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Integrating Beetle Habitat into Pacific Northwest Farming Systems
Why care about Beetles?
While many beetles are notorious agricultural pests, many provide extremely beneficial biological control in agricultural systems. These Predacious ground beetles are long-lived, mostly opportunist predators that consume a variety of food types. Several factors make them particularly beneficial in farming systems. First, they are known to feed on a wide range of crop pests including insects such as aphids and cucumber beetle larvae as well as weed seeds. In addition, both the adults and juveniles can be voracious feeders, with some species consuming close to their body weight in food daily. Most adults forage on the soil surface at night, although a few climb plants in search of prey.
Farm practices that discourage ground beetles
Although many ground beetle species are broadly adapted to life on farms, some farming practices can reduce both their abundance and diversity. All species of ground beetles are highly susceptible to pesticides and most are at least somewhat susceptible to soil disturbance. Combined these two practices often make production fields inhospitable places for many ground beetle species. This is particularly the case in farming systems under intensive chemical crop production practices. Applications of pesticides and inorganic fertilizers are known to reduce ground beetle activity, abundance and diversity. Many species require less disturbed habitats such as perennial grassy margins in order to survive the winter. Farm practices that reduce or degrade these habitats (such as mowing grassy areas) can negatively affect ground beetles. In Oregon, ground beetle species that rely on habitat refuges provide the majority of the beetle activity within crop fields during spring and early summer.
Farm practices that encourage ground beetles
You can enhance the predacious ground beetle habitat on your farm by making a few relatively straightforward adjustments to your practices. The non-cropped area immediately adjacent to production fields can provide much of the less disturbed habitat that many ground beetle species require. These areas of the farm include grassy road margins and uncultivated vegetated strips that beetles use as refuges for the winter or to flee pesticide, crop or soil disturbances. Enhancing these uncultivated, or less cultivated areas on the farm can improve ground beetle numbers. Often this simply involves mowing less frequently or minimizing herbicide overspray.
These habitats can be managed more specifically as beetle habitat by planting grass and forb species that beetles like. These specific enhancements are called beetle banks. We have learned that there are many ways to construct a bank. There is no recipe for the perfect one. Each bank is uniquely designed and created by farmers with tools at hand, to fit their particular farming system. As part of the Farming Scaping for Beneficials Program, Beetle Banks have been established on local farms to explore on-farm methods of beetle bank establishment and their effects on ground beetle populations. Led by Gwendolyn Ellen, three farms have been included in the study thus far. Color posters describing how the banks were established can be downloaded below.
This project was supported by the Western Sustainable Agriculture Research and Education Program.