Toxicity of acephate to larvae of gypsy moth as a function of host plant and bioassay method

We examined toxicity of acephate to third-instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), under different conditions of administration method, availability of food to larvae during bioassay, host plant, and activity of detoxifying enzymes. Larvae that had been fed field-collected foliage of white alder (Alnus rhombifolia Nutt.) were less susceptible 48 h after treatment with topically applied acephate if they were allowed to continue feeding on foliage during the bioassay period (LD₅₀= 60.6 μg/g larva ) than if they were not (LD₅₀= 13.5 μg/g larva ). All surviving larvae were replaced on their original food plant after the 48-h bioassay; of these, 14.4% of the larvae not fed during treatment died before pupation, compared with 1.3% of the larvae fed alder during treatment. The LD₅₀ obtained for topically treated larvae reared and treated on Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, (51.1 μg/g larva) was comparable to that obtained for larvae fed alder (60.0 μg/g larva) throughout treatment. Larvae treated orally with acephate, however, were slightly more susceptible when reared on Douglas-fir (LC₅₀, 20.3 ppm ) than when reared on alder (LC₅₀, 27.0 ppm ). Post-treatment mortality in orally treated larvae was 10.3% in those fed alder and 9.5% in those fed Douglas-fir. Higher cytochrome P-450 activities in larvae reared on Douglas-fir apparently did not enhance tolerance to acephate. Both sexes of orally treated larvae took significantly longer to pupate than did controls on both foliage types, as did topically treated males fed Douglas-fir. Pupal weight generally was slightly, but not always significantly, higher in treated than untreated larvae under all dietary and treatment regimes.     

Density‐dependent polyphenism and baculovirus resistance in teak defoliator,Hyblaea puera (Cramer)

1. Field populations of the teak defoliator larvae, Hyblaea puera Cramer exhibit colour polyphenism under different population densities: greyish‐green with black‐ and orange‐coloured dorsal bands in low‐density endemic populations and uniformly black or intermediate colour during high‐density population. 2. The density dependence of colour polyphenism was confirmed by field monitoring of H. puera populations during 2008–2010. 3. The above findings were later substantiated by rearing H. puera larvae under different densities (i.e. solitary and crowded in the laboratory). Ninety one per cent of the solitary reared laboratory population developed bright coloration whereas, 92% of the group reared larvae turned to black. Eight per cent of larvae from both the rearing densities were of intermediate colour. 4. Density‐dependent resistance build‐up against H. puera nucleopolyhedrovirus by H. puera were tested using the fifth instar larvae. The results showed three‐fold increase of median lethal dose (LD₅₀) value for the group reared larvae (5332 polyhedral occlusion bodies/larvae) compared to the solitary reared ones (1727 polyhedral occlusion bodies/larva) and also significant difference for the mean time to death (3.6 and 3.3 days, respectively). 5. The study revealed the strong influence of larval density on H. puera larval melanism and resistance build‐up against H. puera nucleopolyhedrovirus.     

Evaluations of larvicidal activity of medicinal plant extracts to Aedes aegypti （Diptera： Culicidae） and other effects on a non target fish

A preliminary study was conducted to investigate the effects of the extracts of 112 medicinal plant species, collected from the southern part of Thailand, on Aedes aegypti. Studies on larvicidal properties of plant extracts against the fourth instar larvae revealed that extracts of 14 species showed evidence of larvicidal activity. Eight out of the 14 plant species showed 100% mosquito larvae mortality. The LC50 values were less than 100μg/mL （4.1μg/ mL-89.4μg/mL）. Six plant species were comparatively more effective against the fourth instar larvae at very low concentrations. These extracts demonstrated no or very low toxicity to guppy fish （Poecilia reticulata）, which was selected to represent most common non-target organism found in habitats ofAe. aegypti, at concentrations active to mosquito larvae. Three medicinal plants with promising larvicidal activity, having LC50 and LC50 values being 4.1 and 16.4 μg/mL for Mammea siamensis, 20.2 and 34.7 μg/mL forAnethum graveolens and 67.4 and 110.3μg/mL forAnnona muricata, respectively, were used to study the impact of the extracts on the life cycle ofAe. aegypti. These plants affected pupal and adult mortality and also affected the reproductive potential of surviving adults by reducing the number of eggs laid and the percentage of egg hatchability. When each larval stage was treated with successive extracts at the LC50 value, the first instar larvae were found to be very susceptible to A. muricata and the second instar larvae were found to be susceptible to A. graveolens, while the third and fourth instar larvae were found to be susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence and had no adverse effects on P. reticulata at LC50 and LC50 values, except for the M. siamensis extract at its LC50 value.     

Assimilation of carbon and nitrogen from pollen and nectar by a predaceous larva and its effects on growth and development

Abstract. 1. Predaceous insects may benefit from feeding on non‐prey foods, such as pollen, nectar, and honeydew, because they can provide nutrients that help maintain metabolism and enhance overall nutrient intake. Yet, the extent to which predaceous insects can assimilate non‐prey food and the importance of diet mixing during particular life history stages is poorly understood. In this study the relative contribution of an omnivorous diet to the growth and survivorship of a predaceous larva was tested in a hypothetical situation in which nutritionally optimal prey was not available. The study system comprised a predaceous larva (second‐ and third‐instar larvae of the green lacewing Chrysoperla carnea), nutritionally poor prey (larvae of Drosophila melanogaster), and non‐prey food (pollen suspension, a mixture of bee pollen and artificial nectar (1 M sucrose solution)). Chrysoperla carnea larvae in the mixed diet treatment were provided with both Drosophila larvae and pollen suspension, while those reared on the prey and non‐prey diet treatments received only Drosophila larvae or pollen suspension respectively. 2. The inclusion of pollen and sucrose in their diet enhanced the growth of C. carnea larvae. Second instars reared on the mixed diet developed significantly faster than their cohorts reared on the prey diet, however third instars reared on the mixed diet did not develop faster than their cohorts reared on the prey diet. Larvae reared on the mixed diet became larger adults than did those reared on either the prey or non‐prey diets. Third instars reared on the non‐prey diet completed their development while second instars in the non‐prey diet treatment failed to pupate. 3. Stable isotope analysis indicated that the larvae obtained most of their carbon (55–73%) and nitrogen (71–73%) from Drosophila but acquired only a minor amount of carbon (2–5%) and nitrogen (3–11%) from pollen. Larvae reared on the mixed and non‐prey diets acquired a relatively significant amount of carbon (23–51%) from sucrose. 4. A model, which included a novel fractionation factor to account for the isotopic effect of metamorphosis, was developed to explain the proportion of larval growth attributable to each diet item. It explained the adult δ¹³C values to within 0.2‰ and adult δ¹⁵N values to within 0.7‰ in all treatments. 5. Adults fed ¹⁵N‐labelled pollen as larvae retained the ¹⁵N signal of the pollen as adults. 6. The collective results of this study support the view that, despite their dependence on prey arthropods to obtain most of their dietary nitrogen, omnivorous lacewing larvae can enhance their growth and development by supplementing their diets with alternative non‐prey food resources. This finding is consistent with the notion that omnivory has evolved as a feeding strategy to acquire both additional nitrogen as well as trace nutrients.     

Insecticidal activity of Origanum majorana L. essential oil as anti‐cholinergic agent

The present study was focused on exploring the presence of active compounds in Origanum majorana essential oil (OmEO), and its various knock‐down effects against the rice moth, Corcyra cephalonica. GC–MS analysis detected the existence of major compounds such as monoterpenes, cis‐β‐terpineol and terpinen‐4‐ol with the total proportion of 52.16%. Fumigant toxicity against adult and larvae was calculated with an LC₅₀ value of 11.31 and 49.83 μL/L air, respectively. The contact toxicity against adult, pupa, larvae and eggs was observed with LC₅₀ value 2.54, 0.95, 2.78, and 0.49 μL/L, respectively. Furthermore, the influential repellent behavior against adults has been observed. Acetylesterase (AChE) inhibition activity of OmEO was observed against adult and larvae of C. cephalonica with an IC₅₀ value of 35.89 and 118.54 μL/mL, respectively. Moreover, computational docking study revealed the binding affinity of Cis‐β‐terpineol and terpinen‐4‐ol towards the active binding sites of AChE. On the other hand, Fluorescence‐assisted cytometry and comet assay confirmed the cytotoxic and genotoxic effect of OmEO at various concentrations on C. cephalonica. Altogether, the results showed the knock‐down effect of OmEO against C. cephalonica, and it could be a potential biocontrol measure against the stored product pest.     

Interactions between entomopathogenic nematodes and imidacloprid for rose sawfly control

Rose sawfly, Arge ochropus (Gmelin), is one of the most important pests of ornamental plants such as roses and wild rose bushes in Northern Iran. We investigated the interactions between the insecticides imidacloprid and the entomopathogenic nematodes Heterorhabditis bacteriophora and Steinernema carpocapsae as control agents of fifth-instar larvae in the laboratory. The larvae were very susceptible to S. carpocapsae (LC₅₀: 21 infective juvenile per larva) and H. bacteriophora (LC₅₀: 32). Combinations of two imidacloprid rates (LC₃₀ and LC₅₀) and four rates of each nematode species (LC₂₅–LC₇₅) were tested. Combinations with the lower imidacloprid rate except for that with the highest H. bacteriophora rate caused higher mortality than both respective single-agent treatments. In combination with the higher imidacloprid rate, only one combination with H. bacteriophora and two combinations with S. carpocapsae caused higher mortality than both respective single-agent treatments. Interactions were generally stronger at the lower imidacloprid rate and were stronger for S. carpocapsae (synergistic in seven combinations, additive in one) than for H. bacteriophora (synergistic in two, additive in six). Synergistic imidacloprid-S. carpocapsae combinations could be a useful tool for the control of A. ochropus larvae that would simultaneously control other common pests susceptible to imidacloprid.     

Fouling deterrent chemical defence in three muricid gastropod egg masses from the Southeast coast of India

Abstract

The egg masses of the marine muricid gastropod molluscs Chicoreus virgineus, Chicoreus ramosus and Rapana rapiformis were studied for antifouling activities. The minimum inhibitory concentrations of crude extracts for the inhibition of byssal production and attachment of the brown mussel Perna indica were 650 μg ml^?1, 1150 μg ml^?1 and 925 μg ml^?1 from the three muricid gastropods, respectively. Higher LC₅₀ values than EC₅₀ values and 100% recovery of the mussels in the toxicity assay indicated the non-toxic nature of the extracts. The gradient partitioning of the egg mass extracts and subsequent antimicrofouling screening against 40 biofilm bacteria showed wide-spectrum antibacterial activity of the medium polar fraction from C. virgineus; the non-polar fraction from R. rapiformis and both non-polar and medium polar fractions from C. ramosus. The antimicrofouling activity from extracts of the three egg masses was found to be more prominent than antimacrofouling activity. This may be attributed to the targeting of a defence strategy against microbes in order to protect the developing mollusc embryos.     

Quantitative and qualitative aspects in the production of a nuclear polyhedrosis virus in Spodoptera exigua larvae

Spodoptera exigua nuclear polyhedrosis virus was produced in late fourth instar S. exigua larvae, reared on semi-artificial diet. A maximum amount of virus, 1–2 × 10⁹ polyhedra/larva, was produced in individually-reared larvae after 7 days of incubation, with an inoculum of 7–5 × 10⁴ polyhedra/cm² diet surface. Virus yield was slightly reduced to 9 × 10⁸ polyhedra/larva when production was carried out in groups of 400 and 600 larvae per container. Biological activity of virus harvested from living larvae and from dead cadavers was similar. Microbial contaminants, predominantly bacteria, in the virus product numbered 1–6% of the number of polyhedra. Tests for the presence of vertebrate-pathogenic bacteria in the virus product were all negative.     

THE BIOLOGICAL ACT'IVITIES OF YELLOW AZALEA,RHODODENDRON MOLLE G. DON AGAINST THE VEGETABLE LEAFMINER,LIRIOMYZA SATIVAE (DIPTERA: AGROMYZIDAE) *

Abstract The results of laboratory and greenhouse bioassays indicated that Rhodojaponin‐ III (Abbr. R‐ 1) and extracts of flowers from Rhododendron molle G. Don possessed signficant feeding inhibition and insectcidal properties against the larvae and adults of Liromyzia sativae. Treated with 500 mg/L R‐ III 1 000 mg/L molosul‐tap, and 10 000 mg/L methanol(MeOH) ethyl acetate (EtOAc), CH₂Cl₂, methanol‐water (MeOH‐H₂O) extracts the rates of feeding inhibition were 77. 34 % 74.30 % 82.15 % 77.50 % 67. 33 % 62.85 % against the 2nd instar larvae, and were 67.66% 55.21 % 49.72% 54.26% 46.81 % 38.53% against the 3rd instar larvae, respectively;LC₅₀ values against the 2nd instar larvae were 208.65, 166.05, 2.74 ± 10³,766.72, 5.95 ± 10³, 1.85 ± 10³mg/L, and against 3rd larvae were 300.62, 256.00, 4.33 ±10³, 1.03 ± 10³,9.79 ± 10³, and 2.62± 10³mg/L, respectively. Against the adults, LC₅₀ values of R‐III EtOAc extract and molosultap were 159.07.723.87 and 134.55mgL respectively after treatment for 24 h.     

EFFECT OF FEEDING STIMULANT ON THE FEEDING BEHAVIOR AND MORTALITY OF HELICOVERPA ARMIGERA ON DIETS WITH BACILLUS THURINGIENSIS*

Abstract Bacillus thuringiensis (Bt) was noticed to be highly deterrent to the feeding of Helicoverpa armigera larva when incorporated into diets, even at the non‐lethal dosage. As the dosage of Bt increased, the deterrence showed a tendency of elevation. Feeding stimulant, FS‐1 could attract larvae for feeding, and increase larval feeding time and consumption. Addition of 1% (vlv) FS1 could alleviate the deterrent effect of Bt, especialy in low concentration. In no‐choice test, it was observed that while 1% (v/v) FS1 was added, LC₅₀, of Bt underwent a 41% decrease, but in the choice test, the mortality of larvae was not significantly enhanced.     

Efficacy of bioactive compounds from Curcuma longa L. against mosquito larvae

To identify larvicidal compounds from the ethanolic extracts of Curcuma longa root, the active compounds were isolated using activity‐guided fractionation with column chromatography and identified based on nuclear magnetic resonance (NMR) and mass spectrometry (MS) data. The dipping method was used to determine the larvicidal activities of each compound against 4th‐instar larvae of Culex pipiens pallens. Two compounds were isolated and identified, ar‐turmerone and 8‐hydroxyl‐ar‐turmerone. The two compounds exhibited larvicidal activities against the 4th‐instar larvae of C. pipiens pallens after 24 hr of treatment with LC₅₀ values of 138.86 and 257.68 ppm, respectively. The larvicidal activities of ar‐turmerone and 8‐hydroxyl‐ar‐turmerone against C. pipiens pallens are reported herein for the first time. The elucidation of the structure of these phytochemicals and their insecticidal activities are important for assessing the potential of this plant as a botanical insecticide.     

Insecticidal activity of garlic juice in two dipteran pests

Abstract

• 1 Botanical products excluding pyrethroids constitute a small, but growing portion of the U.K. pesticides market. With increasing legislative pressure upon chemical pesticides such as organophosphates, interest in this sector is increasing steadily.
• 2 Garlic Allium sativum L. juices and extracts form the basis of several commercially available pest control products, but the performance of these products is variable, possibly due to lack of quality control upon batches of materials in the manufacturing process.
• 3 Some garlic products designed for use in the food industry are subjected to rigorous batch‐control to ensure organoleptic consistency. We studied the insecticidal efficacy of a commercially produced food grade garlic juice using two target dipteran pests, Delia radicum (L.) and Musca domestica L.
• 4 Exposure of the two species to different concentrations of garlic juice revealed variability in insecticidal effect across life stages. LC₅₀ values recorded for D. radicum were: eggs (7‐day exposure) 0.8%; larvae (24‐h exposure) 26.4%; larvae (48‐h exposure) 6.8%; and adults (24‐h exposure) 0.4%. LC₅₀ values recorded for M. domestica were: eggs (7‐day exposure) 1.6%; larvae (24‐h exposure) 10.1%; larvae (24‐h exposure) 4.5%; and adults (24‐h exposure) 2.2%.
• 5 Mortality rates caused by the garlic juice were comparable with those obtained with the organophosphate pesticide Birlane^®, indicating parity of effect at various concentrations depending on life stage.
• 6 We conclude that this product may provide an effective, naturally‐derived insecticide for use in agricultural systems against dipteran pests.

     

Boric acid‐induced immunotoxicity and genotoxicity in model insect Galleria mellonella L. (Lepidoptera: Pyralidae)

Boric acid (BA) is widely used in various industrial process and can be accessed to nontarget organisms. This study aimed to investigate the insecticidal effects of BA and its toxic activities with respect to immunologic and genotoxic effects using Galleria mellonella larvae as a model. BA concentrations (78.125–10,000 ppm) were administrated to the larvae using the feeding method. Concentration‐dependent mortality was observed in all larval groups. Probit analysis revealed LC₃₀, LC₅₀, and LC₇₀ values to be 112.4, 320.1, and 911.4 ppm, respectively. These concentrations were used in all bioassays. Drastic reductions in total hemocyte counts along with changes in differential hemocyte counts were observed following BA treatment. Cell viability assays showed dose‐dependent reductions in viable cells and an increase in the necrotic and apoptotic ratios after BA treatment. However, mitotic indices of larval hemocytes did not change at all BA concentrations. The cytotoxic effect of BA led to a significant reduction in cellular immune responses such as encapsulation, melanization, and nodulation activities of treated larvae. While BA increased micronucleus ratios at the highest concentration, comet parameters indicating DNA damage increased in G. mellonella larval hemocytes at all concentrations. These report that BA suppresses the immune system of G. mellonella and also poses risks of genotoxicity at high concentrations.     

Resistance of sugarcane borer to Bacillus thuringiensis Cry1Ab toxin

The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), strain (F52‐3‐R) was developed from F₃ survivors of a single‐pair mating on commercial Cry1Ab Bacillus thuringiensis (Bt) corn plants in the greenhouse. The susceptibility of a Bt‐susceptible and the F52‐3‐R strain of D. saccharalis to trypsin‐activated Cry1Ab toxin was determined in a laboratory bioassay. Neonate‐stage larvae were fed a meridic diet incorporating Cry1Ab toxin at a concentration range of 0.0625 to 32 µg g^?1. Larval mortality, larval weight, and number of surviving larvae that did not gain significant weight (<0.1 mg per larva) were recorded on the 7th day after inoculation. The F52‐3‐R strain demonstrated a significant level of resistance to the activated Cry1Ab toxin. Larval mortality of the Bt‐susceptible strain increased in response to higher concentrations of Cry1Ab toxin, exceeding 75% at 32 µg g^?1, whereas mortality of the F52‐3‐R strain was below 8% across all Cry1Ab concentrations. Using a measure of practical mortality (larvae either died or gained no weight), the median lethal concentration (LC₅₀) of the F52‐3‐R strain was 102‐fold greater than that of the Bt‐susceptible insects. Larval growth of both Bt‐susceptible and F52‐3‐R strains was inhibited on Cry1Ab‐treated diet, but the inhibition of the F52‐3‐R strain was significantly less than that of the Bt‐susceptible insects. These results confirm that the survival of the F52‐3‐R strain on commercial Bt corn plants was related to Cry1Ab protein resistance and suggest that this strain may have considerable value in studying resistance management strategies for Bt corn.     

Comparative study of three herbal formulations against dengue vectors Aedes aegypti

The efficacy of three formulations (i.e., natural lavender crude, essential oil, and gel) extracted from Lavender angustifolia was tested against vectors of the epidemic dengue virus, Aedesaegypti, to evaluate their larvicidal activity effect. The ethanolic extract of the lavender crude was prepared using a rotary evaporator, while the other extracts, such as essential oil and gel, were obtained from iHerb, a supplier of medicinal herbs in the US. The mortality rate of larvae was evaluated 24 h after exposure. Larvicidal activity of the lavender crude was 91% mortality at 150 ppm, 94% for essential oil at a concentration of 3000 ppm, and 97% for lavender gel at a 1000 ppm. Natural lavender crude was one of the most promising extracts tested against Ae.aegypti larvae, with lethal concentrations at LC₅₀ and LC₉₀ of 76.4 and 174.5 ppm post-treatment. The essential oil had the least effect on mosquito larvae, with LC₅₀ and LC₉₀ reaching 1814.8 and 3381.9 ppm, respectively. The lavender gel was moderately effective against Ae. aegypti larvae, with LC₅₀ and LC₉₀ values reaching 416.3 and 987.7 ppm after exposure. The occurrence of morphological abnormalities in the larvae treated with the three compounds, in turn, resulted in an incomplete life cycle. Therefore, our results indicated that natural lavender crude displayed the highest larvicidal activity against larvae, followed by gel and essential oil. Thus, this study concluded that lavender crude is an effective, eco-friendly compound that can be used as an alternative to chemical products to control vector-borne epidemic diseases.     

Effects of Bacillus thuringiensis Cry1C toxin on the metabolic rate of Cry1C resistant and susceptible Spodoptera exigua (Lepidoptera: Noctuidae)

Abstract. The effects of Bacillus thuringiensis (Bt) Cry1C toxin on the metabolic rate of Cry1C resistant and susceptible Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) are investigated using closed‐system respirometry. Mechanisms of resistance to the Bt toxin may be associated with an energetic cost that can be measured as an increase in metabolic rate compared with Bt‐susceptible insects. This hypothesis is tested using third‐ and fifth‐instar larvae and 1–7‐day‐old pupae. Metabolic rate is measured as the amount of O₂ consumed and CO₂ produced. V?_O2 and V?_CO2 (mL g^?1 h^?1) of third‐instar Cry1C resistant larvae reared continuously on a diet containing 320 µg Cry1C toxin per g diet (CryonT) are significantly greater than third‐instar Cry1C resistant larvae reared on toxin for 5 days and reared thereafter on untreated diet (Cry5dT), Cry1C resistant larvae reared on untreated diet (CryReg) and the susceptible parental strain (SeA) reared on untreated diet. There are no differences in V?_O2 and V?_CO2 (mL g^?1 h^?1) among treatment groups for fifth‐instar larvae. CryonT larvae and pupae weigh significantly less than larvae and pupae receiving other treatments. Smaller body mass may be an important biological cost to individuals exposed continuously to Bt toxin. One‐day‐old pupae of all treatment groups exhibit a high V?_O2 (mean approximately 0.174 mL g^?1 h^?1) with CryonT having a significantly greater value than all other treatments; there are no differences among the other treatments. Pupal metabolic rates of all treatment groups decline to a minimum between days 2 and 4 then increase linearly between days 4 and 7 until adult emergence. These results demonstrate no difference in metabolic rates, and possibly fitness costs, between resistant (CryReg and Cry5dT) and susceptible (SeA) S. exigua except when larvae were reared continuously on toxin (CryonT).     

Sublethal effects of hexaflumuron on development and reproduction of the diamondback moth,Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract Effects of hexaflumuron at 10% lethal concentration (LC₁₀) and LC₂₅ on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC₅₀, LC₁₀ and LC₂₅ values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre‐pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre‐adult stages declined significantly at LC₂₅ concentration. Reproduction parameters such as reproductive rate (R₀) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC₁₀ concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.     

Fumigant toxicity of Laurus nobilis and Myrtus communis essential oils on larvae and adults of the Red flour beetle,Tribolium castaneum Herbst (Col.: Tenebrionidae)

Considering the invasion to food commodities by insects and harmful effect of chemical pesticides, essential oils are among the best known substances tested against stored product pests. These compounds may act as fumigants, contact insecticides, repellents or anti-feedants. In present study, fumigant toxicity of essential oils from Laurus nobilis L. and Myrtus communis L. was assessed on larvae and adults of Tribolium castaneum Herbst at 27?±?2?°C, 60?±?5% RH in darkness. Each essential oil was tested in five concentrations with three replicates. The LC₅₀ values of L. nobilis and M. communis against adults of beetle were calculated 243.78 and 56.11?μl/l and LC₉₅ values for them were 685.85 and 144.01?μl/l, respectively. For the larvae of T. castaneum, the LC₅₀ values for L. nobilis and M. communis were 211.64 and 69.63 and LC₉₅ values were 656.84 and 183.65?μl/l, respectively. Results showed that these essential oils may have potential as botanical control agents against larvae and adults of T. castaneum.     

爵床的甲醇提取物对小菜蛾的生物活性作用

为探明爵床(Justicia procumbens)甲醇提取物对小菜蛾的生物活性,采用室内生测法测定了爵床甲醇提取物对小菜蛾的触杀、拒食、胃毒、生长发育抑制和产卵忌避作用。结果表明,爵床甲醇提取物对小菜蛾幼虫具有较强的触杀、拒食、胃毒和生长发育抑制活性,对小菜蛾成虫具有较强的产卵忌避活性。在触杀试验中,药后1、2 d和3 d爵床甲醇提取物对小菜蛾3龄幼虫的致死中浓度(LC50)分别为5.17、4.05和3.06 mg/m L;在拒食试验中,药后1 d和2 d提取物对3龄幼虫的选择性拒食中浓度(AFC50)分别为2.64和3.13 mg/m L,药后1 d和2 d提取物对3龄幼虫的非选择性拒食中浓度(AFC50)分别为3.70、4.54 mg/m L;在胃毒试验中,药后4、5、6 d和7 d提取物对3龄幼虫的致死中浓度(LC50)分别为8.13、3.65、2.88、2.23 mg/m L;在生长发育抑制试验中,药后1 d和2 d提取物对3龄幼虫的抑制中浓度(IC50)分别为2.02、1.40 mg/m L;在产卵忌避试验中,药后1、2 d和3 d提取物对小菜蛾成虫的选择性产卵忌避中浓度(AOC50)分别为2.61、3.66、4.58 mg/m L,药后1、2和3 d提取物对小菜蛾成虫的非选择性产卵忌避中浓度(AOC50)分别为3.19、4.52、5.65 mg/m L。由此证实,爵床提取物对小菜蛾具有显著的毒杀活性,具有开发为新型高效、低毒植物源农药的潜在价值。     

Extracellular electrical activity from the photoreceptors of midge

The ontogeny of photosensitivity has been studied in a holometabolous insect, the midgeChironomus ramosus. The life cycle of midges shifts from an aquatic environment to a non-aquatic environment. Extracellular electrical activity of photoreceptor organs was recorded at larval and adult stages. We found an increase in photosensitivity as the larva metamorphosed to the adult stage. This is the first report of changes in photosensitivity during the development of any insect described in an ecological context.