A Rare Snail Outbreak During Drought Affecting Soybeans

On a farm in Lyon County, a study was being conducted to evaluate the management of slugs in soybeans. By mid-May, a couple of slugs were found, and a laboratory colony was started.

However, the slugs in the field vanished due to drastic environmental conditions (absence of rains and temperatures above 85⁰ F). Later on, the farmer complained about soybean plant damage in some areas of his farm. Plants with at least two to three true leaves were completely destroyed, leaving blank spots in the field (Figure 1). At first, it was hard to believe that mollusks could be the cause of this damage, especially when the area has been experiencing a drought period and warmer temperatures; however, they were. In this case, the perpetrators causing this damage were snails.

Pest Description & Damage

Figure 2. Between 10 and 80 snails per 2 square feet were found under stalks, husk, and cobs of corn planted the previous season. (Photo: Raul T. Villanueva, UK).

Snails differ from slugs by the presence of the spiral shell that is carried on their back. The shell is a hard structure composed of calcium carbonate, which protects the soft body and internal organs. Slugs and snails do not have legs. However, snails have a “foot” that allows them to move and slide along easily with the help of the mucus it secretes. Snails can live up to 2 to 3 years. As this is a work in progress, UK entomologists have not identified the snail species yet and are conducting studies to understand this type of presence in soybean fields planted after corn.

Management

There is no curative control for slugs or snail damage. Populations may be reduced with vertical disking to decrease the amount of organic matter left by corn. Replanting soybean is one of the solutions conducted by some farmers. There are molluscicides used to control slugs as a preventative tool. These are metaldehyde or iron phosphate-based products. Due to the high numbers, UK Entomology is testing different types of molluscicide formulations and baits to manage this pest, as well as running some bioassays to conduct further evaluations.