Virulence, horizontal transmission, and sublethal reproductive effects of Metarhizium anisopliae (Anamorphic fungi) on the German cockroach (Blattodea: Blattellidae)

Virulence of Metarhizium anisopliae (Metschnikoff) Sorokin strain EAMa 01/121-Su against the German Cockroach, Blatella germanica (L.), was determined using four concentrations ranging from 4.2 x 10(6) to 4.2 x 10(9) spores per milliliter. The LD50 value was 1.4 x 10(7) spores per milliliter (56,000 spores per cockroach) and LT50 values were 14.8 days and 5.3 days for 4.2 x 10(8) and 4.2 x 10(9) spores per milliliter, respectively. An experiment was conducted to evaluate whether a fungal transmission could exist among infected and healthy cockroaches. Percentage mortality at a ratio of 1:10 of infected to unexposed cockroaches was 87.5% and LT50 was 12.2 days, which indicated the potential of this strain to be horizontally transmitted and to rapidly spread the infection in the insect population. The effect of a sublethal dose (ca. LD60) of M. anisopliae EAMa 01/121-Su strain, applied topically on German cockroaches, was studied by reciprocal crossing. Othecal production, oothecal hatchability, and nymphal production declined upon exposure to M. anisopliae EAMa 01/121-Su strain. The mean number of oothecae laid by female was progressively and significantly reduced by fungal treatment from second oviposition period onwards. Oothecal hatch of fungally challenged females was reduced by 46-49%, oothecal viability by 48-85%, and nymphal production by 22-35%. Only treated females showed an effect on oothecal production, oothecal hatch, and nymphal production, although oothecal hatch was also governed by treated males at a higher significance level. Our results on virulence and horizontal transmission of fungal conidia of M. anisopliae EAMa 01/121-Su strain and its sublethal reproductive effects on German cockroach females are discussed in terms of its potential to decrease the pest status of B. germanica in the short and long terms.     

Effects of several insecticide formulations on oothecal drop and hatchability in German cockroaches (Dictyoptera: Blattellidae)

Formulations used for control of German cockroaches, Blattella germanica (L.), were investigated. The insecticides tested on gravid females were bendiocarb, chlorpyrifos, cyfluthrin, cypermethrin, fenvalerate, hydramethylnon, malathion, propetamphos, propoxur, and pyrethrins. Exposure to each insecticide increased the frequency of oothecal drop and reduced the percentage oothecal hatch. The percentage of oothecae that were dropped increased as a curvilinear function of insecticide concentration. An LD50 of propoxur to female German cockroaches resulted in the greatest oothecal drop (83.50%); fenvalerate caused the least drop (22.60%). LD50's of cypermethrin, propetamphos, and propoxur resulted in 29.60, 31.807, and 37.30% hatch from dropped oothecae, respectively. The smallest percentage hatch from retained oothecae was caused by LD50's of propoxur (1.5%) and cyfluthrin (7.70%). Retained oothecae from females treated with an LD50 of fenvalerate (68.70%) or pyrethrins (68.70%) had the greatest percentage hatch. Total percentage hatch (dropped and retained oothecae) declined exponentially as the insecticide concentration increased. An LD50 of cypermethrin limited total oothecal hatch to 24.50%, whereas LD50's of fenvalerate, malathion, and pyrethrins resulted in 53.60, 52.20, and 58.90% hatch, respectively. Mean time to oothecal hatch increased linearly with increasing insecticide concentration for all insecticides tested.     

Sublethal effects of insecticides on adult longevity and fecundity of German cockroaches (Dictyoptera: Blattellidae).

The effects of sublethal concentrations of chlorpyrifos, cyfluthrin, and hydramethylnon on adult longevity and fecundity of German cockroaches, Blattella germanica (L.), were investigated. Longevity of males declined linearly with increasing doses of insecticide. An LD50 of cyfluthrin decreased male longevity by 52%, whereas an LD50 of hydramethylnon reduced male longevity by 81%. Longevity of females increased linearly with increasing sublethal doses of chlorpyrifos, whereas all doses of both cyfluthrin and hydramethylnon decreased longevity of females. Fecundity increased linearly with increasing sublethal doses of chlorpyrifos. Number of oothecae formed, oothecae hatched, and number of offspring produced in each ootheca increased with increasing sublethal concentrations of chlorpyrifos. In contrast, fecundity declined with increasing sublethal concentrations of cyfluthrin and hydramethylnon. Formation of the first ootheca occurred approximately 8 d after mating for untreated females but generally longer with sublethal concentrations of all insecticides. The period between oothecae hatch and the formation of subsequent oothecae increased with successive oothecae in all treatments.     

亚致死剂量杀虫剂对意蜂工蜂嗅觉敏感性的影响

喙伸反应(PER)试验适用于评价杀虫剂对蜜蜂行为的影响。本实验利用喙伸反应研究了亚致死剂量(LD50/100～LD50/10)溴氰菊酯和吡虫啉对意蜂Apis mellifera ligustica L.工蜂嗅觉敏感性的影响。结果发现,经口饲喂溴氰菊酯5ng和10ng后,工蜂对0.1%的蔗糖溶液的敏感性显著下降(P<0.05),水应激指数降低,但对0.3%,1%,3%,10%和30%的蔗糖溶液的敏感性没有显著变化;而经口饲喂吡虫啉0.3ng和0.6ng后,工蜂对上述各浓度蔗糖溶液的敏感性变化不明显,但其水应激指数升高。     

Mutagenic evaluation of deltamethrin using rodent dominant lethal assay

The dominant lethal test was used to analyse the mutagenic potential of deltamethrin, a synthetic pyrethroid insecticide, in Swiss albino mice. In the treated series, the animals were exposed orally to three different doses (0.36, 0.72 and 1.08 mg/kg body weight) of deltamethrin dissolved in corn oil. Following the treatment, each male of control, as well as of the treated series, was mated with untreated females, every week for a period of 6 weeks. All mated females were sacrificed on the 13th day of separation and their ovaries and uterus were examined. The results revealed that deltamethrin treatment did not impair the mating capacity and fertility of Swiss albino mice. Mutagenic index, pre- and post-implantation losses were assessed. No significant pre-implantation losses were observed either weekly or averagely. Post-implantation losses were observed at medium and high doses of deltamethrin. A slight increase in dominant lethal mutation rate was observed by increasing doses of deltamethrin in early weeks but decreased in later weeks, so an apparent dose response was not observed.     

Toxicity, sublethal effects, and performance of sulfluramid against the German cockroach (Dictyoptera: Blattellidae)

Topical and oral toxicity of sulfluramid (N-ethyl perfluorooctane sulfonamide) were determined for the German cockroach, Blattella germanica (L.). The topical LD50 of sulfluramid was 175.6 micrograms/g for adult males, 117.8 micrograms/g for adult females, and 122.3 micrograms/g for gravid adult females. Ingestion increased toxicity approximately 1.4 times for adult male B. germanica. Twenty-four hours after topical treatment with 20 micrograms/insect sulfluramid, the percentage of female cockroaches that dropped their oothecae increased approximately 50% compared with controls treated with acetone. Sulfluramid also decreased oothecal hatch of both dropped and retained oothecae. Approximately 90% of oothecae from untreated females hatches, whereas less than 20% hatched from females treated with 20 micrograms/insect. Mean time for oothecal hatch increased linearly with increasing sulfluramid concentration. In arena studies in Ebeling choice boxes, LT50's ranged between approximately 2.3 and 3.9 d for a 0.331 mg/cm2 deposit and a 1.5% bait, respectively. Higher concentrations of sulfluramid were more repellent in both bait and residual formulations. Performance index values indicated excellent potential field efficacy. Field trials with 1.0 and 1.5% (AI) baits showed up to a 71.3% reduction in cockroach numbers. Baits controlled cockroaches throughout the 12-wk test.     

Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)

Effects of sublethal concentrations (LC₂₅) of six insecticides (imidacloprid, rotenone, fenvalerate, abamectin, pirimicarb and azadirachtin) on fecundity and wing dimorphism of the green peach aphid, Myzus persicae (Sulzer), were studied both under laboratory and greenhouse conditions. In the laboratory, aphid reproduction reduced by 44.29% and 54.01% when rotenone and abamectin treatments were applied at sublethal dose, respectively, and sublethal fenvalerate application resulted in markedly lower average reproduction per female per day compared with control. Reproductive duration of aphid treated with abamectin significantly decreased by 44.19%. But in the greenhouse, there were no evident differences in the aphid fecundity and reproductive duration between treatments and control. Life‐table parameters also demonstrated that the six insecticides at sublethal doses did not stimulate the aphid reproductive potential. In the laboratory, after being exposed to sublethal doses of imidacloprid and fenvalerate, the proportions of alate progeny in aphid progeny were significantly higher than that of the control. In the greenhouse, percentages of alate offspring from the mother aphids treated with imidacloprid, fenvalerate and abamectin increased pronouncedly compared with control. Mortality rates of offspring in the nymphal stages from adults treated with insecticides revealed no significant changes between laboratory and greenhouse. The developmental time in days of the offspring varied in all treatments. Mechanisms of insecticide‐induced resurgence are discussed.     

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.     

转Bt基因及其亲本水稻上褐飞虱对三唑磷和溴氰菊酯的反应

以转Bt基因抗虫水稻T1C-19(含cry1C基因)和T2A-1(含cry2A基因)及其亲本水稻MH63为材料,用20和40 mg·L^-1的三唑磷以及1、3和6 mg·L^-1的溴氰菊酯喷雾分别处理稻株上的3龄褐飞虱若虫,研究了两种农药对转Bt基因抗虫水稻上褐飞虱再猖獗的影响.结果表明： 三唑磷处理对褐飞虱的若虫历期无显著性影响,溴氰菊酯则能显著降低若虫历期,但随着两种药剂处理浓度的升高,若虫的存活率降低、成虫的产卵量增加.在同一浓度农药药剂处理下,3个水稻品种上的褐飞虱若虫发育历期、若虫存活率、初羽雌成虫体质量、产卵量和卵孵化率等生态学参数均没有显著差异.表明褐飞虱在两种转Bt水稻上对三唑磷和溴氰菊酯诱导再猖獗的反应能力与其亲本水稻MH63没有差异.     

亚致死剂量马拉硫磷和西维因对飞蝗P450基因表达研究

采用实时定量PCR技术检测飞蝗Locusta migratoria细胞色素P450基因CYP4G62、CYP6EL1和CYP9AQ1经马拉硫磷和西维因不同亚致死剂量和不同时间处理后mRNA的表达水平。结果表明,经马拉硫磷不同亚致死剂量LD10、LD30和LD50处理后,飞蝗CYP4G62和CYP6EL1均在高剂量LD50被显著诱导,分别为对照的3.03和2.0倍,而在低剂量LD10无显著性差异。CYP9AQ1在3个亚致死剂量下表达量均显著提高,且增量随处理浓度增加而降低。经西维因3个亚致死剂量处理后,除在LD30这一浓度下引起CYP4G62表达提高外,其它的P450基因均无显著性差异。选择2种农药的LD15对飞蝗进行点滴处理,分别检测6、12、24和48 h基因的相对表达。经马拉硫磷LD15处理后,除CYP6EL1在12 h和CYP9AQ1在24 h表达量显著降低外,其它各时间点基因表达均无显著差异。经西维因处理不同时间后,3个P450基因的相对表达量均无显著性差异。综合上述结果说明马拉硫磷对3个细胞色素P450基因有一定的诱导作用,而西维因对其无诱导作用。     

The effect of exposure to imidacloprid on Asian longhorned beetle (Coleoptera: Cerambycidae) survival and reproduction

The effect of imidacloprid delivery method and application rate on survival of adult Asian longhorned beetles, Anoplophora glabripennis (Motschulsky), was studied, along with the effect of repeated daily ingestion of imidacloprid on the survival and reproductive capacity of adult females. Beetles exposed repeatedly to 50 ppm imidacloprid died in < 2-3 wk, whether dosed orally each day, or through contact exposure. Beetles given 1 microl of 50 ppm imidacloprid daily for two, three, four, or five consecutive days died sooner with increasing consecutive days: the beetles treated for 5 d all died within 15 d, while 80% of beetles treated for only 2 d lived > 8 wk. For females given 1 microl daily, across a range of doses from 2 to 50 ppm imidacloprid, the total number of viable eggs laid was reduced with increasing dosage, but percentage egg viability was not affected. Survival of females at dosages of 10 or 30 ppm/d was not significantly reduced compared with controls but these females laid 23-38% fewer viable eggs, suggesting a sublethal effect of imidacloprid. Female beetles given 1 microl/d of 40 or 50 ppm imidacloprid died more quickly than controls and viable egg production was reduced 82-93%, because of a combination of lethal and sublethal effects of intoxication.     

溴氰菊酯对飞蝗羧酸酯酶基因表达的影响

【目的】研究溴氰菊酯作用下飞蝗羧酸酯酶基因的mRNA表达特性,为溴氰菊酯的代谢解毒及飞蝗Locusta migratoria防治中抗性风险的评估提供基础资料。【方法】本文采用不同剂量溴氰菊酯处理3龄飞蝗,提取总RNA,体外反转录合成cDNA模板,采用Real-time PCR技术分析飞蝗羧酸酯酶基因在溴氰菊酯不同浓度和不同时间处理后的表达模式。【结果】飞蝗经不同浓度溴氰菊酯处理12 h后,LmCesA3和LmCesE1表现为诱导效应;除LmCesA2外,其余羧酸酯酶基因经溴氰菊酯LD30剂量处理后分别在不同的时间点表现为诱导效应。【结论】5个羧酸酯酶基因LmCesA1、LmCesA3、LmCesD1、LmCesE1和LmCesI1可以被溴氰菊酯诱导,表明其可能参与飞蝗对溴氰菊酯的代谢解毒及抗性产生。     

Insecticide susceptible/resistance status in Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Thailand during 2003-2005

Susceptibility baselines and diagnostic doses of the technical grade insecticides deltamethrin, permethrin, fenitrothion, and propoxur were established based on Aedes aegypti (L.), Bora (French Polynesia), a reference susceptible strain. Field-collected Aedes mosquitoes from each part of Thailand were subjected to bioassay for their susceptibility to the diagnostic doses of each insecticide. Almost all Ae. aegypti collected were incipient resistant or resistant to deltamethrin and permethrin, except those from some areas of Songkhla (southern) and Phan district of Chiang Rai (northern) province. Susceptibility to fenitrothion was found in mosquitoes from Bangkok (central), Chonburi (eastern), Chiang Rai, Kanchanaburi (western), and Songkhla, whereas they were resistant in almost all areas of Nakhon Sawan (north central) and Nakhon Ratchasima (northeastern) provinces. Most of Ae. aegypti were susceptible to propoxur except those from Mae Wong, Nakhon Sawan province. Various levels of insecticide resistance and susceptibility in adjacent areas revealed a focal susceptible/resistance profile in the country. It could be noted that almost all of Ae. albopictus were susceptible to the insecticides tested at the same diagnostic doses. In conclusion, resistance to pyrethroids (permethrin and deltamethrin) has developed in Ae. aegypti in most of the collected areas, suggesting that an alternative choice of insecticide or other control measures should be applied.     

Sublethal effects of antibiosis resistance on the reproductive biology of two spittlebug (Hemiptera: Cercopidae) species affecting Brachiaria spp

Several greenhouse experiments were used to measure how high levels of antibiosis resistance to nymphs in two interspecific Brachiaria (brachiariagrass) hybrids affect life history parameters of the spittlebugs Aeneolamia varia (F.) and Zulia carbonaria (Lallemand), two of the most important spittlebug (Hemiptera: Cercopidae) species affecting Brachiaria production in Colombia. The A. varia-resistant hybrid CIAT 36062, the Z. carbonaria-resistant hybrid SX01NO/0102, and the susceptible accession CIAT 0654 were used to compare the effect of all possible combinations of food sources for nymphs and adults. Calculation of growth indexes showed a significant impact of antibiosis resistance on the biology of immature stages of both species. Median survival times of adults feeding on resistant genotypes did not differ from those recorded on the susceptible genotype, suggesting that factors responsible for high mortality of nymphs in the resistant hybrids did not affect adult survival. Rearing nymphs of A. varia on CIAT 36062 and of Z. carbonaria on SX01NO/0102 had deleterious sublethal effects on the reproductive biology of resulting adult females. It is concluded that high nymphal mortality and subsequent sublethal effects of nymphal antibiosis on adults should have a major impact on the demography of the two spittlebug species studied.     

Sublethal effects of imidacloprid on Bemisia tabaci (Hemiptera: Aleyrodidae) under laboratory conditions

The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most important pests in tropical and subtropical agriculture and is a key pest in greenhouse production worldwide. Current management of B. tabaci relies upon frequent applications of insecticides. Insecticide use not only directly affects pest populations through acute toxicity but also has indirect (sublethal) effects on pest physiology or behavior. In this study, we described sublethal effects of imidacloprid on adult feeding, immature development, adult fecundity, and F1 development of B. tabaci. Honeydew excretion of adults feeding on leaves treated with LC20 and LC40 concentration was significantly lower than that on untreated leaf discs. Egg production of B. tabaci adults subject to LC20 and LC40 concentrations also was less than untreated individuals. Upon transfer to untreated leaves, honeydew excretion and egg production recovered well within 24 and 48 h, respectively. Exposure to LC20 and LC40 concentrations significantly affected developmental time of B. tabaci eggs and nymphs, whereas it did not affect adult molting rate. We did not find sublethal effects on longevity and fecundity of B. tabaci adults when exposed to LC90 and LC40 concentrations for 24 h, and on egg hatching rate, nymphal mortality, and molting rate of the subsequent F1 generation. Exposure to imidacloprid at LC40 concentration significantly decreased the number of females in the F1 generation. Imidacloprid negatively affects development and reproduction of exposed individuals, and sex ratio of subsequent (F1) generation of B. tabaci, which probably disrupts B. tabaci population dynamics, slows population increase, and reduces infestation levels. Therefore, it is necessary to consider potential impact from imidacloprid for integrated management of the pest.     

溴氰菊酯亚致死浓度对烟草粉螟生物学特性的影响

为探讨溴氰菊酯对烟草粉螟的亚致死效应,本文采用烟叶浸渍法以溴氰菊酯亚致死浓度(LC 10和LC 25)胁迫烟草粉螟3龄幼虫,并通过年龄-龄期两性生命表的方法探究溴氰菊酯胁迫对烟草粉螟发育和繁殖的影响。结果显示:与对照相比,溴氰菊酯LC 10、LC 25处理F 0代的平均单雌产卵量显著下降;LC 25处理F 0代的产卵前期及总产卵前期明显长于对照;LC 25处理与LC 10处理和对照间,F 0代雌、雄虫寿命均差异显著;LC 10处理和LC 25处理F 1代与对照存活率明显下降,F 1代各处理间的卵、1龄幼虫、3龄幼虫、5龄幼虫、7龄幼虫和蛹的发育历期无显著差异;但LC 25处理组2龄、4龄、6龄幼虫历期比对照延长了且差异显著;LC 25处理组的成虫前期比对照组延长了且差异显著。同时LC 25处理的雌、雄虫寿命最短,但3个处理间差异不显著。研究表明,亚致死浓度的溴氰菊酯能够抑制烟草粉螟的生长发育和繁殖,以上研究结果可为田间用药控制烟草粉螟提供理论参考。     

Influence of azadirachtin on development and reproduction of Nezara viridula L. (Het., Pentatomidae)

Abstract:  The potential of azadirachtin as an insect growth regulator was evaluated in Nezara viridula L. by applying different doses to fifth instar nymphs. At doses of 200–500 ng per insect almost all the individuals died during moulting to adults and the survivors showed a great number of nymphal characteristics, and also died very soon after. At lower doses, from 2 to 50 ng per insect, approximately 50% of the adults seemed normal. No effect was observed during the last nymphal instar, even at the highest dose applied. The fertility and fecundity of adults, males and females, developing from nymphs treated with different low doses of azadirachtin were also studied. When azadirachtin was applied at 20 ng per insect on fifth instar nymphs, females developing from these nymphs showed a conspicuous reduction of fecundity. This same effect was evident when untreated females mated with males obtained from treated nymphs. Finally, azadirachtin applied at 1  μ g/cm² to the oviposition surface showed a remarkable oviposition repellency.     

Effects of photoperiod,temperature and melatonin on nymphal development,polyphenism and reproduction in Halyomorpha halys (Heteroptera: Pentatomidae)

Influences of photoperiod, temperature and melatonin were examined on development and color patterns of nymphs, and sternum color and reproductive fate of adults in Halyomorpha halys (brevis). Short-day accelerated nymphal development, whereas long-day accelerated reproductive maturation. The two types of photoperiodic responses at different stages may help maintain the univoltinism of this species in the field, assuring the right timing for diapause and reproduction. The pronotum of fifth instar nymphs reared under LD 11:13 shows a brown-marbled color pattern darker, with less creamy-yellowish speckles, than that of nymphs reared under LD 16:8. Short-day-reared fifth instar nymphs, which are destined to diapause in adults, had shorter white stripes on the pronotum, smaller body size, less frequent feeding and more lipid accumulation than the long-day-reared. The longer the exposure to LD 13:11 at 20 degrees C during the nymphal stage, the greater the expression of short-day associated characteristics observed in the fifth nymphal instar and adult stage. Melatonin orally administered (500 microg/ml) to insects under LD 16:8 produced slightly reduced body size, suppressed feeding, extended nymphal period and increased accumulation of lipid compared to the untreated bugs, but did not affect the incidence of diapause in females. In males, melatonin retarded gonadal development under LD16:8. These results may suggest a possible role of melatonin for the control of seasonal polyphenism and development.     

Effects of sublethal doses of deltamethrin on the pair Glossina morsitans morsitans-Trypanosoma (Nannomonas) congolense

The presence of Trypanosoma in Glossina morsitans morsitans induced a decrease in the physiological activity which is expressed in particular by a statistically higher mortality rate of infected flies. A similar effect appears with sublethal doses of deltamethrin either in infected or non infected insects. A cumulative activity of both effects was also observed in infected and treated flies. Sublethal doses of the pyrethroid compound showed a delay in feeding, abortions and larval clampings. Moreover, deltamethrin demonstrated an intravectorial effect against Trypanosoma which can reduce the transmission ability of flies.     

Stimulus frequency dependence of the central and peripheral somatosensory evoked activity in rats treated with various pesticides

Rats were treated with a combination of insecticide agents in different timing schemes. In acute administration, 1/5 LD50 of the three insecticides: dimethoate, propoxur and cypermethrin, or their combination, was given once by gavage. In the developmental model, female rats received oral doses of 1/25 LD50 of the above insecticides in combination in three timing schemes including pregnancy and lactation. Responses in the somatosensory cortex and in the tail nerve, evoked by peripheral electric stimulation, were recorded in acute preparation under urethane anesthesia. It was tested whether the parameters of the cortical and peripheral evoked response are dependent on the frequency and whether this dependence is different in control and treated animals. The latency increase of the cortical responses with increasing stimulation frequency was significantly stronger in rats treated acutely with cypermethrin and the combination, and in rats receiving the combination during both intra- and extrauterine development. On the duration, the effects were less clear. Frequency dependent increase of the tail nerve action potential latency was significantly intensified by cypermethrin, and the amplitude decrease, by cypermethrin and dimethoate. Fatigue of this response during a stimulation series was also altered by the insecticides. Frequency dependence and fatigue possibly reflect the actual state of the nervous system and may have the potency to be developed to functional biomarkers.