TY  - JOUR
JF  - Acarologia
T1  - Cross-resistance spectra and sequential reselection for multi-class pesticide resistance in the predatory mite Amblyseius swirskii (Acari: Phytoseiidae)
VL  - 66
IS  - Suppl
SP  - 198
EP  - 198
PY  - 2026
SN  - 0044-586X
SN  - 2107-7207
PB  - Les Amis d'Acarologia
AU  - Ceren, Dogan
AU  - Nabi Alper, Kumral
AU  - Ceren, Dogan
AU  - Nabi Alper, Kumral
UR  - https://doi.org/10.24349/2c4v-ezon
DO  - 10.24349/2c4v-ezon
DA  - 2026-07-20
ET  - 2026-07-20
KW  - Amblyseius swirskii
KW  - Artificial selection
KW  - Cross-resistance
KW  - Integrated Pest Management
KW  - Multiple resistance
AB  - Understanding cross-resistance in the predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is essential for its successful integration into greenhouse Integrated Pest Management (IPM). This study characterized cross-resistance in a laboratory-selected abamectin- and bifenazate-resistant A. swirskii population against active ingredients with distinct modes of action (MoA): azoxystrobin, deltamethrin, spiromesifen, fluazinam, chlorantraniliprole, milbemectin, and pyridaben. Consequently, a sequential reselection program was implemented to develop multi-resistance against a tactical suite of pyridaben, deltamethrin, and azoxystrobin. The study aims to provide critical insights into the development of robust biocontrol agents capable of maintaining efficacy within complex chemical landscapes. Cross-resistance profiles were determined via concentration–mortality bioassays using adult females with the dry residue method applied with a standardized spray tower, with at least three replicates per treatment. Following the initial screening, the resistant population underwent subsequent reselection using LC50–60 concentrations of azoxystrobin, deltamethrin, and pyridaben, representing different classes (fungicide, insecticide, and acaricide, respectively). Survivorship, fecundity, and predation rates of adult females were evaluated relative to untreated controls and a susceptible reference population. Azoxystrobin exhibited the most pronounced shift; the resistant population showed an LC50 of 257 mL/100 L versus 42 mL/100 L for the susceptible strain (6.2-fold resistance ratio [RR]). Bifenazate (8.74-fold RR) and azoxystrobin (6.12-fold RR) displayed comparable resistance levels despite differing chemical classes, likely attributable to their shared target site (mitochondrial cytochrome bc1 complex, Qo site). Under sublethal azoxystrobin exposure (150 mL/100 L), the resistant population demonstrated superior resilience, with fecundity and consumption reduced by 47% and 16%, compared to severe declines of 76% and 35% in the susceptible population. Conversely, cross- resistance was negligible for deltamethrin (1.20-fold), chlorantraniliprole (1.16-fold), spiromesifen (1.09-fold), fluazinam (1.05-fold), and pyridaben (1.0-fold). Notably, despite high abamectin resistance (19.42-fold), no cross- resistance was observed for milbemectin (1.18-fold), indicating highly specific resistance mechanisms within IRAC Group 6 (acting as Chloride Channel Activators). Abamectin-bifenazate selection can coincide with reduced susceptibility to chemically unrelated compounds via target-site cross-resistance but does not confer broad- spectrum resistance. Ongoing selections with a tactical suite of pyridaben, deltamethrin, and azoxystrobin, will validate these strains for pesticide-compatible IPM. This research was funded by the Bursa Uludag University Scientific Research Unit under grant number FGA-2026-2604.
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