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Story Posted: June 15, 2011 Canola Watch: Cutworms, Weeds, Sprayer cleanout Issues of the week: Weed control is top of mind for most growers. Many will finish their first in-crop herbicide pass this week, weather permitting. Insects are a close second to weeds. Flea beetles are active in all regions and spraying will be required in some cases, especially on fields with thin stands and/or slow crop growth from cool temperatures or frost damage. Cutworm spraying has also been reported in some regions. Growers who didn't manage to seed their intended canola acres should talk to their canola buyers now if they have contracts they can't fulfill. Growers tempted to leave volunteer canola as a crop, consider this: Do you really want to make this your canola crop and take that field out of canola rotation for the next year or two? Crop and weather update Alberta: Southern Alberta has enough moisture for the most part. Central Alberta needs rain, although some areas received a welcome inch this week. Warmer weather has perked up the crop. Alberta crop report. Saskatchewan: Canola is at the 3-leaf stage, on average, and advancing fairly well, although some stands are very thin. Western Saskatchewan could use a general rain. The southeast remains wet and with the crop insurance deadline this week, many acres will not be seeded. Saskatchewan crop report. Manitoba: Seeding ranges from 90-95% complete in areas of the northwest and east, to as low as 5-10% in parts of the southwest. With crop insurance deadlines this week and substantial rain the past few days, those numbers won't change much. Estimates are that most growers (except those in the southwest) got 75% of their intended canola acres seeded. Manitoba crop report. Manitoba crop report. Insect update The Prairie Pest Monitoring Network report says dingy, bristly and glassy cutworms plus sod webworms have been retrieved from timothy, creeping red fescue and select canola fields this spring in the south Peace River region. Click here for a link to the Prairie Pest Monitoring Network's newly posted Cutworm Larval Collecting Protocol. (After clicking, scroll to the bottom of the website page then click on "Cutworm" to open).
Flea beetles. With many early seeded canola crops taking a month or more to get established, protection from insecticide seed treatments may be declining. Later seeded canola crops should still have protection from flea beetle feeding but should also be regularly monitored. Scout for flea beetle damage and prepare to take action if damage reaches 25% defoliation (as shown in the photo) in patches or across the field. Some growers have already sprayed. Pay careful attention to flea beetle feeding in fields thinned due to frost or other factors. Sprays should only be used when necessary, but when evaluating the threat, consider lower thresholds when canola stands are thin and advancing slowly. The economic control threshold may be lower than 25% defoliation when there are fewer than 4-5 plants per square foot, if flea beetles are still actively feeding in significant numbers. Click here for images of 10% to 90% defoliation. Grasshoppers. This is the No.1 issue in the Peace River region this week. Migratory and two-striped grasshoppers have reached threshold numbers in wheat fields and have caused damage along the edges of some canola fields. The Prairie Pest Monitoring Network report for this week says egg development has been greatest in Alberta so far, particularly in the Fort Vermilion area. The maps below show that the egg hatch has only just begun. Click the following provincial links for help with grasshopper monitoring: Alberta Saskatchewan Manitoba
Wireworms. These are the biggest insect threat this week in west central Saskatchewan. While insecticides are not available to control wireworms in canola, it helps to identify whether wireworms are indeed the cause. Cutworms cause similar damage and cutworms can be controlled with insecticide. Other insects such as crane fly larvae, Therevid larvae (stiletto fly), and others may be found in canola fields but would not be damaging the crop. Click here for information about wireworms versus cutworms. Diamondback moths. Traps in southern Alberta and Manitoba are catching higher numbers with every passing week. In Saskatchewan, diamondback moths were picked up in low numbers in traps this week near Swift Current and late last week at locations near Rosetown (west central), Regina and Avonlea (south central). Growers will have to pay attention to larvae numbers when more hatch and we get additional generations later in the summer. Insecticide/herbicide tank mixes: Some growers are looking at insecticide and herbicide tank mixes to save on application costs. This is allowed under PMRA rules as long as both products are registered for the intended use, but some products may be antagonistic or incompatible with each other. Check with your retailer before trying a tank mix for the first time. Sprays should only be used when necessary, but when evaluating the threat, consider lower thresholds when canola stands are thin and advancing slowly. Tips to control hard-to-wet weeds For these weeds:
Overwintering canola. On the topic of hard-to-wet weeds, some growers with unseeded acres have large overwintered canola plants to contend with. Canola that emerges in the fall can survive the winter and have a head start in the spring. Some of these "weeds" are already bolting. After the 5-leaf stage, canola develops its waxy cuticle and is hard to control. Aerial application now may be the best choice if it will be a few weeks before the ground sprayer or cultivator can get on the field. Spraying Liberty with no sunshine. Liberty works best on warm sunny days, but some growers have waited a long time for a warm, sunny and calm day. The weeds can't wait any longer. If you have to spray Liberty on a cloudy day, increase water volumes and consider spraying later in the day when temperatures are at their highest. Flush sprayer tanks properly between products A water rinse is not usually enough to remove herbicide residue from the sprayer system. Herbicides can bind to the tanks and hoses, and most need water plus a cleaning solution to remove them. If not, you never know when the bound herbicide molecules will be released. Some surfactants do a very good job of scrubbing a week's worth of herbicide residue from the sprayer system, creating an unexpected and damaging tank mix. Talk to your retailer about effective tank cleaners. For detailed sprayer tank clean out instructions, read page 14 in the Introduction section of the Saskatchewan and Manitoba Guides to Crop Protection. End the day with an empty tank. A University of Missouri factsheet recommends that sprayer operators end the workday with an empty tank. It says: If you will be using the same agrichemical the next day, thoroughly flushing the sprayer tank and sprayer with clean water is sufficient and will help prevent drying and hardening of pesticide residues. If a different agrichemical will be used, then a more comprehensive procedure is recommended immediately after use. Spraying a multi-stage crop If most plants are within the spray window, then go ahead and spray. Choose a spray rate that will control the largest weeds - as long as there are enough of these large weeds to reduce yields. If large weeds are few and far between, then you could consider a lower rate. Assess the threat. The first emerged and largest weeds are the biggest threat to yield. Herbicide carryover can stop emergence Dry conditions or saturated conditions can extend the period required for herbicide breakdown. For this reason, carryover damage may be occurring when it wasn't expected. In the Peace region, some canola seeded into pea stubble is showing signs of possible group-2 herbicide damage. The Peace was dry last year and herbicide breakdown may have been slower than expected. Damage from herbicide residue can also be worse when it rains after a few weeks of dry weather. In this case, clay particles can release herbicide molecules they had taken up earlier. Symptoms for herbicide carryover are generally the same as symptoms when the wrong product is accidentally sprayed over the crop. There are different symptoms for the different herbicide groups. Hints that soil herbicide carryover may be the cause:
Click here for a table showing herbicide carryover. Management for a thin stand The minimum critical plant population for canola is 4-5 plants per square foot. At that level, canola can still yield 80-100% of an ideal stand. The Canola Council of Canada suggests a target of 7-10 plants per square foot to allow for some plant mortality. Stands of 1-4 plants per square foot can provide a reasonable yield that will often outperform a late seeded crop with higher plant density, but this is not an ideal target. These thin stands need extra attention all season long, may require more crop protection investment than an ideal stand, and will likely mature later.
Step one with a thin stand is to determine the cause so it can be prevented next year. Cold soils, dry soils and frost will thin a stand, but so can insects, diseases, and equipment issues like worn openers, seeding too deep, seeding too fast and using seeding rates that are too low. Many of the fields that were broadcast seeded appear to have the poorest stands, but there are differences among them depending on residue levels and how they were managed. Click here for more scouting tips. Step two, growers have to take extra care to protect the stand from insect damage and weed competition. Manage insects: The lower the plant density, the fewer insects needed to reach the action threshold for control. For example, canola in the Canola Council's Canopy Manipulation Trial in 2002 at Yorkton, Sask., experienced moderate to severe flea beetle pressure. Treatments with an average of 2-3 plants per square foot reached the action threshold of 25% defoliation 8 days after emergence. Treatments with 8-9 plants per square foot reached the action threshold at 20 days after emergence. Crops with low plant densities require more frequent and intensive scouting for insects at all plant growth stages. Manage weeds: Weeds can dramatically reduce yields through competition with the crop for light, moisture and nutrients. Depending on weed type, density and stage of development, yields can be reduced by 5% to over 50%. Removing stress from early weed competition early is essential, but a second application may also be required if the thin stand takes a few weeks to reach canopy closure. Sclerotinia risk increases: Because thin stands have more branches per plant, this extends the flowering period and increases the risk of sclerotinia infection. Prepare for delayed maturity, harvest difficulties, and fall frost: Extra branching that you get with a thin stand can delay seed maturity up to 21 days depending on environmental conditions. This delay raises the fall frost risk, which can result in a more challenging harvest and lower quality. Coming events Canola and inter-row seeding crop walk, June 16 at 1:15 at the Lethbridge Research Station, Lethbridge, Alta. Click here for more information. Lethbridge Research Station crop walk, June 23 at 1:15 at the station in Lethbridge, Alta. CCC agronomy specialist Troy Prosofsky will be present to answer canola questions. Manitoba Canola Growers Association is helping host a combine clinic with Enns Brothers June 28-30 in Portage la Prairie. CCC agronomy specialist Kristen Phillips will speak on June 28 and June 30. CCC crop production resource manager Derwyn Hammond will speak on June 29. Click here to register. Crop Diagnostic School in Carman, Manitoba is July 5-8 and July 11-15. Click here for more information. To register call 204-745-5663. Combine Clinic. The Canola Council of Canada will host a Combine Clinic in Westlock, Alta., July 18 and 19. Click here to register. The Canola Council of Canada's Convention is July 26-28 in Saskatoon. The theme is "Global Farmers. Global Markets." Click here for more information and to register.
For more information, contact a Canola Council of Canada agronomy specialist in your region:
This media release is supported regionally by: Alberta Canola Producers Commission; SaskCanola; Manitoba Canola Growers Association; Canola Council of Canada; Peace River Agriculture Development Fund; B.C. Ministry of Agriculture & Lands.
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