Influence of abiotic factors on diapause termination and temperature requirements for postdiapause development in the European red mite, Panonychus ulmi (Acari: Tetranychidae).

The European red mite Panonychus ulmi (Koch) is widely distributed and it can severely affect pome fruit crops, particularly apple. Pest outbreaks are related to an overuse of non-selective pesticide treatments that lead to the development of resistance and the absence of natural enemies in the orchard. A key aspect to optimize the use of pesticide treatments in the context of IPM is to increase the knowledge on the biology and ecology of the pest to better predict population dynamics and outbreaks. For the European red mite, knowledge on the conditions that lead to diapause breaking by winter eggs is essential to model population dynamics. To increase this knowledge, winter eggs were collected during field surveys in northen Spain during three years and egg hatching was monitored under controlled temperature and photoperiod conditions in the laboratory. The "number of days exposed to cold temperatures" was the most significant factor that positively affected hatching of overwintering eggs. The time required for 50% of the egg population to hatch (T50%) was also negatively modulated by the duration of exposure to cold temperature. The temperature threshold for postdiapause eggs development collected from the field was estimated between 5 and 6 ºC in 2005 and 2007, respectively. Moreover, the degree-days required for post diapause development were estimated between 263.2 and 270.3, depending on the year of collection. Collectively, we provide additional information on the diapause termination and postdiapause development of the European red mite that may effectively contribute to optimize pest population models.

Molecular insight into the endophytic growth of Beauveria bassiana within Phaseolus vulgaris in the presence or absence of Tetranychus urticae.

Entomopathogenic fungi are an important factor in the natural regulation of arthropod populations. Moreover, some can exist as an endophyte in many plant species and establish a mutualistic relationship. In this study, we have investigated the endophytic growth of Beauveria bassiana within different tissues of Phaseolus vulgaris in the presence and absence of Tetranuychus urticae. After the colonization of the B. bassiana within the internal tissues of P. vulgaris. The susceptibility of T. urticae appeared to depend on the life stage where high, moderate, and low mortalities were recorded among adults, nymphs, and eggs, respectively. In addition, this study provided, for the first time, molecular insight into the endophytic growth of B. bassiana by analyzing the expression of several genes involved in the development of the entomopathogenic fungi at 0-, 2-, and 7- days post-inoculation. B. bassiana displayed preferential tissue colonization within P. vulgaris that can be put into the following order based on the detection rate: leaf > stem > root. After analyzing the development-implicated genes (degrading enzymes, sugar transporter, hydrophobins, cell wall synthesis, secondary metabolites, stress management), the most remarkable finding is the detection of behavioral change between parasitic and endophytic Beauveria during post-penetration events. This study elucidates the tri-trophic interaction between fungus-plant-herbivore.

Transcriptome of Tetranychus urticae embryos reveals insights into Wolbachia-induced cytoplasmic incompatibility.

The endosymbiont Wolbachia is known for manipulating host reproduction in selfish ways. However, the molecular mechanisms have not yet been investigated in embryos. Here, we found that Wolbachia had no effect on the number of deposited eggs in Tetranychus urticae Koch (Acari: Tetranychidae) but caused two types of reproductive manipulation: killing uninfected female embryos via cytoplasmic incompatibility (CI) and increasing the hatching ratio of infected female embryos. RNA sequencing analyses showed that 145 genes were differentially expressed between Wolbachia-infected (WI) and Wolbachia-uninfected (WU) embryos. Wolbachia infection down-regulated messenger RNA (mRNA) expression of glutathione S-transferase that could buffer oxidative stress. In addition, 1613 and 294 genes were identified as CI-specific up-/down-regulated genes. Compared to WU and WI embryos, embryos of CI cross strongly expressed genes involved in transcription, translation, tissue morphogenesis, DNA damage and mRNA surveillance. In contrast, most of the genes associated with energy production and metabolism were down-regulated in the CI embryos compared to the WU and WI embryos, which provides some clues as to the cause of death of CI embryos. These results identify several genes that could be candidates for explaining Wolbachia-induced CI. Our data form a basis to help elucidate the molecular consequences of CI in embryos.

Preparation of Matrinic/Oxymatrinic Amide Derivatives as Insecticidal/Acaricidal Agents and Study on the Mechanisms of Action against Tetranychus cinnabarinus.

In continuation of our program to develop natural-product-based pesticidal candidates, matrinic/oxymatrinic amides were obtained through structural optimization of matrine. N'-(4-Fluoro)phenyl-N-(4-bromo)phenylsulfonyloxymatrinic amide (IIm) showed potent insecticidal activity against Mythimna separata. N-(Un)substituted phenylsulfonylmatrinic acids (3a-c) exhibited promising acaricidal activity against Tetranychus cinnabarinus. By qRT-PCR analysis of nAChR subunits and AChE genes and determination of AChE activity of (un)treated T. cinnabarinus, it suggested that the open lactam ring of matrine and carboxyl group and (4-methyl)phenylsulfonyl of N-(4-methyl)phenylsulfonylmatrinic acid (3b) were necessary for action with α2, α4, α5, and ß3 nAChR subunits; compound 3b was an inhibitor of AChE in T. cinnabarinus, and AChE was one possible target of action in T. cinnabarinus against 3b; and compound 3b may be an antagonist of nAChR and AChE in T. cinnabarinus.

Development, lifespan and reproduction of spider mites exposed to predator-induced stress across generations.

Predator-induced stress shows pronounced effects on prey by inducing behavioural, morphological, and physiological responses. Increasing evidence shows that these antipredator responses may also lead to changes in life-history traits such as aging and lifespan. However, little is known about how predator cues influence the fitness of preys and their transgenerational effects. Parental spider mites (Tetranychus urticae) were either raised on a leaf disc with or without cues from a natural predator (Phytoseiulus persimilis). The results showed that predator cues prolonged the development of both sexes, shortened female adult lifespan but not that of males, and reduced lifetime reproductive outputs of the females. The studies with offspring from both cues-exposed and control mothers demonstrated that parental effects were significant in the early developmental stage of offspring, but not in later life stages. The lifespan of offspring was strongly negatively affected by the predator-induced stress when they were directly exposed but not the stress-experienced by their mothers. Additionally, the parental effects in the earlier life stage were sex-specific, with delayed hatching in daughters (but not sons) when parents were exposed to predator-induced stress. This cross-transgenerational study indicated that there were deleterious effects of predator-induced stress on aging and lifespan of prey for both parents and their offspring, although the parental effects appeared to be weak (in the early stage of offspring but diminished in adult stage). This study highlighted the sex-difference of prey in response to predator-induced stress and sex-dependent parental effects on the offspring.

Seasonal occurrence and development of three closely related Oligonychus species (Acari: Tetranychidae) and their associated natural enemies on fagaceous trees.

We compared the life cycles and diapause attributes among three closely related spider mites, Oligonychus castaneae on Castanea crenata, and O. gotohi and O. amiensis on Lithocarpus edulis. The lower thermal thresholds from egg to egg were 10.5, 8.5 and 8.9 °C, respectively, and the thermal constants were 177.8, 229.5 and 232.5 degree-days, respectively. The cumulative hatching rates of diapause eggs of O. castaneae and O. gotohi increased as the season progressed in and after early-to-mid January, which indicates diapause termination. In contrast, O. amiensis showed higher hatching rates in December and January, but hatchability gradually decreased in and after February because some of the eggs died from the cold. Oligonychus castaneae and O. gotohi females produced diapause eggs in response to the short photoperiod in late September to early October and in early-to-late October, respectively, which corresponded to the times predicted by the critical photoperiods (at 15 °C) of 12 h 15 min and 11 h 15 min for the respective species. Oligonychus castaneae showed at least a single population peak over the 3-year observation period, but the time of peak population varied from mid-July to mid-September. The population of O. gotohi was higher between November and May when diapause eggs were present on host plants in early winter and the first-generation females laid eggs on leaves in spring. The population of O. amiensis, which is a non-diapause species, was only high between September and December, because eggs were laid on leaves in autumn to winter and then gradually disappeared and/or died during winter. Natural enemies were observed as the number of spider mites declined, and the density suppression effect by natural enemies was confirmed in the field.

RNAi targeting ecdysone receptor blocks the larva to adult development of Tetranychus cinnabarinus.

RNA interference (RNAi) is a potentially useful pest control method because of its high specificity. Silencing the expression of important RNAi target genes of pests will block important biological processes and reduce pest damage. Ecdysone is a unique arthropod hormone and the ecdysone receptor (EcR) is a key factor in molting pathway. We investigated the possibility that dsRNA targeting of the EcR of Tetranychus cinnabarinus (TcEcR) could effectively block development from larvae to adults. The mRNA level of TcEcR was highest in the larva stage, and 73.1% of the mites failed to survive the larva stage when TcEcR expression was silenced. Only 11.7% of T. cinnabarinus ingesting dsRNA successfully developed into adults, while 86.7% in the control succeeded in molting across each stage. RNAi significantly increased the developmental intervals of T. cinnabarinus. Under the effects of dsRNA, development times for the larva and first nymph doubled. Phenotype of body size change and death were observed during the development of T. cinnabarinus ingesting dsRNA. These findings suggest that RNAi is a potential means for the control of T. cinnabarinus. Genes in hormone pathways such as EcR are possible RNAi targets.

Production of winter eggs in Schizotetranychus brevisetosus (Acari: Tetranychidae) inhabiting evergreen Japanese blue oak.

The overwintering pattern of parasitic herbivorous arthropods is closely related to host phenology, because defoliation imposes strong selection pressures on various developmental stages. This relationship has been well studied in populations of spider mites (Acari: Tetranychidae) on deciduous hosts, but is little studied in populations on evergreen hosts, probably because their leaves are always available. However, spring defoliation may also influence the life cycle. We studied the overwintering pattern of Schizotetranychus brevisetosus (Acari: Tetranychidae), a specialist on evergreen oak, Quercus glauca, in Kochi, Japan. Only adult females and their eggs (winter eggs) survived the coldest months. We also observed a conspicuous seasonal change in egg colour and size: December winter eggs were 1.7× larger than September summer eggs, suggesting the winter eggs are diapausing. Adult females produced summer eggs until November and winter eggs from late November until they disappeared in March. The winter eggs hatched in early March. The immature stages developed in mid- to late March, when 39% of old leaves fell, some of which carried hundreds of immature individuals. Therefore, even in evergreen hosts, defoliation places potentially strong selection pressure on the immature stages. Despite this, S. brevisetosus appears not to change its egg hatching season to avoid the defoliation season, so it may have evolved a behavioural adaptation to escape falling leaves. The existence of several species with similar lifestyles suggests the importance of host phenology and predation pressure for evolution of the overwintering pattern.

Expression dynamics of key ecdysteroid and juvenile hormone biosynthesis genes imply a coordinated regulation pattern in the molting process of a spider mite, Tetranychus urticae.

In insects, the ecdysteroid 20-hydroxyecdysone coordinates with juvenile hormone (JH) to regulate the process of molting, development and metamorphosis; however, this interaction is still unclear in the mites. In this study, we investigated the gene related to ecdysteroid and JH biosynthesis pathways, including four ecdysteroid and 11 JH biosynthesis genes. We examined their expression patterns during molting of different developmental stages of the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), an important agricultural pest that feeds on more than 1100 plant species. The expression of ecdysteroid biosynthesis Halloween genes exhibited a positive zigzag-like pattern, with a peak after 8 h of molting and a drop 8 h after entering each quiescent stage. In contrast, JH biosynthesis genes expression displayed a negative zigzag-like pattern, with a peak at 8 h after entering each quiescent stage and a drop after 8 h of each molting. These opposite patterns imply that ecdysteroid and JH expression is coordinated during the developmental transition. Our data provide an initial perspective on the co-expression of ecdysteroid and JH biosynthesis genes to regulate this important developmental process in the two-spotted spider mite.

Peanut cultivars display susceptibility by triggering outbreaks of Tetranychus ogmophallos (Acari: Tetranychidae).

The peanut red spider mite, Tetranychus ogmophallos Ferreira and Flechtmann (Acari: Tetranychidae), is an important pest of peanut in Brazil and is considered a quarantine pest in other countries. This study investigates the development, reproduction, survival and life table parameters of T. ogmophallos on five peanut cultivars-three with high levels of oleic acid [high oleic] and recently released: Granoleico, IAC OL 3 and IAC 503; and two regular and previously used by farmers: Runner IAC 886, IAC Tatu ST 3-and two breeding lines (L. 8008 and L. 322) in the growth chamber. There were differences between the developmental times of all immature stages, the oviposition period, fecundity and adult longevity of T. ogmophallos reared on the peanut cultivars and breeding lines. The longest duration of the immature stage and lowest fecundity occurred on cultivars Granoleico and Runner IAC 886, and breeding line L. 322, which also displayed the lowest intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) and the shortest mean generation time (T). The highest fitness occurred on the IAC Tatu ST, IAC OL 3, IAC 503 and L. 8008. Our study shows that peanut cultivars belonging to the group with high oleic trait and recently released (IAC OL 3 and IAC 503) are susceptible to T. ogmophallos, except Granoleico, which is resistant. The regular and previously used cultivar Runner IAC 886 and breeding line L. 322 are resistant to the peanut red spider mite.

Population performance of Tetranychus evansi (Acari: Tetranychidae) on African tomato varieties and wild tomato genotypes.

The tomato red spider mite, Tetranychus evansi Baker & Pritchard, is one of the main pests of the tomato crop in several countries, mainly in Africa, where it can reduce tomato yield by up to 90%. The biotic potential of this mite is high and its control is difficult because of low efficiency of chemicals used and the rapid development of resistance to acaricides. We used the two-sex life table to evaluate the effect of two wild tomato genotypes (PI134417 and PI134418) and five tomato varieties widely grown in Benin (Kekefo, Akikon, TLCV15, Tounvi, and TOML4) on demographic characteristics of T. evansi under laboratory conditions. Tetranychus evansi did not develop on the genotypes PI134417 and PI134418, indicating their resistance to this mite. Developmental time of immature stages and female longevity were significantly higher on TLCV15 and Kekefo. Fecundity, net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) of T. evansi on the African varieties were not statistically different among varieties. Generation time (T) was shorter on TOML4 than on TLCV15 and Tounvi. Thus, efforts should be made to prospect varieties with resistance characteristics or to develop other control means, to reduce the use of pesticides to control T. evansi in Africa.

Synthesis and Acaricidal- and Insecticidal-Activity Evaluation of Novel Oxazolines Containing Sulfiliminyl Moieties and Their Derivatives.

Sulfimides and sulfoximines are highly relevant for medicinal chemistry and crop protection, as the resulting products can reveal interesting bioactivities. Herein, we report the design and synthesis of a series of novel 2,4-diphenyl-1,3-oxazolines containing sulfiliminyl and sulfoximinyl moieties. The acaricidal and insecticidal activities of the new compounds were evaluated and indicated that these compounds exhibited excellent acaricidal activities against spider mite larvae and eggs. The LC50 values of 6a-7, 6b-3, 6b-4, 6c-2, and 6c-4 against spider mite larvae were about 4 to 6 times lower than that of the commercial insecticide etoxazole (0.0221 mg L-1), and the LC50 value of 6a-4 against spider mite eggs was 0.0006 mg L-1, which was 10 times lower than that of etoxazole (0.0063 mg L-1). At the same time, most of the compounds showed insecticidal activity though their structure-activity relationships that were different. Oxazolines containing an N-cyano sulfiliminyl moiety at the para position of the 4-phenyl group exhibited better insecticidal activities against cotton bollworm and corn borer than etoxazole, whereas the compounds containing groups derived from sulfiliminyl and sulfoximinyl had weak insecticidal activities. This research again proved that the substituent type at the para site of the 4-phenyl moiety has a decisive role on the biological activity and insecticidal spectrum.

Spraying pyrethroid and neonicotinoid insecticides can induce outbreaks of Panonychus citri (Trombidiformes: Tetranychidae) in citrus groves.

Panonychus citri (McGregor) (Trombidiformes: Tetranychidae) is one of the main defoliator mites in citrus groves. In Brazil, P. citri was formerly considered a secondary pest, but in recent years, the population levels of this mite have increased in many groves, requiring additional acaricide applications for its control. The population growth of P. citri is associated with the increase in the number of applications of pyrethroid and neonicotinoid insecticides to control insect citrus pests. This study assessed the effects of pyrethroid (deltamethrin, esfenvalerate, λ-cyhalothrin) and neonicotinoid (imidacloprid and thiamethoxam) insecticides on biological, behavioral and demographic parameters of P. citri. None of the insecticides tested affected larval hatching, but deltamethrin, esfenvalerate, and λ-cyhalothrin reduced the survival of larvae and protonymphs. Deltamethrin, esfenvalerate, and λ-cyhalothrin induced a significant increase in the fecundity of surviving females. Pyrethroids also caused repellency and changed feeding and oviposition preferences. In contrast, imidacloprid and thiamethoxam did not affect the survival of immature stages, but imidacloprid significantly increased fecundity. Imidacloprid and thiamethoxam did not cause any repellent effect or changes in the feeding and oviposition preferences. Based on the demographic parameters, deltamethrin, λ-cyhalothrin, and imidacloprid increased Ro, r, and λ, whereas esfenvalerate and thiamethoxam were similar to the control. Therefore, the use of these insecticides (especially deltamethrin, λ-cyhalothrin, and imidacloprid) requires caution, such as avoiding repeated use of these compounds during the periods of P. citri incidence in citrus groves.

Preference and performance of the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae) on strawberry cultivars.

The two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most serious pests of strawberry worldwide. Understanding the preference of TSSM for particular cultivars of strawberry and performance on them helps identify host-plant resistance to this pest mite. In this study, we tested preference, developmental duration, fecundity and population levels of TSSM on 14 strawberry cultivars. TSSM showed strong preference for the Chinese cultivars of Yanxiang, Baixuegongzhu, and Jingtaoxiang. Development of TSSM on the cultivars varied from 32.32 to 36.82 days; it was longest on the cultivars Hongxiutianxiang and Baixuegongzhu, and shortest on Yanxiang, Jingzangxiang, and Darselect as well as on a wild variety (Wuye). TSSM had high fecundity on the cultivars Yanxiang, Taoxun, Hongxiutianxiang, Jingzangxiang, Albion and Baixuegongzhu as well as on Wuye, whereas egg production was lowest on Sweet Charlie, Portola, Akihime, and Benihoppe. After 28 days of plant infestation with 10 pairs of adults, the cultivars Yanxiang, Taoxun, Jingzangxiang, Jingtaoxiang, and Baixuegongzhu had the highest number of mites (> 1000 per plant), whereas mite numbers on Albion and Camarosa were low. The population size of TSSM was correlated with fecundity, but no correlation was found between other preference/performance measures. Our study suggests that a rapid increase of population size of TSSM on cultivars of strawberry is related to high fecundity, and also that there are substantial differences in preference and performance across cultivars.

Acaricidal Activity of Cyclodipeptides from Bacillus amyloliquefaciens W1 against Tetranychus urticae.

Bioassay-guided fractionation of the supernatant of the biocontrol strain Bacillus amyloliquefaciens W1 led to the isolation of eight acaricidal cyclodipeptides from the active fractions by column chromatography separation and HPLC purification. The chemical structures of these compounds were identified as cyclo-(Gly-l-Phe), 2, cyclo-(l-Phe- trans-4-OH-l-Pro), 3, cyclo-(Gly-l-Tyr), 4, cyclo-(l-Ala-l-Pro), 5, cyclo-(l-Pro- trans-4-OH-l-Pro), 6, cyclo-(Gly-l-Pro), 7, cyclo-(l-Pro-l-Pro), 8, and cyclo-(l-Tyr- trans-4-OH-l-Pro), 9. Those cyclodipeptides displayed significant acaricidal activities with LC50 values of 13.85-98.24 µM. Cyclo-(l-Tyr- trans-4-OH-l-Pro) (LC50 13.85 µM) was five times more effective than the positive control abamectin (LC50 72.06 µM). The results indicated that the hydroxyl group is an important component. This is the first report on the acaricidal capabilities of cyclodipeptides against Tetranychus urticae. The results revealed that the acaricidal activity of the biocontrol strain B. amyloliquefaciens W1 was dependent on its constituent cyclodipeptides, which have the potential to be safe and environmentally friendly acaricides.

Demographic Comparison of the Tetranychus urticae Koch. (Acari: Tetranychidae) Reared on Different Cultivars of Strawberry.

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest of strawberry (Fragaria × ananassa Duch.) grown in greenhouses and outdoors. In this study, we evaluated the resistance status of five common strawberry cultivars ('Aromas', 'Kurdistan', 'Missionary', 'Paros', and 'Queen Elisa') under laboratory conditions. The developmental times of the preadult and adult stages, total longevity, reproduction, and life table parameters were analyzed according to the age-stage, two-sex life table theory, which provides the most comprehensive description on the survival, stage differentiation, and reproduction of a population. Preadult development was the shortest on Kurdistan and longest on Aromas (17.70 d vs. 21.00 d). The greatest number of oviposition days occurred on Missionary (28.65 d), whereas the fewest were on Queen Elisa (21.58 d). The intrinsic rate of natural increase (r) and finite rate of increase (λ) varied among the cultivars. The highest values were found on Kurdistan (r = 0.1436d-1, λ=1.1544d-1), while the lowest values were on the Aromas cultivar (r = 0.1081d-1, λ=1.1141d-1). The longest mean generation time (T) of T. urticae occurred on Aromas. Based on the results of the present study, the cultivar Aromas was considered the most resistant to T. urticae and least favored strawberry cultivar for the development and reproduction of the mite. Demographic data of twospotted spider mite on these five strawberry cultivars can be used to improve our understanding of the population dynamics of the pest and thereby develop effective pest management strategies against T. urticae in both integrated and organic strawberry production.

Encapsulation of Satureja hortensis L. (Lamiaceae) in chitosan/TPP nanoparticles with enhanced acaricide activity against Tetranychus urticae Koch (Acari: Tetranychidae).

The objective of this study was the fabrication of encapsulated Satureja hortensis essential oil (S.EO) in chitosan/tripolyphosphate nanoparticles (CS/TPP-NPs) via ionic gelation technique and investigation of its acaricidal effect. A high encapsulation efficiency of 96.17% was obtained, which shows successful encapsulation of EOs in CS-TPP nanoparticles. Transmission electron microscopy (TEM) analysis proved the formation of spherical S. hortensis EO-loaded chitosan nanoparticles (S.EO@NPs). Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated the presence of encapsulated S.EO in CS/TPP nanoparticles. The average size of nanoparticles was found to be 192.1 ±â€¯11 nm using dynamic light scattering (DLS) technique. Moreover, durability and fumigant acaricide activity of S.EO@NPs against Tetranychus urticae Koch were investigated. The obtained results demonstrated that there were considerable differences between pure S. hortensis EO and S.EO@NPs in their ovicidal, adulticidal, and persistence activities against T. urticae. The LC50 values of pure EO and as-prepared S.EO@NPs against adult mite were 4.95, 46.98 µL/L after 24 h exposure and 2.02, 31.30 µL/L after 72 h exposure, respectively. Fumigation exposure for 24 and 72 h showed that the sensitivity of adults T. urticae were more than the eggs of T. urticae. The LC50 values of fumigant toxicity of pure S.EO and S.EO@NPs against eggs of T. urticae were measured after 24 and 72 h. The experimental results for 24 h treatment showed 6.71 and 211.66 µL/L air LC50 values for pure S.EO and S.EO@NPs, respectively. In the case of 72 h exposure, The LC50 values of pure S.EO and S.EO@NPs were 4.15 and 107.38 µL/L air, respectively. A sustained release of S.EO from S.EO@NPs was observed during 25 days of the study, indicating the persistence acaricide activity for a long time. The as-prepared S.EO@NPs and pure S.EO illustrated 67% and 2% mortality at 18th day exposure, respectively. The notable increasing of the residual fumigant toxicity may be related to the slow and sustainable release of the active ingredient of EO. Based on this study, the S.EO@NPs showed significantly residual adulticidal activity against adults of T. urticae. S.EO@NPs would be recommended as an alternative for pure EOs and other common acaricides.

Suitability of Pollen from Different Plant Species as Alternative Food Sources for Neoseiulus californicus (Acari: Phytoseiidae) in Comparison with a Natural Prey.

Alternative foods such as pollen may help predators to maintain their populations even when their prey is scarce or absent. In order to develop an appropriate spider mite management strategy using Neoseiulus californicus McGregor and optimize laboratory rearing, its biological parameters on four types of pollen (cedar, pistachio, pear, and apricot) were determined and compared on Tetranychus urticae Koch. Our results indicated that the developmental times of females and males varied from 6.06 to 7.32, and 6.00 to 7.15 d, respectively. The highest fecundity was obtained on pistachio pollen, followed by apricot pollen and T. urticae. Feeding on cedar pollen caused the lowest fecundity. In contrast to T. urticae and pistachio pollen, which resulted in the highest intrinsic and finite rates of increase, feeding on cedar pollen produced the lowest value. Pistachio and apricot pollen appear to have the highest nutritional value. From an ecological perspective, in the presence of pistachio pollen, a more rapid population increase of N. californicus could be expected, when the prey is scarce or absent in greenhouses or fields. This may provide valuable information for the design of a comprehensive program for conservation and/or mass production of N. californicus to control T. urticae and other pests.

Novel Temperature-Dependent Development Rate Models for Postdiapause Egg Eclosion of Three Important Arthropod Pests Found in Commercial Christmas Tree Plantations of Southern Québec, Canada.

The balsam twig aphid Mindarus abietinus Koch (Hemiptera: Aphididae), the spruce spider mite Oligonychus ununguis (Jacobi) (Acari: Tetranychidae), and the pine needle scale Chionaspis pinifoliae (Fitch) (Hemiptera: Diaspididae) are three important pests for the Christmas tree industry of Québec, Canada. Temperature-dependent development rates for postdiapause overwintering eggs of these species have never been studied for populations of southern Québec, where the vast majority of Christmas trees are grown. The accumulation of physiological time in growing degree days (GDD) is a standard tool to predict egg eclosion dates for pests, when first generation immatures are most vulnerable to insecticidal control. Development rates for postdiapause eggs were tested at four or five constant temperatures in the 11-23°C range under controlled conditions, based on time before hatching for eggs collected in a balsam fir plantation in late winter. The standard linear model and three published nonlinear models were fitted to the data and compared for their ability to estimate key biological temperature parameters and to predict development rates of postdiapause eggs. Validation of model predictions of egg eclosion time on balsam fir in the field was reasonably accurate using the classical linear model where field-accumulated GDD were calculated with a particular interpretation of the average method based on daily maximum and minimum temperatures. The linear model could predict mean egg eclosion within around 5 d of eclosion dates observed in the field.

Intercropping With Fruit Trees Increases Population Abundance and Alters Species Composition of Spider Mites on Cotton.

With the recent increase in planting of fruit trees in southern Xinjiang, the intercropping of fruit trees and cotton has been widely adopted. From 2014 to 2016, a large-scale study was conducted in Aksu, an important agricultural area in southern Xinjiang, to compare the abundance and species composition of spider mites in cotton fields under jujube-cotton, apple-cotton, and cotton monocrop systems. The abundance of spider mites in cotton fields under both intercropping systems was generally higher than in the cotton monocrop. The species composition of spider mites also differed greatly between cotton intercropped with apple or jujube compared to the cotton monocrop. The relative proportion of Tetranychus truncates Ehara (Acari: Tetranychidae) in the species complex generally increased while that of another spider mite, Tetranychus dunhuangensis Wang (Acari: Tetranychidae), decreased under fruit tree-cotton systems. More attention should be paid to the monitoring and management of spider mites, especially T. truncates in this important region of China.