The main purpose of this study is to provide essential information regarding the molecular basis of insecticide resistance and to report candidate genes which are responsible for resistance in insects/pests. There are two basic resistance mechanisms existing in pests, i.e., target site resistance and metabolic resistance. During resistance of target site, the specific binding site of an insecticide is modified (mutated) and/or lost, which makes the target site incompatible for activation. Mutation occurs in most common pest (Myzus persicae, Musca domestica and Drosophila melanogaster) target regions, i.e., subunits like nicotinic acetylene choline receptors (nAChRs), knock-down resistance (KDR) etc. Due to these mutations, insecticides are unable to bind into the target region, resulting in loss of binding affinity. Furthermore, in metabolic resistance over production of enzymes occurs which break down (detoxify) insecticides and resulting resistance of pests. The amplification of metabolic enzymes, i.e., Cytochromes p450 monooxygenase, hydrolyses, and Glutathione S-transferase play a central role in evolving metabolic resistance. Various successful approaches are used to combat pests resistance such as insecticides, bio-pesticides and biological control agents. However, some of these strategies have certain limitations such as contamination of the environment, while others possess a low capacity in management of pests. Recent studies have highlighted some novel mechanisms of insecticide resistance that are part of the ongoing efforts to define the molecular basis of insecticide resistance in insect species.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a significant agricultural pest that has developed resistance to many insecticides that are used to control it. Investigating the mechanisms of insecticide detoxification in this pest is important for ensuring its continued control, since they may be contributors to such resistance. Multidrug resistance (MDR) genes that code for the ABCB transmembrane efflux transporters are one potential source of insecticide detoxification activity that have not been thoroughly examined in L. decemlineata. In this study, we annotated the ABCB genes found in the L. decemlineata genome and then characterized the expression profiles across midgut, nerve, and Malpighian tubule tissues of the three full transporters identified. To investigate if these genes are involved in defense against the macrocyclic lactone insecticide ivermectin in this insect, each gene was silenced using RNA interference or MDR protein activity was inhibited using a chemical inhibitor, verapamil, before challenging the insects with a dose of ivermectin. Survival of the insects did not significantly change due to gene silencing or protein inhibition, suggesting that MDR transporters do not significantly contribute to defense against ivermectin in L. decemlineata.

The sweet potato (cotton) whitefly Bemisia tabaci is a major agricultural pest in various fields and vegetable crops worldwide. It causes extensive damage by direct feeding on plants, reducing quality, secreting honeydew and transmitting plant viruses. B. tabaci is known for its genetic diversity and considered a complex of biotypes or, as suggested, a complex of distinct cryptic species. Management of whiteflies relies mainly on the use of insecticides; however, its ability to develop resistance to major insecticide classes creates a serious challenge to farmers and pest control specialists. Among the cryptic species of B. tabaci, MED is considered more resistant than the MEAM1 to insecticides such as pyriproxyfen and neonicotinoids; however, in recent years there are other species of B. tabaci including MEAM1, Asia I and Asia II-1 that have developed high resistance to various groups of insecticides. Advanced methods based on molecular and gene sequence data obtained from resistant and susceptible field-collected B. tabaci populations resulted in a better understanding of resistance mechanisms in this pest. Several components of IPM-IRM (Integrated Pest Management-Insecticide Resistance Management) programs such as selective and biorational insecticides, insecticide rotation with different modes of action and nonchemical control methods are among the countermeasures of insecticide resistance management for this pest. In the current review, we concentrate on insecticide resistance and resistance management of B. tabaci, focusing on reports published mainly over the past 10 years.

Insecticide resistance is one of the most widespread genetic changes caused by human activity, but we still understand little about the origins and spread of resistant alleles in global populations of insects. Here, via microarray analysis of all P450s in Drosophila melanogaster, we show that DDT-R, a gene conferring resistance to DDT, is associated with overtranscription of a single cytochrome P450 gene, Cyp6g1. Transgenic analysis ofCyp6g1 shows that overtranscription of this gene alone is both necessary and sufficient for resistance. Resistance and up-regulation in Drosophila populations are associated with a single Cyp6g1 allele that has spread globally. This allele is characterized by the insertion of an Accord transposable element into the 5′ end of the Cyp6g1 gene.

Insecticide resistance to representatives of commonly used insecticide groups (pyrethroids—cypermethrin; organophosphates—chlorpyriphos; cyclodienes—endosulfan) was determined in five major insect pests of cotton from the main cotton growing regions of India with emphasis on Andhra Pradesh and Maharashtra. The cotton bollworm Helicoverpa armigera (Hubner) exhibited widespread resistance to cypermethrin with 23–8022-fold resistance being recorded in field strains. Resistance to endosulfan and chlorpyriphos was low to moderate in H. armigera. The overall resistance of the pink bollworm Pectinophora gossypiella (Saunders) to pyrethroids was low. However, high resistance levels of 23–57-fold to endosulfan were recorded in some areas of Central India. Resistance to chlorpyriphos was high in the Medak, Bhatinda and Sirsa strains from North India. The majority of the Spodoptera litura (Fab.) strains collected in South India exhibited high resistance levels of 61–148-fold to cypermethrin. Resistance to endosulfan was high only in two strains, collected from Bhatinda and Karimnagar in North India. The S. litura strains from South India exhibited high levels of resistance at 45–129-fold to chlorpyriphos. Insecticide resistance in Earias vittella (Fab.) was low to moderate in the Sirsa and Sriganganagar strains from North India. Bemisia tabaci (Genn.) exhibited moderately high levels of resistance to cypermethrin, but resistance to endosulfan and chlorpyriphos was negligible in the field strains tested. The implications of resistance for cotton pest management in India are discussed.