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Organic Agriculture Centre of Canada
Organic farms provide habitat for many beneficial organisms, including pollinators and insects that prey upon or parasitize pests. In this article, we focus on creating insectaries – strips of plants that support beneficial insects. The subject is currently being studied by Organic Science Cluster researchers.
You can leave weeds or strips of insectary plants along the edges of the fields. The smaller the field, the more effective this is. In some cases, the perimeter may include trees and bushes. You can also have strips of insectary plants throughout a field. Beneficials can travel along these ‘habitat highways’ and disperse into the fields. Larger and more connected strips provide more benefits than small isolated patches.
Living mulches can be insectary plants. To reduce competition, overseed the living mulch seed after the crop is established. Also, crops can be used. For example, unharvested mustard greens, broccoli side shoots and fava beans flower late into the fall and provide food for pollinators, parasitoids and hoverflies.
Consider the following when selecting insectary weeds, flowers or cover crops.
To prevent insectary plants from going to seed or to stimulation migration of predators, you can mow the insectary plants. For example, flowering dandelions provide an essential early source of pollen and nectar when not many other plants are in bloom. Once they are mowed, the beneficials will move into surrounding crops. Sickle-bar mowers are gentler on the beneficials than flail and rotary mowers.
By planting, mowing and tilling different strips at different times, you can maintain several life stages of the plants at one time. This allows you to have flowering plants throughout the season without ever letting them go to seed.
Avoid overfertilizing the insectary. High levels of nitrogen will lead to more vegetative growth and delay flowering, the most valuable stage. Also, if your insectary plant or blend contains legumes, a low level of nitrogen in the soil will stimulate nitrogen fixation.
Creating insectaries on your farm can be as simple as not mowing the field edges. Or, you can develop a complex system of living mulches and flowering crops planted and mowed in succession. The challenge is to reap the greatest benefits of the insectary plants without incurring significant costs (i.e., competition with crops, increase in pests).
© 2012, Organic Agriculture Centre of Canada (OACC)