Top Crop Manager West April 2013 : Page 41

Life cycle of click beetles Wireworm insecticide availability Insecticide Thimet Temik Mocap Dyfonate Furadan Chlorpyrifos Counter Lindane Neonicotinoids Canada Phase-out 2015 No Never registered No No B.C. only No No Yes US Yes Yes Yes No Yes Yes No Yes source: aafc verNoN. No Currently registered insecticides set only on stun Since 2004, growers in Canada have lost some of their most effective treatments for the control of wireworms. Lindane, previous-ly mentioned as a cereal and corn seed treat-ment, was removed in 2004. other effective insecticides, used primarily in potato, includ-ing Temik, Dyfonate, Furadan and Counter (corn), are no longer available. Chlorpy-rifos is now registered for use in potatoes in Canada, but is only used in British Columbia due to there being no minimum residue level (MrL) on potatoes going to the United States. Thimet 15g, originally scheduled for phase-out for use on potatoes in 2012, is now being phased out in 2015. 40 Top Crop Manager west | april 2013 With lindane, research by Vernon showed that 65 to 70 percent of the resident larvae died during the growing season in wheat plantings. Lindane also killed more than 85 percent of new neonate larvae occurring later in the wheat-growing season, effectively knocking back wireworm populations for three years. research to replace lindane has been on-going since 1996, and Vernon has looked at three groups of insecticides for wireworm control: group 4a neonicotinoids include three actives that are registered for use in Western Canada as seed treatments for wire-worm control – clothianidin (poncho), thia-methoxam (Cruiser) and imidacloprid (raxil WW). “Killing neonates is very important when trying to control populations,” explains Ver-non. Unfortunately with the neonicotinoids, Vernon found, they do not actually kill many of the resident larvae. rather, the larvae be-come moribund, which is like being intoxi-cated, and often appear to be asleep. This al-lows the crop to establish and grow, but most wireworms recover fully by mid-summer. To make matters worse, in early-to mid-sum-mer when the new neonate wireworms are hatched, they survive the treatment as well. “You get great crop establishment and yield, but little reduction in resident wireworms and no reduction of neonates. This was the same for all neonicotinoids tested,” says Vernon. “The wireworms are there next year, and this could be one of the reasons we are seeing an increase in wireworm populations.” The effectiveness of a neonicotinoid seed treatment can also be reduced if ger-mination is delayed, since the level of in-secticide activity drops over time. other candidate insecticides include tefluthrin, bifenthrin and lambda cyalo-thrin in the group 3a synthetic pyrethroid family, and fipronil in the phenyl pyrazole family. Vernon’s research found that synthetic pyrethroids applied as wheat seed treat-ments were all repulsive but not lethal to resident or neonate wireworms. once again, while wireworms are repelled from the wheat seed, the crop can grow unharmed, and stand and yield are main-tained. Some of these pyrethroids, howev-er, have proven to be quite effective in re-ducing daughter tuber damage in potatoes. Fipronil shows great promise. In several research studies, fipronil rapidly killed res-ident and neonate wireworms with almost complete control during the spring and summer feeding periods. Similar to lin-dane, fipronil has the potential to provide multi-year protection from wireworms. Fipronil is registered in the United States as regent for the control of wireworm in corn and sunflower, and as an in-furrow at-planting spray application in potato. Vernon has found that fipronil can kill wireworms at very low rates relative to lin-dane or the neonicotinoids registered as cereal seed treatments. However, although wireworms will eventually die at these low rates, some feeding and crop loss can still occur. To get over this challenge, Vernon assessed a blend of thiamethoxam and fipronil at a lower rate, and found that this

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