Infectivity of Steinernema mushtaqi (Rhabditida: Steinernematidae) against insect pests and their mass production

The infectivity of entomopathogenic nematode (EPN), Steinernema mushtaqi was tested against legume pod borer, Maruca vitrata, tobacco caterpillar, Spodoptera litura, blue butterfly, Lampides boeticus, red hairy caterpillar, Amsacta moorei, brown bug, Clavigralla gibbosa, mealy bug, Centrococcus somatics, fruit borer, Earias vittella and green bug, Nezara viridula larvae and in vivo mass production of the above-tested species of EPN have been carried out during 2008. S. mushtaqi was found to be more pathogenic to A. moorei, as it brought about 100% mortality within 48 h, than to S. litura, L. boeticus, N. viriduala and E. vittella, as mortality occurred within 72 h; whereas this level of mortality was recorded in C. somatis, C. gibbosa and M. vitrata within 144 h. No mortality was observed in the control treatment. Multiplication of S. mushtaqi and the yield of infective juveniles (IJs) on these insects was the highest (0.94 × 10⁵ IJs/cadaver) from N. viriduala, followed by S. litura (0.76 × 10⁵ IJs/cadaver), L. boeticus as also C. gibbosa (0.31 × 10⁵ IJs/cadaver) and M. vitrata (0.20 × 10⁵ IJs/cadaver). Very poor populations of IJs were found from A. moorei (0.15 × 10⁵ IJs/cadaver) and C. somatics (0.01 × 10⁵ IJs/cadaver). No multiplication of IJs was found from the cadaver of E. vittella. This opens a new hope of utilising S. mushtaqi in the insect pests management programme.     

The reproduction potentials of four entomopathogenic nematode strains related to cost-effective production for biological control

Bioassays to evaluate the mortality, virulence and reproduction potentials of four indigenous EPN strains, S-PQ16, S-BM12, H-KT3987 and H-CB3452 on insect larvae of mealworm (Tenebrio molitor) and greater wax moth (Galleria mellonella) revealed the highest mortality rates of two insect larvae at the highest inoculation dose of 100 IJs to range from 89 to 100 percent and 94.3–100 percent at 48 h after inoculation, respectively. Virulence was high for all nematode strains, with LC₅₀ values between 29.6 and 47.3 IJs/insect host. The highest IJ yields were different between nematode strains and insect host, from 66.8 × 10³ IJs (S-PQ16) to 118.6 × 10³ IJs (H-KT3987) on T. molitor, and from 54.2 × 10³ IJs (S-BM12) to 163.3 × 10³ IJs (H-KT3987) on G. mellonella. The culturing cost in terms of food expenditure for rearing insect larvae varied between insect larvae and nematode strains, from 6.76 to 26.63 USD per billion IJs for nematode strains cultured on T. molitor larvae and from 3.54 to 7.81 USD per billion IJs for nematode strains cultured on G. mellonella larvae. The full cost for a nematode product of 2.5 × 10⁹ IJs per hectare, produced through in vivo mass culturing, of the most efficient nematode strain, H-KT3987, was 191.3 USD, slightly cheaper than 199.4 USD for the same nematode product produced through in vitro mass culturing.     

Ecological aspects of an isolate of Steinernema diaprepesi (Rhabditida: Steinernematidae) from Argentina

Ecological aspects of Steinernema diaprepesi isolate SRC were studied to evaluate the species potential as biological control agent of insect pests. Under laboratory conditions, the following aspects were determined: the nematode life cycle, pathogenicity to several arthropods, reproductive capacity, tolerance to desiccation, effect of temperature on survival and infectivity of infective juveniles (IJs), and influence of soil texture and soil water potential on the isolate. The parasitic cycle on last-instar larvae of Galleria mellonella at 25°C was completed 8 days after infection. The nematode showed high virulence to lepidopteran larvae, being limited or nil in the remaining orders of arthropods evaluated. An acceptable offspring production of S. diaprepesi was confirmed in the species G. mellonella and S. frugiperda, suggesting that the isolate would have potential for control of lepidopteran larvae. Optimum temperature for reproduction was 20–25°C. IJs survived exposure to a range of temperatures between 10 and 40°C, with a significant reduction in the number of live IJs at 40°C. The nematodes remained infective at 20–40°C. IJ mortality was 100% on day 6 of exposure to 85% RH. The movement of IJs observed in the soil column experiments revealed that the isolate uses a cruiser-type search strategy. Soil texture and water potential significantly influenced IJ movement, search and penetration of G. mellonella larvae. The efficacy of this isolate was found to be favoured in sandy soils, regardless of the soil water potential.     

Effects of abiotic factors on the osmotic response of alginate-formulated entomopathogenic nematode,Heterorhabditis bacteriophora (Nematoda: Rhabditida)

Limited shelf life of entomopathogenic nematodes severely restricts their use in biological control programs. In a series of experiments, the dehydration and rehydration response of Heterorhabditis bacteriophora infective juveniles (IJs) was investigated under a range of glycerol concentrations, temperatures and incubation periods. Based on the outcome of these initial studies, nematodes dehydrated using the optimal process were formulated in alginate granules to understand how these nematodes would undergo survival formulation in a model carrier. The highest rate of osmotically arrested IJs occurred in the 22% glycerol solution (98.06%). IJ recovery was considerably improved when dehydration was processed at 10% glycerol solution and 15°C. By trapping IJs in calcium alginate, depending on the adjuvants, the survival rate of IJs differed significantly. IJ state (dehydrated or non-dehydrated) and the addition of formaldehyde had a profound effect on IJ viability, though the severity of the effect varied was dependent on whether the IJs were alginate formulated. Among different formulations, the highest viability (84.18%) was observed where dehydrated IJs were formulated in alginate granules containing formaldehyde. The results showed that the concentration of osmotic solution not only determines the percentage of dehydrated IJs but also affect their subsequent recovery in an aqueous environment. Overall, the results indicate that the shelf life of formulated IJs is significantly affected by combination effects of a broad range of factors. Then understanding the interactive mode of actions of involved factors in formulation play a critical role in developing and introducing more efficient formulations.     

Development of emulsion from rhizobial fermented starch industry wastewater for application as Medicago sativa seed coat

Starch industry wastewater was efficiently employed for the production of Sinorhizobium meliloti and the concentrated culture was used for the development of a biofertilizer formulation. Tween‐80 (0.02 g/L) acted as the best emulsifier for a Sinorhizobium–canola oil emulsion. The stability of the emulsion and survival of the organism was enhanced by supplementation of xanthan gum at pH 8. The refrigerated condition was most favorable for stability and survival of the microorganism. The survival of microorganism at 4±1°C was 2.78×10¹⁰ and 2.01×10¹⁰ CFU (colony forming unit)/mL on storage for 1 and 2 months, respectively. The values were higher than the prescribed cell count (×10³ CFU/mL) for field application. At 40°C, the survival of bacteria reduced from 3×10¹⁰ CFU/mL to 8.1×10⁹ and 8.8×10⁶ CFU/mL in 1 and 2 months, respectively. Emulsion‐coated seed was incubated at different temperatures and a cell count of 10⁵ CFU/seed was observed after 2 months of storage at 4°C, which was equal to the highest level of the described requirement (10³–10⁵ CFU/seed). Emulsion supplemented with xanthan gum improved the shelf‐life under optimized conditions (Sinorhizobium concentrate – canola oil (1:1) emulsion with 0.02 g/L Tween‐80; storage at pH 8 and temperature 4±1°C) and this emulsion with the required cell count and prolonged viability was used for the pre‐inoculation of seed or for in situ soil application.     

Ecological characterisation of <Emphasis Type="Italic">Steinernema siamkayai</Emphasis> (Rhabditida: Steinernematidae), a warm-adapted entomopathogenic nematode isolate from India

Our study describes basic ecological properties of Steinernema siamkayai Tiruchirappalli strain from India. The effect of temperature on nematode infectivity and development, laboratory host range and foraging behaviour were determined. The data showed that S. siamkayai is a warm-adapted nematode species with larval mortality observed between 15°C and 37.5°C and nematode reproduction occurring between 20°C and 35°C. All insect species used in this study were susceptible to S. siamkayai under laboratory conditions. Sixty infective juveniles (IJs) per insect were used and the lepidopterans, Galleria mellonella (100%) and Spodoptera exigua (85%), were the most susceptible species followed by the dipteran, Ceratitis capitata (60%), and lepidopteran, Cydia splendana (55%), and the coleopteran, Tenebrio molitor (45%), whereas the coleopteran, Curculio elephas (25%), was the least susceptible species. S. siamkayai infective juveniles (IJs) stood on their tails and jumped and could also attach to a mobile host at a rate of 27 IJs larvae⁻¹ out of 1000 IJs in 10 min. Larval mortality of G. mellonella by S. siamkayai on different substrates (sand, filter paper, filter paper sprinkled with sand) was 100% on all substrates. Number of IJs out of 100 IJs that penetrated into a G. mellonella host at different soil depths was the highest at the surface (44 IJs larva⁻¹) and the lowest at 5 cm depth (13 IJs larva⁻¹) with no larval mortality observed at 10 cm depth. In addition, the symbiotic bacterium of S. siamkayai was identified as Xenorhabdus stockiae based on genotypic and phenotypic characterisation. Bacterial growth was observed between 15°C and 41°C.     

Distribution of viruses in the water column of the ice-covered Rybinsk Reservoir and their contribution to heterotrophic bacteria mortality

Virioplankton and bacterioplankton abundance has been determined in the pelagic and littoral zones of the Rybinsk Reservoir during the ice-covered period. The role of viruses in heterotrophic bacterioplankton infection and mortality is assessed. At water temperatures between 0.3 and 0.9°C, the number of planktonic virus particles and planktonic bacteria varies from 37.1 × 10⁶ to 84.1 × 10⁶ particles/mL, (57.3 ± 2.1) × 10⁶ particles/mL on average and from 2.50 × 10⁶ to 6.11 × 10⁶ cells/mL, (3.66 ± 0.16) × 10⁶ cells/mL on average, respectively. The ratio of the virus number to the bacteria number varies from 8.8 to 27.9, being 16.5 ± 0.7 on average. Visually infected cells comprise 0.3–0.5% (1.5 ± 0.2% on average) of the total number of bacterioplankton. Infected bacterial cells contain from 5 to 107 (17 ± 4 on average) mature virus particles. The average virus-induced mortality of bacteria accounts for 13.0 ± 1.9% (variations range from 2 to 55%) of the daily bacterial production, indicating that viruses play an important role in the regulation of bacterioplankton production and abundance in the Rybinsk Reservoir during the ice-covered period.     

Comparative study of the entomopathogenic nematode, Steinernema carpocapsae, reared on mutant and wild-type Xenorhabdus nematophila

The symbiotic interaction between Steinernema carpocapsae and Xenorhabdus nematophila was investigated by comparing the reproduction, morphology, longevity, behavior, and efficacy of the infective juvenile (IJ) from nematodes reared on mutant or wild-type bacterium. Nematodes reared on the mutant X. nematophila HGB151, in which an insertion of the bacterial gene, rpoS, eliminates the retention of the bacterium in the intestinal vesicle of the nematode, produced IJs without their symbiotic bacterium. Nematodes reared on the wild-type bacterium (HGB007) produced IJs with their symbiotic bacterium. One or the other bacterial strain injected into Galleria mellonella larvae followed by exposing the larvae to IJs that were initially symbiotic bacterium free produced progeny IJs with or without their Xenorhabdus-symbiotic bacterium. The two bacterial strains were not significantly different in their effect on IJ production, sex ratio, or IJ morphology. IJ longevity in storage was not influenced by the presence or absence of the bacterial symbiont at 5 and 15 °C, but IJs without their bacterium had greater longevity than IJs with their bacterium at 25 and 30 °C, suggesting that there was a negative cost to the nematode for maintaining the bacterial symbiont at these temperatures. IJs with or without their symbiotic bacterium were equally infectious to Spodoptera exigua larvae in laboratory and greenhouse and across a range of soil moistures, but the absence of the bacterial symbiont inhibited nematodes from producing IJ progeny within the host cadavers. In some situations, such as where no establishment of an alien entomopathogenic nematode is desired in the environment, the use of S. carpocapsae IJs without their symbiotic bacterium may be used to control some soil insect pests.     

Determination of the kinetics of permeation of dimethyl sulfoxide in isolated corneas

Corneal cryopreservation requires that endothelial cells remain viable and intercellular structure be preserved. High viability levels for cryopreserved endothelial cells have been achieved, but preserving intercellular structure, especially endothelial attachment to Descemet's membrane, has proved difficult. Cell detachment apparently is not caused by ice, suggesting osmotic or chemical mechanisms. Knowledge of the permeation kinetics of cryoprotectants (CPAs) into endothelial cells and stroma is essential for controlling osmotic and chemical activity and achieving adequate tissue permeation prior to cooling. Proton nuclear magnetic resonance (NMR) spectroscopy was used to assess the permeation of dimethyl sulfoxide (DMSO) into isolated rabbit corneas. Corneas with intact epithelia were exposed to isotonic medium or 2.0 mol/L DMSO for 60 min and subsequently transferred to 2.0 or 4.0 mol/L DMSO, respectively, at 22, 0, or −10°C. DMSO concentration in the cornea was measured vs time. The Kedem-Katchalsky model was fitted to the data. Hydraulic permeability (m³/N·s) is 7.1×10⁻¹³+216%-11% at 22°C, 8.2×10⁻¹³+235%−21% at 0°C, and 1.7×10⁻¹⁴+19% −16% at −10°C. The reflection coefficient is 1.0+2%−1% at 22°C and 0°C, and 0.9±5% at −10°C. Solute mobility (cm/s) is 5.9×10⁻⁶+6%–11% at 22°C, 3.1×10⁻⁶+12%−11% at 0°C, and 5.0×10⁻⁸ cm/s+59%−40% at −10°C.     

Efficacy of entomopathogenic nematode,Steinernema carpocapsae against the diamondback moth,Plutella xylostella (L.) in laboratory condition

In vitro studies were carried out on the diamondback moth, Plutella xylostella larvae using an insect entomopathogenic nematode isolate, Steinernema carpocapsae obtained from the Koppert company, the Netherlands. Larvae of P. xylostella were collected from cabbage farms around Mashhad city of Iran. During the study, the responses of larvae at 25?°C for three periods of 24, 48 and 72?h with different concentrations of 0, 5, 10, 20, 40, 80, 160 and 320 third instar larvae of nematode (infective stage?=?IJs) per insect into 10?cm Petri dishes containing filter paper soaked with 1?ml of nematodes suspension were compared. Maximum mortality caused by S. carpocapsae nematode was 88% at 24?h, and it was 100% at 48 and 72 h. With increasing nematode population level and exposure time (ET in hour), mortality of P. xylostella larvae was increased. Based on probit analysis, LC₅₀ values of S. carpocapsae nematode in three test periods were 45.61, 12.02 and 40.80 IJs per insect, respectively. Initial ANOVA was performed for S. carpocapsae nematode. The effect of both nematode population levels (IJ) and ET on third instar larvae of the diamondback moth, P. xylostella and interaction between IJ and ET were significant. In general, it is recommended to apply this nematode in suitable condition for controlling diamondback moth.     

Effect of medium and temperature of storage on viability of lactic acid bacteria immobilized in κ-carrageenan-locust bean gum gel beads

Summary The influence of various storage solutions and temperature (4°C and 25°C) on viability ofStreptococcus salivarius subsp.thermophilus andLactobacillusdelbrueckii subsp.bulgaricus entrapped in κ-carrageenan-locust bean gum mixed gel beads was studied. The immobilized strains could be stored at 4°C in all storage solutions studied for at least 14 and 11 days respectively before counts decreased to 10⁵c.f.u./mL, which was considered to be the practical limit for their use as inoculum in a fermentation process. The most effective storage solutions for preserving cell viability at 4°C were NaCl, glycerol and sorbitol solutions forS. thermophilus, and PO₄ buffer and sorbitol solutions forL. bulgaricus. At 25°C,S. thermophilus could be stored for over 14 days in all solutions except glycerol, andL. bulgaricus for 4 days in 10% sorbitol.     

EFFECTS OF APPLICATION PARAMETERS AND ADJUVANTS ON THE FOLIAR SURVIVAL AND PERSISTENCE OF ENTOMOPATHOGENIC NEMATODE STEINERNEMA CARPOCAPSAE ALL STRAIN ON CABBAGES

Abstract  Effects of the critical parameters (spray pressure, the distance between a sprayer and the sprayed plant, the concentration of infective juveniles (Us), volumes of the sprayed suspension of IJs, the temperature and humidity combinations) and the addition of various adjuvants on the survival and persistence of entomopathogenic nematode Steinernema carpocapsae All strain on leaf surfaces of the Chinese cabbage Brassica pekingensis were determined. The results showed that (1) The pressure of a sprayer had negative influence on the persistence of IJs on the leaf. (2) The numbers of the living IJs collected on the leaf significantly increased with the IJ dosages applied on the leaf when the dosage was over 2 000 IJs per mL. (3) More IJs (from 10.1 IJs/cm² to 45.5 IJs/cm²) were collected on the leaf when more volumes of IJ suspension (from 3.3 mL to 19.8 mL) were sprayed. However, when the highest volume of IJ suspension was used, the IJ numbers collected did not increase. (4) In general, the survival of the IJs on the leaf decreased with the exposure time. (5) The formulation of IJs by adding xanthan gum, a sticker and detergent surfactant enhanced the survival and persistence of IJs. The number of living IJs on the leaf with 0.3 % of xanthan gum was 150 times higher than that of the IJs with water alone. IJ suspensions with different concentrations of glycerin and with 0.5 % molasses and 0.01 % detergent surfactant showed similar effects.     

Rapid age-related changes in infection behavior of entomopathogenic nematodes

Nonfeeding infective juvenile (IJ) entomopathogenic nematodes (EPNs) are used as biological agents to control soil-dwelling insects, but poor storage stability remains an obstacle to their widespread acceptance by distributors and growers as well as a frustration to researchers. Age is one factor contributing to variability in EPN efficacy. We hypothesized that age effects on the infectiousness of IJs would be evident within the length of time necessary for IJs to infect a host. The penetration behavior of "young" (<1-wk-old) and "old" (2- to 4-wk-old) Heterorhabditis bacteriophora (GPS 11 strain), Steinernema carpocapsae (All strain), and Steinernema feltiae (UK strain) IJs was evaluated during 5 "exposure periods" to the larvae of the wax moth, Galleria mellonella. Individual larvae were exposed to nematode-infested soil for exposure periods of 4, 8, 16, 32, and 64 hr. Cadavers were dissected after 72 hr, and the IJs that penetrated the larvae were counted. Larval mortality did not differ significantly between 72- and 144-hr "observation periods," or points at which larval mortality was noted, for any age class or species. However, age and species effects were noted in G. mellonella mortality and nematode penetration during shorter time periods. Initial mortality caused by S. carpocapsae and H. bacteriophora IJs declined with nematode age but increased with S. feltiae IJ age. Young S. carpocapsae IJs penetrated G. mellonella larvae at higher rates than old members of the species (27-45% vs. 1-4%). Conversely, old S. feltiae IJs had higher penetration rates than young IJs (approximately 8 to 57% vs. 4 to approximately 31%), whereas H. bacteriophora IJs had very low penetration rates regardless of age (3-5.6%). Our results show that the effect of age on IJ infectiousness can be detected in IJs aged only 2 wk by a 4-hr exposure period to G. mellonella. These results have important implications for storage and application of EPNs and suggest the possibility of shortening the time required to detect nematodes in the soil.     

Factors influencing biocontrol of jimsonweed (Datura stramonium L.) with the leaf-spotting fungus Alternaria crassa

In greenhouse tests, Alternaria crassa (Sacc.) Rands killed > 80% of inoculated jimsonweed (Datura stramonium L.) seedlings within 14 days following a 9-h dew period at 25°C with 1 × 10⁵ spores/ml, and after 8 h of dew at 1 × 10⁶ spores/ml. At least 10 h of dew with 1 × 10⁵ spores/ml and 9 h of dew with 1 × 10⁶ spores/ml were required to obtain 100% mortality of fungus-inoculated plants. Growth stage and inoculum concentration studies revealed that higher concentrations of inoculum were required to obtain 100% mortality of larger plants. Weed control was significantly reduced by day/night air temperatures of 35°C and 24°C, respectively, at all inoculum concentrations as compared to the controls at lower air and dew temperature regimes. The results of these studies indicate that A. crassa has potential as a biological herbicide for the control of jimsonweed.     

应用参数和辅助剂对昆虫病原线虫Steinernema carpocapsae All品系于小白菜叶面存活和黏附数量的影响

测定了叶面应用参数(喷雾压力、高度、线虫悬浮液浓度、线虫悬液量、温度和湿度)以及辅助剂对昆虫病原线虫S．carpocapsaeAll于小白菜叶面的存活率和叶面黏附数量的影响。结果显示：(1)喷雾压力对线虫于叶面的黏附数量有负影响;(2)线虫悬浮液浓度高于2000IJs／mL时,随着线虫浓度的增加,叶面上黏附的线虫数量也明显提高;(3)喷洒的线虫悬液量越多(从3．3mL到19．8mL),叶面上黏附的线虫数量也就越多(从10．1IJs／cm^2到45．5IJs／cm^2),但是当线虫悬液量超出19．8mL时,叶面上黏附的线虫数量不再提高;(4)感染期线虫在叶面存活率随着暴露时间的增长而下降;(6)加入黄原胶和表面活性剂可以提高线虫在叶面的存活率和黏附数量,其中加入0．3％黄原胶的线虫悬浮液在叶面存活的线虫数量是清水对照的150倍。线虫喷洒叶面停留24小时后,2％甘油的线虫悬浮液的线虫在叶面上的存活率大约是清水对照液的62倍,叶面上存活线虫数量也是清水对照液的53倍。     

Storage stability and sourdough acidification kinetic of freeze-dried Lactobacillus curvatus N19 under optimized cryoprotectant formulation

In this study, the response surface methodology was used to optimize the cryoprotective agent (skimmed milk powder, lactose and sucrose) formulation for enhancing the viability of Lactobacillus curvatus N19 during freeze-drying and storage stability of cells freeze-dried by using optimum formulation was evaluated. Our results showed that the most significant cryoprotective agent influencing the viability of L. curvatus N19 to freezing and freeze-drying was sucrose and skim milk, respectively. The optimal formulation of cryoprotective agents was 20 g/100 mL skim milk, 3.57 g/100 mL lactose and 10 g/100 mL sucrose. Using the optimum formulation during freeze-drying, the cell survival was found more than 98%. Under the optimal conditions, although only storage of the cells at 4 °C for 6 month retained the maximum stability (8.85 log cfu/g), the employed protectant matrix showed promising results at 25 °C (7.89 log cfu/g). The storage stability of cells under optimized conditions was predicted by accelerated storage test, which was demonstrated that the inactivation rate constant of the freeze-dried L. curvatus N19 powder was 9.74 × 10⁻⁶ 1/d for 4 °C and 2.08 × 10⁻³ 1/d for 25 °C. The loss of specific acidification activity after the storage at 4 and 25 °C was determined.     

In-vitro liquid culture of the entomopathogenic nematode,Steinernema colombiense,in orbitally shaken flasks

Steinernema colombiense, an entomopathogenic nematode species (EPN) was grown in two types of orbitally shaken flasks at 130?rpm and 28°C, containing 10 or 20?mL, respectively of a complex culture medium with an initial EPN-concentration of 1,000 Infective Juveniles (IJ)/mL. At the 10th day, the EPN-concentration was 58,771 individuals/mL with 87% of them in the IJ stage. No significant differences were found between the EPN growth kinetics in both types of flasks. The nematode-population growth was modelled by a re-parameterized Gompertz equation of three-parameters with best-fit values of 3.8 days for the lag time, 33.8 day^-1 for the maximum growth rate, and 57.3 (dimensionless) for the maximum asymptotic growth.     

Laboratory studies on the fungus Verticillium lecanii, a larval pathogen of the large elm bark beetle (Scolytus scolytus)

From 1972 to 1974, estimates of the natural larval mortality (> second instar) of elm bark beetles caused by pathogenic organisms were always below 7'5 % of the beetle population. The pathogenic fungus Verticillium lecanii was frequently isolated from field-collected dead larvae, and in the laboratory all larvae were killed in 5 days when exposed to spore concentrations of 4·5 × 10⁶ spores/ml. V. lecanii begins to lose its pathogenicity after prolonged culture on artificial media. The time taken for V. lecanii to kill Scolytus scolytus larvae when exposed to a logarithmic series of spore dilutions from 9·1 × 10⁷/ml to 9·1 × 10³/ml increased with decreasing amounts of inoculum. Even at spore concentrations as low as 9·1 × 10³/ml the mortality of treated larvae was greater than that of untreated individuals. At 100% r.h. all treated larvae were killed over a temperature range of 5–30 °C; those maintained at 25 °C were killed most rapidly and those kept at 5 °C the slowest.     

Anhydrobiotic potential and long-term storage of entomopathogenic nematodes (Rhabditida: Steinernematidae)

Anhydrobiosis is considered to be an important means of achieving storage stability of entomopathogenic nematodes that are used in biological control. This study explored the effects of anhydrobiosis on longevity and infectivity of infective juveniles (IJs) of three species of entomopathogenic nematodes Steinernema carpocapsae, Steinernema feltiae, and Steinernema riobrave at 5 and 25 degrees C. Anhydrobiosis was induced in water-dispersible granules (WG) at 0.966-0.971 water activity and 25 degrees C following a 7-day preconditioning of IJs at 5 degrees C in tap water. Survival and infectivity of the desiccated (anhydrobiotic) IJs was compared with non-desiccated IJs stored in water for different periods. Anhydrobiosis increased longevity of S. carpocapsae IJs by 3 months and of S. riobrave by 1 month in WG at 25 degrees C as compared with IJs stored in water. However, desiccation decreased S. feltiae longevity at 25 degrees C and of all three species at 5 degrees C. These results demonstrate a shelf-life of 5 months for S. carpocapsae at 25 degrees C and 9 months at 5 degrees C in WG with over 90% IJ survival. For S. feltiae, over 90% survival occurred only for 2 months at 25 degrees C and 5 months at 5 degrees C in WG. Steinernema riobrave had over 90% survival only for 1 month at 25 degrees C and the survival dropped below 85% within 1 month at 5 degrees C. Induction of anhydrobiosis in WG resulted in 85, 79 and 76% reduction in oxygen consumption by S. carpocapsae, S. feltiae, and S. riobrave IJs, respectively. Differences in IJ longevity among three species in water at 25 degrees C were related both to the initial lipid content and the rate of lipid utilisation, but not at 5 degrees C. The one-on-one infection bioassays indicated that desiccation had no negative effect on the infectivity of any of the nematode species suggesting no harmful effect on the IJs and/or their symbiotic bacteria. The species differences in IJ longevity and desiccation survival at different temperatures are discussed in relation to their foraging strategy and temperature adaptation.     

Dopant-free Starlike Molecular Hole Conductor with Ordered Packing for Durable all-Inorganic Perovskite Solar Cells

All-inorganic n-i-p perovskite solar cells (PSCs) using doped Spiro-OMeTAD as hole transport material (HTM) suffer from photothermal stability due to ionic diffusion and radical-induced degradation by the dopants. In this article, dopant-free starlike molecule (N2, N2-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-N5,N5-bis(4-methoxyphenyl)pyridine-2,5-diamine (BD)) is synthesized to engineer the stacking properties and delivered higher hole mobility than doped Spiro-OMeTAD (3.2 × 10⁻⁴ versus 1.76 × 10⁻⁴ cm² V⁻¹ s⁻¹) as dopant-free HTM. Starlike BD HTM has a twisted acceptor unit and strong dipole, forming crystalline and ordered packing film to ensure intramolecular charge transfer and improve mobility. The BD CsPbI₃ PSCs deliver the maximum efficiency of 19.19%, which is the highest performance for all-inorganic PSCs based on dopant-free HTMs. Meanwhile, the ordered molecules-packing blocks the migration channel of I⁻ ions to metal electrodes and improves the device stability. BD-based devices maintain more than 93% and 80% of the initial efficiency after 85 °C storage for 35 days and maximum power point (MPP) tracking at 85 °C for 1000 h, respectively.