Persimilis Populations Research Articles

Molecular variation of the cytochrome b DNA and protein sequences in Phytoseiulus macropilis and P. persimilis (Acari: Phytoseiidae) reflect population differentiation.

Several phytoseiid mite species are important natural enemies used in biological control strategies. In the present study, Cytb mtDNA sequences of various populations of two species, Phytoseiulus macropolis and P. persimilis, were compared to determine whether the specimens collected in Brazil could belong to P. persimilis as this latter species is reported in South America but not in Brazil. The Cytb marker was used because of its high evolution rate, assumed to capture intraspecific variation. No overlap between intra- and interspecific distances was observed but the distances were quite low for interspecific variation. This can be due to the particular biology of Phytoseiulus species and this shows the difficulty to apply a universal threshold in genetic distances to conclude about the existence of one or several species. Cytb mtDNA sequences were also considered to assess intraspecific variation. The DNA sequences of P. persimilis populations were very similar, probably because they all originated from the West Palearctic region or because of a prevalence of commercialized specimens in natura. For P. macropilis, higher genetic distances were observed and differentiation was noted according to geographic location and, to a smaller extent, pyrethroid resistance. To determine how DNA variation might impact the protein function (CytB fragment considered), the amino acid compositions of the populations studied were compared. No diagnostic mutation was observed between pyrethroid resistant and susceptible populations, whereas four mutations were identified between populations of P. macropilis separated by 1300km (different climatic conditions). The impact of such mutations is discussed but knowledge is scarce, which makes it difficult to root testable hypotheses. The protein analysis clearly opens new perspectives in Phytoseiidae studies.

Not all predators are equal: miticide non-target effects and differential selectivity.

Biological control in conventional agroecosystems involves the integration of chemical and conservation tactics, requiring knowledge of pesticide non-target effects on key natural enemies. Even for natural enemy groups such as predatory mites (Acari: Phytoseiidae), where pesticide non-target effects have been thoroughly examined, there may be significant differences in species susceptibility to specific active ingredients, including newer selective products. Using bioassays, we examined lethal (female mortality) and sublethal (fecundity, egg hatch, larval survival) effects of ten miticides on a spider mite pest (Tetranychus urticae) and three insectary-purchased predatory mites (Phytoseiulus persimilis, Neoseiulus californicus, and N. fallacis) commonly used for its management. Susceptibility of field-collected and insectary-reared populations of P. persimilis was also compared. Cumulative impacts on production of larvae by treated female spider mites and predators were compared to create a metric that simultaneously accounted for miticide efficacy and selectivity. Bifenthrin was the least selective, as it caused acute toxicity to all predators and had little efficacy against T. urticae. Hexythiazox and cyflumetofen were the most selectively favorable. Phytoseiulus persimilis populations were similar in which miticides they were sensitive to, although the insectary-purchased population was generally more sensitive. All products, including those considered selective (cyflumetofen, bifenazate, acequinocyl) had non-target effects on at least one species of predator tested. This work emphasizes that there is high variability in selectivity among species, highlighting the need to examine key natural enemies individually when creating management programs. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Effects of Insecticides and Fungicides Commonly Used in Tomato Production on Phytoseiulus persimilis (Acari: Phtyoseiidae).

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest of tomatoes in North Carolina. Resident populations of the predatory mite Phytoseiulus persimilis have recently been detected on field-grown tomatoes in central North Carolina, and potentially can be a useful biological control agent against T. urticae Laboratory bioassays were used to assess lethal and reproductive effects of 10 insecticides and five fungicides commonly used in commercial tomato production (chlorantraniliprole, spinetoram, permethrin, imidacloprid, dimethoate, dinotefuran, thiamethoxam, bifenthrin, fenpropathrin, lambda-cyhalothrin, azoxystrobin, chlorothalonil, boscalid, cyazofamid, and mancozeb) on P. persimilis adult females and eggs. Insecticides were tested using concentrations equivalent to 1×, 0.5×, and 0.1× of the recommended field rates. Fungicides were tested at the 1× rate only. Dimethoate strongly impacted P. persimilis with high adult mortality, reduced fecundity, and reduced hatch of eggs laid by treated adults, particularly at high concentrations. The pyrethroids lambda-cyhalothrin, bifenthrin, and fenpropathrin were associated with repellency and reproductive effects at high concentrations. Bifenthrin additionally caused increased mortality at high concentrations. Chlorantraniliprole, dinotefuran, and permethrin did not significantly affect mortality or reproduction. Imidacloprid significantly reduced fecundity and egg viability, but was not lethal to adult P. persimilis Thiamethoxam negatively impacted fecundity at the 1× rate. There were no negative effects associated with fungicide exposure with the exception of mancozeb, which impacted fecundity. Field trials were conducted to explore the in vivo impacts of screened insecticides on P. persimilis populations in the field. Field trials supported the incompatibility of dimethoate with P. persimilis populations.

Interaction Between Beneficial Organisms in Control of Spider Mite Tetranychus Urticae (Koch.)

Strict regulations limiting the availability of synthetic pesticides on vegetable crops in greenhouses have created a new challenge for plant protection. Many pests such as whiteflies, thrips aphids, spider mites, and other, still remain dangerous and difficult to control on vegetable crops in greenhouses. In the experience of many and in a review of world literature, it has been noted that effective methods of biological control of many pests are already available, or can be easily adapted for practice. According to the Polish Directives, biological methods should be used prior to any application of chemical products. Thus, biological control is a priority in plant protection, especially for vegetable crops in greenhouses. Tetranychus urticae is the most important pest in greenhouse crops. Successful control of this pest is very difficult. In laboratory studies the predator mites Amblyseius swirskii and Phytoseiulus persimilis showed a high efficacy when used together to control of two-spotted spider mites (86% mortality). When predators were used separately they were less effective against the pest (about 63% mortality). The studies showed that A. swirskii was competitive with P. persimilis populations for controlling the two-spotted spider mite. Other predators mites: Amblyseius degenerans and Amblyseius californicus used in the experiments demonstrated neutral interaction.

Species‐specific RFLP pattern in the Heat Shock Protein26 gene (Hsp26): a single‐locus tool for species identification and experimental testing of habitat‐induced isolation in the New World Artemia species

The brine shrimp Artemia (Crustacea, Branchiopoda), a paradigmatic inhabitant of hypersaline lakes, has molecular features to survive under stressful conditions, such as the p26 heat shock protein. We report the RFLP fingerprinting pattern (four restriction enzymes) of a 217 bp fragment of exon2 of the Hsp26 gene in six Artemia franciscana and four Artemia persimilis populations, the most genetically divergent Artemia species co-occurring in latitudinal extremes of Chile. The species-specific RFLP pattern observed is a simple and cost-effective single-locus tool for species delimitation and experimental testing the habitat-induced isolation barrier between them.

Pattern of female reproductive age classes in mass-reared populations of Phytoseiulus persimilis (Acari: Phytoseiidae) and its influence on population characteristics and quality of predators following cold storage

We exposed mass-produced Phytoseiulus persimilis to 5 °C or 10 °C for 0, 6, 12 or 18 days to determine the influence of cold on the fecundity and longevity of individual predators, on their dispersal and survival patterns following storage, and on the reproductive age structure in populations of females. When P. persimilis populations were tested shortly after harvest the distribution of reproductive age classes was consistently biased towards older and non-producing females, with overall average fecundity of ∼13 eggs and longevity ∼7 days. The number of live predators gradually declined as the length of storage increased at either 5 °C or 10 °C. In contrast, the capability of predators to disperse upward was only reduced after 18 days of storage at 5 °C. The proportion of reproductively young females increased in populations that survived 18 days of storage at either 5 °C or 10 °C, and this was reflected in significantly higher mean oviposition period and fecundity than in the remaining three treatments. Our results reveal that the ability of P. persimilis females to tolerate cold storage and starvation is strongly tied to their reproductive age and that reproductively young females are capable of tolerating prolonged exposure to low temperature and starvation without compromising their quality. Fecundity of P. persimilis assessed shortly after harvest met the expectations outlined in IOBC guidelines. We found a positive linear relationship between the directly measured total fecundity and the results of a short-term (5-day) IOBC fecundity test, indicating that the IOBC test reliably predicts the reproductive potential of P. persimilis females. However, the proportion of surviving predators did not meet IOBC guidelines.

Genetic characterization of Argentinean Artemia species with different fatty acid profiles

The Anostracan genus Artemia is composed by several sibling species reproductively isolated, but identical or very similar in outward appearance. The genus shows also an underlying striking variability from the biochemical point of view, regarding especially the fatty acid profile of the cysts and nauplii. In Argentina, Artemia is represented by two bisexual species: A. franciscana and A. persimilis. Former studies have shown that A. franciscana is present in northern of 36º and that A. persimilis is constrained southwards of 37° S. In general, there is good agreement between morphological and cytogenetic comparisons of Argentinean populations with respect to species discrimination. However, new Argentinean Artemia populations are being analyzed morphologically and it becomes necessary to further investigate if the genetic adscription of these populations is congruent with the results obtained from the current morphological analyses. Restriction fragment length polymorphism (RFLP) analysis of a fragment of the 16S rRNA mitochondrial gene was used to investigate the genetic diversity and population structure of 10 new Artemia populations from Argentina. The mitochondrial DNA (mtDNA) results showed a similar pattern to that of previous cytogenetic and morphological analyses with the two Argentinean species appearing as highly divergent. The presence of A. persimilis in southern Argentina and the southernmost Chilean population was confirmed unveiling a novel picture of species distribution in the country. A. franciscana showed a unique haplotype. Populations of A. persimilis appeared highly structured, although their clustering did not follow a clear geographic pattern. The different Argentinean Artemia populations analyzed were characterized by high variability in their fatty acids, showing both marine- and freshwater-type profiles. For the first time, the investigation of the relatedness between the fatty acid composition in Artemia and genetic markers was attempted. The study aimed at the putative association of molecular markers with marine versus freshwater-type populations. A lack of correlation between RFLP patterns at mtDNA and the fatty acid (FA) profiles was found in the A. persimilis populations which was discussed from the point of view of two main genetic hypotheses and/or phenotypic plasticity.

소형포장에서 친환경농자재가 천적곤충에 미치는 영향

시설재배지 내에서의 친환경농자재는 작물보호를 위하여 사용하기도 하고 작물의 생육을 도와주는 역할을 위해 사용되기도 한다. 친환경농자재는 각종 해충을 방제하기 위하여 사용되는 천적들과 중복 사용될 수도 있다. 이때 친환경농자재가 이러한 천적들에 미칠 수 있는 영향을 평가하였다. 본 실험에 사용된 친환경농자재는 천적곤충에 영향을 많이 주는 것으로 보고된 10개를 선발하여 소형포장과 농가포장에서 평가하였다. 먼저 무당벌레 유충에 미치는 영향을 보면, 친환경농자재를 사용하지 않은 무처리구에서는 무당벌레의 목화진딧물 포식활동이 잘 이루어지고 있지만, EFAMMo L과 EFAMPE D, EFAMME G, EFAMAE A등을 처리한 구에서는 무당벌레의 포식활동이 이루어지지 않아서 진딧물의 개체수가 현저히 증가함을 알 수 있다. 온실가루이좀벌의 경우에, 친환경농자재를 살포한 시험구에서는 전체적으로 온실가루이 약충과 온실가루이좀벌 머미의 개체수가 조금씩 감소하였으며, 특히 IEFAM C, FEFAM D, EFAMSM B, EFAMPE D 등을 처리한 시험구에서 온실가루이좀벌 머미의 수가 무처리구에 비하여 현저히 적은 것을 알 수 있었다 반면에 EFAMMo C를 살포한 처리구의 경우에는 온실가루이를 거의 찾아볼 수 없을 정도로 온실가루이에 대하여 방제효과를 나타내고 있었다. 소포장에서 콜레마니진디 벌의 기생률을 검토한 결과 친환경농자재를 뿌린 구역보다는 무처리구에서의 기생률이 높았다. IEFAM C, FEFAM D, EFAMPE D, EFAMMo L 등을 살포한 구역에서 특히 낮은 기생률을 나타내었다. 잎굴파리좀 벌의 외부기생 머미가 방사 후 1주일 후부터 2주 후까지도 많이 관찰되었지만 처리구와 무처리구 사이의 통계적인 유의성은 없었다. FAMMo C는 점박이응애, 칠레이리응애 모두 개체수를 감소시켰다. EFAMMo L은 점박이응애에는 피해를 주지 않은 반면에, 칠레이리응애의 개체수는 많이 감소하였다. Many kinds of environment friendly agricultural materials (EFAMs) were used for the plant protection, furthermore they support the growth of crops in the greenhouses and the kindly environment friendly farming. Natural enemies might be used for control of insect pest with EFAMs at the same space and time. For testing the toxicity of EFAMs against to natural enemies, 10 EFAMs were selected and tested in small greenhouses and farm's fields. In case of Harmonia axyridis larva, there was no predacious activity against cotton aphids in the block with EFAMMo L, EFAMPE D, EFAMME G and EFAMAE A, otherwise, aphid population was rapidly decreased in the control block without EFAMs. Both of Trialeurodes vaporariorum and Encarsia formosa population were slightly decreased in the block with EFAMs. There were significantly decreased in the block with IEFAM C, FEFAM D, EFAMSM Band EFAMPE D compared with control area. Especially, there was significantly maintained a very low population, both T. vaporariorum and E. formosa in the block with EFAMMo C. The parasitized ratio of Aphidius colemani is also very low in the block with EFAMs compared with control area. In the block with IEFAM C, FEFAM D, EFAMPE D and EFAMMo L, there were significantly different with control area in the number of mummies. Otherwise, in case of Diglyphus isaea and Liriomyza trifolii, there was no significantly different between blocks with and without EFAMs. In the block with EFAMMo C, Tetranychus urticae and Phytoseiulus persimilis populations were significantly maintained a very low level. However, the population of T. urticae was increased, but P. persimilis was decreased in the block with EFAMMo L.

PCR-based identification of the pathogenic bacterium, Acaricomes phytoseiuli, in the biological control agent Phytoseiulus persimilis (Acari: Phytoseiidae)

The predatory mite, Phytoseiulus persimilis is an important biological control agent of herbivorous spider mites. This species is also intensively used in the study of tritrophic effects of plant volatiles in interactions involving plants, herbivores, and their natural enemies. Recently, a novel pathogenic bacterium, Acaricomes phytoseiuli, has been isolated from adult P. persimilis females. This pathogen causes a characteristic disease syndrome with dramatic changes in longevity, fecundity, and behavior. Healthy P. persimilis use spider mite-induced volatiles to locate prey patches. Infection with A. phytoseiuli strongly reduces the attraction to herbivore-induced plant volatiles. The loss of response to herbivore-induced plant volatiles along with the other disease symptoms can have a serious impact on the success of biological control of spider mites. In this study, we have developed a molecular tool (PCR) to detect the pathogenic bacterium in individual predatory mites. PCR primers specific for A. phytoseiuli were developed based on 16S ribosomal DNA of the bacterium. The PCR test was validated with DNA extracted from predatory mites that had been exposed to A. phytoseiuli. A survey on different P. persimilis populations as well as other predatory mite species from several companies that rear predatory mites for biological control revealed that the disease is widespread in Europe and is restricted to P. persimilis. The possibility that the predatory mites get infected via their prey Tetranychus urticae could be eliminated since the PCR test run on prey gave a negative result.

Diversity of the fatty acid composition of Artemia spp. cysts from Argentinean populations

Nauplii of the branchiopod crustacean Artemia spp. are widely used as live food in aquaculture. Their nutritional value depends essentially on the fatty acid profile of their lipids, which can be very variable. Study of this variability (often species- and/or ecology-related) proposes inter- esting theoretical and applied questions. In the present study, cysts (dehydrated dormant eggs) from Argentinean Artemia spp. populations were analysed for their fatty acid profile. Most of the cyst samples analysed (n = 16) were obtained from Artemia persimilis populations, but 3 belonged to A. franciscana. Previous research indicated that A. persimilis populations are confined to inland biotopes, but in this study we report the presence of A. persimilis populations in coastal ecosystems. Cysts from all populations exhibited fatty acid profiles typical of either marine or freshwater, irrespective of the inland or coastal origin of their biotope. This study represents the first time that a significant amount of eicosapentaenoic acid (EPA, 20:5n-3) was detected in A. persimilis cyst sam- ples. We hypothesize on some factors that presumably influence the fatty acid profiles of Artemia spp. cysts: (1) food resources from different habitats, which in turn can be influenced by environmental parameters, (2) the genetic make-up of each population, and/or (3) mechanisms of selective feeding.

Population dynamics of naturally occurring Phytoseiulus persimilis (Acari: Phytoseiidae) colonising beans (Phaseolus vulgaris cv. Sari) infested by spider mites, Tetranychus cinnabarinus (Acari: Tetranychidae), in Turkey

Population dynamics of the naturally occurring phytoseiid Phytoseiulus persimilis Athias-Henriot was studied in relation to Tetranychus cinnabarinus Boisduval in five unsprayed bean plots of 250 m2 (10 by 25 m) during 1994 and 1995 in Samandag province of Hatay, Turkey. T. cinnabarinus remained active throughout winter reproducing on a range of ground-cover plants. P. persimilis was generally encountered as gravid females in a non-diapausing phase in debris during winter. Population growth had begun by April on T. cinnabarinus-infested weeds such as Malva neglecta Wallr., Solanum melongena L., and S. nigrum L. In 1994, T. cinnabarinus reached peaks with 15.20±2.40, 11.67±1.70, 22.15±4.06, 25.51±4.43 and 19.0±2.39 total stages/cm2 leaf area, from June 28 through July 21 in Fidanli 1, 2, 3, Karacay and Kusalani, respectively (Mean±SE). In the same year, the highest average densities of P. persimilis were 0.89±0.26, 1.59±0.39, 0.81±0.13, 0.43±0.16, and 0.33±0.12/cm2 leaf area on July 12 through August 4, respectively. In 1995, peaks of both prey and predator were lower than in 1994 in all plots except T. cinnabarinus in Fidanli 2. The highest average densities of T. cinnabarinus were 11.68±1.69, 14.73±1.65, 13.95±1.98, 0.97±0.25 and 11.59±1.81 total stages/cm2 leaf area in Fidanli 1, 2, 3, Karacay and Kusalani, respectively in 1995 with peaks occurring between July 6 and 27. Thesedensities were 0.22±0.06, 0.33±0.06, 0.07±003, 0.01±0.02 and, 0.41±0.09 total stages/cm2 leaf for P. persimilis on July 6 through 27 in the above mentioned plots, respectively. Throughout the experiments moderate T. cinnabarinus damage was seen on bean leaves before P. persimilis populations peaked, then the visible damage by pest on host plant diminished due to elimination of the pest by the predator and new leaf formation in both years.

Biological control in protected strawberry in northern Italy

Biological control is currently being used in 100 ha of tunnel-grown strawberry in northern Italy. Second-instar larvae of Chrysoperla carnea are released (18 larvae per m2) against aphids when more than 30% of leaflets are infested. Releases of Phytoseiulus persimilis (4–6 predatory mites per m2) are also being used in IPM strategies against Tetranychus urticae; wild P. persimilis populations also occur in the test area, which is near the Adriatic coast. Releases of predators are also successful in the field.

Integrated control ofTetranychus urticaewithPhytoseiulus persimilisandStethorus bifidusin commercial raspberry gardens

Abstract Two-spotted mite (TSM) (Tetranychus urticae Koch) control was studied in commercial raspberry gardens in Nelson and Hastings. In both regions, the predators, Phytoseiulus persimilis Athias-Henriot and Stethorus bifidus Kapur, were found regularly on foliage samples in association with TSM. In Hastings, both predators showed a clear numerical response to TSM and populations of all three species increased and declined cyclically. The cycles were not always in phase among the different cultivars of raspberry. S. bifidus was an important predator when P. persimilis populations were low and unevenly distributed through the property especially in spring. P. persimilis controlled TSM in 6–8 weeks in a favourable pesticide environment and, on one cultivar in the Hastings property, no miticides were needed during a 2-year period. When chemicals toxic to P. persimilis were used (e.g., benomyl and methomyl), TSM increased to potentially damaging levels although no quantitative assessment of damage was made. S. bifidus was killed by organophosphate and carbamate insecticides, but TSM was controlled by P. persimilis when carbaryl, azinphos-methyl, and Bacillus thuringiensis were used against pests and when iprodione and captan were used against fungal diseases.

INFLUENCE OF TEMPERATURE ON THE REPRODUCTIVE POTENTIAL OF TWO MITE PREDATORS OF THE TWO-SPOTTED SPIDER MITE

AbstractOviposition of the predacious mites Phytoseiulus persimilis and Typhlodromus fallacis began 2 days after mating, reached a peak in 1 week, and then declined irregularly. The rates of oviposition were higher, and the oviposition period shorter at 26° than at 20°C. P. persimilis laid 47% more eggs than T. fallacis. The generation time for both species was very dependent on temperature. Minimum values of 112 hours for P. persimilis and 127 hours for T. fallacis were obtained at 28°.Calculations of potential predator populations from the generation time, age-specific fecundity, and proportion of females were made on a daily basis for successive generations. The potential number of living females derived from one mated pair increased logarithmically after a few cycles representing new generations. The rate of increase of P. persimilis populations was 26% higher than that of T. fallacis, and in both species the rate at 26° was about double the rate at 20°.