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Understanding the Critical Role of Broadleaf Pollinator Plants in Pastures

Updated December 19, 2018

Pete Bauman

SDSU Extension Range Field Specialist

An orange and black monarch butterfly resting on a purple flower.
Monarch butterfly on blazing star plant. Courtesy: Matt Morlock

Generally speaking, ‘pollinators’ refers to the suite of plants that produce nectar and pollen (generally flowering broadleaf plants) and the insects and other animals (birds, bats, etc.) that spread the pollen for plant reproduction. In the last several years, the honey bee has been at the center of the pollinator discussion, as their populations have crashed – placing bee keepers and their fruit and nut producing clientele at risk. Along with honey bee decline has come the dramatic decline of local butterfly species, including the iconic monarch butterfly.

Much of our success in food production can be attributed to technological advances. For instance the advent of chemicals for weed control has made farming something quite different than it was decades ago. Along with the cropland chemicals, advancements in chemicals formulated for broadleaf plant control in pastures also continues to develop. These chemistries can be a great tool, but they can also be detrimental. As with any tool, the tool itself cannot be heralded or demonized……it is the appropriate application of the tool that creates successes and failures.

There are many factors that play a role in the overall decline of pollinators. Use of herbicides and insecticides in crop production and conversion of native grasslands to farming are viewed as major contributors. However, we cannot overlook the critical responsibilities of pasture managers in this discussion. On one hand, if it were not for our remaining native pastures many of our pollinator species would be in worse peril than they currently are and our ranchers should be applauded for their efforts in protecting grasslands. But in fairness, if it were not for current pasture management philosophy many of our native broadleaf pollinator species would be more abundant than they are, and pasture managers should seriously consider their responsibilities in that regard.

Producers often look at pastures through the same lens that they view cropland. A common desire is to want the pastures ‘cleaned up’. Simply stated, this means removal or control of anything perceived to be unpalatable to cattle or any species simply not recognized as contributing to the pasture ecosystem. Through heavy stocking rates and broad scale chemical applications, we’ve collectively managed our pastures toward grass-only systems that not only impede the survival of broadleaf plants, but also impede the sustainability of our best native grasses. Often, this leads to weed problems.

This point will be illustrated plainly over the next several weeks as South Dakota’s pastures come to life with mid-summer flowers. The early green-up will primarily be the result of heavy infestations of Kentucky bluegrass and smooth brome that have largely replaced native cool season grasses. Both are non-native exotic grasses that, although palatable early in spring, can indicate poor range health. Look closer and these are the same pastures that are prone to wormwood sage, leafy spurge, thistles, and mid-summer browning due to lack of native warm-season species.

The challenge in range management is balancing legally required management (such as the control of noxious weeds) with integrated management tools that allow our native systems to flourish. For example, identifying early infestations of invasive species and either chemically spot treating or mechanically removing them is much preferred to the alternative of waiting for the problem to grow and then reacting by attacking in full force with non-selective herbicides formulated primarily for grass-only retention. Pasture management should be focused on true objectives rather than perceived problems. Managers who consider pasture production and diversity as a top priority have a much different ‘weed management’ program philosophy than those focused solely on ‘cleaning up the pasture’.

Cattle will include a great many broadleaf plants in their diet if given the opportunity, up to 20% or more. These broadleaf plants play a critical role in the overall function of rangeland nutrient cycles and soil health. Infestations of common plants such as ragweed, goldenrod, gumweed, buckbrush, prairie coneflower, and other less desirable native broadleaf plants may indicate a need for a shift in grazing management rather than a 3-4 year spray rotation. Although judicious use of chemicals for targeted control of certain species may have a place in a well-managed operation, the advanced producer will ask himself/herself if their own management methods are the primary cause of the weedy infestation and thus the need to apply broadcast chemicals in the first place. Careful evaluation of targets may indicate that emphasis on asking ‘why’ weeds persist rather than simply focusing on the weeds may lead to more efficient distribution of input expenses (labor and chemicals), resulting in improved and long-term rangeland health and profitability.