crops Pest Patrol: Canada fleabane in an organic hay crop – Country Guide

crops-pest-patrol:-canada-fleabane-in-an-organic-hay-crop-–-country-guide

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Published: June 10, 2021

Crops

Figure 1 (left). A bolted Canada fleabane plant the day following a frost event where nighttime temperatures reached -3.3 C; Figure 2 (right). The same bolted Canada fleabane plant the following spring (March 2021). Photo:

Supplied

Q: I have a lot of Canada fleabane in my organic hay crop. Is it a problem to feed? How do I get rid of it?

It’s not great to have Canada fleabane in your hay crop. It’s an alternative host for plant feeding insects such as tarnished plant bug, and the leaves have irritated the nostrils of grazing horses, according to one source1.
That said, it is important to note that Canada fleabane is not poisonous to livestock. However, like many weed species found in hay stands, it can be less palatable than the desired forage species. It contains limited protein and digestible fibre, and it can make the crop higher in moisture content, requiring more time to dry down.
A livestock nutritionist should be consulted if forage stands contain a high proportion of Canada fleabane, so adjustments can be made to feed programs. 
Prevent bolted plants from setting seed. They will not overwinter

A bolted Canada fleabane plant will be killed after the first heavy frost (Figure 1 at top) and will not overwinter (Figure 2 at top) compared to its counterparts at the basal rosette stage (Figure 3 below). Canada fleabane will only overwinter when it’s in the basal rosette stage. Rosettes can die over the winter if their root system is not developed enough to anchor the plant in the soil so that it can withstand being “heaved” out of the ground by freeze and thaw cycles. Figures 4 and 5 (below) show basal rosettes that range in size, but their root development has allowed them to successfully overwinter. These plants will then begin to bolt, flower and set seed.

Figure 3. A basal rosette of Canada fleabane that was unaffected by the same frost event where nighttime temperatures reached -3.3 C. This plant successfully overwintered.

photo:
Supplied

Therefore, the best strategy to deal with Canada fleabane in an organic hay crop is to mow bolted plants every time they begin to flower to stop seed production. Sure, they will grow back, branch out and try to flower again, but if you continue to mow, eventually the plants will run out of time and the “killing frost” will finish the job and break the cycle of weed seed returning to the soil. 

Figure 4 (left). Canada fleabane basal rosette that was less than 3 cm in diameter heading into winter but had a good enough root system to successfully overwinter; Figure 5 (right). Canada fleabane basal rosette that was larger than 10 cm in diameter heading into the winter and with a root system that can withstand light tillage.

photo:
Supplied

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