SlugNet: 2025 Wisconsin Slug Monitoring Project

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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

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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 June 22 – 28

Slugs were captured in Chippewa, Fond du Lac and Ozaukee Counties. Each county reported less than one slug per trap (Figure 11). Minimal feeding damage has been reported across the state, and crops have progressed beyond the vulnerable stages (e.g., emergence and early vegetative) for economic damage.

This is the last SlugNet Update of 2025. If you notice severe slug damage in your fields, reach out to the SlugNet Team at UW-Madison Extension.

Wisconsin map with counties shaded red and labeled with values like “0.6, 10” or “NR, 6”.
Figure 11. Average slugs captured from June 22 to June 28. 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.
CountyAverage slug count per trapTotal traps in county
Calumet03
Chippewa0.610
ClarkNR3
DaneNR39
Fond du Lac0.4511
Grant07
Iowa03
Kewaunee06
Marathon05
MarinetteNR1
Oconto08
Ozaukee0.254
RockNR2
SaukNR3
ShawanoNR6
Sheboygan018
Winnebago013
Table of slug trap counts for the week of June 22–28. NR indicates no data were reported for that county during the monitoring time frame.

Week of June 15 – 19

Slugs were captured in Fond du Lac and Sheboygan Counties. Each county reported less than one slug per trap (Figure 10). Minimal feeding damage has been reported across the state. We will continue to provide slug monitoring updates through June.

Wisconsin map with counties shaded red or pink, labeled with values like “NR, 10” or “0, 6”.
Figure 10. Average slugs captured from June 15 to June 19. 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.
CountyAverage slug count per trapTotal traps in county
Calumet03
ChippewaNR10
ClarkNR3
Dane039
Fond du Lac0.4323
Grant0.25
Iowa03
Kewaunee06
Marathon05
MarinetteNR1
Oconto08
Ozaukee04
RockNR2
SaukNR3
Shawano06
Sheboygan018
Winnebago013
Table of slug trap counts for the week of June 15–19. NR indicates no data were reported for that county during the monitoring time frame.

Week of June 8 – 14

Slugs were captured in Dane, Chippewa, Grant, and Sheboygan Counties. Each county reported less than one slug per trap (Figure 9). Slug numbers have started to decline throughout the state and minimal feeding damage has been reported. We will continue to provide slug monitoring updates through June.

Wisconsin map with counties shaded red or pink, labeled with values like “0.8, 10” or “NR, 2”.
Figure 9. Average slugs captured from June 8 – 14. 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.
CountyAverage slug count per trapTotal traps in county
Calumet03
Chippewa0.810
Clark03
Dane0.0739
Fond du Lac017
Grant0.437
Iowa03
KewauneeNR6
Marathon05
MarinetteNR1
Oconto08
Ozaukee04
RockNR2
Sauk03
Shawano06
Sheboygan0.0618
Winnebago013
Table of slug trap counts for the week of June 8 – 14. NR indicates no data were reported for that county during the monitoring time frame.

Week of June 1 – 7

Slugs were captured in Dane, Chippewa, Clark, Fond du Lac, and Sheboygan Counties. Each county reported less than one slug per trap (Figure 8). Slug pressure remains low throughout the state with minimal feeding damage reported. If soybeans or corn have not emerged yet, continue to scout for slugs and slug feeding damage. We will continue to provide slug monitoring updates through June.

Wisconsin map with counties shaded red or pink, labeled with values like “0.5, 10” or “NR, 6”.
Figure 8. Average slugs captured from June 1 to June 7, 205. 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.
CountyAverage slug count per trapTotal traps in county
Calumet03
Chippewa0.510
Clark0.663
Dane0.0839
Fond du Lac0.1217
Grant07
Iowa03
KewauneeNR6
Marathon05
MarinetteNR1
OcontoNR8
Ozaukee04
RockNR2
SaukNR3
ShawanoNR6
Sheboygan0.1218
Winnebago013
Table of slug trap counts for the week of June 1 – 7. NR indicates no data were reported for that county during the monitoring time frame.

Week of May 25 – 31

Slugs were captured in Dane, Grant, and Oconto Counties. Each county reported less than one slug per trap (Figure 7). All slugs were adults. Two counties did not report. We have had reports of slug feeding damage on corn and soybean seedlings in Dane and Dodge County in the last week. 

Wisconsin map with counties color-coded and labeled with values like “0.25, 8” or “NR, 10”; Grant County is dark red.
Figure 7. Average slugs captured from May 25 to May 31. 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.
CountyAverage slug count per trapTotal traps in county
Calumet03
ChippewaNR10
Dane0.2639
Fond du Lac017
Grant0.67
Iowa03
Kewaunee06
Marathon05
Marinette01
Oconto0.258
Ozaukee04
RockNR2
Sauk03
Shawano06
Sheboygan018
Winnebago013
Table of slug trap counts for the week of May 25 – 31. NR indicates no data were reported for that county during the monitoring time frame.

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.
CountyAverage slug count per trapTotal traps in county
Calumet0.333
Chippewa0.110
Dane0.0636
Fond du Lac0.1217
Grant07
Iowa03
Kewaunee06
Marathon0.25
MarinetteNR1
OcontoNR8
Ozaukee0.54
RockNR2
ShawanoNR6
Sheboygan0.063
Winnebago013
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.
CountyAverage slug count per trapTotal traps in county
Dane036
Fond du Lac0.217
Grant0.37
Iowa03
Kewaunee06
Marathon05
MarinetteNR1
Oconto08
OzaukeeNR4
RockNR2
ShawanoNR6
Sheboygan0.333
WinnebagoNR13
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. 
CountyAverage slug count per trapTotal traps in county
Dane0.1636
Fond du Lac023
Grant0.67
Iowa03
Kewaunee06
Marathon05
MarinetteNR1
Oconto08
Ozaukee04
RockNR2
Shawano06
Sheboygan018
Winnebago0.0813
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.
CountyAverage slug count per trapTotal traps in county
Dane036
Fond du Lac0.0923
Grant07
Iowa03
Marinette01
Oconto0.758
Rock02
Shawano0.176
Sheboygan018
Winnebago0.0813
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.
CountyAverage slug count per trapTotal traps in county
Dane0.1736
Fond du Lac0.1823
Grant07
Iowa03
Oconto06
Shawano06
Sheboygan03
Winnebago013
Table of slug trap counts for the week of April 20–26
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