Weed Management – The Cost of Doing Nothing

This little thought-piece was originally prepared for the Wyoming Livestock Roundup several years ago, but requests come in every now and then from different sources for it. I thought I would share here so it is more easily available.

Every now and then I get a quiet weekend afternoon to take some time for myself. I sometimes take advantage of it by enjoying a book in the shade, walking the river trying to find a trout on the rise or some other creative form of ‘doing nothing.’ Sometimes I am able to temporarily forget about the ‘to do list’ for work and home, and it can be quite rejuvenating. At other times, my peace of mind is constantly bombarded by the realization that my R & R will lead only to an increased workload once it is over.

 When making decisions for business or personal reasons one must ensure that benefits exceed the costs, particularly in today’s economic climate, but actions that seem to produce temporary savings today may lead to increased costs in the future. If left unmanaged for even several years, invasive weeds are capable of expanding rapidly, with exponential increase in the negative impacts (such as reductions in livestock forage, crop production or wildlife habitat) felt by the landowner or manager. The decision to implement a weed management program should be evaluated within the context of the particular situation, whether it is a smaller acreage property, a ranch agribusiness or a multi-thousand acre federal grazing allotment. Here we explore the potential impacts of deciding not to actively implement a weed control program or to discontinue an existing program on your property…making the decision to do nothing.

 Invasive weeds are capable of rapid spread from existing populations. Although expansion rates vary among weed species and due to site-specific conditions, we can make some assumptions based on published literature. Small, newly established populations have been documented to expand at rates of up to 60% per year. As infestation become large, rates of expansion may decrease for several reasons, but driven largely by resource limitations. One study indicates an expansion rate of 24% per year over a twenty year period averaged across 14 weed species in the Western U.S. Larger infestations lead to larger losses in usable forage for livestock or wildlife. As an example, a 100 acre leafy spurge infestation in rangelands that normally produce 0.3 AUMs per acre can result in an annual forage loss of 30 AUMs (assuming no forage use from infested acres). Over a 10 year period, you will have lost at least 300 AUMs worth of forage; with the assumption that the infestation did not increase in size. Private grazing leases may be up to $20 per AUM, so this particular leafy spurge infestation may cost a rancher up to $6000 over a 10 year period…not to mention the cost of hay to replace lost forage.

 As individual infestation size increases, the cost of control increases while the probability of eradication decreases. Larger infestations will cost more to control, by default, because more labor and control materials are needed to cover the larger area. Other, less obvious factors also increase potential costs of management. As weeds persist longer in an area and become more dense, the likelihood of controlling the population with a single method decreases: integrated methods including seeding of desirable species may be required. A publication from the University of Nevada discusses the change in costs associated with delaying control on a 75 acre infestation of perennial pepperweed with an expansion rate of 20%, but similar patterns would hold up for other weeds as well. Initial project costs were estimated at $12,647. If the project startup was delayed for only 4 years, those costs were estimated to increase to over $26,000 and to over $54,000 after an 8 year delay in initiating control. If a 30% expansion rate was assumed, a 10-year delay in starting control resulted in a first-year control cost of over $170,000. A California study examined 53 separate weed infestations including 18 different species that were targeted for eradication (complete removal of the weed). Only those infestations less than one acre had a high percentage of successful eradication. Infestations above 100 acres had 25% or less success in eradicating the weed, with labor-hour investments in the tens of thousands. Once a weed infestation passes beyond a few acres, the financial commitment to maintaining the productivity of the infested acres is for the long-term. This not only applies to new infestations, but to those where abandonment of past control efforts have resulted in new expansion of existing infestations.

 We are fortunate in Wyoming to have active Weed and Pest Districts that are willing to aid landowners in their weed management efforts. The districts provide cost-sharing opportunities to purchase herbicides for controlling state-listed noxious weeds; further helping to decrease the financial burdens on landowners. So as you make plans for you to-do list this spring and summer, take some time to consider the long-term perspective. An “ounce of prevention” may be far more affordable than the cost of doing nothing.

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