With Harvest 2020 in the rearview mirror for many farmers, it’s on to spring of 2021. If you’re like most no-tillers, you’re probably going to try something new, something that will improve yields, cut inputs or otherwise benefit the bottom line.
Another possibility is that you may be thinking about eliminating a practice that you’ve done for a long time and are just uneasy about giving it up. Data from Bobby Clark, senior extension agent at the Virginia Cooperative Extension, suggests that when it comes to spring insecticide applications, giving up may be just the thing to do. In a video he posted recently, he talks about research he conducted in 2018-2020 on the presence of slugs in agricultural fields.
Slugs are a common problem in no-till fields. The extra residue that is so helpful in reducing erosion, moderating the soil temperature and retaining moisture is also the perfect environment for slugs because it offers lots of cover and easy access to tender spring crops.
“In my opinion slugs are probably the biggest factor limiting no-till over a significant portion of Virginia, and likely a lot of other states,” he says.
The study looked at slug counts in 32 fields in the Shenandoah Valley. In 2020, the slug numbers were considerably higher than the previous two years due to a very mild 2019-2020 winter. But in addition to the weather, he says a major factor in slug counts was whether or not a pre-plant insecticide was used.
In 2018, for instance, the slug injury rating in fields where a pre-plant insecticide had been applied was about 0.47, whereas it was 0.27 in fields where no pre-plant insecticide was used. Correspondingly, predator counts averaged almost twice as many in the fields that didn’t have the insecticide applied (about 11.7) as those that did have it applied (about 5.9). This suggests that the pre-plant insecticides killed off many of the predators that feed on slugs and slug eggs, so a direct result of using those insecticides is a likely increase in slug activity.
Not every farmer has to contend with slugs, of course, but if you do, pre-plant insecticide applications may be something you just want to give up. Clark has lots more helpful information about managing slugs in a no-till environment and more on the Virginia Cooperative Extension website.
What’s your experience been with the effects of pre-plant insecticide on slug activity?