Acaricidal effect of the antimicrobial metabolite xenocoumacin 1 on spider mite control

The two-spotted spider mite,Tetranychus urticae Koch,is one of the most harmful pests in many agroecosystems worldwide.To effectively manage this pest,there is an urgent need to develop novel bio-active acaricides that support integrated pest management strategies targeting T.urticae.In this study,we explored the acaricidal effects of xenocoumacin 1 (Xcn1) on T.urticae and its predator Neoseiulus californicus using the highly puri?ed compound.Xcn1 was extracted and purified from the cell-free supernatant of the Xenorhabdus nematophila CB6 mutant constructed by the easy promoter activated compound identi?cation (easyPACId) method.When the concentration of Xcn1 exceeded 100μg mL~(–1),the survival rate of spider mite adults declined to below 40%and the fecundity was decreased by 80%at six days post-application.At concentrations of 25 and 50μg mL~(–1),Xcn1 signi?cantly impeded spider mite development by inhibiting the molt.However,neither concentration had any adverse effects on the survival or reproduction of the predatory mite N.californicus.The results from laboratory and semi-?eld experiments consistently demonstrated the effectiveness of the antimicrobial metabolite Xcn1 in controlling pest mites at both the molecular and physiological levels.Our study offers a promising possibility that combines the compatible biocontrol agents of Xcn1 and predatory mites for integrated pest mite control.

Selectivity of Three Miticides to Spider Mite Predator,Phytoseius plumifer(Acari:Phytoseiidae) Under Laboratory Conditions

The predatory mite, Phytoseius plumifer （Canestrini ＆ Fanzago）, is one of the most abundant natural enemies and efficient predator of phytophagous mites in Iran. The miticides hexythiazox （Nisorun, EC 10%）, fenpyroximate （Ortus, SC 5%）, and abamectin （Vertimec, EC 1.8%） were tested in the laboratory for their side effects on P. plumifer. The miticides were applied at the highest field recommended concentration （N） to detached leaves using a Potter Tower to deposit 2 mg spray solution per cm2. Percent predator mortality was evaluated from the protonymph up to the adult stage including the first five days of the oviposition period. Analysis of data showed that the total effect values of hexythiazox were below the lower threshold, and thus it could be considered to be a harmless miticide to P. plumifer. In contrast, the total effects of fenpyroximate and abamectin were found harmful to the predatory mite at the highest field recommended concentrations.

Morphological characteristics of Neoseiulus setarius Ma,Meng&Fan,sp.nov.(Acari:Phytoseiidae)from China

The genus Neoseiulus Hughes,1948 is one of the largest genera in Phytoseiidae and contains more than 364 valid species in the world.In this paper,a new species N.setarius Ma,Meng&Fan,sp.nov.is described based on both adult female and male specimens collected from Setaria viridis(L.)Beauv.(Gramineae),in Inner Mongolia of China.The adult females of the new species are characterized by having a fully reticulated dorsal shield,barbed Z5,bellshaped spermathecal calyx with a short basal stalk.Furthermore,seta R1 is off dorsal idiosomal shield in adult males.

Refinement of Methodology for Cadmium Determination in Soil Micro-Arthropod Tissues

Highly precise and reliable determination of heavy metals in soil micro-arthropod tissues remains a challenge because of the small size of the animals and their typical low abundance in metal-contaminated agricultural soils. The present study sought to develop a method for cadmium （Cd） determination in soil micro-arthropods by optimizing the sample digestion procedure, reducing sample weight, modifying sample pre-treatment and validating the methodology with field samples. The optimized digestion conditions comprised a sample mass of 50-150 μg, digestion reagent of nitric acid：hydrogen peroxide （3：1）, digestion temperature of 105 ℃, digestion period of 3 h and digestion volume of 30 μL. Defecation of the standard Collembola Folsomia candida （92 h） and the indigenous Collembola Onychiurus yodai （42 h） and ultrasonic cleaning of F. candida increased the accuracy of Cd determination. The recovery of Cd using the refined procedure was 98.9% and the limits of detection and quantification were 0.002 and 0.008 μg L-1, respectively. The within-batch precision values were 〈 3%. The Cd concentrations in the tissues of the Collembola Isotorna sp. collected from a range of metal-contaminated fields determined by the improved method were consistent with the Cd concentrations in the field soils. The results indicate that the optimized method can be used for more accurate or reliable determination of Cd concentrations in soil micro-arthropod tissues.

Belowground Tritrophic Food Chain Modulates Soil Respiration in Grasslands

Edaphic biota significantly affects several essential ecological functions such as C-storage, nutrient turnover, and productivity.However, it is not completely understood how belowground animal contribution to these functions changes in grasslands subject to different land use types. A microcosm experiment was carried out to test the effect of a tritrophic food chain on CO_2 release from grassland soils. Soil was collected from three differently managed grassland systems(meadow, pasture, and mown pasture) located in three distinct German regions that cover a north-south gradient of approximately 500 km. The tritrophic food chain comprised natural edaphic microflora, nematodes, and predatory gamasid mites. The experimental design involved a full factorial combination of the presence and absence of nematodes and gamasid mites. Nematodes significantly increased the CO_2 emissions in most treatments,but the extent of this effect varied with land use type. The fact that grazing by nematodes stimulated the metabolic activity of the edaphic microflora over a wide range of grassland soils highlighted the critical impact of the microfauna on ecosystem services associated with soil organic matter dynamics. Gamasids slightly amplified the effect of nematodes on microbial metabolic activity,but only in the pastures. This effect was most probably due to the control of nematode abundance. The fact that gamasid addition also augmented the impact of environmental conditions on nematode-induced modulation of soil respiration highlighted the need for including land use differences while evaluating soil fauna contribution to soil processes. To conclude, the differential response of the investigated tritrophic food chain to different grassland management systems suggests that adverse effects of land use intensification on important soil processes such as atmospheric C-release could potentially be reduced by using management methods that preserve essential features of the belowground food web.