Fumigant Insecticide Research Articles

Modeling the Efficacy of Phosphine on Eggs of Major Stored-Product Insect Species: Investigating Strains with Varying Susceptibility Levels

Phosphine is a widely utilized fumigant insecticide in stored-product facilities; however, its excessive application and improper usage have contributed to the emergence of resistance in insect populations. Although phosphine resistance is globally recognized, limited studies address its effects across different developmental stages. This research investigates the efficacy of phosphine on the eggs of major stored-product pests, including Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), Tribolium castaneum, and T. confusum (Coleoptera: Tenebrionidae), focusing on strains with varying levels of phosphine susceptibility. Egg hatching rates were analyzed following exposure to phosphine concentrations ranging from 50 to 1000 ppm for durations of 1 to 7 days. Predictive models were constructed to correlate phosphine concentration and exposure time, facilitating the determination of optimal pest control strategies. The findings reveal significant differences in efficacy among species and strains, with eggs from susceptible strains experiencing complete hatch failure at 50 ppm, while resistant strains showed higher tolerance. Lethal time (LT50 and LT99) values were determined, with LT99 ranging from 6.91 to 12.95 days at 50 ppm, highlighting species-specific and age-related differences in phosphine susceptibility. Lethal concentration (LC50 and LC99) values could only be estimated for T. castaneum, with LC99 for 1-day-old eggs ranging from 773.67 ppm to 923.03 ppm after 2.5 days of exposure. Furthermore, egg age influenced susceptibility, with 2-day-old eggs exhibiting greater mortality compared to 1-day-old eggs. This study underscores the critical role of phosphine concentration, exposure duration, and developmental stage in resistance management, providing valuable insights for enhancing fumigation protocols and improving the control of stored-product pests.

Sublethal phosphine fumigation induces transgenerational hormesis in a factitious host, Corcyra cephalonica.

The rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) is a pest of stored grains and widely used as a factitious host during the mass rearing of several natural enemies of crop pests. Hormesis is well-documented in pest insects, to some extent in natural enemies of pests. We report transgenerational stimulatory effects of the widely used fumigant, phosphine. The study reports the consequences of sublethal, low lethal and median lethal concentrations (LC5 , LC25 and LC50 ) and untreated control for two sequential generations of the species (G1 to G2 ). In this study, we investigated the life-history traits, nutrient reserves (protein, lipid and carbohydrate) and larval gut microbiome (using 16 s rRNA V3-V4 metagenomics sequencing) of C. cephalonica. Stimulatory effects were observed for various biological traits of C. cephalonica, notably adult longevity, emergence and increased egg hatchability when exposed to LC5 of phosphine. The total protein, lipid and carbohydrate contents of C. cephalonica also were found to be significantly increased by LC5 in both generations. The microbial diversity of LC5 treated larval gut was higher and found to be different from the rest of the treatments. This is the first report showing hormesis to a fumigant insecticide. Our findings increase knowledge on the interaction between hormesis, nutrient reserves and gut bacteria in C. cephalonica exposed to insecticides. Overall, the present study establishes phosphine-induced hormesis at LC5 in the host C. cephalonica, which might help improve the quality of mass rearing of various natural enemies. © 2023 Society of Chemical Industry.

Towards a Miniaturized Photoacoustic Detector for the Infrared Spectroscopic Analysis of SO2F2 and Refrigerants

Sulfuryl fluoride (SO2F2) is a toxic and potent greenhouse gas that is currently widely used as a fumigant insecticide in houses, food, and shipping containers. Though it poses a major hazard to humans, its detection is still carried out manually and only on a random basis. In this paper, we present a two-chamber photoacoustic approach for continuous SO2F2 sensing. Because of the high toxicity of SO2F2, the concept is to use a non-toxic substituent gas with similar absorption characteristics in the photoacoustic detector chamber, i.e., to measure SO2F2 indirectly. The refrigerants R227ea, R125, R134a, and propene were identified as possible substituents using a Fourier-transform infrared (FTIR) spectroscopic analysis. The resulting infrared spectra were used to simulate the sensitivity of the substituents of a photoacoustic sensor to SO2F2 in different concentration ranges and at different optical path lengths. The simulations showed that R227ea has the highest sensitivity to SO2F2 among the substituents and is therefore a promising substituent detector gas. Simulations concerning the possible cross-sensitivity of the photoacoustic detectors to H2O and CO2 were also performed. These results are the first step towards the development of a miniaturized, sensitive, and cost-effective photoacoustic sensor system for SO2F2.

Ozone reduces lifespan and alters gene expression profiles in Rhyzopertha dominica (Fabricius).

Rhyzopertha dominica is one of the most important stored grain pests that seriously damage rice and wheat. At present, the method of controlling stored grain pests mainly relies on insecticide fumigation. However, the excessive use of pesticides not only leaves pesticide residues, with harmful effects on human health and the environment, but also induces insect resistance. Ozone is a strong oxidant with the characteristics of easy decomposition and without residue. Although ozone has been widely used in the food industry in recent years, research on the control of stored grain pests is limited. In this research, we used ozone treatment to control R. dominica adults and explore the molecular mechanisms that affect them. Here, we found that ozone treatment on R. dominica adults could decrease life span and increase malondialdehyde (MDA) content, as well as reduce activity of total superoxide dismutase (SOD) and catalase (CAT). Using RNA-seq technology, we identified 641 genes that were differentially expressed between ozone-treated and control R. dominica adults [fold-change of ≥ 2 (q-value < 5%)]. When comparing ozone treatment with control R. dominica adults, 330 genes were significantly upregulated and 311 were downregulated. RT-qPCR confirmed that 11 genes were differentially expressed in ozone-treated and control R. dominica adults. These genes were involved in insect cuticle protein and antioxidant system. This research showed that ozone treatment could reduce the lifespan of R. dominica through antioxidant system. It is an environmentally benign method for the control of stored grain pests and has great development potential.

A chromosome-level genome of the booklouse, Liposcelis brunnea, provides insight into louse evolution and environmental stress adaptation.

BackgroundBooklice (psocids) in the genus Liposcelis (Psocoptera: Liposcelididae) are a group of important storage pests, found in libraries, grain storages, and food-processing facilities. Booklice are able to survive under heat treatment and typically possess high resistance to common fumigant insecticides, hence posing a threat to storage security worldwide.ResultsWe assembled the genome of the booklouse, L. brunnea, the first genome reported in Psocoptera, using PacBio long-read sequencing, Illumina sequencing, and chromatin conformation capture (Hi-C) methods. After assembly, polishing, haplotype purging, and Hi-C scaffolding, we obtained 9 linkage groups (174.1 Mb in total) ranging from 12.1 Mb to 27.6 Mb (N50: 19.7 Mb), with the BUSCO completeness at 98.9%. In total, 15,543 genes were predicted by the Maker pipeline. Gene family analyses indicated the sensing-related gene families (OBP and OR) and the resistance-related gene families (ABC, EST, GST, UGT, and P450) expanded significantly in L. brunnea compared with those of their closest relatives (2 parasitic lice). Based on transcriptomic analysis, we found that the CYP4 subfamily from the P450 gene family functioned during phosphine fumigation; HSP genes, particularly those from the HSP70 subfamily, were upregulated significantly under high temperatures.ConclusionsWe present a chromosome-level genome assembly of L. brunnea, the first genome reported for the order Psocoptera. Our analyses provide new insights into the gene family evolution of the louse clade and the transcriptomic responses of booklice to environmental stresses.

Toxicity of Five Plant Volatiles to Adult and Egg Stages of Drosophila suzukii Matsumura (Diptera: Drosophilidae), the Spotted-Wing Drosophila.

The environmental impact of methyl bromide (MB) has resulted in its phase out as an insecticidal fumigant except for critical use exempted categories. Consequently, there is an urgent need to develop an environmentally sustainable MB alternative fumigant. trans-Cinnamaldehyde (TC), benzaldehyde, allyl isothiocyanate (AITC), hexanal, and ethyl formate (EF) are naturally occurring plant volatiles with insecticidal properties. This study assessed the toxicity of these plant volatiles to adult and egg stages of the spotted-wing drosophila (SWD) (Drosophila suzukii Matsumura). The plant volatile treatments had a significant effect on adult SWD mortality. The descending order of toxicity to adult SWD was benzaldehyde > AITC > TC > hexanal > EF at a headspace concentration of 0.50 μL/L air for 24 h. All the volatiles, at a concentration of 4.00 μL/L air, significantly inhibited larval emergence from SWD eggs in artificial diet compared to the control. At a 0.50 μL/L air level, among the volatiles tested, only AITC exhibited 100% inhibition against larval emergence from SWD eggs in blueberry fruits after 24 h exposure. In summary, this study shows that all volatiles tested elicited varying degrees of toxicity toward SWD adults and eggs. However, AITC was the most efficacious volatile and the one with the greatest promise as a post-harvest fumigant for both adult and egg stages of SWD.

Repellent and insecticidal effects of essential oils of Petroselinum crispum (Mill.) Fuss and Pimenta racemosa var. racemosa (Mill.) J.W. Moore leaves on Dinoderus porcellus Lesne (Coleoptera: Bostrichidae)

Essential oils from leaves of Petroselinum crispum (Mill.) Nym. ex AW HillFuss (Apiaceae) and Pimenta racemosa var. racemosa (P. Mill.er) J.W. Moore (Myrtaceae) were evaluated for their repellent properties, insecticidal and fumigant activities against Dinoderus porcellus Lesne (Coleoptera: Bostrichidae). The essential oils of these plants were obtained by Clevenger-type hydro distillation method with yield of 0.47 and 1.09% w/w for P. crispum and P. racemosa, respectively. Essential oils of both plants exhibited a low repellent activity (class I and II of repellency) against D. porcellus at all tested concentrations. The P. crispum and P. racemosa essential oils were toxic to D. porcellus in contact, ingestion and fumigant assays. The D. porcellus adults were more susceptible to contact action of P. crispum (LD50 = 1.15 µL/adult) than P. racemosa (LD50 = 414.38 µL/adult) at 72 h, whereas in ingestion assay, P. crispum essential oil was the most effective toxin (LC50 = 3.88 µL/g) at 21 days interval time. Strong feeding deterrence (68.97%) was achieved in D. porcellus adults by using P. crispum essential oil at a concentration of 0.4 µL/g of yam chips. In the fumigation assays, P. crispum (LC50 = 7.22 µL/L air) essential oil was more toxic than P. racemosa (LC50 = 3.39×106 µL/L air) against D. porcellus adults within 7 days. These findings, suggest that P. crispum essential oil was more active against D. porcellus adults and showed its potential for development as natural anti-feeding agent, and fumigant insecticide for managing D. porcellus adults in stored yam chips. Key words: Contact Contact toxicity, Feeding feeding deterrence, Fumigant fumigant toxicity, Repellent repellent activity, Storage storage insects.

English

Post-harvest losses of agricultural produce caused by store grain pest most especially cereals and grains to store pest require developing cheap, ecofriendly and readily available insecticide to combat this threat and achieve the goal of food security in developing countries. This study investigated the effects of Cleistopholis patens (leaf and stem bark) on Plodia interpunctella infestation in stored maize grains. Powders from the plant were administered at 0.5, 1.0, 1.5, 2.0 and 2.5 g dosages to maize grains containing developmental stages of P. interpunctella both as contact and fumigant insecticides. The insecticidal activities were monitored at 24, 48, 72 and 96 h post-treatment periods. As a contact insecticide, C. patens was significantly (PË‚0.05) more effective than as a fumigant against all developmental stages of the pest. The leaf powder was observed to be weakly effective both as contact and fumigant against P. interpunctella. At its peak, 69.17% larval mortality was achieved at 2.5 g dosage after 96 h exposure, but 1.5 g dosage of the stem bark achieved 0% egg hatchability and 100% larval and adult mortalities at the same length of exposure. Inferences from these results suggest that the plant has some bioactive constituents which if properly harnessed can be co-opted into integrated management of P. interpunctella infesting stored products. Key words: hatchability, contact, fumigant, bioactivity, Indian meal moth and post- treatment.

Transcriptomic analysis of s-methoprene resistance in the lesser grain borer, Rhyzopertha dominica, and evaluation of piperonyl butoxide as a resistance breaker

BackgroundThe lesser grain borer, Rhyzopertha dominica is a serious pest of stored grains. Fumigation and contact insecticides play a major role in managing this pest globally. While insects are developing genetic resistance to chemicals, hormonal analogues such as s-methoprene play a key role in reducing general pest pressure as well as managing pest populations that are resistant to fumigants and neurotoxic contact insecticides. However, resistance to s-methoprene has been reported in R. dominica with some reports showing a remarkable high resistance, questioning the use of this compound and other related analogues in grain protection. The current study attempts to identify possible molecular mechanisms that contribute in resistance to s-methoprene in R. dominica.ResultsTranscriptome analysis of resistant and susceptible strains of this pest species identified a set of differentially expressed genes related to cytochrome P450s, indicating their potential role in resistance to s-methoprene. Laboratory bioassays were performed with s-methoprene treated wheat grains in presence and absence of piperonyl butoxide (PBO), a cytochrome P450 inhibitor. The results indicate that PBO, when applied alone, at least at the concentration tested here, had no effect on R. dominica adult emergence, but has a clear synergistic effect to s-methoprene. The number of produced progeny decreased in presence of the inhibitor, especially in the resistant strain. In addition, we also identified CYP complement (CYPome) of R. dominica, annotated and analysed phylogenetically, to understand the evolutionary relationships with other species.ConclusionsThe information generated in current study suggest that PBO can effectively be used to break resistance to s-methoprene in R. dominica.

Ecomore 2 project in Cambodia: Integrated vector management for dengue vectors in schools in an entomological/epidemiological approach

Background: In Cambodia, recent results showed very high resistance of Aedes aegypti to temephos, the only larvicide used in Cambodia, and two adulticides (permethrin used for net treatment, and deltamethrin for insecticide fumigation). The Ecomore2 project in Cambodia aims to estimate the effectiveness of an integrated vector management (IVM) targeting schools combined with an educational program to mitigate peaks of dengue and dengue-like syndromes (DLS) for reducing subsequent overcrowding of health centers. Methods and materials: A cluster randomized controlled trial was implemented in 24 clusters (12 under integrated vector control and 12 without), each including one school, with an active surveillance of DLS in neighboring villages. Our research program was also implemented to determine if an IVM could decrease the number of Ae. aegypti mosquitoes in schools by using Bacillus thruringiensis var. israelensis as a larvicide, pyriproxyfen for the dissemination of insect growth regulator larvicide and spores of Beauveria bassiana for slowly killing adults; all these methods were combined with education and sensitization of children. Results: Monitoring of mosquito populations during the first year showed the presence of at least 58 mosquito species, including dengue virus vectors such as Ae. aegypti and Ae. albopictus, but also vector species of Plasmodium spp., and Japanese encephalitis, Rift Valley Fever, West Nile Fever, Zika, Chikungunya and Ross River viruses. Ae. aegypti and Ae. albopictus were present in all 24 schools. There was no difference in the relative abundance of Ae. aegypti and Ae. albopictus between the clusters before the intervention. In parallel, epidemiological data neither showed any baseline difference of DLS. Entomological data following IVM showed a decrease of 50% of Ae. aegypti relative abundance in treated clusters compared to untreated clusters. The latter showed an average relative abundance of Ae. aegypti similar to the first year. The difference for Ae. albopictus relative abundance was not significant between the 2 areas. Epidemiological final data analysis are in progress, but will be presented for the ICID conference. Conclusion: In conclusion, the IVM decreased the Dengue vectors in schools in Cambodia. The epidemiological results of dengue incidence in the 2 clusters will be discussed during the conference.

Efficacy of ethylenesulphonyl fluoride against stored grain psocids, Liposcelis bostrychophila Badonnel and Liposcelis entomophila (Enderlein)

Phase-out, impending ban, and developing insect resistance to the commonly used insecticides for stored grains pose serious challenges to the scientific community and it is imperative to develop effective pest management strategies. Identification and testing of new compounds are potential options to deal with the growing threat. Ethylenesulphonyl fluoride (ESF), a new synthetic compound, is one of the most promising alternative fumigant insecticides that can be used to control the insect pests in stored-grains. However, limited evidence is available to support its efficacy to control the stored-product psocids. This study evaluates the ESF as a prospective control reagent to exterminate different life stages of the psocids Liposcelis bostrychophila Badonnel and L. entomophila (Enderlein). We conducted a 4 h toxicity trials and 12 h simulated efficacy trials with adults of the two species in wheat. Adults and nymphs were highly susceptible to ESF. Complete adult and nymph mortality (LD99) was also recorded at dosages ranged from 1.97 μL/L to 3.80 μL/L. Moreover, complete (LD99) egg mortality was recorded at dosages between 3.59 μL/L and 7.60 μL/L. Remarkably, the mortality of adults decreased with increasing depth of the grain bulk. Our study establishes ESF as a potential reagent that can be used effectively to control a variety of commonly known stored grain psocids.

Efficacy of bioactive compounds and their association with different cowpea cultivars against their major stored pest.

Stored grain insects are controlled with fumigant insecticides which can select resistant insect populations and cause environmental and applicator contamination. Thus, resistant cultivars and chemical constituents of essential oils are an alternative to the almost exclusive use of these insecticides. The effects of the combination of cowpea cultivars Vigna unguiculata (L.) Walp. with chemical constituents of essential oils against Callosobruchus maculatus were determined. Four cowpea cultivars: BRS Tracuateua, BR 17 Gurgueia, Epace 10 and Sempre Verde (insect rearing) untreated were used in the experiments and combined with chemical constituents of essential oil: eugenol, geraniol and trans-anethole. The biological parameters observed were: total egg number and eggs per grain, egg viability (%), insects emerged and insects per grain, immature stage viability (%), instantaneous rate of growth (ri), insect dry weight (mg), grain weight loss (%) and egg-adult period. When comparing all biological parameters, the cultivars BRS Tracuateua and BR 17 Gurgueia were harmful to C. maculatus. In the toxicity tests, the results showed that LC30 and LC50 of the chemical constituents ranged from 54.77 to 103.48 ppm and 60.99 to 125.18 ppm, respectively. In most of the biological parameters, LC50 had adverse effects significantly higher than LC30 and BR 17 Gurgueia treated were harmful to C. maculatus. Overall, the findings showed that BR 17 Gurgueia combined with eugenol and geraniol more significantly affected the biological parameters of C. maculatus than when associated with trans-anethole, reducing egg number, insects emerged and egg viability. © 2020 Society of Chemical Industry.

Association between Prenatal Exposure to Household Pesticides and Neonatal Weight and Length Growth in the Japan Environment and Children's Study.

The effects of prenatal exposure to household pesticides on fetal and neonatal growth have not been fully clarified. The present study aims to determine the effects of prenatal exposure to pesticides on neonates’ body size and growth during the first month. This study included 93,718 pairs of pregnant women and their children from the Japan Environment and Children’s Study. Participants completed self-reporting questionnaires during their second or third trimesters on their demographic characteristics and frequency of pesticide use during pregnancy. Child weight, length, and sex were obtained from medical record transcripts. Birth weight and length, as well as weight and length changes over the first month, were estimated using an analysis of covariance. Frequency of exposure to almost all pesticides had no effects on birth weight and length. However, we found small but significant associations (i) between the use of fumigation insecticides and decreased birth weight, and (ii) between frequencies of exposure to pyrethroid pesticides, especially mosquito coils/mats, and suppression of neonatal length growth. Prenatal exposure to household pesticides, especially those containing pyrethroids, might adversely influence fetal and postnatal growth trajectories.

Determining baseline toxicity of ozone against an insecticide-susceptible strain of the common bed bug, Cimex lectularius L. under laboratory conditions.

Ozone gas is commercially used for deodorization and microbial control. Its efficacy against stored product insect pests is well documented. In the midst of the common bed bug (Cimex lectularius L.) outbreak, claims were made that ozone gas was effective for their control. This study was conducted to determine baseline ozone concentrations and exposure times required for the control of an insecticide-susceptible C. lectularius strain under laboratory conditions. Dichlorvos (DDVP), an organophosphate class fumigant insecticide was used as a positive control. Nymphs and adults were more susceptible to ozone than eggs. Complete (100%) nymph and adult mortality was achieved at an ozone concentration (C) of 1500 ppm and exposure time (T) of 180 min, or concentration × time product (CT) of 270 000 ppm-min, whereas eggs required an eightfold higher CT (2 040 000 ppm-min). DDVP vapor was 2070-, 2542- and 450-fold more potent than ozone, against nymphs, adults and eggs, respectively. Baseline ozone toxicity data provide insights on the practicality of using this gas for the management of common bed bugs. High ozone CT products required for C. lectularius control, particularly eggs, suggest that its use for treating infested human dwellings is not feasible due to logistic, safety and monetary concerns. © 2020 Society of Chemical Industry.

Aluminum Phosphide Poisoning and Blast in Gastric Tube a Rare Phenomenon- A Case Report

Suicide by poisoning is the second most common cause of death by suicide (27.9%) as per The National Crime Records Bureau (NCRB) India in 2015.Aluminum phosphide (ALP) is the leading agricultural poison used to commit suicide as where its availability is not properly regulated. Aluminum phosphide (ALP) is a highly toxic solid fumigant pesticide, rodenticide and insecticide. It is commonly used as outdoor and indoor pesticide in developing countries like India, Pakistan, Srilanka and Iran because it is a cheap, effective, free from toxic residue and do not alter the viability of seeds. Aluminium Phosphide (ALP) is a highly toxic fumigant which is used commonly as an indoor pesticide in agriculture based industry for storage of grains. ALP on ingestion reacts with a gastric water and release phosphine gas, which is highly flammable, and very toxic in nature. Over the last few decades ALP has emerged as an agent of choice being used as suicidal poisoning in a country where it is readily available. The high mortality rate is due to severe mitochondrial dysfunction leading to disruption of cellular respiration, causing tissue hypoxia and organ dysfunction. Despite long research no specific antidote could be developed and the treatment remained supportive. Spontaneous ignition of phosphine (PH3) is a rare but very peculiar phenomenon reported in the case of aluminium phosphide poisoning. Here we share our experience in a case of phosphine (PH3) poisoning, which presented with spontaneous ignition and blast during treatment which caught the attention of local and national media in India,

Entomotoxic potential of Morinda lucida (benth.) Leaf powder as contact and fumigant biopesticides in the management of Plodia interpunctella (Hubner) [Lepidoptera: Pyralidae

The toxic effects of leaf powder of Morinda lucida against the developmental stages of Plodia interpunctella was investigated in this study. Air-dried leaf of Morinda lucida was pulverized into fine powders and administered at 0.5, 1.0, 1.5, 2.0 and 2.5 g dosages to maize grains containing egg, larval and adult stages of P. interpunctella separately, for contact and fumigant treatments. The insecticidal activities of the leaf powder was monitored at 24, 48, 72 and 96 h post-treatment periods. The leaf powder achieved 100% larval mortality at 1.5 g dosage after 72 h and 96 h post-treatment period as contact insecticide. Also, 1.5 g, 2.0, and 2.5 g dosages of the leaf powder deterred egg hatchability, thus no adult emergence was recorded in these treatments. The leaf powder as a contact insecticide also achieved 100%adult mortality at 1.5 g, 2.0 g and 2.5 g dosage after 72 h and 96 h post-treatment period. As a fumigant insecticide, no deterrent to egg hatchability was recorded, 100% larvae mortality was recorded in 2.0 g and 2.5 g treatments after 96 h post treatment, while 100% adult mortality was recorded in 2.5 g treatment after 72 h post treatment. The results obtained from this study shows that the leaf powder of M. lucida has some insecticidal properties that could be considered in the integrated management of P. interpunctella infesting stored foods. ?

The contributions of the population about prevention practice of Dengue

Introduction: Dengue is the world’s most important arboviral disease in terms of number of people affected ans is transmitted by mosquitoes Aedes Aegypti. The main strategy for epidemic prevention and control is population behavior in the prevention and insecticide fumigation. Objective: The following study aims to describe the contributions of the population about prevention practice of dengue. Materials and Methods: This is a descriptive research. Studies of any design published from 2012 to 2016 available in english, portuguese and spanish were included. The survey was conducted in the Scientific Electronic Library Online (SciELO). Results and Discussion: Six articles were found that match the eligible criterias. In accord to them, it was realized that the Brazilian population has a slouch behavior in practice prevention of mosquito outbreaks, providing opportunities that the mosquito prolife, and not getting success in disease control. This may occur because of poor infrastructure conditions in most cities, as well as the lack of preventive actions both private and public initiative. Conclusion: It was clear that the Brazilian population needs to engage in preventive actions related to dengue, but also charge more effective action of public policies to assist them in combating the proliferation of the mosquito.

Acute inhalation co-exposure to 1,2-dichloropropane and dichloromethane cause liver damage by inhibiting mitochondrial respiration and defense ability in mice.

1,2-Dichloropropane (1,2-DCP) is used as an industrial solvent, insecticide fumigant and household dry cleaning product. Carcinogenicity caused by long-term exposure to 1,2-DCP is well established. However, the possible liver damage and related toxic mechanisms associated with acute inhalation exposure to 1,2-DCP are rarely reported. In this study, we investigated the effects of individual and combined exposure to 1,2-DCP and dichloromethane (DCM) on mice liver. The results showed that 1,2-DCP significantly caused liver necrosis, possibly due to 1,2-DCP-induced inhibition of the mitochondrial respiratory chain complex I-IV activities, resulting in mitochondrial dysfunction and extreme ATP consumption. Moreover, 1,2-DCP also decreased mitochondrial defense ability by inhibiting the mitochondrial glutathione S-transferase 1 (MGST1) activity, further aggravating liver damage. Additionally, we found that DCM co-exposure potentially enhanced 1,2-DCP toxicity. Our findings suggest that inhibition of mitochondrial function and MGST1 activity play critical roles in modulating 1,2-DCP-induced liver damage. Furthermore, our results contribute to study the new mechanism of mitochondria-dominated signaling pathways underlying liver injury induced by 1,2-DCP and DCM.

Mortality of kiwifruit pests (Coccoidea) exposed to ethyl formate delivered using either carbon dioxide or nitrogen carrier gases

Ethyl formate (EF) is used as a fumigant against insect pests on many commodities. Delivery of EF uses a carrier gas, usually carbon dioxide (CO2), to reduce its flammability. However, CO2 is expensive and can only be delivered relatively slowly. Nitrogen (N2) has been proposed as an alternative. The efficacy of EF delivered using CO2 or N2, was evaluated at 5 and 15˚C, against two important postharvest pests of kiwifruit (greedy scale (Hemiberlesia rapax, Hemiptera: Diaspididae) and obscure mealybug (Pseudococcus viburni, Hemiptera: Pseudococcidae). Mortalities of both insect species were higher in the presence of CO2 than N2. There was a strong interaction with treatment temperature: N2 at 5˚C resulted in low mortality across both species. Greedy scale was more susceptible to EF than obscure mealybug across all treatments. Nitrogen as a carrier gas for EF substantially lowered the efficacy of EF as an insecticidal fumigant, relative to CO2. This is hypothesised to be caused by differing respiration rates across temperatures and CO2 concentrations. Solutions for rapid CO2 delivery should be explored over further trials with N2 at low temperatures.

UJI TEPUNG BIJI MENGKUDU (Morinda citrifolia L.) TERHADAP HAMA BUBUK JAGUNG Sitophilus zeamais M. (Coleoptera; Curculionidae)

Sitophilus zeamais M. was a warehouse pest that attacks corn kernels in storage. S. zeamais pest control commonly used fumigant insecticides that used still has many disadvantages such as food safety impacts, environmental pollution and pest resistance, so that a safe alternative to control was needed, one of which was using noni seeds. This research was aimed to obtain a dose of noni seed flour that was effective to S. zea mays corn powder pest mortality.The research was conducted at the Laboratory of Plant Pest, Faculty of Agriculture, University of Riau from March to May 2018.The treatment used was the dose of noni seed flour 0 g.100 g-1 corn, 2 g.100 g-1 corn, 4 g.100 g-1 corn, 6 g.100 g-1 corn, and 8 g.100 g-1 corn. This research was conducted experimentally using a completely randomized design (CRD) with 5 treatments and 4 replications. Based on the results of the research, the dose of noni seeds 8 g.100 g-1corn had not been effective in controlling S. zeamais with mortality of 52.50%, shrinkage of corn seed weight by 8.78% and an increase in individuals by 8.20. Keywords: Morinda citrifolia L., Sitophilus zeamais M., Zea mays