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Domestic Programs Pest Evaluation. Arthur E. Miller, USDA-APHIS-PPQ, AERO, Raleigh, NC. October 6, 2003
Scientific name: Orobanche minor Smith (Orobanchaceae)
Physical description: OM is a fleshy, herbaceous, annual, parasitic plant that grows up to 22 inches tall. The stems are simple and yellow to straw-colored. The leaves are small triangular flaps, alternate to the stem. The roots are short, unbranched, fleshy, and attached to the roots of broadleaf hosts. The self-pollinating flowers are borne in an elongated terminal cluster. Petals are 1/2 inch long and snapdragon-like. Flower coloration is off-white to yellowish, with violet markings. The flowering period is short, starting about one week following emergence. The flowering period is March through May in southern Georgia.
The minute, easily dispersed seeds are prolifically produced and long-lived, some remaining viable for 10 years or more. OM is an obligate parasite. Under proper temperature and moisture conditions, the minute seed (0.5 mm) germinates in the presence of a stimulant from the root of a host plant. Upon host - parasitic contact, the tip of the radicle swells, producing a bulb-like haustorium. The swelling develops into a "spider" stage with reddish rootlets under ground, starting about January in southern Georgia.
Origin and North American Distribution: OM is native to the Middle East and North Africa. It has been introduced into several states. Infestations are currently known to exist in GA, NC, OR, PA, SC, VA, and VT.
Quarantines: OM is a Federal Noxious Weed.
Dispersal: This exotic invasive weed was probably introduced as a vetch seed contaminant and then the seeds were distributed mostly by mowers in southwestern Georgia. It was introduced into South Carolina by a plant collector and with clover seed into North Carolina and Virginia. Other means of dispersal can be soil, equipment, and visitor's shoes.
Control: Property managers and cooperators may use these strategies:
Economic impact: OM has a wide host range. There is concern that this weed may be spread from current infestations to crops such as legume forages and leafy green vegetables. Heavy infestations can cause crop failure. OM has not been observed on any of the major crops in southwestern Georgia, possibly due to asynchrony of life cycles which would differ in other counties and states. Flowers and vegetables in home gardens and ornamental plants are at risk.
Environmental impact: OM has a wide host range and can mutate. Untreated infested turf areas are made ugly with numerous large dead rust-colored plants. It may be parasitic on one or more threatened or endangered plant species.
Benefits of control: Protection of crops, yards, and endangered species in a wide range of climates in the U.S.
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Last updated on Wednesday, November 05, 2003 at 01:31 PM
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