Why scout for disease after harvest?
Harvest means the end of the crops, but the job’s not done yet. A thorough field scouting after harvest is important to provide insight into the future wellbeing of your crops.
There are still insects & diseases to inventory. Knowing they’re there when we’re rotating crops & managing fields allows us to understand what potential diseases or problems might have come with the seeds.
Post-harvest scouting avoids missing clues due to a thick crop canopy like canola in mid-season. Also, some diseases come later in the season, after you would scout for diseases.
Some considerations for pests & diseases during post-harvest scouting are:
- Lifecycle & when/why they’re an issue
- When to look
Scouting for Sclerotinia
Sclerotinia spawns late in the season and a fall scout means its already done its damage. However, post-harvest scouting makes it easier to assess the extent of the damage. It provides a better understanding of the disease prevalence and informs decisions on crop rotations.
Infected fields benefit from an extended crop rotation that allows more time for the disease to die off between host crops.
Here are some quick tips for dealing with Sclerotinia:
- Right after harvest assess 50 stems using a W pattern in the field
- Soft rotting stems are likely the sclerotinia. Squeeze damaged stems under moist conditions and if they are mushy it is sclerotinia, dry stems will shred apart easily leaving fibers, and finding black sclerotia in a stem is a clear indication of infection.
- Use a 0-100% scale to record the severity of the plants and use the data to calculate incidents. Data can be used to make management decisions.
- Straight-cutting can give you a better chance to inspect the crops; after the combine finishes a row, you can move into the field to scout ahead before the next row is cut
For more information on how you can combat Sclerotinia, you can visit: www.canolacouncil.org/canola-encyclopedia/diseases/sclerotinia-stem-rot
Scouting for Blackleg
A canola disease that develops later in the growing season. It can be an issue to scout for but it’s not going to give you an idea of the whole field. Assessing after harvest lets you get a better grasp of problem areas and the reach of the disease.
Here are some quick tips for dealing with Blackleg:
- At harvest is the best time to look for basal cankers that have formed in the stems
- Assess 50 random plants using a W pattern in the field
- Clip off the roots from the stems and look for blackened tissue inside the crown of the stem
- Use the zero to five rating scale found on the canola council website to assess the level of damage present and make management decisions
For more information on how you can combat Blackleg, you can visit: www.canolacouncil.org/canola-encyclopedia/disesases/blackleg/#scouting-tips
Scouting for Pests
Farming Smarter is involved with the Alberta Pest Monitoring Program, together we examine the prominence of Wheat Stem Sawfly and Wheat Midge to get a forecast for the following year.
Wheat Midge & Stem Saw Fly can be scouted for at the same time. Stem Saw Fly larvae will cocoon inside 0-2 cm stubble; Wheat Midge larvae is found in soil samples that we send into a lab. Scouting for these pests allows us to plan for future pest management.
If you’re interested in pest scouting at your own farm, here’s what we do when we scout:
Wheat Stem Saw Fly
- Take a 1-metre measuring stick & a garden trowel
- Sample 4 sites 50 metres apart along the field edge (4th or 5th row in)
- Count the number of long stems cut by the swather and the number of short stubs (with closed tops) cut by saw flies. It can be easier to find the stubs if you pull or dig up the stubble. Feeling for the stubs that are not easily distinguishable from swather cut stems is recommended. The stubs will feel more solid and rough at the cut point then the unaffected stubble.
Some tips we have for dealing with Wheat Stem Sawfly:
- Cocoons make stubble tougher; it’s a notable difference you can feel
- They usually cocoon 0-2 cm above ground
- Before or after assessing for wheat stem saw fly you can take soil samples to send to a lab to assess for wheat midge larvae
- With a bucket and a soil sampler walk in a horseshoe pattern into the field and take 17 (3/4-inch core) to 10 cores (1 inch core) 10 meters apart.
Some tips we have for dealing with Wheat Midge:
- Swath ASAP; there’s a potential to save infested stems
- They’re more susceptible to pesticides
Post-harvest scouting of pests can also be beneficial. It shows what insect pressure you have in your crops. If Insects can burrow over winter, it provides insight into what your crops dealt with this season and what you can expect next time.
Tips for Management Practices
Here are some management practices that can help you combat pests and diseases at your farm:
- Learn how to identify pest damage; a change in the firmness of the stalk can help identify the presence of a pest or disease
- Consider your rotation times; increasing or decreasing the number of rotations between your crops can help with starving out the pest/disease
- Harvest earlier; an early harvest can increase your chances of catching the larvae before it has a chance to move below cutting heights