Sunday night, many areas in Ontario received a frost. The overall impact is minimal
Wheat that is at flag leaf stage is well protected. We had harder frosts in the mid 80s with no impact on wheat. The one that I remember was June 12 or 13, 1972 when I was doing my masters. I had some corn in my plots frozen that night. The wheat that year was OK.
The cold weather may mean an end to weed control in wheat. Some herbicides can be applied “to early flag leaf.” By the time weather warms the flag leaf may be too far extended in most fields. The bit of yield you get by applying herbicides now may not be worth risking damaging the wheat. You may have to switch to a preharvest treatment. You can still spray fungicides on wheat.
Corn crop is OK. Earliest planted fields (first days of April) were at the two-leaf stage. They will be frozen and grow back. Larry Cowan’s March planted corn is frozen for the fourth or fifth time. It will grow back. (Larry farms in Middlesex County).
Applying burndown with residual herbicides will continue. It is not the best conditions for spraying burndown but it may be better than waiting and spraying when the weeds are even bigger. BF