Mosquito larvicide

Methoprene and hydroprene are first-generation juvenoids that iacorporate minor stmctural optimisation of neotenin to increase persistence. Methoprene, 1-isopropyl (E,E)-ll-methoxy-3,7,ll-tnmethyl dodecadi-2,4-enoate (129) (bp 100 C/6.7 Pa, vp 3.5 mPa at 25°C), is soluble ia water to 1.4 mg/L. The rat oral LD q is >34,000 mg/kg. Methoprene has been used as a mosquito larvicide, ia baits for ant control, and as a catde feed-through treatment for horn fly control. Hydroprene, methyl (H,H)-3,7,ll-trimethyl-dodecadi-2,4-enoate (130) (bp 174°C at 2.5 kPa, vp 2.5 mPa at 25°C), is soluble ia water to 0.54 mg/L. The rat oral LD q is >34,000 mg/kg. Hydroprene is especially effective against aphids and cockroaches. 

Granulars are pelleted mixtures of toxicant, usually at 2.5 ndash 10%, and a dust carrier, eg, absorptive clay, bentonite, or diatomaceous earth, and commonly are 250 ndash 590 ]lni in particle size. They are prepared by impregnation of the carrier with a solution or slurry of the toxicant and are used principally for mosquito larviciding and soil appHcations. 

The compound MON-0585 is a nontoxic, biodegradable larvicide that is highly selective against mosquito larvae. Synthesize MON-0585 using either benzene or phenol as a source of the aromatic rings. 

The testing techniques used with mosquito larvae, usually the addition of calculated quantities of the larvicide previously dissolved in a water-miscible solvent, are somewhat more comparable. However, the results here are conflicting. The A. qvxjdnmaculatus larvae are killed within 24 hours by either DDT or DFDT at concentrations somewhat... 

Monofluoroacetic acid offers little promise as a mosquito larvicide, but 2-ethylhexyl monofluoroacetate is a very powerful aphicide. The high toxicity of the fluorinated lower aliphatic acids and their esters to vertebrates probably precludes their use as insecticides except under highly controlled conditions. The toxicity of the fluorinated acids to the vertebrates is attributed to their interference with an enzyme system, but the possibility of finding one with a high specificity for insects is not excluded. 

Individual applications of 0.014-0.019 kg/ha, emulsifiable concentrate, oil diluent, 3 applications at 5-week intervals 0.02 kg/ha, granularformulation, single application 0.025 kg/ha, single application 0.028 kg/ha (0.025 Ibs/acre), single aerial application, mosquito larvicide granules Individual applications of 0.028 kg/ha, 4 applications at 2-week intervals... 

Moore, J.B. and S.G. Breeland. 1967. Field evaluation of two mosquito larvicides, Abate and Dursban against Anopheles quadrimaculatus and associated Culex species. Mosquito News 27 105-111. 

Schaefer, C.H. and E.F. Dupras, Jr. 1969. The effects of water quality, temperature and light on the stability of organophosphorus larvicide used for mosquito control. Proc. Pap. Annu. Conf. Calif. Mosq. Control Assoc. 37 67-75. 

U.S. Fish and Wildlife Service (USFWS). 1968. Field Appraisal of Tests to Control Salt Marsh Mosquito with Dursban Applied as a Larvicide And Adulticide in Florida. U.S. Fish Wildl. Serv. Spec. Rep., Pesticide Field Appraisal Program, Atlanta, Georgia. Mimeo. 25 pp. 

Mulla, M.S., H. A. Darwazeh, and M.S. Dhillon. 1980. New pyrethroids as mosquito larvicides and their effects on nontarget organisms. Mosquito News 40 6-12. 

Methoprene has been fully registered since 1975 for commercial usage as a mosquito larvicide and for control of horn flies via feed-through application to cattle. In addition, methoprene is registered in Japan for administration to silkworms to enhance silk production. As the only IGR currently (July, 1978) registered, it follows that the environmental fate of methoprene has been investigated in detail. 

In summary, photodecomposition of methoprene is facile and leads to a multiplicity of products. The lower photostability in sunlight of methoprene compared to epifenonane has been mentioned previously. Because of its photochemical lability and its ready microbial degradation (see below), methoprene is microencapsulated for aquatic use as a mosquito larvicide. 

Figure 1. Relationship between the mosquito larvicidal toxicity (log LC50) of the thiocarbamate derivatives of carbofuran, propoxur and m-isopropylphenyl methylcarbamate (MIP) and logarithm of the octanol/water partition coefficient (log P).

Previous work with extracts of various plant species containing isobutylamide compounds indicated the larvicidal effects of the extracts against several species of mosquito.Other work has shown the molluscicidal activity of some unsaturated aliphatic isobutylamides against Physa occidentalis. 

Zhu J, Zeng XY, Liu T, Qian K, Han Y, Xue S, Tucker B, Schultz G, Coats J, Rotvley W, Zhang A, Adult repellency and larvicidal activity of five plant essential oils against moscgmocs, J Amer Mosquito Control Assoc 22-3 b— b22, 2006. 

Petroleum oils in mosquito control ore discussed from the pioneering experiments to their present-day status. Used alone or as carrying agents for other materials, such as DDT, petroleum oils have proved almost indispensable as larvicides and adulticides in the control of mosquitoes. Outdoor applications, from the ground and from the air, are described as well as indoor space and residual sprays. Standard specifications are urged for a petroleum oil that may be used as a mosquito larvicide. 

Howard s ( d) pioneer experiment on the use of kerosene against mosquito larvae, published in 1892, is well known. It is not so well known, however, that in 1867 he observed how illuminating oil killed mosquito larvae when he accidentally spilled some oil while filling a lantern over a horse trough infested with wrigglers. When called upon to devise a means for killing mosquitoes in later years, he remembered this incident on his father s farm in his early boyhood and so performed experiments that led to the universal use of petroleum oils as mosquito larvicides. 

Oil as Toxicant. Crude petroleum and several petroleum products, used alone or with other materials acting as contact poisons, make effective mosquito larvicides. 

While carrying out tests on mosquito larvicides in Florida, Burrell et al, (8) found that oils were not spreading properly on most of the waters in September, and that some type of inhibiting biological film had formed on these breeding areas after control operations had been initiated early in the summer. They compared the spreading properties of Triton X-100 and of a Span 20-Tween 20 mixture (equal parts when used in No. 2 fuel oil) the results are given in Table II. 

Unfortunately, the superintendents of many mosquito abatement districts know too little about the resistance of the surface films existing on their mosquito-breeding areas. Here is an excellent opportunity for a cooperative study between the oil company furnishing the larvicide and the mosquito control agency using it. 

Specifications. The New Jersey Agricultural Experiment Station has prepared specifications for mosquito larvicides as a result of experiments conducted by Gins-burg (19). 

The Tennessee Valley Authority (3 ) gives the following specifications for black oil as a mosquito larvicide ... 

There is need for experiments on the effect of various solvents in formulation of mosquito larvicides and adulticides containing chlorinated hydrocarbon insecticides. 

The miscibility and specific gravity of mosquito larvicides may greatly modify their usefulness. Likewise, information on the viscosity of petroleum oils in relation to their effectiveness as mosquito larvicides and adulticides may increase their value. There is much that we do not know about them and their place in mosquito control. 

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