Black Fly Spraying on Greenbrier River

Good going, Marty! I understand that the black fly spray kills the whippoorwills.

Black Fly Control Program

Introduction

The groundwork for the Black Fly Control Program was laid out in the early 1980's, when black flies were declared a public health hazard in southern West Virginia. It was suggested that the black flies could be controlled in the aquatic larval stage by the application of a biological pesticide to several rivers in the area. This suggestion sparked a rage of controversy, pitting the “anti-gnatters” against naturalists and anglers. The anti-gnatter faction was ultimately successful, and the State Legislature provided funding specifically for black fly control. Spraying has been conducted annually since 1986.

Black flies are controlled through the use of a biological agent called Bacillus thuringiensis var. israelensis, or Bti. Bti is a bacterium that disrupts the digestive system, resulting in rapid mortality. This strain of bacteria is only potent on insects having an alkaline gut and, therefore, has little effect on non-target species. Laboratory studies have not demonstrated any adverse effects on mammals or fish at the recommended dosage rate.

Responsibilities

The goal of the Black Fly Program Coordinator is to maintain good control of the black fly population without adversely affecting other members of the aquatic community. Attention must be paid to details, as there is little room for in timing of treatments if adequate black-fly control is to be achieved. The Coordinator must be able to identify aquatic insect groups in the field. College-level studies in aquatic entomology, limnology, or similar courses are required. The Coordinator must be able to recognize the black fly instars* with confidence, as good larval control is achieved by applying treatment to the proper instar.

*An instar is the life stage between two successive molts.

Treatment Area

Three river systems are treated:

1) Bluestone: 13 sites—lower 12 miles (1 section)

2) Greenbrier: 112 sites (6 sections)
a. Lower Greenbrier: 17 sites—from the mouth to Talcott
b. Upper Greenbrier: 13 sites—from Talcott to Half Way (approximately one mile above
Alderson)
c. Lower Greenbrier Extension: 13 sites—from Half Way to Ronceverte
d. Upper Greenbrier Extension: 17 sites—from Ronceverte to Anthony
e. Lower New Greenbrier: 20 sites—from Anthony to Spice Run
f. Middle/Upper New Greenbrier: 32 sites—from Spice Run to Clover Lick

3) New: 18 sites (2 sections)
a. Upper New: 8 sites—from Wylie Island (near Virginia line) to Bluestone lake
b. Lower New: 10 sites—from the Bluestone Dam to Sandstone

The application sites are permanent transects located at black-fly-producing riffles. These transects are indicated on topographical maps labeled according to the river sections listed above.

If new maps are prepared, the location of all utility lines crossing the river must be indicated. Utility lines are indicated by red X's or red lines across the stream. These notations are crucial for the safety of the pilot.

Determination of Treatment Date

Larval development is dependent on water temperature: the warmer the water, the more rapid the development. When water temperatures reach 50° F, larval growth occurs fairly quickly. In general, each instar lasts about 2 days until water temperatures reach the 60° mark, and 1 to 1.5 days when temperatures are in the 70s and 80s. A rough estimate of the development schedule follows.

If the water temperature is: Then the black fly development time is:
40 – 49  F 2.5 days / instar
50 – 59  F 2 - 2.5 days / instar
60 – 69  F 2 - 1.5 days / instar
70 – 79  F 1.5 days / instar
80 – 89  F 1 - 1.5 days / instar

Determination of Flows

It is imperative to have a calculator and a cell phone on hand (see below). The fist step is to obtain the flows for the respective sections of rivers from the following gauges:

Upper New River (8 sites), Glen Lyn, Va.: (540) 726-7369

New River below dam (2 sites*) and Lower New River (8 sites, Hinton gauge), Army Corps of Engineers, Bluestone Dam: 466-1234

Bluestone River (13 sites), Pipestem: 466-1626

Lower Greenbrier River (17 sites), Hilldale: 466-0913

**Upper Greenbrier River (13 sites), Lower Greenbrier Extension (13 sites), and Upper Greenbrier Extension (17 sites), Alderson: 445-3105

**Upper, Middle, and Lower New Greenbrier River (52 sites), Buckeye: access from USGS website

• One is just below the dam and one just above the mouth of the Greenbrier River.

** For greater accuracy, a sliding scale is advised for the Greenbrier River between the Buckeye and Alderson gages, as these readings can be quite different. It is up to the Coordinator to determine and apply such a scale.

Pilot and Ground Crew Duties

The Bti must be applied in such a manner to assure that the treatment site receives a dosage of 11 ppm for a duration of approximately one minute. The pilot may sometimes need to make two passes to apply all the product specified for a particular site. Riffles need to be treated from bank to bank to ensure good control.

During high flows, the line of flight across the riffle can be adjusted so that a faster flowing area will be treated further upstream than a slower flowing area. This adjustment allows the band to collapse when it reaches the riffle and gives an even treatment for the entire cross-section.

At the dam, the pilot must be especially careful to avoid anglers. Whenever possible, the spray should be applied directly above the spillway. Often, however, anglers make this impossible and the pilot must move downstream, applying the product as close to the spillway as possible.

The total amount of Bti to be used is determined prior to loading the truck that follows the helicopter. This information is used by the coordinator and the pilot to determine how much Bti will be flown from each loading zone. The coordinator supervises the loading of the truck to make sure enough Bti is loaded.

Bacillus thuringiensis subsp. israelensis (Bti) is a naturally occurring soil bacteria used as a microbial insecticide to control the spread of vector-borne diseases, protect public health, and manage insect pest species. Bti was first discovered in a stagnant pond in the Negev Desert of northcentral Israel in 1976 (Margalit and Dean 1985). Initial testing of Bti revealed acute toxicity to mosquitoes (Goldberg and Margalit 1977) and black flies (Undeen and Nagel 1978) that can carry and transmit diseases. Further research demonstrated that Bti is nontoxic to humans, mammals, birds, beneficial insects, fish, plants, and most aquatic organisms (EPA 1998 Bti EG2215 Factsheet). Bti was first registered by the U.S. EPA as an insecticide in 1983. Species-specific properties, safety to nontarget organisms, rapid breakdown, and reduced insect resistance make Bti an ideal pesticide (de Barjac and Sutherland 1990), with greatly reduced environmental impacts in comparison to man-made chemical insecticides.
Trade Names: Vectobac, Teknar, Aquabac, Bactimos, LarvX, etc. (26 Bti products in U.S.)
Application Procedures and Mode of Action on Target Organisms
Bti is applied by aerial spraying or backpack spraying at a safe rate specified by the United States Environmental Protection Agency. Black flies and mosquitoes must actively ingest Bti in order for the material to be effective. Bti is a gram positive, aerobic, spore-forming bacterium that produces protoxins in the form of parasporal protein crystals. In the alkaline digestive tract of black flies and mosquitoes, the protoxins become activated into highly toxic delta-endotoxins. The endotoxins cause a rapid breakdown in the lining of the midgut and necrosis of skeletal muscles, resulting in paralysis and mortality of target insect pests. Bti is nontoxic to most nontarget organisms due to their acidic digestive systems and lack of suitable tissue receptor sites.
Impacts on Nontarget Organisms
Most nontarget scientific studies conducted since the discovery of Bti in 1976 have concluded that the material is harmless to most nontarget organisms when applied at recommended label rates. Research has demonstrated that Bti is nontoxic to humans, mammals, birds, fish (trout and bluegill), and most invertebrates when properly applied (EPA 1998 Reregistration Eligibility Decision). Moderate toxicity in Daphnia and honeybees has been attributed to inert formulation ingredients rather than active ingredients. In fish studies, juvenile trout species and fathead minnows were unaffected by normal dosages, and were impacted only at very high Bti concentrations. Studies have demonstrated limited impacts to several aquatic Diptera families (Chironomidae and Blepharoceridae midges) when exposed to Bti treatments in mosquito and black fly habitats (Laird et al. 1990). Sensitive mayflies, stoneflies, caddisflies, crustaceans, snails, and bivalves, important members of the aquatic food chain in freshwater fisheries, are not significantly affected by Bti applications (Jackson et al. 2002). Data from a large number of studies indicate that Bti can be used in a carefully managed treatment program to selectively control insect pest and vector species with minimal adverse environmental impacts.
Further Reading
• Undeen, A.H. and W.L. Nagel. 1978. The effect of Bacillus thuringiensis ONR-60A strain (Goldberg) on Simulium larvae in the laboratory. Mosquito News 38: 524-527.
• de Barjac H. and D.J. Sutherland (eds.). 1990. Bacterial control of mosquitoes and black flies: Biochemistry, genetics and applications of Bacillus thuringiensis

In my experience sometimes what is billed as a need is really "make work"

I notice in reading the "not to worry" literature which was sent by the WV Dept of Agriculture (posted above) several matters which cause me to ask some questions. 1. It says " most" studies show it is non toxic; what do the other studies show? 2.It is toxic to honey bees; when was the last time you saw a honey bee? Bees have dwindled to next to nothing in my experience in the last thirty years. I use to raise bees. Any adverse impact on this important resource to agricultre should be avoided. 3. All safety also depends upon proper "application"; that is mixing right amounts and spraying right amounts. Just because something is "naturally occurring" does not mean it can cause no harm. All viruses for example are naturally occurring. Multiflora rose is a naturally occurring plant unfortunately. When people "tinker" with the ecosystem to adjust it there are often unforeseen negative consequences.