Questions of the Week

How to help canola recover after hail?

Canola can generally recover after early season hail so long as it doesn’t break off the growing point. Be patient: give the crop several days post-hail before making any decisions. Though it can be tempting to ‘try something’, no post-hail rescue products are proven. Since ‘miracle cures’ that appear to have incredible results are likely getting credit for canola’s natural ability to branch and regrow, always leave check strips. Branching can often compensate for hail damage, but the crop will be at higher risk of sclerotinia due to extended flowering and will mature later. (Will canola recover from early season hail?) (Canola usually recovers from early season hail) (Hail from 4 leaf to flowering)

How high is the sclerotinia risk?

A dense crop canopy and high humidity — currently the case in many to most Canadian canola acres – are ideal conditions for the development of sclerotinia. At an infection rate of 10% or more, it typically pays to spray. Make a management plan now, as fungicide timing is critical. Fungicide is already in high demand so book product now. The Canola Council of Canada has released a new sclerotinia risk assessment tool. More details available here. (Factors in the sclerotinia spray decision) (Top 10 sclerotinia stem rot questions) (Weather based assessment of sclerotinia stem rot risk)

Is it too late…

… For top-dressing? It’s still worth considering adding nitrogen if yield potential is higher than available fertility, or if you suspect that previously applied nitrogen has been lost in saturated soils. Remember, canola will need 2.5 to 3.5 lbs of nitrogen to produce one bushel. The crop can make effective use of a top-up up to the 6-leaf stage; any N added at or after flowering won’t be as useful this crop year. Keep in mind that added nitrogen will extend the growing season; therefore, ask: are growing days before frost a concern? Top-dressing a weedy field will feed the weeds. (Tips to apply nitrogen and sulphur in season) (Volatilization losses from surface applied nitrogen) (Canola Encyclopedia: Nitrogen)

… For weed control? Early weed control is still a critical priority. Scout for misses, whether sprayer misses or herbicide misses. In fields with cleavers, remember quinclorac needs to be applied before 6-leaf. (Weed control strategies for each HT system) (Spray early: Economics of early weed control)

Why wait to spray for cabbage seedpod weevil?

Cabbage seedpod weevil (CSPW) are now starting to look for somewhere to lay eggs. Though the adults will feed on buds, it’s important to wait to spray until the critical control window at 10% flowering because:

  • Economic losses from CSPW are almost entirely due to weevils laying eggs in young pods, not adults feeding. 
  • CSPW move very easily between fields. Spraying too early means a second spray will likely be required and limits later-application insecticide choice. 
  • Low levels of bud feeding can cause a defense response in healthy plants, causing them to flower longer, positively impacting yield. Click here to read the research behind this phenomenon.

Scout now! In addition to CSPW, priority pests this week include: grasshoppers (still mostly in low numbers), flea beetles (which may be at economic threshold in some fields), lygus bugs (which have no official threshold but are a concern on budding canola or rosettes), as well as diamondback moths and bertha armyworms. (Cabbage seedpod weevil scout and control tips)

Where to get current pest updates?