Partial compensation of the sublethal effect of deltamethrin on the sex pheromonal communication of Trichogramma brassicae

Pyrethroid insecticides are widely used and lead to a sizable environmental pollution that could interfere with the population biology of insects. Trichogramma is a beneficial insect used in biological control and which natural populations contribute to the control of Lepidopterus pests. In this work, we determined the effect of a sublethal dose of deltamethrin on the sex pheromonal communication of Trichogramma. The dose used (LD 0.1) induces no detectable mortality (the theoretical mortality is only one insect over 1000) and can be a good representation of contamination by this insecticide from environmental pollution. The insecticide was shown to have opposite effects on the sex pheromonal communication of Trichogramma, depending on which sex was exposed (Delpuech, J.M., Legallet, B., Terrier, O., Fouillet, P., 1999. Chemosphere 38, 729–739). We show that, when both sexes are simultaneously exposed to the insecticide, this effect is only partially neutralized. The mean response of treated males responding to the sex pheromone from treated females is not significantly different from that of controls, but the kinetics of their response is not the same. When both sexes are treated, the response of males to the sex pheromone is lower at the beginning but their response does not decrease during time contrary to controls and becomes finally higher than that of controls. Therefore, the sublethal effect of deltamethrin in the field can be either advantageous or disadvantageous depending on the difficulty in finding females and their scarcity.     

Partial compensation of the sublethal effect of deltamethrin on the sex pheromonal communication of Trichogramma brassicae

Pyrethroid insecticides are widely used and lead to a sizable environmental pollution that could interfere with the population biology of insects. Trichogramma is a beneficial insect used in biological control and which natural populations contribute to the control of Lepidopterus pests. In this work, we determined the effect of a sublethal dose of deltamethrin on the sex pheromonal communication of Trichogramma. The dose used (LD 0.1) induces no detectable mortality (the theoretical mortality is only one insect over 1000) and can be a good representation of contamination by this insecticide from environmental pollution. The insecticide was shown to have opposite effects on the sex pheromonal communication of Trichogramma, depending on which sex was exposed (Delpuech, J.M., Legallet, B., Terrier, O., Fouillet, P., 1999. Chemosphere 38, 729–739). We show that, when both sexes are simultaneously exposed to the insecticide, this effect is only partially neutralized. The mean response of treated males responding to the sex pheromone from treated females is not significantly different from that of controls, but the kinetics of their response is not the same. When both sexes are treated, the response of males to the sex pheromone is lower at the beginning but their response does not decrease during time contrary to controls and becomes finally higher than that of controls. Therefore, the sublethal effect of deltamethrin in the field can be either advantageous or disadvantageous depending on the difficulty in finding females and their scarcity.     

Unexpected effects of sublethal doses of insecticide on the peripheral olfactory response and sexual behavior in a pest insect

Pesticides have long been used as the main solution to limit agricultural pests, but their widespread use resulted in chronic or diffuse environmental pollutions, development of insect resistances, and biodiversity reduction. The effects of low residual doses of these chemical products on organisms that affect both targeted species (crop pests) but also beneficial insects became a major concern, particularly because low doses of pesticides can induce unexpected positive—also called hormetic—effects on insects, leading to surges in pest population growth at greater rate than what would have been observed without pesticide application. The present study aimed to examine the effects of sublethal doses of deltamethrin, one of the most used synthetic pyrethroids, known to present a residual activity and persistence in the environment, on the peripheral olfactory system and sexual behavior of a major pest insect, the cotton leafworm Spodoptera littoralis. We highlighted here a hormetic effect of sublethal dose of deltamethrin on the male responses to sex pheromone, without any modification of their response to host-plant odorants. We also identified several antennal actors potentially involved in this hormetic effect and in the antennal detoxification or antennal stress response of/to deltamethrin exposure.     

Promising new technology for managing diamondback moth (Lepidoptera: Plutellidae) in cabbage with pheromone

Experiments were conducted in plantings of cabbage in spring 1999 and 2000 to evaluate a novel, new matrix system for delivering sex pheromone to suppress sexual communication by diamondback moth, Plutella xylostella (L.). The liquid, viscous, slow-release formulation contained a combination of diamondback moth pheromone, a blend of Z-11-hexadecenyl acetate, 27%:Z-11-hexadecen-1-ol, 1%:Z-11-tetradecen-1-ol, 9%:Z-11-hexadecenal, 63%, and the insecticide permethrin (0.16% and 6% w/w of total formulated material, respectively). Field trapping experiments showed that the lure-toxicant combination was highly attractive to male moths for at least four weeks using as little as a 0.05 g droplet of formulated material per trap; and the permethrin insecticide had no apparent influence on response of moths to lure baited traps. Small field plots of cabbage were treated with the lure-toxicant-matrix combination using droplets of 0.44 and 0.05 g each applied to cabbage in a grid pattern at densities ranging from 990 to 4396 droplets/ha to evaluate the potential for disrupting sexual communication of diamondback moth. There was no significant difference in the level of suppression of sexual communication of diamondback moth, as measured by captures of males in pheromone-baited traps located in the treated plots, versus moths captured in untreated control plots, among the treatments regardless of droplet size (0.05 or 0.44 g) or number of droplets applied per ha. Plots treated with the smallest droplet size (0.05 g) and with the fewest number of droplets per ha (990) suppressed captures of male diamondback moths > 90% for up to 3 weeks post treatment. Although laboratory assays showed that the lure-toxicant combination was 100% effective at killing the diamondback moth, the mode of action in the field trials was not determined. The results indicate that the liquid, viscous, slow release formulation containing diamondback moth pheromone could be used to effectively suppress sexual communication of this pest in cabbage and other crucifers, although as many as three applications probably would be required for suppression over an entire growing season.     

Evaluation of the effect on arthropod populations by using deltamethrin to control Phloeotribus scarabaeoides Bern. (Coleoptera: Scolytidae) in olive orchards

Field tests were made for the control of an olive insect pest, the olive bark beetle, Phloeotribus scarabaeoides (Col: Scolytidae), using the pyrethroid insecticide deltamethrin (D) and this insecticide combined with ethylene (D+E), an attractant of the olive bark beetle. The tests were run in olive orchards in the provinces of Granada and Jaén (Andalusia, southern Spain), treating several olive rows so as to create a barrier effect to control the pest attack. The main objective was to evaluate the arthropod fauna affected by these treatments. The different taxa captured have been separated in three different trophic groups: parasitoids, predators and phytophagous. A knock-down effect was found during the first dates in all the functional groups in all cases. The results showed the following trend in arthropod abundance: D+E>D>C. This trend was significant (p<0.05) for predators and phytophagous insects in both zones. The parasitoids of Prays oleae (Lep.: Plutellidae), a major olive pest, were most affected by the treatments, together with several groups of predators such as ants, cantharids, coccinellids and mirids. Data from the captures show the need to determine the optimum time for insecticide application in order to minimise its effect on beneficial insect populations.     

Polychlorinated biphenyls and organochlorine pesticides in Baltic Sea sediments and bivalves

Insecticide resistance is an evolutionary response to insecticides and, as such, important for environmental biomonitoring and for pest management. Fitness disadvantage in the absence of insecticide is a frequent assumption in models of insecticide resistance evolution, which was observed in different insect species. Fitness studies are based in demographic performance of isolated populations without direct interaction between insecticide-resistant and -susceptible populations. Here we reported a study of direct competition following a factorial bivariate design between an insecticide-susceptible population of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), and one of two insecticide-resistant populations - one exhibiting fitness disadvantage based on demographic studies (Juiz de Fora) and other not exhibiting it (Jacarezinho). Total number of insects, mortality by insecticide, insect body mass and respiration rate were recorded after three generations of competition. Indeed, fitness disadvantage was observed in the resistant population from Juiz de Fora, but not in the population from Jacarezinho, as expected. The higher body mass and respiration rate of the insecticide-resistant insects from Jacarezinho are probably mitigating the physiological costs associated with the insecticide resistance minimizing their fitness disadvantage, what does not take place with the insecticide-resistant insects from Juiz de Fora. These distinct responses between the insecticide-resistant populations are probably related to the length and intensity of field-selection with insecticides.     

Spodoptera exigua: mating disruption, measurement of airborne concentration of pheromone, and use of specialist receptor cell responses for comparison to female pheromone emission

Field experiments were conducted to evaluate Shin-Etsu Yoto-con-S 'rope' pheromone dispensers applied at different site densities in cotton to determine efficacy in disrupting sexual communication and mating of beet armyworm moths, Spodoptera exigua (Hübner); obtain atmospheric measurements of the disruptant pheromone components in and away from treated areas; and relate this information to estimates of the concentration of pheromone in the near vicinity of a calling virgin female moth. The number of pheromone-dispensing sites/ha ranged from 25 with 20 ropes/site up to a total of 247 sites with 2 ropes each. A total of 112 g pheromone of a 70:30 blend of (Z,E)-9,12-tetradecadien-l- ol acetate (ZETA) and (Z)-tetradecen-1-ol (Z9-14:OH) was applied/ha. As few as 25 sites/ha effectively disrupted sexual communication by 91%, as measured by reductions of moth captures in traps baited with pheromone lures, and mating by beet armyworm females by 94% for at least 10 weeks post-treatment. The results compared favorably to an earlier large-scale field experiment in which beet armyworm larval populations were reduced 95% using 500 pheromone-dispensing sites/ha (two ropes/site) and 160 g total pheromone/ha. The airborne concentration of ZETA and Z9-14:OH measured within the pheromone-treated plots that disrupted mating was 1.5 x 10(-13) M and 1.2 x 10(-13) M, respectively. The airborne concentration of ZETA and Z9-14:OH in the vicinity of a female was estimated (by excision and electrophysiological methods) to range between 2.1 x 10(-11) M and 2.4 x 10(-12) M, respectively, in a 1.6 km/h (1 mph) wind speed. Thus, the average ZETA concentration in the treated plots was about 140 times less than that expected from a single female; the average Z9-14:OH in the treated plots was about 20 times less. The data support an argument that disruption of mating by beet armyworm resulted from an imbalance in sensory input because mating was almost completely disrupted in all of the plots for at least 10 weeks with a mixture of ZETA:Z9-14:OH that differed significantly with that from excised female sex pheromone glands. Estimates of these parameters provide a benchmark for the requisite pheromone concentration in the atmosphere to achieve a high level of mating disruption for beet armyworm and possibly other insect pest species.     

Herbicide toxicity,selectivity and hormesis of nicosulfuron on 10 Trichogrammatidae (Hymenoptera) species parasitizing Anagasta ( = Ephestia) kuehniella (Lepidoptera: Pyralidae) eggs

Selective agrochemicals including herbicides that do not affect non-target organisms such as natural enemies are important in the integrated pest management (IPM) programs. The aim of this study was to evaluate the herbicide toxicity, selectivity and hormesis of nicosulfuron, recommended for the corn Zea mays L. (Poaceae) crop, on 10 Trichogrammatidae (Hymenoptera) species. A female of each Trichogramma spp. or Trichogrammatoidea annulata De Santis, 1972 was individually placed in plastic test tubes (no choice) with a cardboard containing 45 flour moth Anagasta ( = Ephestia) kuehniella Zeller, 1879 (Lepidoptera: Pyralidae) eggs. Parasitism by these natural enemies was allowed for 48 h and the cardboards were sprayed with the herbicide nicosulfuron at 1.50 L.ha^?1, along with the control (only distilled water). Nicosulfuron reduced the emergence rate of Trichogramma bruni Nagaraja, 1983 females, but increased that of Trichogramma pretiosum Riley, 1879, Trichogramma acacioi Brun, Moraes and Smith, 1984 and T. annulata females. Conversely, this herbicide increased the emergence rate of Trichogramma brasiliensis Ashmead, 1904, T. bruni, Trichogramma galloi Zucchi, 1988 and Trichogramma soaresi Nagaraja, 1983 males and decreased those of T. acacioi, Trichogramma atopovilia Oatman and Platner, 1983 and T. pretiosum males. In addition, nicosulfuron reduced the sex ratio of T. galloi, Trichogramma bennetti Nagaraja and Nagarkatti, 1973 and T. pretiosum and increased that of T. acacioi, T. bruni, T. annulata, Trichogramma demoraesi Nagaraja, 1983, T. soaresi and T. brasiliensis. The herbicide nicosulfuron was “harmless” (class 1, <30% reduction) for females and the sex ratio of all Trichogrammatidae species based on the International Organization for Biological Control (IOBC) classification. The possible hormesis effect of nicosulfuron on Trichogrammatidae species and on the bacterium Wolbachia sp. (Rickettsiales: Rickettsiaceae) was also discussed.     

Occurrence of spruce bark beetles in forest stands at different levels of air pollution stress

The spruce bark beetle, Ips typographus (L.) is the most serious pest of mature spruce stands, mainly Norway spruce, Picea abies (L.) Karst. throughout Eurasia. A complex of weather-related events and other environmental stresses are reported to predispose spruce stands to bark beetle attack and subsequent tree mortality; however the possible role of industrial pollution as a predisposing factor to attack by this species is poorly understood. The abundance and dynamics of I. typographus populations was evaluated in 60-80 year old Norway spruce stands occurring on 10 x 50 ha sites in five countries within the Carpathian range that were selected in proximity to established ozone measurement sites. Data were recorded on several parameters including the volume of infested trees, captures of adult beetles in pheromone traps, number of attacks, and the presence and relative abundance of associated bark beetle species. In several cases, stands adjacent to sites with higher ozone values were associated with higher bark beetle populations. The volume of sanitary cuttings, a reflection of tree mortality, and the mean daily capture of beetles in pheromone traps were significantly higher at sites where the O(3) level was higher. However, the mean infestation density on trees was higher in plots associated with lower O(3) levels. Captures of beetles in pheromone traps and infestation densities were higher in the zone above 800 m. However, none of the relationships was conclusive, suggesting that spruce bark beetle dynamics are driven by a complex interaction of biotic and abiotic factors and not by a single parameter such as air pollution.     

In vitro metabolism of deltamethrin by stem and leaf homogenates of tobacco plants

Stem and leaf homogenates from tobacco plants metabolised deltamethrin by oxidative and hydrolytic actions on the insecticide. Although a major portion of deltamethrin remained unchanged, metabolites such as 3-phenoxybenzaldehyde, 3-phenoxybenzoic acid and 3-(2,2-dibromonyl)-2,2-dimethylcyclopropanecarboxylic acid were formed. The data suggest a major portion of the insecticide would remain unchanged when absorbed by tobacco plants.     

A multi-step bioassay to assess the effect of the deltamethrin on the parasitic wasp Aphidius ervi

Insecticides are widely used for crop protection. Effectiveness of pesticides and beneficial arthropods in an Integrated Pest Management (IPM) program requires a full understanding of how specific pesticides alter natural enemy effectiveness. This may require evaluation of chemicals at different life stages of the insect considered, on different physiological and behavioural components, and also on population dynamic components such as recolonization capacities after a pesticide treatment. Aphidius ervi Haliday (Hymenoptera: Braconidae) is an aphid parasitoid commonly used for the biological control of aphid populations. In this work, our aim was to assess the effects of deltamethrin (pyrethroid) treatments on this parasitoid using a multi-step bioassay. We evaluated its effects on parasitoid emergence, adult survival and longevity, and host searching. Two exposure methods were used, topical and spray, to evaluate impact of the deltamethrin field rate (6.25ga.i./ha) and also to compare the methods of exposure. A four-armed olfactometer was used to investigate effect of deltamethrin on host searching behaviour. When applied at the rate of field exposure, deltamethrin reduced the adult longevity but not the rate of emergence from mummies. Effects varied between the two exposure methods. Two indices were defined: the "population survival index" to measure capacity of parasitoids to recolonize a treated field and the "reproductive potential" to estimate the reduction in reproduction as a function of longevity decrease. These indices predicted effects of deltamethrin on A. ervi in terms of mortality and reduction of recolonization capacities. However, adults that survived residual exposure to deltamethrin retained their ability to orient to host odours. The implications of results in IPM and interest of the methodology used are both discussed.     

What do sentinels stand for?

Sentinel species are biological monitors that accumulate a pollutant in their tissues without significant adverse effects. Primarily used to measure the amount of a pollutant that is biologically available, they may also increase the sensitivity of an analytical procedure or summarise a complex pollution signal. This paper examines the validation of sentinels, referring particularly to the use of invertebrates in monitoring toxic metal pollution in terrestrial ecosystems. Few studies measure the capacity of a sentinel to quantify changes in ambient levels. Definitions of 'bioavailability' also differ between workers and few note that this may be a highly species-specific measure. Validation requires that the temporal and spatial scales over which a sentinel integrates a pollution signal are known. The sentinel has to be calibrated against source concentrations and this relationship shown to be consistent over the normal range of exposure. This requires some consideration of the environmental and biological determinants of pollutant assimilation. Differences between populations can confound simple comparisons between sites based on native populations. Transplanted individuals, matched for age, sex and physiological state, might be used when the aim is not to assess bioavailability to the resident population. A simple measure of their capacity to detect differences in ambient pollutant levels is proposed to evaluate candidate species, to assess their consistency and capacity to equilibrate with their source. A small survey of earthworms from a well-defined gradient of Pb pollution is used to illustrate problems of interpreting tissue concentrations in sentinels.     

Typology of susceptibilities of aquatic insect larvae to different larvicides in a tropical environment

Multi-gutter tests are used by the Onchocerciasis Control Programme in West Africa to screen antiblackfly larvicides with reference to non-target aquatic insect larvae. Because the tests are not always conducted under the same environmental conditions, direct comparison of results by the usual methods of data analysis presents some difficulties. The application of reciprocal averaging (correspondence analysis) to data from tests carried out using the same protocol indicates that the test periods have no incidence on the impact in gutter of the larvicides. The analysis also makes it possible to classify the insecticide families according to their degree of general toxicity on fauna. In addition there is no evidence of a uniform effect produced by each insecticide family on the principal taxa.     

Efficacy of new mass-trapping devices against Bactrocera oleae (Diptera tephritidae) for minimizing pesticide input in agroecosystems

Decreasing pesticide use in olive groves is central to controlling pathogens and pests such as Bactrocera oleae. This has led to the development of mass trapping devices which not only minimize pesticide use but, with improved efficacy of attractants, also decrease costs associated with pest control and ensures that the quality of olive oil is safe for human consumption. This study was undertaken to test a new device which utilizes reduced quantities of both insecticide (lambda-cyalothrin) as well as the female olive fly pheromone (1,7-dioxaspiro-(5.5)-undecane). The new device was tested against an older device manufactured by the same company. The use of plastic polymers as substrate for encapsulating the pheromone allowed for a slower pheromone release, prolonging the efficacy and duration and thus reducing costs. The density of adult populations was monitored using yellow chromotropic traps that were checked every ten days and the degree of olive infestation, as determined by preimago stages, was assessed by analyzing 100 drupes per plot. Infestation analyses were performed every ten days. The control plot had the lowest density of adults and the highest drupe infestation rate. The new devices were more effective than the older devices in both attracting adults and controlling infestation of drupes. Moreover, the new devices containing reduced amounts of pheromone and insecticide were cheaper and exhibited longer functional efficacy. In addition to the slower release of attractants, the plastic polymers used in these newer devices were also more resistant to mechanical and weather degradations. Results demonstrate that mass trapping can indeed be an effective means of controlling B. oleae via eco-sustainable olive farming.     

Deltamethrin residues in milk and tissues of lactating dairy cows.

Lactating dairy cows were fed deltamethrin (2 or 10 mg kg-1 feed) for 28 consecutive days and deltamethrin residues measured in milk and tissues. Deltamethrin residues were higher relative to dose administered. The order of relative concentrations of deltamethrin in tissues, measured 1, 4, and 9 days after the last dose was: renal fat greater than subcutaneous fat greater than forequarter muscle greater than hindquarter muscle greater than liver greater than kidney. Depletion of deltamethrin residues in milk was very rapid indicating the half-life of the insectide of about 1 day. Trace amounts of deltamethrin metabolites 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (less than 0.0235 ppm) and 3-phenoxybenzoic acid (less than 0.034 ppm) were also detected in milk and tissues of treated cows.     

Effects of the insect growth regulator (S)-methoprene on survival and reproduction of the freshwater cladoceran Moina macrocopa

This study examines the acute and chronic effects of the insecticide (S)-methoprene on the survival and reproduction of the freshwater cladoceran Moina macrocopa. In laboratory toxicity tests, the 24- and 48-h LC50 values for (S)-methoprene were 0.51 and 0.34 mg litre(-1), respectively. Survival, longevity and fecundity were reduced at 0.05 mg litre(-1) and higher concentrations. At 0.005 and 0.01 mg litre(-1), longevity and fecundity increased slightly as compared to control animals. If environmental concentrations of methoprene do not exceed 0.05 mg litre(-1), as is generally the case, application of this insecticide is unlikely to induce detrimental effects on natural cladoceran populations. The stimulatory effect of very low levels of methoprene on reproductive performance is consistent with the hypothesis of a regulatory role of juvenile hormone-like compounds in crustacean reproduction.     

Effects of herbicide and insecticide interaction on soil entomofauna under maize crop

The aim of this study was to evaluate the impact of the herbicide mixture nicosulfuron + atrazine, with or without the insecticide chlorpyrifos, onto soil entomofauna under maize crop. The treatments, applied 25 days after maize emergence, were represented by a weeded control without insecticide and herbicide, a weeded control with chlorpyrifos, and mixtures of nicosulfuron + atrazine, with or without chlorpyrifos. Arthropods populations, on the soil surface, as well as inside the soil under maize, were principally represented by mites (Arachnida: Acari), decomposer collembolans (Hexapoda:Parainsecta:Collembola) and predator ants (Hymenoptera:Formicidae). The nicosulfuron + atrazine mixture with chlorpyrifos and the isolated chlorpyrifos reduced the population dynamics of all insect groups on the soil surface compared to the weeded control. In the soil, mite and ant populations were reduced after application of the herbicide mixture with chlorpyrifos and of the isolated chlorpyrifos.     

Effect of binary combination of deltamethrin+MGK-264 on the levels of phospholipid and lipid peroxidation in the snail Lymnaea acuminata

Effect of sublethal treatment of (40% and 60% of 48 h LC50) of deltamethrin+MGK on phospholipid level and rate of lipid peroxidation in nervous and foot tissue of Lymnaea acuminata were studied. Maximum reduction in phospholipid (24.10%) level and increase in rate of lipid peroxidation (586.8%) were observed in foot tissue of snail exposed to 60% of 48 h LC50 of deltamethrin+MGK 264 for 96 h. Alterations in the levels of phospholipids and rate of lipid peroxidation were time and concentration dependent. Use of MGK-264 with deltamethrin increases the toxicity of deltamethrin and their action on membrane phospholipids and rate of lipid peroxidation.     

Synergistic effect of Eugenia jambolana Linn. and Solidago canadensis Linn. leaf extracts with deltamethrin against the dengue vector Aedes aegypti Linn. at Mysore

With the goal in mind to minimize the application of environmentally hazardous chemical insecticides, the larvicidal activity of two plant extracts along with deltamethrin was studied at University of Mysore. The extracts of Solidago canadensis and Eugenia jambolana were employed for working out the synergistic efficacy against Aedes aegypti larvae, as the extracts of both the plants exhibited high efficacy when applied individually. The deltamethrin when analyzed separately, LC₅₀ and LC₉₀ values were 0.00045 and 0.00148 ppm, respectively. Synergistic studies with two plant extracts on deltamethrin revealed S. canadensis as more effective with synergistic factor(SF) of 4.090 for LC₅₀ value and 4.781 for LC₉₀ followed by E. jambolana with SF 1.80 for LC₅₀ and 2.467 for LC₉₀ at 1:1 ratio of the phytoextracts and deltamethrin. Thus, S. canadensis was found to be a better larvicidal and synergistic agent. Combination of phytochemical and insecticide were found to be more effective than insecticides or phytochemicals alone which could be a good ecofriendly and cost-effective approach to reduce the dose of chemicals with high residual effect to be applied in vector control programs.