Development of acaricide resistance in Pacific spider mite (<Emphasis Type="Italic">Tetranychus pacificus</Emphasis>) from California vineyards

In recent years, grape growers in California reported failures of acaricides against Tetranychus pacificus McGregor. We collected T. pacificus populations from four vineyards and tested them for resistance to bifenazate, propargite and pyridaben. In addition, we sequenced part of the cytochrome b gene of bifenazate-resistant and -susceptible T. pacificus to test for the presence of mutations reported to confer resistance to the congeneric T. urticae. None of the mutations conferring resistance to bifenazate in T. urticae were present in resistant T. pacificus. Resistance levels ranged from full susceptibility to statistically significant 11-fold resistance to pyridaben, sevenfold resistance to bifenazate and fourfold resistance to propargite compared to a susceptible population. Despite the relatively low levels of resistance detected, we estimated that under the conditions of our study the highest field rates of bifenazate and pyridaben application would cause less than 58 and 66% mortality of adult females in the most resistant populations, respectively. In contrast, field rates of propargite application would cause close to 100% mortality in the least susceptible population. These results highlight a potential link between resistance development and reduced field effectiveness for bifenazate and pyridaben. Finally, T. pacificus may be more tolerant to bifenazate and propargite than T. urticae, since the LC₅₀ values for the susceptible population of T. pacificus were several times higher than LC₅₀’s reported for susceptible T. urticae.     

Potentiation of a propargite and fenpyroximate mixture against two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

Using susceptible and resistant reference strains and standard bioassay methods a new miticide product was screened for efficacy and cross-resistance against two-spotted spider mite, Tetranychus urticae Koch. Experimental product NN1 850.0 EW (fenpyroximate and propargite 3:10 ratio) was significantly (P<0.05) more toxic than either compound tested alone (co-toxicity index 1029). Non-overlapping 95% CIs at the LC₅₀ and LC₉₉ level suggest that there is no cross-resistance to NN1 850.0 EW from existing organophosphate and pyrethroid resistance. NN1 850.0 EW is worthy of further development for T. urticae control.     

Monitoring of acaricide resistance of Tetranychus urticae (Acari: Tetranychidae) from Korean apple orchards

Tetranychus urticae populations were collected from ten commercial apple orchards and their susceptibilities to 12 acaricides were tested using a leaf disc bioassay. The resistance of each T. urticae population was reported as the LC₅₀ value, the resistance ratio (RR) and the slope of the probit–concentration regression. Cross resistances of T. urticae populations were estimated using the Spearman's rank correlation coefficient. Most local populations showed low resistance levels (RR ≤ 10). Development of resistance to METI and pyrethroid acaricides differed among local populations. The highest RR value (154.6) was found in the Uiseong population to tebufenpyrad. The Geochang population was highly resistant, especially to METI and pyrethroid acaricides. T. urticae populations collected from Suwon, Chungju, Yeongju and Geochang showed moderate resistance (10 < RR ≤ 40) to more than two acaricides. Resistance ratios to abamectin, chlorfenapyr, fenbutatin-oxide and milbemectin were low (RR ≤ 10) in all populations. The LC₅₀ values of abamectin, chlorfenapyr, fenbutatin-oxide and milbemectin ranged from 0.06 to 0.2 mg/l, from 0.67 to 3.38 mg/l, from 10.12 to 40.85 mg/l and from 0.47 to 3.01 mg/l, respectively. We discuss possible cross-resistance to acaricides using Spearman's rank correlation coefficient.     

Spider mite resistance to miticides in South Carolina strawberry and implications for improved integrated pest management

Tetranychus urticae Koch (Acari: Tetranychidae), twospotted spider mite, is a major secondary pest of strawberry and can cause significant yield loss. Tetranychus urticae is typically controlled using miticides, which has led to rapid resistance development. In South Carolina (USA), extension agents and growers have reported field failures of miticides (inadequate pest suppression), but resistance has not been quantitatively determined. In 2018, we determined the level of miticide resistance of six T. urticae populations found on strawberry across South Carolina. We examined efficacy of all miticides registered for use on US strawberry by conducting an initial diagnostic bioassay at 20% of the maximum labeled field rate. Any population?×?active ingredient combination resulting in?<?55% mortality was identified as ‘potentially resistant’ and concentration–response bioassays were then conducted to calculate LC₅₀ values for an individual population. These values were compared with those of a known-susceptible laboratory population to calculate resistance ratios (RR). Our results indicate that examined South Carolina populations of T. urticae from strawberry were highly resistant to bifenthrin (RR?=?100–60,000) and there was reduced susceptibility to fenbutatin-oxide (RR?=?25–123). The 'Sardinia' population had decreased abamectin susceptibility (RR?=?25). No resistance to hexythiazox, etoxazole, acequinocyl, bifenazate, fenpyroximate, spiromesifen, or cyflumetofen was found. Based on available data, it appears that miticide resistance is not a likely cause of field failures and issues related to application error and coverage should be investigated. Overall, this work supports the need to reduce the use of broad-spectrum pesticides and older products, in favor of newer miticide chemistries due to resistance issues.

     

The effect of groundcover and herbicide treatment on twospotted spider mite density and dispersal in southern Oregon pear orchards

A total of 49 groundcover plant species representing 47 genera in 22 families were identified from a survey of 5 pear orchards. Density of twospotted spider mite (Tetranychus urticae Koch) inhabiting these plants was estimated visually several times during the field season. Plants were ranked in 1 of 3 categories depending on mite densities found on these plants during the summer. T. urticae was found to be highly abundant (category 3) on 26 species, at lower densities on 10 species (category 2), and was rarely or never found on the remaining 12 species (category 1). Dispersal of mites from groundcover plants into trees was found to be highly variable within and between orchards. Within orchard dispersal appeared to be related to the distribution and abundance of category 3 host plants in the orchard. Variability between orchards may also be affected by groundcover management techniques and levels of acaricide resistance in T. urticae. The use of herbicides to control groundcover plants significantly increased the dispersal of T. urticae into the orchard trees.     

Dispersal and gene flow of pesticide resistance traits in phytoseiid and tetranychid mites

Dispersal and gene flow of pesticide resistance traits in phytoseiid and tetranychid mites are discussed relative to their biologies and resistance management. The focus is on deciduous fruit-tree crops whereTyphlodromus pyri Scheuten andMetaseiulus occidentalis (Nesbitt) can effectively control spider mite pests. Oregon populations ofM. occidentalis were more dispersive thanT. pyri, as evidenced by movement to small apple trees placed inside and outside of commercial apple orchards. This difference was corroborated by the spatial distributions of organophosphate resistance in populations from sprayed orchards and nearby unsprayed habitats:T. pyri showed patchy, local patterns of resistance whileM. occidentalis showed more regional, homogeneous trends. Gene flow among populations was estimated from allozymic variation ofT. pyri. Intra- and inter-population genetic variation was high enough to prevent population differentiation. Thus, allozymic estimates of gene flow were higher than that indicated by pesticide resistance patterns.Dispersal inTetranychus urticae Koch is also discussed relative to resistance evolution. Immigration of resistant phenotypes from crops or other sprayed habitats can increase the frequency of resistance. Immigration of susceptible individuals from surrounding unsprayed habitat into a sprayed crop can slow resistance or lead to its reversion, depending on the level of gene flow between populations. Dispersal within crops can have the same effect if susceptibles come from a refuge. In pears, immigration of susceptibleT. urticae from nearby habitat and groundcover aided in reversion of organotin resistance. Experiments on resistance management tactics forT. urticae are discussed.     

Effects of acaricides,pyrethroids and predator distributions on populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> in apple orchards

We sampled mites in three apple orchards in Nova Scotia, Canada, that had been inoculated with pyrethroid-resistant Typhlodromus pyri and had a history of Tetranychus urticae outbreaks. The objective of this study was to monitor populations of T. urticae and phytoseiid predators on the ground and in trees and to track dispersal between the two habitats. Pesticides were the chief cause of differences in mite dynamics between orchards. In two orchards, application of favourably selective acaricides (abamectin, clofentezine) in 2002, coupled with predation by T. pyri in trees and Neoseiulus fallacis in ground cover, decreased high T. urticae counts and suppressed Panonychus ulmi. By 2003 phytoseiids kept the tetranychids at low levels. In a third orchard, application of pyrethroids (cypermethrin, lambda-cyhalothrin), plus an unfavourably selective acaricide (pyridaben) in 2003, suppressed phytoseiids, allowing exponential increases of T. urticae in the ground cover and in tree canopies. By 2004 however, increasing numbers of T. pyri and application of clofentezine strongly reduced densities of T. urticae in tree canopies despite high numbers crawling up from the ground cover. Another influence on T. urticae dynamics was the distribution of the phytoseiids, T. pyri and N. fallacis. When harsh pesticides were avoided, T. pyri were numerous in tree canopies. Conversely, only a few N. fallacis were found there, even when they were present in the ground cover and on tree trunks. Low numbers were sometimes due to pyrethroid applications or to scarcity of prey. Another factor was likely the abundance of T. pyri, which not only competes with N. fallacis, but also feeds on its larvae and nymphs. The scarcity of a specialist predator of spider mites in trees means that control of T. urticae largely depends on T. pyri, a generalist predator that is not particularly effective in regulating T. urticae. The Canadian Crown's right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

The stability of tebufenpyrad resistance in two-spotted spider mite (Acari: Tetranychidae) under laboratory conditions

The successful use of chemical rotations to manage insecticide resistance requires reversion between alternate chemical applications. We tested a tebufenpyrad resistant population of Tetranychus urticae Koch after some 55 months laboratory culture without pesticide selection and found LC₅₀ level resistance had dropped from 63.29- to 2.41-fold. However, the population was still heterogeneous with LC₉₉ level resistance at 38.03-fold. It is likely that a lack of reversion contributed directly to the initial tebufenpyrad control failure. This revised version was published online in August 2006 with corrections to the Cover Date.     

The development of bifenthrin resistance in two-spotted spider mite (Acari: Tetranychidae) from Australian cotton

Bifenthrin (Talstar^®) was registered at the beginning of the 1993/94 season for control of Helicoverpa spp. and Tetranychus urticae in Australian cotton. Resistance was monitored in T. urticae following registration but despite the implementation of resistance management, resistance evolved in the 1996/97 cotton-growing season after only four seasons use. During the following three seasons resistance increased progressively both in level (from 1.2- to 109-fold at LC₅₀) and abundance (from 20 to 90% strains) and was linked to field control failures. The evolution of resistance has now reduced the reliability of bifenthrin for T. urticae control in Australian cotton. The impact of bifenthrin resistance in T. urticae and its continued management in Australian cotton is discussed.     

Mode of inheritance of resistance to three new acaricides in the Kanzawa spider mite Tetranychus kanzawai Kishida (Acari:Tetranychidae)

The genetics of resistance to three new types of acaricide tebufenpyrad, fenpyroximate and pyridaben was studied by crossing a resistant (R) with a susceptible (S) strain of Tetranychus kanzawai Kishida. The resistance ratios calculated from the LC50s of the R and S strains were 97, 1265 and 134 for tebufenpyrad, fenpyroximate and pyridaben, respectively. The responses to the three acaricides in F1 females from reciprocal crosses between the R and S strains showed that the modes of inheritance of resistance to tebufenpyrad, fenpyroximate and pyridaben were intermediate, incompletely dominant and completely recessive, respectively. Furthermore, the responses of F2 females from the reciprocal crosses indicated that the resistance to the three acaricides was under monogenic control.Exp Appl Acarol 22: 699708 © 1998 Kluwer Academic Publishers     

Sensitivity of Venturia inaequalis to Trifloxystrobin and Difenoconazole in Uruguay

The sensitivity of Venturia inaequalis to trifloxystrobin and difenoconazole was studied in Uruguay. Populations of V. inaequalis were collected from apple orchards with different histories of trifloxystrobin use. Sensitivity of populations to trifloxystrobin was analysed using a method for testing spore germination published by FRAC, using a discriminatory concentration of 2.0 mg a.i./l. Resistance to trifloxystrobin was widespread in the region of commercial apple production with resistance detected in all orchards examined, the incidences ranging from 3% to 95%. The highest frequencies were found in orchards with the most intensive use of Quinone outside inhibitors (Q_oI) fungicides. Sensitivities of isolates of V. inaequalis to difenoconazole were assessed at five concentrations using a mycelial growth assay on isolates (33 isolates per orchard) from one non‐commercial (baseline orchard) and two commercial orchards having differing histories of difenoconazole use. Populations in both commercial orchards exhibited reduced sensitivities to difenoconazole compared to the baseline orchard. Resistance factor (RF) values of 6.6 and 11.74 were measured in the orchards with moderate (up to 4 sprays per season) and intensive use (more than 5 sprays per season) of difenoconazole, respectively. A single‐assessment concentration (SAC) was identified for assessing difenoconazole sensitivity of V. inaequalis isolates by fitting linear regressions between log₁₀ EC₅₀ and relative growth (RG) of the isolates at each fungicide concentration testing, and comparing the goodness‐of‐fit of the regression lines. Comparable results were obtained based on EC₅₀ values and RG values at a SAC of 0.05 mg of active ingredient per litre (a.i. per l). Populations from both commercial orchards differed from the baseline population, in that isolates with RG ≥70 were present at substantial levels in the former but absent from the latter.     

A mutation in the PSST homologue of complex I (NADH:ubiquinone oxidoreductase) from Tetranychus urticae is associated with resistance to METI acaricides

The acaricidal compounds pyridaben, tebufenpyrad and fenpyroximate are frequently used in the control of phytophagous mites such as Tetranychus urticae, and are referred to as Mitochondrial Electron Transport Inhibitors, acting at the quinone binding pocket of complex I (METI-I acaricides). Because of their very frequent use, resistance evolved fast more than 20 years ago, and is currently wide-spread. Increased activity of P450 monooxygenases has been often associated with resistance, but target-site based resistance mechanisms were never reported.Here, we report the discovery of a mutation (H92R) in the PSST homologue of complex I in METI-I resistant T. urticae strains. The position of the mutation was studied using the high-resolution crystal structure of Thermus thermophilus, and was located in a stretch of amino acids previously photo-affinity labeled by fenpyroximate. Selection experiments with a strain segregating for the mutant allele, together with marker-assisted back-crossing of the mutation in a susceptible background, confirmed the involvement of the mutation in METI-I resistance. Additionally, an independent genetic mapping approach; QTL analysis identified the genomic region of pyridaben resistance, which included the PSST gene. Last, we used CRISPR-Cas9 genome editing tools to introduce the mutation in the Drosophila PSST homologue.     

Resistance status of the carmine spider mite,Tetranychus cinnabarinus and the twospotted spider mite,Tetranychus urticae to selected acaricides on strawberries

The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year‐round intensive horticultural production region. LC₉₀ of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region.     

Resistance to acaricides in Italian strains of <Emphasis Type="Italic">Tetranychus urticae</Emphasis>: toxicological and enzymatic assays

Problems with Tetranychus urticae are frequently reported in protected crops in Italy, particularly in roses where many introduced acaricides show a progressive loss of effectiveness. We have conducted bioassays to assess the response of some Italian strains of T. urticae to a number of acaricides. These include compounds that were widespread and frequently used in the past, but also some recently registered compounds. We investigated two T. urticae strains collected from rose growers where control failures were reported (SAN and PSE), together with a strain collected from unsprayed vegetables (BOSA). Adult females of the rose strains (SAN and PSE) were resistant to tebufenpyrad (Resistant Ratio—RR, RR₅₀ = 48.4 and 163.6) and fenpyroximate (RR₅₀ = 74.1 and 25.9) when compared to the susceptible BOSA strain. Lethal concentrations for these products were higher than the registered field rate. The PSE strain proved to be highly resistant to abamectin (RR₅₀ = 1,294.1). Variation in bifenazate susceptibility was detected amongst strains, but LC₉₀ values of SAN and PSE were still in the range of the registered field rate. In egg bioassays, the SAN and PSE strains exhibited high resistance levels to clofentezine (RR₅₀ = 66,473 and 170,714), hexythiazox (RR₅₀ = 70,244 and 159,493) and flufenoxuron (RR₅₀ = 61.9 and 117.9). But the recently introduced ovi/larvicides etoxazole and spirodiclofen exhibited high activity on all strains. The activity of detoxifying enzymes such as esterases, glutathione-S-transferases (GSTs) and cytochrome P450 monooxygenases (MFOs) was determined in these strains as a preliminary attempt to identify potential resistance mechanisms. Enzymatic assays showed that the rose strains exhibited 2.66 and 1.95-fold increased MFOs activity compared to the susceptible strain. Assays for GSTs revealed that only the SAN strain exhibited a significantly higher activity. In contrast, only the PSE strain showed a significant higher hydrolysis of 1-naphthyl acetate.     

Comparison of susceptibility of two populations of Tetranychus urticae Koch to two acaricides,abamectin and propargite

The spider mite, Tetranychus urticae Koch is a serious pest of economically important plants in closed and open area worldwide. The spider mite resistance to acaricide plays a major role in the failure of the chemical control method. Thus, the aim of the current study was to evaluate the efficacy of two acaricides, abamectin and propargite, against two populations (strains) of the spider mite. Results showed that LC₅₀s of the abamectin against susceptible and resistant strains of the spider mite were 0.1 and 2730?ppm, respectively. Whilst LC₅₀s of the propargite against susceptible and resistant strains of the spider mite were 55 and 7199?ppm, respectively. Resistance ratio (RR) calculated as the ratio of resistance LC₅₀/susceptible LC₅₀ showed that RR for abamectin and propargite was 20285 and 130, respectively. The enzyme assay results showed that three mechanisms of MFO, GST and EST are involved in the abamectin resistance of the spider mite. In gel assays, when α-naphthyl acetate was used as substrate, three bands appeared in the gel in which bands E2 and E3 were major bands and E1 was a minor band confirming that α-naphthyl acetate was a better substrate for general esterase activity in the spider mite whereas β-acetate when used for esterase activity, only two faint bands (E1 and E2) were observed. The order of their involvement in the abamectin resistance is EST?>?MFO?>?GST.     

Sublethal effects of essential oil of Cinnamomum zeylanicum Blume on life expectancy (ex) and age-specific fertility (mx) of two-spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae)

Two-spotted spider mite, Tetranychus urticae Koch, is one of the most important pests of agricultural products that have a global distribution. Now, the control is dependent on the use of chemical pesticides. The effects of the sublethal concentrations (LC₁₀ and LC₂₅) of the essential oil of Cinnamomum zeylanicum were evaluated on some parameters of the life table of the pest, at the constant temperature of 30?°C, relative humidity of 40?±?5% and photoperiod of 16L: 8D. Our results showed that the essential oil of cinnamon is effective on female adult stage. Lethal concentration at which 50% mortality (LC₅₀) for the essential oils is from C. zeylanicum on female adult mite was 23.39?μl/L air. Sublethal concentrations of the essential oil of C. zeylanicum also impair the natural biology of the mite. Concentrations of sublethal of essential oil decreased age-specific fertility (m_x) of T. urticae compared with the control. Sublethal concentrations (LC₁₀ and LC₂₅) have reduced the life expectancy (e_x) in egg stage. Sublethal effects of the essential oil of C. zeylanicum and its impact on T. urticae management are discussed.     

Resistance to chlorpyriphos in the predatory mite Kampimodromus aberrans

The predatory mite Kampimodromus aberrans (Oudemans) is a key biocontrol agent in vineyards in Italy and Southern Europe. Its susceptibility to common pesticides (e.g., organophosphates) has been considered an important factor in preventing successful biocontrol of phytophagous mites. Nevertheless, populations of K. aberrans apparently resistant to organophosphates (OPs) have been reported to occur in Northern Italian vineyards. The resistance of K. aberrans to fungicides (e.g., mancozeb) has been demonstrated in the laboratory in France, but little is known about the toxicity of insecticides towards K. aberrans. Of these pesticides, the OP chlorpyriphos is extensively used in viticulture to control lepidopterans and homopterans. The present study investigated the dose–response effect of chlorpyriphos in four K. aberrans strains characterized by different levels of exposure to OP insecticides in the past: from never to frequently exposed. Resistance to chlorpyriphos is demonstrated for populations collected from vineyards and apple orchards. Resistance factors exceeded 145,000× for the three strains collected in vineyards and orchard. LC₅₀ values for resistant strains were 1.85–6.83 times higher than the recommended field dose of chlorpyriphos for vineyards and orchards (525 mg a.i./l).     

Effects of B-azolemiteacrylic on life-history traits and demographic parameters of two-spotted spider mite,Tetranychus urticae (Acari: Tetranychidae)

The present study was conducted to evaluate sublethal effects of B-azolemiteacrylic on the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Female adults of T. urticae were exposed to LC₁₀ and LC₃₀ of the acaricide, and the effects on treated females and their offspring were evaluated. The results showed that the fecundity of F₀ female adults treated with LC₁₀ and LC₃₀ of B-azolemiteacrylic was reduced by 30.9 and 39.2%, respectively. Longevity and oviposition period of the females were significantly reduced as well. The developmental duration of egg and deutonymph stage of the F₁ generation were not significantly different from that of the control. The protonymph stage after LC₃₀ treatment lasted significantly longer, whereas the larva, deutonymph and female stage were significantly shorter than the control. The oviposition period of the F₁ generation was significantly shortened, the fecundity of each female decreased significantly, and the ratio of female-to-male was reduced too. Moreover, the average generation period of T. urticae after LC₁₀ and LC₃₀ treatments was shorter than that of the control, and the net production rate (R₀), intrinsic rate of increase (r_m) and finite rate of increase (λ) were all reduced by 33.3, 7.5 and 1.9% (LC₁₀ treatment) and by 51.3, 14.8 and 3.6% (LC₃₀ treatment), respectively. The population doubling time was prolonged by 7.5 and 14.8% after LC₁₀ and LC₃₀ treatments, respectively, compared with the control. These results indicate that B-azolemiteacrylic may effectively inhibit the development rate of the F₀ and F₁ populations of T. urticae, which will help design integrated strategies for the comprehensive control of T. urticae and rational use of pesticides in the field.

     

Sublethal effects of fenpyroximate and pyridaben on two predatory mite species, <Emphasis Type="Italic">Neoseiulus womersleyi</Emphasis> and <Emphasis Type="Italic">Phytoseiulus persimilis</Emphasis> (Acari,Phytoseiidae)

Laboratory bioassays were conducted to evaluate the sublethal effects of fenpyroximate and pyridaben on life-table parameters of two predatory mites species, Neoseiulus (= Amblyseius) womersleyi and Phytoseiulus persimilis. In these assays, young adult females were treated with three sublethal concentrations of each acaricide. The life-table parameters were calculated at each acaricide concentration, and compared using bootstrap procedures. For each acaricide, the LC₅₀ estimates for both species were similar, yet the two species exhibited completely different susceptibility when the population growth rate was used as the endpoint. Exposure to both acaricides reduced the net reproduction rate (R _o ) in a concentration-dependent manner and their EC₅₀s were equivalent to less than LC₇. Two different scales of population-level endpoints were estimated to compare the total effect between the species and treatments: the first endpoint values were based on the net reproductive rate (fecundity λ) and the second endpoint values incorporated the mean egg hatchability into the net reproductive rate (vitality λ). The fecundity λ decreased in a concentration-dependent manner for both acaricide treatments, but the vitality λ decreased abruptly after treatment of N. womersleyi with pyridaben. The change in the patterns of λ revealed that the acaricide effects at the population level strongly depended on the life-history characteristics of the predatory mite species and the chemical mode of action. When the total effects of the two acaricides on N. womersleyi and P. persimilis were considered, fenpyroximate was found to be the most compatible acaricide for the augmentative release of N. womersleyi after treatment.     

Sublethal effects of fenpyroximate on life table parameters of the predatory mite <Emphasis Type="Italic">Phytoseius plumifer</Emphasis>

Knowledge of the lethal and sublethal effects of pesticides on biological control agents is necessary for successful implementation of integrated pest management programs. The sublethal effect of acaricide fenpyroximate (Ortus^®) on performance of females and their offspring of Phytoseius plumifer (Canestrini &; Fanzago), an efficient predator of Tetranychus urticae Koch, was determined under laboratory conditions. The adult predators were exposed to the residues of the acaricide on fig leaves and the LC₅₀ value was determined based on a concentration–response analysis. The results showed that sublethal concentrations of fenpyroximate significantly affected the fecundity and longevity of the treated females of P. plumifer. Reproductive and life table parameters of the subsequent generation were also affected by sublethal concentrations. It could be concluded that sublethal concentrations can significantly reduce the population growth of P. plumifer and this should be considered in integrated pest management programs.