Story Posted: May 18, 2011

Canola Watch: Seed to moisture, Flea beetles feeding, Cutworms

Issues of the week: Strong winds have dried out the top inch of soil in many parts of Alberta and western Saskatchewan. Many canola fields could use a rain, as growers are seeding deeper to hit moisture. While growers rush to seed, take time during each day to scout for flea beetles on emerging crop, especially if wind has driven them down to feed on stems and undersides of leaves. Thresholds are lower for stem feeding.

Crop and weather update
Peace (B.C. and Alberta): Canola seeding is around 25% complete across the region and progressing well. Warm temperatures and high winds have dried out the topsoil, and many growers are seeding deeper to hit moisture.

Alberta: Canola seeding progressed quickly over the past week and is over 50% complete in the south and around 25% complete in central Alberta, on average. Strong winds have dried out the top inch of soil and many fields could use a rain to help with emergence. Alberta crop report.

Saskatchewan: Seeding is advancing quickly in the west and north. Areas from Unity to Lloydminster and around Moose Jaw are furthest ahead, with about 50% of canola acres seeded. Eastern Saskatchewan, except for spots hit by a large rain storm in the past week, is drying nicely and well underway. Saskatchewan crop report.

Manitoba: Areas furthest advanced have about 5% of crops seeded, but it could be a busy week of seeding ahead. Sunny and warm days are forecast for the next week or so, and fields are drying out enough to support seeding equipment. Manitoba crop report.

Seeding down to moisture OK in mid May
Seeding deep to chase moisture is rarely a good idea early in the season. In the cool soils of late April and early May, mortality for deep seeded canola can be high and those plants that do reach the surface may not be very vigorous.

But that situation changes with the warm soils of mid to late May. Seeding 1.5” to 2” deep to hit moisture will hasten germination and crop establishment in fields where the top 1” is too dry to allow germination and emergence.

Here are some tips:

• Seed doesn't have to be IN moisture. ON moisture is OK when seeding deeper, because the additional soil above the seed row slows that moisture loss. Make sure the seed row is well packed to seal in that moisture and prevent further drying out.
• Recognize that deeper seeding will increase seed and seedling mortality. Add 10% to the seeding rate to compensate.
• Put starter phosphate in the seed row. Keep rates to 25 pounds of actual phosphate per acre, or lower, for seed safety. The nitrogen component of ammonium phosphate can damage seed and seedlings at rates higher than that.
• Consider the crusting risk. For heavier soils, a rain before canola emergence could create a crust above the seed row. Because deep seeded canola tends to take longer to emerge, the risk of rain before emergence is higher. Bare soils are more prone to crusting than soils with higher surface residue. With wet conditions, growers may have tilled or harrowed soils that they may not have tilled in the past. In this case, the risk of crusting may be increased relative to past experience.
• Heavy rain could also fill in drill runs. Instead of 1.5” of soil cover, it could be 3” if the drill and packer combination creates a deep seed trench that fills with mud after a rain.
• Slow down when seeding deep to more closely manage seed depth for all rows. At higher speeds, back rows tend to throw more dirt over the front rows. Click here for more on seeding speed and click here for more on seeding tips in general.

Look on stems for flea beetles
It could be a heavy year for flea beetle feeding, especially since a lot of canola will emerge right at peak activity for the insect. High winds may force flea beetles off leaf tops and down to leaf undersides and leaf stems. This could actually make the situation worse, since it takes just a few bites on a stem to nip off a whole cotyledon or sever the stem. Stem feeding, if it's happening on a lot of plants, has a lower control threshold than the 25% damage recommended for leaf feeding.

Growers taking advantage of good seeding weather should take a few minutes each day to scout emerged crop. Flea beetles can do a lot of damage in a week, and if growers wait until all crops are seeded before pest scouting, those early crops could be lost.

Seed treatments should still be effective for fast emerging canola, but flea beetles have to feed to take up the insecticide, so some feeding damage is expected. Growers and crop scouts should be vigilant, especially if the flea beetle population has a high proportion of striped flea beetles. Some research suggests the amount of feeding required for control may be greater for this species.

At high numbers, flea beetles may overwhelm the seed treatment protection. Monitor the amount of leaf feeding to determine if this is occurring, and apply a foliar insecticide if the action threshold of 25% leaf area damage is exceeded and flea beetles are still actively feeding. Click here for images that show what different levels of leaf damage look like.

A number of foliar products are registered for flea beetles on canola. To find them, click your province for your guide to crop protection: Alberta Saskatchewan Manitoba.

Benefits of early scouting
Early scouting is important for flea beetle management, as described in the previous article. Early scouting also gives growers a chance to:

• Take a plant stand count. If the stand is limited in some way, this can help you identify steps to improve for next year. Identify any issues with seed placement that may be the result of drill settings, calibration and opener performance. Identifying these issues now will help to improve drill performance for next year. Click here for an RTL article on how to troubleshoot for drill problems.
• Have a baseline for crop emergence and condition of the stand. If frost or some other environmental or pest damage sets back the crop, knowing what was there before the event will help growers identify the extent of damage.
• Identify weed size and number. Determine whether to hold up seeding for a pre-seed application and what rate is appropriate given the weed sizes and species.

Learn to identify pest cutworms
Cutworms are showing up in big numbers in some fields across the Prairies, particularly in northeastern Alberta. Check emerged canola crops for bare patches, holes or notches in foliage, and clipped plants - telltale signs of cutworm feeding.

At least four cutworm specifies may damage canola: pale western, redbacked, army and dingy. Dingy and army cutworms overwinter as larvae, so early in the season they will be larger than species that overwinter as eggs. You're more likely to see bare patches, not clipped plants, with dingy species.

Many species of cutworms can feed for several weeks. If they thin out a crop early, reseeding may not be the best solution if the larvae are young enough that they could still be feeding when the new crop emerges. A lot of glassy cutworms have been found in the Peace region, but this species tends to feed on cereals and stay away from canola.

Current canola seed treatments are not registered for or known to provide adequate control of cutworms, but many foliar insecticides are registered. Cutworms surface at night to do their above ground feeding, so spraying as close to nightfall as possible is recommended. Since not all cutworms will surface on a single night, it may take several days before full effect of the insecticide is achieved.

Scout before spraying. Dig in the ground to a depth of 10 cm and look for cutworms and wireworms. Wireworms can cause similar bald patches to appear in canola fields, but no products are registered (or effective) for wireworm control in canola. Wireworms are a higher risk in canola seeded into land that was in pasture or hayland last year. If wireworms are the culprit, put away the sprayer and make note of areas or fields where the damage was higher. Remember these areas when planning crops and seed treatments for next year.

Click here for a MAFRI factsheet on cutworms, which includes photos. Click here to view the Canola Council of Canada's cutworm webinar from last week.

Spray big weeds before seeding
Seeding is the priority for many growers this week, but fields with lots of big weeds should get a pre-seed burnoff with a high rate of glyphosate before seeding. The herbicide needs only a day or two to get down into the growing point of these large weeds, then the grower can resume seeding. The economic return will be higher than if the grower seeded over these large weeds and then took a chance on getting them sprayed before crop emergence.

Shallow seeded canola can emerge within 5 days under warm and generally moist soil conditions. And since growers need to leave weeds for a couple days to start growing again after the seeding operation, the window for post-seed/pre-emergence spraying is very narrow. With all the wind these days, that opportunity may never come.

Click here for more on weed control under wet conditions.

CleanStart is it for volunteer RR canola
CleanStart is the only registered product for controlling RR volunteers ahead of canola. It may be tempting to try other products, but these products are not registered.

Not only does the use of unregistered products violate the Canola Council of Canada's Export Ready message, but it could also set back the canola crop. Canola damage from pre-seed applications from MCPA and 2,4-D, for example, is well known. The photos below show canola damage from a pre-emergence application of 2,4-D. The result can be purpling of the stem, stunted growth and in some cases, deformation. One seedling in the photo has no cotyledons and no growing point.

The whole point of controlling volunteer canola and early weeds is to give the canola crop a head start. But if unregistered herbicides are setting back the canola crop and thinning the stand, the whole purpose of a pre-seed burnoff is compromised.

Thin stands often better than reseeding
What if a grower calibrated wrong and seeded at 3 pounds/acre instead of 5 pounds as intended? If that seed had a thousand kernel weight (TKW) of 5 grams, the actual number of surviving plants per square foot could be lower than the minimum 4-5 plants required for canola to reach its yield potential. Click here to see how important it is to recalibrate when switching crops or varieties.

Should the grower reseed?

Not likely. This thin stand is not optimal for yield (see the graph below) but a thin stand at the end of May has better yield and quality potential than the alternative, which is reseeding.

The key is to protect those few plants. Thresholds for everything are lower with a thin stand. Watch closely for insects and consider spraying for flea beetles when damage is only 20%. Keep weed competition to a minimum. And know that the large bushy plants that this crop produces will have wider windows of susceptibility for sclerotinia. If the risk is high, a split application of fungicide may be warranted because the flowering period will be longer.

If growers know immediately that they made a mistake with the seeding rate, they could try to overseed to bump the rate. But if the mistake is not known for a couple days, just leave the crop, assess it as it emerges, and manage accordingly. Don't try to overseed because it could damage germinated seedlings and create a multi-stage crop that presents management challenges all season long.

If soil test results are unexpected...
Some growers with very wet fields have seen higher than expected nitrogen levels in their soil test results. This was a surprise because they expected soil nitrogen to be a lot lower since denitrification and leaching tend to be higher with high moisture. A number of factors could have created an inaccurate result. For example, if wet soil samples warm up quickly in the truck cab or house, the warmth can accelerate soil microbes and increase mineralization, creating a false high result. If growers reduce nitrogen fertilizer rates in response to these results, the field may not have the nutrient it needs to match the high yield potential in these moist soils.

Any time you get an unexpected soil test result, it would be worth doing the test again. When taking the new soil test, make sure to avoid the fertilizer band if applications have already been made in the field.

Growers will not want to hold up seeding while waiting for soil test results, but if new test results are lower than the first results, growers could apply an in-crop top up.

Top up also works if growers can't get timely delivery of all the fertilizer they need. With so many growers seeding hard at the same time, some fertilizer dealers are having trouble keeping up with demand. Growers may opt to go with what they have for now and then top up later.

For more information, contact a Canola Council of Canada agronomy specialist in your region:

• Kristen Phillips, agronomy specialist, Manitoba, phillipsk@canolacouncil.org, 204-761-2143
• Jim Bessel, senior agronomy specialist, Central Saskatchewan, besselj@canolacouncil.org, 306-373-6771
• Shawn Senko, agronomy specialist, Eastern Saskatchewan, senkos@canolacouncil.org, 306-270-9307
• Clint Jurke, agronomy specialist, Western Saskatchewan, jurkec@canolacouncil.org, 306-821-2935
• Dan Orchard, agronomy specialist, Central Alberta, orchardd@canolacouncil.org, 780-777-9923
• Troy Prosofsky, agronomy specialist, Southern Alberta, prosofskyt@canolacouncil.org, 403-332-1412
• Doug Moisey, senior agronomy specialist, North Central Alberta, moiseyd@canolacouncil.org, 780-645-9205
• Greg Sekulic, agronomy specialist, Peace Region, sekulicg@canolacouncil.org, 780-832-2382

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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