COLUMBUS – Field observations last fall and farmers’ reports this spring indicate that slugs could be a big problem in Ohio’s no-till crops this season.
“I’d be happy if I turn out to be wrong, but at this point, I’ve been concerned about what I’ve seen out there more than I’ve ever been in the past,” said Ron Hammond, Ohio State University entomologist.
Fall numbers high.
Large slug populations in the fall tend to be a good predictor of the numbers that show up in spring, Hammond said. Last fall, he found slugs in fields even when he wasn’t looking for them.
A home-rigged beer trap caught 70 slugs – about seven times the normal levels – in a northwestern Ohio field.
Reports have come from northern, central and west-central Ohio, Hammond said.
An apparently mild 2000 summer helped slugs, and wintry weather is usually not a major factor in controlling them, Hammond said. Last winter brought enough snow to insulate the pests, he said.
Hungry when hatched.
Slugs lay eggs in spring. The hatched juveniles feed on plants, causing stand losses if seeds are still in the ground or emerging.
Farmers with persistent stand defoliation problems need to scout as soon it warms up and fields are dry enough for walking.
“Get out, and move the residue off the soil,” Hammond said. “Look under corn cobs and rocks. You don’t have to dig the soil up, but just loosen it up to see if they’re in the upper surface. It takes time to get out and look around.”
Set beer trap.
Farmers also can set beer traps to help determine slug numbers, Hammond said. Place a bowl or plastic container in the ground so the lip is even with the surface. Fill it partially with any beer except light beer. Cover the trap with a board or flat object.
The next day examine the trap for slugs.
Another method is to lay a board or shingle on the ground and check underneath it the next day or so.
Farmers should be prepared if slug numbers seem high relative to past years in fields with persistent defoliation.
Damage will depend on when eggs hatch relative to the growth of the crop. Juveniles can feed on nonemerged seeds or seedlings if they hatch at or before plant emergence.
On the other hand, plants can outgrow slug damage if the crop starts growing well before a slug hatch about mid- to late-May.
“You can have a lot of slugs out there, but because of the advanced growth stage of the plants, you will have little crop damage,” Hammond said. “The earlier you can plant, the better it is. The sooner the plants grow and get out of the ground, the better off they will be.”
Scouting is important because stand loss is certain if feeding is found on soybeans before emergence or shortly after.
Farmers with stand problems and a high slug population or eggs should consider applying molluscicide in the seed drill or right after planting.
Corn provides a better, but smaller, window for treatment if slugs are found before or at seedling emergence, Hammond said.
Deadline MPs molluscicide in bait form has been found to be effective. Farmers can apply it from the planter’s fertilizer box by dropping the tubes directly over the soil.
For post-plant applications, farmers can use a spinner spreader to apply product evenly.
As soon as temperatures get warm and soils are drier, Hammond will survey for slugs to diagnose the potential for crop losses. He will post reports to the OSU’s weekly Crop Observation and Report Network Newsletter at www.ag.ohio-state.edu/~corn/agcrops.html.
OSU Extension’s “Slugs on Ohio Field Crops” also provides information. It is available at local Extension offices or online at www.ag.ohio-state.edu/~ohioline/icm-fact/fc-20.html.