Current forecast is for fairly warm temperatures through late evening Tuesday evening, followed by a substantial drop in temperatures and chance of snow, followed by cold/cool temperatures through the weekend. Primary question concerning this scenario seems to be whether it is okay to apply wheat or burndown herbicides prior to this cold snap. Some things we know about herbicides and cold weather:
Though the current cold snap has caught our attention, we are actually ahead on heat units compared to this time last year, and we’ve accumulated enough degree days to see potential outbreaks of alfalfa weevil in some locations. Weevils have already been spotted in northwest Ohio. Overwintered adults begin laying eggs when temperatures exceed 48°F. Peak larval activity and feeding damage occur between 325 and 575 heat units (based on accumulation of heat units from January 1 with a base of 48°F). Current (Jan. 1 – Apr.
We have begun collecting two important pest in our expanded trapping this year—true armyworm and black cutworm. True armyworms feed on wheat before moving on young (typically late-planted) corn. Black cutworm can feed on young corn and even completely cut plants.
The weather forecast this week is indeed concerning for forage stands in general and especially for alfalfa and red clover. The low night temperatures in the forecast may potentially cause severe frost injury to both annual forage crops (e.g. winter rye and winter triticale) and perennials forages.