Inheritance of resistance to pyriproxyfen in Bemisia tabaci (Hemiptera: Aleyrodidae) males and females (B biotype)

We evaluated effects of the insect growth regulator pyriproxyfen on Bemisia tabaci (Gennadius) (B biotype) (Hemiptera: Aleyrodidae) males and females in laboratory bioassays. Insects were treated with pyriproxyfen as either eggs or nymphs. In all tests, the LC50 for a laboratory-selected resistant strain was at least 620 times greater than for an unselected susceptible strain. When insects were treated as eggs, survival did not differ between males and females of either strain. When insects were treated as nymphs, survival did not differ between susceptible males and susceptible females, but resistant males had higher mortality than resistant females. The dominance of resistance decreased as pyriproxyfen concentration increased. Resistance was partially or completely dominant at the lowest concentration tested and completely recessive at the highest concentration tested. Hybrid female progeny from reciprocal crosses between the susceptible and resistant strains responded alike in bioassays; thus, maternal effects were not evident. Rapid evolution of resistance to pyriproxyfen could occur if individuals in field populations had resistance with traits similar to those of the laboratory-selected strain examined here.     

THE TOXICITY OF DDT IN ABRASIVE AND NON-ABRASIVE DUSTS TO THE RICE WEEVIL, CALANDRA ORYZAE L. (COLEOPT., CURCULIONIDAE)*

The toxicity of DDT in different dust carriers to the rice weevil, Calandra oryzae , was determined under standardized conditions, using deposits large enough to ensure that the insects accumulated an excess of dust.
Some evidence was obtained that DDT is transported to the cuticle as a vapour.
At high humidity, the toxicity of DDT was not markedly affected by any carrier except charcoal which reduced the toxicity, probably by absorption of DDT vapour. Small differences in toxicity of DDT caused by other carriers could not be accounted for by differences in their average particle size, bulk density, amount adhering to insect, surface area, abrasiveness to insects or effect on behaviour of the insect.
At low humidity, abrasive dusts killed the insects by desiccation, thus adding to the toxic effect of DDT. Abrasion of the insect's cuticle did not affect the apparent rate of penetration of DDT at 50% R. H. or at 95% R. H.
Starved insects were more susceptible to DDT poisoning, and in some experiments abrasive carriers increased the toxicity of DDT by preventing the insects from feeding.     

THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES: I. DEVELOPMENT OF RESISTANCE TO DDT IN A STRAIN OF DROSOPHILA MELANOGASTER MEIG.

Successive spraying with DDT suspensions of the adults of a wild colony of Drosophila melanogaster and the progeny of survivors enhanced the resistance to that insecticide.
The rate at which resistance increased depended on: (1) the relative proportion of resistants to susceptible individuals, or (2) the intensity of selection as measured by the concentration of DDT, the proportion killed or on both. The resistance of the populations of the insects fluctuated considerably whether subjected to successive sprayings or not, and in one sprayed series there was some indication of a rhythm with peaks of susceptibility occurring at regular intervals.
Enhanced resistance may show a change of slope in the probit log concentration regression line, leading to different relative values at different levels of mortality, or by a parallel shift of the regression line. The former appears to be a preliminary stage of selection and indicates a change in the frequency distribution within a population.
Increasing the concentration of DDT, slowly or rapidly, may have enhanced resistances at an increased rate, but the series sprayed with the lower initial concentration reached finally the same end point, as judged by the values of log lc . 50.
During the course of these experiments the insects developed sensitivity to carbon dioxide (used in anaesthesis). Its bearing on our work is considered in Part II.     

The effect of gypsy moth metamorphosis on the development of nuclear polyhedrosis virus infection

The development of nuclear polyhedrosis virus (NPV) infection in gypsy moth (Lymantria dispar) was studied before, during, and after host metamorphosis, and in larvae and pupae in the subsequent generation, to determine whether NPV ingested by late instars can replicate in host tissues through metamorphosis and whether it can be vertically transmitted to progeny. Individuals that survived sublethal dosages of NPV did not differ from undosed insects in pupal weight, fecundity, larval and pupal weight of progeny, or response of progeny to NPV challenge. No evidence of NPV infection or of abnormal histology was found in adult tissues examined by light microscopy and no virus was detected on the surface of eggs produced by NPV-treated moths. No NPV-caused mortality was recorded among undosed progeny of dosed or undosed parents. The progeny of dosed parents were neither more resistant nor more susceptible to LdMNPV than were progeny of undosed parents and lethal times did not differ between groups. Examination of larval, pupal, and adult tissues by DNA hybridization revealed that insects in which NPV DNA was detected died prior to adult eclosion. NPV was not detected in any hosts surviving to the adult stage. These results suggest that survivors of sublethal dosages of NPV avoid infection and are therefore incapable of vertically transmitting infectious virus to progeny.     

氰氟虫腙对小菜蛾阿维菌素抗性和敏感种群的亚致死效应(英文)

在实验室条件下采用生命表技术研究了氰氟虫腙亚致死剂量（LC₂₅）对小菜蛾Plutella xylostella阿维菌素抗性（AV-R）和敏感（AV-S）种群的亚致死效应, 旨在为小菜蛾对阿维菌素的抗性治理提供理论基础。结果表明： 氰氟虫腙对小菜蛾3龄幼虫抗性种群的LC₅₀和LC₂₅分别为0.24 mg/L和0.09 mg/L; 对敏感种群的LC₅₀和LC₂₅分别为0.20 mg/L和0.07 mg/L。氰氟虫腙亚致死剂量0.09 mg/L 处理小菜蛾后, 对处理代的影响表现为显著降低处理种群的化蛹率、 蛹重、 羽化率、 繁殖力; 明显延长蛹期, 缩短成虫产卵期和寿命; 对子代种群的影响表现为显著降低卵的孵化率、 幼虫各龄期的存活率, 延长发育历期。处理种群的内禀增长率（r_m）、 周限增长率（λ）和净增值率（R₀）显著低于对照种群（P<0.0001）。亚致死剂量的氰氟虫腙对小菜蛾抗性种群的影响大于敏感种群, 对处理代种群的影响大于子代种群。氰氟虫腙亚致死剂量可以极大地影响小菜蛾尤其是阿维菌素抗性种群的种群动态, 因此氰氟虫腙对于小菜蛾的抗性治理具有积极的作用。     

Fitness costs of sublethal exposure to Bacillus thuringiensis in Helicoverpa armigera: a carryover study on offspring

Bacillus thuringiensis (Bt) is an efficient entomopathogen used for pest control. While Bt pathogenesis has been thoroughly studied, less is known about the biological effects of sublethal Bt exposure. To address this knowledge gap, we document sublethal effects of Bacillus thuringiensis var. kurstaki (Btk) on the biology and development of Helicoverpa armigera (Hübner) under laboratory conditions. The results obtained revealed that duration of the different life stages in treated neonates of H. armigera was significantly affected by sublethal treatments. Furthermore, fecundity was also negatively affected in female moths developed from Btk‐treated neonates, with the rate of egg hatchability reaching zero in the LC₂₅. We also present data supporting that the effect of sublethal Btk concentrations could carry over to the next generation. Sublethal Btk concentrations reduced the net reproduction rate (R₀), and there were also significant differences among the values of this parameter at all treatments tested when compared with controls. The intrinsic and finite rates of increase (r_m and λ, respectively) were significantly lower in insects treated with sublethal Btk concentrations compared with control insects. Consequent with the reduce rate of development observed for H. armigera treated with Btk, the mean generation time (T) and doubling time (DT) were significantly higher in insects exposed to any Btk concentration tested compared with control. Our data demonstrate significant fitness costs resulting from sublethal Btk exposure in H. armigera. These observations underline the importance of considering the role of sublethal effects when attempting to evaluate the impact of Bt treatment on an insect pest population and its progeny.     

Effects of Bt plants on the development and survival of the parasitoid Cotesia plutellae (Hymenoptera: Braconidae) in susceptible and Bt-resistant larvae of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

A range of crops have been transformed with delta-endotoxin genes from Bacillus thuringiensis (Bt) to produce transgenic plants with high levels of resistance to lepidopteran pests. Parasitoids are important natural enemies of lepidopteran larvae and the effects of Bt plants on these non-target insects have to be investigated to avoid unnecessary disruption of biological control. This study investigated the effects of Cry1Ac-expressing transgenic oilseed rape (Brassica napus) on the solitary braconid endoparasitoid Cotesia plutellae in small-scale laboratory experiments. C. plutellae is an important natural enemy of the diamondback moth (Plutella xylostella), the most important pest of brassica crops world-wide. Bt oilseed rape caused 100% mortality of a Bt-susceptible P. xylostella strain but no mortality of the Bt-resistant P. xylostella strain NO-QA. C. plutellae eggs laid in Bt-susceptible hosts feeding on Bt leaves hatched but premature host mortality did not allow C. plutellae larvae to complete their development. In contrast, C. plutellae developed to maturity in Bt-resistant hosts fed on Bt oilseed rape leaves and there was no effect of Bt plants on percentage parasitism, time to emergence from hosts, time to adult emergence and percentage adult emergence from cocoons. Weights of female progeny after development in Bt-resistant hosts did not differ between plant types but male progeny was significantly heavier on wildtype plants in one of two experiments. The proportion of female progeny was significantly higher on Bt plants in the first experiment with Bt-resistant hosts but this effect was not observed again when the experiment was repeated.     

Effects of Bt cotton and crylac toxin on survival and development of pink bollworm (Lepidoptera: Gelechiidae).

We evaluated the effects of Bacillus thuringiensis (Bt) toxin CrylAc on survival and development of a susceptible strain and laboratory-selected resistant strains of pink bollworm, Pectinophora gossypiella (Saunders). For susceptible and resistant strains tested on artificial diet, increases in CrylAc concentration reduced developmental rate and pupal weight. In greenhouse tests, survival of resistant larvae on transgenic cotton that produces CrylAc (Bt cotton) was 46% relative to their survival on non-Bt cotton. In contrast, Bt cotton killed all susceptible larvae tested. F1 hybrid progeny of resistant and susceptible adults did not survive on Bt cotton, which indicates recessive inheritance of resistance. Compared with resistant or susceptible larvae reared on non-Bt cotton, resistant larvae reared on Bt cotton had lower survival and slower development, and achieved lower pupal weight and fecundity. Recessive resistance to Bt cotton is consistent with one of the basic assumptions of the refuge strategy for delaying resistance to Bt cotton. Whereas slower development of resistant insects on Bt cotton could increase the probability of mating between resistant adults and accelerate resistance, negative effects of Bt cotton on the survival and development of resistant larvae could delay evolution of resistance.     

Sublethal larval exposure to imidacloprid impacts adult behaviour in Drosophila melanogaster

Pesticides are now chronically found in numerous ecosystems incurring widespread toxic effects on multiple organisms. For insects, the larvae are very exposed to pesticide pollution and the acute effect of insecticides on larvae has been characterized in a range of species. However, the carry‐on effects in adults of sublethal exposure occurring in larvae are not well characterized. Here, we use a collection of strains of Drosophila melanogaster differing in their larval resistance to a commonly used insecticide, imidacloprid, and we test the effect of larval exposure on behavioural traits at the adult stage. Focusing on locomotor activity and on courtship and mating behaviour, we observed a significant carry‐on effect of imidacloprid exposure. The heritability of activity traits measured in flies exposed to imidacloprid was higher than measured in controls and in these, courtship traits were genetically less correlated from mating success. Altogether, we did not observe a significant effect of the larval insecticide resistance status on adult behavioural traits, suggesting that selection for resistance in larvae does not involve repeatable behavioural changes in adults. This lack of correlation between larval resistance and adult behaviour also suggests that resistance at the larval stage does not necessarily result in increased behavioural resilience at a later life stage. These findings imply that selection for resistance in larvae as well as for behavioural resilience to sublethal exposure in adult will combine and impose a greater evolutionary constraint. Our conclusions further substantiate the need to encompass multiple trait measures and life stages in toxicological assays to properly assess the environmental impact of pesticides.     

Sub-lethal Effects of the Insecticides Pirimicarb and Dimethoate on the Aphid Parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) When Attacking and Developing in Insecticide-Resistant Hosts

The effectiveness of parasitoids as biological control agents can be constrained by insecticide use, not only through direct mortality but also as a result of sublethal effects. Several pest aphids have become resistant to a range of insecticides and a resistant strain of Myzus persicae was used in laboratory experiments to investigate sublethal effects of the insecticides pirimicarb and dimethoate on the parasitoid Diaeretiella rapae . Both insecticides produced sublethal effects on D. rapae when the parasitoid attacked and developed in aphids that had been dipped in insecticide solutions. Dimethoate affected oviposition behaviour; females were apparently repelled by residues on the surface of dipped aphids, thus reducing their attack rate and hence the number of mummies produced. Also, the reproductive performance of parasitoids that had developed in pirimicarb-dipped aphids appeared to be adversely affected, in comparison with parasitoids that emerged from uncontaminated hosts, and this was reflected both in lower mummy production and lower attack rates. Pirimicarb, but not dimethoate, affected the sex ratio of the offspring of D. rapae that had developed in dipped aphids, causing a significant increase in the proportion of males. This only occurred when the male parent had developed in a pirimicarb-dipped aphid, suggesting that the effect involves male sterility or mating behaviour, although they appeared to mate normally. These sublethal effects are potential constraints on the efficiency and effectiveness of D. rapae as a biological control agent of aphid pests, but to assess fully their potential impact further studies need to be done using more realistic extended laboratory and semi-field techniques.     

Development of resistance to the insecticide effect of juvenile hormone analog in Drosophila virilis: genetic and biochemical aspects

The development of resistance to the insecticide effect of juvenile hormone analogue (AJH-I) in Drosophila was studied. It is found that under the AJH-I treatment metamorphosis in D. virilis was delayed and some insects died. Selection of resistant flies was performed using sublethal dose of AJH-I (viability was 8%). The selection at such dose of AJH-I resulted in an increase in the proportion of resistant flies up to 30% already by the F3, whereafter is fluctuated within the range of 24-46% for further 12 generations. The increase in resistance to the lethal effect of AJH-I was also accompanied by an increase in resistance to its teratogenic effects. An analysis of the kinetics of selection has shown that the AJH-I resistance is controlled by more than one gene. It is established that the increase in resistance is associated with selection of individuals having high activity of juvenile hormone esterase.     

Assessment of Potential Sublethal Effects of Various Insecticides on Key Biological Traits of The Tobacco Whitefly,Bemisia tabaci

The tobacco whitefly Bemisia tabaci is one of the most devastating pests worldwide. Current management of B. tabaci relies upon the frequent applications of insecticides. In addition to direct mortality by typical acute toxicity (lethal effect), insecticides may also impair various key biological traits of the exposed insects through physiological and behavioral sublethal effects. Identifying and characterizing such effects could be crucial for understanding the global effects of insecticides on the pest and therefore for optimizing its management in the crops. We assessed the effects of sublethal and low-lethal concentrations of four widely used insecticides on the fecundity, honeydew excretion and feeding behavior of B. tabaci adults. The probing activity of the whiteflies feeding on treated cotton seedlings was recorded by an Electrical Penetration Graph (EPG). The results showed that imidacloprid and bifenthrin caused a reduction in phloem feeding even at sublethal concentrations. In addition, the honeydew excretions and fecundity levels of adults feeding on leaf discs treated with these concentrations were significantly lower than the untreated ones. While, sublethal concentrations of chlorpyrifos and carbosulfan did not affect feeding behavior, honeydew excretion and fecundity of the whitefly. We demonstrated an antifeedant effect of the imidacloprid and bifenthrin on B. tabaci, whereas behavioral changes in adults feeding on leaves treated with chlorpyrifos and carbosulfan were more likely caused by the direct effects of the insecticides on the insects'' nervous system itself. Our results show that aside from the lethal effect, the sublethal concentration of imidacloprid and bifenthrin impairs the phloem feeding, i.e. the most important feeding trait in a plant protection perspective. Indeed, this antifeedant property would give these insecticides potential to control insect pests indirectly. Therefore, the behavioral effects of sublethal concentrations of imidacloprid and bifenthrin may play an important role in the control of whitefly pests by increasing the toxicity persistence in treated crops.     

Effects of jasmonate-induced defenses in tomato on the potato aphid, Macrosiphum euphorbiae

Jasmonates such as jasmonic acid (JA) are plant‐signaling compounds that trigger induced resistance (IR) to a broad range of arthropod herbivores. JA‐dependent defenses are known to reduce the growth and survivorship of many chewing insects, but their impact on piercing–sucking insects such as aphids has not been extensively investigated. In this study, induced resistance was activated in tomato (Lycopersicon esculentum Mill) (Solanaceae) using a foliar application of synthetic JA, and control plants were treated with carrier solution. The life parameters of individual potato aphids and their progeny (Macrosiphum euphorbiae Thomas) (Hemiptera: Aphididae) were evaluated on the unsprayed leaves of plants in order to access the systemic effects of the foliar treatments. IR significantly reduced the longevity and net reproduction of adult aphids, as well as the percentage of juveniles to survive to maturity. These results indicate that JA application induces systemic defenses in tomato that have a direct negative impact on aphid survivorship. This study also examined aphid honeydew excretion, in order to evaluate the potential influence of induced resistance on aphid feeding behavior. The average honeydew production per aphid was comparable on plants with or without JA treatment, indicating that JA‐dependent defenses did not deter feeding. This suggests that the observed effects of JA on aphid survivorship were due to antibiotic rather than antixenotic factors. In addition to studying the effects of JA treatment on a tomato cultivar that is susceptible to aphids, this study also examined the effects of exogenous application of JA on tomato plants that carry the aphid resistance gene, Mi‐1.2. JA application did not significantly enhance or inhibit aphid control on resistant tomato. These findings expand our understanding of the effects of JA‐dependent defenses on piercing–sucking insects, and of the potential interactions between induced resistance and R‐gene mediated aphid resistance in tomato.     

蜚蠊灭菌肽的诱导及初步分离分析

昆虫经诱导盾产生灭菌肽的研究近年来已有很大进展,有关这方面的研究工作绝大多数都是以有翅亚纲内生翅类鳞翅目(主要是蚕类)昆虫和少数双翅目昆虫为材料.本文首次以有翅亚纲外生翅类蜚蠊目的美洲蜚蠊(Ptriplaneta americana L.)为实验昆虫,用Escherichia coil K₁₂ strain D₃₁作诱导源,对不同发育期、不同性别、不同成虫期的蜚蠊进行诱导后,采用含菌培养基平板测活方法,就存在个体数及能产生抗菌物质的个体数进行了初步的研究.发现成虫日龄在10天之内的雄性蜚蠊能够产生抗菌物质的个体百分比最高.抗菌物质出现的高峰期是在诱导后第三、四天.用滴滴涕和溴氰菊酯作诱导源对雄性蜚蠊的诱导实验表明,杀虫剂也能诱导蜚蠊产生抗菌物质,而且所诱导产生抗菌物质的活性强度(用抑菌圈直径表示)高于大肠杆菌所诱导的.滴滴涕和溴氰菊酯的重复诱导可提高蜚蠊产生抗菌物质个体百分比.蜚蠊经诱导后产生的抗菌物质具有广谱性,对苏云金杆菌、金黄色葡萄球菌、枯草杆菌及绿脓杆菌等有较强的抗菌活性,而对大肠杆菌D₃₁、大肠杆菌、粘质沙雷氏杆菌和溶壁微球菌等有较弱的抗菌活性.用肽类物质的指纹图谱法分离蜚蠊血淋巴抗菌物质,发现经诱导后血淋巴中确有新的肽类物质产生,该物质具抗菌活性,用DABITC法分析,其N-末端氨基酸为赖氨酸.     

Inter- and intra- species differences in plants as hosts to shape Tyria jacobaeae

The effects of sublethal doses of deltamethrin and propoxur, applied topically at LD10, LD30 and LD50 on German cockroaches, were studied by reciprocal crossing. Male and female longevities decreased curvilinearly with increasing sublethal doses of deltamethrin, and decreased linearly with increasing sublethal doses of propoxur. Fecundity of females treated with deltamethrin and propoxur was reduced with increasing sublethal doses of both insecticides. Oothecal production, oothecal hatchability and nymphal production also declined with increasing doses of deltamethrin and propoxur. Preoviposition and incubation periods were not affected by sublethal doses of deltamethrin and propoxur, although some significant differences were observed at certain oothecal numbers. Two-way analysis of variance indicated that only treated females showed an effect on oothecal production while oothecal hatch and nymphal production were governed by both treated females and males. Insecticide susceptibility tests on the progeny of parents treated with sublethal doses demonstrated that these doses did not increase insecticidal tolerance in the F1 generation.     

DDT resistance in Anopheles gambiae declines with mosquito age

Adult Anopheles gambiae Giles mosquitoes from Zanzibar were tested on a standard discriminating dose of DDT which reliably kills susceptible mosquitoes. Adults from wild-caught larvae reared in the laboratory, and from the F1 progeny of wild-caught adults, showed less than 5% test mortality when newly-emerged, but mortality rose with age to over 90% when they were 12-14 days old. Wild-caught mixed-age adults showed an intermediate mortality rate of 25%, close to the rate predicted from laboratory results for a fully resistant population with an age-structure typical of this species in natural conditions. It is inferred that older, genetically resistant insects may be scored as susceptible, so that routine susceptibility tests with wild-caught adults underestimate the frequency of resistance. In Zanzibar, such tests probably helped to persuade spraying authorities to continue spraying DDT in spite of resistance. Resistance which is restricted to younger insects may nonetheless reduce the effectiveness of spraying.     

Residues of chlorinated hydrocarbons in tissues of raptors in Florida

Dead or moribund raptors (n = 75) representing 11 species were collected between 1971 and 1981 from various locations in Florida. Samples of bran, muscle, liver and adipose tissue were analyzed for DDT, DDE, DDD, dieldrin, and PCB's. Detectable concentrations of DDT or its metabolites were found in 100% of all samples of muscle and liver, and 77% all samples of brain. Dieldrin was determined to be present in 91%, 93%, 87% and 78% of all samples of brain, muscle, liver and adipose tissue, respectively. Lethal or hazardous concentrations of dieldrin were found in brain samples from three birds, but DDT and PCB's were present at sublethal concentrations. When species were grouped according to their dietary habits, it was not possible to identify any trends in pesticide concentrations.     

Genetics and fitness costs of cyromazine resistance in the house fly (Diptera: Muscidae)

The genetic basis of cyromazine resistance was investigated in the house fly, Musca domestica L. The ED-R strain, which was collected in Mississippi and selected further in the laboratory, was 116.5-fold resistant compared with the laboratory susceptible strain, OR-S. The SEL strain, which was created by crossing ED-R with OR-S followed by three cycles of reselection and backcrossing to OR-S, was 84.7-fold resistant relative to the susceptible strain. Mortality data from reciprocal crosses of resistant and susceptible flies indicated that resistance was autosomal and not influenced by maternal effects. The relative position of probit lines from the parental strains and reciprocal crosses showed that resistance was expressed as an incompletely dominant trait with D = 0.30 and 0.32 for ED-R and SEL, respectively. To determine the number of genes involved, models of one, two, three, four, and five loci were used to compare observed and expected mortality of F1ED-R x susceptible backcross. Resistance was best described by a polygenic model of three loci when equal and additive effects of loci were assumed. Another approach, which was based on phenotypic variances, showed that nE, or the minimum number of freely segregating genetic factors for ED-R, equaled 3.07. ED-R showed greater reductions in fitness compared with SEL independent of the presence or absence of sublethal concentrations of cyromazine. These data suggested that reduced fitness was not due to deleterious pleiotropic effects of the resistance genes themselves but arose from other loci in the ED-R genotype.     

谷蠹和米象对磷化氢抗性遗传的研究

本文就谷蠹Rhyzopertha dominica 和米象Sitophilus oryzae对磷化氢的抗性遗传进行了研究,分别对两个种的实验室敏感品系和粮仓现场采集的抗性品系作为亲本进行杂交。同时测定了各自的亲本及其F₁杂种、F₁对抗性亲本回交和F2混交后代的剂量-死亡率反应曲线,并对它们的结果进行了遗传分析。结果指出,谷蠹和米象的F₁杂种对磷化氢的抗性遗传都为不完全隐性,各自的显性度(D)分别是-0.768和-0.348。同时F₁,回交和F₂混交的观察值和计算值之间的X²分析也表明,抗性表现为一个以上的常染色体因子遗传,但是主要是受隐性因子所控制。