The later hail occurs in the season, the more damage it can do to yield. Canola can keep flowering to compensate from hail that occurs during flowering. And plants that were past flowering can start to regrow, going through flowering stages again. But these very late plants often cannot mature in time.
Harvest planning for late-season hail. Shattering risk increases for hailed pods (although pod-shatter tolerant canola can be more resilient.) Before jumping the gun and swathing too early, take these decision-making steps:
1. Assess where most of the crop yield will come from. If most of the yield will come from undamaged pods lower in the canopy, swathing after 50-60% seed colour change when those pods have reached full size will probably contribute more to yield than swathing early to save hail damaged pods. Note that hail tends to damage top pods more than lower pods, and top pods make a much lower contribution to yield.
2. After hail on podded canola, increase crop walks for the following week to check lower pods. Damage to these lower pods may not be evident immediately after a hail, but bruises can show up after a few days. Seeds either side of a pod bruise will likely dry up, and bruised pods are more likely to shatter prematurely. If lower pods — pods where the yield is — have high levels of damage, then earlier swathing may be warranted.
3. Be prepared to swath quickly if pod bruising is widespread. However, swathing before 20% seed colour change is counterproductive.
Treatments. Time and moisture are the best treatments for hailed crop. While we’d like a product to assist in hail recovery, to date it appears a well developed root system, moisture and time are all we can count on.
If applying any treatment on hail-damaged crops, keep in mind that there is very little research available on the efficacy of any product for this purpose. Leave appropriate check strips in order to make an accurate yield comparison at harvest. Note pre-harvest intervals if applying a fungicide.