Our project seeks to expand the adoption of Conservation Biological Control practices for aphid
management on vegetable farms in northern Utah and the Intermountain West. Most farmers in
the region are faced with significant hurdles in learning and upfront costs required to implement
such practices. Aphid control is a fruitful “introduction” to Conservation Biological Control as
aphids have many natural enemies, and are a persistent problem for vegetable growers. Cabbage
aphid problems in particular have increased in recent years, as more farmers in the region grow
kale and other brassica crops year-round to meet customer demand.
Our project will establish aphid-control hedgerows at six farms, three of which will be used as
demonstration sites. Hedgerows will be evaluated for their potential to attract
natural enemies of cabbage aphid and to reduce aphid damage to cole crops, using associated
control plots (at varying distances from hedgerows) for comparison.
Education and outreach components of the project focus on building knowledge and visibility of
Conservation Biological Control practices at the grassroots level, and on making connections
between Master Gardeners, urban farmers, and established vegetable growers
to share their experience with Conservation Biological Control in our region. We will extend
Conservation Biological Control education and the results of this study to growers throughout
the Intermountain region with USU Extension or other publications, with an emphasis on the cost-benefit analysis of incorporating hedgerows for pest control.
Our project attempts to lower the barriers to adoption of Conservation Biological Control
practices by emphasizing 1) economic-yielding hedgerow plants that increase profitability (via
sales of culinary or medicinal herbs, seeds, or bouquets), 2) flexibility of hedgerow
implementation using a 4-component design for demonstration hedges, each component a standalone
border, and 3) the multiple resource conservation possibilities to meet other challenges on
the farm (e.g., reducing soil erosion, filtering runoff, preventing weed encroachment).
Objective 1. Evaluate whether hedgerows attract natural enemies of cabbage aphid
Objective 2. Evaluate whether fewer cole crops reach economic loss thresholds with
Objective 3. Use established hedgerows and outcomes of this study (Objectives 1 and 2) to
support broader education goals with Conservation Biological Control through
Master Gardener program and presentations to urban and small-acreage vegetable farmers.
Objective 4. Encourage grower-to-grower information exchange regarding Conservation
Biological Control with workshops or farm tours at demonstration farm sites.
Methods for establishing hedgerows (Objective 1a):
Site Analysis, planning, and design: SPRING 2018
- Site 1 (Green Team Farm). A 55 ft x 10 ft block was chosen for the hedgerow, along/directly adjacent to a 60-ft long greenhouse. The area had been used for storage and was compacted with low fertility soils, and few weeds. Topography was generally flat, but for the purposes of water catchment/conservation the area was sculpted to slope slightly downhill away from the greenhouse to capture runoff from the roof, and allow runoff to flow across the planting. A berm was constructed around three sides of the planting, and a pathway between the greenhouse edge and the planting for access. Plant choices: drought-tolerant mix of grasses, shrubs, and flowering perennials to provide continuous food and shelter for beneficial insects. Plants also selected to provide a yearly source of herbs and farmscaping perennials (most likely the grasses, most easily divided) to sell or add more beneficial insect habitat to the farm.
- Site 2 (Hand Sown Homegrown Farm) A 80 ft x 4 ft block was chosen for the hedgerow, located between a fence and an open irrigation ditch that conveys water to the farm. The area was covered with turf grass and perennial weeds, having been mowed with a weed whacker several times per season. The hedgerow site is adjacent to the growing area, which is enclosed by the fence. A visual screen and windbreak is needed at the site to mitigate pests and weed seeds arriving by wind from the shared access road area and irrigation ditch along the south property line. Plant choices: flowering columnar shrubs and native bunchgrasses to fit in the narrow space and grow tall (8 ft) to provide a windbreak and visual screen in 3-5 years; also several flowering perennials planted in the gaps at each end of the hedgerow to attract and retain beneficial insects.
- Site 3 (Wheeler Historic Farm) A 100 ft x 5 ft block was chosen for the hedgerow, which follows the edge of a historic farmhouse yard, and an irrigation ditch for part of its length (60 ft). The area had been bulldozed in 2017 for renovation of the historic farmhouse and garden, and was populated by some annual and perennial weeds. A hedgerow is needed as a living fence to enclose the historic farmhouse garden and provide stabilizing vegetation along the irrigation ditch. Plant choices: modern cultivars of traditional shrubs will be used, to aesthetically match the historic farmhouse, provide a realistic representation of a historic hedgerow, and provide recognizable species to the public for the “demonstration” objective.
Site Preparation and planting: FALL 2018
- Site 1 (Green Team Farm). To prepare the site, the site was irrigated for 24 hours, soil was then loosened with a broadfork, and approximately 2″ of bark fines were spaded into the planting area. Plants were installed followed by installation of six Netafim irrigation lines (layout shown in photos). Species include feather reed grass, blue gramma grass, rabbitbrush, Russian sage, catmint, alyssum, candytuft, echinacea, black eyed susan, goldenrod, licorice mint hyssop, butterfly weed, and purple aster.
- Site 2 (Hand Sown Homegrown Farm) To prepare the site, turf grass and weeds were removed by hand and approximately 1″ of bark fines were spaded into the planting area. Plants were installed followed by installation of two Netafim irrigation lines (layout shown in photos). Species include black tower elderberry, golden tower elderberry, standing ovation serviceberry, little bluestem grass, blue gramma grass, echinacea, candytuft, black eyed susan, goldenrod, and autumn joy stonecrop.
- Site 3 (Wheeler Historic Farm) To prepare the site, weeds were removed by hand and approximately 2″ of bark fines were spaded into the planting area. Plants were installed followed by installation of three Netafim irrigation lines (layout shown in photos). Species include knockout rose and Korean dwarf lilac for the shrub row and tufted hairgrass along the outside edge (the dark, uniform grass clumps shown in photos). Note: Existing perennial grasses (the lighter green, irregular clumps) immediately adjacent to the ditch were left in place to provide temporary stabilization while the tufted hairgrass becomes established.
Educational & Outreach Activities
- Tour of farmscaping elements at Green Team Farm, Salt Lake City, UT. Event = “Bee Fest, A Celebration of Pollination” June 16, 2018. Tour of Green Team Farm midway through the festival led by James Loomis (GT Farm Director), with approximately 5 participants who were farmers, included stops emphasized the multitude of existing beneficial insect plantings on the farm including the OW18-007 planned hedgerow site where Western SARE signage was posted.
- Workshop and tour of farmscaping elements at Wheeler Farm, Murray, UT. Event = “Urban Farming and Farmscaping Conference” August 30, 2018. Approximately 10 participants at the workshop were farmers. Approximately 5 farmer participants attended the farmscaping elements tour led by Laura Horn that emphasized the existing beneficial insect plantings including two planned installations funded by OW18-007 where Western SARE signage was posted.