LT50 Values Research Articles

Frost survival and gene expression in timothy (Phleum pratense L.) cultivars as affected by age and selection in diverse field environments.

The sustainable production of perennial grasses in Northern Norway is at risk due to the ongoing climate change. The predicted increase in temperatures and variable weather patterns are further expected to create challenges for winter survival of timothy (Phleum pratense L.). Knowledge about the molecular mechanisms underlying freezing tolerance is crucial for developing robust cultivars. The current study is aimed at identifying genes involved in freezing stress response of timothy and studying gene expression differentiation due to field selection in contrasting environments using RNAseq. Four timothy cultivars were field tested for three years in Tromsø and Vesterålen, in Northern Norway. The surviving material from the field tests, along with plants raised from the original seed lots, were subjected to freezing tests. LT50 values varied across cultivars and materials. Many genes coding for transcription factors and proteins known to play an important role in freezing tolerance, like dehydrins, c-repeat binding factors, and late embryogenesis abundant proteins were upregulated with decreasing temperatures. Moreover, genes associated with glycolysis/gluconeogenesis, TCA cycle, glutathione metabolism, proteasome pathways and genes encoding autophagy-related proteins, plasma membrane-associated proteins, sugar and amino acid transporters had elevated expression in field survivors compared to plants raised from the original material. The lower freezing stress tolerance of field survivors despite the elevated expression of several stress-responsive genes might be due to a combination of selection in the field and the age effect. Furthermore, differences in freezing stress response between northern and southern adapted cultivars and surviving material from two field trial locations are discussed.

The effectiveness of garlic extract against Spodoptera litura on Chili

Spodoptera litura is a polyphagous pest and attack many families of cultivated plants, such as chili plants. Application of synthetic pesticides is still the mainstay for controlling this pest in the field. To support eco-friendly plant protection management, it is important to explore potential natural materials such as garlic extract. This research aims to determine the potential of garlic extract in controlling S. litura on chili plants, and to see its indirect effect on chili yield. The research was carried out in two sites, in the laboratory and the field. The experiment used a completely randomized design with 6 treatments and 4 replications. The concentrations of garlic extract, i.e., control (0%), 24%, 26%, 28%, 30%, and 32%. The results showed the application of garlic extract had a significant effect on the mortality of S. litura, the frequency of attacks, and the intensity of pest attacks in the field, and had an effect on the variable number of fruit and fruit weight of chili plants. The LC50 and LC90 values reached 19.66% and 29.97% in the laboratory, and 28.30% and 34.3%% in the field, respectively. The LT50 and LT90 values from the 32% garlic extract in the laboratory were respectively 3.37 and 7.23 days. The application of garlic extraction affected growth and yield, i.e. healthy leaves, number of fruits, and weight of fruits in chili. The garlic extract is potentially used as an organic pesticide to suppress the S.litura attacks while keeping the plant's growth and yield.

Toxicity Assessment on Odonata Larvae Survivability in Monitoring Heavy Metal Contaminations

The aquatic ecosystem has been suffering a continuous increase of metal contamination such as Cadmium (Cd), Zinc (Zn), and Manganese (Mn) due to their inadequate high potential to disturb the aquatic organism population. Meanwhile, some insects such as Pseudagrion microcephalum and Ischnura senegalensis can be used as biological indicators to determine stream health. Therefore, this study was conducted to determine the relationship between the heavy metal concentration and its effect on the survivability of two different species of damselfly larvae from the family Coenagrionidae; Pseudagrion microcephalum and Ischnura senegalensis. In this study, there is a significant effect of three heavy metal exposures on the survivability of P.microcephalum (F11,180=14.50, P=0.00) and I.senegalensis (F11,180 =15.10, P=0.00). Pseudagrion microcephalum is more tolerable towards Mn (F3,60=13.19, P=0.00) and Zn (F3,60=16.07, P=0.00) at different concentrations compared to I.senegalensis. In the meantime, I.senegalensis was tolerable to Cd exposure. The LC50 value of Cd was much lower than other heavy metals. Besides, the LT50 value of Cd at 200 mg/L was the lowest on P. microcephalum (31 hr) and I. senegalensis (36 hr) compared to other heavy metals. Cd was the most toxic to P.microcephalum and I.senegalensis larvae followed by zinc and manganese (LC50 & LT50=Cd > Zn > Mn). It is concluded that I.senegalensis was tolerant towards Cd, Mn, and Zn compared to P.microcephalum and Cd had the fastest-acting toxicity and significantly reduced the lethal time of mortality on both species.

The Effect of Botanical Pesticides Azadirachtin, Celangulin, and Veratramine Exposure on an Invertebrate Species Solenopsis invicta (Hymenoptera: Formicidae).

The injudicious and excessive use of synthetic pesticides has deleterious effects on humans, ecosystems, and biodiversity. As an alternative to traditional crop-protection methods, botanical pesticides are gaining importance. In this research endeavor, we examined the contact toxicity, knockdown time, lethal time, and toxicity horizontal transmission of three natural pesticides from plants (azadirachtin, celangulin, and veratramine) on red imported fire ants (RIFA; Solenopsis invicta). Our research findings indicated that azadirachtin and celangulin exhibited relatively high toxicity, with median lethal dose (LD50) values of 0.200 and 0.046 ng/ant, respectively, whereas veratramine exhibited an LD50 value of 544.610 ng/ant for large workers of S. invicta at 24 h post-treatment. Upon treatment with 0.125 mg/L, the (median lethal time) LT50 values of azadirachtin and celangulin were determined to be 60.410 and 9.905 h, respectively. For veratramine, an LT50 value of 46.967 h was achieved after being tested with 200 mg/L. Remarkably, azadirachtin and celangulin were found to exhibit high horizontal transfer among RIFA, with high secondary mortality (100%) and tertiary mortalities (>61%) after 48 h of treatment with 250 mg/L, as well as with their dust formulations for 72 h. However, veratramine did not exhibit significant toxicity or horizontal transfer effects on RIFA, even at high concentrations. These findings suggest that azadirachtin and celangulin are likely to have a highly prominent potential in the management of S. invicta.

Physiochemical Responses and Ecological Adaptations of Peach to Low-Temperature Stress: Assessing the Cold Resistance of Local Peach Varieties from Gansu, China.

In recent years, extreme weather events have become increasingly frequent, and low winter temperatures have had a significant impact on peach cultivation. The selection of cold-resistant peach varieties is an effective solution to mitigate freezing damage. To comprehensively and accurately evaluate the cold resistance of peaches and screen for high cold resistance among Gansu local resources, nine different types of peach were selected as test resources to assess physiological, biochemical, and anatomical indices. Subsequently, 28 peach germplasms were evaluated using relevant indices. The semi-lethal temperature (LT50) was calculated by fitting the change curve of the electrolyte leakage index (ELI) with the Logistic equation; this can be used as an important index for identifying and evaluating the cold resistance of peach trees. The LT50 values ranged from -28.22 °C to -17.22 °C among the 28 tested resources; Dingjiaba Liguang Tao exhibited the lowest LT50 value at -28.22 °C, indicating its high level of cold resistance. The LT50 was positively correlated with the ELI and malondialdehyde (MDA) content with correlation coefficients of 0.894 and 0.863, respectively, while it was negatively correlated with the soluble sugar (SS), soluble protein (SP), and free proline (Pro) contents with correlation coefficients of -0.894, -0.721, and -0.863, respectively. The thicknesses of the xylem, cork layer, cork layer ratio (CLR) and thickness/cortex thickness (X/C) showed negative correlations (-0.694, -0.741, -0.822, -0.814, respectively). Finally, the membership function method was used to evaluate cold resistance based on the ELI, MDA, Pro, SP, SS, CLR, and xylem thickness/cortex thickness (X/C) indices. The average membership degree among all tested resources ranged from 0.17 to 0.61. Dingjiaba Liguang Tao emerged prominently in terms of high-cold-resistance (HR) membership value (0.61).

THE EFFECT OF FRANGIPANI FLOWER (PLUMERIA ACUMINATA AIT) EXTRACT WITH GRANULE FORMULATION ON MORTALITY OF AEDES AEGYPTI LINN INSTAR III LARVAE

Dengue hemorrhagic fever is a disease transmitted through the bite of the Aedes aegypti mosquito and is widely found in Indonesia. The main key in dealing with Aedes aegypti mosquitoes is to control their spread and eradicate larvae. Vegetable larvicide frangipani flower extract formulated in granule form can be an alternative in vector control. The purpose of this study was to analyze the effect of frangipani flower (Plumeria acuminata Ait) extract with granule formulation as vegetable larvicide against Aedes aegypti Linn instar III larvae. The study was conducted in the laboratory of B2P2VRP Salatiga in 2015. The research method used was a pure experiment with 6 concentrations of 1.6%; 1.9%; 2.7%; 3.4%; 4.3% and 4.7% were accompanied by 4 repetitions. The total sample of larvae in the study amounted to 800 heads. Observations were made for 2,4,6 and 24 hours. Based on the results of study, the effective concentration of frangipani flower extract with granule formulation against the mortality of Aedes aegypti larvae is 4.7% because it is able to kill larvae 100%. The results of probit analysis obtained LC50 values of 1.572% and LC90 3.025%, while the LT50 value at an effective concentration of 4.7% was 2.902 or 3 hours and the LT90 value is 9.421 or 9 hours. The ANOVA test obtained p value = 0.000 (p<0.05). The results showed that there were significant differences in various concentrations of frangipani flower extract granules on the mortality of Aedes aegypti larvae. The conclusion was that the 4.7% concentration in the formulation of frangipani flower extract granule (Plumeria acuminata Ait) was effective as a vegetable larvicide

Insecticidal potential of Streptomyces sp. dichloromethane extracts against the cactus cochineal Dactylopius opuntiae (Cockerell)

Destructive damages caused by Dactylopius opuntiae (Cockerell) to cactus worldwide require an ecofriendly IPM approach. Streptomyces sp. produce wide range of biologically active secondary metabolites that can be an interesting alternative to chemical insecticides for pest control, as they are less toxic and easily biodegradable. The efficacy of dichloromethane extracts of four Moroccan Streptomyces sp. strains: Streptomyces bellus- E23-2, Streptomyces galilaeus- E23-9, Streptomyces africanus- E23-3, and Streptomyces bellus- E25-12 (applied at 11, 13, 15, 17 and 20 mg mL-1) against D. opuntiae nymphs and adult females was evaluated under laboratory and greenhouse conditions. Results showed that Streptomyces bellus- E23-2 and Streptomyces galilaeus- E23-9 dichloromethane extracts applied at 20 mg mL-1 were more effective, causing higher mortality against nymphs (92% and 91%, respectively) and adult females (90% and 95%, respectively) after 8 days of exposure, resulting in an LT50 value of 3.0 days (nymph), and 3.0 and 6.0 days (adult female), respectively. Streptomyces bellus- E25-12 extract had the lowest mortalities [88% (nymph) and 68% (adult female)]. In greenhouse experiment, the highest first instar nymph mortality was achieved by Streptomyces bellus- E23-2 (55.5%) and Streptomyces galilaeus- E23-9 (50.5%) dichloromethane extracts at 20 mg mL-1. The metabolites found in dichloromethane extracts of Streptomyces bellus- E23-2 and Streptomyces galilaeus- E23-9 show considerable potential to be used in the development of new biopesticide formulations for use in integrated pest management programs against D. opuntiae.

Bioefficacy of engineered Beauveria bassiana with scorpion neurotoxin, LqqIT1 against cotton mealybug, Phenacoccus solenopsis and cowpea aphid, Aphis craccivora.

Cotton mealybug, Phenacoccus solenopsis (Tinsley) and cowpea aphid Aphis craccivora (Koch) are notorious polyphagous, hemipteran sap sucking insect pests. A recombinant toxin gene 'LqqIT1' from the scorpion Leiurus quinquestriatus quinquestriatus (Ehrenberg) was cloned in the pAL1 fungal expression vector and then expressed in the entomopathogenic fungus Beauveria bassiana (Balasmo) using genetic modification techniques. The genetically transformed B. bassiana strain (BbLqqIT1-3) and its un-transformed parent strain (Bb-C) were screened to infect the third instar nymphs of P. solenopsis and first instar nymph of A. craccivora through leaf treatment and topical application (spray) method at 1 * 107 spores per ml concentration. The recombinant strain BbLqqIT1-3 was highly pathogenic against A. craccivora but non pathogenic to P. solenopsis. BbLqqIT1-3 induced 72 and 43.33% mortality in A. craccivora nymphs 96 h after leaf treatment and topical application, respectively. The nymphs of A. craccivora infected with BbLqqIT1-3 displayed classical neurotoxic symptoms such as sluggishness, solublize and liquification of the body. Crude soluble toxin protein, BbLqqIT1a-CSE and Bb-WT-CSE was extracted from the BbLqqIT1-3 and Bb-C, respectively using ammonium sulphate precipitation method, and their oral toxicity was analyzed at 5 µg/ml concentration. The survival of the studied insects was negatively affected by the crude soluble toxin extracts. The LT50 values of BbLqqIT1a-CSE against P. solenopsis and A. craccivora were 22.18 and 17.69 h, respectively. Exposure to crude soluble toxin extracts also accounted for the imbalance of ionic concentrations in the hemolymph of treated insects such as hyperpotassemia (3.53-8.18 meq/ml) in the P. solenopsis and hypopotassemia (7.52-0.47 meq/ml) in A. craccivora. The transformed fungus BbLqqIT1-3 strain exhibited promising results in invitro study.

Ovicidal and Pediculicidal Activity of Indigofera suffruticosa Mill. Leaf Oil on Pediculus humanus capitis Egg to Adult Stages.

Pediculosis capitis, commonly known as head lice infestation, represents a significant health 26 problem for school children worldwide. Repeated and long-term usages of highly toxic pediculicides have resulted in the development of increased levels of resistance and do not kill louse eggs. Alternative pediculicides, such as herbal products, have recently been proposed for the treatment of head lice infestation, thereby decreasing toxicity. This study analyzed the chemical composition of I. suffruticosa leaf extracts using GC-MS and evaluated the effects of Indigofera suffruticosa Mill. (I. suffruticosa) leaf extract on the mortality of head lice and their eggs. The major five components of the tested oils identified were as follows: n-hexadecanoic acid, hexadecanoic acid, ethyl ester, oleic acid, (E)-9-octadecenoic acid ethyl ester, and linoleic acid ethyl ester. The effective pediculicide of the I. suffruticosa leaf extracts affected head lice in all stages (egg, nymph, and adults). The concentrations of I. suffruticosa leaf extracts at 500mg/mL produced the highest effective ovicidal on egg with 96.6% unhatching and pediculicide on nymphs and adults with 96.7 ± 5.7% and 86.7 ± 5.7% mortality, respectively, at 60min (LT50 value < 10min). The analysis of the external structure of the adult-stage head lice by SEM examination revealed that dead lice exposed to I. suffruticosa leaf extract displayed damage to the outer smooth architecture and obstructed the respiratory spiracles. We may conclude that the application of I. suffruticosa leaf extract produces an effective herbal pediculicide capable of affecting all stages of head lice.

The effect of two isolates of Beauveria bassiana (Bals.) Vull. on the larvae of confused flour beetle [Tribolium confusum du Val., 1863 (Coleoptera: Tenebrionidae)

The confused flour beetle cause economic losses in stored products, especially in products obtained from wheat. Although using insecticides against storage pests is an effective method, their frequent and continuous use can lead to resistance and toxicity issues in non-target organisms. In this study, the effect of local Beauveria bassiana isolates (BMAUM LD.2016 and BMAUM M6-4) on the 3rd instar larvae of confused flour beetle (Tribolium confusum) was determined under laboratory conditions. As a result of the experiment, both isolates of B. bassiana were found to be more effective on the larvae in the spraying method compared to the dipping method. In the spraying method, mortality rates on the 9th day were 72% in BMAUM LD.2016 isolate, 34% in the dipping method, respectively. Mortality rates of BMAUM M6-4 isolate were recorded as 96% in the spraying method and 8% in the dipping method. In the spraying method, the mortality date (LT50) was determined as 6.09 days for BMAUM LD.2016 isolate and 3.90 days for BMAUM M6-4 isolate. The LT50 value could not be calculated in the dipping method, since the mortality rates were below 50% for both isolates. BMAUM M6-4 isolate caused higher mortality in larvae than BMAUM LD.2016 isolate. As a result, B. bassiana isolates have shown a high level of effectiveness against T. confusum, demonstrating that they can be used as isolates for insect control.

Uji Efikasi Berbagai Konsentrasi Insektisida Nabati Buah Majapahit (Aegle marmelos L. Correa) terhadap Mortalitas Hama Uret Tanaman Kelapa (Oryctes rhinoceros L.)

A type of insect that causes a decline in coconut production is the uret pest of coconut (Oryctes rhinoceros L.). The vegetable pesticide of the majapahit fruit is one of several techniques for controlling pests. This study was carried out from April to July 2022 at the Plant Protection Laboratory of the Department of Agricultural Production, Jember Country Polytechnic. The goal of this investigation was to determine the impact of the majapahit vegetable pesticide on the death of the uret pest of coconut plants. This study employed a non-factorial randomized block design (RBD) with four treatments and six replications, namely control, 50%, 60%, and 70% majapahit fruit extract.. The experimental data were examined using ANOVA; if the findings indicated a significant influence, a 5% stage LSD similarly check was carried out, along with the determination of LT50 using probit analysis. Mortality, physical changes, and LT50 are the key factors. The results showed that the majapahit fruit's natural insecticides had a significant impact on the death of the coconut plant's ureth pest, with the LT50 value at a concentration of 70% majapahit fruit extract reaching its lowest point in 178 hours.

Efektivitas Konsentrasi Biopestisida Asap Cair Tandan Kosong Kelapa Sawit (Elaeis guineensis Jacq.) terhadap Mortalitas Hama Uret Tebu (Lepidiota Stigma F.)

Indonesia’s The sugarcane white grub (Lepidiota stigma F.) is one of the pests that causes a decrease in sugarcane production. There are several ways to control pests, one of which is using biopesticide made from the liquid smoke of empty oil palm bunches. This research was conducted in January-February 2023 at the Plant Protection Laboratory of the Department of Agricultural Production at Jember State Polytechnic. The aim of this study was to determine the effectiveness of different concentrations of biopesticide made from the liquid smoke of empty oil palm bunches in controlling the sugarcane white grub. The study used a randomized block design (RBD) consisting of four treatments with six replications, namely 1% concentration, 1.5% concentration, 2% concentration, and 2.5% concentration of biopesticide made from the liquid smoke of empty oil palm bunches. The data were analyzed using ANOVA, and if significant effects were found, further analysis was conducted using the Tukey test at a significance level of 5%. The LT50 was determined using probit analysis. The parameters used were mortality, physical changes, and LT50. The results showed that the biopesticide made from the liquid smoke of empty oil palm bunches had a highly significant effect on the mortality of the sugarcane white grub, with the fastest LT50 value of 98 hours at a concentration of 2.5%.

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.

Pathogenecity testing of indigenous Bacillus thuringiensis isolates against chickpea pod borer, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Ethiopia

Helicoverpa armigera (Hübner) is the most significant insect pest of chickpea in Ethiopia. Sole reliance on insecticide causes both human and environmental health problems. A common soil bacterium, Bacillus thuringiensis used as a bioinsecticide to control numerous Lepidopteran larvae. Therefore, indigenous isolates were collected, screened, tested for pathogenicity against H. armigera with a reference Bacillus. var. thuringiensis. From 121 soil samples collected, 23 Bacillus species were isolated and purified. Bt index ranged from 0.33 to 1.00 and the mean was 0.73 average Bt index. Absorbance values ranged from 0.46 to 0.98. Screening biotoxicity assay was conducted at the rate of 1 mL against 3rd instar larvae of H. armigera. Experiments were replicated three times; ten larvae were used per replicate and reputed thrice. Ten indigenous Bt isolates were screened based on larval mortality which ranged between 27.78% and 75.83% and LT50 values of 45.71–143.9 h. The highest mortality of 75.83% and LT50 of 45.71 h was recorded from reference Bt followed by indigenous Bt isolate KDL with mortality percentage of 69.16% and LT50 of 48.49 h. Statistically no significant difference was observed among the tested bacterial isolates. Biotoxicity assay was conducted at five concentrations ranging from 0.25 to 2 mL. The LD50 and LD 90 values were 0.84–1.24 mL and 1.54–1.98 mL, respectively. The lowest LD50, 90 of 0.84 mL and 1.54 mL were recorded from KDL Bt isolate compared to reference Bt whose LD50 and LD90 were 0.84 mL and 1.66 mL. Results of Bt growth under varied values of temperature ranged from 15oC to 40 °C. All the Bt isolates showed growth at all the values of the tested temperatures with steady growth from 15 °C to 20 °C and uniform growth observed from 20 °C to 30 °C. After 35 °C, the growth of all the Bt isolates declined indicating that 30 °C–35 °C is the optimum growth temperature range. Protein content ranged from 0.43 to 0.97 (mg/mL). However, protein content and larval mortality was not linearly correlated. It was concluded that all the tested indigenous Bacillus isolates were virulent enough and identified as a promising candidate bioinsecticide against H. armigera. Hence, recommended for further intensive evaluations under greenhouse and field trails.

Analisis filogenetik Hyposidra talaca nucleopolyhedrovirus (HytaNPV) yang diisolasi dari perkebunan teh Gunung Mas, Bogor, Jawa Barat dan virulensinya terhadap Hyposidra talaca Walker

Hyposidra talaca (Walker) is an important pest of tea plant. H. talaca can cause losses of between 40–100% in the dry season if proper control is not carried out. H. talaca has natural enemies such as predators, parasitoids, and pathogens. One of the entomopathogens is NPV. This study aims to obtain molecular characteristics through DNA polymerase sequences and determine the virulence level of NPV isolates from H. talaca. The same species from different locations can have genetic variability. Therefore, molecular characterization by polymerase chain reaction (PCR) on DNA polymerase sequences is one way to study the genetics of HytaNPV. NPV was isolated from infected H. talaca larvae collected from the field. The DNA isolates were used as templates for PCR for DNA polymerase gene amplification with an amplicon target of ±1,000 bp. A sequencing process followed the PCR provides nucleotide sequence. HytaNPV DNA polymerase sequencing results were aligned with GenBank's BLAST data to provide information on the relationship of HytaNPV to NPVs isolated from other regions. Based on molecular character analysis using DNA polymerase gene sequence, HytaNPV Bogor has a homology level of 93.9% with HytaNPV isolated from India. HytaNPV Bogor has a genetic relationship with the NPV that infects Buzura suppressaria from China and Australia. HytaNPV Bogor is similar to the NPV that infects H. talaca from India. The bioassay of HytaNPV isolate against H. talaca showed the highest LT50 value of 1.92 days was found in concentration of 1.58 x 107 POBs/ml in second instar larvae.

EFFECTIVENESS OF HIGH TEMPERATURES AGAINST CALLOSOBRUCHUS MACULATUS (Coleoptera: Bruchidae) ADULTS

Pulse beetle, Callosobruchus maculatus is a worldwide severe pests of pulse grains in the storage conditions. Considering the negative consequences of synthetic chemicals used against C. maculatus, effectiveness of various high temperatures were evaluated against it under lab conditions. The Classic® 1080 series laboratory oven (HT Company (Ilford) Ltd. UK) was used to get the desired temperatures of 40, 45, 50, 55, and 60ºC. Five pairs of freshly emerged C. maculatus adults were placed with twenty cowpea seeds in a petri dish were used for each temperature regime for five exposure times i.e., 10, 20, 30, 40, and 50 minutes. Data on adult mortality was observed after 24-hours. Results confirmed the effective of high temperatures against adult C. maculatus as 100% mortality of the targeted adults was recorded within 10 minutes at 60°C, whereas it took 40- and 50-minutes to kill 100% of the adults at 55 and 50°C, respectively. The LT50 values of required temperature against C. maculatus at various exposure timings ranged between 43.544°C at 50 minutes exposure to 48.994°C at 10 minutes exposure, whereas overall minimum and maximum fiducial limits for LT50 temperatures were ranged between 42.845 to 49.655°C. No negative impact of high temperatures was also recorded on the germination percentage of cowpea seeds as germination success recorded at various high temperatures was not significantly different from the control cowpea seeds.

Isolation, Identification and Evaluation of the Effects of Native Entomopathogenic Fungi from Côte d'Ivoire on Galleria mellonella.

The fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a polyphagous pest highly damaging to maize and other food crops in Africa, particularly in Côte d'Ivoire. Chemical pesticides not only have often proved to be unsuccessful, but cause adverse effects on the environment and human health; therefore, entomopathogenic fungi could represent an alternative biocontrol solution. Against this background, fungi were isolated from soil samples collected in maize fields in three regions of Côte d'Ivoire, by the methods of soil dilution and baiting with Galleria mellonella. The resulting 86 fungal isolates were phenotypically and genetically identified. The pathogenicity of seven isolates of Metarhizium spp., three isolates of Beauveria bassiana and two isolates of Trichoderma sp. was evaluated on fifth instar larvae (L5) of G. mellonella. Larval mortality rates and the median lethal time (LT50) were determined seven days after inoculation for each of these selected isolates. The median lethal concentration (LC50) was determined for a selection of isolates. Beauveria bassiana isolate A214b was the most effective, causing 100% mortality, with an LT50 of 2.64 days and an LC50 of 1.12 × 104 conidia mL-1. Two other promising isolates, A211 and A214a, belonging to B. bassiana, caused 100% mortality with LT50 values of 3.44 and 4.04 days, respectively. Mortality caused by Metarhizium isolates varied from 65.38% to 100%, with Metarhizium anisopliae isolate T331 causing 100% mortality with an LT50 of 3.08 days at an LC50 of 3.33 × 104 conidia mL-1. Trichoderma sp. isolates were the least pathogenic ones. Beauveria bassiana and Metarhizium isolates showed to be virulent against the model Lepidopteran G. mellonella and will be tested on S. frugiperda.

Effect of thermal acclimation on the tolerance of the peach fruit fly (Bactrocera zonata: Tephritidae) to heat and cold stress

Understanding the thermal biology of insects is of increasing importance for predicting their geographic distribution, particularly in light of current and future global temperature increases. Within the limits set by genetic makeup, thermal tolerance is affected by the physiological conditioning of individuals (e.g., through acclimation). Considering this phenotypic plasticity may add to accurately estimating changes to the distribution of insects under a changing climate.We studied the effect of thermal acclimation on cold and heat tolerance of the peach fruit fly (Bactrocera zonata) – an invasive, polyphagous pest that is currently expanding through Africa and the Middle East. Females and males were acclimated at 20, 25 and 30 °C for up to 19 days following adult emergence. The critical thermal minimum (CTmin) and maximum (CTmax) were subsequently recorded as well adult survival following acute exposure to chilling (0 or −3 °C for 2 h). Additionally, we determined the survival of pupae subjected for 2 h to temperatures ranging from −12 °C to 5 °C.We demonstrate that acclimation at 30 °C resulted in significantly higher CTmax and CTmin values (higher heat resistance and lower cold resistance, respectively). Additionally, adult recovery following exposure to −3 °C was significantly reduced following acclimation at 30 °C, and this effect was significantly higher for females. Pupal mortality increased with the decrease in temperature, reaching LT50 and LT95 values following exposure to -0.32 °C and −6.88 °C, respectively. Finally, we found that the survival of pupae subjected to 0 and 2 °C steadily increased with pupal age.Our findings substantiate a physiological foundation for understanding the current geographic range of B. zonata. We assume that acclimation at 30 °C affected the thermal tolerance of the flies partly through modulating feeding and metabolism. Tolerance to chilling during the pupal stage probably changed according to temperature-sensitive processes occurring during metamorphosis, rendering younger pupae more sensitive to chilling.

ANTI-SCHISTOSOMA EFFICACY OF Occimum gratissimum (SCENT LEAF) AND Andrographis paniculata (KING OF BITTERS) AGAINST Schistosoma haematobium CERCARIA

Anti-schistosomal effect of crude aqueous extract of Occimum gratissimum (scent leaf) and Andrographis paniculata (king of bitters) on Schistosoma haematobium were cercaricidally evaluated over a period of 2 hours (h). The mortality of the cercaria was dose and time dependent. At 100 milligram per milliliter (mg−mL), O. gratissimum and A paniculata exhibited 100% mortality. Statistically, extract concentrations (F = 53.55; P= 0.004) and plant species (F = 10.13; P = 0.049) had significant (p < 0.05) effect on cercaria mortality. Pearson correlation coefficient (R) analysis showed that the results of cumulative mean cercariae mortalities and exposure time were strongly correlated for both plants. Probit analysis, lethal concentration (LC50) of O. gratissimum and A. paniculata against S. haematobium cercaria was 41.50 and 44.10 mg−mL respectively. The median lethal time (LT50) values for O. gratissimum and A. paniculata extract concentrations at 120 minutes treatment implicated 100.0 mg−mL to be the most toxic concentration which generated an LT50 value of 50.47 and 55.0 minutes respectively. While the least effective concentration of A. paniculata was 25.0 mg−mL requiring 115.03 minutes to cause 50% mortality of cercariae. From the study, it can be deduced that O. gratissimum and A. paniculata elicited varying degree of anti-schistosomal properties at all concentrations against S. haematobium. S. haematobium cercariae were more susceptible to toxic effects of O. gratissimum leaf extracts than A. paniculata. Cultivation of these plants along river banks will help in controlling cercariae and possibly miracidia in endemic areas by way of leave shedding since these plants are hydrophilic, biodegradable, readily available and less laborious to cultivate.

Efektivitas Isolat Nematoda Entomopatogen Steinernema sp. Produksi PPAH Kabupaten Kediri terhadap Mortalitas Larva Spodoptera frugiperda J. E. Smith

Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) is a pest that has just entered Indonesia since 2019 and has adapted and become an important pest in corn plants. Therefore, we need a control by utilizing biological control agents that exist in nature, one of which is the entomopathogenic nematode type Steinernema sp. which has been developed by the Biological Agent Service Post (PPAH) "Sidodadi" in the Plosoklaten District, Kediri Regency. The methods used in this study were: collection and rearing of S. frugiperda pests; breeding of entomopathogenic nematodes Steinernema sp. in vivo. The application of an entomopathogenic nematode to test pathogenicity against 3rd instar S. frugiperda larvae. The application treatments used were population densities of 1.000 JI/ml, 800 JI/ml, 400 JI/ml, 200 JI/ml plus a control treatment. The study was designed with a single Completely Randomized Design (CRD) with six treatments and was repeated four times. Each replication consisted of 10 S. frugiperda larvae. Parameters observed included mortality of S. frugiperda larvae due to Steinernema sp.. Effectiveness of Steinernema sp. by calculating the LT50 value. Observation of biological symptoms of S. frugiperda infected with Steinernema sp. and calculation of the infection rate of Steinernema sp.. Data from observations were analyzed using a 5% ANOVA. If there is a significant difference, further DMRT testing is carried out. The effectiveness test was carried out by calculating the LT50 value using Finney's (1971) probit analysis. Based on observations for 120 hours, it was shown that entomopathogenic nematode PPAH isolate was effective in killing S. frugiperda larvae. PPAH isolate entomopathogenic nematode was effective in causing mortality in S. frugiperda larvae. The highest mortality value of S. frugiperda due to entomopathogenic nematode treatment was 97.5% in treatment with 800 JI/ml and 1000 JI/ml at 120 hours after application observation. The fastest LT50 value causing mortality in S. frugiperda larvae was in the 1000 JI/ml of 32.60 hours. The treatment with the longest LT50 value caused the mortality of 50% of the test insects, namely the 200 JI/ml over 95.88 hours. Observation of the infection rate showed the highest infection rate was found in the 1000 JI/ml at 24 hours after application with as many as 0.02% tails, this is because that the higher the inoculated entomopathogenic nematode population, the higher the infection rate value.