Two-spotted spider mite,
Tetranychus urticae
Koch (Acari: Tetranychidae), is a cosmopolitan pest species that can feed on more than 1000 host plant species. Historically, organophosphate (OP) and ...carbamate insecticides have been used to control this extremely polyphagous pest. However, its ability to develop acaricide resistance rapidly has led to failure in control. Mutations in acetylcholinesterase gene (
ace
), the target-site of OP and carbamate insecticides, have been reported to be one of the major mechanisms underlying this developing resistance. In this study, mutations previously associated with resistance (G119S, A201S, T280A, G328A, F331W/Y) in
ace
have been screened in 37
T. urticae
populations collected across Turkey. All mutations were found in various populations, except G119S. Almost all populations had F331W/Y mutation (being fixed in 32 populations), whereas only two populations harboured A201S mutation, but not fixed. On the other hand, more than half of the populations contained T280A and G328A mutations. In addition, the presence of same haplotypes in populations originating from distinct geographic locations and a wide variety of
ace
haplotypes might indicate multiple origins of F331W and F331Y mutations; however, this needs further investigation. The results of area-wide screening showed that
ace
mutations are widely distributed among
T. urticae
populations. Therefore, the use of this group of insecticides should be limited or only rotational use might be regarded as a resistance management tool due to its different mode of action from other main acaricide groups in
T. urticae
control across Turkey.
Varroa destructor
is the most common ectoparasite of the Western honey bee (
Apis mellifera
L.) worldwide and poses a serious threat to bee health. Synthetic acaricides, particularly pyrethroids, are ...frequently used to control
Varroa
mites. However, long-term and repeated use of synthetic pyrethroids has led to the development of resistance. In this study, we report on the presence of resistance mutations in the voltage-gated sodium channel in
V. destructor
populations from Turkish beekeeping areas. Two resistance mutations, L925V and L925I, that were previously associated with pyrethroid resistance, were found in more than 75% of the populations. A general correlation between the presence of mutations and the history of acaricide usage was observed for the sampled hives. In addition, we show there is only a low genetic distance among the sampled
V. destructor
populations, based on the analysis of three mitochondrial genes: cytochrome
b
(
cytb
), ATP synthase subunit 6 (
atp6
), and cytochrome
c
oxidase subunit III (
cox3
). Revealing the presence and geographical distribution of pyrethroid resistance mutations in
V. destructor
populations from Turkish apiaries will contribute to create more effective mite management programmes.
The family Phytoseiidae contains many predatory mite species and some are used in biological control programs worldwide. The identification of phytoseiid mites is based on tiny morphological ...structures and sometimes species diagnosis is not easy especially for non-taxonomists. DNA-based approaches may offer a fast and accurate diagnosis to overcome these difficulties, nevertheless more DNA sequences are needed to determine intra- and inter-specific variations and to provide accurate decision rules based on genetic distances between the taxa considered. In this study, we provide the molecular characterization of seven phytoseiid species based on the internal transcribed spacer (ITS) region. Several populations of these species collected in Turkey were considered. A phylogenetic tree was also constructed. Finally, we record the presence of
Neoseiulus reductus
(Wainstein) in Turkey.
The Arachnida subclass of Acari comprises many harmful pests that threaten agriculture as well as animal health, including herbivorous spider mites, the bee parasite Varroa, the poultry mite ...Dermanyssus and several species of ticks. Especially in agriculture, acaricides are often used intensively to minimize the damage they inflict, promoting the development of resistance. Beneficial predatory mites used in biological control are also subjected to acaricide selection in the field. The development and use of new genetic and genomic tools such as genome and transcriptome sequencing, bulked segregant analysis (QTL mapping), and reverse genetics via RNAi or CRISPR/Cas9, have greatly increased our understanding of the molecular genetic mechanisms of resistance in Acari, especially in the spider mite Tetranychus urticae which emerged as a model species. These new techniques allowed to uncover and validate new resistance mutations in a larger range of species. In addition, they provided an impetus to start elucidating more challenging questions on mechanisms of gene regulation of detoxification associated with resistance.
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•Acari comprise several economically important mite and tick species.•Resistance development to acaricides is a serious worldwide problem.•New genomic tools have increased insights in resistance mechanisms.•Combinations of target-site and metabolic resistance can confer high resistance levels.•New detoxifying gene families were recently uncovered.•Gene regulation mechanisms in the context of resistance await further elucidation.
The codling moth
Cydia pomonella
is the major pest of apple orchards worldwide. Chemical insecticides are commonly used against pests; however, increased number of resistance cases highlights the ...urgent need for alternative control methods. Plant-derived essential oils are promising alternatives to chemical insecticides. Although they show great efficacies under laboratory conditions, their efficacy are lower in the field; requiring their formulation. Methyl-eugenol (ME) is a plant essential oil with insecticidal activity; however, knowledge on the efficacy of formulated forms and mode of action of ME is limited. Here, we developed two formulations of ME, an emulsion oil in water (EW) and an emulsifiable concentrate (EC). Bioassays on neonate larvae revealed a limited efficacy of non-formulated ME with the highest mortality of 34.1% at 15% concentration at 120 h after the application. The mortality caused by EW formulation without ME led to a maximum of 10% mortality, while the mortality caused by EW formulation with ME varied between 26.7 and 100% for the lowest and highest concentrations, respectively. As the EC formulation without ME led to 90% mortality, no further bioassay on the EC formulation of ME was conducted. EW formulation of ME showed strong contact toxicity against
C. pomonella
larvae after 120 h of application (LC
50
= 40.5 µL/cm
2
). Since ME is known to inhibit acetylcholinesterase, the relative expression levels of
AChE-1 and AChE-2
genes were examined in ME-exposed surviving larvae upon its plain application. Only
AChE-
1 was upregulated with a five-fold increase 24 h after treatment, which might be the reason for the survival of the larvae. Overall, the EW formulation of ME has great potential against codling moth. Further studies under field conditions will be helpful to use this essential oil in integrated pest management programs.
Graphical abstract
Varroa destructor
Anderson & Trueman (Acari: Varroidae) is of paramount significance in modern beekeeping, with infestations presenting a primary challenge that directly influences colony health, ...productivity, and overall apicultural sustainability. In order to control this mite, many beekeepers rely on a limited number of approved synthetic acaricides, including the pyrethroids tau-fluvalinate, flumethrin and organophosphate coumaphos. However, the excessive use of these substances has led to the widespread development of resistance in various beekeeping areas globally. In the present study, the occurrence of resistance mutations in the voltage-gated sodium channel (VGSC) and acetylcholinesterase (AChE), the target-site of pyrethroids and coumaphos, respectively, was examined in
Varroa
populations collected throughout the southeastern and eastern Anatolia regions of Türkiye. All
Varroa
samples belonged to the Korean haplotype, and a very low genetic distance was observed based on cytochrome c oxidase subunit I (
COI
) gene sequences. No amino acid substitutions were determined at the key residues of AChE. On the other hand, three amino acid substitutions, (L925V/I/M), previously associated with pyrethroid resistance, were identified in nearly 80% of the Turkish populations. Importantly, L925M, the dominant mutation in the USA, was detected in Turkish
Varroa
populations for the first time. To gain a more comprehensive perspective, we conducted a systematic analysis of the distribution of pyrethroid resistance mutations across Europe, based on the previously reported data.
Varroa
populations from Mediterranean countries such as Türkiye, Spain, and Greece exhibited the highest frequency of resistance mutation. Revealing the occurrence and geographical distribution of pyrethroid resistance mutations in
V. destructor
populations across the country will enhance the development of more efficient strategies for mite management.
Mitochondrial electron transfer inhibitors at complex II (METI-II), also referred to as succinate dehydrogenase inhibitors (SDHI), represent a recently developed class of acaricides encompassing ...cyflumetofen, cyenopyrafen, pyflubumide and cyetpyrafen. Despite their novelty, resistance has already developed in the target pest, Tetranychus urticae. In this study a new mutation, H146Q in a highly conserved region of subunit B of complex II, was identified in a T. urticae population resistant to all METI-IIs. In contrast to previously described mutations, H146Q is located outside the ubiquinone binding site of complex II. Marker-assisted backcrossing of this mutation in a susceptible genetic background validated its association with resistance to cyflumetofen and pyflubumide, but not cyenopyrafen or cyetpyrafen. Biochemical assays and the construction of inhibition curves with isolated mitochondria corroborated this selectivity. In addition, phenotypic effects of H146Q, together with the previously described H258L, were further examined via CRISPR/Cas9 gene editing. Although both mutations were successfully introduced into a susceptible T. urticae population, the H146Q gene editing event was only recovered in individuals already harboring the I260V mutation, known to confer resistance towards cyflumetofen. The combination of H146Q + I260V conferred high resistance levels to all METI-II acaricides with LC50 values over 5000 mg a.i./L for cyflumetofen and pyflubumide. Similarly, the introduction of H258L via gene editing resulted in high resistance levels to all tested acaricides, with extreme LC50 values (>5000 mg a.i./L) for cyenopyrafen and cyetpyrafen, but lower resistance levels for pyflubumide and cyflumetofen. Together, these findings indicate that different mutations result in a different cross-resistance spectrum, probably also reflecting subtle differences in the binding mode of complex II acaricides.
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•Succinate dehydrogenase inhibitors (SDHI) are recently developped acaricides.•A population resistant to all commercial SDHI acaricides was detected.•A H146Q mutation in sdhB was validated by marker-assisted backcrossing, biochemical assays and CRISPR-Cas9 knock-in.•H146Q confers high levels of resistance to cyflumetofen and pyflubumide, but not cyenopyrafen and cyetpyrafen.
The family Tetranychidae includes many agriculturally important species known as spider mites. Their morphological identification is quite difficult due to the tiny size of their taxonomic characters ...and the requirement for high-level expertise. This may lead to pest misidentification and thus failure in pest management. DNA-based species identification seems to offer an alternative solution to overcome these issues. In the present study, two common molecular markers—
Cytochrome oxidase subunit I
(
COI
) and Internal transcribed spacer 2 (ITS2)—were used to identify 10 spider mite species from Turkey. Furthermore, genetic distances for several of them were assessed.
Panonychus ulmi
and
Bryobia kissophila
had the lowest (1.1%) and highest (4.5%) intra-specific genetic distances, respectively. In addition, integrative taxonomy allowed to identify
Eotetranychus quercicola
in Turkey as a new record. The sequences herein obtained will allow rapid species identification using molecular techniques and will contribute to resolve the phylogenetic history of spider mites.
The black cutworm (BCW), Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is an economically significant pest affecting numerous crops and turf grasses. Despite employing various methods, such as ...chemical and biological control, to mitigate this pest, the efficacy of these methods often fails to reach the desired level. Hence, the integration of diverse strategies is a key to sustainable management. In this study, we assessed the toxicity of four insecticides (indoxacarb, pyridalyl, lufenuron, and methoxyfenozide) and three local EPN isolates (two isolates of Heterorhabditis indica and one of Heterorhabditis bacteriophora) in targeting the fifth instar larval (L5) and pupal stages of BCW. After demonstrating their potential use in BCW control, we explored the combined use of sublethal concentrations of insecticides (LC15 or LC30) alongside the LC20 values of EPNs. The findings revealed that lufenuron and methoxyfenozide, when combined with EPNs, exhibited a synergistic effect on the L5 stage of BCW, whereas the same combination displayed antagonism on pupae. On the other hand, the combination of indoxacarb and pyridalyl with EPNs demonstrated a synergistic effect on the pupal stage of BCW. These results highlight the potential of employing a combination of insecticides and EPNs at sublethal concentrations to control BCW effectively. This approach shows promise for designing sustainable pest management strategies within the framework of integrated pest management (IPM).
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•The potential of indoxacarb, pyridalyl, lufenuron, and methoxyfenozide, was shown in managing A. ipsilon.•Entomopathogenic nematodes (EPNs), particularly Heterorhabditis bacteriophora, have shown virulence against A. ipsilon.•Synergistic effects were observed when H. indica isolates were combined with lufenuron or methoxyfenozide.•Variations in the efficacy of these combinations were observed between the larval and pupal stages of A. ipsilon.•Integrating EPNs with insecticides presents a promising and sustainable approach for managing A. ipsilon populations.
Ketoenol acaricides have been widely used to control Tetranychus urticae populations across the world. However, control failure due to resistance development is an increasing concern. To sustain ...resistance management, it is therefore important to understand the molecular mechanisms underlying resistance, as well as understand the level of cross-resistance they convey between different ketoenol acaricides, such as spirodiclofen or spiromesifen. A T. urticae population with moderate levels of resistance to ketoenols was collected from a carnation greenhouse and further selected in the laboratory with spirodiclofen and spiromesifen, separately, until high levels of resistance were achieved. Synergism assays indicated the involvement of P450 monooxygenases and, to a lesser extent, carboxyl/cholinesterases in resistance. Genome-wide gene expression analysis of ketoenol-selected populations compared to the initial field-collected population and a susceptible reference laboratory population further supported the hypothesis of P450-mediated resistance to ketoenols. In addition to metabolic resistance, target-site resistance was also investigated, but no amino acid substitutions in the carboxyl-transferase (CT) domain of the acetyl-CoA carboxylase (ACCase), the target-site of ketoenols, were found in the studied populations. However, increased expression of ACCase was found in the spiromesifen-selected, but not in the spirodiclofen-selected population. Finally, changes in resistance levels of some commonly used acaricides were identified after selection with spiromesifen or spirodiclofen.
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•A field-collected T. urticae population was selected with spirodiclofen and spiromesifen, separately.•Shared and unique molecular responses to ketoenol resistance were identified.•The results supported the P450-mediated resistance to ketoenols.•No mutations were found in ACCase.•The potential risk of cross-resistance between ketoenols and several acaricides was determined.
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