Methoprene, effectiveness

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. 

Madder, D.J. and W.L. Lockhart. 1978. A preliminary study of the effects of diflubenzuron and methoprene on rainbow trout (Salmo gairdneri Richardson). Bull. Environ. Contam. Toxicol. 20 66-70. 

Ankley, G.T., J.E. Tietge, D.L. DeFoe, K.M. Jensen, G.W. Holcombe, E.L. Durhan, and S.A. Diamond. 1998. Effects of ultraviolet light and methoprene on survival and development of Rana pipiens. Environ. Toxicol. Chem. 17 2530-2542. 

Retinoic Acid Receptor. Most of the biological effects of retinoids are mediated through the retinoic acid receptor (RAR) and the retinoid X receptor (RXR). Both all-/ran.s-retinoic acid and 9-d.v-rctinoic acid serve as agonists of RAR, while only 9-d.v-rctinoic acid functions as an agonist of RXR. The functional RAR exists as a heterodimer with RXR, while functional RXR exists as a homodimer. Methoprene is a juvenile hormone III analogue that mimics the activity of this insect hormone. 

Methoprene and fenoxycarb mimic the action of insect juvenile hormone in molting and reproduction, and have low toxicity to mammals. Exposure at molting produces deformed insects having mixed larval/pupal or larval/adult morphologies, and they disrupt reproductive physiology in adults to effectively serve as a method of birth control. 

At this point the history of the concept of hormonal control of insects should be recalled, since the major reasons for the selection of JH as a rational lead for pesticide design were the beliefs that JH occurred only in insects and not in other animals. The implication was that JH would therefore be selectively active in insects with no significant effects on other forms of life. In the cases of JH analogs of the farnesane skeleton, extensive studies of comparative toxicology have largely verified these beliefs. Toxicological results have been reviewed in detail (20 ) and a comprehensive study of the environmental fate and metabolism of methoprene has been completed (2 1). ... 

At least two events were responsible for a change in this attitude and provided the incentive to select and develop an effective juvenoid for cockroach control a) the success achieved with the juvenoid methoprene in the control of breeding flea populations in household carpets and upholstery (17, 18) b)... 

Results. Technical hydroprene as well as the RF formulation were both fully effective in inhibiting reproduction and producing a high or complete Incidence of morphogenetic abnormalities at a rate as low as 1 ug/cnr (Table II). Technical methoprene required 1000 Ug/cm, and thus was 100 to 1000 times less effective than hydroprene technical. Methoprene RF was at least 10 times more effective than technical methoprene and therefore approximately 100 times less effective than hydroprene in a similar formulation. High concentrations of the inerts of RF formulations appeared to be toxic by themselves, at least when formulated with dienoates. A formulation blank was not included because the blank RF formulation was found to be physically not comparable (only a formulation with an inert look alike dienoate would have made a relevant comparison). 

Discussion. The increase in activity for the RF formulations of methoprene and the retention of activity for hydroprene was a surprise since formulations with a long residual generally tend to decrease acute activity. However, the increased stability, the decrease in volatility and the intense contact with a dust formulation by grooming cockroaches may have contributed to this result. It also appeared that methoprene (RF 10%) at 100 ug/cin was an effective control dose. 

Early reports suggested that methoprene exerted its toxic effect not as a JH mimic but as an inhibitor of JH degradation, resulting in the accumulation of endogenous JH (Slade and Wilkinson, 1973). More recent studies involving insect tissue culture or cell culture have eliminated this hypothesis. 

Figure 5. Effects of JHA ( methoprene) and Bld-HrTH on the capacity for soluble protein synthesis by fat body from decapitated, female adult B, discoidalis.

Methoprene is a long chain hydrocarbon ester active as an insect growth regulator. It is effective against several insect species. Formulations include slow-release briquets, sprays, foggers, and baits. 

Although juvenile hormone itself is too unstable in light and too expensive to synthesize for use in controlling insect populations, related compounds, called juvenile hormone mimics, have been used effectively. The best known example is called methoprene, sold under such trade... 

No clinical effects or overt signs of toxicity are known to have occurred in humans due to methoprene exposure. Because of its mechanism of action, methoprene has high selectivity for insects and no acute toxicity is expected in humans even after ingestion of large doses. 

Methoprene is practically nontoxic to birds with an acute oral LD50 of >2000 mg kg in mallard ducks and an 8 day dietary LC50 >10 000 ppm in bobwhite quail. In avian reproduction studies, methoprene had no effects on reproductive parameters at dietary concentrations of 30 and 3 ppm in quail and mallards, respectively. 

Pyrethrins and PBO in combination with methoprene showed lOO ft control of feline fleas 35 days after treatment, with a satisfactory residual effect up to 2 months (Donahue, 1992). In addition (here is evidence that PBO is an 1GR in its own right. In a laboratory study PBO added lo three major cotton plant al 1 Biochemical s in the diet of tobacco bud worm larvae significantly decreased the growth rate of the 5-day-old larvae, and was found to be toxic to the 1- and 3-day-old larvae (Hey din t i u/.. 1988). 

Besides aroma chemicals, we are supplying key intermediates for the synthetic insect growth regulators, (S)-3,7-dimethyl-l-octanal 18a and (S)-7-methoxy-citronellal 18b, on 100 ton scales each. Hydropren 19a is effective for mosquitoes and Methopren 19b is used for controlling cockroach, where only (S)-forms are active (Fig.3). 

Kawada, H. and Hirano, M. (1996) Insecticidal effects of the insect growth regulators methoprene and pyriproxyfen on the cat flea (Siphonaptera Pulicidae). Journal of... 

Fleas on animals can be controlled by methoprene (11.45), a juvenile hormone mimic that prevents the conversion of larvae into pupae.177 Another chemical, lufenuron (11.46) is given to the animal orally. Any flea that bites the animal becomes sterile by inhibition of the development of chitin, a vital polymer in the exoskeleton. These chemicals should have minimal effects on other species. 

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