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Project description

Integrated Use of Prescribed Burning and Clopyralid for Yellow Starthistle Control and Optimum Rangeland Health. (99DS020)
Program UC IPM competitive research grants program
Principal
investigator 		J.M. DiTomaso, Vegetable Crops/Weed Science Program, UC Davis
Host/habitat Rangeland
Pest Yellow Starthistle Centaurea solstitialis
Discipline Weed Science
Review
panel 		Decision Support
 Start year (duration)  1999 (Three Years)
Objectives Determine the effectiveness of prescribed burning, clopyralid treatments, and varying combinations of the two on yellow starthistle control.

Evaluate the effect of varying combinations of burning and clopyralid on rangeland health, as determined by changes in plant diversity and desirable forage quality and quantity.

Assess the impact of a two-year strategy using prescribed burning, clopyralid and combinations of the two methods on the insect biological control populations.

Develop a sustainable integrated management approach that maximizes yellow starthistle control while optimizing rangeland health.

Final report In California and other western states, rangeland productivity and health have been greatly compromised by infestations of noxious thistles, particularly yellow starthistle. Recent research efforts have led to the development of effective control methods for yellow starthistle, particularly prescribed burning and the herbicide clopyralid (Transline). However, repeated use of burning can be impractical and continuous clopyralid treatments can result in suppression of desirable legume species or selection for other undesirable species or herbicide resistance starthistle. Although the solution to these potential problems is the development of effective integrated weed management strategies, no studies have yet focused on the impact of integrating prescribed burning and herbicide on yellow starthistle management and rangeland health and vigor. This project was established in three California counties to address this issue. Current results indicate that both clopyralid a nd prescribed burning can provide near complete control of yellow starthistle. However, when only a single year of control is used, starthistle seedling populations are reduced the following year but vegetative cover is often nearly equal to plots not treated the previous year. This emphasizes the need for a multi-year control strategy. Our results after two years of control indicate that a first-year prescribed burning followed by a second-year clopyralid treatment can provide consistently good control of yellow starthistle, as well as reduced levels of noxious annual grasses, including medusahead and ripgut brome. While two consecutive years of burning can also be effective, some areas to not completely burn in the second year, due to the loss of thatch after the first year burn. Two consecutive years of clopyralid is also an effective approach for control of yellow starthistle, but it can lead to increases in medusahead or ripgut brome. From these findings, we believe be have developed sustainable integrated management approaches that maximizes yellow starthistle control while optimizing rangeland health.

Third-year
progress 		In California and other western states, rangeland productivity and health have been greatly compromised by infestations of noxious thistles, particularly yellow starthistle. Recent research efforts have led to the development of effective control methods for yellow starthistle, particularly prescribed burning and the herbicide clopyralid (Transline). However, repeated use of burning can be impractical, and continuous clopyralid treatments can result in suppression of desirable legume species or selection for other undesirable species or herbicide-resistant starthistle. Although the solution to these potential problems is the development of effective integrated weed management strategies, no studies have yet focused on the impact of integrating prescribed burning and herbicide on yellow starthistle management and rangeland health and vigor. This project was established in three California counties to address this issue. Current results indicate that both clopyralid and prescribed burning can provide near complete control of yellow starthistle. However, when only a single year of control is used, starthistle seedling populations are reduced the following year but vegetative cover is often nearly equal to plots not treated the previous year. This emphasizes the need for a multi-year control strategy. Our results after two years of control indicate that a first-year prescribed burning followed by a second year clopyralid treatment can provide consistently good control of yellow starthistle, as well as reduced levels of noxious annual grasses, including medusahead and ripgut brome. While two consecutive years of burning can also be effective, some areas do not completely burn in the second year, due to the loss of thatch after the first year burn. Two consecutive years of clopyralid is also an effective approach for control of yellow starthistle, but can lead to increases in medusahead or ripgut brome. From these findings, we believe be have developed sustainable integrated management approaches that maximizes yellow starthistle control while optimizing rangeland health.

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