Loading...Phacelia has lavender blue flowers rich in nectar and pollen, which attract beneficial insects including hoverflies, which are effective aphid predators. A study where Phacelia tanacetifolia was planted in strips in wheat field margins in the UK and North America found the numbers of hoverflies was significantly higher in fields with strips. Aphid numbers were reduced in the second year of the experiment.
Anecdotal evidence from UK farms also suggests using Phacelia as a companion in oilseed rape can help protect the crop from Flea Beetle and pigeons. That said, its use as part of Integrated Pest Management (IPM) requires some forethought to ensure it delivers expected results, according to advisers.
Companion cropping
Marc Bull, technical sales adviser at Bright Seeds, says Phacelia is not an ideal companion crop in conventional cereals as any comprehensive herbicide strategy will take it out. Instead, he sees more potential in organic or regenerative farming systems. In these cases it can be autumn established in stubbles, with wheat or barley direct drilled into it in the spring. This way, it acts as a winter cover crop and attracts beneficial insects in the spring once it flowers, although an extreme winter frost could kill it off.
“Be cautious on seed rate as it can be a dominant crop,” Marc says, warning it can outcompete the cereal crop in the spring. Topping or grazing over winter can help, together with a cautious seed rate of about 1-1.5kg/ha. “As long as the following crop is a cereal, that herbicide regime will address volunteers,” he adds.
A lower seed rate is also advised when Phacelia is sown as a companion crop with oilseed rape, as herbicide or a mild frost will not kill it. And it can be used as part of a mix with plants like crimson clover and buckwheat.
Simon Hobbs from Agrii says companion cropping is attractive in light of Sustainable Farming Incentive (SFI) payments of £55/ha. Consequently, Agrii is undertaking trial work to look at weed control options in winter wheat sown with crops like Phacelia. These will assess factors like chemistry, in-field practicalities and gross margins. However, Simon believes field margins are a more effective way of attracting beneficial insects.
Flower margins attract beneficial insects
“Using a companion to attract beneficials into a crop isn’t the way to do it; beetle banks and crop margins are more permanent and can build insect populations.”
Margins should include a variety of flowering species like Phacelia, yarrow and meadow buttercup to attract a range of beneficials. The SFI pays £673/ha for flower rich margins, while in-field strips could also be used in larger fields to draw beneficials into the crop.
Welsh farmer cuts out insecticides with Phacelia
For Bridgend farmer, Richard Anthony, Phacelia is part of an overall strategy aimed at eliminating insecticide use and raising soil organic matter. He decided to grow it as a cover crop after oilseed rape and before wheat about eight years ago.
He tops the 194ha of oilseed rape stubble and drills Phacelia 5kg/ha with a disc and tine machine before rolling it in. The crop is grown for six to eight weeks before he sprays it off – and its fast establishment and large biomass have delivered multiple benefits. “It does so many things, it’s incredible,” he says. In particular he has noted a marked improvement in insects and worms, soil structure and mycorrhizal fungi activity.
We’ve managed to go for five years without using insecticides.
Richard Anthony
The short growing window does not allow time for the Phacalia to flower. However, Richard includes it in the flower margin mix around 61ha of oilseed rape. It’s here that it plays a part in attracting beneficial insects.
“We’ve managed to go for five years without using insecticides. We’re trying to increase the beneficials and get them to do the work for us,” says Richard, who farms 1,215ha. He’s also taken additional steps to avoid insecticide use, including grazing sheep on wheat in November-December. By nibbling off the top shoots and trampling in diseased side shoots the aim is to avoid the need to spray for aphids.