Some years, slugs cause only minimal problems. Other years, they can be a real problem.

“It seems that these critters just go in cycles,” says Jeff Graybill, a Manheim, Pa., farmer and Penn State Extension educator in Lancaster County.

This year, the cycle has been bad. “I had to replant about 20% of my 15-acre bean field,” he says. “It was a real challenge because the damage varied widely across the field, and we probably replanted almost a dozen areas randomly scattered. So, a lot of driving down good beans to get to the bad ones.”

Penn State’s Slug Monitoring Project, funded by the Pennsylvania Soybean Board, has been tracking slug populations across the state since the start of the growing season. Its most recent report showed slug populations lower than previous weeks, but the damage to crops, particularly soybeans, has already been done.

Eric Rosenbaum, Rosetree Consulting, says this has been one of the worst years for slugs he has seen.

“It’s pretty bad. This year, it’s up there. It’s really bad,” he says.

Some areas, such as the Hegins area of Schuylkill County, Pa., have been especially hard hit, he says, with many growers having to replant. He attributes the high slug feeding to a couple of factors. First, a nice planting window in April allowed growers to plant early. Then, it got cold and rainy, which didn’t result in much growth but allowed slug populations to explode. The lack of crop growth created a smorgasbord for slugs to gorge on.

“The worst was in high-residue situations, in soybeans no-tilled into high-residue corn,” Rosenbaum says. “We did see damage in corn, but most of the replants were soybeans.”

IS IT YELLOW DWARF? Notice some yellowing in your barley, wheat or other small grains when you did your fertilizer or herbicide application? It might be barley yellow dwarf virus. But according to Eric Rosenbaum, between 60% and 70% of small-grain fields he tested this spring came back positive for two other lesser-known diseases: soilborne wheat mosaic or bacterial mosaic of wheat. (Photo by Juliette Marshall, Bugwood.org)

Past experiences with slugs have led some growers to adopt more tillage on fields that were once long-term no-till. Rosenbaum says this is reactionary and shouldn’t be done without planning and thinking of alternatives.

“The pendulum is swinging back to more tillage,” he says. “I wish it wasn’t so, but it seems to be that way.”

One thing he has noticed is that fields where growers no-tilled a thin cover crop in corn ground last fall — 40 pounds of rye, for example — and then planted green this spring saw very few problems.

What’s that yellow streaking?

Notice some yellowing in your barley, wheat or other small grains when you did your fertilizer or herbicide application? If you thought barley yellow dwarf virus, you may be right. But not necessarily.

In fact, Rosenbaum says, between 60% and 70% of small-grain fields he tested this spring came back positive for two other lesser-known diseases: soilborne wheat mosaic or bacterial mosaic of wheat.

It was particularly noticeable, he says, on dairy farms with continuous triticale and wheat silage rotations.

“For the past 30 years a lot of dairy farmers have been doing rye silage and corn silage,” Rosenbaum says. “Now it’s triticale and wheat. This is when a buildup of soilborne diseases happens.”

These diseases are often misdiagnosed as barley yellow dwarf virus because they look very similar. Symptoms, he says, start appearing when plants start to elongate in spring with just some yellow patches in fields, becoming more noticeable as the plants mature.

According to Penn State Extension, soilborne wheat mosaic and the related wheat spindle streak mosaic can cause severe stunting along with yellowing and tip dieback. These viruses are transmitted by a fungus-like soil organism that can survive for several years in affected fields, making management challenging. Some small-grain varieties with resistance are available.

The bacterium Clavibacter michiganense, subspecies Tessellarius, causes bacterial mosaic of wheat, which causes yellow flecking of leaves. The bacterium persists in crop residue but may also be seedborne. To avoid it, start by using certified seed.

Another way to avoid it: "Rotate your small-grain species around, and even how to manage cover crops and species selection,” Rosenbaum says. “So, if wheat is in rotation as a cash crop, don’t use it as a cover crop.”