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Story Posted: August 18, 2010 Canola Watch 17: How to harvest diseased and hailed crop In This Issue: Tips for harvesting diseased fields, Swathing better than straight combining for hailed crop, Harvest tips for short and lodged crop, Lygus up to 10x thresholds, Questions and contacts. Issues of the week Crop and weather reports Alberta: Crops in general are a week to 3 weeks from swathing, the latest fields being in the south. Swathing has just begun for the earliest fields, but heavy rain the past week in some areas — St. Paul, for example, got 4" in one storm — has refilled low spots and hampered field access. The province needs warm and dry conditions to mature the crop, which looks very good to this point. Read the Alberta crop report. Saskatchewan: With rainfall and cooler temperatures in the past week, most fields are still 10 days to 2 weeks from swathing. Some southern fields are swathed already and general swathing is close for that region. Swathing will start by this weekend, if all goes well, for the earliest fields in areas north of Saskatoon. Yield potential ranges widely. Read the Saskatchewan crop report. Manitoba: Some fields in the south central region have been combined, with yield reports in the 20-50 bushel/acre range. Swathing is fairly general across the province, except in the northwest where general swathing is still at least a week away. Rain across the province in the past week, including up to 5" in the Killarney area, has slowed progress. Read the Manitoba crop report. Quick Hitters Careful with Reglone on canola. Reglone does not hasten crop maturity. It shuts the plant down quickly and basically STOPS it from maturing, which can lock in high green levels. In 2009, there were a number of situations where growers applied Reglone to late maturing canola crops with the assumption that seed maturity would be accelerated. Unfortunately, the results after harvest showed very high green seed counts in samples sprayed with Reglone. The label is clear that Reglone should be used as a last resort for lodged canola crops only. Growers using Reglone on canola to be straight combined take note: Reglone can significantly increase both pod shatter and pod drop if harvesting is delayed, so be prepared to combine as soon green seed and seed moisture have reached suitable levels. Think recropping restrictions on fields planned for canola in 2011. Click here for the list of products with residual action, including those registered for pre-harvest and post-harvest application. For more details on any of these products, please read product labels and your provincial guide to crop protection. Click your province for a link to your guide: Alberta , Saskatchewan , Manitoba. Flea beetles have returned. We’ve had a few calls about flea beetle feeding late in the season. It’s not something to worry about. In her research, Julie Soroka with AAFC in Saskatoon found no effect from fall flea beetle feeding at numbers as high as 350 beetles per plant when canola is at translucent-seed to green-seed stages or later. She adds that this work was done in non-drought conditions. Open pods to determine seed colour change. The ideal swathing time for yield and quality is when 50% to 60% of seeds on the main stem have at least some brown spotting on them. To determine this, you have to get into the field, identify the main stem, and then start opening pods from bottom to top. For more tips, click here to hear CCC agronomy specialist Erin Brock on ACPC radio and click here for a CCC how-to video. Empty pods. While checking canola for seed colour change, farmers in dry regions of the Peace are noticing blanks on stems and that many pods are empty. These are common responses to drought stress, as Murray Hartman, Alberta oilseed specialist, noted in his ACPC webinar of July 7. Click here to view. Pressure from diamondback moth larvae is dropping in most regions, but some fields will still have high levels. For insight into diamondback moth biology and control, click here for an August 12 ACPC webinar on the pest. The presenter is Lloyd Dosdall, entomologist from the University of Alberta. Tips for harvesting diseased fields 1. Walk the crop and assess the level of disease damage. "Two percent of plants damaged can look like a lot when assessing the field from the road," Moisey says. 2. If the number of diseased plants and disease severity are low, don’t alter harvest plans. 3. If infection rates are high, as suggested by the photo below, growers need to determine where most of their yield is. If it’s in the healthy plants, then make harvest decisions based on what’s best for the healthy plants. That means swathing at 50% to 60% seed colour change for ideal yield and quality. If most of the yield is in the infected plants, then earlier swathing — at 30% to 40% seed colour change — may be more appropriate. But make sure seeds in pods on branches and upper main stems are firm. Diseased plants will dry down prematurely, which is why swathing earlier is recommended. The sclerotinia fungus may continue to grow on swathed canola if conditions are wet, but seeds that have reached the firm green stage or later should still mature. 4. When swathing diseased crops, be careful when using a swath roller. Lift the roller so it doesn’t pack the windrow too aggressively. This will protect the pods of those damaged and more advanced plants. Also, if weather conditions after swathing remain damp, compacted swaths can hasten development of sclerotinia in the swath. 5. Canola with severe sclerotinia infection can be very dusty when combined, due to the growth of the sclerotinia fungus as well as other moulds that can attack the decaying plants. We recommend growers wear a mask when handling severely-diseased canola.
Swathing better than straight combining for hailed crop Often the best way to manage canola with late-season hail damage is to swath the crop instead of straight combining. That way damaged pods don’t shell out while the grower waits to straight combine the crop. Also, bruised seeds — which generally will not mature — will have time in the swath to shrivel up so they blow out the back of the combine. Keys to the decision:
Harvest tips for short and lodged crop Here’s a recap of tips for swathing short lodged crop:
Lygus up to 10x thresholds Economic thresholds at pod ripening are 8-20 adults or late instar bugs per 10 sweeps when canola prices are $10 to $12 per bushel. (See the first table below for more details.) At these numbers, spraying is warranted to save yield but remember the pre-harvest intervals. Products with the shortest pre-harvest intervals still require 7 days between spraying and cutting, so if the field is within a week of swathing, then spraying is no longer an option. (See the second table below for a table of pre-harvest (pre-cutting) intervals.) In fields that close to cutting, many pods are hardening and lygus will not be able to penetrate and cause damage anyway. In severe cases, swathing a little earlier than recommended — perhaps at 30% to 40% seed colour change instead of the ideal 50% to 60% — may be the best solution.
Questions and contacts If you have questions on regional issues, contact one of the following Canola Council of Canada regional agronomists or provincial oilseed specialists:
This report is supported by each of the provincial canola grower associations. For more information on some of their activities, check out the following links:
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