Slug Populations are on the Rise

Dr. Heather Darby, UVM Extension

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Continuous wet weather over the past 3 years presumably has led to a rise in slug populations. Slugs are a problem associated with fields with high amounts of crop residues. They like moist and cool conditions and primarily feed on crops after dusk and through the night. It is rare to see slug damage on hay and corn crops but over the last 2 years we have heard of several cases where field crops have been annihilated. You may not notice the slugs in the field during the day it is “the undercover crop pest”. They hide under residue and soil clods during the day and wait for the coolness of the night and crawl out to eat your crops. They leave a trail of slimy silvery white goo on the plants and the soil. The most typical species causing devastation to field crops is the grey garden slug (Deroceras reticulatum). Other less common species include the dusky slug (Arion subfuscus) and the marsh slug (Deroceras leavae). These slugs are common sights in corn and soybean fields, but not known to cause economic damage to field crops. Their damage looks as is hail has shredded the corn plants and eventually if the populations are high enough they eat entire plants. Generally fields that have high residue such as no-till and heavy weed populations are more likely to become inundated with slugs. Some plants can withstand 10 or more slugs per plant but others are more susceptible. Higher populations may warrant control or you can pray that it dries out. Certain management practices like tillage on a regular basis may help to reduce slug populations. Another management consideration is to alter planting dates prior to when slugs begin their heavy feeding or delay planting to when the soil has warmed and the slug populations have decreased.
Control of slugs with a pesticide is often difficult due to the slug’s ability to shed slime, simultaneously shedding the toxins.
For more information on scouting and control options please contact Dr. Heather Darby at the University of Vermont Extension at (802) 524-6501.

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