Red imported fire ants cover the insecticide-treated surfaces with particles to reduce contact toxicity

Surface treatment is commonly used in controlling the red imported fire ants, Solenopsis invicta Buren. In the present study, the behavioral responses of S. invicta workers to surfaces treated with insecticides were investigated. Toxicological tests showed that beta-cypermethrin had the highest contact toxicity (with the lowest LC₅₀ value) among nine tested insecticides, followed by thiamethoxam, fipronil, indoxacarb, chlorfenapyr, spinetoram, rotenone, avermectin, and chlorantraniliprole. In the laboratory, surfaces treated with beta-cypermethrin or rotenone significantly reduced the number of foraging ants. In addition, S. invicta workers transported significantly more particles (measured in weight and/or covered area) onto surfaces treated with fipronil (50, 500, and 5000 µg/mL), rotenone (5000 µg/mL), or avermectin (5000 µg/mL) compared with the controls. Similarly, these insecticides significantly triggered the particle-covering behavior of ants in the field. We hypothesized that such behaviors would reduce the contact toxicity of insecticides against S. invicta. When the surfaces treated with fipronil or rotenone (500 or 5000 µg/mL) were artificiality covered with particles, S. invicta had significantly higher LT₅₀ values compared with insecticide-treated surfaces without particles. This study provides the first evidence that S. invicta workers can perform particle-covering behavior to reduce the toxicity of certain insecticides, which constitutes a unique insecticide-resistance strategy in ants.

     

Effects of methoxyfenozide and pyridalyl on the larval ectoparasitoid Habrobracon hebetor

Habrobracon hebetor Say (Hymenoptera: Braconidae) is an ectoparasitoid that is used for inundative biological control of various lepidopteran insect pests. Lethal and sublethal effects of two biorational insecticides, methoxyfenozide and pyridalyl, were evaluated on H. hebetor under laboratory conditions. The adults were exposed to dry insecticide residues that were applied on glass plates. Bioassays showed that the LC₅₀ values of methoxyfenozide and pyridalyl were 155 and 1,226 μg a.i./ml, respectively. The LT₅₀ values of methoxyfenozide and pyridalyl were 2.1 and 3.3 days, respectively. The effects of methoxyfenozide and pyridalyl on larvae were tested using a dip method with field-recommended concentrations of either insecticide. The emergence rates were reduced by 24.4 and 29.3 % for methoxyfenozide and pyridalyl treatments, respectively. In order to assess the sublethal effects of low-lethal concentrations of methoxyfenozide and pyridalyl, adult wasps were exposed to the LC₃₀ concentration of each insecticide, and demographic parameters of live wasps were recorded. Exposure of adults to low-lethal concentrations (LC₃₀) negatively affected the fecundity, fertility, and sex ratio, and also the intrinsic rate of increase (r _m), finite rate of increase (λ), generation time (T), and doubling time (DT). The longevity and net reproductive rate (R ₀) of H. hebetor were not affected by sublethal exposure to these insecticides. The results showed that despite low acute toxicities of both insecticides on larval and adult stages of H. hebetor, they may negatively affect the population of the parasitoid and interfere in IPM programs.     

Lethal and sublethal effects of cycloxaprid,a novel cis-nitromethylene neonicotinoid insecticide,on the mirid bug Apolygus lucorum

Recently, Apolygus lucorum (Hemiptera: Miridae) has become an important insect pest of Bt cotton and fruit trees in China. At present, the application of chemical insecticides is the main control option for this pest. We investigated the lethal effect of seven neonicotinoid insecticides on A. lucorum adults, including six commercialized neonicotinoids and a novel one, cycloxaprid, which is developed in China. In addition, we assessed the sublethal physiological (longevity, fecundity) and behavioral (pre-oviposition and oviposition periods) effects of LD₁₀ (low lethal dose) and LD₄₀ (moderate lethal dose) of cycloxaprid on the mirid bug. Lethal effect of the insecticides was determined using a topical exposure method; contact toxicity against the adults was ranked as follows: cycloxaprid, nitenpyram > clothianidin > acetamiprid, imidacloprid > thiamethoxam > dinotefuran. Among these insecticides, the toxicity of cycloxaprid against the adults was the highest; its LD₅₀ value was 2.54 ng a.i. (active ingredient)/adult. Both LD₁₀ (0.74 ng a.i./adult) and LD₄₀ (1.98 ng a.i./adult) of cycloxaprid induced sublethal effects in the adults; we observed a reduced longevity in males and the LD₄₀ also shortened the longevity of females. In addition, the LD₄₀ prolonged the pre-oviposition period and shortened the oviposition period of females, and it decreased their fecundity. The hatching rate of eggs laid by the females exposed to LD₁₀ and LD₄₀ greatly decreased (two-fold lower when exposed to LD₄₀). Our results demonstrate that cycloxaprid is among the best candidate insecticides for controlling A. lucorum, and it showed significant lethal and sublethal effects on this mirid bug.     

Comparison of spinosad with three traditional grain protectants against Prostephanus truncatus (Horn) and Ephestia kuehniella (Zeller) at different temperatures

The insecticidal effects of deltamethrin, chlorpyriphos-methyl, pirimiphos-methyl, and spinosad were evaluated against adults of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and larvae of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae). Spinosad was applied at 1 and 0.5 ppm, deltamethrin at 0.5 ppm, chlorpyriphos-methyl at 2.25 ppm, and pirimiphos-methyl at 4 ppm. All tests were carried out on wheat for E. kuehniella and in maize for P. truncatus, at three temperature levels, 20, 25, and 30 °C. Mortality of the exposed individuals of P. truncatus was measured after 7, 14, and 21 days of exposure, and 60 days later, the progeny production in the treated and untreated substrate was recorded. In the case of Ephestia kuehniella, mortality was assessed after 25 days. Spinosad was highly effective against P. truncatus adults, even at 0.5 ppm, but 1 ppm provided a better “speed of kill” and a higher suppression of progeny production. Mortality of the exposed P. truncatus adults after 21 days of exposure on maize treated with 0.5 ppm of spinosad was 100 %, regardless of the temperature level tested. A complete (100 %) mortality level was also noted in the case of maize treated with deltamethrin and pirimiphos-methyl, while in the case of chlorpyriphos-methyl, mortality at the 21 day exposure ranged between 61 and 90 %. Progeny production was completely suppressed only on maize treated with deltamethrin. In contrast, pirimiphos-methyl was the most effective grain protectant for E. kuehniella, since mortality was usually <99 %. In general, for both species tested, temperature had a significant effect on mortality, but this trend was different at different insecticides.     

Conspecific transmission of insecticidal adhesive powder through mating in the Mediterranean fruit fly,Ceratitis capitata

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) (medfly) is a polyphagous pest of global economic importance. This study tested the suitability of two different adhesive powders, Entostat^TM and an adhesive metal powder, as insecticide carriers for use in a lure and kill pest control system, that would allow the auto-dissemination of insecticide from males to female conspecifics through sexual interactions. Lethal time to 50 % (LT₅₀) irreversible knockdown was calculated for male and female medfly artificially contaminated by five different doses of spinosad insecticide, formulated with each adhesive carrier powder. The formulations with adhesive metal powder resulted in a rapid knockdown of medfly which was too fast for use in an auto-dissemination system. Entostat powder with 2 % spinosad gave the best performance, allowing sufficient time for transfer between conspecifics before knockdown and, therefore, allowing the most auto-dissemination (LT₅₀ 4 h). Knockdown through transfer of powder from males to females during mating was confirmed, with knockdown at 70–78 % for mated females, with a LT₅₀ of <40 h. These results indicate that Entostat powder is a suitable carrier powder for the development of an insecticidal auto-dissemination control system.     

MA-chitosan nanogel loaded with Cuminum cyminum essential oil for efficient management of two stored product beetle pests

Natural essential oils have received increased attention as alternatives to synthetic pesticides for pest management of foodstuffs. Recently, microencapsulation and other controlled release techniques are used to increase insecticidal efficiency and persistence of essential oils with slow and controlled release. In this study, the possibility of improving the insecticidal activity of plant essential oils was investigated for effective management of two stored product beetle pests. Self-assembly technique was used to prepare nanogels of myristic acid-chitosan loaded by essential oil extracted from cumin, Cuminum cyminum L. Fumigant toxicity of C. cyminum oil and oil-loaded nanogels (OLNs) were investigated at 4, 7, 10, 13, and 16 µL/L air against the granary weevil Sitophilus granarius L. and 8, 11, 14, 17, and 20 µL/L air for confused flour beetle Tribolium confusum Jacquelin du Val. Experiments were conducted at 27 ± 1 °C and 55 ± 5 % relative humidity in continuous darkness. Insecticidal bioassay revealed that OLNs were more toxic than C. cyminum oil against tested beetle pests. The persistence of the oil and OLNs was also evaluated against two tested species. Results indicated that C. cyminum oil completely lost its insecticidal activity after 12 days, whereas at the same period, the OLNs lost about 60 % of its activity when applied against S. granarius and 15% for T. confusum. Therefore, it could be concluded that encapsulation improved the persistence of the oil.     

Field resistance of Spodoptera litura (Lepidoptera: Noctuidae) to organophosphates, pyrethroids, carbamates and four newer chemistry insecticides in Hunan, China

The present studies were carried out to evaluate resistance in the populations of Spodoptera litura Fab. (Lepidoptera, Noctuidae) from five districts of Hunan Province in China to various insecticides from 2010 to 2012 using a standard leaf dip bioassay method. For organophosphates and pyrethroids, resistance ratios compared with a susceptible Lab-BJ strain were in the range of 14–229-fold for organophosphates and 12–227-fold for pyrethroids. Similarly, relative low levels of resistance to emamectin, indoxacarb, and chlorfenapyr were observed in all five populations. In contrast, the resistance to carbamates (thiodicarb or methomyl) was significantly higher than that of organophosphates, pyrethroids and newer chemistry insecticides. The pairwise correlation coefficients of LC₅₀ values indicated that the newer chemistry insecticides and old generation insecticides were not significant except abamectin, which was negatively significantly correlated with methomyl. A significant correlation was observed between thiodicarb, methomyl, and deltamethrin, whereas resistance to bifenthrin showed no correlations with resistance to other insecticides except deltamethrin. The results are discussed in relation to integrated pest management for S. litura with special reference to management of field evolved resistance to insecticides.     

Efficacy of two formulations of pirimiphos-methyl as surface treatment against Sitophilus granarius,Rhyzopertha dominica,and Tribolium confusum

In the present work, the insecticidal effect of two pirimiphos-methyl formulations [emulsifiable concentrate (EC) and capsule suspension (CS)] as surface treatment on concrete, plywood, galvanized metal, plastic, and ceramic tile was evaluated in laboratory bioassays against Sitophilus granarius (L.), Rhyzopertha dominica (F.), and Tribolium confusum Jacquelin du Val. Pirimiphos-methyl was applied at two-dose-rates, 0.01 and 0.1 mg/cm², and insect mortality was assessed after 1, 2, 3, 4, 5, 6, and 7 days of exposure. After the final mortality count, alive individuals were transferred to untreated dishes, and delayed mortality was evaluated after an additional period of 7 days. In another series of laboratory bioassays, the residual efficacy of these two pirimiphos-methyl formulations on concrete was evaluated against S. granarius, R. dominica, and T. confusum. Pirimiphos-methyl was applied at two-dose-rates, 0.01 and 0.1 mg/cm², on concrete dishes which were either kept in continuous darkness or exposed to light. A bioassay was initiated at the day of storage and every 4 weeks for 4 consecutive months (5 bioassays in total). Mortality of the exposed adult beetles was measured after 3 and 7 days of exposure. Both formulations were highly effective, with S. granarius being the most susceptible species. In general, mortality of the exposed beetles was not significantly affected by the surface type, with the exception of the significantly lower mortality counts of S. granarius adults on ceramic tile. CS appeared to be much more persistent on concrete than EC for all three species tested. Moreover, CS was not affected by light. In contrast, in some of the combinations tested, EC performance was poor in dishes that were exposed to light, in comparison with dishes that were in continuous darkness. We conclude that the surface type does not significantly and consistently affect S. granarius, R. dominica, and T. confusum mortality after surface application of the two pirimiphos-methyl formulations tested. Furthermore, CS can provide long-term protection when applied on concrete surfaces.     

Impact of agricultural adjuvants on the toxicity of the diamide insecticides chlorantraniliprole and flubendiamide on different life stages of the navel orangeworm (<Emphasis Type="Italic">Amyelois transitella</Emphasis>)

The navel orangeworm (Amyelois transitella) (Walker) is a destructive pest of tree nuts in California orchards. Overall demand for these crops and acreage expansions have resulted in significant insecticide applications to reduce A. transitella damage. Despite widespread use in A. transitella insecticide applications, the potential toxicity of adjuvants applied in combination with insecticides remains uncharacterized. In these experiments, five adjuvants (Cohere^®, Dyne-Amic^®, FastStrike^®, Induce^®, Latron B-1956^®), alone and in combination with the diamide insecticides chlorantraniliprole (Altacor^®) and flubendiamide (Belt^®), were assessed for activity against the adults and eggs of A. transitella. Laboratory studies utilized a spray tower for application while field studies used orchard air-blast sprayers. Laboratory exposure of both adults and eggs demonstrated that adjuvant toxicity varied across life stages. In the laboratory, the addition of chlorantraniliprole to adjuvants increased incapacity (dead + moribund). The results for flubendiamide were variable, and only FastStrike had the same high adult toxicity for both diamides. For eggs exposed to these diamides, overall mortality was similar. In field studies, Dyne-Amic and Latron B-1956 were tested and their adult toxicity varied. In contact assays, effects of adjuvants were similar when used with Belt^® and differed when used with Altacor^®. We conclude that the adjuvants for navel orangeworm management are intrinsically toxic to A. transitella in both the laboratory and field. Further studies are needed to attain the toxicity realized in the laboratory in field applications and also to determine whether our findings of adjuvant enhancement of insecticide toxicity are applicable to other insecticide classes.     

Chemical pre-treatments improve seed germination and seedling growth in <Emphasis Type="Italic">Semecarpus kurzii</Emphasis>: an ethnomedicinally important plant

Semecarpus kurzii Engl. is an important ethnomedicinal plant used for curing tumours, inflammation, fever and pain, and is also a source of iso ricinoleic acid. During the present investigation, effect of chemical pre-treatments on germination and seedling growth revealed significant differences. Different pre-treatments could improve germination and treatment with KNO₃ (9.9 mM) was significantly superior (94%) to the untreated control (76%). Mean daily germination varied among the treatments (0.90–4.14 seeds per day), when compared with 2.27 seeds per day in control. Mean germination time was significantly reduced from 22.14 days (control) to 16.40 days (19.8 mM KNO₃) and 17.16 days (1.45 mM GA₃). Treatment with KNO₃ (19.8 mM) and GA₃ (1.45 and 2.90 mM) significantly reduced the time for 50% germination. Treatment with higher concentrations of GA₃ and KNO₃ exhibited significantly faster germination initiation (11.0 and 12.0 days, respectively) over the control (17.0 days). Seedling vigour index was not improved by pre-treatments. Chemical treatments did not improve shoot growth, collar thickness, or number of seedling leaves; however, root growth was significantly improved over control. Treatment with GA₃ (2.90 mM) promoted leaf elongation but reduced leaf width significantly. Treatment with KNO₃ and GA₃ could be recommended to obtain healthy seedlings for establishing new plantations of this important medicinal plant species.     

Rapid predictions of cold tolerance in Douglas-fir seedlings using chlorophyll fluorescence after freezing

Chlorophyll fluorescence measurements were performed on the foliage of 3-year-old (11/2+11/2) nursery-grown Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings after exposure to controlled freezing temperatures, in the laboratory, to assess low temperature tolerance. The seedlings were propagated in an Irish nursery and lifted at monthly intervals overwinter 1999 and 1999–2000. Excised shoots from first-order laterals were frozen, in the dark. After freezing, needles were immediately assessed using chlorophyll fluorescence. The excised shoots were then maintained under controlled conditions for 14 days and visually assessed for needle damage. The chlorophyll fluorescence parameter, F _v/F _m, accurately predicted cold hardiness and was linearly related to visual needle damage and short-term survival. An equation was constructed using F _v/F _m data for determining the LT₅₀, that is, the freeze temperature causing 50% seedling damage. The predictions of F.LT₅₀ (fluorescence-based empirical determination of LT₅₀) have been tested over two seasons (i.e., against a second independent data set) with variability between 0 and 1.8°C of visual estimates, though predictions were often 1.1°C of the visual assessment. This approach provided a simple, rapid and accurate prediction of cold tolerance, under climatic conditions where in situ measurements are unreliable. The method can be used to predict if Douglas-fir seedlings have developed sufficient tolerance for lifting to the cold-store, or for planting.     

Effect of storage temperature on the insecticidal activity of a wettable powder formulation ofBacillus thuringiensis var.israelensis onCulex pipiens molestus larvae

Bactimos was incubated for 30 days under 7 constant temperatures (i. e. ?20, ?10, 5, 25, 35, 40 and 45°C). The insecticidal activity of the compound was evaluated against 2nd and 4th instar larvae ofCulex pipiens molestus after 1, 3, 7, 10, 15 and 30 days of storage. No loss in the insecticidal activity of the Bactimos was detected after 30 days at ?20, ?10 and 5°C. At temperatures above 25°C the insecticidal activity reduced as the storage period increased. The LT₅₀ value of Bactimos for the 2nd and 4th instar larvae at 24 h and 48 h exposure was found to decrease as the temperature increased.     

Potential of Metarhizium anisopliae and Beauveria bassiana in the control of tea termite Microtermes obesi Holmgren in vitro and under field conditions

Two strains of Metarhizium anisopliae (Metschnikoff) Sorokin and two strains of Beauveria bassiana (Ballsamo) Vuillemin were evaluated for their potential use as biological control agents against the tea termite Microtermes obesi Holmgren. The strains were screened for relative pathogenicity, and the median lethal time eliciting 50% mortality (LT₅₀) was calculated. In general, the M. anisopliae strains were more virulent with lower LT₅₀ values than B. bassiana strains. The LT₅₀ values ranged from 1.6 to 3.7 days. The median lethal concentrations (LC₅₀) of all the isolates were also determined. The M. anisopliae strains had low LC₅₀ values compared to B. bassiana strains. The LC₅₀ values ranged from 35 to 140 conidia per termite. The strains were also tested for survival under laboratory nest conditions. All the isolates exhibited the ability to grow, sporulate and produce an epizootic in treated nest material. Field applications of the isolates also produced promising results.     

Chemical composition,insecticidal and biochemical effects of essential oils of different plant species from Northern Egypt on the rice weevil,Sitophilus oryzae L.

The extensive use of synthetic insecticides and fumigants for control stored-product insects has led to the development of resistance. Essential oils from aromatic plants may provide proper alternatives to currently used insect control agents. Essential oils from 20 Egyptian plants were obtained by hydrodistillation. The chemical composition of the oils was identified by gas chromatograph/mass spectrometer. Fumigant and contact toxicities of the essential oils were evaluated against Sitophilus oryzae. The inhibitory effects of the essential oils on acetylcholinesterase and adenosine triphosphatases activities were examined. The oils were composed of monoterpene hydrocarbons (i.e., limonene, sabinene, β-pinene and γ-terpinene) and oxygenated monoterpenes (i.e., terpinen-4-ol, β–thujone, 4-terpineol, α-citral and 1,8-cineole) with the exception of the oil of Schinus terebinthifolius which was contained sesquiterpenes, and the oil of Vitex agnus-castus which contained similar amounts of monoterpenes and sesquiterpenes. In the fumigation assay, the oils of Origanum vulgare (LC₅₀ = 1.64 mg/L air), Citrus lemon (LC₅₀ = 9.89 mg/L air), Callistemon viminals (LC₅₀ = 16.17 mg/L air), Cupressus sempervirens (LC₅₀ = 17.16 mg/L air), and Citrus sinensis (LC₅₀ = 19.65 mg/L air) showed high toxicity to S. oryzae. In the contact assay, the oils of Artemisia judaica, C. viminals, and O. vulgare caused the highest toxicity to S. oryzae with LC₅₀ values of 0.08, 0.09, and 0.11 mg/cm², respectively. The oil of A. judaica (I₅₀ = 16.1 mg/L) invoked the highest inhibitory effect on AChE activity, while the oils of C. viminals and O. vulgare were the most potent inhibitors to ATPases activity with I₅₀ values of 4.69 and 6.07 mg/L, respectively. The results indicate that the essential oils of A. Judaica, O. vulgare, C. limon, C. viminals, and C. sempervirens could be applicable to the management of populations of S. oryzae.     

Field evolved resistance to carbamates,organophosphates, pyrethroids,and new chemistry insecticides in <Emphasis Type="Italic">Spodoptera litura</Emphasis> Fab. (Lepidoptera: Noctuidae)

Spodoptera litura Fab. (Lepidoptera, Noctuidae) is a polyphagous pest and has been shown to be resistant to a wide range of insecticides, which has led to sporadic out breaks of the pest and failure of crops. We were interested to establish if resistance to insecticides is diverse in different populations of S. litura collected from various areas with variable temperatures. We collected S. litura from eight different locations and compare the toxicity of insecticides. Resistance to the pyrethroids ranged from 20- to 11,700-fold compared with the Lab-PK (laboratory susceptible population). The resistance to bifenthrin was the lowest in a population collected from Multan and the highest to esfenvalerate in a population collected from Lodhran. Similarly, very high level of resistance to spinosad, indoxacarb, and methoxyfenozide was observed in all eight populations. In contrast, resistance to organophosphates was significantly lower than the pyrethroids, spinosad, indoxacarb, and methoxyfenozide, while toxicity of emamectin to field populations was similar to the Lab-Pk. The results are discussed in relation to integrated pest management (IPM) for S. litura with special reference to management of field evolved resistance to insecticides.     

Susceptibility of <Emphasis Type="Italic">Megachile rotundata</Emphasis> to insecticides used in wild blueberry production in Atlantic Canada

The alfalfa leafcutting bee, Megachile rotundata (Fabricius), is a valuable wild and managed pollinator of lowbush blueberry (syn. ‘wild blueberry’, Vaccinium angustifolium Ait.), in Atlantic Canada. As some insecticides may present a hazard to pollinators, we assessed the susceptibility of M. rotundata to insecticides used or projected for future use in lowbush blueberry pest management. In topical direct contact bioassays, adults were susceptible to phosmet, spinosad, spinetoram, and deltamethrin. Based on findings from these laboratory studies, it appears that when used at recommended or projected application rates, each of these compounds poses a hazard to M. rotundata by direct contact. In a second experiment, eggs and larvae were collected in the field and their pollen provisions were treated with deltamethrin, flubendiamide, and spinetoram at field relevant concentrations. Larvae treated with deltamethrin and spinetoram in the laboratory either died before spinning a cocoon or, in the case of spinetoram, occasionally pupated without spinning a cocoon. Flubendiamide was not toxic to adult M. rotundata by direct contact and had no effect on larval survivorship, or time to complete cocoon spinning. Emergence after overwintering was relatively poor overall, but there was no effect of treatment. Based on these results, flubendiamide appears safe to use in the presence of M. rotundata, whereas the other insecticides we tested may pose a hazard.     

马尾松毛虫抗药性监测

松毛虫是我国松林中的主要害虫。当前,化学防治松毛虫是主要方法之一,但是,长期连续使用化学药剂,会使松毛虫产生抗药性。为此,世界各国都十分重视有害生物抗药性的研究。世界卫生组织(WHO)和联合国粮农组织(FAO)相继成立了害虫抗药性专家工作小组委员会,针对不同害虫推荐了一系列抗药性的测定方法,建立测定网进行全球性调查。为建立起我国林业害虫抗药性监测网,使测定方法逐步标准化、规范化,我们制定了“松毛虫抗药性的测定方法”,开展了对马尾松毛虫(Dendrolimus punctatus Walker)抗药性的监测工作。现将测定结果报道如下。     

Fumigant activity of <Emphasis Type="Italic">Illicium verum</Emphasis> fruit extracts and their effects on the acetylcholinesterase and glutathione<Emphasis Type="Italic"> S</Emphasis>-transferase activities in adult <Emphasis Type="Italic">Sitophilus zeamais</Emphasis>

The insecticidal activity of Illicium verum Hook. f. against Sitophilus zeamais Motschulsky adults were identified, and the underlying mechanisms were studied. Extracts from I. verum fruits in methyl alcohol (MA), ethyl acetate (EA), and petroleum ether (PE) were tested by fumigation in a hermetic container to determine their toxicity. The effects of the three extracts on the activity of acetylcholinesterase (AChE) and glutathione S-transferases (GSTs) of S. zeamais were determined in vivo. All extracts showed strong fumigant activity. The fumigant effects were enhanced with increased dosage and prolonged exposure time. 1.25, 2.50, 5.00, 10.00, and 20.0 mg/l doses of the MA, EA, and PE extracts caused the mortalities from 8.37 to 90.26 %, 21.81 to 95.89 %, and 15.84 to 92.57 %, respectively, at 72 h after treatment. Consequently, the most effective dose of the MA, EA, and PE extracts is the 20.0 mg/l. The LD₅₀ of the MA, EA, and PE extracts at 72 h after treatment were 7.10, 3.93, and 4.55 mg/l, respectively. The activities of AChE and GSTs were notably inhibited by the three extracts, as compared with the control, with strong dose- and time-dependent effects. The inhibition strength of the three extracts on AChE and GSTs activities were in the following order: EA extract > PE extract ≥ MA extract. Therefore, I. verum extracts could be explored as novel natural fumigants for the future control of stored-product insect pests.     

Efficacy of low temperatures for the control of all life stages of <Emphasis Type="Italic">Plodia interpunctella</Emphasis> and <Emphasis Type="Italic">Liposcelis bostrychophila</Emphasis>

The insecticidal effect of low temperatures for the control of all life stages of two stored-product insects, Plodia interpunctella and Liposcelis bostrychophila, was evaluated under laboratory conditions. The temperatures tested were 0, ??5, ??10 and ??15 °C, and, at these temperatures, the insects were exposed for 2, 4 and 8 h and also for 1, 2, 3 and 7 days. Regarding P. interpunctella, the most cold-tolerant life stage was larvae, given that 2 days of exposure were needed for complete (100%) mortality at ??10 °C. Moreover, all larvae were dead at ??15 °C even after 2 h of exposure. Eggs of P. interpunctella were susceptible to cold, as mortality was complete after 7, 1 day, 2 and 2 h at 0, ??5, ??10 and ??15 °C, respectively. L. bostrychophila was by far less susceptible than P. interpunctella. For this species, adults were still alive even after 7 days at ??10 °C, while complete mortality was achieved only after 1 day at ??15 °C. Eggs of L. bostrychophila were the most cold-tolerant life stage, as survival was observed even after 3 days at ??15 °C. The results of the present study provide the first data set on which all life stages of P. interpunctella and L. bostrychophila are evaluated for their susceptibility to cold treatments in a standardized series of exposures and temperatures. These results are expected to further encourage the “real world” application of cold treatments for the disinfestation of durable stored-products.