Deltamethrin resistance

Resistance to py rethroids can also be in part attributed to reduced penetration in insects. Ahmad et al. (2006) found that delayed cuticular penetration played an important role in deltamethrin resistance in Chinese and Parkinson strains of the cotton bollworm, Helicov-erpa armigera. The half-time for applied deltamethrin was 1 hr for the susceptible strain and 6 hr for both of the resistant strains. 

Kumar, S., Thomas, A., Sahgal, A., Verma, A., Samuel, T., and Phillai, M.K.K., Effect of the synergist, piperonyl butoxide, on the development of deltamethrin resistance in yellow fever mosquito, Aedes aegypti L. (Diptera Culicidae), Arch. Insert Biochem. Physiol., 50,1, 2002. 

In a parallel selection study, a 137-fold deltamet hi in-resistant strain when subject to continuous selection pressure with synergized della me thrin, showed 76 reversion in resistance in the lirst generation and significantly retarded the development of resistance in subsequent generations. Thomas ef al. concluded that even though high larval resistance develops under intense laboratory selection. the addition of PBO can drastically reduce the speed of development of deltamethrin resistance in this species of mosquito. 

Zhu F, Parthasarathy R, Bai H, Woithe K, Kaussmann M, Nauen R, Harrison DA, Palli SR (2010) A brain-specific cytochrome P450 responsible for the majority of deltamethrin resistance in the QTC279 strain of Tribolium castaneum. Proc Natl Acad Sci U S A 107 8557-8562... 

Tabarean IV, Narahashi T (1998) Potent modulation of tetrodotoxin-sensitive and tetrodotoxin-resistant sodium channels by the type II pyrethroid deltamethrin. J Pharmacol Exp Ther 284 958-965... 

Vais H, Williamson MS, Goodson SJ, Devonshire AL, Warmke JW, Usherwood PN, Cohen CJ (2000) Activation of drosophila sodium channels promotes modification by deltamethrin. Reductions in affinity caused by knock-down resistance mutations. J Gen Physiol 115 305-318... 

Forshaw PJ, Ray DE (1990) A novel action of deltamethrin on membrane resistance in mammalian skeletal muscle and non-myelinated nerve fibres. Neuropharmacology 29 71-81... 

Sequestration in insects This is another resistance mechanism in which GSTs were found to be involved in pyrethroid resistance. Kostaropoulos et al. (2001) have reported that GST confers protection against deltamethrin by binding to the insecticide in the yellow mealworm ijenebrio monitor). 

Figure 10.9 Resistance ratios in successive generations of Aedes aegypti larvae subjected to different selection pressures. Open circle, selection with deltamethrin alone Triangle, selection of the parent susceptible strain with deltamethrin plus PBO (1 5) Solid circles, selection of F24 deltame-thrin-selected strain with deltamethrin plus PBO (1 5). (From Kumar, S., et al., Arch. Insect Biochem. Physiol., 50,1, 2002. With permission.)...

Ahmad, M., Denholm, I., and Bromilow, R.H., Delayed cuticular penetration and enhanced metabolism of deltamethrin in pyrethrin-resistant strains of Helicoverpa armigera from China and Pakistan, Pest Manag. Sci., 62, 805, 2006. 

Riskallah, M.R., Abd-Elghafar, F., Abo-Elghar, M.R., and Nassar, M.E., Development of resistance and cross-resistance in fenvalerate and deltamethrin selected strains of Spodoptera littoralis (Boisd.), Pestic. Sci.t 14,508,1983. 

Kyncrgized cyfluthrin is the main candidate protectant to compete with deltamethrin, in terms of high solo activity, and has been reviewed by Pospis-ehil and Smith (1994). They concluded that a dosage rate of 2 nig kg 1 syner-gi/ed by 10 mg kg"1 of PBO was sufficient to give at least 9 months protection even against resistant strains of insects. 

Thomas et al. (1991) induced 1449- fold resistance to deltaniethriii t[trough con tin nous larval selections of Quito quinqueftiM-iaiuji for 40 generations. When the larvae were subjected to selection pressure using deltamethrin and PBO (1 5) the speed of selection for del tame thrin resistance in the larvae slowed down considerably by 17 to 6195-. 

The action of deltamethrin on the GABA response was more difficult to determine, because low concentrations of deltamethrin caused depolarization and rapid firing of action potentials, accompanied by a decrease in membrane resistance. Deltamethrin at 0.1 nM caused a massive increase in firing frequency, and a depolarization of 30mV, after perfusion for ten minutes. Application of TTX, which specifically blocks voltage dependent sodium channels, abolished the action potentials, and also reversed the pyrethroid-induced depolarization and decrease in membrane resistance. 

Finally, it is possible that these techniques can be extended successfully to insect CNS preparations. Methods now exist to prepare functional insect synaptosomes from insect ganglia (1 ), and these preparations have been used to demonstrate veratridine-dependent neurotransmitter release and enhancement of this release by deltamethrin in a superfusion assay (2j)). Further refinement of these methods should allow direct measurement of sodium channel-mediated sodium fluxes in insect CNS preparations, thus allowing the investigation of target site differences not only between mammals and insects but also between susceptible and resistant insect strains. 

Figure 2. Responses of three strains of the housefly to single doses of deltamethrin and aconitine in a larval paralysis bioassay. Paralysis was assessed 10 min. after treatment and was defined as the loss of ability to perform a stereotypic curling movement. Resistance in the kdr and super-kdr strains is directed against both compounds. For each treatment group shown n = 60. The bar for deltamethrin in super-kdr is omitted because no paralysis was observed at dosages up to 20 p.g/larva (n = 40). Data were taken from Ref. 22.

The wide spectrum of pyrethroid resistance in these populations, which involves permethrin, fenvalerate, flucythrinate, cypermethrin, deltamethrin, and cyhalothrin, the relative lack of synergism by p. b. (52) or DEF, and the presence of DDT as well as methoxychlor resistance (52), suggest that this resistance is due to the site insensitivity mechanism kdr. Interestingly, some evidence of behavioral resistance was also detected. It was observed that pyrethroid-resistant flies tended to... 

In the middle of the 20th century, the synthetic development of DDT and other chlorinated hydrocarbons (C.H.), increased insecticidal activity well beyond that of most natural products. Problems arose with bioaccumulation of C.H. residues in the food chain, human fat tissue, mother s milk, as well as the development of insecticide resistance. It became obvious there were limitations to synthetic technology as well. The modification of a natural product, for example, from chrysanthemum flowers and their pyrethrum extracts (7) to pyrethroids such as allethrin, resmethrin, permethrin (2), and deltamethrin created a model in which insecticides are created from the skeleton of insecticidally active natural molecules. Thus, the avermectin, abamectin, ivermectin family of pesticides originated from compounds produced by the soil bacterium, Streptomyces avermitilis (5), and the commercially successful chloronicotinyl insecticides, though not derived from nicotine, are chemically related 4). Both pyrethroids and chloronicotinyls are currently used commercially as termiticides. We have previously provided a detailed review of natural products as pesticidal agents for control of the Formosan subterranean termites, Coptotermes formosanus Shiraki (5). 

Some pyrethroids are especially useful for wood preservation due to their physico-chemical parameters, e.g. very low vapor pressure, high UV-resistance and very low water solubility, resulting in a long-term protection of technical material. Today the active ingredients Permethrin, Cypermethrin, Cyfluthrin, Deltamethrin and Bifenthrin (Figure 18 and 19) are used in wood protection. Due to their long-term protection and their fast action these compounds can be used in preservative and curative applications. Table 7 summarizes the efficacy in tests according to European standards EN 21 and EN 47. 

Wheelock GD, Scott JG (1992) The role of cytochrome- P450IPR in deltamethrin metabolism by pyrethroid-resistant and susceptible strains of house-flies. Pestic Biochem Physiol 43 67-77 Wheelock GD, Shan G, Ottea J (2005) Overview of carboxylesterases and their role in the metabolism of insecticides. J Pestic Sci 30 75-83... 

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