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 spirotetramat on the mealybug destroyer, Cryptolaemus montrouzieri

Spirotetramat is a new systemic insecticide listed in Group 23 of the IRAC mode-of-action classification scheme as an inhibitor of lipid biosynthesis. Side effects assessment on key natural enemies is necessary before incorporating a pesticide in IPM programs. Herein, lethal and sublethal side effects of spirotetramat on adults and larvae of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) were evaluated under laboratory conditions by topical application and by ingestion of treated individuals of Planococcus citri Risso (Hemiptera: Pseudococcidae). The lethal and sublethal effects of spirotetramat were compared to those of chlorpyriphos and pyriproxyfen, two insecticides commonly used in Spanish citrus. Spirotetramat resulted harmless: (1) when directly applied on larvae and adults of C. montrouzieri, since it did not affect survival, longevity, fecundity, egg hatching, and offspring survival. In contrast, chlorpyriphos was classified as moderately toxic for adults due to its effects on fecundity, egg hatching and offspring survival. Pyriproxyfen was classified as harmful for larvae due to the acute effect on pupal mortality. When larvae and adults of C. montrouzieri were fed with treated prey, spirotetramat was also classified as harmless. Adults of C. montrouzieri fed with pyriproxyfen-treated prey exhibited increased fecundity but no eggs hatched. Moreover, the larvae fed on pyriproxyfen-treated prey did not reach the adult stage. The results of this study indicate that spirotetramat may be compatible with augmentative releases of C. montrouzieri in citrus.     

The effects of cold pre-treatment on the toxicity of several contact insecticides on adults of three Sitophilus granarius (L.) populations

As very little is known about the impact of cold pre-treatments on insecticidal toxicity to the surviving stored-product insects, we examined the effects of cooling (?5 °C) on the toxicity of five contact insecticides to Sitophilus granarius adults from three populations (laboratory, field and selected). We determined: (a) weevil lethal time after exposure to ?5 °C, (b) the effects of two cold pre-treatments (LT₂₀ and LT₅₀—lethal time for 20 and 50 % of exposed adults) on 24 and 72 h recovery rates of laboratory adults after exposure to five insecticides and (c) deltamethrin, dichlorvos and malathion toxicity to two weevil populations with altered insecticide susceptibility after exposure to the LT₂₀ and LT₅₀ pre-treatments. The tested S. granarius populations showed no significant differences in their susceptibility to cooling. All insecticides except dichlorvos were more toxic to the laboratory weevils after 24 h than after 72 h recovery from the LT₂₀ pre-treatment. Dichlorvos and deltamethrin were more toxic to the other two populations after 72 h of recovery. Comparing the effects of cold pre-treatment and non-treatment on the laboratory strain, no significant increase in the toxicity of insecticides was detected, while only deltamethrin was significantly more toxic to the field and selected populations recovering for 24 h (12.1 and 11.0 times, respectively) and 72 h (6.9 and 36.6 times) from the LT₂₀ pre-treatment. In conclusion, only the shorter of the two cold pre-treatments was found effective in terms of increasing the insecticidal toxicity, especially against the populations with altered susceptibility to insecticides.     

Direct and admixture toxicity of diatomaceous earth and monoterpenoids against the storage pests <Emphasis Type="Italic">Callosobruchus</Emphasis><Emphasis Type="Italic">maculatus</Emphasis> (F.) and <Emphasis Type="Italic">Sitophilus oryzae</Emphasis> (L.)

We investigated the effects of two commercial diatomaceous earth based insecticides (DE), Protect-It^® and SilicoSec^®, the nano-structured silica product AL06, developed by the section for Urban Plant Ecophysiology at Humboldt University Berlin, and the monoterpenoids, eugenol, and cinnamaldehyde on two stored product pests, Callosobruchus maculatus and Sitophilus oryzae. Protect-It^® was more effective than SilicoSec^® against C. maculatus while the reverse was true for S. oryzae. Generally C. maculatus was more sensitive towards DE and silica treatment than S. oryzae. Mortality rate of both pest species increased when DE’s were applied to food commodities previously treated with a monoterpenoid. In admixture experiments, the toxicity of SilicoSec^® + cinnamaldehyde (LD₅₀ = 42.73 ppm), SilicoSec^® + eugenol (LD₅₀ = 24.30 ppm), and Protect-It^® + eugenol (LD₅₀ = 2.60 ppm) was increased over DE alone against S. oryzae. Both substances showed a synergistic effect considering their co-toxicity coefficient relative to the LD₅₀-value. In contrast, we could not find any synergistic effects in experiments with C. maculatus. Here only Protect-It^® + cinnamaldehyde (LD₅₀ = 20.84 ppm) showed an additive effect while all other combinations of monoterpenoid and DE indicated antagonistic effects. In addition to contact insecticidal effects both monoterpenoids showed a strong fumigant action. The presented results indicate that the natural product DE has great potential to replace synthetic pesticides commonly used in stored product pest management. Efficacy of DE can be improved by adding certain monoterpenoids against certain insect pests.     

Susceptibility of the Mexican bean beetle <Emphasis Type="Italic">Epilachna varivestis</Emphasis> Mulsant (Coleoptera: Coccinellidae) to endemic isolates of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae)

Entomopathogenic fungi represent excellent candidates for biological insecticides. Among the many entomopathogenic fungi, Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) is one of the most promising species. Here, we report the results of infection studies performed using four B. bassiana native isolates (Bb37, Bb38, Bb40, and Bb45) compared with the commercial product Mycotrol^® (strain GHA) on adult Mexican bean beetle Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), one of the most important pests of bean production in Mexico. First, single concentration (1 × 10⁸ conidia mL^?1) assays were carried out using all isolates applied using an immersion method. Examinations at 10 days after inoculation indicated that isolates Bb37, Bb38, and Bb40 significantly reduced adult survival, causing 60–75% mortality compared to the commercial strain GHA (33%) and control (29%). Second, using two selected isolates (Bb37 and Bb40), the mean lethal concentration values (LC₅₀) were estimated for third instar larvae and adult E. varivestis. The LC₅₀ values for Bb37 and Bb40 isolates decreased 5.26-fold and 3.19-fold, respectively, in third instars compared with adults. However, such difference for Bb40 isolate was not significant. Finally, an experiment, to compare the median survival time (MST) values between third instar and adult E. varivestis, was conducted using Bb37 and Bb40 at 1 × 10⁹ conidia mL^?1. MST values were significantly reduced against larvae (87 and 100 h) compared with adults (130 and 134 h) by Bb37 and Bb40, respectively. We conclude that native isolates of B. bassiana represent an important alternative for the control of E. varivestis. However, to demonstrate its effectiveness under field conditions, detailed studies are needed.     

Zur Wirkung einiger organischer Phosphor-Präparate in subletaler Dosis aufSpodoptera littoralis (Boisd.) (Lep. Noctuidae)

Zusammenfassung Das 4. Stadium der Larven von.S. littoralis wurde mit der maximalen nichtletalen Dosis (LD₀) sowie den subletalen Dosen (LD₁₀ und LD₅₀) der 3 Insektizide Cyolane, Monocrotophos und Phosvel im Laboratorium behandelt. Die überlebenden Individuen wurden bis zum Ausschlüpfen der Falter gezogen und anschließend auf ihre Biproduktion untersucht. Die max. LD₀ wirkte stimulierend auf die Eiproduktion, So betrug der prozentuale Anstieg der täglich abgelegten Eizahl je Weibchen in 5 Tagen 70,6% nach Cyolane-, 60,4% nach Monocrotophos- und 34,5% nach Phosvelbehandlung.Die subletalen Dosen wirkten unterschiedlich auf die Eiproduktion. Die LD₁₀ verursachte eine Vermindung, dagegen eine Erhöhung der Eizahl um 12,2% derung der Eizahl um 12,4% nach Cyolane-Anwenper female during 5 days was the following: 70,6%, nach Monocrotophos- und um 7,3% nach Phosvelanwendung. Die LD₅₀ verminderte die Eizahl um 34,6% bei Monocrotophos, führte dagegen bei Phosvel zu einem geringen Anstieg von 3,3%.Die LD₅₀ der 3 Insektizide hatte, verglichen mit der Kontrolle, eine Abnahme des Verpuppungsprozentes, eine Erhöhung der Sterberate bei den Larven und Puppen und eine Störung der Sexualrate zugunsten der mä nnlichen Falter zur Folge, während sich die max. LD₀ und LD₁₀ der o. g. Insektizide auf die Sexualrate, verglichen mit der Kontrolle, zugunsten der weiblichen Falter auswirkten. Im allgemeinen verhielt sich das Verpuppungsprozent umgekehrt proportional zur Insektiziddosis, während die Sterberate für Larven und Puppen proportional der Insektiziddosis war. Alle max. LD₀ hatten nur einen geringen Einfluß auf das Verpuppungsprozent.

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Summary The 4th instar larvae ofS. littoralis (Boisd.) was treated in the laboratory with the maximal non lethal dose (max. LD₀) and the sublethal doses (LD₁₀ and LD₅₀) of 3 insecticides (Cyolane, Monocrotophos and Phosvel). Surviving larvae reared to imagines, and then tested on the egg production. The max. LD₀ of the aforementioned insecticides showed a stimulation effect on the egg production of the females. The percentage of increase in the number of eggs produced 60,4%, 34,5% after Cyolane, Monocrotophos, and Phosvel treatment respect.The sublethal doses showed different effects on the egg production: LD₁₀ decreased the percentage of eggs of 12,4% after Cyolane treatment, while Monocrotophos and Phosvel increased the same (12,2% and 7,3% respect.). LD₅₀ decreased the percentage number of eggs (34,6% after Monocrotophos treatment) and there was a slight increase after Phosvel treatment (3,3%). LD₅₀ furthermore decreased the percent pupation, increased the mortality of the larvae and pupae and disturbed the sex ratio for the benefit of the males, compared with the control, while the max. LD₀ and LD₁₀ of the 3 insecticides affected the sex ratio for the benefit of the females. The percent pupation in general was in inverse relation to the insecticide dose, while the mortality of the larvae and pupae was in proportional relation to the insecticide dose. All max. LD₀ have shown a slight influence on the percent pupation compared with the Control.

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Faris El- Lakwah, Dozent, Polytechn. Institut Cairo, Dep. Agriculture, Moshtohor, A. R. E. — Farid A. Abdel-Salam, Ass.-Prof., Central Laboratory for Pesticides (CAPL), Ministry of Agriculture, Cairo-Dokki, A. R. E.     

Efficacy of endosulfan and fipronil and joint toxic action of endosulfan mixtures against Leptinotarsa decemlineata (Say)

The Colorado potato beetle (Leptinotarsa decemlineata [Say]) in the north Xinjiang Uygur autonomous region in China has evolved resistance to pyrethroids and carbamates. Mutations resulting in target site insensitivity, namely L1014F in LdVssc1 voltage-sensitive sodium channel and S291G in acetylcholine esterase, confer, at least partially, the resistance. Insecticides with different modes of action may serve as likely replacements. Endosulfan and fipronil are GABA-gated chloride channel-blocking insecticides. In this article, we found that the contact toxicities of the two compounds were among the highest ever estimated to the 4th-instar larvae and the adults and affirmed that they were useful for L. decemlineata control in north Xinjiang. Regarding stomach toxicities of the two compounds, adult beetles were less sensitive than 2nd-, 3rd-, and 4th-instar larvae, suggesting that the appropriate timing for spraying is the early larval stage. Mixtures of endosulfan and α-cypermethrin at 1:160, 1:80, and 1:40 ratios, of endosulfan and phoxim at 1:24 ratio, and of endosulfan and isocarbophos at 1:72 and 1:288 ratios, significantly increased toxicity in a field population. The combination indices were significantly below 1 at both LD₅₀ and LD₉₀ levels, revealing synergistic effects. Our results demonstrated that endosulfan and fipronil could be applied alone and endosulfan may also be used in binary mixtures to restore pyrethroid susceptibility. These findings may have considerable practical implications for L. decemlineata resistance management.     

Side effects of selected insecticides on the <Emphasis Type="Italic">Tuta absoluta</Emphasis> (Lepidoptera: Gelechiidae) predators <Emphasis Type="Italic">Macrolophus pygmaeus</Emphasis> and <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis> (Hemiptera: Miridae)

Tuta absoluta is a pest native to South America that produces significant damage to tomato crops and was first detected in Europe in late 2006. Data obtained during 2008 from commercial tomato crops in which IPM was applied suggested that good pest control was possible through the combined action of the predatory mirid bugs Macrolophus pygmaeus and Nesidiocoris tenuis and the use of selective insecticides. The aim of our study was to evaluate the lethal and sublethal side effects of three of the insecticides most widely used to control T. absoluta on these predators: azadirachtin, spinosad and indoxacarb. Seven days after applying the treatment at the maximum recommended field rates, the mortality produced by indoxacarb ranged from 28% for nymphs of M. pygmaeus to 77% for females of N. tenuis and were significantly higher than those produced by azadirachtin, spinosad and the control (<13%). However, indoxacarb did not affect the number of descendants of females exposed to residues during the last days of their preimaginal development. In contrast, spinosad significantly reduced the offspring of M. pygmaeus and azadirachtin significantly reduced the offspring of N. tenuis females. The sublethal effects of azadirachtin and spinosad on predator reproduction should therefore not be ignored. This information could be useful when selecting the most appropriate insecticide to control T. absoluta in greenhouses and field crops in which M. pygmaeus and N. tenuis are used as biological control agents.     

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested.     

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.     

Food source provisioning and susceptibility of immature and adult<Emphasis Type="Italic"> Tribolium castaneum</Emphasis> on concrete partially treated with chlorfenapyr (Phantom<Superscript>®</Superscript>)

A series of experiments were conducted in which adults, pupae, and 4-week-old larvae of Tribolium castaneum (Herbst), the red flour beetle, were exposed separately on concrete arenas partially treated (14.4% of the total area) with the insecticide chlorfenapyr (Phantom^®) at 1.1 g of active ingredient/m². A flour food source (patch) was also provided in the untreated portions of the arenas. In the first trial, adult mortality averaged 60.0 ± 10.6%, but progeny production occurred in the provided food patches. Pupal mortality was only 8.3 ± 3.1%, indicating that when adult emergence occurred, those adults were able to escape exposure, and there was no difference in progeny production from that in untreated controls (P = 0.27). In the second trial, few larvae exposed in choice and no-choice arenas were able to emerge as normal adults. In a final trial, residual efficacy declined during a 3-week period, with larvae being more susceptible than adults. Results show mobility of life stage may be a determining factor when assessing susceptibility of T. castaneum to contact insecticides.     

Susceptibility of different life stages of Tribolium confusum to pyrethrin aerosol: effects of a flour food source on insecticidal efficacy

Accumulated grain dust and flour residues in flour mills can potentially decrease the efficacy of contact surface treatments and aerosol insecticides used for control of adult and immature stages of stored product insects. A study was conducted to evaluate the effects of flour residues on the efficacy of piperonyl butoxide-synergized pyrethrin aerosol against different life stages of the confused flour beetle, Tribolium confusum Jacquelin du Val. Twenty individual adults, pupae, or larvae of T. confusum, confined in Petri dishes containing 0, 0.1, 1, 5, or 10 g of wheat flour, were exposed separately inside an empty shed to the label rate of the aerosol. The formulation contained 1 % active ingredient pyrethrin and the label application rate was 1.04 ml/m³. After 2 h of exposure, all dishes were removed from the shed and placed in an incubator set at 27 °C and 60 % RH. Mortality of T. confusum adults decreased with increasing amount of flour. Recovery of moribund adults 15 days after exposure was greater in the 5 and 10 g flour dishes (15 and 46 %) compared to the 0.1 or 1 g flour dishes (0.7 and 5 %). As the flour amounts increased, more larvae and pupae were able to emerge as adults. Results show accumulated flour residues during aerosol application can compromise aerosol efficacy, and also suggest the flour impaired penetration ability of the aerosol. These results also emphasize the importance of sanitation and cleaning to remove spillage and extraneous material prior to an aerosol application.     

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.     

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.     

Effects of insect activity, soil, and cuticular factors on virulence of Beauveria bassiana toward Blissus leucopterus hirtus

The fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) is a potential biological control agent of hairy chinch bug, Blissus leucopterus hirtus Montandon (Hemiptera: Lygaeidae), but its virulence against this important turf grass pest is limited. To gain insight into why high numbers of conidia are needed for rapid kill, conidial persistence on insects was monitored under several experimental conditions. One day after exposure to a concentrated B. bassiana suspension, most conidia were removed from insects, particularly at warmer temperatures. Removal was higher when soil was present, suggesting that the insects may have transferred the conidia to soil. Most conidia on insects lost viability within 2?days. In contrast, conidia stored in soil under the same conditions as the insects remained viable. Earlier instar nymphs were more susceptible to lethal fungal infection than were adults. Materials recovered from a hexane rinse of adult insects inhibited conidial germination. These results have implications for applied aspects of chinch bug biological control with B. bassiana.     

Evaluation of spinetoram and spinosad for control of Prostephanus truncatus,Rhyzopertha dominica,Sitophilus oryzae,and Tribolium confusum on stored grains under laboratory tests

Spinetoram and spinosad have been evaluated against certain stored-product insect pests with success but there are no data available on the comparison of the efficacy of these two novel compounds in stored grains. Thus, laboratory bioassays were conducted to compare spinetoram and spinosad as grain protectants against Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) adults and larvae. Factors such as treatment (1 ppm spinetoram, 1 ppm spinosad, 0.1 ppm spinetoram + 0.9 ppm spinosad, 0.5 ppm spinetoram + 0.5 ppm spinosad, and 0.9 ppm spinetoram + 0.1 ppm spinosad), exposure interval (1, 2, 7, and 14 days), temperature (20, 25, and 30 °C), and commodity (barley, maize, rye, and wheat) were evaluated. Progeny production was assessed after 60 days of exposure. Concerning temperatures, for P. truncatus adults, after 14 days of exposure, all adults were dead in treatments except of the case of spinosad alone at 20 °C. Offspring emergence was completely suppressed in all treatments at 20 and 25 °C. For R. dominica adults, after 7 days of exposure, the overall mortality ranged from 92.8 to 100 %. After 14 days of exposure, all adults were dead in all treatments of the combined use of spinetoram and spinosad at 25 and 30 °C. Progeny production was completely suppressed in all treatments at 30 °C. For S. oryzae adults, after 7 days of exposure, all S. oryzae were died at 25 and 30 °C in all treatments except in the case of spinosad alone. Offspring emergence was very low in all treatments and temperatures except in the case of spinosad alone at 30 °C. For T. confusum adults, after 1, 2, and 7 days of exposure, the overall mortality was low in all treatments and temperatures. Concerning commodities, for R. dominica adults, after 7 and 14 days of exposure, the overall mortality was >97 %. Offspring emergence was very low in all commodities. For S. oryzae adults, after 7 and 14 days of exposure, the overall mortality was increased exceeding 91 % except in the case of spinosad alone 7 days after exposure in barley. Progeny production was high in barley and rye in all treatments. For T. confusum adults, after 7 and 14 days, the overall mortality was low in barley, rye, and wheat. No offspring emergence was recorded in all treatments and commodities. For T. confusum larvae, after 14 days of exposure mortality was further increased, but did not reach 100 % for any of the combinations tested. The results of the present study suggest that the simultaneous application of spinetoram and spinosad was generally equally effective with the use of either spinosad or spinetoram alone. Furthermore, the increase of dose of either compound resulted in the same mortality levels. Thus, no benefits were achieved when spinetoram and spinosad were used simultaneously on grains, regardless of the proportion of each ingredient. These issues should be seriously considered when control measures against stored-product insects are designed.     

The effects of different rearing diet media on the irradiated pupae and adults of flour beetle,Tribolium confusum (J. du val)

In this study, gamma radiation was applied between 10–120 Gy at 10 dose levels for 2–4 days-old pupae; 10–150 Gy at 11 dose levels for 12–14 days-old adults ofT. confusum. All experiments were carried out in incubators maintained at 27±0.5°C and 70±5% relative humidity. The development of adults reared on different flours from irradiated pupae was not prevented by exposing these stages investigated doses. Rapidly developing confused flour beetle were more susceptible to killing by gamma radiation. Adults that emerged from treated pupa had elytral and other deformities. In barley flour, rate of deformed individuals were higher than the other rearing media. LD₅₀, LD_99,9 and SD_99,9 values for wheat flour were high compared with both barley and maize flour. For adult treatment, there were differences in survival among rearing diets especially at doses of 40, 50 and 60 Gys. But there were no differences for LD₅₀ and LD_99,9 values at adult stage, indicating little influence of rearing medium on susceptibility of adults. On the other hand, there were little differences between rearing diets for SD₅₀ and SD_99,9.With 6 tables and 4 figures     

Toxicity and repellence of Taiwanese indigenous djulis, Chenopodium formosaneum, against Aedes albopictus (Diptera: Culicidae) and Forcipomyia taiwana (Diptera: Ceratopogonidae)

The biological activity of djulis (Chenopodium formosaneum) extracts was evaluated against mosquitoes and biting midges. Djulis extracts were relatively nontoxic to Aedes albopictus larvae. However, they showed interesting repellence against adult mosquitoes as estimated by the median effective dosages (ED₅₀). ED₅₀ values for djulis extracts against mosquito adults in descending order were: seed extracted with methanol (0.83 %), seed extracted with dichloromethane (0.66 %), leaf extracted with methanol (0.50 %), and leaf extracted with dichloromethane (0.40 %). Field tests also suggested that djulis methanol extracts were effective at about a 1 % level against biting midges (Forcipomyia taiwana). A total of 15 and 20 compounds accounting for 88.8 and 79.9 % in the seed and leaf extract, respectively were identified by gas chromatography coupled to mass spectrometry (GC–MS). Among these, 9, 12-octadecadienoyl chloride, (Z, Z) was found in both as well as being the major constituent in the leaf extract (35.7 %). Further studies on the repellent property of the extracts against mosquitoes and biting midges are warranted.     

Physical barriers for suppression of movement of adult stink bugs into cotton

Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say) (Heteroptera: Pentatomidae) are economic pests of cotton in the southeastern USA. Because adult stink bugs exhibit edge-mediated dispersal at crop-to-crop interfaces as they colonize cotton, strategic placement of physical barriers at these interfaces could manage these pests. The objective of this study was to determine the effectiveness of a physical barrier, either synthetic or plant-based, at the peanut-to-cotton interface for suppressing stink bugs that would move to cotton. In 2012 and 2013, sorghum sudangrass (2.4 and 2.1 m high, respectively) was significantly taller than cotton (1.4 and 1.3 m high, respectively) which was taller than peanut (0.4 and 0.5 m high, respectively). Buckwheat (0.6 m high), planted only in 2012, was significantly taller than peanut, but shorter than cotton. For both years of the study, sorghum sudangrass and a 1.8-m-high polypropylene barrier wall effectively deterred dispersal of stink bugs into cotton. Because each of these barriers was taller than cotton, their success in protecting cotton likely was due to disruption of the flight of stink bugs from low-growing peanut into cotton. The shortest barrier wall (0.6-m-high) did not suppress stink bug dispersal into cotton probably because it was approximately the same height as peanut. In 2012, flowering buckwheat increased the efficacy of Trichopoda pennipes (F.) attacking N. viridula in cotton although it did not deter dispersal of stink bugs. In conclusion, a barrier at least as tall as cotton can effectively retard the entry of stink bug adults into cotton.     

Field evaluation of an attract and kill strategy against western corn rootworm larvae

The larvae of the invasive maize pest Diabrotica virgifera virgifera (Coleoptera; Chrysomelidae, western corn rootworm) hatch in the soil in spring and search for maize roots following CO₂ gradients. CO₂ is one cue that might be used as an attractant towards soil insecticides, a mechanism already shown in laboratory experiments. This study compared the efficacy of several combinations of in or between-row applications of different rates of CO₂-emitting capsules and/or soil insecticides (here tefluthrin) aimed at preventing root damage by the pest larvae under field conditions. CO₂ emission of the capsules in the soil lasted up to 28 days with a peak after 21 days coinciding with the first larval hatch. The pest density in the soil was not high enough to cause root damage above the economic threshold. Furthermore all tefluthrin applications, regardless of whether at full, half or quarter rates effectively prevented root damage; thus CO₂ did not significantly further increase this efficacy. In-row applications of tefluthrin with or without CO₂-emitting capsules prevented root damage to a much larger extent (59–77 % on the node injury scale) than the between-row applications of tefluthrin with or without capsules (17–31 %). In conclusion, further research on belowground orientation and movement of D. v. virgifera larvae, as well as tests with combinations of CO₂-emitting capsules and lower rates of soil insecticide are needed to potentially develop attract and kill strategies as a management option against this maize pest.