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Bollinger County, Missouri

Information provided for informational purposes only

Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated.

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Pesticide Table for Curtis' Pearly Mussel | About Curtis' Pearly Mussel
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Pesticide Table for Curtis' Pearly Mussel

Active Ingredient Product or Trade Name
Chlorpyrifos on Alfalfa Lorsban
Chlorpyrifos: all other uses except on Alfalfa, or as a Termiticide Lorsban, Dursban, Pageant
Benomyl Benlate, Tersan 1991
Carbaryl Sevin, Sevimol
Diazinon Diazinon, D-z-n
Dicofol Kelthane
Dimethoate Cygon
Disulfoton Di-Syston
Malathion Cythion
Naled Dibrom
Parathion (ethyl) Parathion, Paraspray
Phosmet Imidan
Propiconazole Tilt, Orbit, Banner
Pyrethrins Pyrellin, Pyrenone, Pyrethrum, and others
Trichlorfon Dylox, Proxol

Trade names provided by the University of Missouri Extension Service. For additional information, contact your local University Extension office.

Limitations on Pesticide Use

Product or Trade Name Limitations
Lorsban Do not apply 100 yards from the water's edge (ground application) nor 1/4 mile from the water's edge (aerial application) within the shaded area(s) shown on the map.
All other products listed Do not apply 20 yards from the water's edge (ground application) nor 100 yards from the water's edge (aerial application) within the shaded area(s) shown on the map and 1/2 mile up all streams joining the shaded areas.

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Curtis' pearly mussel [Epioblasma florentina curtisi]

Curtis' pearly mussel is a small bivalve mollusk, one of seven clams in the genus Epioblasma that have been federally listed as endangered. Like most listed clams, it is a member of the family Unionidae, probably the most imperiled family of organisms in the world. This species has an oval shell that is usally less than four centimeters (1.5 in) in length, with males being slightly larger than females. In both sexes, the shell color is yellow-brown to light brown, sometimes with fine, evenly spaced rays over most of its length. This mussel is a long-term breeder in which eggs are fertilized in the fall and the larvae are released in the spring. Although the names are similar, this animal is not closely related to Curtus' mussel, also known as the Black clubshell.

This pearly mussel makes its home in transitional zones between swift-flowing streams headwaters and the more leisurely meandering currents, where it buries itself in the stream floor of sand, gravel, cobbles, and boulders. The mussel is often found in shallow waters at depths of to 76 centimeters (30 in). Like all other mollusks, Curtis' pearly mussel requires clear, usilted water to live in, because silt clogs the siphon which the animal uses to strain water for nutrients.

Curtis' pearly mussel has historically existed in scattered locations throughout river basins in southern Missouri and northern Arkansas. Since the mid-1970's, this species has only been found in southeastern Missouri, in the Castor River, Can Creek, and the Little Black River. From 1981 to 1983, out of 140 probable locations on 26 streams, this mussel was only found at six sites. Despite the fact that this animal has been listed as an endangered species since 1976, it is still extremely uncommon and is thought to remain near extinction.

Much of the former range of the Curtis' pearly mussel has been destroyed by the construction of reservoirs, like Lake Taneycomo and Bull Shoals Reservoir. Impoundements like these flood habitat upstream, and cause silt accumulation downstream by drastically reducing the flow of water. Stream channeling, gravel dredging, and poor land management practices have further exacerbated the problems of siltation and chemical runoff.

The immediate goal of recovery for Curtis' pearly mussel is to thwart extinction and to prevent further loss and damage of to the habitat. There is hope to transfer mussels from a viable population to depleted areas, and to produce juveniles by artificial culture to assist the restocking of suitable habitat within its historic range.

Matthews, J.R. (ed.), The Official World Wildlife Fund Guide to Endangered Species, Beacham Publishing Inc, Washington, DC. Vol. II, pp. 962-963.

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