Habitats for Beneficials

by Dr. David Orr (NCSU) and Tony Kleese (EarthWise) 

Organic farmers have historically been interested in using beneficial insects for pest management. Survey data indicate that the preferred method farmers use to accomplish this is not to purchase beneficial insects but rather to enhance populations that already exist on their farms. While pesticide impacts on beneficials are greatly reduced in organic farming operations, most organic farmers are compelled to provide habitat of some kind to further enhance beneficial populations. With just a few general principles, growers can create habitats for beneficial insects on their farms.

 

What Plant Species Are Best?

Focusing on specific plants may not be the best approach to establishing habitat. Everyone has their own preferences and goals (e.g. insect predators, pollinators, wildlife) with habitat creation. Instead of being overly concerned about which plant species to include in habitat, a better approach may be to focus on guiding principles. First, diversity is important—no one plant will satisfy all of your needs. Second, it’s valuable to choose diverse plants that bloom at different times so that something is always blooming on the farm. Third, promoting native plants and vegetation ensures that you have well-adapted plants that will provide resources to native beneficials and wildlife. Fourth, try to avoid plants that will feed pests like moths (e.g. Japanese honeysuckle that preferentially feeds hornworm moths).

 

Habitat Isn’t Just For Beneficial Insects
As with plant species, it may not always be best to focus on habitat for just one organism. Farmland wildlife will make use of habitat areas and considering their needs such as cover (e.g. field borders should be at least 30 ft. wide), nesting areas (e.g. shrubs) and food resources (e.g. seeds from flowering plants) will make your habitat more productive.

 

Ugly is OK

Neatly mowed areas offer few re- sources to beneficial insects or wildlife, while areas that look unkempt to us may be great habitat for wildlife provided they are not filled with exotic, invasive plants. Wildlife resource managers in North Carolina recommend that you “Farm Ugly” to enhance wildlife populations. For example, fallow field borders are basically weedy strips that are lightly disked roughly every 3 years to keep out woody vegetation. These are excellent and “instant” habitat for farmland gamebirds and songbirds. When you understand that neatness doesn’t equate to habitat and appreciate the value of lightly managed vegetation, then areas that are biologically productive will begin to look attractive.

 

What Should The Habitat Provide?

To be most effective, habitats should provide food (e.g. nectar, pollen) and alternative hosts (e.g. plant feeding insects that are not pests) for when there are none in crops. Also, habitats should include nesting sites (e.g. lightly vegetated areas for ground nesting bees and wasps, shrubs for songbirds) and overwintering sites (e.g. standing vegetation, trees, leaf litter on woodland edges). Clearly, all of these values may not come from a single habitat area, and so you should look across your entire farm when you are considering habitat.

 

How Much Habitat Is Enough?

In general, bigger is better when it comes to individual habitat areas for both beneficials and wildlife. Although narrow or small habitat areas may be fine for beneficial insects, wildlife prefer larger blocks. Narrow strips result in much higher predation of nesting birds for example. Research indicates that providing non-crop natural or semi-natural vegetation on at least 20% of a landscape will enhance populations of a variety of beneficials, including predators, parasites, and pollinators.

 

Where to Put the Habitat?

It is natural to want to put habitat next to the field you want to manage pests or pollinators in. This should not necessarily be the case, though. Research has shown that the larger landscape may be more important than what’s beside a field. In some cases, habitat that is a mile or more away may have an impact on insect populations in crop fields. For wildlife, as well as ground dwelling beneficials, it can be important to provide travel corridors for them to move across the landscape. Siting habitat areas adjacent to existing non-crop vegetation will help accomplish this.

 

Conclusion

By following the principles laid out so far, your beneficial insect populations will likely be enhanced. Whether it’s because of habitat or not, organic farming itself seems to be a practice that leads to better pest management by promoting something called species evenness. This means that in organic crops, populations of different species of insect predators are more or less equal in size and collectively are more effective in reducing pest numbers and damage than if the population size of one species was large and the others small.

 

Dr. David Orr is an Associate Professor of Entomology at NCSU with a research and extension focus on applied biological control of insect pests and organic insect management.

 

Tony Kleese has managed several organic farms, helped develop USDA’s National Organic Standards, and cofounded the Earthwise Company to offer consultations on organic farming and certification.

 

This article appeared in the Summer 2012 edition of the Stewardship Newsletter.  To receive this quarterly publication that is chock-full of great tips and tools for farmers, gardeners and foodies, join CFSA today!  Join us!