Margaret Holm
People who read this column know that I promote the benefits of supporting natural habitats. The notion of a clean and neat looking agricultural property with crops surrounded by bare soil and neatly mown turf grass is still a strong image. But we now know that there are many benefits to maintaining or developing strips or patches of plant diversity.
The impact of insect pests (many of which are non-native) and the invasive plants can be moderated by healthy native insect populations, which are living on natural habitats that surround many properties. But what if you don’t live near a natural ecosystem area? How can you encourage biodiversity on your property?
I attended two seminars this spring, one on native insect pollinators and the other on managing invasive plants. There were some common themes with suggestions on how property owners can encourage insect diversity to boost pollination and beneficial insects.
First, keep a few large trees and maintain some old untreated wood fences and sheds. Many of British Columbia’s 450 species of bees are solitary and nest in decomposing wood. Very few native bees are yellow and fuzzy; they may be small and jewel-toned or black and inconspicuous. They work longer hours than honey bees, start earlier in the year, and collect nectar and pollen when it’s too cold for the hive bees.
Studies show that where there are healthy native bee populations they pollinate more than 70 percent of flowers on an agricultural property compared to honeybees. But increased use of pesticides makes orchards more reliant on honeybees being brought in. Only one quarter of native bumbles population are healthy with many species declining due to lack of habitat and the combined effects of pesticides, herbicides and fungicides. Insects ingest pollen, nectar and other insects all which may be contaminated and lead to the build-up of harmful chemicals.
Moths, butterflies and flies also collect and disperse pollen. The hoverfly (syrphid fly), which mimics the colours of a bee, is an efficient flower pollinator and as a bonus--its larvae eat aphids and thrips. These attractive native flower flies have been shown to maintain good numbers on farm and urban settings. But they do need old trees for habitat. Maintaining mature trees on your property will also attract bats and birds of prey that provide valuable pest control.
A second important way to support biodiversity is to increase floral diversity by planting a variety of native and non-native cover crops and flowers mid-row or along crop borders. Properties that have the most plant diversity also have the most bees and insects. This relates to the third point, which is to manage invasive plants so that the need to use herbicides along crop margins is reduced. It is these edge rows that often support healthy insect populations.
Rather than constantly battling invasive plants, seed bare and disturbed soil areas with cover crops. Remember that sand, gravel and soil brought onto your property are major sources of weed contamination, as are vehicle tires. Each region has its own set of invasive plants. The Osoyoos and Oliver areas are battling puncturevine, a fast growing invasive with thorny seeds. It is not a problem further north, but it has shown up on agricultural properties in spot locations as weed seeds hitchhike on tires and vehicle undercarriages.
How soil is handled during construction can have a big impact on future trouble with invasive plants. When soil has to be disturbed, plant native or other cover crops right away to prevent invasive plants getting the upper hand. If invasive plants appear, keep the tops mowed so flowers do not get a chance to set seeds.
By creating favorable conditions for healthy native plants and insect populations, you can provide habitat patches that allow beneficial insects to survive, thrive, and disperse to neighbouring properties. ■
Margaret Holm works for the Okanagan Similkameen Conservation Alliance. Contact her at outreach@osca.org.