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To Plan To Control Slugs Next Year

On July 01, 2017

Slug damage was a common problem for many crop producers this year. Extension Entomologist John Tooker suggests while slugs are fresh in our minds it may be beneficial to discuss some longer-term slug-management options that might help decrease future slug challenges.

Our factsheet that addresses slugs in no-till production provides some good context for this discussion and details on biology and management options; it can be found here http://ento.psu.edu/extension/factsheets/slugs-as-pests-of-field-crops).

Tooker suggests it is wise to acknowledge that most climate forecasts appear to be predicting that Pennsylvania will be getting wetter, not drier, over the coming decades. This means to him that springs like 2017 may become more common, making crop establishment and troubles from slugs even more likely and challenging.

One reliable approach to decreasing pest populations in the future is to diversify rotations as much as possible. This point has been reinforced for slug control by our work in Penn State’s Sustainable Dairy Cropping Systems project, which is lead by Heather Karsten in the Dept. of Plant Science. In this project, a large group of scientists is studying two diverse, six-year rotations that include cover crops and perennial hay (alfalfa or alfalfa/grass mix) and we are comparing these rotations to a two-year, corn-soybean rotation without cover crops. We have found that slug populations are significantly lower in the more diverse rotations than the two-year rotation. There are likely multiple causes for the larger populations in the two-year rotation and I will address two.

First, the rotation itself likely helps because it disrupts lifecycles and generally makes pest populations (insect, slugs, pathogens, even weeds) less successful because each crop has its own timing and management practices that contribute to keeping the population in check. In continuous corn or a corn-soybean rotation, management is often more or less similar each year, allowing pests the opportunity to adapt and thrive despite management.

The bottom line is that for pest management, a three-year rotation is better than a two-year, four-year is better than three-year (and so on); pest control capacity increases with duration of the rotation. Second, aside from disrupting pest populations, diverse rotations also foster improved populations of beneficial arthropods that can assist with pest control. Simple two-year rotations (including ours) often include preventative insect management with insecticidal seed coatings and broadcast sprays of insecticides, either by themselves or tank mixed with herbicides and/or fungicides. These insecticides and the simple rotation, by not providing sufficient habitat, together limit populations of beneficial insects, spiders, and centipedes that can help with insect pest and slug control.

Conversely, diverse rotations benefit these beneficial arthropod populations by providing more varied habitats, particularly when they include cover crops and/or perennially hay crops. The more you can grow these populations by diversifying and using insecticides only when necessary (even seed treatments), the more help you will get help against your slugs populations. To be clear, I am not advocating for no insecticides, I would like folks to use them within the framework of Integrated Pest Management, which with its economic thresholds, can inform when insecticides will be useful. Believe it or not, using insecticides blindly can exacerbate pest problems, including slugs.

Many farmers believe that cover crops tend to be part of the problem when it comes to slugs, but our research indicates that cover crops can be helpful in the fight against slugs. As mentioned above, cover crops can help diversify rotations and will promote better populations of beneficial arthropods, which in turn can help control slugs if their populations are strong and not disrupted by insecticides. Some farmers have even gone as far as planting into standing green cover crops (i.e., “planting green”) to help with their slug challenges. This approach involves establishing corn or soybean into standing cereal rye or other cover crop, and then spraying the cover crop with an herbicide (often glyphosate) one to seven days after planting, so the cover crops dies slowly. This planting strategy is not for the faint of heart and often requires some mentorship by an accomplished practitioner, but anecdotally during the spring 2017 those farmers that planted green well appear to have had less of a challenge from slugs. Our research is continuing to look into how this works, but preliminarily it seems that planting green gives slugs an alternative food source (slugs prefer the dying cover crop, often cereal rye, over the growing cash crop) while fostering improved, natural-enemy populations, particularly ground beetles (http://ento.psu.edu/extension/factsheets/ground-beetles) can help suppress slug populations. These beetles are vital because they eat slugs, but importantly their populations can be suppressed by insecticide use, including seeds treated with neonicotinoid insecticides, so if you are interested in planting green, untreated seeds and IPM are the best companions for this approach. Tooker would not advise growers to dive into planting green without discussing the practice with some farmers that have worked with the system for a while. But Tooker is becoming more convinced that it is a viable approach to slug management, in addition to the other benefits it provides (e.g., erosion control, organic matter input, nutrient cycling, etc.).

So there are a few ideas and principles to help you begin to develop a cropping system that stands up better against slugs. These approaches to farming are more management intensive, but in the long run appear to be more resilient in the face of pests and most any other challenges that may come along. Tooker welcomes your feedback.

To Plan To Attend The PA No Till Alliance Field Day

This years field day will kick off on the evening of July 26 and will run through the day of July 27. The event will be held at the Jeff Frey Farm, 13 Radcliffe Road, Willow Street, PA  17584. The evening of July 26 from 6:00 – 9:00 PM will feature a moderated open mike discussion on Manure Management in No Till and Cover Crops. Many of the speakers will be present to discuss one on one with participants as well as an opportunity to mingle with like-minded farmers!  Also, check out the soil pit! The evening is free with Pre-registration by July 21, 2017. Cost is $10 the day of the event and includes Ribs and Beef Brisket meal @ 6:30 p.m.

The program on July 27 runs from 9:00 a.m. -3:00 P.M and Registration opens at 8:00 a.m. Again the day program is free with Pre-registration by July 21, 2017. Cost is $10 the day of the event and includes a pulled pork or boneless chicken lunch. To pre-register, contact Jay Howes:  jhowes@pennag.com<mailto:jhowes@pennag.com> or call PennAg Industries (717) 651-5920<tel:(717)%20651-5920>. Free cover crop seed to be given away to 15 qualified participants!

Through the day there will be 4 engaging Panel discussions moderated by Steve Groff. In the morning panel number one will discuss “Practical Experience and Lessons Learned when Planting Green”. The second panel will discuss “How to grow your own cover crop seed”.

At 10:45 A.M. the Keynote speaker will be  Steve Berger who has  30 years No Till and 15 years cover crop experience on his 2,200 acre Iowa farm.  His topic will be “We always want something covering the soil”.

The afternoon panels will cover “Why Water Quality Matters” and “Summer/alternative forage options”. There will be an afternoon concurrent session on “Manure Management in No Till and Cover Crops” This will be a Roundtable Discussion with Steve Berger.

Quote Of The Week: “One person can make a difference and everyone should try.” John F. Kennedy