Tanglehead Invasion!

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At the end of 2020, CKWRI will have completed a four-year study on the use of prescribed fire and cattle grazing to manage the invasive tanglehead grass on a private ranch in South Texas. This research provides reliable information that may be applied by ranchers in the region. Follow link in bio to read full article in the most recent issues of Caesar Kleberg Tracks.  

Posted to CKWRI's Instagram page on August 17, 2020. (www.instagram.com/ckwri_official/)

Challenges and Strategies to Manage Invasion of Tanglehead: A Threat for Wildlife Habitat Integrity

by J. Alfonso Ortega-S.

Several exotic invasive grasses such as buffelgrass, old world bluestems, and guinea grass have been a concern for the conservation of wildlife habitat. These exotic grasses were introduced to the U.S. to increase the production of forage for cattle. Certainly, at the time these decisions were made, the value of wildlife species was not as important as now and it seemed like the right decision. One of the characteristics of these exotic grasses is that they are all very palatable for cattle. It is different in the case of tanglehead, which is a native grass that provides good forage for cattle, and naturally reduces/declines through heavy grazing. However, it has been invading native rangelands in the sand sheet region of South Texas, a prime area for white-tailed deer and bobwhite hunting. Thousands of acres of monocultures of Tanglehead have replaced critical native wildlife habitat.

In most of the ecological sites of the sand sheet region, tanglehead should be about 5% of the native vegetation cover. Small groups of 2 or 3 plants, spaced throughout the landscape, provides good for nesting cover for bobwhites or wild turkeys. However, tanglehead has gone from scattered clumps to large monoculture stands in a brief time. Tanglehead in Kleberg and Jim Hogg counties increased in percentage from 1.4% in 1999, to 2.7% in 2002, to 8.1% in 2009, and then to 17.8% in 2014, which means the plant increased coverage over 10 times in 15 years. This increase in tanglehead likely occurred because of peak rainfall shifting from spring to summer and a reduction in cattle grazing on ranches where the main focus was habitat management for wildlife. What should be done if a landowner notices that tanglehead becoming more abundant? Monitoring how tanglehead cover is changing over time is crucial for taking action. When spots of the plant start looking excessive, the use of glyphosate at 24 or 36 oz/ac can be used to kill individual spots of the invasive plant.

The lack of action at the initial stages of tanglehead invasion sets the stage for a much bigger problem. Once tanglehead becomes a monoculture the question becomes: is there any treatment to manage it and return the habitat to the original state? We have been successful managing monocultures of tanglehead with prescribed fire and cattle grazing. The capacity of tanglehead to accumulate forage (about 5000 lb/ac) is an advantage to use practices like prescribed fire. In addition to the reduction in tanglehead biomass and the mortality of some plants, the new growth of tanglehead increases the palatability of the forage for cattle and the nutritive value of the grass, which in turn reduces the presence of tanglehead through grazing. According to our research, mature tanglehead can be 4% crude protein compared to 16%, 34 days after fire. We found that burning patches of about 10% of the size of the pasture, with a stocking rate of cattle of about 20 acres per animal unit, effectively reduced the tanglehead population and increased native plant species richness. Prescribed fire increased utilization of tanglehead to 52% in the burned areas compared to 6% in the non-burned areas and cattle used the burned areas 4.5 times more than the non-burned areas. Plant species richness increased 330% in the burned plots compared to before the burn. How often do we need to apply the prescribed burning and the cattle grazing to maintain the invasion of tanglehead to acceptable levels? The differences from burning and grazing may last for 3 years, which is an acceptable treatment life. When is the best time to burn tanglehead to manage the invasion? Late fall or early winter burns have shown to have the best results. Considering that tanglehead is a warm season grass, burning right before or at the beginning of the dormancy will weaken the plants, decreasing the density and providing opportunities for native plants to germinate and establish. What if is not possible to conduct a prescribed burn? Poor burning conditions may occur in South Texas often. Anecdotal observations indicate that mowing patches of tanglehead increase the palatability and nutritive value of the grass, attracting cattle to the mowed areas which would result in a similar effect as using prescribed fire.

There are still many questions to answer about tanglehead management. Our research program is generating practical knowledge to deal with the problem. At the end of 2020, we will have completed a four-year study on the use of prescribed fire and cattle grazing to manage tanglehead invasion on a private ranch in South Texas. The research we are conducting with tanglehead will provide more reliable information that may be applied by ranchers in the region.

Read the entire issue of Caesar Kleberg Tracks Spring 2020 here