Author: David Hunsburger
Slugs remain a pest of high concern across the territory. Weather events such as mild wet winters allow the overwintering of all 3 stages of their life cycle, egg- juvenile-adult. This can precipitate a large population of feeding slugs early in the crop season. Slugs being hermaphrodites can reproduce without an active partner although they do use mating to exchange sperm. A single gray garden slug can lay hundreds of eggs, the good news is they do die soon after laying eggs.
Slugs like the cool moist conditions in spring and the eggs hatch, most slug damage that is troublesome for crop production occurs in the youngest plants. Cultural practices that enable a seedling to grow quickly are helpful in mitigating slug effects on the crop. Sometimes a shallow (3 inches of less) disking or turbotilling can lower populations by reducing cover, although there are plenty of anecdotal reports of horrendous slug damage in moldboard plowed “clean tillage” fields. The practice of planting green and providing an alternative food source of slow dieback cover crops has also been touted as beneficial. Use of a well-set row cleaner to provide for warmer soil temperatures is also helpful. Varieties with good early vigor and rapid growth along with adequate fertility can help the plants out grow the feeding form the slugs. Warm and sunny weather will also keep them to only feeding at night. The seed trench should be closed completely, this will not harbor the slugs in a dark moist environment and keep them from using the open trench as a conduit to the next seedling in the row. Some producers have used bait dropped from spinners or drones in high population outbreaks, this is quite costly. Some producers will cut 30% Nitrogen with half water and spray at night to act as a desiccant, this can also burn the crop. Extension does not currently have any published data on economic thresholds for damage but they do encourage scouting, using an asphalt shingle or wet cardboard sheet laid down over night will allow you to do a count, this can give you an indication of how quickly the numbers are rising… Again, good robust growth and sunny weather is the best.
Crop rotation and having a biodiverse cover crop can help provide a good habitat for slug predators to thrive. Ground beetles, rove beetles, centipedes, daddy long legs, firefly larvae, birds and frogs are the major predators of slugs.
This author will relate some experiences we have seen on our operation. We have increased the population of predators by changing some of our management practices. Some background here on beetles specifically, as invertebrates’ beetles and fireflies are affected by insecticides. Slugs as part of the mollusk family or snails without shells are completely unaffected by insecticides. Neonicotinoids are water soluble materials often applied to seeds and being soluble they are taken up by the plant tissues, lots remain in the soil solution and can leach out into aquifers. Slugs feed on the plants with no ill effects in any capacity, although the neonics are now in the bodily fluids of the mollusk. The beetle predator bites the slug and receives a lethal dose in just a little nibble, flops on his back and his legs go “running” just like a cartoon character and the beetle quickly expires. Noenicitinoids have a half life of 34 days in full sunlight exposed to soil biome. Without sunlight and microbes, it can take over 1300 days to dissipate, all the while being harmful to beneficials including bees and other pollinators.
Slug Management Case Study/Story
We signed up for the Conservation Stewardship Program (CSP) for the first time in 2008. This is a federal program administered by the USDA-NRCS, rewarding producers for good practices they’ve adopted on their own and offering incentives to adopt additional conservation activities. For us, the program was heavy on the rewards as we were long term no till, cover crops, manure management plans, crop rotation etc. As the program requires participants to adopt new practices, we have added many new conservation activities over the years. We have added some buffer strips, monitored and re-seeded our pastures, planted trees, tested forages, etc. Most recently, we agreed to reduce neonicotinoid seed treatments on our cash crops. This was an easy move as Kings has many options for alternatives for seed treatments.
Years after adopting this practice, we participated in a “soil your undies” activity with NRCS where you bury a pair of cotton underwear in a field and then dig them up after 60 days of being buried. Other than the elastic bands, the cotton of the underwear is merely a carbon and food for soil microbes. So, by burying the carbon source, you can observe the level of microbial activity in the soil. When it came time to dig up the underwear, I was away from the farm for work, so our local NRCS person dug them up for us. She commented on the veritable buzz that was going on in the corn field from all the activity of the insects…there was very much a sense that the soil was alive.
Since 2020, we have participated in a local soil health group that meets biannually. I am one of the few farms that does the reduced insecticides on seeds. A majority are no tillers and many of them have complained about the excessive replants they have had on corn and beans the last few years. We have not needed a replant for slug damage since we began this practice. I am convinced that is due to our robust predator population keeping them in check. I have observed some stripping feeding on the lower leaves, so I know I have a few slugs, but not any damage to stand count.
Final comments – it can be a challenge to find corn seed without neonic seed treatments. If you want to go to no insecticides on corn seed, you must use conventional hybrids. Kings does offer a few duracade above and below ground protection in a Fortenza non-neonic insecticide. Otherwise, EPA as part of the registration of the GMO traits has required by law a insecticidal seed treatment. Browse products or contact King’s Agriseed directly.
This is our story, if you want more resources to corroborate our suppositions, you may wish to contact Dr. John Tooker Entomologist from PSU for references regarding this topic. I hope some of you will consider looking at these types of management changes to increase your farm’s ability to reduce slug damage!
Recent Comments