Cultural Control of yellow starthistle - Centaurea solstitialis
Goats: Goats are the most popular method used for the control of yellow starthistle (1). While cattle and sheep won't eat the weed in its "spiny" stage, goats will. Yellow starthistle also provides food that is high in protein for goats (3). They get approximately 8 to 14% protein (1). The crude protein concentration is also a good number for them. It ranges anywhere from 11 to 28% (2).
Tillage: Tilling is often used to damage root systems. In young plants, tilling helps separate the shoots. It also damages the roots in most large plants. Tilling must only be done only when the surface of the soil is dry. This prevents the re-growth of the weed. Thus, the best time to do this is in the early summer months. However, you can repeat the cultivation process in the same season after rainfall stimulates more germination (1).
Tilling is the most effective on roadsides. It is usually not used in wildlands or rangelands because it can damage species of plants that many people do want (2). It is also bad because it increases erosion (1). The chances for a worse infestation is also more likely in wildlands and rangelands (2).
Hand Pulling: The most effective way to remove yellow starthistle is in small or scattered patches throughout a grassland system (2). To prevent the plant from growing back, you must make sure that you remove it correctly (1). There are several steps you must take to kill and prevent yellow starthistle from growing back. The first thing you should do is look to see what stage the plant's growth is in. The best time for removal is after it has bolted, but before the weed has gotten its first flowers. When pulling the weed you must learn to remove all stem material above the ground. Even leaving a two inch piece of stem above the ground could allow the weed to grow back. It is also important to make sure the soil around the weed is not disturbed much. Too much disturbance could allow new seeds to re-establish themselves (1).
Areas where there is heavy vegetation are usually the easiest to kill using this method. Yellow starthistle usually develops a long, thin stem and has only a few basal leaves. These types of plants generally have no leaves attached to their base, and thus rarely are able to grow back (1).
Controlled Burning: This method is often used to control yellow starthistle (1). In order to have success, you need to burn at the right time of year. The best time is is the mid-summer months (late June to early July.) During these months, burning will be most effective because it is in the early flowering stage (2). A downfall to burning is that it has only minimum impact on the seeds. The surface of the soil only reaches a temperature of 200 degrees Celsius. Therefore the seeds on the surface of the soil cannot be damaged. The seeds may also eventually germinate (1). Burning also requires several years to sufficiently control yellow starthistle (2). In the first growing season, the diversity will increase (1). However, after approximately three years of burning, 99% of all the seeds in the seedbank are reduced. Vegetation control will also be 90% or higher (2).
Watering: No information available.
Fertilizing: No information available.
Grazing Methods: Sheep, goats, and cattle all eat yellow starthistle (1). Sheep and cattle will only eat it before the spines on the weed form, but goats will eat it no matter what growth stage it is in (2). Intensive grazing is an effective way to control yellow starthistle (3). This is using a large number of animals to try to control the weed (1). The best time for intensive grazing is in May and June. This process will reduce plant and canopy size, as well as seed production (2). However, overgrazing can backfire your efforts to control the plant (3). A new invasion of the weed often occurs if you overgraze (1). The spines of the plant are poisonous to some grazing animals. (3)
1.) DiTomaso, Joseph M., Yellow Starthistle Information, Management. [Online] Available: http://wric.ucdavis.edu/yst/manage/management.html, January 8, 2001.
2.) DiTomaso, Joseph M., et. al., Yellow Starthistle, Home & Landscape. [Online] Available: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7402.html, January 8, 2001.
3.) Harper, John, et. al., Yellow Starthistle. [Online] Available: http://danr.ucop.edu/uccelr/range01.htm, Last modified April 4, 1999.
By Kristen Leverton and Justin Stratton 01/17/02
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