Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112Pest Watch Pea Leaf Weevil Challenging-to-control pea leaf weevils expanded their range in Alberta again in 2016. 30 www.seed.ab.ca | Advancing Seed in Alberta FOR the third year in a row, pea leaf weevils continued their damaging march into central and north-central Alberta in 2016. Their range expansion leaves pea and faba bean growers frustrated and scientists scratching their heads. “To be honest, we’re not exactly sure why their range is expanding,” says Scott Meers, insect management specialist with Alberta Agriculture and Forestry (AAF). “They stayed relatively contained in southern Alberta from the early 2000s until about three years ago when they started moving north. “It could be because of faba bean acre- age expansion; it could be the series of milder winters we’ve had lately; it could be because of the August moisture we’ve had in some of those expansion areas over the past few years. It’s probably a perfect storm of multiple factors and the insects are taking advantage of the opportunity.” In keeping with the past couple of years, movement continued largely in a north- westerly direction with weevils showing up in the Barrhead, Westlock and Lac St. Anne areas in 2016. Once again, the economic infestations occurred south of Hwy 1 and in central Alberta from Red Deer north almost to Edmonton. The weevils’ range appears to be expanding more quickly in faba bean acreage than pea fields. Unlike most yield-robbing insects, it is very difficult to quantify losses due to pea leaf weevil damage. Adult pea leaf wee- vils eat faba bean and pea leaves in spring but typically this feeding does not result in decreased yield. Rather, yield losses occur due to the weevils’ voracious larvae. These larvae eat a young crop’s nitrogen fixing nodules, causing indirect yield loss when the crop is starved of nitrogen. “Pea leaf weevils cause subtle yield losses – the less nitrogen fixation that occurs, the lower the yield potential. But that can be masked by soils that have high organic matter,” says Meers. “With an insect like bertha army worm, you know exactly what the loss will be. But it’s not possible with pea leaf weevil to say that if you have X number of weevil, you give up Y per cent of yield.” While pea leaf weevils are not the number one ranked robber of yield in pea and faba bean fields, they do cause significant stress to producers because they are difficult to manage. Pea leaf weevil do not generally respond well to foliar-applied insecticide: by the time a foliar application is pos- sible, pea leaf weevil eggs have already been laid in the soil and are enroute to hatching into hungry, nodule-consuming larvae. Producers who opt to apply foliar insecticide should only apply at early growth stages (two to three node growth stage), and only if damage appears on the clam leaves. If damage is evident on lower leaves of the crop, it is likely the adults have already laid eggs in the soil and insecticide will be useless. Research from southern Alberta sug- gests that seed treatment can limit yield loss from weevils; however, response to seed treatment is variable. When seeds germinate and seedlings emerge quickly and strongly, response to seed treatment can prove effective. However, cool, wet weather, early seeding and poor seeding depth can delay germination and emer- gence, and can result in less effective weevil control. That said, several days of very warm temperatures (20 C or more) in late April or early May can help weevils get an early start. A crop is much better able to withstand weevil infestation if it manages to grow beyond the sixth node stage before the weevils arrive, or if the seed treatment remains effective through the sixth node stage. Producers should also be aware that seed treatment may not offer as strong a return on investment in soils with higher organic matter content as it might in soils containing low organic matter. Given that central Albertan soils typically contain two to three times as much organic matter as southern Alberta’s soils, more research will need to be conducted to determine whether seed treatment offers a good return in those areas. “It’s a bit dangerous to project southern Alberta’s research on central Alberta. I Watch for characteristic, crescent shaped feeding marks along the edges of newly emerged pea leaves. Photo by Janet Kanters.