SlugNet: 2025 Wisconsin Slug Monitoring Project

Welcome to the inaugural year of the SlugNet project in Wisconsin, a new initiative aimed at monitoring slug populations across the state. This effort uses a citizen science approach, relying on the valuable contributions of participants throughout Wisconsin to collect data on slug populations in field crops, with a focus on conservation cropping systems (e.g., reduced tillage, cover crops).

UW-Madison Extension and external partners are tracking slug activity to identify patterns in their emergence and damage. The project’s goal is to understand the key factors that lead to severe slug outbreaks so we can help farmers take preventive steps—especially since current chemical control methods are limited and often don’t work well. As planting gets underway, be prepared for slugs if there are wet and cool weather conditions.

See Most Recent SlugNet Counts

The team will be regularly sharing updates on slug counts from participating counties and observations of feeding damage in this weekly article. In the first year of the project, the team is excited to gather as much data as possible.

Slug Management Resources

Visit our partner, the Bick Lab, for more field crop insect pest information

For more information on slug management, read Managing Slugs in Wisconsin Field Crops

To see count updates and get involved, visit the SlugNet website

For those interested in helping us understand slug activity in Wisconsin crop fields, there’s still time to get involved! Visit the SlugNet project website for more information about the project’s goals, protocols, and how to participate in slug monitoring. Thanks to all volunteers who are already monitoring traps for slugs!

See our Managing Slugs in Wisconsin Field Crops article for more information on slug pests in Wisconsin.

See Most Recent SlugNet Counts

Weekly Slug Trapping Data for Wisconsin Farmers

Week of May 18 – 24

Slugs were captured in Dane, Fond du Lac, Ozaukee, Sheboygan, Marathon, and Chippewa Counties. Each county reported less than one slug per trap (Figure 6). Slime trails, but no slugs, were present on shingles in Winnebago County suggesting that slugs are present in those fields. Four counties did not report.

Keep an eye out for slug feeding damage on early emerging plants. At this point in the season, we have 15 counties participating in the first year of the SlugNet project monitoring a total of 145 slug traps across the state. Thanks to all volunteers! We will continue to update slug numbers as the season continues.

Wisconsin map with counties shaded red, labeled with two values like “0.1, 10” or “NR, 6”. — **Figure 6.** Average slugs captured from May 18 to May 24. The number on the left is the average slug count per trap; the number on the right is the total number of traps established in that county. NR indicates no data were reported for that county during the monitoring time frame.

County	Average slug count per trap	Total traps in county
Calumet	0.33	3
Chippewa	0.1	10
Dane	0.06	36
Fond du Lac	0.12	17
Grant	0	7
Iowa	0	3
Kewaunee	0	6
Marathon	0.2	5
Marinette	NR	1
Oconto	NR	8
Ozaukee	0.5	4
Rock	NR	2
Shawano	NR	6
Sheboygan	0.06	3
Winnebago	0	13

Table of slug trap counts for the week of May 18–24. NR indicates no data were reported for that county during the monitoring time frame.

Week of May 11 – 17

Slugs were captured in Grant, Fond du Lac, and Sheboygan Counties. Each County reported less than one slug per trap (Figure 4). Planting made big gains this week, so several traps were removed from fields temporarily to allow for field operations and five counties did not report this week (NR). Slug pressure remains low throughout the state, especially compared to 2024. Late May probabilities are showing a likelihood for cooler-than-normal temps and a lean towards near-normal precip.

Some crops have emerged, and with cooler-than-normal temps, seedling growth may be slowed. Slow growing seedlings are at a higher risk for slug damage, so make sure to take note of any potential herbivory, especially on soybean seedlings. See our Managing Slugs in Wisconsin Field Crops article for pictures of slug feeding damage on soybean seedlings.

Two slugs circled in red on a black shingle trap among dried corn husks and stalks. — **Figure 5.** Slugs on the bottom of a shingle trap in Grant County. Photo: Kory Stalsberg

Map of Wisconsin with counties shaded red or pink. Darker counties trapped more slugs. — **Figure 4.** Average slugs captured from May 11 to May 17. The number on the left is the average slug count per trap; the number on the right is the total number of traps established in that county. NR indicates no data were reported for that county during the monitoring time frame.

County	Average slug count per trap	Total traps in county
Dane	0	36
Fond du Lac	0.2	17
Grant	0.3	7
Iowa	0	3
Kewaunee	0	6
Marathon	0	5
Marinette	NR	1
Oconto	0	8
Ozaukee	NR	4
Rock	NR	2
Shawano	NR	6
Sheboygan	0.33	3
Winnebago	NR	13

Table of slug trap counts for the week of May 11–17. NR indicates no data were reported for that county during the monitoring time frame.

Week of May 4 – 10

Slugs were captured in Dane, Winnebago, and Grant Counties. This is the first slug capture report from Grant County. Each county reported less than one slug per trap (Figure 3). Slime trails, but no slugs, were present on shingles in one Shawano County location suggesting that slugs are present in that field. Marathon, Ozaukee, and Kewaunee Counties submitted their first data reports this week. Traps from Sauk, Chippewa, and Calumet Counties will be coming online soon.

Slug pressure remains low throughout the state. Probabilities for May are leaning towards warmer and drier weather, which should reduce slug activity and minimize potential feeding damage to any emerging crops.

Map of Wisconsin showing slug presence data by county, with varying shades of red indicating different levels of slug presence. — **Figure 3.** Average slugs captured from May 4 to May 10. The number on the left is the average slug count per trap; the number on the right is the total number of traps established in that county. NR indicates no data were reported for that county during the monitoring time frame.

County	Average slug count per trap	Total traps in county
Dane	0.16	36
Fond du Lac	0	23
Grant	0.6	7
Iowa	0	3
Kewaunee	0	6
Marathon	0	5
Marinette	NR	1
Oconto	0	8
Ozaukee	0	4
Rock	NR	2
Shawano	0	6
Sheboygan	0	18
Winnebago	0.08	13

Table of slug trap counts for the week of May 4–10. NR indicates no data were reported for that county during the monitoring time frame.

Week of April 27 – May 3

Slugs were captured in Fond du Lac, Winnebago, Oconto, and Shawano Counties. Each county reported less than one slug per trap (Figure 2). Slug eggs were found in Dane County.

The map shows slug distribution across Wisconsin counties. One county (Oconto) in red has high presence (0.75 slugs/trap, 8 traps). Pink counties show lower counts. Gray counties have no data. — **Figure 2.** Average slugs captured from April 27 to May 3. The number on the left is the average slug count per trap; the number on the right is the total number of traps established in that county.

County	Average slug count per trap	Total traps in county
Dane	0	36
Fond du Lac	0.09	23
Grant	0	7
Iowa	0	3
Marinette	0	1
Oconto	0.75	8
Rock	0	2
Shawano	0.17	6
Sheboygan	0	18
Winnebago	0.08	13

Table of slug trap counts for the week of April 27 – May 3

Week of April 20 – 26

This is the first slug monitoring update of the 2025 season. Slug trap data have been reported from multiple Wisconsin counties (Figure 1). Traps from additional counties (Sauk, Chippewa, Calumet, Ozaukee, Rock) will be coming online soon. Few slugs have been reported so far this year (less than one slug per trap), and only in Dane and Fond du Lac counties. Juvenile and adult slugs were found in each county. This suggests that some adults successfully overwintered and some eggs have begun to hatch. Slime trails, but no slugs, were present on shingles in two Grant County locations suggesting that slugs are present in those fields.

Map of Wisconsin counties showing alfalfa weevil counts with darker red areas in Dane and Fond du Lac counties indicating higher infestation levels, and lighter pink areas in Grant, Iowa, Winnebago, Sheboygan, Shawano, and Oconto counties showing lower counts. — **Figure 1.** Average slugs captured from April 20–26. The number on the left is the average slug count per trap; the number on the right is the total number of traps established in that county.

County	Average slug count per trap	Total traps in county
Dane	0.17	36
Fond du Lac	0.18	23
Grant	0	7
Iowa	0	3
Oconto	0	6
Shawano	0	6
Sheboygan	0	3
Winnebago	0	13

Table of slug trap counts for the week of April 20–26