Adult Female Fecundity Research Articles

Effect of Larval Nutritional Regimes on Morphometry and Vectorial Capacity of Aedes aegypti for Dengue Transmission.

Background Nutritional level in larval diet of mosquito vectors influence on life history traits and vectorial capacity (VC). Therefore, the present study was carried out to assess the effect of larval diet concentration on vector bionomic and VC of Aedes aegypti in Sri Lanka. Method Three batches of 400 Ae. aegypti larvae (first instar) were reared under different concentrations of larval diet (6%, 8%, and 10%; Volume/Volume), which was prepared by mixing 12.5 g of tuna meal, 9.0 g of bovine liver powder, and 3.5 g of Brewer's yeast, in 100 ml of distilled water. The effect of larval diet concentration on different morphometric and functional parameters of larvae (length and width of head, abdomen, survival rate, and pupation success), pupae (length and width of cephalothorax, survival rate, and adult emersion), adult (length and width of thorax, abdomen, survival rate, longevity, biting frequency and fecundity of adults) were examined. In addition, VC of Ae. aegypti was evaluated. The General Linear Model (GLM) was used for the statistical analysis. Results Larval head length, head width, thoracic width, abdominal length, abdominal width, total length, and survival rate significantly increased with higher doses of larval diet (P < 0.05). In case of pupae, length, and width of cephalothorax, survival rate and adult emergence rate denoted an increasing trend with the elevated larval diets. However, the variations of survival rate and adult emergence rate were statistically significant (P < 0.05). In adults, all morphometric parameters (thoracic length, abdominal length, abdominal width, and wing length) significantly increased with elevating larval diets levels (except for thoracic width) along with the biting frequency, fecundity, and survival rate (P < 0.05) of adult females. The VC also denoted significant variations (F4,14 = 24.048; P < 0.05) with the larval diet concentration, whereby the highest VC of 196.37 was observed at 10% treatment. Conclusion Larval food availability has a significant influence on the adult fitness and thus may affect the incidence of dengue due to variations in the VC of Ae.

Lethal and sublethal effects of fluralaner on the two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae).

Two-spotted spider mite (TSSM), Tetranychus urticae Koch is a serious agricultural pest and has developed high levels of resistance to many acaricides. Hence, screening new acaricides is important in the control of TSSM. Fluralaner, a novel isoxazoline, has high activity against agricultural and ectoparasitic pests; however, little information is available about its effects on agricultural mites. Lethal and sublethal effects of fluralaner towards TSSM eggs and female adults were therefore evaluated in this study. Fluralaner exhibited higher activity towards TSSM female adults (LC50 , 0.49 mg L-1 ) compared with commercial acaricides including fenpyroximate, pyridaben and hexythiazox, and also excellent activity towards eggs (LC50 , 0.36 mg L-1 ). The results of a sublethal effect study showed a significant reduction in the duration and fecundity of female adults with increases in the tested concentrations. The net reproductive rate (R0 ) decreased to 67.34 ± 3.96 and 50.29 ± 3.40 offspring per individual in LC10 and LC30 treatments compared with control (108.31 ± 7.61 offspring per individual). The intrinsic rate of increase (r) and finite rate of increase (λ) in the controls (0.30 and 1.36 d-1 ) were significantly higher than in the LC30 treatment (0.25 and 1.29 d-1 ); whereas, they were almost identical to values for the LC10 treatment. No change in mean generation time (T) was observed at sublethal concentrations treatments. Our results demonstrated that fluralaner has high acaricidal activity and could be considered a potential acaricide for TSSM management. © 2019 Society of Chemical Industry.

Insecticidal, Behavioral and Biological Effects of Chlorantraniliprole and Chlorfluazuron on Cotton Leafworm (Spodoptera littoralis).

The cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae) is the most destructive pests and causing a great loss for several vegetables and field crops. So, the present study was aimed to evaluate and compare the effects of chlorantraniliprole and chlorfluazuron on certain behavioral and biological aspects of S. littoralis at different stages. Under laboratory conditions, the toxicity of chlorantraniliprole and chlorfluazuron against the egg masses, 2nd and 4th larval instars of S. littoralis were evaluated. The impact of tested insecticides on the feeding, oviposition of females and biological aspects of S. littoralis was also carried out. Overall, chlorfluazuron was more toxic than chlorantraniliprole. According to repellency index (RI %), tested insecticides have a repulsive effect for the feeding of 2nd and 4th larval instars as well as for oviposition of females. Sublethal concentrations significantly reduced larval and pupal weight, adult survival, percent of pupation and adult emergence, female fecundity, fertility percentage, weight and protein content of ovaries. While, larval and pupal durations were increased. It was concluded that chlorantraniliprole and chlorfluazuron have insecticidal, behavioral and biological effects on S. littoralis stages and may be used as alternatives to conventional insecticides in IPM programs.

The maternal effects of heat shock on biological parameters and ovaries of Frankliniella occidentalis (Thysanoptera: Thripidae)

Maternal effects of heat shock are reported for some species of insects, but little is known about such effects in the western flower thrips (WFT) Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). WFT is a pest of vegetables in greenhouses worldwide. It is susceptible to high temperatures in its natural environment and is controlled using heat treatment in China. WFT population growth is suppressed by a brief exposure to a high temperature of 40°C or 45°C in the laboratory. To explore the mechanism by which high temperatures suppress the growth of WFT populations, as well as the effects of multiple heat treatments on WFT, we recorded the duration of development and survival of immature WFT, and the sex ratio (female/male) and fecundity of F1, F2, F3 and F4 adult females that developed after a single heat shock, and those of F2 offspring after a double heat shock. We also recorded the longevity and ovarian structure of adult females of the treated generation (P) and their F1, F2 and F3 offspring after a single heat shock. In addition, we determined whether the effects of a heat shock on second instar nymphs and adults differed. The results indicate that exposure of the parental generation to 41°C or 45°C for 2 h significantly prolonged the duration of development, reduced survival of immature WFT and altered the sex ratio (female/male), longevity and fertility of their adult female offspring. The effects of a heat shock of 41°C persisted for two generations, whilst the effect of heat shock of 45°C persisted for three generations. In addition, double heat shocks had more pronounced effects than a single heat shock. Heat shock administered to second instar nymphs resulted in a decrease in the number of ovarioles, whilst a heat shock administered to adults resulted in ovariole deformity. The maternal effects of heat shock in terms of the biological parameters of WFT, structure and number of ovarioles, are critical in determining the suppression of the growth at high temperatures of WFT populations.

PREY CONSUMPTION AND FECUNDITY OF Phytoseiulus persimilis ATHIAS-HENRIOT FED ON DIFFERENT STAGES AND DENSITIES OF Tetranychus urticae Koch. (ACARI: PHYTOSEIIDAE: TETRANYCHIDAE) UNDER LABORATORY CONDITIONS

The effect of different prey densities and prey stages of Tetranychus urticae onfeeding capacity and fecundity of Phytoseiulus persimilis adult females was studied on leaf discs ofeggplant, Solanum melongena L. (Black Baladi cultivar) during ten days under laboratory consistentconditions of 25 ± 2°C and 65 ± 2% R.H.. The following prey densities were tested: 5, 10, 15 and 20for the tested stages of prey (eggs, larvae, males and females). It was found that all of the prey testedstages were eaten by P. persimilis females. The total average of devoured prey individuals perpredator female during ten days was significantly (P ≤ 0.05) affected by stage and density of theintroduced prey. In all cases, number of preys consumed by predator was increased with increasingprey density. P. persimilis consumed more eggs and larvae than males and females of the prey. Totalaverages of consumed T. urticae eggs and larvae were 35.5, 23.7; 67, 40.1; 82.2, 54.0 and 118.8, 77.2at prey densities of 5, 10, 15 and 20, respectively. The highest consumption was detected when thepredator fed on T. urticae stages at a density of 20/prey. Eggs laid by predator female were differedsignificantly (P ≤ 0.05) according to stage and density of the introduced preys during the experimentalperiod. The greatest number of deposited eggs was observed when feeding on T. urticae eggs followedby females at different prey densities. Total averages of P. persimilis eggs were 10.7, 19.4, 29.7 and32.7 eggs (for prey eggs) as well as 9.2, 13.4, 22.5 and 25.9 eggs (for prey females), at prey densitiesof 5, 10, 15 and 20, respectively. Differences in total number of deposited eggs of P. persimilis werenot significant (P ≤ 0.05) when the predator was provided with larvae, males and females at each of thetested densities of T. urticae. A positive and high significant correlation was found between densitiesof prey stages and each of feeding capacity and fecundity of the predator. Daily number of depositedeggs was gradually increased to reach the highest value on the sixth day in most cases. Thereafter, thedeposited eggs were decreased to the end of experiment. The present study suggests the possibility ofutilization P. persimilis as an ideal biocontrol agent to reduce T. urticae populations on eggplants

Delayed mortality and sublethal effects of cold stress in Drosophila melanogaster

Analysis of sublethal responses in cold-stressed insects can provide important information about fitness costs and a better understanding of the physiological mechanisms used to prevent and/or to cope with cold injury. Yet, such responses are understudied and often neglected in the literature. Here, we analyzed the effects of cold stress applied to larvae on the mortality/survival and fitness parameters of survivor adults of the vinegar fly, Drosophila melanogaster. Third instar larvae (either cold-sensitive or cold-acclimated) were exposed to either supercooling or freezing stress, both at −5 °C. A whole array of sublethal effects were observed, from mortality that occurs with some delay after cold stress, through delayed development to the pupal stage, to shortened life-span of the adult, and decreased female fecundity. Taking the sublethal effects into account improves the ecological meaningfulness of cold hardiness assay outcomes. For instance, we observed that although more than 80% of cold-acclimated larvae survive freezing to −5 °C, less than 10% survive until adulthood, and survivor females exhibit more than 50% reduction in their fecundity relative to controls. Female fecundity was positively correlated with dry mass and negatively correlated with total protein and glycogen stores. Hence, these parameters may serve as good predictors of survivor adult female fecundity. Further, we provide the concept of a two-component defense system, which (based on analysis of sublethal effects on fitness parameters) distinguishes between physiological mechanisms that help insects to resist (reduce or avoid) or tolerate (survive or repair) injuries linked to cold stress.

Effect of buprofezin on developmental stages of Diaphorina Citri Kuwayama (Hemiptera: Liviidae)

Effect of buprofezin (7.5, 15, 30, 75, 150 and 300 ppm each) on development of Asian citrus psyllid (ACP), Diaphorina citri Kuwayama was studied on Citrus reticulata Blanco (budlings) with different stages of citrus psylla viz., 1-2-and 3-4-days old eggs, and first, third and fifth instar nymphs. The effect of IGR was dose-dependent and varied according to the age of the life stage. Mean egg hatching/plant for both 1-2-and 3-4-day old eggs were significantly low at 150 and 300 ppm. First and third instars were highly susceptible than fifth instars with zero survival at 150 and 300 ppm while adult emergence ranged between 40.33–44.67% from fifth instar at 150 and 300 ppm during season I and II. Similarly, fecundity of adults emerged from such treatments (first and third instar nymphs) were zero at higher concentrations of buprofezin (150 & 300ppm) while fecundity of adult females emerged from treated fifth instar nymphs released on healthy budling were nil. Hence, buprofezin may be incorporated as a management tactic in rotation with insecticides especially during flush emergence after further field evaluation as it has significant effect on growth, reproduction and survival of citrus psylla.

Effects of temperature on the development, fecundity, and life table parameters of Riptortus pedestris (Hemiptera: Alydidae)

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is an economically important insect pest of soybean. We investigated the developmental periods of each life stage as well as adult longevity and female fecundity. The study was conducted at eleven constant temperatures (12.0, 14.0, 15.9, 17.3, 19.3, 23.6, 28.3, 31.2, 34.2, 35.1, and 36.1 °C) for temperature-dependent development, and six constant temperatures (15.8, 19.7, 24.0, 27.8, 32.6, and 35.5 °C) for adult longevity and oviposition. Riptortus pedestris females showed successful egg-to-adult development from 17.9 to 36.1 °C, but failed to complete development under 15.9 °C. Using linear regression, lower developmental threshold (LDT) and thermal constant (K) for the total immature stage were estimated as 14.1 °C and 336.7°-day (DD), respectively. Higher and lower temperature threshold (TH and TL, respectively) were calculated using Lobry–Rosso–Flandrois (LRF) and Sharpe–Schoolfield–Ikemoto (SSI) models; a wider TL-to-TH temperature range (31.4 °C) was observed for LRF than for SSI (18.6 °C). The adult emergence frequency over the full range of constant temperatures was simulated using nonlinear developmental rate functions and the Weibull function. The daily egg production was predicted with respect to temperature and adult age. Biological characteristics of R. pedestris from different local populations are discussed.

Life history traits in a capital breeding pine caterpillar: effect of host species and needle age

BackgroundFor capital breeding Lepidoptera, larval food quality is a key determinant of their fitness. A series of studies have suggested that the larval host species or varieties dramatically impact their development and reproductive output. However, few studies have reported the role of foliar age and adult mating success has often been ignored in these studies. In this paper, the influence of host species and needle age on larval performances, adult mating behavior and fitness consequences has been studied using a capital breeding caterpillar, Dendrolimus punctatus Walker (Lepidoptera:Lasiocampidae).ResultsIn larval performance trial, a strong effect of larval host species and needle age was found on survivorship, developmental duration, body weight, percentage of adult emergence, and growth index, but not on percentage of female progeny. In adult mating trial, larval host species and needle age also significantly affected mating latency and mating duration, but not mating success. In adult fitness trial, female fecundity, longevity and fitness index, but not oviposition duration and fertility, influenced by larval host species and needle age.ConclusionsThese results reveal the importance of larval host species and needle age on larval performance and adult reproductive fitness in this capital breeding insect and provide strong evidence that old needles of masson pine P. massoniana is the best host for D. punctatus.

Erythromycin Exposure Disrupts the Life Cycle Stages of Aedes aegypti L. (Diptera: Culicidae)

Erythromycin is one of the most widely used antibiotics globally and is considered an emerging contaminant in wastewaters and environmental waters. The egg, larval, and pupal stages of the dengue vector Aedes aegypti L. reside and develop in aquatic environments. These mosquito stages may be exposed to compounds in the water, such as erythromycin. Aquatic stages of Ae. aegypti were reared in different concentrations of erythromycin which resulted in significant delay and decrease in eclosion of eggs and pupation of larvae (P < 0.05). Moreover, emergence of adults from pupae, larval survival, and adult female fecundity significantly decreased (P < 0.05). A few occurrences of hypopigmentation in larvae and blisters in adult mosquitoes were also observed. Interestingly, second-generation eggs, which were laid by adult female mosquitoes exposed to erythromycin during their aquatic stages, did not exhibit decreased levels of eclosion in the presence of erythromycin. These results reveal that long-term erythromycin exposure disrupts the Ae. aegypti life cycle by decreasing survival and delaying progression throughout different life stages. However, this study demonstrates that Ae. aegypti can rapidly acquire significant tolerance to the emerging environmental contaminant erythromycin within two generations.

Insecticidal Activity of Garlic (Allium sativum) and Ginger (Zingiber officinale) Oils on the Cotton Leafworm,Spodoptera littoralis(Boisd.) (Lepidoptera: Noctuidae)

Management of Spodoptera littoralis infestation has been achieved by using chemical insecticides; however, the environment-friendly methods without unwanted side effects of these chemicals are becoming very important in modern pest management strategies. Natural products including plant extracts and oils are some of the alternative approaches in pest control. In the present work, insecticidal activities of oils from garlic cloves (Allium sativum), and ginger rhizomes (Zingiber officinale) were evaluated on S. littoralis by means of sublethal concentrations. The essential oils were extracted and their chemical composition was identified using a GC Ultra-ISQ mass spectrometer. The results showed that there were highly significant differences between all treatments and the control in some biological aspects. The larval and pupal duration was significantly prolonged, also pupal weight increased for all treatments when compared to the control. The percentage of hatchability of deposited eggs was significantly decreased, especially when using ginger both oil extracts at LC50 concentration. On the other hand, the pupation percentage, rate of adult emergence, sex ratio and female fecundity were not significantly affected by all applications. The catalase enzyme (CAT) activity showed significant difference only at LC50 of ginger oil.

Mixed artificial diets enhance the developmental and reproductive performance of the edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae)

Diet mixing is a common feeding habit among polyphagous insect herbivores and is believed to be advantageous for performance-related factors like growth, survival and oviposition. However, relatively little is known about the influence of artificial diet or their mixtures on the performance of edible insects. We examined the effects of artificial diet mixtures on the developmental and reproductive performance (survival, developmental time, fresh adult weight and female fecundity) of an edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae). We raised individuals from eggs and reared newly hatched nymphs to adult stage on six different dietary treatments consisting of a single diet, and mixtures of two, three, five, six and eight artificial diets. More diversified diets resulted in shorter development time and greater adult fresh weight and female fecundity compared to the single diet or less diversified diets. Even with slight diet diversification, survival to adult stage was greatly improved. Overall, these results highlight the potential of diet mixtures in achieving maximum adult weights and female fecundity and shortening development time, information which could be used when designing mass-rearing programs for this edible grasshopper.

Demographic drivers of a refugee species: large-scale experiments guide strategies for reintroductions of hirola.

Effective reintroduction strategies require accurate estimates of vital rates and the factors that influence them. The hirola (Beatragus hunteri) is the rarest antelope on Earth, with a global population size of <500 individuals restricted to the Kenya-Somali border. We estimated vital rates of hirola populations exposed to varying levels of predation and rangeland quality from 2012 to 2015, and then built population matrices to estimate the finite rate of population change (λ) and demographic sensitivities. Mean survival for all age classes and population growth was highest in the low-predation-high-rangeland-quality setting (λ=1.08±0.03 [mean ± SE]), and lowest in the high-predation-low-rangeland-quality setting (λ=0.70±0.22). Retrospective demographic analyses revealed that increased fecundity (the number of female calves born to adult females annually) and female calf survival were responsible for higher population growth where large carnivores were absent. In contrast, variation in adult female survival was the primary contributor to differences in population growth attributable to rangeland quality. Our analyses suggest that hirola demography is driven by a combination of top-down (predation) and bottom-up (rangeland quality) forces, with populations in the contemporary geographic range impacted both by declining rangeland quality and predation. To enhance the chances of successful reintroductions, conservationists can consider rangeland restoration to boost both the survival and fecundity of adult females within the hirola's historical range.

Understanding the demographic drivers of realized population growth rates.

Identifying the demographic parameters (e.g., reproduction, survival, dispersal) that most influence population dynamics can increase conservation effectiveness and enhance ecological understanding. Life table response experiments (LTRE) aim to decompose the effects of change in parameters on past demographic outcomes (e.g., population growth rates). But the vast majority of LTREs and other retrospective population analyses have focused on decomposing asymptotic population growth rates, which do not account for the dynamic interplay between population structure and vital rates that shape realized population growth rates (λt=Nt+1/Nt) in time-varying environments. We provide an empirical means to overcome these shortcomings by merging recently developed "transient life-table response experiments" with integrated population models (IPMs). IPMs allow for the estimation of latent population structure and other demographic parameters that are required for transient LTRE analysis, and Bayesian versions additionally allow for complete error propagation from the estimation of demographic parameters to derivations of realized population growth rates and perturbation analyses of growth rates. By integrating available monitoring data for Lesser Scaup over 60yr, and conducting transient LTREs on IPM estimates, we found that the contribution of juvenile female survival to long-term variation in realized population growth rates was 1.6 and 3.7 times larger than that of adult female survival and fecundity, respectively. But a persistent long-term decline in fecundity explained 92% of the decline in abundance between 1983 and 2006. In contrast, an improvement in adult female survival drove the modest recovery in Lesser Scaup abundance since 2006, indicating that the most important demographic drivers of Lesser Scaup population dynamics are temporally dynamic. In addition to resolving uncertainty about Lesser Scaup population dynamics, the merger of IPMs with transient LTREs will strengthen our understanding of demography for many species as we aim to conserve biodiversity during an era of non-stationary global change.

Performance of reproductive system of Dichelops melacanthus (Hemiptera: Pentatomidae) subjected to buprofezin and pyriproxyfen: morphological analysis of ovarioles and testes

The use of insecticides known as insect growth regulators, which are considered more selective to natural enemies, may be an alternative to integrated pest management of stink bugs of the main crops in Brazil. The objective of this study was to evaluate histological changes in the reproductive system of Dichelops melacanthus as well as female fecundity and egg fertility after use of growth-regulating insecticides. The insecticides used were buprofezin (a chitin biosynthesis inhibitor) at a sublethal concentration (LC30 of 2.99 g L-1) and pyriproxyfen (a juvenile hormone analog) at a sublethal concentration (LC30 of 8.35 mL L-1). A completely randomized experimental design was used, with 10 repetitions and 10 insects per experimental unit. Two bioassays were performed: in the first bioassay, fecundity (eggs/female) and fertility (nymph eclosion) of the insects that survived the insecticides were evaluated; in the second bioassay, morphological alterations of the ovarioles of adult females and of the testes of adult male insects that survived the insecticides were evaluated. Buprofezin and pyriproxyfen did not affect the adult sex ratio or female fecundity. Pyriproxyfen reduced the percentage of ecloded nymphs (71.6%) compared with that of the control and buprofezin (96.4 and 90.6%, respectively) treatments and had an ovicidal effect, with direct and indirect action on embryogenesis. Morphological changes were observed in both treatments with buprofezin and pyriproxyfen. The alterations observed in female and male reproductive systems may occur by the action of buprofezin and pyriproxyfen on the morphology of both ovarioles and testes.

Performance of reproductive system of Dichelops melacanthus (Hemiptera: Pentatomidae) subjected to buprofezin and pyriproxyfen: morphological analysis of ovarioles and testes

The use of insecticides known as insect growth regulators, which are considered more selective to natural enemies, may be an alternative to integrated pest management of stink bugs of the main crops in Brazil. The objective of this study was to evaluate histological changes in the reproductive system of Dichelops melacanthus as well as female fecundity and egg fertility after use of growth-regulating insecticides. The insecticides used were buprofezin (a chitin biosynthesis inhibitor) at a sublethal concentration (LC30 of 2.99 g L-1) and pyriproxyfen (a juvenile hormone analog) at a sublethal concentration (LC30 of 8.35 mL L-1). A completely randomized experimental design was used, with 10 repetitions and 10 insects per experimental unit. Two bioassays were performed: in the first bioassay, fecundity (eggs/female) and fertility (nymph eclosion) of the insects that survived the insecticides were evaluated; in the second bioassay, morphological alterations of the ovarioles of adult females and of the testes of adult male insects that survived the insecticides were evaluated. Buprofezin and pyriproxyfen did not affect the adult sex ratio or female fecundity. Pyriproxyfen reduced the percentage of ecloded nymphs (71.6%) compared with that of the control and buprofezin (96.4 and 90.6%, respectively) treatments and had an ovicidal effect, with direct and indirect action on embryogenesis. Morphological changes were observed in both treatments with buprofezin and pyriproxyfen. The alterations observed in female and male reproductive systems may occur by the action of buprofezin and pyriproxyfen on the morphology of both ovarioles and testes.

Modeling the Temperature- and Age-Dependent Survival, Development, and Oviposition Rates of Stable Flies (Stomoxys calcitrans) (Diptera: Muscidae).

Stable flies (Stomoxys calcitrans (L.)) can be a serious pest associated with cattle facilities. In Denmark, they occur most abundantly at organic farms, where they cannot be controlled by means of insecticides. On traditional farms, where chemical control is widely used, development of resistance is of increasing concern. Therefore, interest in biological control or other alternative methods has been growing during the recent years. In order to understand the complex relationships between a pest and its natural enemies in a variable environment, it is necessary to know how temperature affects the dynamics of the involved species. In this paper, we apply data derived from several existing sources to investigate the influence of temperature on development and survival of eggs, larvae, pupae, and adult stable flies, as well as on the fecundity of adult females. We demonstrate that the same modeling framework (called SANDY), previously applied to lifetable data of the pteromalid pupal parasitoid (Spalangia cameroni Perkins), a biological control agent used against stable flies, can also be used to model S. calcitrans. However, the predicted temperature responses depend on the data sources used to parameterize the model, which is reflected by differences in estimated population growth rates obtained from American and non-American studies. Elasticity analysis shows that growth rates are more sensitive to changes in viability, in particular of adult flies, than in fecundity, which may have implications for the management of stable fly populations.

Physiological Responses Induced by Ostrinia furnacalis (Lepidoptera: Crambidae) Feeding in Maize and Their Effects on O. furnacalis Performance.

Plants damaged by herbivorous insects often respond by mounting a series of defense responses that can inhibit the insect's fitness. Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) is a major insect pest in maize throughout much of Asia, Australia, and the western Pacific islands. We examined the effects of O. furnacalis -induced maize defenses on O. furnacalis fitness, and explained the effects from biochemical changes that occur in maize leaves in response to O. furnacalis feeding. The results of the age-stage, two-sex life table showed that significantly longer larval and pupal life spans, and total preoviposition period (TPOP) occurred. A decrease in the longevity and fecundity of female adults was observed in O. furnacalis fed on O. furnacalis -damaged leaves. The mean generation time ( T ), finite rate of increase ( ), net reproductive rate ( R 0 ), and intrinsic rate of increase ( r ) were also correspondingly affected. Biochemical assays indicated that 24 h of O. furnacalis herbivory resulted in decreased levels of the benzoxazinoids, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), and 2-(2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one)-β-D-glucopyranose (DIMBOA-Glc), and a corresponding increase in 2-(2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one)-β-D-glucopyranose (HDMBOA-Glc). Maize also exhibited higher activities of the defensive enzymes-peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and polyphenol oxidase (PPO)-after 24 h of herbivory. We concluded that exposure to O. furnacalis -damaged leaves had an inhibitory impact on the fitness of the neonate to pupa stages of O. furnacalis . The observed higher level of HDMBOA-Glc and higher enzymatic activities of POD, SOD, CAT, and PPO may account, in part, for the observed inhibitory effects on O. furnacalis fitness.

Extract of the PlantCostus speciosusas a New Acaricide for Control of the Two-Spotted Spider MiteTetranychus urticaeKoch (Acari: Tetranychidae)

Extract of the plant Costus speciosus was evaluated for its potential acaricidal and ovicidal activities against the two-spotted spider mite, Tetranychus urticae Koch, for the first time under laboratory conditions. The acaricidal activity was performed by studying the mortality, fecundity, fertility and offspring development of adult females at two different temperatures. The LC50 value of C. speciosus is 2.3 %. Treatment significantly affected the fecundity of the females, percentage of hatched eggs, percentage of eggs reaching adult stages and duration of each life cycle stage. The acaricidal efficacy of this extract is temperature dependent. The greater susceptibility of T. urticae to C. speciosus was recorded at a lower temperature. Concerning the ovicidal activity of C. speciosus, extract exhibited 79.67 ± 4.01 % mortality on eggs. It also significantly delays the egg hatching of T. urticae compared to the control. Results showed that hatching started on the sixth day post-deposition in the treated group compared to the fourth day in the control group. All hatched eggs turned into nymphs in the control group while treatment reduced the number of hatched eggs and caused death of all hatched larvae before reaching nymphal stages. Extract of C. speciosus has promising acaricidal and ovicidal activities that could lead to the development of new bio-acaricides and is worth further investigation.

Effects of the miticide hexythiazox on biology of Galendromus flumenis (Acari: Phytoseiidae)

ABSTRACTThe Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae), is a major pest of dates. The miticide hexythiazox (Savey® 50 DF) is the current industry standard for Banks grass mite management on dates. However, sole reliance on hexythiazox as a single control strategy may lead to resistance in the mite population. Incorporating biological control into the Banks grass mite management on dates is a step towards a more integrated programme. The predatory mite, Galendromus flumenis (Chant), is the most abundant predator and the only phytoseiid species on date bunches. Conservation of G. flumenis is essential for a successful integrated mite management programme, and it is important to understand the impact of hexythiazox on the biological control of Banks grass mite by G. flumenis. For this purpose, the toxic effects of the recommended field rate of hexythiazox on the development of different immature stages and the fecundity of adult females of G. flumenis were evaluated. Laboratory bioassays were conducted in which predators were both treated topically by hexythiazox sprays and exposed to residues on the arena surface and on the sprayed prey. Mortality due to hexythiazox was 0.09% in eggs, 2.63% in larvae, 0.00% in protonymphs and 2.08% in adult females of G. flumenis. Hexythiazox did not have any significant effect on the fecundity of the treated females, hatch rate of the laid eggs, progeny development or sex ratio. Results suggest that hexythiazox would not disrupt the biological control of Banks grass mite by G. flumenis in the field.