Gross Reproductive Rate Research Articles

Influence of sublethal effects of imidacloprid, indoxacarb and lambda-cyhalothrin on life history traits of Blattella germanica (Blattodea: Ectobiidae)

The aim of this study was to investigate the effects of sublethal doses (LD10 and LD25) of lambda-cyhalothrin, imidacloprid, and indoxacarb on life-history traits of B. germanica using age-stage, two-sex life tables. Therefore, The results showed that the longevity of B. germanica adults was significantly decreased when compared to adults in control treatment. Moreover, the cockroach females lived longer than males. Furthermore, nymph longevity of B. germanica was increased compared to the nymph in control treatment. Additionally, it was observed that the fecundity, reproductive value (Vxj), net reproductive rate (R0), gross reproduction rate (GRR), finite rate of increase (λ), and intrinsic rate of increase (rm) were significantly reduced. On the contrary, the means of generation time (T) and the total preovipositional period (TPOP) of treatments were increased compared to the control series. Understanding the mechanisms of insecticidal sublethal impacts on insects and on their subsequent generations is of ultimate importance for proper applying of insecticides.

‎‎Lethality and effects on biological and population growth parameters of ladybird predator Hippodamia variegata (Goeze) treated by some plant essential oils

The lethal and sublethal effects of essential oils isolated from Heracleum persicum, Mentha pulegium, and Achillea millefolium were studied on ladybird predator Hippodamia variegata feeding on wheat aphids. M. pulegium and H. persicum essential oils had, respectively, the most and the least lethal effects on the egg and first-instar larvae of the ladybird. The essential oil of M. pulegium had the most adverse effects on gross reproductive rate (GRR), net reproductive rate (R0 ), age-specific survival rate (lx ), and age-specific fecundity (mx ). Contrary, the most intrinsic rate of increase (rm ) and fecundity were recognized on ladybirds treated with H. persicum essential oil.

Effects of Imunit Insecticide on Biological Characteristics and Life Table Parameters of Spodoptera cilium (Lepidoptera: Noctuidae).

Simple SummarySpodoptera cilium Guenee (Lepidoptera: Noctuidae) is one of the grass pests in some parts of the world, including the southern regions of Iran. The larvae of S. cilium feed on grasses and heavy infestations can severely destroy lawn grasses. In the present study, we monitored the effects of Imunit on some biological and demographic parameters of the offspring generation. Our results indicate that Imunit reduced the survival rate and fecundity of S. cilium and could be used in the management programs of this pest.Imunit is a mixture of alpha-cypermethrin + teflubenzuron, and has been launched for controlling caterpillars. In this study, the effects of Imunit at LC50 and LC30 were investigated on parental and offspring generation of S. cilium, according to age-stage, two-sex life table. The experiments were conducted by leaf dipping method at 25 °C and 60 ± 5% relative humidity, under a cycle of 16 h fluorescent light and 8 h darkness. LC30 and LC50 concentrations of Imunit increased the immature developmental time of S. cilium in the offspring generation, while the LC50 of Imunit significantly reduced the developmental time of adults. The adult pre-oviposition period and total pre-oviposition period considerably increased when offspring were treated with LC50 of Imunit. In offspring of S. cilium exposed to LC50 and LC30 concentrations of Imunit, the gross reproductive rate (GRR), net reproduction rate (R0), the intrinsic rate of population increase (r), and the finite rate of population increase (λ) significantly reduced compared to the control. This study showed that the application of Imunit at LC50 could suppress the S. cilium population and can be used in the integrated management program of this pest.

Determining the Effect of Temperature on the Growth and Reproduction of Lasioderma serricorne Using Two-Sex Life Table Analysis.

Simple SummaryThe developmental time of L. serricorne significantly decreases as the temperature increases from 21 °C to 33 °C. Adult L. serricorne have a relatively longer oviposition period and the highest fecundity at a temperature of 33 °C. Lasioderma serricorne has the highest age-stage-specific survival rate (Sxj) at a temperature of 27 °C, but a higher fecundity (mx and lxmx) is observed at temperatures of 30 °C and 33 °C. A comprehensive analysis shows that among the experimental temperatures, a temperature between 30 °C and 33°C is the most appropriate for the population development of the pest. Our research results provide theoretical information for the control of pests and mass rearing of L. serricorne.The cigarette beetle Lasioderma serricorne (Fabricius) is a major pest of stored products worldwide, especially tobacco and foods, causing huge economic losses. This study aimed to experimentally investigate the population dynamics of this pest at different temperatures and provide theoretical input for its control. Populations of L. serricorne were established under laboratory conditions at five temperatures (21 °C, 24 °C, 27 °C, 30 °C, and 33 °C). Results showed that an increasing temperature significantly affected the developmental time, longevity, oviposition period, and fecundity of L. serricorne. Both the longevity and fecundity of adult beetles were significantly reduced as the temperature increased. High temperatures significantly reduced the total duration of the preoviposition period but prolonged the oviposition period of L. serricorne. Increasing the temperatures from 21 °C to 33 °C significantly influenced the life table parameters of L. serricorne. The intrinsic increase rate (r), finite increase rate (λ), and gross reproductive rate (GRR) all increased with a greater rearing temperature, but mean generation time (T) was significantly shortened. To our best knowledge, this is the first report to detail the entire life history of the cigarette beetle in response to different temperatures when reared on tobacco dry leaves. This finding may provide basic information on the occurrence of L. serricorne in a warehouse setting and its mass rearing.

Biology and life tables of Telenomus remus (Hymenoptera: Scelionidae) as parasitoid of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Telenomus remus (Hymenoptera: Scelionidae), is an endoparasitoid on eggs of Spodoptera frugiperda (J. E. Smith). S. frugiperda. The information of T. remus as a natural enemy of S. frugiperda is very limited. The research objective is to determine some biological aspects of T. remus, i.e. longevity, fecundity, and life table variables. The demographic statistics using the jackknife method. T. remus is collected from the field identified as T. remus. The immature stage of T. remus reached 8.13 days, the longevity of the male was 10.07 days, while a female was 10.29 days with a fecundity of 75 eggs, and a sex ratio of male and female was 1:2.16. T. remus life table, i.e. gross reproduction rate (GRR) was 74.67 individuals/generation, net reproduction rate (R0) was 45260.60 females/females/generation, with generation period (T) was 8.62 days, and intrinsic rate of increase (r) was 1.24 females/female/day. The success parasitization of T. remus reaches 91%.

Biology and life table of Trichogramma chilotraeae, Egg parasitoids of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Spodoptera frugiperda is a species of armyworm that attacks maize crops globally and is a dangerous new invasive pest in Indonesia. Biological control, which employs natural enemies, is one method of controlling this pest. One of the natural enemies found in the field is the egg parasitoid of the Trichogrammatidae family. This study aimed to determine the reproductive capacity of the parasitoid on S. frugiperda eggs. The tested parasitoids were collected from S. frugiperda eggs on corn cultivations in Tenjolaya Village, Bogor Regency, West Java Province. The identification results showed that the parasitoid species used in this study was Trichogramma chilotraeae. The development periods of eggs, first instar larvae, second instar larvae, and pupae in the laboratory were 1.16 days, 1.18 days, 1.39 days, and 3.28 days, respectively. The reproductive capacity of T. chilotraeae on S. frugiperda eggs, referred to as the net reproduction rate (Ro), was 28.13, gross reproduction rate (GRR) was 30.43. the average time for one generation (T) was 9.07. The intrinsic rate of increase (r) was 5.54, and Doubling time (DT) was 1.88. Thus, the egg parasitoid of T. chilotraeae was not very effective as a potential biological agent for S. frugiperda.

A Laboratory Assessment of the Lethal and Sub-Lethal Effects of Four Insecticides Considered for Commercial Control of the Tomato Leaf Miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leaf miner, Tuta absoluta (Meyrick), is a key pest of the Solanaceae, which is commercially controlled worldwide using insecticides. In this study, the toxicity of various concentrations of four insecticides, a thiamethoxam + lambda-cyhalothrin combination, indoxacarb, acetamiprid, and hexaflumuron, were assessed against second-instar larvae of T. absoluta. Results showed that indoxacarb with a LC50 value of 7.13 mg a.i./l was more toxic than acetamiprid, thiamethoxam + lambdacyhalothrin, and hexaflumuron. Sub-lethal effects of insecticides on demographic and biological parameters of T. absoluta were evaluated using LC30 concentrations estimated from bioassays. The lowest intrinsic rate of increase (rm) was shown in indoxacarb treatments (0.083/day). Except for hexaflumuron, the net reproductive rate (R0) and gross reproductive rate (GRR) were significantly lower in all treatments compared to the control. The shortest and longest adult longevities were shown in the indoxacarb treatment (18.92 days) and the control (26.94 days), respectively. The lowest fecundity was observed in the indoxacarb treatment (46.62 offspring/female). Except for hexaflumuron, the pupal weight was significantly decreased in all insecticide treatments. With the results of this study, combined with acute toxicity data, the significant adverse effects of indoxacarb, acetamiprid, and thiamethoxam + lambda-cyhalothrin on demographic and biological parameters of T. absoluta larvae were determined providing support for their consideration in commercial use in suppressing this pest.

Sub-lethal effects of a Bt-based bioinsecticide on the biological conditioning of Anticarsia gemmatalis.

Bioinsecticides based on Bacillus thuringiensis (Bt) Berliner, 1915 are widely used to control lepidopteran in several crops. However, surviving insects exposed to the sub-lethal concentration of Bt-based bioinsecticides can suffer a multitude of effects on the biological conditioning known as hormesis. Here, we aimed to provide a clearer understanding of the biological conditioning of Anticarsia gemmatalis (Hübner, 1818), exposed to different concentrations of a Bt-based bioinsecticide, by assessing life table parameters over three generations. We defined five sub-lethal concentrations (LC5, LC10, LC15, LC20, and LC25) from the response curve estimate of A. gemmatalis. Deionized water was used as a control. We assessed the parameters of eggs-viability and the duration of the stages, incubation, larval, pre-pupal, pupal, adult, pre-oviposition and total biological cycle. Data were used to construct the fertility life table using the two-sex program. The survival curves showed greater variation in the proportion of individuals at each development stage using the LC25. The sub-lethal concentrations did not influence the incubation-eggs period, pre-pupal and pupal. However, the larval and adult stages using LC25 and LC10 were the most affected. Changes in sex ratio were observed using LC20 and LC5. The toxic effect of Bt-based bioinsecticide interfered mainly in the parameters of fertility, sex ratio, net reproduction rate (R0), and gross reproduction rate (GRR).

How long-term mass rearing affects the quality of the Trichogramma embryophagum (Hartig) (Hymenoptera: Trichogrammatidae) reared on Sitotroga cerealella (Olivier) eggs

BackgroundMaintaining the quality and efficacy of biological control agents during long-term mass rearing plays a crucial role in the success of a biological control program. In this study, the biological traits of a local population colony of Trichogramma embryophagum (Hartig) with rearing on Sitotroga cerealella (Olivier) eggs for over 40 generations (G) were assessed.ResultsFemale adult longevity was significantly different among generations, ranging from 7.98 d in G5 to 5.19 d in G40. The reared wasps showed highest fecundity (60.50 eggs/female) in G5 compared to the other generations. The female sex ratio varied from 63.16% in G5 to 49.31% in G40. Significant differences were observed in population growth parameters and the highest gross reproductive rate (GRR) (40.96 eggs/individual) and net reproductive rate (R0) (38.21 eggs/individual) were found in G5. However, a non-significant difference was found in the intrinsic rate of natural increase (r) until the 10th generation, but its values significantly declined with increasing the generation numbers. The finite parasitism rate (ω) ranged from 0.468 host/parasitoid/day in G5 to 0.274 host/parasitoid/day in G40.ConclusionsThe results showed that the quality of T. embryophagum reared under continuous laboratory conditions declined after 10 generations, and for use of them in biological control programs under field conditions, the reared population should be refreshed by adding wild individuals from time to time.

Effects of plant probiotic bacteria and herbivore-induced plant volatiles on life table parameters of Tetranychus urticae (Acari: Tetranychidae) on kidney bean’s attached leaves

ABSTRACT The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an agricultural important polyphagous pest of many crops that causes significant yield loss. In this study, the effect of four herbivore-induced plant volatiles (HIPVs) (methyl jasmonate, methyl salicylate, indole, and 3-pentanol) with a concentration of 100 mmol/L and two plant probiotic bacteria (PBB) (Bacillus pumilus INR7 and Bacillus velezensis H3), were investigated on life table parameters of T. urticae under laboratory conditions (25 ± 1°C, 65 ± 5% RH, and 16 L: 8D). The T. urticae cohorts were reared on attached leaves of kidney bean plants (Phaseolus vulgaris L.) treated with HIPVs and PBBs, separately. The life history data were analysed using age-stage, two-sex life table theory. The intrinsic rate of increase (r) on methyl salicylate (0.1667 ± 0.0087 day-1) and B. velezensis treatment (0.1640 ± 0.0099 day-1) was significantly lower than the control group (0.1934 ± 0.0100 day-1). The finite rate of increase (λ) ranged from 1.178 ± 0.0116 day-1 on the B. velezensis to 1.2134 ± 0.0121 day-1 on the control with a significant difference (P < 0.05). The gross reproduction rate (GRR) on the indole treatment was significantly lower than the other treatments (28.14 ± 3.66 offspring). Based on the results, methyl salicylate, B. velezensis and indole could be considered resistance inducing materials against T. urticae.

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.

Influence of elevated temperature on the fitness of Diamondback moth, Plutella xylostella (L.) in cauliflower

Aim: To understand the effect of elevated temperature on the bionomics and fitness parameters of Plutella xylostella which would help in predicting the population growth rates and formulating appropriate management tactics. Methodology: In the present investigation, the fitness parameters of diamondback moth were studied at six different temperatures (31, 32, 33, 34, 35 and 36°C) in cauliflower in Open Top Chambers. Observations were recorded on the survival, longevity and fecundity at daily interval. The raw data on bionomics and life table parameters were analyzed using TWO-SEX- MS chart. Results: The total life cycle of P. xylostella was longer at 31°C and it declined with increasing temperatures. However, P. xylostella did not complete its development at 35 and 36 °C. The intrinsic rate of increase (rm) increased from 0.22 at 31°C to 0.28 at elevated temperature of 34°C. Temperature also had a significant effect on the net reproductive rate (R0), Gross Reproductive Rate (GRR) and finite rate of increase (λ). Interpretation: The fitness parameters will help to predict the change that occur in P. xylostella population due to climate change and global warming.

Life history traits and demographic parameters of Typhlodromus transvaalensis reared on three eriophyid species (Acari: Phytoseiidae: Eriophyidae)

ABSTRACT Typhlodromus transvaalensis is a generalist predatory mite with economic potential to control eriophyid mites in various fruit trees. Developmental times were significantly longer on Aculus fockeui and Calepitrimerus baileyi than on Aceria dioscoridis. Females of T. transvaalensis presented the shortest oviposition period (20.39 days) and adult longevity (28.96 days) on C. baileyi, while having the longest periods on A. dioscoridis (29.77 and 36.17 days). Total fecundity of females offered A. dioscoridis (39.90 eggs/female) was highest, followed by A. fockeui (27.12 eggs/female) and was lowest on C. baileyi (23.26 eggs/female). The intrinsic rates of increase (r) were higher on A. dioscoridis (0.225 females/female/day) than on A. fockeui (0.175 females/female/day) and C. baileyi (0.168 females/female/day). The generation time (T) was statistically similar on A. fockeui (17.788 days) and C. baileyi (17.501 days) and longest, while was shortest on A. dioscoridis (15.711 days). The net reproductive rate (R0) and the gross reproductive rate (GRR) were highest on A. dioscoridis (34.457 eggs/individual and 35.390 eggs/individual), whereas the lowest values were obtained on C. baileyi (19.107 eggs/individual and 19.500 eggs/individual). The results suggest that T. transvaalensis is a promising control agent for A. fockeui and C. baileyi on pear and apple trees.

&lt;p class="Body"&gt;&lt;strong&gt;The effects of bifenazate on life history traits and population growth of &lt;em&gt;Amblyseius swirskii&lt;/em&gt; Athias-Henriot (Acari: Phytoseiidae)&lt;/strong&gt;&lt;/p&gt;

Tetranychus urticae Koch (Acari: Tetranychidae) is a notorious crop pest with a worldwide distribution that has developed resistance to a wide range of acaricides. Combined tactics of pest management have special significance not only for a reduction in pesticide residues but also to maintain the natural enemy activity, which is an objective of IPM programs. Here, we investigated the effect of low-lethal concentrations of bifenazate at LC10, LC20, and LC30 on development and reproduction parameters of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Lethal and sub-lethal concentrations were estimated using leaf dip bioassay method. The crude data were analyzed based on age-stage, two-sex life table analysis. Toxicological assays showed bifenazate treatments gradually decreased the longevity and total life span of both sexes. Our results indicated that reproductive and total fecundity of the next generation were also affected by sublethal concentrations. All concentrations caused a significant decline in oviposition days, compared to the control. The intrinsic rate of increase (rm) varied from 0.1344 to 0.1151 day-1 for the mites treated with distilled water and LC30 treatments, respectively. The finite rate of increase (λ) was affected by the acaricide concentration (lowest at LC30 concentration: 1.1221 day-1). Bifenazate concentration (LC10, LC20 and LC30) treatments gradually reduced the gross reproduction rate (GRR) and net reproductive rate (R0). Based on obtained results from current study, bifenazate is not a favorable acaricide with A. swiriskii and cannot be recommended to use with this predatory mite in integrated management.

Continuous rearing on Ephestia kuehniella reshaped quality of the parasitoid wasp Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

• Quality of T. brassicae decreased over long-term mass rearing on E. kuehniella. • G5 and G10 had the highest GRR , R 0 , r and λ . • G5 and G45 had the highest and lowest values of c 0 , ψ and ω , respectively. • The efficacy of wasps decreased dramatically after G20. Continuous mass rearing of Trichogramma brassicae (Bezdenko) at commercial mass-rearing insectaries may affect both quality and performance of natural enemies. In the present study, we studied the quality and performance of a colony of T. brassicae reared for over 45 generations (G) on Ephestia kuehniella Zeller using two-sex life table parameters and parasitism capacity. Our results revealed that although different generations showed no significant difference in terms of female longevity or total life span until G35, G5 and G10 had the highest values of fecundity, gross reproductive rate ( GRR ), net reproductive rate ( R 0 ), intrinsic rate of natural increase ( r ), and finite rate of increase ( λ ). No significant difference in male adult longevity was found among different generations. The longest and shortest mean generation times ( T ) were found in G10 (13.65 ± 2.31 d) and G45 (13.25 ± 3.37 d), respectively. The finite rate of parasitism ( ω ) ranged from 0.355 ± 2.332 host/parasitoid/day in G5 to 0.242 ± 0.017 host/parasitoid/day in G45. However, ω did not show any significant difference until G20. These results indicate that T. brassicae wasps held under continuous laboratory rearing declined in quality after 20 generations, and therefore periodical rejuvenation of the colony by adding feral parasitoids is strongly recommended.

Temperature-based phenology model to predict the development, survival, and reproduction of the oriental fruit fly Bactrocera dorsalis

The oriental fruit fly Bactrocera dorsalis (Diptera: Tephritidae) is a major pest of fruit and vegetable production systems on several continents. The pest has invaded many countries, causing considerable impact on fruit production systems and commercialization. In this study we determined the relationship between temperature and development, survival and reproductive parameters of B. dorsalis on an artificial diet under laboratory conditions under 7 constant temperatures (10, 15, 20, 25, 30, 33 and 35 °C) with 70±10% relative humidity and a photoperiod of L12:D12. We validated the laboratory results with a full life table analysis under semi-natural conditions in a screenhouse. We used the Insect Life Cycle Modeling (ILCYM) software for all mathematical models and simulations applied to all life history parameters. Bactrocera dorsalis completed its development at temperatures ranging between 15 and 33 °C with the mean developmental time of egg, larva, and pupa ranging between 1.46 and 4.31 days, 7.14-25.67 days, and 7.18-31.50 respectively. The models predicted temperatures ranging between 20 and 30 °C as favorable for development and survival, and 20 to 25 °C for optimal fecundity of B. dorsalis. Life table parameters showed the highest gross reproductive rate (GRR), net reproductive rate (Ro), intrinsic rate of increase (rm), and finite rate of increase (λ) between 25 and 31 ᵒC while generation time (T) and doubling time (Dt) were low at this interval. The effects of future climate change on B. dorsalis life history parameters were further investigated and the outcome from this study will help in the management of B. dorsalis in different agroecologies in the context of ongoing climate change.

Statistik demografi Dolichotetranychus floridanus Banks pada dua kultivar nanas (Ananas comosus (L.) Merr.)

Pineapple is one of important fruit crops in Indonesia. One of important problems in pineapple production is pest infestation.. This study aims to investigate the biology, demography, and life cycle of Dolichotetranychus floridanus Banks on two pineapple cultivars (Queen and Cayenne). Observation of mite development (eggs-adults) were conducted every 6 hours. Adults were observed everyday to record the fecundity. The life table was constructed from the survivor and fecundity of D. floridanus. Based on this table, the variables of population growth, including gross reproduction rate (GRR), net reproductive rate (R0), mean generation time (T) and increase intrinsic rate (r) were determined. The results showed that the GRR, R0, and r of D. floridanus in the Queen cultivar were higher than Cayenne cultivar, while the T in the Queen cultivar was lower. Queen cultivar more suitable for D. floridanus than Cayenne cultivar.

&lt;p class="Body"&gt;&lt;strong&gt;The response of common bean (&lt;em&gt;Phaseolus vulgaris&lt;/em&gt; L.) to salinity and drought stresses and life table parameters of &lt;em&gt;Tetranychus urticae&lt;/em&gt; Koch reared on it&lt;/strong&gt;&lt;/p&gt;

Plants in nature are constantly exposed to various stresses resulting from fluctuating environmental conditions which adversely affect their growth and development and may affect the performance of herbivores feeding on them. Drought and salinity are the most serious problems of agriculture due to climatic changes. According to global warming and drying of Urmia salty lake in Northwestern Iran which could result in salinization of agricultural lands nearby, the focus of this study was to examine the effect of two above mentioned stresses on a host plant and its pest population. Three levels of salinity (50 (low), 100 (intermediate) and 150 (high) mM NaCl) and water deficit (40–50% the amount of water given to control plants) were induced to common bean (Phaseolus vulgaris) as stress factors and the following characteristics were measured: fresh and dry weight, leaf area, chlorophyll, carotenoid, proline and protein contents and CAT, APX and GPX enzyme activities. The life table parameters of two-spotted spider mite, Tetranychus urticae Koch, reared on stress-induced plants were measured and compared with control. The high saline condition caused plant defoliation and was deleted from results. The low saline condition caused an increase in fresh weight and decrease in chlorophyll and protein contents of plant. Intermediate saline condition caused an increase in APX and CAT enzyme activities and decrease of dry weight, chlorophyll, protein and proline contents. Drought condition caused an increase of APX and GPX enzyme activities and proline content and decrease of dry weight and chlorophyll content. Analysis of life table data of T. urticae showed a significant decrease of net reproductive rate (R0), mean generation time (T) and gross reproductive rate (GRR) of mites reared on plants under both of stresses. The intrinsic rate of increase (r) and finite rate of increase (λ) decreased significantly only for mites reared on plants under intermediate saline condition.

Acetamiprid resistance and fitness costs of melon aphid, Aphis gossypii: An age-stage, two-sex life table study

The melon aphid, Aphis gossypii is a globally distributed crop pest with a wide host range. The intensive use of insecticides against this insect over several years has led to develop resistance against many insecticides including acetamiprid. Understanding the relationship between acetamiprid resistance and fitness of A. gossypii is essential to limit the spread of the resistant population in the field. In this study, age-stage, two-sex life table approach was used to investigate these relationships in the lab. Results showed that resistant strain (Ace-R) had a reduced fitness (relative fitness = 0.909) along with significantly decreased adult longevity, fecundity, net reproductive (R0), mean generation time (T) and gross reproductive rate (GRR). Compared to the susceptible strain (Ace-S), the pre-adult period and total pre-oviposition period (TPOP) were also significantly shorter in Ace-R strain. Moreover, the expression profiles of EcR, JHBP, JHAMT, JHEH, USP and Vg genes supposed to be involved in insect reproduction and development were analyzed using Quantitative Real Time PCR. The EcR, JHBP, JHAMT and USP genes were up-regulated, Vg gene was down-regulated while the mRNA level of JHEH gene was statistically same in the Ace-R strain compared to the Ace-S strain. Collectively, this study provides the occurrence and magnitude of fitness costs of A. gossypii against acetamiprid resistance and could be helpful to manage the resistance evolution in field populations.

Host dependent demographic parameters of spider mite Oligonychus biharensis (Hirst) on two bean species

The influence of two economic host plants country bean (Lablab purpureus L.) and mung bean (Vigna radiata (L. Wilczek)) on the development, reproduction and demographic parameters of the spider mite, Oligonychus biharensis (Acari Tetranychidae) were constructed using two-sex life table program under laboratory condition at 25 °C, 60–80% RH, and a photoperiod of 16 L:8D h. Both male and female of O. biharensis successfully completed their development from egg to adult on two host plants. Immature development of O. biharensis was shorter on L. purpureus than on V. radiata. Oviposition, lifetime fecundity, female adult longevity of the spider mite was higher on L. purpureus than V. radiata. The net reproduction rate (R0), intrinsic rate of natural increase (rm), mean generation time (tG), finite rate of increase (λ) and gross reproduction rate (GRR) of O. biharensis were significantly affected by host plants. The R0-values of O. biharensis were significantly higher on L. purpureus than V. radiata. GRR also showed the similar trend as of the net reproduction rate. The mean generation time of O. biharensis was higher on V. radiata than on L. purpureus. Based on the intrinsic rate of population increase, L. purpureus was more suitable than V. radiata. The results of the study reveal that the host plants greatly influenced the life parameters of the spider mite O. biharensis and it helps to reveal the population dynamics on particular host plant species.