Rop plays conserved roles in the reproductive and digestive processes of spider mites

Ras opposite(Rop)is known to play an essential role in regulating vesicle trafficking,including synaptic transmission and general secretion.The fundamental roles of Rop have been confirmed by the observation that null mutations in many organisms generate lethal phenotypes during embryogenesis.However,the effects of Rop during the postembryonic stages,especially in non-model organisms,remain largely unknown.Here,we provide new data that enhance our understanding of Rop's roles in the adults of multiple species of Tetranychus spider mites(Acari:Tetranychidae),a class of notorious agricultural pests.Our in silico and experimental evidence demonstrated that Rop is under purifying selection and is highly conserved in Tetranychus spp.RNA interference experiments showed that Rop is required for maintaining normal fecundity but has no significant effect on survival.We further demonstrate that knockdown of Rop darkens the body color of spider mites and blocks the excretion of fecal pellets,which is likely to be related to an abnormality in the excretion of food waste in the digestive system.Overall,our findings clarify novel functions of a vesicle trafficking-related gene in the adult stage of multiple Tetranychus species and highlight the need to evaluate the roles of essential genes in various organisms.

Research on recognition for cotton spider mites’damage level based on deep learning

The changes in cotton leaf characteristics are closely related to the cotton spider mites’damage level.Extracting the distinguishable features of cotton leaves is an effective method to identify the level.However,it faces enormous challenges for the classification due to various factors,such as illumination intensity,background complexity,shooting angle and so on.A recognition model is proposed,which is trained through transfer learning with the two-stage learning rate from 0.01 to 0.001 based on MobileNetV1.The experiments demonstrate that the deep learning model attains the accuracy of 92.29%for the training set and 91.88%for the test set of the mixed data.For testifying the effectiveness of the two-stage training method,the models are trained with the two public datasets,CIFAR-10 and Flowers,and attain the accuracy of 95.46%and 95.57%for the test sets,respectively.The average recognition time for a single cotton leaf image is about 0.015 s.Furthermore,the mobile terminal application is developed with the model embedded,to realize the real-time recognition for cotton spider mites’damage level in the field.

Lack of fitness cost and inheritance of resistance to abamectin based on the establishment of a near-isogenic strain of Tetranychus urticae

Many populations of the two-spotted spider mite, Tetranychus urticae Koch, have developed high levels of resistance to the pesticide abamectin in China and other countries. This study developed a near-isogenic line to understand better the inheritance, cross-resistance, and fitness costs associated with abamectin resistance in the field population of T. urticae in China. We introduced the trait that confers extremely high abamectin resistance in a field-collected population of T. urticae into a susceptible laboratory strain(IPP-SS) to generate an abamectin-resistant near-isogenic line(NIL-Aba).This process was carried out through multiple backcrossing to IPP-SS and via parthenogenesis and abamectin screening. Compared with IPP-SS, the NIL-Aba strain had a 25 147-fold resistance to abamectin and a high level of cross-resistance to bifenthrin(288.17-fold), an intermediate level to emamectin benzoate(42.57-fold), and low levels to bifenazate, chlorfenapyr, cyflumetofen, cyenopyrafen, and cyetpyrafen with resistance ranging from 3.18-to 9.31-fold.But it had no cross-resistance to profenofos. The resistance to abamectin in NIL-Aba was autosomal, incompletely dominant, and polygenic. Based on two sex life table parameters, no fitness cost was found in NIL-Aba. Establishing the NIL-Aba strain provides a reliable basis for an in-depth study of abamectin resistance in T. urticae. New information on toxicological characteristics and fitness cost should facilitate the management of abamectin resistance in field populations of T. urticae.

The Influence of Tetranychus urticae Koch (Acari: Tetranychidae) Life Table and Reproductive Parameters by Applying Si on Bean at Library Condition

Two-spotted spider mite, Tetranychus urticae Koch, is one of the important pests of bean, which can cause severe damages on it. Silicon is one of the micronutrient elements, as its spray on the leaves can decrease the population of the pest. In this research, the impact of four different doses of Si (0, 1, 1/5, 2 ppm) was investigated on biological and population growth parameters of T. urticae. The experiments were carried out in Petri dishes in an incubator at 25°C ± 2°C, 65% ± 5% RH and 16 L: 8 D. The duration of developmental stage was significantly affected by Si dose. The longest immature period, the shortest longevity of females and the shortest oviposition period were obtained at 2 ppm. In addition, Si dose significantly affected population growth parameters of the mite. The intrinsic rate of natural increase (rm) of the mite ranged from 0.246 to 0.215 day which lowest and the highest values were at 2 ppm and control plants, respectively. The lowest net reproductive rate (R0) and finite rate of increase (λ) of the mite and the highest value of mean generation time (T) and doubling time (DT) were estimated at 2 ppm. The results of this peruse represented that 2 ppm had better potential for decreasing the population of the two-spotted spider mite, and it can be used in the mite integrated pest management programs.

Ethanol Extraction of Hyoscyamus niger and Hypericum calycinum Evaluated for Acaricidal Activity against Tetranychus urticae Koch （Acari： Tetranychidae）

Hyoscyamus niger L. （Solanaceae） and Hypericum calycinum L. （Hypericaceae） were collected from two provinces Bursa and Ankara in Turkey during flowering stages. Extracts obtained from H. niger and H. calycinum were tested against two-spotted mite as an acaricidal pesticide. Bioassay experiments were carried out under laboratory conditions using two different methods namely, leaf disc dipping and direct leaf spraying. Two-spotted mite was reared in insectary using Phaseolus vulgaris L. （Fabaceae）. In the leaf dipping method, H. niger extract resulted in an effective adjusted mortality for larvae of 87.13% and for adults of 81.66%. For H. calycinum the adjusted mortality for larvae and adults was 77.77% and 85.97% respectively at the highest concentration. In larval stage, LCs0 values were 5.47 w/v and 3.32 w/v dipping and spraying method respectively. In addition, adult stage, it was determined that LCs0 values were 1.17 w/v and 3.56 w/v in both methods. For leaf spraying method. H. niger resulted in an adjusted showed an effect against larvae and adults mortality rate was 95% and 91% respectively. However, H. calycinum mortality percentage was 80% and 87% at 12% concentration, with LC50 values of 9.62 w/v and 2.13 w/v in dipping method. In this research apart from mortality effects on egg, reproduction was also investigated. Each concentration showed that treated females laid less eggs compared to the untreated females.

Acaricidal Activity of Extracts of Juglans regia L. on Tetranychus urticae Koch （Acari： Tetranychidae）

Two-spotted spider mite （Tetranychus urticae Koch） （Acari： Tetranychidae） is a very serious pest worldwide, causing considerable damage to vegetables, flowers and fruit crops. The application of plant extracts to control insects can be an effective alternative. In this study, the efficacy of an extract from Juglans regia L. （Juglandecaea） was tested as an alternative to conventional acaricides. Using two different methods, bioassays were used to determine the effects of varying concentrations J. regia （1%, 3%, 6%, 12%） of the extracts. Experiments were carried out using 3 cm diameter leaf disks of Phaseolus vulgaris L. In addition, the effects of the extract on mite reproduction and oviposition were investigated. As a result, in the leaf dipping method, the 12% concentration of the extract caused the highest mortality of nymph （90%） and adult （83.00%） stages. For the spraying method, the mortality of adults at the same concentration was 100%. In bioassays at lower concentrations, the adult mites laid lower numbers of eggs in comparison to the untreated mites. The highest effect occurred at concentration of 12% and the lowest effect was at 1%. The extract was no observed ovicidal effect.

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 inten- sive 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. LC90s 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. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respec- tive 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.

The microbiota in spider mite feces potentially reflects intestinal bacterial communities in the host

Microorganisms prov ide many physiological functions to herbivorous hosts.Spider mites(genus Tetranychus)are important agricultural pests throughout the world;however,the composition of the spider mite microbial community,especially gut micro-biome,remains unclear.Here,we investigated the bacterial community in five spider mite species and their associated feces by deep sequencing of the 16S rRNA gene.The composi-tion of the bacterial community was significantly different among the five prevalent spider mite species,and some bacterial symbionts showed host-species specificity.Moreover,the abundance of the bacterial community in spider mite feces was significantly higher than that in the corresponding spider mite samples.However,Flavobacterium was detected in all samples,and represent a"core microbiome".Remarkably,the maternally inherited endosymbiont Wolbachia was detected in both spider mite and feces.Overall,these results offer insight into the complex community of symbionts in spider mites,and give a new direction for future studies.

Comparative life table analysis of Tetranychus urticae （Acari Tetranychidae） on 14 soybean genotypes

The life table parameters of two-spotted spider mite （TSSM）, Tetranychus urticae Koch, on 14 soybean genotypes （Sari, Sahar, Tellar, Zane, Ks3494, LI7, Dpx, 032, 033, Clark, Hill, 127, Tms and Williams） were evaluated at 28 ±1℃, 65% ± 5% RH and a photoperiod of 16 ： 8 h L ： D. The survivorship data （lx） of adult females were fitted to the Weibull frequency distribution model in all genotypes tested. Based on the Weibull parameters, the survival curve was type I on all genotypes, which indicated that the mortality mostly occurred in old individuals. Furthermore, two mathematical models （Analytis and Enkegaard） were fitted to age-specific fecundity data （mx）. The highest intrinsic rate of increase （rm） was recorded on L17 （0.392） and the lowest values of this parameter were obtained on Tms （0.233）, Hill （0.236）, 032 （0.236）, 127 （0.237） and Clark （0.240）. In addition, net reproductive rate （R0） and finite rate of increase （λ） of the TSSM had the highest value on L17 as 45.521 and 1.475, respectively. The lowest values of these parameters were recorded on Tms as 12.149 and 1.258, respectively. Doubling time （DT） varied significantly on different genotypes and the shortest and longest values of this period were obtained on L17 and 032, respectively. Our findings revealed that Tms, Hill, 032, 127 and Clark were less suitable genotypes, suggesting that they are more resistant to the TSSM than the other genotypes.