Cuban brown snail, Zachrysia provisoria (Gastropoda): Damage potential and control

The snail Zachrysia provisoria (Pfeiffer) is poorly known in Florida, USA, where it predominately is viewed as a pest of ornamental plants. I evaluated its host plant relationships, foliage consumption potential, and susceptibility to several molluscicides. Many of the potential hosts, especially common ornamental plants that are planted densely as ground cover and might be expected to provide a favorable environment for snails, are not suitable for growth of young snails. Older snails, though displaying some ability to feed and damage hosts unsuitable for growth of young snails, displayed similar patterns of acceptance and growth. Several weeds were favorable for growth, suggesting that untended environments could lead to snail problems in adjacent ornamental plantings. The effect of plant condition (age) on snail feeding preference was assessed by measuring leaf consumption by snails presented simultaneously with young (green, located apically) and senescent (yellowing or yellow, located basally) leaves of a single plant species. From preferred host plants, snails chose young leaf tissue, but from less preferred plants they consumed senescent tissue. Foliage consumption potential was assessed using romaine lettuce at two constant temperatures, 24 and 32 °C. Foliage consumption increased with age (wet weight) at both 24 and 32 °C; however, the rate of consumption was higher at the lower temperature. At 24 °C, mean peak consumption was about 40 cm2 of leaf area or 12 g wet weight/day. At the less favorable high temperature of 32 °C, mean peak consumption was reduced by about 50%, to a mean of only 20 cm2 or 6 g wet weight/day. Relative consumption rate (cm2 or g foliage/g snail) diminished with age (wet weight) of the snails. Several molluscicide-containing baits were assessed. Metaldehyde-based baits induced mortality most quickly, followed by iron-based baits. A boric acid-based bait was slowest, requiring 12 days for the induction of significant levels of mortality. All baits significantly suppressed feeding, however, sometimes even in the absence of mortality.