Checking slug traps in a field.

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The Pennsylvania Slug Project is back for another year as part of the Soybean On-Farm Network, funded by the Pennsylvania Soybean Board. Penn State Extension educators throughout the state are beginning to monitor for slugs and will regularly share their observations and the risk posed by slugs to no-till crop fields in this newsletter. This year, we are trying to collect data early and focus our efforts on the gray garden slug. Our goal is to develop a model to predict when gray garden slug egg hatch occurs in the spring and provide information on slug outbreaks and risk across the state.

As planting gets started and progresses, be prepared for slugs if there are wet, cool conditions. Four slug species can be encountered in Pennsylvania field crops and are monitored in our project. See our Slugs as Pests of Field Crops fact sheet for more details. If you want to deploy slug traps on your farm, check out our Scouting for Slugs in Field Crops video.

Slug Management

Our research indicates that managing slugs requires an integrated pest management (IPM) approach that should be planned well before the spring planting season. The most diverse rotations tend to experience the fewest slugs, and adding cover crops can increase rotational diversity. Our research also shows that higher ground beetle populations can help suppress slug populations. Populations of these beetle predators are reduced by insecticide use, including broadcast applications and insecticidal seed coatings.

For tips on how to manage slugs in the spring, see our article on Best Management Practices at Planting to Reduce Slug Damage. If you are monitoring slugs with refuge traps and average 1–2 slugs per trap, and, there is severe slug feeding damage or dying seedlings, a slug bait is justified. Slug baits are most economical as a rescue treatment in portions of fields that are experiencing severe slug infestations. These baits can be ineffective, especially when it rains.

Week of May 12, 2026

Slug numbers remained low in all counties. A mix of juvenile and adult grey garden slugs is still being found; however, most slugs reported are juveniles. No marsh slugs were reported. Slug eggs were found in Butler County.

An image of Pennsylvania with counties highlighted in blue that participated in slug trapping. Slugs in low numbers were found in Columbia, Butler, Indiana, Franklin, and Lancaster Counties. — May 11-12 PA county map. Average grey garden slugs captured from May 11-12. The number on the left indicates the average grey garden slug count per trap; the number on the right indicates the total number of traps set up in that county.

Week of May 5, 2026

Slug numbers increased, but numbers remained low. There was a mix of juvenile and adult grey garden slugs reported. No marsh slugs or slug eggs were reported.

An image of Pennsylvania with counties highlighted in blue that participated in slug trapping. Slugs in low numbers were found in Butler, Centre, Dauphin, Franklin, Indiana, Montgomery Counties. — May 4-7 PA county map. Average grey garden slugs captured from May 4-7. The number on the left indicates the average grey garden slug count per trap; the number on the right indicates the total number of traps set up in that county.

Week of April 28, 2026

Slug numbers continued to decrease this week as soil remains dry. Any counties reporting slugs this week found a total of 1 grey garden slug across all traps. A small grey garden juvenile was found in Montgomery County. All other grey garden slugs reported were large adults. One marsh slug was reported in Lancaster County.

Map of Pennsylvania with participating counties in blue. — April 27-28 PA county map. Average grey garden slugs captured from April 27-28. The number on the left indicates the average grey garden slug count per trap; the number on the right indicates the total number of traps set up in that county.

Week of April 21, 2026

Slug numbers decreased this week. All counties were reporting an average of less than one slug per trap. Most of the grey garden slugs observed were large adults. Small juveniles were found in Butler and Franklin Counties, indicating that slug eggs are starting to hatch. Slug eggs were also found in Butler County. No marsh slugs were observed this week.

Map of Pennsylvania with some counties highlighted in blue — April 20-21 PA county map. Average grey garden slugs captured from April 20-21. The number on the left indicates the average grey garden slug count per trap; the number on the right indicates the total number of traps set up in that county.

Image of a grey garden slug next to a group of slug eggs with a pen tip next to the eggs for size reference — Image 1. Grey garden slug next to slug eggs in Butler County (Image Credit: Stephen Campbell).

Week of April 14, 2026

Slugs are starting to appear and have been observed in multiple counties. With the exception of Centre County, all counties were reporting less than one slug per trap. All of the grey garden slugs were large adults, indicating that they overwintered. Marsh slugs were also noted in Centre and Lancaster Counties.