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Agronomic Crops Network

Ohio State University Extension


Slug Management Considerations and Statewide Slug Monitoring Report – Update #5

A slug on a leafTemperatures are on the rise in Ohio and while slugs remain in the fields, you may notice your plants outgrowing some of the foliage feeding they received over the past few weeks. Soybean plants are capable of withstanding certain levels of defoliation depending on their growth stage (Figure 1). For instance, plants from V1 (first trifoliate) – R2 (full bloom) have a 30% defoliation threshold before yield loss becomes an issue. In Ohio, many soybean fields are past VE (cotyledon emergence) – VC (unifoliate leaves unrolled), which is most susceptible to slug damage, because the growing point of the plant is within the emerging cotyledons. If your plants succumbed to slug damage at the VE – VC stage, it may be necessary to replant. If you decide to replant with no other treatments against slugs, keep a close eye on the seedlings because slugs remain in the field year-round and may continue feeding on the newly planted seeds.

For advice on soybean replant decisions, view our previous newsletter article:

Bait Treatment Options

If your field had a lot of slug damage this year and you’d like to treat slugs, baits containing metaldehyde or iron phosphate are approved for use in Ohio corn and soybean. Before applying baits, it is important to confirm slugs are causing the defoliation in your field. Slugs are nocturnal, making them difficult to spot during the day (especially with the increasing heat). To get a feel for your slug population look for the slugs by carefully examining the soil surface, and brushing aside residue and debris. You can put down square-foot sections of plywood at a few locations in the field (marked with flags) and check under them periodically in the morning. Unfortunately, we do not have a threshold recommendation for how many slugs are too many, but monitoring the population will give you a feel for whether the problem is increasing or decreasing. If you decide an application is necessary, apply the baits in dry weather, when rain is not in the forecast to avoid the pellets breaking down. 

Metaldehyde (3.24 and 4%) remains the most effective bait treatment to date. Concentrations are most effective when applying 10 pounds per acre for soybeans and 25 pounds per acre for corn (spread pellets at a rate of 5 – 12 pieces per square foot). Metaldehyde is labeled in Ohio for both crops, but not labeled for both crops in all states, so be sure to check the label before application. An alternative to metaldehyde is iron phosphate, but it is not as effective. The advantage of iron phosphate is it is approved for use in organic crops.

For more information on slug management, visit our field crop slug factsheet at

Figure 1. Soybean defoliation thresholds based on growth stage. To view the complete card, click here:










Ohio Monitoring Update

Many counties in Ohio continue to monitor for slugs for a multi-state project funded by the United Soybean Board which will allow us to better understand slug populations across the state and region. 

The map below shows the average number of slugs found under the shingle trap in each county from June 10th – June 16th (Figure 2). With the warm weather, the average number of slugs in the majority of counties decreased. Wayne County had the highest average of 2.8 slugs/shingle over the past week, followed by Knox County with 1 slug/shingle. The majority of counties in Ohio continue to report low numbers of slugs under the shingle traps; however, slug activity varies greatly from field to field, and all no-till fields planted recently should be scouted for slugs – especially fields that are newly planted or in the VE – VC growth stage.

Slug Monitoring in Ohio

June 10th – June 16th  

Figure 2. Average slugs captured from June 10th – June 16th. The bold number on the left indicates the average slug count for the week, followed by the standard number on the right which indicates the total traps set up in that county.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.