malathion

[dr-solo]

somehow I deleted the message I wanted to respond to. Malathion is used to control mosquitoes. The regional department of natural resources hydrologist (who I had worked with on other issues to the public health) asked for my recommendation for controlling mosquitoes due to the spread of West Nile Virus. I told her to go the NON CHEMICAL route and use Bt israeli since a microbe will mutate close to the rate the mosquitoes will mutate to resistance. I am not an advocate of any kind of wide spread pesticide use. I actively advocate and lecture against most GMO specifically against Bt corn and herbicide resistance in crops. I DO advocate integrated pest management. In my own garden I use the least noxious chemicals, in the least amount, limited only to the affected plants, and only when absolutely necessary. Pure Malathion is one of the least noxious chemicals when used correctly on land. Contaminants and carriers are credited with much of the toxicity. Ingrid

* Malathion is rapidly and effectively absorbed by practically all routes including the gastrointestinal tract, skin, mucous membranes, and lungs. Malathion undergoes similar detoxification mechanisms to other organophosphates, but it can also be rendered nontoxic via another simple mechanism, splitting of either of the carboxy ester linkages. Animal studies indicate it is very rapidly eliminated though urine, feces and expired air with a reported half-life of approximately 8 hours in rats and approximately 2 days in cows [2]. Autopsy samples from one individual who had ingested large amounts of malathion showed a substantial portion in the stomach and intestines, a small amount in fat tissue, and no detectable levels in the liver. Malathion requires conversion to malaoxon to become an active anticholinesterase agent. Most of the occupational evidence indicates a low chronic toxicity for malathion. One important exception to this was traced to impurities in the formulation of the pesticide [2].

Ecological Effects:

• Effects on birds: Malathion is moderately toxic to birds. The reported acute oral LD50 values are: in mallards, 1485 mg/kg; in pheasants, 167 mg/kg; in blackbirds and starlings, over 100 mg/kg; and in chickens, 525 mg/kg [2,6]. The reported 5- to

8-day dietary LC50 is over 3000 ppm in Japanese quail, mallard, and northern bobwhite, and is 2639 ppm in ring-neck pheasants [6]. Furthermore, 90% of the dose to birds was metabolized and excreted in 24 hours via urine [79]. * Effects on aquatic organisms: Malathion has a wide range of toxicities in fish, extending from very highly toxic in the walleye (96-hour LC50 of 0.06 mg/L) to highly toxic in brown trout (0.1 mg/L) and the cutthroat trout (0.28 mg/L), moderately toxic in fathead minnows (8.6 mg/L) and slightly toxic in goldfish (10.7 mg/L) [13,8,16]. Various aquatic invertebrates are extremely sensitive, with EC50 values from 1 ug/L to 1 mg/L [28]. Malathion is highly toxic to aquatic invertebrates and to the aquatic stages of amphibians. Because of its very short half-life, malathion is not expected to bioconcentrate in aquatic organisms. However, brown shrimp showed an average concentration of 869 and 959 times the ambient water concentration in two separate samples [12]. * Effects on other organisms: The compound is highly toxic to honeybees [13].

Environmental Fate:

• Breakdown in soil and groundwater: Malathion is of low persistence in soil with reported field half-lives of 1 to 25 days [19]. Degradation in soil is rapid and related to the degree of soil binding [12]. Breakdown occurs by a combination of biological degradation and nonbiological reaction with water [12]. If released to the atmosphere, malathion will break down rapidly in sunlight, with a reported half-life in air of about 1.5 days [12]. It is moderately bound to soils, and is soluble in water, so it may pose a risk of groundwater or surface water contamination in situations which may be less conducive to breakdown. The compound was detected in 12 of 3252 different groundwater sources in two different states, and in small concentrations in several wells in California, with a highest concentration of

6.17 ug/L [33]. * Breakdown in water: In raw river water, the half-life is less than 1 week, whereas malathion remained stable in distilled water for 3 weeks [12]. Applied at 1 to 6 lb/acre in log ponds for mosquito control, it was effective for 2.5 to 6 weeks [12]. In sterile seawater, the degradation increases with increased salinity. The breakdown products in water are mono- and dicarboxylic acids [12]. * Breakdown in vegetation: Residues were found mainly associated with areas of high lipid content in the plant. Increased moisture content increased degradation [33]. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List Manager: Puregold Goldfish List at up: the problem, dont waste energy finding who's to blame ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I receive no compensation for running the Puregold list or Puregold website. I do not run nor receive any money from the ads at the old Puregold site. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Zone 5 next to Lake Michigan

[Carl 1 Lucky Texan]

anticholinesterase

excellent info - thanx

Carl

[limey]

I understand malathion kills honey bees? (which is a bad thing.) The county used to spray for mosquitoes several times a summer but were using malathion. I haven't seen a honey bee in a long time - is that the cause?

[George Shirley]

There's been a lot in the ag news about some sort of mite that's been killing off whole hives of European honey bees, the kind we've had in the USA for over 200 years. I don't think anyone still uses malathion to kill mosquitoes nowadays.

George

[limey]

No, the county stopped using malathion a number of years ago. I don't know what they use now. I hadn't heard about the mites.

Dora

[dr-solo]

pesticides of all kinds can kill honey bees. but a greedy practice has decimated the bee population. normally, bees put up enough honeycomb to last all winter. too many bee keepers take all the honey comb, let the bees die and ordered new bees in the spring. the result was spreading disease to all these new colonies which were shipped north and infected wild colonies and those bee keepers kept their bees over winter.

"Varroa destructor and Varroa jacobsoni are parasitic mites that feed off the bodily fluids of adult, pupal and larval bees. Varroa mites can be seen with the naked eye as a small red or brown spot on the bee's thorax. Varroa is a carrier for a virus that is particularly damaging to the bees. Bees that are infected with this virus during their development will often have a visible "K-wing" deformity.

Varroa has led to the virtual elimination of feral bee colonies in many areas and is a major problem for kept bees in apiaries. Some feral populations are now recovering ? it appears that they have been naturally selected for varroa resistance (these so-called feral populations may be africanized bees).

Varroa was first discovered in Southeast Asia in about 1904, but has now spread virtually worldwide. Varroa was discovered in the United States in 1987, in New Zealand in 2000.

Varroa is generally not a problem for a hive that is growing strongly. When the hive population growth reduced in preparation for winter or due to poor late summer forage the mite population growth can overtake that of the bees and can then destroy the hive. Often a colony will simply abscond (leave as in a swarm, but leaving no population behind) under such conditions. "

our typical h>limey wrote:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List Manager: Puregold Goldfish List at

up: the problem, dont waste energy finding who's to blame ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I receive no compensation for running the Puregold list or Puregold website. I do not run nor receive any money from the ads at the old Puregold site. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Zone 5 next to Lake Michigan