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.     

Modifications of the sex pheromonal communication of trichogramma brassicae by a sublethal dose of deltamethrin

Pyrethroid insecticides, by their intensive use and their persistence that can exceed 3 months, largely contribute to the environmental pollution. In this work, we determined the effects of a very low dose of deltamethrin on the sex pheromonal communication of Trichogramma brassicae. The dose used was a dose that would theoretically kill one insect over 1000 (an LD 0.1). We found that this dose slightly but very significantly increased the arrestment behavior of treated males responding to the female pheromone. On the other hand when females were exposed to the same dose of insecticide, the response of males to their pheromone was very significantly decreased. In Trichogramma, like in other insects, sex pheromonal communication probably involves nervous transmissions both for the reception and the emission of the pheromone. Then, the sublethal effects of deltamethrin, observed in this work, are certainly due to multiple actions of this insecticide on nervous transmissions. Trichogramma is a beneficial insect that contributes to the control of pest populations of moths. Actions of this insecticide at a dose that can correspond to environmental pollution could be a real threat to the equilibrium of these populations.     

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.     

Survival and behavior of the insecticide-exposed predators Podisus nigrispinus and Supputius cincticeps (Heteroptera: Pentatomidae)

Pentatomid stinkbugs are important predators of defoliating caterpillars in agricultural and forestry systems, and knowledge of the impact of insecticides on natural enemies is important information for integrated pest management (IPM) programs. Thus, we assessed the toxicity and behavioral sublethal response of the predators Podisus nigrispinus and Supputius cincticeps exposed to deltamethrin, methamidophos, spinosad and chlorantraniliprole, insecticides commonly used to control the velvetbean caterpillar (Anticarsia gemmatalis) in soybean crops. With the exception of deltamethrin for S. cincticeps, all insecticides showed higher acute toxicity to the prey than to these natural enemies providing effective control of A. gemmatalis. The recommended field concentration of deltamethrin, methamidophos and spinosad for controlling A. gemmatalis caused 100% mortality of P. nigrispinus and S. cincticeps nymphs. Chlorantraniliprole was the less toxic and the most selective insecticide to these predators resulting in mortalities of less than 10% when exposed to 10× the recommended field concentration for a period of 72 h. Behavioral pattern changes in predators were found for all insecticides, especially methamidophos and spinosad, which exhibited irritability (i.e., avoidance after contact) to both predator species. However, insecticide repellence (i.e., avoidance without contact) was not observed in any of the insects tested. The lethal and sublethal effects of pesticides on natural enemies is of great importance for IPM, and our results indicate that substitution of pyrethroid and organophosphate insecticides at their field rates by chlorantraniliprole may be a key factor for the success of IPM programs of A. gemmatalis in soybeans.     

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.     

In situ assays with tropical cladocerans to evaluate edge-of-field pesticide runoff toxicity

Tropical regions’ economy is usually based on agriculture, which involves an intensive use, and even frequent overuse, of pesticides. Nevertheless, not much research has been done on the impact of pesticides on tropical aquatic ecosystems, which are often contaminated by runoff-related pesticide inputs due to unpredictable and torrential rainfalls. This study aimed to: (i) adapt and evaluate a short-term sublethal in situ assay using post-exposure feeding as an endpoint, to the tropical cladoceran species Diaphanosoma brachyurum (collected at the Pedra do Cavalo dam in the Paraguaçu River basin, Bahia, Brazil), and, (ii) assess the role of the standard species Daphnia magna as an adequate laboratory surrogate. Lethal and sublethal (post-exposure feeding) responses were assessed for the two species. To evaluate these responses under environmentally realistic exposure conditions, a runoff event was simulated in an agricultural area previously contaminated with different deltamethrin concentrations. The resultant runoff water was used to set up microcosms with different dilutions, simulating the entrance of runoff water in an adjacent lentic system. An in situ assay with D. brachyurum was performed inside the microcosms, allowing to discriminate the effects due to deltamethrin from those due to other potential stressors associated with the experimental design (e.g. organism handling, load of suspended particles, microcosm design). Water samples were collected from microcosms to conduct a laboratory assay with D. magna. The in situ methodologies revealed to be suitable to conduct assays with D. brachyurum under tropical conditions, since all exposed organisms were successfully retrieved from the chambers. Furthermore, none of the potential stressors associated with the experimental design influenced the daphnids’ performance. The tropical cladoceran species, exposed under more realistic conditions, revealed to be more sensitive than the laboratory standard species: lethal effects were only observed for D. brachyurum and sublethal effects were noticed at a lower deltamethrin concentration for this species than for D. magna.     

Dose-response relationship in lethal and behavioural effects of different insecticides on the parasitic wasp Aphidius ervi

Neurotoxic insecticides are widely used for crop protection and behavioural perturbations can be expected in surviving beneficial insects, including parasitoids of pest insects. The present study aims to investigate the relationship between the dose of insecticide parasitoids have been exposed to, and the subsequent ability of these parasitoids to respond to host-related cues. A four-armed olfactometer, a design widely used to observe orientation responses in various insects and parasitoids in particular, was chosen to investigate the dose-response relationship. The species studied was Aphidius ervi, a relatively generalist parasitoid of aphids, and commercialised for biological control and integrated pest management. Active ingredients with similar and different modes of action on the nervous system were compared: a pyrethroid (lambda-cyhalothrin), an organophosphate (chlorpyrifos), a carbamate (pirimicarb) and a carbamyltriazole (triazamate). Adult females were exposed to dry residues on glass for 24 h. LD50 were calculated and predicted a high risk of mortality at the field application rate. The effect of five increasing residual doses of each active ingredient was tested on responses to plant-host odour in the olfactometer, from sublethal doses to LD50, and up to LD70 for some products. It appeared that none of the doses of lambda-cyhalothrin, chlorpyriphos and pirimicarb had any effect on A. ervi responses to the odour from the aphid-infested plant (Myzus persicae on oilseed rape). But for triazamate, a significant dose-behavioural response was quantified and attraction to the odour was no longer significant in females surviving the LD50. The possible explanations for the presence or absence of effect, depending on the insecticide are discussed.     

Effects of a selenium-enriched diet on antioxidant response in adult crayfish (Procambarus clarkii)

Many diets employed in aquaculture are enriched with selenium to improve the diet quality and its conservation. The aim of the study was to investigate the effects of a diet enriched in selenium (1.21 mg kg(-1)) on the antioxidant response of Procambarus clarkii (Girard, 1852). Crayfish fed a diet with lower selenium content (0.30 mg kg(-1)) were the control. Selenium accumulation, enzymatic activities, and total glutathione were evaluated in hepatopancreas of adults of both sexes fed with both diets for 50 days at two experimental times (T(30), T(50) days). Treated females exhibited the highest selenium bioaccumulation during both experimental times, while treated males displayed the highest selenium concentration after 30 days, compared to control crayfish. A sex-related difference was found for the response of the analyzed enzymes in the selenium diet-treated specimens. In fact, superoxide dismutase, glutathione peroxidase and glyoxalase I activities in males were more sensitive compared with females, showing depleted activities in both experimental times. Catalase activity was induced in females (T(50)), while glutathione S-transferase activity was the highest in treated females and the lowest in treated males, compared with own controls. Only glutathione reductase activity and glutathione content showed the same trend in both sexes, which were both lowered in treated specimens, when compared with control crayfish. This result might be due to the effect of selenium toxicity on this freshwater species. Males and females of P. clarkii showed a different susceptibility to the prooxidant effects in a Se-enriched diet.     

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.     

Biochemical effects of long term exposure to Cr,Cd,Ni on rainbow trout (Salmo gairdneri Rich.) : Influence of sex and season

$\text{Salmo gairdneri}$ specimens were exposed for 6 months to low concentrations of Cr,Cd,Ni, and their mixture. Treated animals, particularly males, showed an impairment in glucidic metabo - lism, a modification in lysosomal function, and alterations in gill sialic acid content.Some of these alterations persist in males after 3 month recovery, with only exception for Ni - treated animals.A connection between sex, seasonal cycle, and biochemical response to metal pollution was observed.     

A comparison of the effects of organophosphate insecticide exposure and temperature stress on fluctuating asymmetry and life history traits in Culex quinquefasciatus.

Effects of exposure to a non-chemical (temperature) or chemical (organophosphate insecticide) stressor during larval development were compared in Culex quinquefasciatus mosquitoes. Stress was measured in two ways: using conventional life history traits (survival, development time and a measure of body size) and by calculating the degree of developmental instability from the departure from bilateral symmetry of wing characters (fluctuating asymmetry). Increasing insecticide dose, but not temperature, was observed to elevate wing fluctuating asymmetry in male but not female mosquitoes. Insecticide treatment reduced survival and was associated with a significant reduction in wing trait sizes in both females and males but did not significantly affect development time. Temperature was associated with a significant reduction in all life history traits in both sexes. Therefore wing fluctuating asymmetry in C. quinquefasciatus cannot be used as a general biomonitor of all stress, although it may have potential as a more specific monitor of chemical stress. It needs to be complimented with other measures such as life history and biochemical methods. The significant differences in response between sexes may impact on results of short-term larval exposures to insecticides.     

Reproduction disturbances of Brachionus calyciflorus (rotifer) for the screening of environmental endocrine disrupters

Rotifers and especially the Brachionus calyciflorus species have already shown advantages (e.g. good sensitivity, simplicity, ecological relevance, short generation time) for the chronic toxicity assessment of water pollutants. In this study, the B. calyciflorus three-day test was evaluated on ethinylestradiol, nonylphenol and testosterone for the determination of endocrine disrupting (reproductive) effects. Reproduction (intrinsic rate of population increase) and sex ratio (males/females and mictic females/amictic females) were explored and discussed as suitable endpoints. B. calyciflorus has shown a fair sensitivity to detect reproductive disrupting effects after exposure to ethinylestradiol, nonylphenol and testosterone. Population growth (intrinsic rate of population increase, r) and the ratio ovigerous females/non-ovigerous females are both suitable endpoints, whereas the occurrence of males was not frequent enough to be used as endpoint.     

The chronic toxicity of fenoxycarb to larvae of the grass shrimp,Palaemonetes pugio

Abstract

This study examined effects of fenoxycarb, a carbamate insecticide, on larvae of the grass shrimp, Palaemonetes pugio. In laboratory experiments, grass shrimp larvae were exposed to fenoxycarb from hatch to postlarval metamorphosis in a chronic, static renewal bio assay. LC50's ranged from 0.92 mg/L at 96 h to 0.35 mg/L at the end of the study (24 days). In assessing sublethal effects of fenoxycarb, postlarval emergence was significantly (p < 0.05) reduced in exposed grass shrimp as compared with controls, and the time to reach postlarval status was significantly (p < 0.05) increased in exposed grass shrimp. Significant differences were not found in other sublethal parameters including postlarval dry weight and intermolt duration. Analysis of fenoxycarb from spiked seawater samples showed concentrations declined by 32 to 42% after 24 h.     

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.     

The risks posed by deltamethrin drift to hedgerow butterflies

The susceptibilities of Pieris rapae and P. brassicae (Lepidoptera: Pieridae) to topical treatment with deltamethrin were determined. LD(50)s continued to fall for an extended period after treatment and did not reach a clear end-point for P. rapae. This indicated a failure to excrete or metabolise the active ingredient, which may have continued to exert toxic effects throughout the insect's life cycle. Weight loss by P. brassicae larvae was detected at sublethal rates of exposure and treated insects exhibited feeding inhibition and produced smaller pupae and adults. Residual exposure bioassays over 72 h for P. brassicae exposed to deltamethrin deposits on cabbage leaves, detected toxic effects at rates as low as 1/520th of field application rate. LD(50)s again fell for an extended period after exposure. A model predicting mortality at given levels of drift indicated high levels of short-term risk to larvae exposed to rates of drift deposition recorded in the field. The potential of buffer zones to reduce the toxicological impact of spray drift in the field is discussed.     

Bioaccumulation of lead, mercury, and cadmium in the greater white-toothed shrew, Crocidura russula, from the Ebro Delta (NE Spain): sex- and age-dependent variation

We quantified bioaccumulation of lead, mercury, and cadmium in bones from 105 greater white-toothed shrews (Crocidura russula) collected at the Ebro Delta, a polluted area, and the Medas Islands, a control site. Lead and mercury levels varied with site, age, and sex, although statistical significances depended on each factor. Globally, shrews from the polluted area exhibited significantly higher concentrations of Pb and Hg. Increment of Pb with age was particularly remarkable in wetland animals and was interpreted in relation to human activities, namely hunting. Unlike males, females from the Ebro Delta maintained low Hg levels, which were associated with gestation and lactation. Cadmium levels did not differ between sites, sexes, or ages. This study provides the first data on heavy metals in mammals from this wetland and suggests that C. russula is a good bioindicator of metal pollution. We concluded that sex and age may represent an important source of variation in the bioaccumulation of these metals in wild populations.     

The combined effect of lead exposure and high or low dietary calcium on health and immunocompetence in the zebra finch (Taeniopygia guttata)

The widespread contamination by lead and the acidification of the environment ask for a better understanding of the effects of the interaction between lead and calcium on various aspects of health, including disease defense, in wildlife. Here, we investigated the effects of chronic exposure to sublethal levels of lead, combined with high or low dietary calcium, on health and several components of immunity in male and female zebra finches (Taeniopygia guttata). Thirty individuals of each sex were randomly assigned to three groups: a control group, a group exposed to lead with an additional calcium source (i.e. grit) and a group exposed to lead without access to an extra calcium source. Lead was administered as lead acetate via the drinking water (20 ppm) for 38 consecutive days. Exposure to lead increased significantly the concentrations of lead in kidney and bone in individuals of the experimental groups. Furthermore, the lack of a calcium supplement significantly enhanced the uptake of lead. Lead did not affect health indices such as hematocrit, spleen mass and body mass, nor the adrenal stress response. Cell-mediated immune responsiveness, assessed by a delayed-type hypersensitivity response to phytohaemagglutinin, was also not affected by lead exposure. On the other hand, lead exposure did significantly suppress the secondary humoral immune response towards sheep red blood cells in females, but only when the additional calcium source was not available. This effect was not found in males, suggesting sexual differences in susceptibility of humoral immunity to lead treatment in zebra finches.     

Diet-mediated effects of heavy metal pollution on growth and immune response in the geometrid moth Epirrita autumnata

The potential capacity of larval growth and immune response traits of the autumnal moth to adapt to heavy metal polluted environment was tested experimentally. Both the relative growth rate (RGR) and pupal weight were significantly higher in control trees than on polluted trees, indicating that metal pollution prevented the insect from achieving maximal growth on birch leaves. Larval growth rates of different broods differed significantly between metal contaminated and control birches. However, pupal weight of broods, which is considered more important for fitness than growth rate, in response to pollution did not differ. Immune response was significantly higher in moths exposed to pollution than in moths that were exposed to control environment suggesting that pollution enhances the immune defense of defoliators. Encapsulation rate tended to differ between broods indicating that the immune function has potential to respond to selection.     

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.     

Organochlorine contaminant and retinoid levels in blubber of common dolphins (Delphinus delphis) off northwestern Spain

The effect of age, sex, nutritive condition and organochlorine concentration on blubber retinoid concentrations was examined in 74 common dolphins incidentally caught off northwestern Spain. Age and blubber lipid content were strong determinants of the retinoid concentrations in males, while these variables did not account for the variation found in females. Retinoids were positively correlated with organochlorines in males and negatively in females. However, pollution levels were moderate and likely to be below threshold levels above that a toxicological response is to be expected. Thus, a cause-effect relationship between organochlorine and retinoid concentrations could not be properly established, and the observed correlation may be the result of an independent association of the two variables with age. Further research on the influence of the best predictor variables on retinoid dynamics is required to implement the use of retinoids as biomarkers of pollutant exposure in cetaceans.