AgWatch

April Is Typically The Time To Control Musk Thistle

SPRINGFIELD, MO.
   April is the best time to control musk thistle since it is typically still in the rosette stage according to John Hobbs, an agronomy specialist with University of Missouri Extension.
   “The musk thistle is most susceptible to herbicide in its young vegetative stage. The key to thistle control is to prevent plants from going to seed,” said Hobbs.
   There are several control methods proven to be successful in controlling thistle. However, none of these methods will provide complete control with only one application.
   According to Hobbs, musk thistle is readily controlled by timely tillage.
   “The most common method of control is spraying with herbicides. The stage of growth is very critical. Apply all chemicals during the rosette stage for the best results,” said Hobbs.
   Spring application should be done before stem elongation and while daytime temperatures are at least 60 to 65 degrees Fahrenheit (typically in late March to late April).
    Fall application (typically in September to November) should be done to seedlings and first rosettes as they are actively growing.
   During the summer months, after the plant has flowered, removing the seed head and pulling or hoeing the entire plant is the only option left.
   “Mowing, by itself, does not provide effective control. Buds and flowers will soon redevelop and the infestation will become greater,” said Hobbs.
    The following are recommended chemical controls in pastures for thistles: Herbicide 2,4-D amine, 1 - 2 quarters per acre, 3 - 6 Tb per gallon; herbicide 2, 4-D Easter, 2 quarters per acre, 3 Tb per gallon; herbicide Grazon, 1 quarters per acre, 3 Tb per gallon. Δ
Musk thistle has also been called nodding thistle because of its large solitary flower heads that often bend over. Seedling plants have waxy, pale green leaves with shallowly lobed margins containing irregular prickles. During the second season of growth, leaves become deeply cut and their margins are tipped with stiff, sharp spines. Leaf tissue is glossy and the only hair on the foliage may be found on the main veins. The flower head has numerous spine-tipped bracts, is usually pink to purple in color (occasionally white) and grows up to 2 inches in diameter. In Missouri, musk thistle is most problematic in pastures and along roadsides. It is regulated by Missouri noxious weed laws.
Photo courtesy University of Missouri Extension

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