Filter Paper Bioassay Research Articles

Preferences for livestock bedding as a development substrate of the stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), and potential application of entomopathogenic nematodes for controlling stable fly larvae.

The stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), is a significant insect pest with global veterinary implications due to its capacity to both cause nuisance and transmit disease-causing pathogens to livestock. This study aimed to determine the livestock bedding preferred for use as a development substrate by S. calcitrans larvae and field-collected adults. The result showed that S. calcitrans larvae exhibited a preference (26.7%) for 7-day-old cow manure. Gravid females displayed a pronounced preference (55.0%) for fresh cow manure. As there were eight choices, indifference would result in 12.5% for each bedding substrate. Furthermore, the efficacy of four entomopathogenic nematodes (EPNs), namely Heterorhabditis bacteriophora (Poinar), Heterorhabditis indica Poinar, Karunakar & David (Rhabditida: Heterorhabditidae), Steinernema siamkayai Poinar, Karunakar & David and Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae), against S. calcitrans larvae and the persistence after application to livestock bedding substrates were evaluated under laboratory conditions. In filter paper bioassays, all four EPNs caused 76.7%-100.0% mortality in the second instar larvae of S. calcitrans when applied at 50 and 100 infective juveniles (IJs)/cm2 within 5 days after exposure. For the third instar larvae of S. calcitrans, only H. indica induced high mortalities of 86.6% when applied at 100 IJs/cm2 within 5 days after exposure, while the other EPNs resulted in mortalities of less than 70%. The data further demonstrated that H. bacteriophora, H. indica and S. siamkayai remained present in the substrates linked to S. calcitrans larvae for as long as 7 days after the application of EPNs. This study demonstrates the potential of EPNs as a biologically based control agent against larvae of S. calcitrans, a serious pest and significant vector for various livestock animals.

Ixodes scapularis Is the Most Susceptible of the Three Canonical Human-Biting Tick Species of North America to Repellent and Acaricidal Effects of the Natural Sesquiterpene, (+)-Nootkatone.

Ticks are vectors of many human and animal zoonotic disease-causing agents causing significant global health and economic strain. Repellents and acaricides are integral to the human capacity for personal protection from tick bites. Nootkatone, a naturally occurring sesquiterpene found in the Alaskan cedar tree, grapefruit, and other sources, has been documented to be a potent acaricide. Research has also noted repellent effects against some tick species. In this study, our aim was to investigate the effect of synthetic, high-purity (+)-nootkatone on adult Ixodes scapularis, Dermacentor variabilis, and Amblyomma americanum ticks in an in vitro, vertical filter paper bioassay. (+)-nootkatone showed compelling tick repellency, but median effective concentrations (EC50) significantly differed among species. Ixodes scapularis were repelled at very low concentrations (EC50 = 0.87 ± 0.05 µg/cm2). Higher concentrations were required to repel D. variabilis (EC50 = 252 ± 12 µg/cm2) and A. americanum (EC50 = 2313 ± 179 µg/cm2). Significant post-exposure mortality, assessed 24 h after repellency trials, was also observed in I. scapularis but was absent entirely in D. variabilis and A. americanum. These tests demonstrate that nootkatone has a promising dual-action personal protection capacity against adult I. scapularis ticks, warranting further investigation in more natural environments and in the presence of host cues.

Do Commercial Insect Repellents Provide Protection against the Tick Amblyomma sculptum (Acari: Ixodidae)?

Amblyomma sculptum is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against A. sculptum is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against A. sculptum. Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF!® and Repelex®), Icaridin (Exposis® and SBP®), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly (p < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control (p < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!®, Repelex®, and Exposis® were tested as they showed better performance in the filter paper test. OFF!® showed the best percentage of repellency (100%), followed by Repelex® (96.8%), and Exposis® (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against A. sculptum presented in this study is crucial, since this is the main ectoparasite of humans that can transmit Rickettsia rickettsii when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.

Time-dependent mortality and behavioral response of Odontotermes obesus (Blattodea: Termitidae) against different dose rates of pesticides for sustainable forest management

Termites have become a global concern, and their effective management has remained a challenge since time immemorial. Certain microbial and botanical agents have been used for their management, but their efficacy has been compromised, particularly in field conditions. Hence, the current study was designed to check the efficacy of low doses of different pesticides, such as chlorpyrifos, fipronil, bifenthrin, and chlorantraniliprole, against mortality and behavioral responses of Odontotermes obesus at two different temperatures (16 ± 1 and 26 ± 1°C). The discrete behavioral symptoms included intoxication, ataxia, moribundity, and death. Laboratory-maintained termite workers were exposed to different concentrations of pesticides through a filter paper bioassay. All tested pesticides and their concentrations differed significantly regarding their lethal time (LT50) values compared to the mortality of termite workers. Moreover, the LT50 values of pesticides gradually decreased with increased pesticidal concentrations. Temperature also had a significant effect on the efficacy of tested pesticides as all pesticides showed better results at higher temperatures. At both tested temperatures, chlorantraniliprole (5 ppm) proved to be the most effective pesticide against termite workers. Similarly, the behavioral symptoms also varied depending on pesticides and their administered concentrations and existed for a relatively longer time span at lower temperatures. In most cases, the order of responses was moribundity, followed by intoxication and ataxia. Moribundity and intoxication were the most frequently observed symptoms for chlorpyriphos and bifenthrin-treated termite workers. In the case of fipronil, intoxication was the most pronounced symptom. Similarly, the maximum value of ataxia was recorded in the case of chlorantraniliprole. However, moribund symptoms lasted longer in all tested concentrations of chlorantraniliprole, followed by ataxia and intoxication. The overall order of toxicity was chlorantraniliprole &amp;gt; bifenthrin &amp;gt; fipronil &amp;gt; chlorpyrifos. These pesticides, at their low doses, did not exhibit any repellent action and were not detected by the foraging termite workers. Moreover, their slow action mechanism makes them a suitable candidate for infecting whole colonies away from treated surfaces. Therefore, these pesticides can be successfully incorporated into different integrated termite management programs to keep the plantation free from threatening underground pests.

Biocontrol Potential of Entomopathogenic Nematodes against Odontotermes obesus (Blattodea: Termitidae) under Laboratory and Field Conditions

Odontotermes obesus (Blattodea: Termitidae) is a prevalent subterranean wood-eating termite species that causes damage to mature trees, saplings and seedlings. The efficacy of most synthetic insecticides against this notorious pest has been compromised primarily because of its enigmatic feeding behavior and development of resistance to a number of insecticides. It has therefore become necessary to explore other alternative biologically sound and low-impact termite control methods, particularly for use in forests. Hence, this study was designed to verify the efficacy of different indigenous EPN isolates (Steinernema carpocapsae, Heterorhabditis bacteriophora and Heterorhabditis indica) against workers of Odontotermes obesus. The pathogenicity of each nematode isolate was assessed in laboratory conditions using filter paper and sawdust bioassay at two different temperatures (16 ± 1 and 26 ± 1 °C). Additionally, the efficacy of the nematode species was also assessed in field conditions. The results of the experiments revealed that the mortality of termite workers was more pronounced in sawdust bioassay in comparison with filter paper bioassay at both the tested temperatures. The mortality response in both bioassays was more pronounced at the higher temperature. A significantly higher mortality was recorded at both tested temperatures for S. carpocapsae followed by H. bacteriophora and H. indica. A dose-dependent positive mortality response was also recorded at both tested temperatures. Similar to the laboratory trials, the field applications of the three tested nematode species showed that maximum mortality was recorded for S. carpocapsae followed by H. bacteriophora and H. indica. It was therefore concluded that indigenous EPNs can provide more effective control of termites, possibly because of their direct interaction with pest species in the soil and the possibility of causing secondary infection through infected cadavers.

천연 진드기기피제 개발을 위한 블렌딩 에센셜오일의 진드기 기피효능에 관한 연구

In this study, an experiment was conducted to measure the tick repellent efficacy through the synergy effect according to the type and ratio of blending essential oil. The subjects were adults and nymphs of the Haemaphysalis longicornis, and the repellent efficacy was measured using the filter paper bioassay method. Based on the past research, citronella oil, geranium oil, vetiver oil, and neem oil were selected as a single treatment experiment since their repellent efficacy was confirmed. The first experiment revealed that the repellent efficacy of citronella oil and geranium oil were high. Afterwards, in order to investigate the synergy effect on tick repellent efficacy, experimental group was consisted of neem seed oil (carrier oil) that was blended with citronella and geranium oil, at a ratio of 1:1, 2:1, and 17:3 (15%). Also, negative control group was composed of ethanol that was blended with citronella and geranium oil at the same ratio of experimental group. As a result, the blending of citronella and neem seeds showed higher repellent efficacy in all blending ratios than the blending of geranium and neem seeds. In adult ticks, blending ratio of citronella and neem seeds was 1:1 and 17:3, showed the most significant difference of repellent efficacy. In nymph ticks, when the blending ratio of citronella and neem seed was 1:1 and 17:3, the repellent efficacy was the same as that of the positive control commercial repellent. In conclusion, it was confirmed that both nymph and adults ticks showed higher repellent efficacy when blended than single treatment. In this study, the synergy effect of the blending of citronella and neem seeds on the tick repellent effect has a high potential to replace synthetic repellents.

Surveillance of Aedes populations in Jiangsu Province in 2020

To investigate the seasonal Aedes population fluctuation and the resistance of Aedes populations to common insecticides in Jiangsu Province in 2020, so as to provide insights into vector-borne infectious diseases control. One village was randomly sampled from each of Xinbei District of Changzhou City and Zhangjiagang County of Suzhou City in southern Jiangsu Province, Hai'an County of Nantong City and Yandu District of Yancheng City in Central Jiangsu Province, and Suining County of Xuzhou City and Sihong County of Suqian City in northern Jiangsu Province during the period between May and October, 2020. A small ponding container was sampled, and larval Aedes mosquitoes were collected using straws once each in early and late stages of each month. All larvae were bred in laboratory to adults for population identification. In addition, larval breeding were observed in all small ponding containers in and out of 30 households that were randomly sampled from six surveillance sites, and the larval mosquito density was estimated using Breteau index. Larval A. albopictus mosquitoes were sampled around Cuiyuan New Village in Jintan District of Changzhou City, and bred in laboratory to the first offspring generation, and the susceptibility of adult female mosquitoes to deltamethrin, lambda-cyhalothrin, malathion, and propoxur was tested using the filter-paper bioassay recommended by WHO. A total of 1 165 larval Aedes mosquitoes were captured from small ponding containers in six surveillance sites of Jiangsu Province in 2020, and all were identified as A. albopictus following eclosion. The largest number of Aedes larvae captured was found in July. A total of 1 152 households were investigated in six surveillance sites, and the mean Breteau indexes were 9.58, 13.20, 13.71, 13.20, 12.18 and 5.58 from May to October, respectively, while a high Aedes transmission risk was seen in Xinbei District of Changzhou City, with a higher Breteau index than in Suining (H = 23.667, Padjusted = 0.001) and Sihong (H = 22.500, Padjusted = 0.003) counties. The field-captured A. albopictus from Cuiyuan New Village in Jintan District of Changzhou City remained sensitive to malathion, but was resistant to propoxur, and developed high-level resistance to deltamethrin and lambda-cyhalothrin. A. albopictus was present in southern, central and northern Jiangsu Province in 2020, and the larval density peaked in July. A. albopictus captured from Cuiyuan New Village in Jintan District of Changzhou City has developed high-level resistance to pyrethroid pesticides.

Use of the generalist predator Anystis baccarum in greenhouse IPM: Interactions with other biological control agents, a laboratory study

A generalist predatory mite, Anystis baccarum (L.), was developed as a new biocontrol agent in Canada, and became commercially available in 2022. Because successful biological control programs in greenhouse crops rely on the release of several natural enemies simultaneously to deal with multiple pest species, this study assessed the interaction of A. baccarum with other commonly used biocontrol agents in laboratory trials. Note that only adult stages were used, because the agents tested are predominantly sold and released as adults. Anystis baccarum killed and consumed the generalist phytoseiid mites, Neoseiulus cucumeris (Oudemans) and Amblyseius swirskii Athias-Henriot; however, the mortality of the phytoseiid mites was reduced when an alternative food, Ephestia kuehniella Zeller eggs, was available. There was no intra-guild interaction between A. baccarum and the soil-dwelling predatory mite, Stratiolaelaps scimitus (Womersley). No statistically significant mortality was observed when Orius insidiosus (Say), a generalist hemipteran, or Delphastus catalinae (Horn), a coccinelid beetle used to control whiteflies, were confined with A. baccarum without alternative food for 24 h. The susceptibility of A. baccarum to the entomopathogenic fungus Beauveria bassiana (Balsamo) GHA strain was evaluated by exposing the mites to conidia in a filter paper bioassay. Differences in mite mortality were not significant across all treatments, and only one case of successful sporulation fungal growth was observed from cadavers recovered in the experiments; similarly, differences in the number of eggs produced were not significant across all treatments. Although the laboratory trials sometimes showed severe predation pressure from A. baccarum on other biocontrol agents, they are likely to be functionally compatible in the greenhouse owing to differences in habitat preferences and availability of other prey (pests) or another food source. Results of the current study provide insights that will enable the development of rational biocontrol programs that include A. baccarum.

Pediculicidal Activity of Foeniculum vulgare Essential Oil in Treatment of Pediculus capitis as a Public Health Problem.

Pediculosis, caused by Pediculus spp is an important public health problem in urban and rural areas around the world. Natural compounds such as plant essential oils (EOs) have been suggested as a potential alternative for insect pest control recently. The purpose of this study was to investigate the toxicity of Foeniculum vulgare essential oil against the head louse, Pediculus capitis under laboratory conditions. Fennel essential oil components were analyzed using GC-mass apparatus. Immersion and contact filter paper bioassays were used to evaluate fennel essential oil toxicity at the two-fold concentrations of 2.5, 5, 10, 20, and 40% against nit and nymph/adult stages of the head louse. Trans-anethole, α-Thujone, and limonene, which consisted of 76.08%, 10.37%, and 5.34% were the most components of fennel oil respectively. The LC50 values for the adult /nymphs were 11.5, 6.4, 3.9, 3.1 and 2.5% and LC99 values were 29.5, 15.2, 12.8, 10.8, and 7.4% at 10, 20, 30, 45 and 60 minutes after exposure respectively. The lethal times (LT50) for adults/nymphs were 5.2, 8.1, 9.5, 20.5, and 45.8 minutes and LT99 were 138.6, 91.3, 23.8, 21.7, and 13.9 minutes in the concentrations of 2.5, 5, 10, 20 and 40%, respectively. LC50 and LC99 values were 2.32% and 7.36% after 5 days for the eggs. Fennel essential oil at the concentration of 15% after 20min is suggested to develop as an appropriate formulation to evaluate in clinical trials.

Susceptibility of Anopheles sinensis to insecticides in Puyang City, Henan Province

To investigate the susceptibility of Anopheles sinensis to malathion, deltamethrin and lambda-cyhalothrin in Puyang City, Henan Province, so as to provide the scientific basis for local malaria vector control. An. sinensis was captured from Puyang County, Puyang City of Henan Province in September 2018 and July 2020, and the susceptibility of field captured An. sinensis to malathion, deltamethrin and lambda-cyhalothrin was tested using the filter-paper bioassay recommended by WHO. The insecticide resistance level was assessed based on the WHO criteria. In 2018 and 2010, the half knock-down times (KT50) of malathion were 91.08 min and 40.95 min for An. sinensis, with knock-down rates of 37.50% and 60.87% 60 min post-exposure to malathion and 24-hour mortality rates of 90.91% and 100%, respectively, and the insecticide resistance levels were moderately resistant (M) and susceptible (S). The KT50 of deltamethrin were 415.56 min and 341.19 min for An. sinensis in 2018 and 2020, with knock-down rates of 22.92% and 16.98% 60 min post-exposure to malathion and 24-hour mortality rates of 22.92% and 16.98%, and the insecticide resistance levels were all resistant (R). The KT50 of lambda-cyhalothrin were 164.22 min and 236.22 min for An. sinensis in 2018 and 2020, with knock-down rates of 30.39% and 38.30% 60 min postexposure to malathion and 24 h mortality rates of 19.60% and 21.28%, respectively, and the insecticide resistance levels were all R. An. sinensis is relatively susceptible to malathion but has developed high-level resistance to deltamethrin and lambda-cyhalothrin in Puyang City, Henan Province..

Biocontrol potential of the entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) against the termite species, Microtermes obesi (Holmgren) (Blattodea: Termitidae)

BackgroundGlobally, termites cause a great problem for the farmers which eat the stalk of the wheat, maize, and the sugarcane and also affect the growth of vegetables. For ecological farming system, biocontrol agents represent a vital implement in pest management policies. Biological control can play a probable, even more considerable part to reduce the adverse possessions of synthetic chemical pesticides.ResultsThe present study aimed to evaluate the biocontrol potential of one heterorhabditid species and 4 steinernematid species against the termite species (Microtermes obesi (Holmgren) (Blattodea: Termitidae)) on filter paper bioassay and wooden logs. Among all tested species of the entomopathogenic nematodes, maximum mortality rates 100% were obtained by using Steinernema pakistanense N-KA.04 and S. bifurcatum N-KA.93 after 48 h of the application. S. siamkayai N-KA.12 mortality ranged (85–87%), followed by S. ceratophorum N-KA.57 (77–80%) and then Heterorhabditis indica N-KA.03 (70–77%) at the highest concentrations (350–650 IJs/ml).ConclusionsThe expansion of appropriate application products for the management of termite effectiveness, observing and timing of application, participation of farmers in checking, and judgment is essential to avert disasters of entomopathogenic nematodes (EPNs) in field conditions and to make farmers’ confident with the use of the most promising species of EPNs.

Sublethal concentrations of spinosad synergize the pathogenicity of fungi to larvae of Ephestia kuehniella (Lepidoptera: Pyralidae)

We evaluated the efficacy of four entomopathogenic fungi (EPF) and their compatibility with the bioinsecticide spinosad for control of Ephestia kuehniella (Zeller) under laboratory conditions. Three EPF, including Beauveria bassiana (Balsamo-Criveili) Vuillemin isolates Z1 and Iran 1395C, Lecanicillium (= Verticillium) lecanii (Zimmerman) Zare &amp; Gams, isolate Iran 229, and Purpureocillium (Paecilomyces) lilacinum (Thom) Luangs-ard, Hywel-Jones &amp; Samson, isolate Iran 1026 were tested against third and fifth larval instars of Ephestia kuehniella using a filter paper bioassay. Mortality caused by the EPF ranged from 63.3-72.5% for third instars and 50-65.5% for fifth instars, with LT50 ranging from 8.4-10.5 d and 10.1-12.9 d, respectively. The effect of spinosad at LC10 (= 26.2 ppm) on EPF spore germination was evaluated and found to be negligible, ranging from 0% for B. bassiana Z1 to 5.7% for P. lilacinum. The LC50 values for spinosad against third and fifth instar E. kuehniella larvae were 452.5 and 1446 ppm, respectively. Subsequently, spinosad at LC10 was applied to third instar E. kuehniella larvae 24 h before application of the EPFs at LC50. The addition of spinosad to applications of L. lecanii and B. bassiana Z1 and Iran1395C isolates synergized their pathogenicity to E. kuehniella larvae, whereas the effect was merely additive for P. lilacinum. Our results suggest that these EPF isolates can be used effectively in combination with spinosad for management of E. kuehniella in stored products.

Effectiveness of Entomopathogenic Nematodes against the African White Rice Stem Borer Maliarpha separatella Rag

The efficacy of three entomopathogenic nematodes (EPN) species Steinernema carpocapsae Weiser, Steinernema karii Waturu, Hunt & Reid, Heterorhabdtids indica Poinar, Karunaka & David and two EPN isolates collected from Coastal Kenya (EX MOMBASA) and Rift valley (EX NAKURU) was evaluated against larvae of African white rice stem borer, Maliarpha separatella Rag. The experiment was carried out using no- choice modified filter paper bioassay at KARI-Mwea. Whatman filter paper was substituted with white cotton cloth discs. The activity of the biological agents under study was determined at 25℃ and 65% relative humidity, with concentrations of 50, 100 and 200 infective juveniles (IJs) per one M. separatella third instar larva. The larvae were confined in 60mm plastic petri dishes in darkness as the larvae spend their entire life inside the rice stems. The mortality rate was determined at 24, 48, 72 and 96 hours after application of the nematode suspension. Significant virulence was obtained with all the nematode species at 200 infective juveniles (IJs). There was low mortality at 50 and 100 concentration rates. All the EPNs significantly reduced M. separatella larvae after 48 hours in the following order H. indica> EX NAKURU> S. carpocapsae> EX MOMBASA >S. karii. The number of nematodes from the infected cadavers after 48 hours post infection was H. indica (553), EX –MSA (294), EX-NKU (242), S. karii (168) and S. carpocapsae (157). S. karii took the longest time (96 hours) to kill all the test insects. In conclusion, the study shows that EPNs are effective against M. separatella and could be used within an integrated pest management strategy for the pest. There is need to carry out further studies to determine effective dosages under field conditions.

Resistance of the stable fly, Stomoxys calcitrans (Diptera: Muscidae), to cypermethrin in outbreak areas in Midwestern Brazil.

Population explosions of the stable fly (Stomoxys calcitrans) have become a serious concern for livestock producers near sugarcane mills in some regions of Brazil due to the insect's massive reproduction on sugarcane byproducts and waste. Despite the limited efficiency of insecticides for controlling stable fly outbreaks, producers still rely on chemical control to mitigate the alarming infestations in affected areas. This study evaluated the susceptibility of S. calcitrans populations to cypermethrin in the state of Mato Grosso do Sul, Brazil. Stable flies were tested from three field populations and two colonies, established from flies previously collected at sugarcane mills. Wild flies were collected with Nzi traps in areas of sugarcane plantations. Both wild and colonized flies were exposed to eleven concentrations of cypermethrin in impregnated filter paper bioassays. All the populations proved to be resistant to cypermethrin, with resistance factors among field populations ranging from 6.8 to 38.6. The intensive use of insecticides has led to the development of pyrethroid resistance in stable fly populations in the proximities of sugarcane mills in the state of Mato Grosso do Sul.

Biogenic design of ZnS quantum dots - Insights into their in-vitro cytotoxicity, photocatalysis and biosensing properties

Zinc sulphide Quantum Dots (QDs) are semiconductor nanoparticles that have profound applications in medical imaging, photocatalysis and biosensing. Of late, green synthesis of ZnS QDs has emerged as an useful substitute for the routine chemical synthesis. The present study reports the biosynthesis of ZnS QDs using the fungus Aspergillus sp. under ambient conditions. In the present study, the mechanism behind the antibacterial action of the biosynthesized ZnS Quantum Dots has been explored. It was found that biogenesis using fungus has resulted in the synthesis of spherical crystalline ZnS particles of mean diameter 6.3 nm. FTIR analysis indicated the presence of active organic functional groups on the surface of the QDs. The optical and structural features of the biogenic ZnS were found to be comparable with that of the chemically synthesized quantum dots. Thereafter, the antibacterial activities of the biosynthesized ZnS QDs were observed against pathogenic bacteria. The green synthesized ZnS exhibited excellent antibacterial activity and were quantified using filter paper bioassay. Experimental evidences indicated that the antibacterial strategy relied on bacterial cell membrane disruption, leakage of the cytoplasmic contents and associated ROS mediated oxidative damages leading to bacterial cell lysis. Further, the prospects of biogenic ZnS for photodegradation of dyes and sensing of heavy metals in aqueous phase were investigated.

Effect of sodium chloride, potassium chloride on germination and growth of Foxtail millet (Setaria italica L.)

Foxtail millet (Setaria italica L.) is the second most important species of Millet belonging to family Poaceae. It is a cereal crop mainly planted in poor sites of East Asia. In the present study the impact of different concentrations (100 mM, 150 mM, 200 mM, and 250 mM) of NaCl, KCl separate and in combination of both these salts in equal amounts was studied on germination ratend some growth parameters of foxtail millet (Setaria italica L.) using filter paper bioassay and pot experiment. Results showed that 100 mM of NaCl and KCl had the least effect on germination and growth of foxtail millet. However, under all the higher concentrations (150, 200, and 250 mM) of NaCl, KCl marked decrease in radicle length, plumule length, germination rate, stem length, stem thickness, leaves length, leaves number, number of tillers, whole plant weight, spike length, number of grains per spike and weight of 50 grains was recorded as compared to control plants. In combined salts stress, a marked reduction in all growth parameters of the test plant in all salt levels was recorded. It is concluded that with an increase in salt concentration, the effects of salt stress became more pronounced in all salt treatments. The results revealed that the effects of combined salts on the test plants were more pronounced as compared to the effects when the plants were treated with NaCl and KCl salts alone. Keywords: Foxtail millet (Setaria italic L.); KCl; NaCl; Poaceae; Salt stress http://dx.doi.org/10.19045/bspab.2019.80080

Repellent Effects of Encapsulated Carvacrol on the Rhipicephalus (Boophilus) microplus (Acari: Ixodidae).

Rhipicephalus (Boophilus) microplus (Canestrini) is a problem for livestock production systems, and its control has become challenging due to the selection of tick populations resistant to synthetic chemical acaricides. The use of repellent compounds prevents contact between the arthropod parasite and the host and can, thus, contribute to increases in the efficacy of these acaricides. Carvacrol monoterpenic phenol is a possible alternative method for controlling R. (B.) microplus; however, this compound is highly volatile, and its volatilization can be decreased through microencapsulation, which results in the timed release of the compound. The cell wall of Saccharomyces cerevisiae can be utilized for the protection of volatile molecules. The aim of this study was to evaluate the in vitro repellent effect of yeast cell wall-encapsulated carvacrol on susceptible R. (B.) microplus larvae. Specifically, the vertical filter paper bioassay was employed to analyze the repellent activity of encapsulated carvacrol, nonencapsulated carvacrol, and N,N-diethyl-meta-toluamide at concentrations ranging from 0.75 to 0.001 mg/cm2, and the repellent activities were evaluated. Both carvacrol and encapsulated carvacrol exhibited repellent effects on R. (B.) microplus larvae, and the encapsulated compound showed the highest repellent activities at the lowest concentrations. Carvacrol encapsulated exhibited a low repellent concentration in all times (≤0.05 mg/cm2), whereas the carvacrol nonencapsulated ranged CR50 from 0.13 to 0.27 mg/cm2 at 1- to 6-h posttreatment. The present paper provides the first description of the use of a microencapsulation technique for achieving the highest repellent effect of carvacrol and indicates that this technique might be used to obtain new delivery systems for volatile and hydrophobic compounds.

Detection of Reduced Susceptibility to Chlorfenapyr- and Bifenthrin-Containing Products in Field Populations of the Bed Bug (Hemiptera: Cimicidae).

Insecticide resistance is a major impediment for effective control of Cimex lectularius L. Previous resistance detection studies with bed bugs have focused on certain pyrethroid, neonicotinoid, organochlorine, organophosphate, and carbamate insecticides. Within the pyrethroid class, resistance studies have mostly been limited to deltamethrin, lambda-cyhalothrin, and alpha- and beta-cyfluthrin. The goal of this study was to develop diagnostic concentration bioassays for assessing bed bug susceptibility levels to chlorfenapyr- and bifenthrin-containing products. First, glass vial and filter paper bioassay methods were compared for their utility in susceptibility monitoring. Statistical comparison of toxicity data between bioassays indicated that the vial assay was less confounded by assay susbtrate effects, required less insecticide, and was faster, especially for chlorfenapyr. Next, using vial diagnostic concentrations (LC99) for each insecticide, 10 laboratory-adapted field strains and the Harlan lab-susceptible strain were screened for susceptibility to chlorfenapyr and bifenthrin. The results of this study reveal recent bed bug susceptibility levels to certain chlorfenapyr- and bifenthrin-containing products. Reduced susceptibility was detected in three and five field strains to chlorfenapyr and bifenthrin, respectively. Detection of reduced susceptibility suggests that certain strains may be segregating toward greater chlorfenapyr and bifenthrin resistance. These results merit continuous resistance monitoring efforts to detect chlorfenapyr and bifenthrin susceptibility shifts. Additionally, to reduce insecticide selection pressures and delay resistance development, adoption of integrated bed bug control strategies that combine chemical and nonchemical methods is recommended.

Acaricidal and insecticidal activities of essential oils of Cinnamomum zeylanicum barks cultivated from France and India against Dermatophagoides spp., Tyrophagus putrescentiae and Ricania sp.

The chemical composition of Cinnamomum zeylanicum bark oils cultivated from France and India was analyzed by GC–MS. The main components of C. zeylanicum oil were cinnamaldehyde (63.97 and 67.21%) and eugenol (6.84 and 19.79%) from France and India, respectively. Acaricidal and insecticidal activities of C. zeylanicum oils against Dermatophagoides sp, T. putrescentiae and Ricania sp. were evident. The LC50 values of C. zeylanicum oil were 123.77 and 93.06 mg/L in samples from France and India, respectively, against Ricania sp. adults in the spray bioassay. Using the leaf-dipping bioassay, the LC50 values of the oil from France and India were 80.99 and 57.44 mg/L, respectively, against Ricania sp. nymphs. Acaricidal activity of the C. zeylanicum oil from India in the fabric disk bioassay (LD50, 0.64, 0.51 and 1.72 μg/cm3, respectively) was greater than France oil (LD50, 0.92, 0.81 and 1.82 μg/cm3, respectively). In the filter paper bioassay, india oil (LD50, 1.82, 1.55 and 3.08 μg/cm2, respectively) was more potent than France oil (LD50, 2.07, 1.94 and 6.20 μg/cm2, respectively) against D. farinae, D. pteronyssinus and T. putrescentiae. The results indicate that the essential oils of C. zeylanicum barks could be an effective natural acaricide and insecticide for controlling house dust mites, stored food mites and fruit pests.

Control of primary reproductives of Microtermes spp. in soil treated with Galleria cadavers infected with Heterorhabditis indica

The virulence of entomopathogenic nematodes (EPN) to the primary reproductives – alates and dealates – ofMicrotermesspp. was examined. Mortality in alates was observed in 18 h in the filter paper bioassay to test the relative virulence of infective juveniles (IJ) ofHeterorhabditis indicaandSteinernema abbasi. The LD50 forH. indicawas achieved with 5.11 IJ alate−1at 60 h, while forS. abbasiit was attained at 72 h with 6.91 IJ alate−1. Both nematodes completed their life cycle in the alates with an average production per cadaver of 3245 IJ and 2349 IJ forH. indicaandS. abbasi, respectively, at an infection dose of 30 IJ alate−1. ThusH. indicawas selected for the soil assay. The soil was implanted withH. indica-infected cadavers ofGalleria mellonella. Within 72 h 100% mortality was observed in the dealates. Successful recycling of nematodes in the termite cadavers reinforced the suitability ofH. indicafor the biological control of primary reproductives.