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COVER CROPPING FOR POLLINATORS AND BENEFICIAL INSECTS

Doug and Anna Crabtree’s farm rests on more than 2,000 resources to maximize their health and reproductive po-
acres in northern Montana, and it is a model of how cover tential, an abundance of nectar to produce surplus honey, a
crops can be a foundation of pollinator and beneficial insect refuge from insecticides, and enhanced nesting opportuni-
management. Like many farmers, their approach to cover ties for wild bee species.
cropping began with an interest in soil health and quickly Other Beneficial Insects
grew to encompass much broader goals as they recognized The natural enemies of crop pests that sometimes in-
the additional benefits cover crops could provide. “We want habit farms include a diverse range of predatory beetles,
to implement pollinator conservation at the field-level aphid-eating flower flies, lacewings, small solitary parasitic
scale,” Doug says. “Anyone can wasps, and many others. In addition to preying upon crop
create a small wildflower strip, pests, most of these predatory and parasitoid insects either
but as we scale up, we need need, or benefit from, alternative food sources during at
conservation areas distributed least one stage of their life. In some cases, that alternative
across the entire operation.” food source is nectar or pollen. Consequently, like pollina-
While the Crabtrees have es- tors, many of these natural pest enemies also benefit from
tablished permanent native flowering cover crops. An increase in beneficial insects
wildflower strips around many brought about by a mix of annual buckwheat, lacy phacelia,
Photo by Julie Birky eton of habitat throughout the and sweet alyssum resulted in fewer pests. In other cases,
of their fields to provide a skel-
cover crops can support beneficial insect populations even
farm, extensive cover crop ro-
when they do not flower. Some predators and parasitoids
tations provide the muscle that
makes their operation a rich landscape for bees and other do not feed on nectar and
pollen, but rather need a
beneficial insects. This commitment to cover cropping is continuous supply of prey
having clear and positive impacts on crops such as flax, insects to maintain their
sunflower, and safflower. A farm’s ability to support its own populations. So when cash
pollinator community provides biological security, and the crops are absent, non-flow-
Crabtrees have never needed to bring honey bee hives onto ering cover crops can sup-
the farm for pollination. Photo by Dirceau Gasson port pests to the extent that
Basic Pollinator Ecology they become a stable food
Honey bees and wild bees alike are considered important source for beneficial insects.
agricultural pollinators, and both groups of bees share many For example, ground beetles, which are generalist pred-
of the same habitat requirements necessary to thrive. Both ators of slugs, caterpillars, and grasshopper eggs, can be
require reliable and abundant pollen and nectar resources sustained by leaving some areas unmowed or by creating
throughout the growing season. In addition, bees require a “beetle bank” of perennial grasses outside crop fields.
protection from pesticides. While large doses may be di- Beetles can overwinter in this augmented habitat and their
rectly lethal to bees, smaller doses can result in sublethal prey can breed in it. Thus, these grassy refuges can keep
impacts, such as reduced reproduction or foraging. Inter- the beetle population high by providing both habitat and
estingly, research suggests that diverse pollen and nectar a food source outside the cropping period. Similarly, even
resources may help improve the overall health of bees and if prey insects found in cover crops are not pests of your
increase their chances of cash crops, they can still be an important food resource for
detoxifying low doses of predator and parasitoid insects that will switch their prey
some pesticides. Wild bees preference once cash crop pests become available. Finally,
also need undisturbed areas like pollinators, predatory beneficial insects need protec-
for nesting, and the undis- tion from insecticide applications and vegetative structures
turbed soils of a cover crop
for egg-laying or overwintering. Well-managed cover crop
Photo by Dirceau Gasson can provide this. Flowering systems can help meet these habitat requirements.
cover crops can support the
The plants that best fit your needs will vary by location and
habitat requirements of bees
purpose. Different cover crops have different strengths.
through pollen and nectar

40 Flowering broadleaf species are a must when selecting