SEPTEMBER 2018 GERMINATION.CA 11 Disease and Insect Pressure It’s not known exactly why most intercrops see a reduction in dis- ease and insect pressure, according to Scott Chalmers, diversification specialist for Manitoba Agriculture’s Westman Agricultural Diversification Organization (WADO). But the data is there to prove this is often the case. Chalmers has been studying intercrop mixtures since 2009, mostly focusing on yield and nitrogen and phosphorous interactions in pea/ canola (or peanola) intercrops. Intercropping with canola has major benefits for peas: because peas, which typically fall to the ground, are held up by the canola, they experi- ence less disease pressure and pea quality is higher. They are also much easier to harvest. “You’re not having to drag your combine knife through the ground,” says Chalmers. “It’s easier on the equipment.” A peanola intercrop also offsets N depletion in the soil after canola. Planted alone, peas can leave a 40-pound N credit in the soil; pro- ducers can expect to see about half this credit — maybe 20 lbs. N — after peanola. But the reduction in pest and disease pressure is perhaps the most fascinating result of intercropping peas and canola. In a 2017 study, Chalmers showed that pea crops planted alone could see 16 or more pea aphids per plant. In the peanola mixture, that figure dropped to around two-to-four aphids per plant — well below the economic threshold levels for spraying. Similarly, in a study in Hamiota, Man., Chalmers’ team found 18 per cent pea disease incidence in mono- cropped pea versus two-to-three per cent pea disease incidence on the intercropped peanola under the same environmental conditions. Chalmers says intercropping is best used as a pulse production system: the intercropping system actually doesn’t favour canola, but there are huge benefits for pea. “What we tell farmers is that if you’re good at growing canola, just grow canola,” he says. “Intercropping is a more economical way of growing peas per acre. You may grow fewer peas, but because the canola is there, your net income is greater than if you grow either crop separately — you’re overyielding.” Starting from Scratch For producers considering intercrop- ping for the first time, Chalmers says it’s important to “start small,” and get comfortable with the process before growing whole quarters. “Intercrops are a bit more finicky. There’s more to look after. It’s two crops on one field, which means twice the thinking power,” he says. They’re riskier, too: according to Colin Rosengren, a founding member of Three Farmers, a Saskatchewan- based business that manufactures camelina oil, it’s hard to get crop insurance on intercrop mixtures. In Saskatchewan, producers can get specialty crop insurance on a portion of their intercrops, which guarantees producers the average on their other insured crops. But Rosengren, who intercrops perhaps three-quarters of his 6,000-acre operation, says it isn’t worth it for him. In fact, he believes most produc- ers who intercrop do not carry crop insurance at all. It’s a catch-22 for the industry, as insurers generally won’t offer insurance until a minimum number of acres are intercropped in a province. “Acres are very significant, but many aren’t insuring, so the numbers officially aren’t there,” says Rosengren. In terms of harvesting and selling intercropped mixtures, Chalmers says producers might need to modify equipment or buy rotary harrows or a cleaner and will need at least two working augers. “Harvesting takes quite a bit of coordination,” he says. Another risk is if buyers are not OK with a small amount of con- tamination if seed from another crop is found in a producer’s sample, Chalmers points out. “There’s no way Students counting aphids in peas in a pea-canola crop. Courtesy Scott Chalmers