Wednesday, June 1, 2016

Scout Soybeans for Slug Damage

Some recent fields visits within the Northern Burrus footprint have shown indications of slug damage to soybean fields. Some scouting at dusk revealed signs of slugs in emerging soybeans at the end of May. 

Slugs are very delicate animals that can desiccate rather easily. They actually are little more than moist flesh folded over itself. Moisture and cool temperatures are therefore essential for slug populations to thrive.  Temperatures ranging from the 60s to the 70s with high relative humidity create the ideal environment for these members of the mollusk family. The need for moist conditions also explains why slugs prefer fields with abundant residue. Residue provides a moist microenvironment which once again allows adult slugs and their eggs to persist. When conditions become unfavorable, many slugs will die and others will go into an inactive state.
Soil moisture may keep seed slots open allowing high slug populations to inflict more stand-reducing injury. They do their damage with a tongue-like appendage that is very abrasive. Slugs may be able to reach the seed and/or growing point. Both are usually below ground with the growing point, moving above ground only later. Slugs grind long streaks or holes in leaf tissue giving that tissue a “ragged” appearance. They are usually deemed the culprit because they leave slime trails on ragged plants and on the ground surrounding ragged plants.
The heat should stop slugs, but we are still visiting fields in Mid-June and evaluating their feeding on leaves and stems:

If slug issues occur often within fields with heavy residue, row cleaners, strip till, and ensuring the seed slot is closed after planting may be some other management options.  Planting early and shallow disking may also help to defeat heavy slug pressure.  Pesticides or slug baits such as metaldehyde or iron phosphate can be used, but may not be economical and washed away from heavy rain.

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