Current situation and forecasting of resistance evolution to lambda‐cyhalothrin in Spanish medfly populations

Abstract

BACKGROUND The control of the Mediterranean fruit fly Ceratitis capitata (Wiedemann) in Spanish field populations mainly relies on the insecticides lambda‐cyhalothrin and spinosad as bait sprays. However, their sustainable used is compromised by the development of lambda‐cyhalothrin resistance and the detection of spinosad resistant alleles. In addition, the use of lure‐and‐kill traps covered with deltamethrin has increased in the last years. It is thus urgent to predict the impact that the combination of both pyrethroids will have in the evolution of lambda‐cyhalothrin resistance and how they could be combined with spinosad so as to establish proper resistance management programs. RESULTS Toxicity bioassays were performed to analyze the current levels of lambda‐cyhalothrin resistance in field populations, proving that it has remained stable in the last decade. An evolutionary model was established to explore the weight of selected parameters in the evolution of lambda‐cyhalothrin resistance in C. capitata and to forecast resistance development under different resistance management scenarios. Our results highlight the importance of fitness cost and inheritance to fit the experimental results. The analyses predicted that the rotation of lambda‐cyhalothrin and spinosad, when deltamethrin traps are also deployed in the field, will slow down the evolution of resistance, especially when cross‐resistance between both pyrethroids is considered. CONCLUSION Lambda‐cyhalothrin resistance has not increased in the last decade, probably due to the alternation of this insecticide with spinosad. Our modelling results indicate that the best option to avoid an increase in lambda‐cyhalothrin resistant alleles, considering that deltamethrin use is growing, would be to continue combining their use with spinosad. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

First detection of resistance to deltamethrin in Spanish populations of the Mediterranean fruit fly, Ceratitis capitata

“…An important component of IRM is the use of alternative insecticides to delay the onset of resistance to a particular insecticide and avoid the combined use of insecticides with cross-resistance. We have found deltamethrin resistance in geographic areas where lambda-cyhalothrin resistance already existed (Arouri et al 2015;Guillem-Amat et al 2022). Thus, it is possible that resistance to lambdacyhalothrin is conferring cross-resistance to deltamethrin, though they may also have evolved independently by different resistance mechanisms.…”

“…However, care should be taken when combining deltamethrin traps and lambdacyhalothrin sprays, since our results indicate that different scenarios of cross-resistance between these two pyrethroids may occur for Medfly populations in the area of study. Guillem-Amat et al (2022) simulated the evolution of lambda-cyhalothrin resistance under different crossresistance scenarios with deltamethrin and concluded that the efficacy of both pyrethroids would be seriously compromised under the assumption of cross-resistance, even when partial. Thus, farmers should avoid the overuse of both pyrethroids in the same fields for long periods of time, as there is a risk of cross-resistance between them.…”

“…The domains II and III of the voltage-gated sodium channel (VGSC) gene (XM_020861574) were partially sequenced to cover most of the codons associated to knockdown resistance (kdr) mutations in insect species, as previously described 1 3 (Guillem-Amat et al 2022). We analyzed 20 flies from: (i) the field populations collected in Betxi in 2017 and in Benaguasil and Picassent in 2018 that survived to the bioassays with MagnetMed™; and (ii) the deltamethrin-resistant strains BP-delta and Rfg-delta, that survived to the exposure to Decis Protech in contact bioassays.…”

“…We analyzed 20 flies from: (i) the field populations collected in Betxi in 2017 and in Benaguasil and Picassent in 2018 that survived to the bioassays with MagnetMed™; and (ii) the deltamethrin-resistant strains BP-delta and Rfg-delta, that survived to the exposure to Decis Protech in contact bioassays. The oligonucleotides used were NaCh899_F (5'-TCG AGT TTT TAA ACT TGC CAAA) and NaCh932_R(5'-TTT CCG AAC AGT TGC ATT CC) for region 899-932, Kdr_F (5'-TCG TTT TTC GTG TGC TAT GC) and Kdr_R (5'-CCA GGC TTT AAA ACG CGA TA) for region 977-1058, and NaCh1528_F (5'-AAG CAA CCA ATC CGT GAA AC) and NacCh1575_R (5'-TCG GTC TAG GAA TGG CTT TT) for region 1528-1575(Guillem-Amat et al 2022. The amplicons were visualized on 1% agarose (Agarosa D2, Conda Pronadisa, Madrid, Spain) gels (Tris 40 mM, EDTA 1 mM, pH 8.0), purified using the QIAquick PCR Purification Kit (QIAGEN, Germany), and sequenced by Sanger at Secugen S.L.…”

“…Since 2009, malathion was restricted in the European Union and other insecticides gained importance in Medfly control, such as spinosad and the pyrethroid lambda-cyhalothrin used as bait sprays. However, field resistance to lambda-cyhalothrin was shortly detected (Arouri et al 2015) and resistance rates have remained stable during the last decade (Guillem-Amat et al 2022). Field resistance to spinosad has not been reported yet (Ureña et al 2019), but resistant alleles to this insecticide have been already detected at low frequency in field populations (Guillem-Amat et al 2020a).…”