Fertility Life Table Parameters Research Articles

Compatibility of pesticides with the predatory mite Neoseiulus barkeri.

Multiple arthropod pests can affect the same crop in agricultural systems, requiring the integration of control methods. In the present study, the effects of residual exposure to four broad-spectrum insecticides/acaricides (azadiractin, abamectin, chlorfenapyr, and fenpyroximate) on immature (development and survival time) and adult females (longevity, fecundity, and fertility life table parameters) of the predatory mite Neoseiulus barkeri were evaluated. Additionally, the insecticides/acaricides were categorized according to their selectivity based on the classification proposed by the International Organization for Biological Control (IOBC) for assessing the susceptibility of arthropods in laboratory experiments. Method 004, proposed by the Insecticide Resistance Action Committee (IRAC), was adopted for the bioassays with predators exposed to insecticide-acaricide residues. Among the insecticides/acaricides studied, azadirachtin had minimal effects on immature and adult N. barkeri (all non-significant) and was considered harmless based on the classification of toxicity according to the standards/categories proposed by the IOBC. All other insecticides/acaricides affected immature and adult N. barkeri and were considered slightly harmful in terms of toxicity, according to the IOBC.

Olfaction Response and Fertility Life Table Parameters of Tetrastichus howardi (Hymenoptera: Eulophidae) Parasitizing Plutella xylostella (Lepidoptera: Plutellidae) and the factitious host Tenebrio molitor (Coleoptera: Tenebrionidae).

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes the diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), but not much is known about its potential as a biocontrol agent. A rearing protocol has been established for this parasitoid on pupae of the factitious host Tenebrio molitor (L.) (Coleoptera: Tenebrionidae), with the aim of releasing it in the field to manage several lepidopteran species. The potential population growth of a parasitoid can be measured through fertility life tables and provide supporting information for using T. howardi in the management of P. xylostella. Also, the fitness and behavior of T. howardi reared on a factitious host can be indicators of its potential to control P. xylostella. Thus, in this study, the fertility life table parameters of T. howardi parasitizing P. xylostella were determined, as well as the effects of the natal host on the behavior of T. howardi towards host volatiles and parasitism rate. The results showed that net reproduction rate (Ro) and the intrinsic rate of population growth (rm) of T. howardi parasitizing P. xylostella were 13.6 (♀/♀) and 0.124 (♀/♀*day), respectively, whereas the mean generation time was 20.9days. Moreover, the natal host (T. molitor or P. xylostella) did not affect the fitness, parasitism rate, or olfactory response of T. howardi. In general, regardless of the natal host, parasitoid females responded to volatiles of both host species and exhibited the same rate of parasitism on P. xylostella. Therefore, T. howardi reared on the factitious host maintains its attraction and potential to parasitize P. xylostella, and can contribute to the biological control of this pest.

The complex II resistance mutation H258Y in succinate dehydrogenase subunit B causes fitness penalties associated with mitochondrial respiratory deficiency.

The acaricides cyflumetofen, cyenopyrafen and pyflubumide inhibit the mitochondrial electron transport chain at complex II [succinate dehydrogenase (SDH) complex]. A target site mutation H258Y was recently discovered in a resistant strain of the spider mite pest Tetranychus urticae. H258Y causes strong cross-resistance between cyenopyrafen and pyflubumide, but not cyflumetofen. In fungal pests, fitness costs associated with substitutions at the corresponding H258 position that confer resistance to fungicidal SDH inhibitors have not been uncovered. Here, we used H258 and Y258 near-isogenic lines of T. urticae to quantify potential pleiotropic fitness effects on mite physiology. The H258Y mutation was not associated with consistent significant changes of single generation life history traits and fertility life table parameters. In contrast, proportional Sanger sequencing and droplet digital polymerase chain reaction showed that the frequency of the resistant Y258 allele decreased when replicated 50:50 Y258:H258 experimentally evolving populations were maintained in an acaricide-free environment for approximately 12 generations. Using in vitro assays with mitochondrial extracts from resistant (Y258) and susceptible (H258) lines, we identified a significantly reduced SDH activity (48% lower activity) and a slightly enhanced combined complex I and III activity (18% higher activity) in the Y258 lines. Our findings suggest that the H258Y mutation is associated with a high fitness cost in the spider mite T. urticae. Importantly, while it is the most common approach, it is clear that only comparing life history traits and life table fecundity does not allow to reliably estimate fitness costs of target site mutations in natural pest populations. © 2023 Society of Chemical Industry.

Biology and life table of Tetranychus neocaledonicus André (1933) (Acari: Tetranychidae) in different hosts

Tetranychus neocaledonicus colonizes both cultivated and spontaneous plants. Species such as Phaseolus lunatus, Vigna unguiculata, Abelmoschus esculentus, and Glycine max are listed as hosts to T. neocaledonicus. However, very little is known about the bioecological aspects of this host-T. neocaledonicus interaction. The present study aims to determine the biological aspects (development and survival of immature individuals, reproduction, and fertility life table parameters) of T. neocaledonicus in P. lunatus, V. unguiculata, A. esculentus, and G. max. Individuals of T. neocaledonicus multiplied in laboratory were used on plants of P. lunatus to establish the experiments. To evaluate biological and reproductive parameters, three daily assessments were performed during the immature stages and one assessment during the adult stage. The mean developmental time from egg to adult was recorded. The highest mean was observed in V. unguiculata (13.57 days). Tetranychus neocaledonicus showed the highest fecundity in V. unguiculata, G. max and P. lunatus: 93.75, 93.38, and 79.10 eggs/female and longevity of 43.78, 33.42, and 47.26 days, respectively. Survival rate was above 50% until the 50th day in P. lunatus, 65th day in G. max and V. unguiculata, and 40th day in A. esculentus. The hosts G. max and V. unguiculata provided the highest net reproduction rates (R0) for T. neocaledonicus. The intrinsic rate of increase rm was lower when mites parasitized V. unguiculata and A. esculentus. This also happened for the finite rate of increase (λ). Host plants affect the performance and the biological, population, and reproductive parameters of T. neocaledonicus. Glycine max is the most favorable host for the development and reproduction of T. neocaledonicus.

Lethal and sublethal effects of synthetic and bio-insecticides on Trichogramma brassicae parasitizing Tuta absoluta.

The tomato leaf miner (TLM), Tuta absoluta (Meyrick), is an invasive tomato pest found worldwide. Sustainable control strategies aimed at increasing biological control approaches and decreasing chemical inputs are required, due to the tendency to develop insecticide resistance. In this study, the lethal and sublethal effects of four chemical insecticides (abamectin, indoxacarb, chlorantraniliprole, and spinosad) and the sublethal effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) on a widespread TLM egg parasitoid, Trichogramma brassicae Bezdenko, were estimated. Concentration mortality response bioassays enabled the estimation of lethal concentrations of the tested insecticides for the parasitoids, with chlorantraniliprole having the lowest LC50 and indoxacarb the highest. The LC25 and LC50 of the tested insecticides on the TLM were sprayed on eggs and then offered at three time intervals to the parasitoids. The fertility and other life table parameters of the individuals emerging from the treated eggs were estimated. All of the chemical insecticides, but not the fungus, had harmful effects on T. brassicae. The insecticide applications caused a 3.84–5.17 times reduction in the net reproductive rate (R0) compared with the control. No parameters were affected by spraying the fungus in the 0h treatment, but effects were recorded at 24 and/or 48h, except for the gross reproduction rate (GRR). The value of the intrinsic rate of increase (rm) also decreased to 0.528–0.617 after the insecticide treatments. The doubling time (DT) increased in all treatments compared to the control. Nevertheless, the generation time (T) was only very slightly affected. In addition, in the combination experiments, M. anisopliae showed a remarkable synergism with T. brassicae in controlling TLM eggs. These results indicate that low levels of lethal effects on key biological control agents should be considered in the choice of insecticides to be included in sustainable TLM control packages.

Effects of Delayed Mating on the Reproductive Performance of Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae).

Simple SummaryIn many Asian countries, Henosepilachna vigintioctopunctata (F.), is seriously harmful to Solanaceae vegetables. With the popularization of green agriculture and the improvement in people’s living standards, biological pest control may become the mainstream. The artificial release of sex pheromones and other methods to delay insect mating, thus affecting population abundance, is an important part of biological control. We took H. vigintioctopunctata collected from Jingzhou, Hubei Province, China, back to the laboratory to establish an experimental population to study the effect of delayed mating on its reproductive behavior. The negative effects on reproduction and changes in population life table parameters, such as net reproductive rate, intrinsic and finite rates of increase, doubling time, and mean generation time, could be estimated by the treatment of delayed mating of males and females, which could be useful for providing important information for pest control in the future.Henosepilachna vigintioctopunctata (F.) is a serious pest of numerous solanaceous crops in many Asian countries. The purpose of this study was to clarify the effects of delayed mating on mating success, fecundity, fertility, pre-oviposition period, oviposition period, adult longevity, and population life table parameters (including net reproductive rate, intrinsic and finite rates of increase, doubling time, and mean generation time) of H. vigintioctopunctata. Beginning three days after emergence for both sexes, mating was delayed an additional 0, 2, 4, 6, or 8 days. We compared the data when mating was delayed for males only with the data when mating was similarly delayed for females only. Reproductive and life table parameters were calculated from the two data sets and compared. The results showed that the preoviposition and oviposition period of adults was significantly reduced by delayed mating, while the preoviposition period was not significantly different in adults mated at older ages. The mating success rate, fecundity, and proportion of hatching eggs decreased with increasing mating age. Longevity was not affected by the age at mating. Mating delay also affected the life table parameters of H. vigintioctopunctata, with a similar trend observed in the net reproductive rate and intrinsic and finite rates of increase, all of which decreased gradually as the number of delay days increased. The population doubling time increased with increases in mating age. The results also showed that delayed mating was an effective measure to consider in controlling H. vigintioctopunctata. It is hoped that our data will provide a scientific basis and contribute technical guidance for forecasting and integrated management of this pest.

Fitness Cost of Chlorpyrifos Resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) on Different Host Plants.

Spodoptera frugiperda (J. E. Smith, 1797) is a polyphagous pest of global relevance due to the damage it inflicts on agricultural crops. In South American countries, this species is one of the principal pests of maize and cotton. Currently, S. frugiperda is also emerging as an important pest of soybeans and winter cereals in Brazil. Chemical control is one of the main control tactics against S. frugiperda, even though resistance against numerous modes of action insecticides has been reported. To support insect resistance management programs, we evaluated the fitness costs of resistance of S. frugiperda to the acetylcholinesterase inhibitor chlorpyrifos. Fitness costs were quantified by comparing biological parameters of chlorpyrifos-resistant and -susceptible S. frugiperda and their F1 hybrids (heterozygotes) on non-Bt cotton, non-Bt maize, non-Bt soybean, and oats. The results revealed that the chlorpyrifos-resistant genotype showed lower pupa-to-adult and egg-to-adult survivorship and reduced larval weights on oats; longer neonate-to-pupa and egg-to-adult developmental periods, and lower pupal weights and fecundity on maize; lower pupal weights on soybean; and reduced fecundity on cotton compared with the chlorpyrifos-susceptible genotype. Fitness costs also affected fertility life table parameters of the resistant genotype, increasing the mean length of a generation on cotton and maize and reducing the potential for population growth on all hosts. These findings suggest fitness costs at the individual and population levels of chlorpyrifos resistance in S. frugiperda, indicating that removal of the selective agent from the environment would result in reduced resistance and opportunities for the restoration of susceptibility.

Insecticide Rotation and Adaptive Fitness Cost Underlying Insecticide Resistance Management for Spodoptera frugiperda (Lepidoptera: Noctuidae).

Rotation of insecticide modes of action is recommended to delay selection for insecticide resistance. In this study, larvae of Spodoptera frugiperda (J.E. Smith) were exposed alternately to spinetoram and metaflumizone with insecticidal and biological response determined. Five generations (G) were evaluated with at least 200 larvae assayed per treatment. The experiment consisted of rearing field-collected and untreated larvae (M-Control), larvae with successive applications of either metaflumizone (M-MET) or spinetoram (M-SPI), and alternation of these insecticides (M-Rotation treatment) consisting of the following treatments: G2 = exposure to SPI, G3 = exposure to MET, G4 = exposure to SPI, G5 = exposure to MET, and G6 = exposure to SPI. Four days after application, those surviving larvae were used to compose the following generations. In the G7, evaluations were made on the selected populations M-MET, M-SPI, M-Rotation, and control larvae to determine biological characteristics used to calculate the fertility life table parameters and further comparisons across treatments. The frequency of resistance was increased at rate of 49.5% and 29.2% after five generations of selection pressure with MET and SPI, respectively. However, rotation of insecticides reduced the frequency of resistance about 50% over the generations. Individuals originated from successive exposures to the insecticides exhibited delayed egg incubation, greater percentage of pupae with deformation, longer larval and pupal periods, and reduction in emergence rate and longevity of adults, suggesting adaptive costs associated with resistance.

Cross-crop resistance of Spodoptera frugiperda selected on Bt maize to genetically-modified soybean expressing Cry1Ac and Cry1F proteins in Brazil

Spodoptera frugiperda is one of the main pests of maize and cotton in Brazil and has increased its occurrence on soybean. Field-evolved resistance of this species to Cry1 Bacillus thuringiensis (Bt) proteins expressed in maize has been characterized in Brazil, Argentina, Puerto Rico and southeastern U.S. Here, we conducted studies to evaluate the survival and development of S. frugiperda strains that are susceptible, selected for resistance to Bt-maize single (Cry1F) or pyramided (Cry1F/Cry1A.105/Cry2Ab2) events and F1 hybrids of the selected and susceptible strains (heterozygotes) on DAS-444Ø6-6 × DAS-81419-2 soybean with tolerance to 2,4-d, glyphosate and ammonium glufosinate herbicides (event DAS-444Ø6-6) and insect-resistant due to expression of Cry1Ac and Cry1F Bt proteins (event DAS-81419-2). Susceptible insects of S. frugiperda did not survive on Cry1Ac/Cry1F-soybean. However, homozygous-resistant and heterozygous insects were able to survive and emerge as fertile adults when fed on Cry1Ac/Cry1F-soybean, suggesting that the resistance is partially recessive. Life history studies revealed that homozygous-resistant insects had similar development, reproductive performance, net reproductive rate, intrinsic and finite rates of population increase on Cry1Ac/Cry1F-soybean and non-Bt soybean. In contrast, heterozygotes had their fertility life table parameters significantly reduced on Cry1Ac/Cry1F-soybean. Therefore, the selection of S. frugiperda for resistance to single and pyramided Bt maize can result in cross-crop resistance to DAS-444Ø6-6 × DAS-81419-2 soybean. The importance of these results to integrated pest management (IPM) and insect resistance management (IRM) programs is discussed.

Effect of biofertilizers and Verticillium lecanii (Zimm.) Viégas applied to Canavalia ensiformis L. (Fabaceae) on the bioecology of Brevipalpus phoenicis (Acari: Tenuipalpidae)

Two assays were conducted to evaluate the effect of biofertilizer suspensions applied to Canavalia ensiformis (L.) DC. plants on Brevipalpus phoenicis (Geijskes) bioecology. In the first assay (residual effect), the following treatments were tested: a) Distilled water (Control); b) Biofert - biofertilizer produced in a single bioreactor; c) Biomix – a mix of biofertilizers produced in four bioreactors; and d) Bio+VL - Biofert + Verticillium lecaniiI (Zimm.) Viégas. In the second assay (systemic effect) only two suspensions were tested: a) Biofert and b) Distilled water (control). In the first assay, the biofertilizer was applied once on the whole plant and mites were confined in arenas on both leaflets. In the second assay, the plants were sprayed weekly only in one leaflet and the mites were confined in arenas on the non-sprayed leaflet. In both bioassays, bioecological parameters related to survival and oviposition were evaluated. The biofertilizer effects on potential population growth during the first generation were measured by fertility life table parameters (net reproductive rate (Ro), mean generation time (T), doubling time (DT), intrinsic rate of increase (Rm) and finite rate of increase (). The biofertilizer had adverse effects on both survival and oviposition parameters. The net reproduction rates (Ro) were of 18.1; 12.9; 12.5 and 10.5 females/female (assay I) and 19.4 and 13.0 females/female (assay II), respectively for the treatments in the above-mentioned orders. These results show that the biofertilizer reduced the potential population growth of B. phoenicis in either residual or systemic effect assays.

Resistance of Lima Bean (Phaseolus lunatus L.) to the Red Spider Mite Tetranychus neocaledonicus (Acari: Tetranychidae).

The red spider mite, Tetranychus neocaledonicus (Acari: Tetranychidae) can be an important pest on lima bean (Phaseolus lunatus L.). Thus, the objective of this work was to assess the antibiosis and antixenosis effects of lima bean genotypes on T. neocaledonicus, through the evaluation of performance parameters as well as the host preference for food and oviposition. Nine lima bean genotypes from the Active Bank of Germplasm of the Federal University of Piauí – BGP / UFPI were screened. To assess antibiosis parameters, eggs of T. neocaledonicus were individually placed on leaf disks of each genotype. The period and survival of the different stages of development (larvae, protonymph, deutonymph and adult), pre-oviposition, oviposition and post-oviposition period, longevity and fecundity of females were evaluated, and fertility life table parameters were calculated. In choice tests, adult females of T. neocaledonicus were used. The numbers of mites and eggs were counted for each genotype. The protonymph, egg-adult, longevity and oviposition period, fertility life table parameters, as well as the food and oviposition preference were affected by lima bean genotypes. We found that some genotypes reduced adult female longevity, increased the larval and egg-adult period, decreased oviposition period, negatively affected the fertility life table parameters, reducing the net reproductive rate (Ro), the intrinsic rate of increase (rm) and the finite rate of increase (λ), while increasing the population doubling time (DT), exhibiting a reliable antibiosis effect upon T. neocaledonicus. Nevertheless, these same genotypes were the most preferred for food and oviposition. By contrast, some other genotypes reduced the adult female longevity and oviposition period, elongated the larval period and affected fertility life table parameters, demonstrating an antibiosis effect upon T. neocaledonicus. Moreover, these other genotypes were among the less preferred for food and oviposition, exhibiting an additional antixenosis effect. Thus, our results demonstrate that the genotypes of lima bean may present distinct levels of resistance to T. neocaledonicus, and this resistance may be an important tool for Integrated Pest Management. This is one of the first studies aiming to describe mite resistance sources in lima bean.

Effects of different diets on biological parameters of the predatory mite Amblyseius swirskii (Acari: Phytoseiidae)

ABSTRACTThe predatory mite, Amblyseius swirskii Athias-Henriot is one of the natural enemies of agricultural pests such as the spider mite, Tetranychus urticae (Koch). Pollen, as a food supplement or alternative food source, has a considerable impact on the efficiency of the predatory mite in the biological control programme. In this study, the effect of six distinct diets (one consisting solely of the eggs of T. urticae and the others being pollen of apricot, soybean, sesame, walnut, and date, each mixed with the eggs of T. urticae) on the biological parameters of A. Swirskii was studied. Development from egg to adult, oviposition day, and daily mortality were investigated in 65 replications for each type of food. The results demonstrated that A. swirskii was able to adapt to each of the six tested diets and growth development was considerable with each. Comparisons of the biological parameters among these diets showed that the average generation length, from egg to adult, had significant differences at the 5% level. The fertility life table parameters showed no significant differences between treatments for rm (the rate at which a population increases in size in the absence of density-dependent forces impacting the population)‚ λ (sustained increase in population in one day compared to the previous day), and R0 (number of progeny of the substituted females per person in one generation). The results showed that the oviposition and survival times of A. swirskii were greatly enhanced by the pollen diets so that a much greater efficiency of this predatory mite in biological control programmes was achieved.

Behavioral and Biological Effects of Exposure to Tuta absoluta (Lepidoptera: Gelechiidae) Sex Pheromone on Several Trichogramma (Hymenoptera: Trichogrammatidae) Populations.

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of tomato worldwide. Biological control of the pest using Trichogramma (Hymenoptera: Trichogrammatidae) wasps can be combined with other practices such as use of synthetic sex pheromones for mating disruption or mass trapping programs. In this study, effects of T. absoluta sex pheromone on behavioral responses and fertility life table parameters of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae), Wolbachia-uninfected (W-) Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae), and Wolbachia-infected (W+) T. brassicae were investigated under laboratory conditions. Female wasps of T. evanescens and T. brassicae (W+) were attracted to the pest synthetic sex pheromone (around 62%) and calling virgin female moths (around 75%) and their responses were affected by the wasp age and temperature. Exposure to the host synthetic sex pheromone significantly reduced the percentage of adult emergence, longevity, and fecundity of female wasps, as well as the time spent to find a mate and duration of mating. However, tested populations were not affected similarly. Despite the laboratory tests, greenhouse experiments showed that the wasps were not caught in the traps baited with T. absoluta synthetic sex pheromone. Complementary studies are needed to precisely determine possible interference between pheromone application and releasing Trichogramma Westwood (Hymenoptera: Trichogrammatidae) wasps to achieve a successful integrated control of T. absoluta.

Fitness costs of key point mutations that underlie acaricide target-site resistance in the two-spotted spider mite Tetranychus urticae.

The frequency of insecticide/acaricide target‐site resistance is increasing in arthropod pest populations and is typically underpinned by single point mutations that affect the binding strength between the insecticide/acaricide and its target‐site. Theory predicts that although resistance mutations clearly have advantageous effects under the selection pressure of the insecticide/acaricide, they might convey negative pleiotropic effects on other aspects of fitness. If such fitness costs are in place, target‐site resistance is thus likely to disappear in the absence of insecticide/acaricide treatment, a process that would counteract the spread of resistance in agricultural crops. Hence, there is a great need to reliably quantify the various potential pleiotropic effects of target‐site resistance point mutations on arthropod fitness. Here, we used near‐isogenic lines of the spider mite pest Tetranychus urticae that carry well‐characterized acaricide target‐site resistance mutations to quantify potential fitness costs. Specifically, we analyzed P262T in the mitochondrial cytochrome b, the combined G314D and G326E substitutions in the glutamate‐gated chloride channels, L1024V in the voltage‐gated sodium channel, and I1017F in chitin synthase 1. Five fertility life table parameters and nine single‐generation life‐history traits were quantified and compared across a total of 15 mite lines. In addition, we monitored the temporal resistance level dynamics of populations with different starting frequency levels of the chitin synthase resistant allele to further support our findings. Three target‐site resistance mutations, I1017F and the co‐occurring G314D and G326E mutations, were shown to significantly and consistently alter certain fitness parameters in T. urticae. The other two mutations (P262T and L1024V) did not result in any consistent change in a fitness parameter analyzed in our study. Our findings are discussed in the context of the global spread of T. urticae pesticide resistance and integrated pest management.

Susceptibility, Oviposition Preference, and Biology of Grapholita molesta (Lepidoptera: Tortricidae) in Prunus Spp. Rootstock Genotypes

Studying the susceptibility of peach trees to Grapholita molesta (Busck) is one of the major steps in the development of pest-resistant peach varieties. This work evaluated the susceptibility of 55 genotypes of the "Prunus Rootstock Collection" ("Coleção Porta-enxerto de Prunus") of Embrapa Temperate Climate (Pelotas, Rio Grande do Sul, Brazil) to the natural infestation of G. molesta, assessed the oviposition preference of G. molesta in choice and no-choice bioassays, and estimated the biological parameters and the fertility life table on different Prunus spp. genotypes in the laboratory. Genotypes Prunus kansuensis (Rehder), I-67-52-9, and I-67-52-4 were the most susceptible to G. molesta infestation in the field (>60% of branches infested), while 'Sharpe' (Prunus angustifolia x Prunus spp.) and Prunus sellowii (Koehne) were the least infested (0% of branches infested). In choice and no-choice bioassays, G. molesta preferred to oviposit on P. kansuensis when compared with Sharpe. The Sharpe genotype also showed an antibiosis effect, resulting in negative effects on the fertility life table parameters when compared with the genotypes P. kansuensis and 'Capdeboscq.' The results found in the present study can provide information to initiate a long-term breeding program moving desired G. molesta resistance traits from the rootstock into the Prunus spp. cultivars.

Life table of the red spider mite Tetranychus bastosi (Acari: Tetranychidae) on different host plants

Tetranychus bastosi Tuttle, Baker and Sales was described from Ceará state, northeastern Brazil. It has so far been reported from 25 plant species, among which cassava (Manihot esculenta Crants), common bean (Phaseolus vulgaris L.) and papaya (Carica papaya L). Although there is no information about its impact on crop yield, high population levels have been observed on some crops, leading to suppose that damage might occur in some occasions. In this study, fertility life table parameters were calculated for T. bastosi on cassava, common bean and papaya at 25 ± 2 °C, 70 ± 5% RH and photoperiod of 12/12 h. The best performance of T. bastosi occurred on C. papaya and P. vulgaris, on which the intrinsic rate of population increase reached 0.184 and 0.183 female/female/day, respectively. These results agree with the most common occurrence of this mite on papaya and on common bean than on cassava.

Performance of Eriopis connexa (Coleoptera: Coccinellidae) resistant to lambda-cyhalothrin after extended recovery from knockdown.

A population of the predatory lady beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae) was recorded as resistant to lambda-cyhalothrin. Adults exposed to this insecticide have recovered from knockdown after 72h. Thus, the performance of resistant (R) and susceptible (S) populations of E. connexa not exposed to insecticide (R0 and S0) and R adults recovering from knockdown 24, 48, and 72h after exposure (R24, R48, and R72) was studied. In addition, the fertility life table parameters were calculated for one generation considering the progenies from R0, S0, and R24 populations. The recovery rate from knockdown was 69.4% for R-adults, and greater recovery rate was observed within 48h following lambda-cyhalothrin exposure. The S-females produced about 50% more eggs and lived longer, when compared with R-females irrespective of the recovery periods after knockdown. The R-females produced similar number of eggs and exhibited similar longevity across all treatments (R0, R24, R48, and R72). Progenies produced by R- and S-populations did not exhibit consistent differences in development and survival. The fertility life table parameters showed higher intrinsic rate of population growth (rm) and lower mean generation time (T) for R0- and R24-females, when compared with those for S0-females. Thus, the time interval needed to recover from knockdown is not related to the adaptive cost of resistance in E. connexa.

Life table of Orius insidiosus (Hemiptera: Anthocoridae) feeding on Sitotroga cerealella (Lepidoptera: Gelechiidae) eggs

To use a natural enemy to control an insect pest, it is important to determine the biological parameters of the native populations of the predator. The goal of this study was determinate the biological parameters of O. insidiosus fed on Sitotroga cerealella eggs. A batch of 225 O. insidiosus eggs were laid into bean pods. The bean pods were kept in glass jars, and the eggs and first instar nymphs were counted daily. All nymphs were extracted and individualized in Petri dishes. The presence/absence of exuvie was observed daily as a way to assess the emergence of adults from the nymphal stage. Seventeen adult couples were placed into Petri dishes with a segment of bean pod. The bean pod segments were extracted and replaced daily, counting the number of eggs present on the pods. The life cycle, survival percentage, sex ratio, male/female longevity, pre ovoposition, ovoposition and post ovoposition periods were determined. Finally, fertility life table parameters were estimated. The nymphal development time was 12.0 ± 0.22 days, with 80.47 % ± 3.23 survival, while the total development time was 15.0 ± 0.23 days, with 66.67 % ± 1.90 survival. Of the total adults that emerged, 30.95 % ± 2.38 were females. The female sex ratio was 0.75, and the oviposition period was 0.86 ± 9.21 days with a total fertility of 60.29 ± 7.39 eggs. The data estimated from the fertility life table were: Ro: 28.26, rm: 0.14, T: 24.26, λ: 1.13 and DT: 5.01.

Efeito de Bacillus thuringiensis nas características biológicas do predador Orius insidiosus Say (Hemiptera: Anthocoridae) alimentado com ovos de Plutella xylostella L. (Lepidopteta: Plutellidae)

A traça-das-crucíferas, Plutella xylostella (L.) (Lepidoptera: Plutellidae), é considerada uma das pragas mais importantes de brassicáceas (Brassicaceae) em todo o mundo. A praga ocorre todos os anos no Brasil, onde o seu manejo é feito principalmente com controle químico por causa de sua conveniência e rápida ação inicial. O uso indiscriminado de inseticidas afeta organismos não-alvo e tem sido associado com o aumento da resistência de populações de P. xylostella. Estas preocupações despertaram o interesse para o uso de outras estratégias de controle, que incluem o uso de microrganismos entomopatogênicos como Bacillus thuringiensis Berliner e do predador Orius insidiosus (Say) (Hemiptera: Anthocoridae). O objetivo foi avaliar o efeito de B. thuringiensis (B. thuringiensis aizawai GC 91, Agree®) nas características biológicas de O. insidiosus. Os predadores foram alimentados com ovos de P. xylostella tratados com água destilada (controle) ou com suspensão de B. thuringiensis (0,7 g/0,5 L). Os seguintes aspectos biológicos foram avaliados: duração, sobrevivência e consumo durante o período ninfal; e consumo, número de ovos por fêmea e viabilidade de ovos durante a fase adulta. Os parâmetros de tabela de vida de fertilidade também foram avaliados para os tratamentos com ovos tratados e não tratados com B. thuringiensis. Os resultados mostraram que dentre os parâmetros de O. insidiosus a duração de ninfas de segundo ínstar, consumo ninfal e longevidade de fêmeas foram afetados pela presença de B. thuringiensis nos ovos tratados. Fêmeas alimentadas com ovos tratados mostraram menor número da progênie, que consequentemente levou a uma menor taxa de crescimento populacional.

The impact of cucumber nitrogen nutrition on life history traits of Tetranychus urticae (Koch) (Acari: Tetranychidae)

The nutritional quality of the host plant is one of the most important factors of growth and reproduction for crop pests. In order to investigate the impact of nitrogen on the biology and demography of Tetranychus urticae Koch (Acari: Tetranychidae), cucumber plants were nourished by four levels of nitrogen: N1 (10 meq /L NO3-), N2 (12 meq/L NO3-), N3 (15 meq/L NO3-) and N4 (20 meq /L NO3-). The experiments were performed under laboratory conditions at 25+/-1 °C, 60+/-5 % RH and a photoperiod of 16:8 (L:D) hours. Based on the results, increasing nitrogen nutriment was associated with a diminution of pre-imaginal duration in female mites from 13.13 to 10.74 days. In the opposite direction, the population reared on nitrogen-deficient cucumbers exhibited the highest rates of net fecundity (36.79 eggs/female) and net fertility (27.22 eggs/female). However, no considerable variation was demonstrated in fertility life-table parameters. The greatest net reproductive rate (R0) was observed when using the deficient (N1) nitrogen solution (22.12 females/female/generation). Additionally, the intrinsic rate of natural increase (rm) was estimated to be 0.178, 0.171, 0.183 and 0.185 females/female/day on cucumbers which were nourished by 10 to 20 meq/L NO3-, respectively. Finally, the mean population doubling time (DT) ranged from 3.72 to 4.04 days, and was at a minimum with the excess (N4) nitrogen solution and at a maximum with the moderately deficient (N2) treatment