Development of resistance to insecticides

Carboxylesterases are well-represented in insects and are sometimes important in the development of resistance to insecticides. Thus, a well-characterized carboxylesterase E4 is responsible for resistance to organophosphorus insecticides in the aphid (Myzuspersicae) [107]. In the California Culex mosquito, the esterase B1 is 500-fold more abundant in organophosphate-resistant than in susceptible insects. The increase of esterase levels is the result of gene amplification, i.e., the resistant animals have an increased number of copies of the structural esterase gene [108],... 

INCREASED FACTORS OF SYNERGISM WITH THE DEVELOPMENT OF RESISTANCE TO INSECTICIDES... 

The world is never without prophets and during this era, several spoke and they—in the usual manner of prophets—spoke in vain. Development of resistance to insecticides was the first theme of the... 

Resistance to insecticides has drawn global attention since the Korean War in 1950 when the mass use of organic synthetic insecticides, such as DDT and BHC, against agricultural pests and sanitary pests became common. Organophosphorus compounds and carbamates were used thereafter, but invited problems of safety concerns and insect resistance. Synthetic pyrethroids were watched with keen interest as alternatives and have become used widely not only for sanitary pests but also agricultural pests. The development of resistance to synthetic pyrethroids is also not a rare phenomenon and has spread all over the world. 

The human toxicity of DDT has been a subject of intense study during the last 20-25 years. This led the World Health Organisation to prohibit the use of DDT as an insecticide. The long-term use of DDT resulted in the development of resistance to the insecticide in many pests (over 200 species). As a result, most developed countries initiated programmes for the gradual replacement of DDT. The manufacture of DDT, and consequently that of chloral, has been in gradual decline since 1963 [12, 13,17]. 

Cross-resistance refers to a situation in which a strain that becomes resistant to one insecticide automatically develops resistance to other insecticides to which it has not been exposed. For example, selection of a strain of Spodoptera littoralis with fenvalerate resulted in a 33-fold increase in tolerance to fenvalerate. The resistant strain also showed resistance to other pyrethroids (11- to 36-fold) and DDT (lower than for the pyrethroids). Exposure of Cidex qninquefasciatus to fenitrothion resulted in the development of resistance to the carbamate insecticide propoxur. Similarly, selection of a housefly strain with permethrin resulted in a 600-fold increase in resistance to permethrin. The resistant strain also showed resistance to methomyl, DDT, dichlorvos, and naled (Hassall, 1990). 

J ousefly infestations have been controlled primarily by insecticidal measures, but with the development of resistance to the majority of available insecticides, new measures have been sought. Preliminary... 

DDT-dehydrochlorinase is only one of the enzymes causing detoxification of DDT. Also important in this respect are those mixed function oxydases which decrease the effect of DDT by inducing oxidative degradation. In his experiments carried out on Heliothis species, Plapp (1973) showed that the development of resistance to DDT can be traced back to oxidative enzymes. The field of action of these enzymes involves a wide range of insecticides. Accordingly, the effect of those anti-resistant compounds — the action of which is based on the inhibition of oxydases — is more general and concerns almost all types of insecticides. 

Despite the development of resistance to DDT in some populations of Anopheles mosquitoes, DDT remains generally effective when used for house spraying due to excitorepellency as weU as insecticidal effects." " DDT is still available and used in IRS components of malaria control programs, mainly due to a lack of equally effective and cost-comparable alternatives." ... 

Apart from the resistance of insects to insecticides, resistance has been developed by plants to herbicides, fungi to fungicides, and rodents to rodenticides. Rodenticide resistance is discussed in Chapter 11, Section 11.2.5. 

The complexity of the new insecticidal chemicals brings many other problems. Synthetic organic chemicals are not effective against all pests. There is a marked selectiveness in action even between closely related species of insects. Some insects have already developed resistance to some of the newer materials. The idea of insects developing resistance to certain chemicals is not new. The over-all principle is well established in a few cases. The early development of flies resistant to DDT, a chemical which had been highly and universally effective for fly control, came as a surprise. Other cases of resistance to DDT are being indicated, and at least one kind of mite has developed resistance against another of the newer chemicals—parathion. 

Another extremely important military characteristic is effectiveness against many different species of insects without the development of resistant strains. Every insecticide that must be added to the military list of supplies geometrically increases the difficulties of procurement and distribution. At the present time, nineteen different insecticides and insect repellents and four different rodenticides are issued by the Army Quartermaster. These figures do not include the different formulations of insect repellents issued under the same stock number. The three basic insect repellents are dimethyl phthlate, Indalone, and Rutgers 612. These repellents are issued either alone or in various combinations, further complicating the supply situation because of the variation in efficiency of these substances against different species of mosquitoes in different parts of the world. 

The development of resistant strains of an insect to a given insecticide is not new. Melander (7) in 1914 pointed out that the San Jose scale in Washington had developed a resistance to lime-sulfur sprays. Recently Babers (1) of the Bureau of Entomology and Plant Quarantine brought together an excellent evaluation and summary of the literature dealing with the development of insect resistance to insecticides he lists 111 references to work on this phenomenon. 

A. aegypti colonies were found to have developed cross-resistance to even polyfluoro benzylalcohol ester pyrethroids with potent insecticidal activity. Mosquito coils of these compounds were effective against allethrin-susceptible A. aegypti colonies at ultra-low concentration, but needed several times higher concentrations for A. aegypti colonies in Group III in Table 8 (unpublished). 

Currently there are few insecticides registered as surface treatments to control stored-product insects. For years the organophosphate insecticide malathion was used as a surface treatment for structural facilities, but stored-product insects throughout the world have developed extensive resistance to malathion (Subramanyam and Hagstrum, 1996). Most of the resistance reports were generated from studies with bulk grains, but in the United States, resistance has been documented for field populations of the red flour beetle, T. castaneum (Herbst), and the confused flour beetle, T. confusum (DuVal), collected from flour mills (Arthur and Zettler, 1991, 1992 Zettler, 1991). Populations of the Indianmeal moth, the almond moth, and the red flour beetle collected from bulk peanuts and empty warehouses were also highly resistant to malathion (Arthur et al., 1988 Halliday et al., 1988). 

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