09 Feb The perfect tumbleweed storm
If you haven’t seen a fence line like this, you haven’t driven through Special Areas lately. The culprits: kochia and Russian thistle, and even sometimes common baby’s breath (but that’s a story for another day).
Why are we seeing this uptick in tumbleweeds? The answer may be a perfect tumbleweed storm.
Kochia and Russian thistle are just two of many species that use tumbling as a method to spread seeds (15-25,000 seeds per kochia plant or 200,000 seeds per Russian thistle plant) across great distances. Both species are introduced (non-native) summer annuals in the Amaranthaceae (pigweed) family that share a somewhat unique photosynthetic pathway not too common to our part of the world (only 3% of vascular plants) called the C4 pathway. These warm season (C4) plants use special bundle sheath cells to allow photosynthesis (and therefore plant growth) to occur in dryer, hotter environments than C3 plants (cool season plants). This adaptation is likely one of the major contributing factors to our tumbleweed woes occurring in Special Areas – I don’t have to explain to you that we’ve been experiencing hot, dry conditions.
Kochia and Russian thistle are currently not listed under the Alberta Weed Control Act and therefore are not legislated to be controlled. Kochia, in particular, can tolerate high salinity conditions, often making it an invader of marginal lands in Special Areas, spreading across the landscape with winds. It also has played an important (but risky) role in livestock feed during the drought, as it can have high protein content if harvested correctly. This can contribute to producers actually encouraging its growth, and furthering spread through livestock feed movement as kochia seeds will not be destroyed by the rumen of a cow. Russian thistle has a poor forage value as it is only edible for a short time after seedling stage as it becomes very spiny, woody and unpalatable to livestock.
For those who have been trying to control kochia, Russian thistle, and other weeds, drought conditions have proven to be another challenge. Not only is group 2, 4 & 9 confirmed herbicide resistant kochia present across the prairies, timing becomes a challenge for those plants still susceptible to treatment. Systemic herbicides (most herbicides, including glyphosate or “round up”) must be translocated throughout the plant from the point of contact (leaves) to the roots to achieve control. In order to do that, they must first be absorbed into the leaf. In hot, dry conditions plants form a waxy cuticle to prevent water loss which also prevents herbicide uptake. When temperatures continue to climb, the plants stop photosynthesizing and therefore stop translocation of water, nutrients, and any herbicide that did manage to enter the plant. When your plant slows or stops growing, your herbicide is ineffective.
So what can we do to control kochia and Russian thistle?
Do we learn to live with it? What do we do with those miles of fence buried in tumbleweeds like a bad western movie? Will a break in drought conditions bring relief?
Find out by tuning into our free March noon hour webinar series! Register now.