Topical Application Bioassays Research Articles

Mosquito Adult Bioassays.

Topical application and bottle bioassays measure the responses of adult mosquitoes to specific doses of an insecticide (dose-response). Topical application bioassays are generally used to measure the dose-response of adult mosquitoes to insecticides in which the amount (dose) of insecticides the mosquitoes receive is known in the laboratory. Here, a 0.5-µL drop of the insecticide dissolved in a relatively nontoxic solvent, such as acetone, is applied to the thorax of insects, and the insects' susceptibility to the insecticide is determined in terms of either the median lethal dose (LD50) or 90% of the mortality lethal dose (LD90). Bottle bioassays measure the dose-responses in which the exact amount of insecticide in a bottle is known while the exact amount of insecticide that mosquitoes (field-collected or laboratory-susceptible) receive is not known. Bottle bioassays can be either single dose tests or multiple dose applications. The bottle bioassay described in this protocol is a modified form of the World Health Organization (WHO) and U.S. Centers for Disease Control (CDC) bottle bioassays. For the single bottle assay, a detailed protocol with the amount (dose/bottle) of each insecticide and threshold times is provided by the CDC; here we provide protocols for topical and bottle bioassay applications with multiple doses.

Comparison of the variability in mortality data generated by CDC bottle bioassay, WHO tube test, and topical application bioassay using Aedes aegypti mosquitoes

BackgroundInsecticide resistance remains a major public health problem. Resistance surveillance is critical for effective vector control and resistance management planning. Commonly used insecticide susceptibility bioassays for mosquitoes are the CDC bottle bioassay and the WHO tube test. Less commonly used in the field but considered the gold standard for assessing insecticide susceptibility in the development of novel insecticides is the topical application bioassay. Each of these bioassays has critical differences in how they assess insecticide susceptibility that impacts their ability to differentiate between resistant and susceptible populations or determine different levels of resistance intensity.MethodsWe compared the CDC bottle bioassay, the WHO tube test, and the topical application bioassay in establishing the dose–response against deltamethrin (DM) using the DM-resistant Aedes aegypti strain MC1. Mosquitoes were exposed to a range of insecticide concentrations to establish a dose–response curve and assess variation around model predictions. In addition, 10 replicates of 20–25 mosquitoes were exposed to a fixed dose with intermediate mortality to assess the degree of variation in mortality.ResultsThe topical application bioassay exhibited the lowest amount of variation in the dose–response data, followed by the WHO tube test. The CDC bottle bioassay had the highest level of variation. In the fixed-dose experiment, a higher variance was similarly found for the CDC bottle bioassay compared with the WHO tube test and topical application bioassay.ConclusionThese data suggest that the CDC bottle bioassay has the lowest power and the topical application bioassay the highest power to differentiate between resistant and susceptible populations and assess changes over time and between populations. This observation has significant implications for the interpretation of surveillance results from different assays. Ultimately, it will be important to discuss optimal insecticide resistance surveillance tools in terms of the surveillance objective, practicality in the field, and accuracy of the tool to reach that objective.Graphical

Insecticidal Activities and GC-MS Analysis of the Selected Family Members of Meliaceae Used Traditionally as Insecticides.

The environmental and health risks associated with synthetic pesticides have increased the demand for botanical insecticides as safer and biodegradable alternatives to control insect pests in agriculture. Hence in this study, five Meliaceae species were evaluated for their insecticidal activities against the Spodoptera frugiperda and the Plutella xylostella larvae, as well as their chemical constituents. Repellence, feeding deterrence, and topical application bioassays were employed to evaluate their insecticidal activities. GC-MS analysis was performed to identify chemical compounds present in each plant. The repellence bioassay indicated that Melia azedarach extracts exhibited the highest repellence percentage against S. frugiperda (95%) and P. xylostella (90%). The feeding deterrence bioassay showed that M. azedarach and Trichilia dregeana extracts displayed excellent antifeeding activity against the S. frugiperda (deterrent coefficient, 83.95) and P. xylostella (deterrent coefficient, 112.25), respectively. The topical application bioassay demonstrated that Ekebergia capensis extracts had the highest larval mortality against S. frugiperda (LD50 0.14 mg/kg). Conversely, M. azedarach extracts showed the highest larval mortality against P. xylostella (LD50 0.14 mg/kg). GC-MS analysis revealed that all plant extracts had compounds belonging to the two noteworthy groups (phenols and terpenes), which possess insecticidal properties. Overall, this study lends scientific credence to the folkloric use of Meliaceae species as potential biocontrol agents against insect pests.

Essential Oils as a Source of Ecofriendly Insecticides for Drosophila suzukii (Diptera: Drosophilidae) and Their Potential Non-Target Effects.

The spotted wing drosophila (Drosophila suzukii) is one of the main invasive pests of small fruits in the world. Thus, 19 essential oils (EOs) were selected to analyze the effects through toxicity and repellency on oviposition and D. suzukii adults. In addition, their lethal and sublethal effects on the pupal endoparasitoid Trichopria anastrephae were evaluated. The EOs of C. flexuosus and Mentha spp. had the highest toxicity observed in the topical application bioassay for D. suzukii. In contrast, the EOs of C. verum, C. citratus QT citratus, and C. winterianus showed the highest toxicity in the ingestion bioassay for D. suzukii. The dry residues of C. verum and C. citratus QT citratus reduced the oviposition of D. suzukii. In the repellency bioassays, the 19 EOs analyzed repelled ≅ 90% of the D. suzukii females. All EOs evaluated using the LC90 values of the products provided mortality of less than 20% of T. anastrephae adults and did not cause a reduction in the parasitism of surviving T. anastrephae females. We conclude that the EOs evaluated have the potential to be used in the management of D. suzukii. They can also serve as selective active ingredients for the formulation and synthesis of new biopesticides.

Insecticidal Effect of Pistacia lentiscus (Anacardiaceae) Metabolites against Lobesia botrana (Lepidoptera: Tortricidae)

The extensive use of synthetic insecticides in agriculture poses a great risk for human health and the ecosystem, and mandates the development of safer alternatives derived from natural products. In the present study, we assessed the larvicidal effect of Pistacia lentiscus fruits, leaves, and bark extracts and their components on larvae of a major vine pest, Lobesia botrana. Pistacia lentiscus is an evergreen shrub or small tree possessing significant medicinal value with numerous therapeutic uses since antiquity. Using petri dish residual exposure and topical application bioassays we demonstrated that the fruit extract of P. lentiscus and its metabolites were toxic on L. botrana larvae. Extracts from leaves and bark showed no effect. Βioassay-guided fractionation of P. lentiscus fruit hexane extract led to the identification of its constituents with insecticidal properties on L. botrana larvae. Specifically, we have identified that the main contributor to the bioactivity of the hexane extract of P. lentiscus fruits is its major fraction, PLFHe2 (76.25%). Furthermore, we have found that PLFHe2 is a mixture of triglycerides and that the fatty acids responsible for the observed toxicity are oleic and linoleic acid.

A Practical Insecticide Resistance Monitoring Bioassay for Orally Ingested Dinotefuran in Anopheles Malaria Vectors.

Simple SummaryWhen insecticides are used to control mosquitoes, resistance is likely to develop over time. It is important to monitor the trait so that an alternative insecticide class can be deployed if needed, to sustain the efficiency of the intervention. Most insecticides for control of adult malaria vectors are used in treated bed nets or sprayed on walls where mosquitoes rest, so that mosquitoes contact them through their tarsi (feet). To control mosquitoes which are becoming resistant to these tools, new insecticide-based tools using both different chemistry and mode of uptake have been developed. One example of these is Attractive Toxic Sugar Baits (ATSBs), from which mosquitoes feed and ingest insecticide that kills them. However, different methods may be needed to monitor for resistance against interventions that have different modes of uptake. This study employed a method for applying insecticide directly onto a mosquito and measuring mortality, and the results were related to mortality from the same insecticide when ingested. This demonstrated that the method may be suitable to detect signs of resistance developing in mosquito populations targeted with ATSBs. Application of the method in wild populations will provide further validation.Attractive Toxic Sugar Baits (ATSB) deployed outdoors are likely to be particularly effective against outdoor biting mosquitoes and, if they contain insecticides with a different mode of action, mosquitoes resistant to pyrethroids. One such ATSB based on the neonicotinoid dinotefuran is currently under evaluation in Africa. As with any insecticide-based intervention, it will be important to monitor for the possible emergence of vector resistance. While methods for detecting resistance to insecticides via tarsal contact are recommended by the World Health Organization (WHO), these may not be applicable for orally ingested insecticides. Here, a new ingestion assay, appropriate for a controlled laboratory setting, is described using fluorescein sodium salt (uranine) as a feeding marker. Conventional topical application bioassays, more appropriate for routine deployment, have also been used to apply dinotefuran to the thorax of adult Anopheles mosquitoes with an organic carrier to bypass lipid cuticle barriers. The two methods were compared by establishing lethal doses (LD) in several Anopheles strains. The similarity of the ratios of susceptibility to dinotefuran between pairs of pyrethroid susceptible and resistant strains validates topical application as a suitable, more practical and field applicable method for monitoring for the emergence of resistance to orally ingested dinotefuran. A discriminating dose is proposed, which will be further validated against field populations and used to routinely monitor for the emergence of resistance alongside ATSB trials.

Topical Application Bioassay to Quantify Insecticide Toxicity for Mosquitoes and Fruit Flies

The continued use of insecticides for public health and agriculture has led to widespread insecticide resistance and hampering of control methods. Insecticide resistance surveillance of mosquito populations is typically done through Centers for Disease Control and Prevention (CDC) bottle bioassays or World Health Organization (WHO) tube tests. However, these methods can result in a high degree of variability in mortality data due to variable insecticide contact with the insect, the relatively small numbers of organisms tested, extensive variation in mass between populations, and constantly changing environmental conditions, leading to variable outcomes. This paper presents the topical application bioassay, adapted as a high-throughput phenotypic bioassay for both mosquitoes and fruit flies, to test large numbers of insects along a range of insecticide concentrations. This assay 1) ensures consistent treatment and insecticide contact with every organism, 2) produces highly specific dose-response curves that account for differences in average mass between strains and sexes (which is particularly important for field-collected organisms), and 3) allows for the calculation of statistically rigorous median lethal doses (LD50), which are necessary for resistance ratio comparisons-an alternative surveillance approach from diagnostic dose mortality, which is also used for larvicide resistance surveillance. This assay will be a complementary tool for accurately phenotyping mosquito populations and, as illustrated using fruit flies, is easily adaptable for use with other insects. We argue that this assay will help fill the gap between genotypic and phenotypic insecticide resistance in multiple insect species.

Topical Application Bioassay to Quantify Insecticide Toxicity for Mosquitoes and Fruit Flies.

The continued use of insecticides for public health and agriculture has led to widespread insecticide resistance and hampering of control methods. Insecticide resistance surveillance of mosquito populations is typically done through Centers for Disease Control and Prevention (CDC) bottle bioassays or World Health Organization (WHO) tube tests. However, these methods can result in a high degree of variability in mortality data due to variable insecticide contact withthe insect, the relatively small numbers of organisms tested, extensive variation in mass between populations, and constantly changing environmental conditions, leading to variable outcomes. This paper presents the topical application bioassay, adapted as a high-throughput phenotypic bioassay for both mosquitoes and fruit flies, to test large numbers of insects alonga range of insecticide concentrations. This assay 1) ensures consistent treatment and insecticide contact with every organism, 2) produces highly specific dose-response curves that account for differences in average mass between strains and sexes (which is particularly important for field-collected organisms), and 3) allows for the calculation of statistically rigorous median lethal doses (LD50), which are necessary for resistance ratio comparisons-an alternative surveillance approach from diagnostic dose mortality, which is also used for larvicide resistance surveillance. This assay will be a complementary tool for accurately phenotyping mosquito populations and, as illustrated using fruit flies, is easily adaptable for use with other insects. We argue that this assay will help fill the gap between genotypic and phenotypic insecticide resistance in multiple insect species.

Resistance status and the rate of resistance development in Musca domestica Linnaeus (Diptera: Muscidae) to permethrin and imidacloprid in Indonesia

A previous report has indicated that in many regions of Indonesia, populations of Musca domestica Linnaeus have shown very high resistance to permethrin and low resistance to imidacloprid. In this study, the resistance status to permethrin and imidacloprid was updated using a topical application and feeding bioassay. Six housefly strains originated from six highly populated cities in Indonesia, namely Serang (SRG), Jakarta (JKT), Bandung (BDG), Semarang (SMG), Yogyakarta (JOG), and Surabaya (SBY). A seventh strain (Danish Pest Infestation Laboratory (DPIL)) served as the control. Each strain was tested for resistance to the two insecticides. In addition, the rate of development of resistance to the two insecticides was measured over ten generations. The results indicated that all field strains showed very high resistance to permethrin. The highest resistance level recorded was in the SRG strain (RR50 = 2880), and the lowest was in the JKT strain (RR50 = 520). Repeated application of permethrin over ten generations increased the resistance level by about 2.7–32.73-fold as compared to the level of their respective parental populations. On the other hand, most strains showed low to moderate resistance to imidacloprid, in which the SRG strain had the highest resistance level (RR50 = 15.5) and the SBY strain had the lowest (RR50 = 2.0). Repeated application of imidacloprid over ten generations increased the resistance level by about 3.25–17.41-fold. The findings, which is the second report of housefly resistance in Indonesia since 2016, provide a crucial foundation for developing appropriate housefly integrated pest management strategies in highly populated areas in Indonesia.

Susceptibilidad de Diaphorina citri a dimetoato y clorpirifos en huertas citrícolas comerciales de Veracruz, México

There are reports of Diaphorina citri resistance in the state of Veracruz to chlorpyrifos and dimethoate due to the excessive use of these products for the control of pests, among them D. citri. The purpose of this work was to diagnose the susceptibility of D. citri adults to chlorpyrifos and dimethoate in commercial citrus orchards of the municipality of Martinez de la Torre, Veracruz. For this, 200 adults of D. citri were collected in each of 30 orchards, and topical application bioassays were performed with dimethoate at 0.0090% concentration and chlorpyrifos at 0.0085% concentration. Diaphorina citri adults without chemical control during 10 years were used as a control. Mortality of D. citri with dimethoate and chlorpyrifos averaged 85%, in contrast the control mortality was 99% and 98.8% with dimethoate and chlorpyrifos, respectively. According to these results, it can be inferred that D. citri has some resistance to organophosphate insecticides in the orchards of Martinez de la Torre, Veracruz. This information can be used to decide the type of insecticides to apply in the study area.

Insecticidal and oviposition deterrent effects of essential oils of Baccharis spp. and histological assessment against Drosophila suzukii (Diptera: Drosophilidae)

The diverse flora of the Atlantic Forest is fertile ground for discovering new chemical structures with insecticidal activity. The presence of species belonging to the genus Baccharis is of particular interest, as these species have shown promise in pest management applications. The objective of this study is to chemically identify the constituents expressed in the leaves of seven species of Baccharis (B. anomala DC., B. calvescens DC., B. mesoneura DC., B. milleflora DC., B. oblongifolia Pers., B. trimera (Less) DC. and B. uncinella DC.) and to evaluate the toxicological and morphological effects caused by essential oils (EOs) on the larvae and adults of Drosophila suzukii (Diptera: Drosophilidae). Chemical analysis using gas chromatography-mass spectrometry (GC–MS) indicated that limonene was the main common constituent in all Baccharis species. This constituent in isolation, as well as the EOs of B. calvescens, B. mesoneura, and B. oblongifolia, caused mortality in over 80% of adults of D. suzukii at a discriminatory concentration of 80 mg L−1 in bioassays of ingestion and topical application. These results are similar to the effect of spinosyn-based synthetic insecticides (spinetoram 75 mg L−1) 120 h after exposure. Limonene and EOs from all species had the lowest LC50 and LC90 values relative to spinosyn and azadirachtin (12 g L−1) in both bioassays. However, they showed the same time toxicity over time as spinetoram when applied to adults of D. suzukii (LT50 ranging from 4.6 to 8.7 h) in a topical application bioassay. In olfactometry tests, 92% of D. suzukii females showed repellent behavior when exposed to the EOs and limonene. Likewise, the EOs of B. calvescens, B. mesoneura, and B. oblongifolia significantly reduced the number of eggs in artificial fruits (≅ 7.6 eggs fruit−1), differing from the control treatment with water (17.2 eggs fruit−1) and acetone (17.6 eggs fruit−1). According to histological analyses, the L3 larvae of D. suzukii had morphological and physiological alterations and deformations after exposure to treatments containing EOs and limonene, which resulted in high larval, pupal, and adult mortality. In view of the results, Baccharis EOs and their isolated constituent, limonene, proved to be promising alternatives for developing bioinsecticides to manage of D. suzukii.

Insecticide resistance in California populations of the glassy-winged sharpshooter Homalodisca vitripennis.

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is a primary vector of Pierce's disease of grapes in California. Systemic imidacloprid treatments have been the mainstay of area-wide treatment programs that were established in the Central Valley (Kern and Tulare Counties) and Southern California (Riverside County) during the 1990s to combat the pest. The programs helped to suppress populations on citrus, a major sharpshooter host, to levels that significantly reduced migration into adjacent vineyards. However, beginning in 2012, there has been a resurgence of glassy-winged sharpshooter populations in Kern and Tulare counties, and hitherto successful treatment strategies have not been as effective. This study investigated the possibility that insecticide resistance was a contributing factor to the population resurgence. Topical application bioassays detected high levels of resistance to imidacloprid in Kern and Tulare populations, and lower levels of resistance (perhaps due to cross-resistance) to the foliar neonicotinoid acetamiprid (20-fold), the pyrethroid fenpropathrin (7.4-fold), and the butenolide flupyradifurone (4-fold). Samples of glassy-winged sharpshooters from citrus groves under organic management also exhibited high levels of imidacloprid resistance. The long-term use of imidacloprid has selected for resistance in glassy-winged sharpshooters. The most resistant populations also exhibited resistance to the foliar neonicotinoid acetamiprid, the pyrethroid fenpropathrin, and the butenolide flupyradifurone. High levels of imidacloprid resistance in insects sampled from organic groves indicate that resistant insects are migrating from nearby conventional groves, which could compromise the control of sharpshooters in organic systems with insecticides affected by cross-resistance. © 2021 Society of Chemical Industry.

Field Efficacies and Joint Actions of Beta-cyfluthrin Mixed With Thiamethoxam or Tolfenpyrad Against Diaphorina citri (Hemiptera: Liviidae).

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most serious pest of citrus because it is a vector for the highly destructive citrus greening disease (huanglongbing, HLB). Currently, insecticide applications are being used widely to control psyllid populations, thereby suppressing the spread of HLB. In the present study, topical application bioassays were performed to detect the joint actions of beta-cyfluthrin and thiamethoxam or tolfenpyrad against D. citri adults in the laboratory. In 2019, a field plot experiment was conducted to evaluate the control efficacies of beta-cyfluthrin+thiamethoxam 22% capsule suspension and beta-cyfluthrin+tolfenpyrad 30% microemulsion against D. citri using foliar sprays. For the former, a 9:13 mass ratio had the highest synergistic effect, with a cotoxicity coefficient of 188.64. For the latter, a 5:25 mass ratio had the highest synergistic effect, with a cotoxicity coefficient of 153.94. A one-time foliar spray of the former at 30-40 mg/kg or of the latter at 40-60 mg/kg effectively controlled D. citri, with control efficacies varying from 80.1 to 99.4% or 80.4 to 100.0%, during the 3-30 d after treatment, respectively. Moreover, field observations indicated that these foliar sprays at the tested rates had no negative effects on citrus trees. Thus, foliar sprays of beta-cyfluthrin+thiamethoxam or beta-cyfluthrin+tolfenpyrad under the given conditions may control D. citri.

Toxicity of Phenylpropanoids from Alpinia galanga (Zingiberaceae) extracts against Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

Spodoptera exigua Hubner is one of the most important agricultural pests in Thailand. The present study investigated the toxicity of crude extracts and phenylpropanoid compounds of A. galanga (Zingiberaceae) against S. exigua. After 24 h of a topical application bioassay on secondary instar larvae, the ethyl acetate extract estimation of the LD50 of A. galanga (Zingiberaceae) showed toxicity toward secondary instar S. exigua larvae (LD50 ~ 2.44 µg/larva). Phenylpropanoid compounds were isolated from the ethyl acetate A. galanga crude extract which has [1’S]-1’-acetoxychavicol acetate as highest toxicity (LD50 of 1.93 µg/larvae). [1’S]-1’-acetoxychavicol acetate also showed carboxylesterase activity inhibition. Thus, the ethyl acetate extract of A. galanga may have [1’S]-1’-acetoxychavicol acetate as an active ingredient for controlling this pest, which could be used as an alternative to application of environmentally insecticides for controlling S. exigua.

Lethal and sublethal toxicities of acetogenin-based bioinsecticides on Ceratitis capitata and the parasitoid Diachasmimorpha longicaudata

In this study, was evaluated the action lethal and sublethal of three formulations of Annona species extracts (A. mucosa, A. muricata and A. sylvatica) on adults of Ceratitis capitata (Wiedemann, 1852) (Diptera: Tephritidae) and yours parasitoid Diachasmimorpha longicaudata (Ashmead, 1905) (Hymenoptera: Braconidae). In addition, the efficacy of the selected toxic bait formulations was evaluated by mixing them with different food attractants (Anamed™, 3% Biofruit and 7% sugarcane molasses). From the use of the discriminatory concentration (2000 mg L-1), only A. mucosa caused mortality of C. capitata of more than 85% in ingestion and topical application bioassays, equivalent a spinosyn-based insecticide (control positive). In toxic bait formulation with the tested food attractants, the extracts had a residual effect (mortality ≥80% C. capitata) up to 14 days after applying treatments (DAAT) in the absence of rain. Based on the LC90 (1984.20 mg L−1) values estimated from the concentration-response curves for C. capitata, A. mucosa caused less than 40% adult mortality of the parasitoid D. longicaudata in the ingestion bioassay. However, both treatments showed no sublethal effects (parasitism reduction) over time. In addition, in bioassays with and without choice, there was a significant reduction in the number of punctures and galls caused by females and larvae of C. capitata, respectively, in grape berries in the presence of dry residues of all evaluated treatments. The A. mucosa seed extract was considered the most promising product for use in C. capitata management programs, particularly in organic-based systems, due to its selectivity to D. longicaudata.

Insecticide susceptibility of Culex pipiens pallens (L.) and Aedes albopictus (Skuke) to five commonly used pesticides in the Republic of Korea

AbstractField collected populations of two mosquito species, Culex pipiens pallens and Aedes albopictus, were tested for susceptibility to five pyrethroid insecticides using a topical application bioassay. The laboratory strain of Cx. pipiens pallens (KS‐CP) demonstrated the most and the lowest susceptibility to deltamethrin and d‐cis/trans prallethrine with LD50 values of 0.00022 μg/♀ and 0.00178 μg/♀, respectively, while Ae. albopictus (KS‐AL) showed the greatest and the lowest susceptibility to phthalethrin and deltamethrin with LD50 values of 0.00015 μg/♀ and 0.00085 μg/♀, respectively. Cx. pipiens pallens (JF‐CP) collected at a nearby rice field in Jeonju showed the greatest susceptibility to deltamethrin (LD50 value of 0.0473 μg/♀) and the resistance ratios (RRs) and compared to the laboratory strain were 215 fold greater. JF‐CP demonstrated the lowest susceptibility to d‐cis/trans phenothrin (0.7697 μg/♀) with RRs 711.0 fold greater than the KS‐CP. An Ae. albopictus (JF‐AL) collected at a nearby forest in Jeonju showed the highest susceptibility to deltamethrin (0.00203 μg/♀) with RRs 2.4 fold greater than the KS‐AL. JF‐AL demonstrated the lowest susceptibility to d‐cis/trans prallethrine (LD50 value 0.00646 μg/♀) with RRs 9.4 fold greater than the KS‐AL. JF‐AL demonstrated the greatest resistance to phthalethrin with RRs 39.3 fold greater than the KS‐AL. Resistance ratios of Cx. pipiens pallens between field and laboratory strains ranged from 215.0 to 711.0 and Ae. albopictus ranged from 2.4 to 39.3. These results indicate that the choice of effective insecticides to selected species of mosquito populations will result in more effective control against field strains of mosquito vectors and decrease environmental pollution.

Toxicities of Insecticidal Toxic Baits to Control Ceratitis capitata (Diptera: Tephritidae): Implications for Field Management.

Ceratitis capitata (Wiedemann, 1824) is a significant insect pest of fruits produced worldwide and is capable of causing direct and indirect damage to fruit. Chemical control is the most frequently used management strategy, mainly involving organophosphate insecticides. However, the frequent use of this chemical group has resulted in unacceptable chemical residues on fruits. In this study, the toxicity of 18 insecticides was evaluated in adults and larvae of C. capitata in a laboratory. The organophosphate insecticides chlorpyrifos (Lorsban 480BR), phosmet (Imidan 500WP), and malathion (Malathion 1000EC); the spinosyns spinetoram (Delegate 250WG) and spinosad (Tracer); and the pyrethroid alpha-cypermethrin (Fastac 100SC) caused high mortality (>80%) in C. capitata adults in topical application bioassays and by ingestion when mixed with Biofruit 5% food lures. However, the insecticides chlorfenapyr (Pirate), spinetoram and chlorpyrifos produced a significant reduction in larval infestation of the fruits (67, 74, and 84% larval mortality, respectively). Insecticides based on spinosyns, alpha-cypermethrin, and cyantraniliprole are alternatives that can replace organophosphates in the management of C. capitata in the field.

Seven-year monitoring of pyrethroid resistance in the pollen beetle (Brassicogethes aeneus F.) during implementation of insect resistance management.

An increase in the spread of pyrethroid resistance in the pollen beetle has been documented in many European countries. Pyrethroid resistance in the pollen beetle in the Czech Republic has been detected using a topical application bioassay. Resistance monitoring has been carried out during the implementation of insect resistance management. The susceptibilities of nine pollen beetle populations to four pyrethroids in 2009 - 2015 in the Czech Republic are presented in this paper. The highest resistance ratio (RR) values [based on the lethal dose for 50% of the population (LD50 )] obtained for deltamethrin, lambda-cyhalothrin, tau-fluvalinate and etofenprox were 500, 299, 108 and 66.9, respectively. Pollen beetle mortality after application of deltamethrin or lambda-cyhalothrin gradually decreased from 2009 to 2013. High cross-resistance between lambda-cyhalothrin and deltamethrin and low cross-resistance between lambda-cyhalothrin and etofenprox were demonstrated. A kdr mutation known to cause resistance in the pollen beetle was not detected. A high level of resistance was recorded in most of the nine populations of the pollen beetle in 2013. In the following 2 years, a decrease in resistance associated with a population density decrease of the pollen beetle was observed in all nine populations as a result of insect resistance management based on pyrethroid reduction in winter oilseed rape. © 2017 Society of Chemical Industry.

Effect of synthetic insecticides on the larvae of Coccinella septempunctata from Greek populations

Coccinella septempunctata L. is one of the most abundant ladybird species in Greece, preying on several aphid species and other arthropods, of which many are pests of cultivated plants. These pests are usually controlled with chemical insecticides. During this process, however, beneficials are also exposed to pesticides. The development of Integrated Pest Management (IPM) programs against aphids requires the evaluation of the effects of insecticides on beneficial insects. We evaluated the LD50 of imidacloprid, acetamiprid, bifenthrin and deltamethrin on first, second, third and fourth instar larvae of C. septempunctata by topical application. Moreover, we studied their sublethal effects (LD10) on the development, weight and prey consumption of fourth instar larvae. The topical application bioassays showed that deltamethrin and bifenthrin were highly toxic to all larval instars, whereas imidacloprid and acetamiprid were less toxic to fourth instar larvae. The LD10 dose significantly affected, developmental time, adult weight and daily predation. These results show the importance of assessing potential effect of insecticides on C. septempunctata for developing effective IPM programs of aphids in Greece.

Impact of Topical Application Site On the Efficacy of Permethrin and Malathion To Culex quinquefasciatus.

Although insecticide spray droplets will potentially impinge on many exoskeletal body regions, traditional mosquito topical bioassays focus insecticide application to the mesothoracic pleural or dorsal area. Concentrations of permethrin and malathion found in droplets from ultra-low volume and low-volume sprays were evaluated for efficacy against adult Culex quinquefasciatus using a topical application bioassay. Results document nonuniform insecticide sensitivity across body regions, which has not been previously assessed in mosquitoes. Insecticide contact with appendages, such as the leg and the wing, returned much lower mortality from both insecticides than exposure to the primary body (i.e., head, thorax, and abdomen). No difference was observed in percent mortality 24 h after exposure to different insecticides to the same body region. Sublethal behaviors were also observed and discussed for both insecticides. Our findings provide valuable information for those performing topical bioassays, and may help explain insecticide effectiveness wherever droplets impinge upon the mosquito body during laboratory or field applications.