Insecticidal Resistance Monitoring in mitotypes of Bemisia tabaci in South Punjab region of Pakistan

Abstract

Abstract Whitefly (Bemisia tabaci Gennadius) (Hemiptera: Aleyrodidae) is a serious pest of several summer crops in hot and dry climates with diverse cryptic species complex worldwide. Among 7 major clades of B. tabaci; Asia-II is predominant in the cotton zone of Punjab-Pakistan. Cotton is one of the favorite hosts of B. tabaci, where it feeds and spread different plant viruses. In Pakistan, the primary approach used to manage B. tabaci in the cotton environment is through the use of synthetic pesticides. A vital tool for the effective management of B. tabaci is the monitoring of insecticidal resistance. Different cotton field strains were collected from the four major cotton growing districts of South-Punjab to assess their genetic variability and resistance levels compared with the laboratory susceptible population against most commonly used insecticides during the years 2020 and 2021. Leaf-dip bioassays were performed on 2nd instar nymphal (N2) stage; while adult bioassays were conducted on G1 stage on field collected populations. Genetic analysis of mtCOI revealed that all the populations were belonged to Asia II-1 clade. A mixture of three haplotypes of Asia II-I including haplotypes-2, haplotype-3 and haplotype-4 was identified from Jampur and Bahawalpur samples. However, haplotype-4 and haplotype-3 were identified from Multan population while Vehari samples comprised of haplotype-4 and haplotype-2. Buprofezin (RR ranged 25.75–36.71), pyriproxyfen (RR ranged 7.98–12.78) and diafenthiuron (RR ranged 20.59–28.12) were least efficient products in adult bioassays and had moderate to low level of resistance. However, spirotetramat and flonicamid both were relatively effective against adults with low to very low resistance during both the years. Pyriproxyfen demonstrated least efficacy for reducing adult emergence followed by flonicamid and buprofezin with moderate to very low resistance ratio respectively. In contrast spirotetramat (RR ranged 2.20–4.01), was highly effective against nymphs followed by diafenthiuron (RR ranged 4.63–7.68), having very low resistance ratio. However an upward trend of resistance development was observed against all the five tested insecticides during both the monitoring years. Current study concluded that different mitotypes/haplotypes of B. tabaci have various level of insecticidal resistance to the old conventional insecticides. These results establish a regional baseline that can serve as a reference for future monitoring and management of B. tabaci resistance to the tested insecticides.