatest concern to the vineyard owner are Helix aspersa, Theba pisana and Cochicella barbara.

Theba pisana can reach very high numbers; infestations of up to 200-250 snails per vine have been recorded (Sanderson, G. (1995) Snails in viticulture. Australian Grapegrower and Winemaker 378a, 115-118) and in one case, 87kg of snails were collected from vines yielding 30 tonnes of fruit.

Symptoms of Attack

Although contamination and fungal infection are the most common symptoms of snail damage, occasionally Helix aspersa will feed on growing buds and new foliage.
Severe snail infestations can also result in clogged sprinkler heads and water lines, reducing irrigation efficiency and adding to labour costs.

Solution

Controlling snails once they have started to move up into the vine canopy is almost impossible, as they will not return to the ground to feed on pellets.

So it’s important to control snails while they’re most active. If control measures are put in place before they start mating, greater reductions in population will be observed.

Although labour-intensive, manual removal of snails from vines and supporting posts can significantly help control the population.

If using pellets, the greatest effect will come from application during early autumn, after the initial rains, particularly if the soil beneath vines is kept clear of vegetation to remove alternative food sources. On-going applications during autumn and winter will continue to reduce populations further.