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2020 Pennsylvania Slug Monitoring Project

Many fields across Pennsylvania are past their most vulnerable seedling stages. As corn and soybean plants continue to emerge in some fields, target your scouting to problem slug fields. Previous updates are included below this week's report.

Updated:

June 16, 2020

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Marsh slugs occur frequently at slug monitoring sites in Pennsylvania. Photo: Liz Bosak.

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Previous updates for the PA Slug Project, part of the Soybean On-Farm Network, are included below this week's report.

June 16, 2020

No news is good news for the PA Slug Monitoring Project this week. Corn and soybean crops at most monitoring sites are no longer in danger of severe slug damage. Slug counts for all four monitoring species remain below one per trap on average. Next week will be the last report for this spring. We will resume monitoring in the fall after harvest.

Reported counties for this week

Butler – Justin Brackenrich
Centre – Adriana Murillo-Williams
Crawford – Joel Hunter
Lebanon – Del Voight
Perry – Liz Bosak
Schuylkill – Dwane Miller
Union – Anna Busch
York – Heidi Reed – spring reporting completed

June 9, 2020

Another quiet week for the PA Slug Monitoring Project. A few field sites had reported minimal damage but now those crops have passed the most vulnerable stages. Only 1 site is reporting more than 2 slugs per trap but damage in the field is minimal. Fields to target for scouting would be fields with open seed furrows, wetter fields, and those with a history of excessive slug feeding. Bean leaf beetles are active in soybean fields right now and will damage the thick, fleshy seed leaves and the true leaves. One easy way to tell the difference between slug and bean leaf beetle feeding is to look for slugs' shiny, slime trails on leaves. It usually takes at least ten damaged plants before a slime trail is spotted.

Reported counties for this week

Bedford and Cambria – Zach Larson
Butler – Justin Brackenrich
Centre – Adriana Murillo-Williams
Centre – Chris Houser
Crawford – Joel Hunter
Lancaster – Jeff Graybill
Lebanon – Del Voight
Perry – Liz Bosak
Union – Anna Busch
York – Heidi Reed – spring reporting completed

June 2, 2020

It has been a quiet week for the PA Slug Monitoring Project. Despite challenging cold weather for most of May, many corn fields are approaching v2 (2 leaf collars) and v3 (3 leaf collars). Meanwhile, other cornfields are just being planted or corn seedlings emerged this week. The older corn plants at v2 and later are much more capable of out-growing slug damage except under extremely high slug populations. Newly emerged seedlings are the most vulnerable but with many areas of the state expecting temperatures above 80 degrees later this week, corn seedlings will likely out-compete light to moderate slug pressure.

Since a corn plant's growing point/apical meristem is below ground until v6, young corn plants can withstand moderate to heavy slug feeding for a few days. This is not the same situation for soybean. Soybean plants are particularly vulnerable under moderate to heavy slug feeding. The growing point of soybean is at the top of the plant meaning that once the plant experiences too much feeding damage, it is not able to recover, and the field needs to be replanted.

Monitoring sites from across Pennsylvania are reporting low slug numbers. There is only 1 site out of 20 sites this week reporting more than one slug found per trap. Each field site contains ten slug traps and the average is considered for each field site for this report. Given our monitoring results, I would suggest checking fields that may have been planted on the wet side and have partially open to completely open seed furrows. Fields with open seed furrows typically have the worst slug damage if a slug population exists in the field.

Reported counties for this week

Bedford and Cambria – Zach Larson
Butler – Justin Brackenrich
Centre – Adriana Murillo-Williams
Centre – Chris Houser
Crawford – Joel Hunter
Lancaster – Jeff Graybill
Lebanon – Del Voight
Montgomery – Andrew Frankenfield
Perry – Liz Bosak
Schuylkill – Dwane Miller
Union – Anna Busch
York – Heidi Reed

May 26, 2020

A cold, some would say frigid, May slowed or stalled planting across the state. This week, one county reported slug damage in four-day old corn seedlings. Many corn and soybean fields have been planted over the last seven days. Next week we should finally get a more accurate assessment of slug damage on corn and soybean crops. Slugs defoliate corn and soybean plants by scraping leaf tissue and eventually creating large, blocky holes. After recent feeding, shiny, iridescent slime trails can be observed. Slug feeding usually occurs at night but actively feeding slugs have been noted on cool, cloudy days or during foggy, morning hours. It is especially important to make sure seed furrows are closed because an open seed furrow allows slugs to feed on plants emerging from the seed and remain relatively protected and comfortable. This is the so-called 'slug superhighway' that producers want to avoid if possible. Slug populations remain low with most traps containing zero or a single slug.

Please note that the reporting counties were updated for May 12 and May 19.

Reported counties for this week

Lebanon – Del Voight
McKean and Potter – Nicole Santangelo
Montgomery – Andrew Frankenfield
Schuylkill – Dwane Miller
Union – Anna Busch

May 19, 2020 report

Marsh slugs are the most common slug species sited in slug traps. Juvenile and adult gray garden slugs remain an infrequent visitor to slug traps around the state. One site reported Dusky slugs this week. No crop damage to report yet because most crops at our field sites have not yet been planted or emerged.

Reported counties for this week

Bedford and Cambria – Zach Larson
Crawford – Joel Hunter
Lebanon – Del Voight
McKean and Potter – Nicole Santangelo
Montgomery – Andrew Frankenfield
Perry – Liz Bosak
Schuylkill – Dwane Miller

May 12, 2020 report

At least in our monitored fields, it looks like slugs did not appreciate the cold, wet weather of last week. The northern areas of Pennsylvania reported snow while the southern region had widespread freezes, frosts, and rain. Marsh and Dusky slug counts remained at low levels for the third week in a row. It will be at least a week before crop damage observations will begin in the southeast and southcentral regions.

Reported counties for this week

Butler – Justin Brackenrich
Crawford – Joel Hunter
Lebanon – Del Voight
McKean and Potter – Nicole Santangelo
Perry – Liz Bosak
Schuylkill – Dwane Miller
Union – Anna Busch

May 5, 2020 report

Slug populations remain at low levels again this week. Observed slug species included: Marsh, Gray Garden, Dusky, and Banded. Most fields had zero to one slug found per trap with ten traps distributed in a single field. One field exceeded two Marsh slugs per trap but, again, this is a low number of slugs. Cool, rainy weather has delayed corn and soybean planting throughout the state. When crops begin to emerge, we will monitor for plant damage at 3, 7, 14, and 21 days after emergence.

Reported counties for this week

Bedford and Cambria – Zach Larson
Franklin – Brittany Clark
Lancaster – Jeff Graybill
McKean and Potter – Nicole Santangelo
Montgomery – Andrew Frankenfield
Perry – Liz Bosak
Schuylkill – Dwane Miller
Union – Anna Busch
York – Heidi Reed

April 28, 2020 report

Based on prior years, Extension Educators and Farmer Cooperators identified fields with a history of slug problems. We are back in those fields again this season to scout for slug eggs and install slug traps. We are looking for four different species of slugs in each trap: Gray Garden, Marsh, Dusky, and Banded. After the crop emerges in each field, plant damage will be assessed in addition to slug counts.

Of the sixteen reported fields so far, very few if any slug eggs have been found. In each field, eggs were counted at ten random locations within a one square foot area and ten slug traps were installed. In all reporting counties, see below for list, adult Marsh slugs were found but the average count per trap is less than one. Most of the gray garden slugs observed in traps were adults with a few juveniles. Spider and ground beetle activity were noted at most of the field sites. It is a little too early to tell if slug counts are following a similar pattern as 2018 and 2019. Stay tuned for next week's report.