Lower Intrinsic Rate Of Increase Research Articles

The effect of sublethal doses of flupyradifurone on the life table and esterase enzyme of Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae)

The aim of this study was to determine the effect of two different sublethal doses (LC10 and LC30) of flupyradifurone on the life table and esterase enzyme of Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae). The experiments were conducted in 2022 in Isparta University of Applied Sciences laboratory and climate rooms in 2022 as 1 control + 2 sublethal doses. For the life table, control, LC10 and LC30 doses were established as 30, 25 and 30 replications, respectively. Female and total lifespan of M. persicae adults exposed to LC10 concentrations of flupyradifurone were significantly shortened. Daily and total numbers of the offsprings decreased at both LC10 and LC30 concentrations. Furthermore, these negative effects on the aphid were revealed as a lower intrinsic rate of increase (r), net reproductive rate (R0), finite rate of increase (λ) and fecundity (F). Based on the obtained data, flupyradifurone seems to suppress the population growth of M. persicae. It was determined that esterase enzyme activity involved in pesticide detoxification did not change in populations exposed to two different sublethal doses of flupyradifurone and unexposed (control). It is thought that this study facilitates the understanding of the lethal and sublethal effects of flupyradifurone on aphid performance.

Biochemical characteristics of sorghum cultivars affect life table parameters, feeding performance, and digestive enzyme activities of Helicoverpa armigera

AbstractThe cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a major insect pest of various agricultural crops worldwide. In this study, the effects of eight sorghum [Sorghum bicolor (L.) Moench, Poaceae] cultivars (Payam, Pegah, Sepideh, Spidfid, Kimia, KGS23, KFS2, and KFS18) on life table parameters, feeding performance, and activities of digestive enzymes in H. armigera were assessed under laboratory conditions. The insects were fed grains of the eight cultivars. Furthermore, the phytochemicals starch, proteins, flavonoids, and phenolic compounds in the grains were quantified to investigate their relationship with ecological and physiological parameters in H. armigera. Our results revealed that H. armigera had the shortest development time when reared on cv. Sepideh and the longest development time when reared on cv. Payam. The insects reached the highest and lowest intrinsic rate of increase (r) on cv. Sepideh and Payam, respectively. The relative growth rate (RGR) and efficiency of conversion of digested food (ECD) of larvae were highest and lowest on cv. Sepideh and Payam, respectively. Larval proteolytic activity was highest on cv. KFS18 and lowest on cv. Sepideh. Concerning phytochemicals, protein content was highest in cv. KFS18 and lowest in cv. Payam and KGS 23. Total phenolic levels were highest in cv. Payam and lowest in cv. Sepideh. According to the correlation analysis, overall, plant protein content was negatively correlated with insect development time, but positively correlated with pupal weight and r. Total phenolic content was positively correlated with insect development time, and negatively correlated with r and RGR. Cluster analysis indicated that cv. Sepideh was the most susceptible host, whereas cv. Payam was the most resistant. Therefore, cv. Payam may be a candidate for use in integrated pest management (IPM) against H. armigera.

Biological Fitness Cost, Demographic Growth Characteristics, and Resistance Mechanism in Alpha-Cypermethrin-Resistant Musca domestica (Diptera: Muscidae).

Musca domestica L., a pest of animals and humans, has developed resistance to alpha-cypermethrin, a pyrethroid insecticide commonly used to control medically important pests in many countries, including Saudi Arabia. We investigated the mechanism underlying the development of alpha-cypermethrin resistance and life history characteristics of alpha-cypermethrin-susceptible (Alpha-SS) and alpha-cypermethrin-resistant (Alpha-RS) M. domestica using the age-stage, two-sex life table theory, which is crucial for developing a future rational management strategy and minimizing the negative effects of alpha-cypermethrin on the environment. Our results showed that Alpha-RS M. domestica had a 405.93-fold increase in resistance to alpha-cypermethrin relative to Alpha-SS M. domestica. This increase in the resistance toward insecticide was attributed to metabolic enzymes, such as glutathione S-transferases, specific esterases, and cytochrome P450 monooxygenases. Furthermore, Alpha-RS M. domestica exhibited lower relative fitness (0.50), longevity, survival rate, life expectancy, reproductive values, intrinsic rate of increase, net reproductive rate, fecundity, maternity, and finite rate of increase, along with shorter larval, female preadult, and adult durations than Alpha-SS M. domestica, indicating fitness costs associated with most parameters. However, no significant differences were found between the strains in the following parameters: egg, pupa, and male preadult durations; adult preoviposition, total preoviposition, and oviposition periods; female ratio; and total generation time. Additionally, Alpha-RS M. domestica had a markedly lower intrinsic rate of increase, net reproductive rate, and finite rate of increase than Alpha-SS M. domestica. The results of this study suggest that alpha-cypermethrin resistance may lead to dominant fitness costs in M. domestica. Overall, these findings will aid in the development of rational control strategies for M. domestica as well as help to reduce pesticide pollution.

The effects of different Charleston pepper cultivars on the demographic parameters and the antioxidant levels of Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae)

Host plant diversity causes differences in the biology and adaptation of insects. In this study, variations in some biological properties and adaptive antioxidative response of Myzus persicae (Sulzer,1776) (Hemiptera: Aphididae) on five Charleston pepper, Capsicum annuum L. (Solanaceae) cultivars were investigated under laboratory conditions (25±1°C, 60±5% RH). The lowest intrinsic rate of increase (r = 0.193 d-1) of M. persicae was estimated in the tested cohort fed with the Kanyon cultivar, while the highest intrinsic rate of increase (r = 0.248 d-1) was found on the Tufan cultivar. The cohort fed with Safkan cultivar exhibited the highest levels of GST-CDNB and EST-PNPA at 562.80 and 207.64 nmol/mg protein, respectively, whereas the cohort fed with Kanyon cultivar showed the lowest levels at 317.04 and 132.14 nmol/mg protein, respectively. Analysis of life table parameters and enzymatic/non-enzymatic antioxidant levels of M. persicae showed that among the cultivars we tested, the Tufan cultivar was the most preferred host by M. persicae, while Kanyon cultivar was a less suitable host.

Study of life table and predation efficiency of Typhlodromus bagdasarjani (Mesostigmata: Phytoseiidae) fed Eotetranychus frosti (Trombidiformes: Tetranychidae) reared on different apple cultivars

ABSTRACT The life table parameters and predation rate of Typhlodromus bagdasarjani Wainstein & Arutunjan (Phytoseiidae) fed on Eotetranychus frosti (McGregor) (Tetranychidae) nymphs reared on four apple cultivars Kohanz Golab, Imperial Gala, Lebanon Red, and Granny Smith were studied under laboratory conditions. The longest developmental time of immature stages in females was observed on Kohanz Golab, and the shortest one was on Granny Smith. The fecundity ranged from 27.28 eggs on Golab Kohanz to 41.98 eggs on Granny Smith. The highest and lowest intrinsic rate of increase (r) were obtained on Granny Smith (0.254 day-1), and Kohanz Golab (0.136 day-1), respectively. The total prey consumption by all immature stages on Kohanz Golab, Imperial Gala, Lebanon Red, and Granny Smith was 36.93, 29.93, 27.36, and 21.30 prey, respectively. The total prey consumption by adult females was 424.70±24.41 prey on Kohanz Golab, 327.39±18.50 prey on Imperial Gala, 289.77±17.42 prey on Lebanon Red, and 218.50±14.64 prey on Granny Smith. The lowest fecundity and intrinsic rate of increase as well as the longest total life span of the predator on the resistant cultivar (Kohanz Golab) to E. frosti showed that integrated use of resistant cultivars and phytoseiid mites for control of spider mites needs more investigations.

Knockout of cryptochrome 1 disturbs the locomotor circadian rhythm and development of Plutella xylostella.

Cryptochrome 1 (CRY1) functions as a light-responsive photoreceptor, which is crucial for circadian rhythms. The identity and function of CRY1 in Plutella xylostella remain unknown. In this study, cry1 was cloned and identified in P.xylostella. Then, a cry1-knockout strain (Cry1-KO) of P.xylostella with a 2-bp deletion was established from the strain Geneva 88 (G88) using the CRISPR/Cas9 technology. No daily temporal oscillation of cry1 was observed in G88 and Cry1-KO, and cry1 mean daily transcription of Cry1-KO was lower than that of G88. Both G88 and Cry1-KO demonstrated rhythmic locomotion under the light/dark condition with Cry1-KO being more active than G88 in the daytime, whereas Cry1-KO completely lost rhythmicity under constant darkness. The developmental period of pre-adult of Cry1-KO was longer than that of G88; the lifespan of the Cry1-KO male adult was shorter than that of G88; the fecundity of Cry1-KO was lower than that of G88; and Cry1-KO showed lower intrinsic rate of increase (r), net reproduction rate (R0 ), finite increase rate (λ), and longer mean generation time (T) than G88. Our results indicate that cry1 is involved in the regulation of locomotor circadian rhythm and development in P.xylostella, providing a potential target gene for controlling the pest and a basis for further investigation on circadian rhythms in lepidopterans.

Methyl Jasmonate-Treated Pepper (Capsicum annuumL.) Depresses Performance and Alters Activities of Protective, Detoxification and Digestive Enzymes of Green Peach Aphid [Myzus persicae(Sulzer) (Hemiptera: Aphididae)

Methyl jasmonate (MeJA) is a phytohormone that has been used to artificially induce plant resistance against multiple arthropod herbivores. However, it is still uncertain whether MeJA can trigger pepper plant resistance against Myzus persicae (Sulzer) (Hemiptera: Aphididae) (green peach aphid, GPA). In this study, we assessed the effects of different concentrations (0, 0.008, 0.04, 0.2, 1.0, and 5.0 mM) of MeJA-treated pepper on the development and reproduction performance of GPA to identify an appropriate concentration for vigorous resistance enhancement. MeJA dose was applied on the pepper to investigate the changes in activities of protective enzyme (superoxide dismutase, SOD; catalase, CAT; peroxidase, POD and polyphenol oxidase, PPO), detoxification enzymes (acetylcholinesterase, AchE; glutathione S-transferase, GSTs; cytocrome P450, CYP450, and carboxylesterase, CarE), and digestive enzymes (protease, PRO and amylase, AMY) in GPA. The results showed that all concentrations of MeJA-treated pepper significantly suppressed GPA performance, wherein 0.2 mM was the optimal concentration, as it presented the lowest intrinsic rate of increase (rm), finite rate of increase (λ), and the highest population doubling time (Dt) values. Furthermore, the protective enzymes (SOD and CAT), detoxification enzymes (GSTs, CYP450, and CarE), and AMY activities increased significantly in MeJA-treated groups than the control group, while the POD and PPO activities were remarkly inhibited under 0.2 mM treatment. These findings indicate that exogenous spraying of 0.2 mM of MeJA significantly enhanced pepper resistance against GPA. The result of this study suggests MeJA application can be used as a promising strategy in integrative management of this insect pest.

Soil Fertilization With Medicinal Plant Processing Wastes Suppresses Tuta absoluta (Lepidoptera: Gelechiidae) and Aphis gossypii (Hemiptera: Aphididae) Populations.

Organic soil amendments can influence insect pest populations and the damage to plants they cause. In this study, the effects of medicinal plant processing wastes (MPPWs) applied as organic fertilizers on the host preference and performance of Tuta absoluta and Aphis gossypii were investigated on tomato and cucumber plants, respectively. Processing wastes of cumin, rosemary, thyme, artichoke, chamomile, fenugreek, and nettle were applied in four levels of 0, 20, 40, and 80 g dry matter/1kg culture media in pot experiments. Results showed the application of MPPWs, especially 80 g of nettle, reduced the number of T. absoluta eggs (from 0.8 to 0.4 egg/leaf) and their hatching percentage (from 90 to 76%). The highest and lowest number of aphids were observed in control (36 aphids/plant) and treated cucumbers with 80 g of cumin (18 aphids/plant). Also, the lowest intrinsic rate of increase (0.08 d-1) and net reproductive rate (20 offspring) of T. absoluta were observed in tomatoes fertilized with nettle. The highest and lowest net reproductive rate of A. gossypii were obtained on control and treated plants with 80 g of nettle, respectively. Results of damage assessment showed that the percentage of dry weight loss in the aphid-infested plants was reduced by the use of MPPWs, so that lowest weight loss was observed in the treatment with 80 g of nettle. In conclusion, soil amendment using MPPWs could result in lower pest populations and may improve plant tolerance to insect pest stress, thus these by-products could be considered a valuable tool in pest management.

Plant-mediated effects of water-deficit stress on the performance of the jujube lace bug, Monosteira alticarinata Ghauri (Hemiptera: Tingidae) on Jujube tree

Drought phenomenon as a consequence of climate change may become a major limiting factor for agricultural systems, and its impacts on plant-insect interactions are only partially understood. Addressing this issue, life-history responses of the jujube lace bug were evaluated on jujube tree under three water treatments (control, moderate and severe drought stress). Performance responses of the jujube lace bug were evaluated under controlled conditions using arenas consisting of jujube leaves inside Petri dishes. Plant biochemical measurements showed that leaf chlorophyll a, b, and total chlorophyll content, were higher in moderate water stress treatment than other treatments while Total Soluble Solids, total carbohydrate, and proline concentrations were increased in drought stress. Also, the lowest amount of carotenoid, phosphorous, sodium content was measured in severe drought stress treatment. The life history responses of Monosteira alticarinata showed that mean oviposition period and life span were statistically higher on moderate water stress than other treatments. The lowest intrinsic rate of increase (r), the finite rate of increase (λ), the net reproductive rate (R0), gross rate reproduction (GRR), total fecundity, and the highest doubling time (DT) were measured on severely drought stress treatment. An increase on the performance of the lace bug can be due to an increase on the chlorophyll, nitrogen, protein and free amino acids in moderate water stressed plants. However in severe stress it do worse. Overall, this study revealed that sap feeders benefit from moderate water stress.

Effects of Host Plants on the Growth, Reproduction, and Defense in Pea Aphids, Acyrthosiphon Pisum

Background: Pea aphids (Acyrthosiphon pisum) possess a weak immune system, but they can firmly mount immunological responses. However, the influence of different plants on their defense against different microbes remains largely unknown. In addition, no previous research has integrated the growth, reproduction, and defense responses of pea aphids feeding on different plants. Objective: This study aims to investigate the growth, reproduction, and defense responses of pea aphids feeding on different plants. Methods: Pea aphids were cultivated on both Medicago sativa and Vicia faba. Growth and reproduction were evaluated. Additionally, we monitored the survival and microbial loads of pea aphids after bacterial and fungal infections. Results : Pea aphids reared on M. sativa had lower growth, lower intrinsic rate of increase, and lower finite rate of increase when compared to aphids feeding on V. faba. The net reproduction was lower in aphids feeding on M. sativa, although the difference was not significant. The mean time of generation and pre-reproductive periods was longer for aphids reared on M. sativa than for aphids reared on V. faba. In the infection experiments, we found that aphid survival was not affected by the host plant. However, aphids reared on M. sativa generally harbored fewer microbial loads than those reared on V. faba. Conclusions: The growth and reproduction of pea aphids are affected by the host plant. Aphids feeding on different plants had different tolerances to microbial infections. Our study sheds light on improving biological control program for aphids.

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.

Residual toxicity and sublethal effects of fenvalerate on the development and physiology of Spodoptera exigua reared on different hosts

Beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is one of the most devastating pests of different key crops. The present study deals with the toxic effect of fenvalerate insecticide on the development, reproduction and the detoxification enzyme’s activity of S. exigua feeding on tomato, cabbage, and artificial diet. The developmental period of the second instar to adult emergence was prolonged (16.74 days) reared on tomato followed by cabbage (15.97 days) and artificial diet (15.62 days). The fecundity of S. exigua was lowest on the tomato plant (279 eggs), followed by an artificial diet (347 eggs), while the highest number of eggs was observed on cabbage after the control diet (421eggs). Moreover, the lowest survival rate of the second to the third instar, fourth to the fifth instar, and hatchability were recorded in insects reared on tomato (70.89%) compared to that reared on cabbage (77.08%) and artificial diet (79.66%). S. exigua reared on tomato had the lowest intrinsic rate of increase (r: 0.133) and the highest mean generation time (T: 31.36). Furthermore, detoxifying enzyme activity in S. exigua was much lower on tomato than on cabbage and diet. Moreover, the fenvalerate toxicity was synergized by either piperonyl butoxide (PBO) or S,S,S tributylphosphorotrithioate (DEF) due to the likely participation of monooxygenases or esterase; this suggests a general metabolic resistance. This research provides a solid base for devising an applicable and successful strategy for the controlling the resistance development in beet armyworms.

Characterization of resistance to rice leaf folder, Cnaphalocrocis medinalis, in mutant Samba Mahsuri rice lines

AbstractThe rice leaf folder, Cnaphalocrocis medinalis Guenée (Lepidoptera: Crambidae), an important foliage feeding insect in rice, Oryza sativa L. (Poaceae), is widely distributed throughout Asia, causing frequent outbreaks and considerable yield losses. Mutants of the rice strain Samba Mahsuri (MSM) represent unique plant material and are explored here for the first time for resistance to the rice leaf folder. Stringent rapid field screening for two consecutive seasons led to the identification of 10 lines as moderately resistant, with low damage area as well as low damage score. Upon assessment of various morphological traits potentially contributing to the resistance, damage area was negatively correlated with leaf length and positively with leaf width. Among the biochemical traits, leaf nitrogen content was positively correlated with leaf folder damage whereas silica was negatively correlated. Oviposition preference by leaf folder adult moths and larval settling preference were low on MSM 139 and MSM 127. We also observed that leaf folder larvae took more time for leaf selection (3.1 min) and making a primary fold (41.5 min), with more head swings (846) in moderately resistant MSM lines. Similarly, in these lines, leaf folders showed a low intrinsic rate of increase (rm = 0.15 females per female per day), low weekly multiplication rate (2.85), and low net reproductive rate (R0 = 137.5 females per female per generation) with increased generation time (T = 32.8 days) and doubling time (4.5 days), indicating their relatively poor population growth potential. Overall, the moderately resistant mutant lines we identified showed reduced ovipositional preference and larval settling preference, extended larval developmental period with low survival, reduced primary fold length, and an increased number of binds and head swings with a low intrinsic rate of increase resulting in reduced population build‐up. These lines possessing a good genetic makeup have a great potential to be used in breeding programs for the development of leaf folder resistant varieties.

Fitness comparison of Plutella xylostella on original and marginal hosts using age-stage, two-sex life tables.

The diamondback moth, Plutella xylostella, is an important agricultural pest that severely damages cruciferous vegetables. Although previously considered a threat only to Brassica species, P. xylostella has been observed to feed on noncruciferous vegetables. Here, we established a population of P. xylostella on the pea Pisum sativum (PxP population). We compared this PxP population's performance on the pea host plant to a population (PxR) reared on the original host plant radish (Raphanus sativus) for several generations using an age‐stage, two‐sex life table and analyzed the correlations between different fitness parameters. In the 1st generation of the PxP population, survival rate of immature stage was 17%, while the survival rate of PxR was 68%; the duration of the 4th larval instar (5.30 d) and mortality (25%) of this generation were significantly longer (2.8 d) and higher (1%) than that of PxR, respectively (both p < .001). Upon long‐term acclimation, the PxP fitness improved significantly, especially that the survival rate of immature stages increased to approximately 60% in the 15th, 30th, and 45th generations. However, PxP feeding on pea exhibited poorer fitness with longer larval developmental time, shorter total life span, lighter pupa, and lower fecundity in different generations compared with PxP feeding on radish. PxP feeding on pea also showed a significantly lower intrinsic rate of increase (r), net reproduction rate (R 0), finite increase rate (λ), and longer mean generation time (T) than PxP feeding on radish in all generations tested. Significant positive correlations were observed between pupal weight and female fecundity in pea‐fed populations, and between female longevity and female fecundity in pea‐fed and radish‐fed populations. Our findings suggest that P. xylostella adaptation to pea does not improve overall fitness compared with the original host radish, making pea a marginal host for P. xylostella.

Progeny fitness determines the performance of the parasitoid Therophilus javanus, a prospective biocontrol agent against the legume pod borer

Therophilus javanus (Bhat & Gupta) is an exotic larval endoparasitoid newly imported from Asia into Africa as a classical biological control agent against the pod borer Maruca vitrata (Fabricius). The parasitoid preference for the five larval instars of M. vitrata and their influence on progeny sex ratio were assessed together with the impact of larval host age at the time of oviposition on development time, mother longevity and offspring production. In a choice situation, female parasitoids preferred to oviposit in the first three larval instars. The development of immature stages of the parasitoid was observed inside three-day-old hosts, whereby the first two larval instars of T. javanus completed their development as endoparasites and the third larval instar as ectoparasite. The development time was faster when first larval instars (two- and three-day-old) of the host caterpillars were parasitized compared to second larval instar (four-day-old). The highest proportion of daughters (0.51) was observed when females were provided with four-day-old hosts. The lowest intrinsic rate of increase (r) (0.21 ± 0.01), the lowest rate of increase (λ) (1.23 ± 0.01), and the lowest net reproductive rate (Ro) (35.93 ± 6.51) were recorded on four-day-old hosts. These results are discussed in the light of optimizing mass rearing and release strategies.

Demography of Cacopsylla chinensis (Hemiptera: Psyllidae) Reared on Four Cultivars of Pyrus bretschneideri (Rosales: Rosaceae) and P. communis Pears With Estimations of Confidence Intervals of Specific Life Table Statistics.

The psyllid Cacopsylla chinensis (Yang & Li) (Hemiptera: Psyllidae) is a serious pest of pears in China. To determine and contrast the fitness of the psyllid on two endemic cultivars of Pyrus bretschneideri (i.e., BHXS and BSL) and two introduced cultivars of Pyrus communis (i.e., CB and CRB), we analyzed data on the development, survival, and fecundity from C. chinensis individuals reared on the four cultivars. The age-stage, two-sex life table theory was used in order to enable the inclusion of males in the analysis as well as a means of identifying the variation in developmental durations among individuals. Results indicated that C. chinensis can successfully develop and reproduce on all four pear cultivars. However, based on the lower preadult survival rate, longer preadult duration, longer total preoviposition period (TPOP), and lower fecundity that occurred on both cultivars of P. communis, these two cultivars are less favorable hosts for C. chinensis than the P. bretschneideri cultivars. The lower intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) on CB and CRB pears showed these two introduced cultivars are more resistant to C. chinensis than the endemic BHXS and BSL pears. These resistant cultivars would be appropriate candidates for managing C. chinensis. We used the bootstrap technique to estimate the uncertainty of the population parameters (r, λ, R0, etc.), while also demonstrating that it can be used for estimating the 0.025 and 0.975 percentile confidence intervals of the age of survival rate.

Comparative performance and digestive physiology of Diaphania indica (Lepidoptera: Crambidae) on Trichosanthes anguina (Cucurbitaceae) cultivars.

Diaphania indica (Saunders) (Lepidoptera: Crambidae) is an important phytophagous pest of Trichosanthes anguina L. in India. We studied life table parameters by age-stage, two-sex, amylolytic and proteolytic activities, and food utilization parameters of D. indica on the leaves of three T. anguina cultivars (Baruipur Long, Polo No. 1 and MNSR-1). Further, nutrients (total carbohydrates, proteins, lipids, amino acids and nitrogen) and antinutrients (total phenols, flavonols and tannins) in leaves were determined. The development time (egg to adult emergence) was the shortest on MNSR-1 (19.79 d) and the longest on Polo No. 1 (25.72 d). Fecundity was the highest and lowest on MNSR-1 (259 eggs) and Polo No. 1 (151.22 eggs), respectively. The lowest intrinsic rate of increase (rm) and net reproductive rate (R0) of D. indica on Polo No. 1 were 0.1112 d-1 and 27.22 offspring individual-1, respectively. The mean generation time (T) was the shortest on MNSR-1 (23.99 days) and the longest on Polo No. 1 (29.70 d). The larvae of D. indica fed with MNSR-1 had the highest level of amylolytic and proteolytic activities, and the lowest activities were in the larvae fed with Polo No. 1. The fifth-instar larvae fed with Polo No. 1 had the lowest consumption index and growth rate. The higher larval development time and lower fecundity of D. indica on Polo No. 1 were due to the lower level of nutrients and a higher level of antinutrients than other cultivars. Our results concluded that Polo No. 1 cultivar could be suggested for cultivation.

Role transformation of fecundity and viability: The leading cause of fitness costs associated with beta-cypermethrin resistance in Musca domestica.

Fitness is closely associated with the development of pesticide resistance in insects, which determines the control strategies employed to target species and the risks of toxicity faced by non-target species. After years of selections with beta-cypermethrin in laboratory, a strain of housefly was developed that was 684,521.62-fold resistant (CRR) compared with the susceptible strain (CSS). By constructing ≤ 21 d and ≤ 30 d life tables, the differences in life history parameters between CSS and CRR were analyzed. The total production numbers of all the detected development stages in CRR were lower than in CSS. Except for the lower mortality of larvae, all the other detected mortalities in CRR were higher than in CSS. ♀:♂ and normal females of CRR were also lower than those of CSS. For CRR, the relative fitness was 0.25 in the ≤ 21 d life table and 0.24 in the ≤ 30 d life table, and a lower intrinsic rate of increase (rm) and net reproductive rate (Ro) were detected. Based on phenotype correlation and structural equation model (SEM) analyses, fecundity and viability were the only directly positive fitness components affecting fitness in CRR and CSS, and the other components played indirect roles in fitness. The variations of the relationships among fitness, fecundity and viability seemed to be the core issue resulting in fitness differences between CRR and CSS. The interactions among all the detected fitness components and the mating frequency-time curves appeared to be distinctly different between CRR and CSS. In summary, fecundity and its related factors separately played direct and indirect roles in the fitness costs of a highly beta-cypermethrin-resistant housefly strain.

Peanut cultivars display susceptibility by triggering outbreaks of Tetranychus ogmophallos (Acari: Tetranychidae).

The peanut red spider mite, Tetranychus ogmophallos Ferreira and Flechtmann (Acari: Tetranychidae), is an important pest of peanut in Brazil and is considered a quarantine pest in other countries. This study investigates the development, reproduction, survival and life table parameters of T. ogmophallos on five peanut cultivars-three with high levels of oleic acid [high oleic] and recently released: Granoleico, IAC OL 3 and IAC 503; and two regular and previously used by farmers: Runner IAC 886, IAC Tatu ST 3-and two breeding lines (L. 8008 and L. 322) in the growth chamber. There were differences between the developmental times of all immature stages, the oviposition period, fecundity and adult longevity of T. ogmophallos reared on the peanut cultivars and breeding lines. The longest duration of the immature stage and lowest fecundity occurred on cultivars Granoleico and Runner IAC 886, and breeding line L. 322, which also displayed the lowest intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) and the shortest mean generation time (T). The highest fitness occurred on the IAC Tatu ST, IAC OL 3, IAC 503 and L. 8008. Our study shows that peanut cultivars belonging to the group with high oleic trait and recently released (IAC OL 3 and IAC 503) are susceptible to T. ogmophallos, except Granoleico, which is resistant. The regular and previously used cultivar Runner IAC 886 and breeding line L. 322 are resistant to the peanut red spider mite.

Fitness cost of nitenpyram resistance in the brown planthopper Nilaparvata lugens

A resistant strain of Nilaparvata lugens has been continuously selected in the presence of nitenpyram for 27 generations under laboratory conditions in order to study the fitness cost of nitenpyram resistance. The resistance to nitenpyram in N. lugens was at a high level (resistance ratio = 144.7-fold). Life-tables of the nitenpyram-resistant strain and the susceptible strain (SS) of N. lugens were studied by using the age-stage, two-sex life-table approach. Compared to the SS, the relative fitness of the resistant strain of N. lugens was 0.55, with a lower intrinsic rate of increase (r) and net reproductive rate (R0). Changes in some life-history traits of the resistant strain were also observed. The duration of the egg stage, the development times of the first-, third- and fourth-instar nymphs, the adult preoviposition period and the total preoviposition period of the resistant strain were significantly increased, whereas the longevity, egg survival rate and fecundity (eggs/female) (absolute fitness) were significantly decreased in the resistant strain of N. lugens. The lower intrinsic rate of increase (r) and net reproductive rate (R0) seemed to be largely due to number of eggs laid, developmental time and egg survival rate. These results showed that the development of nitenpyram resistance may lead to significant fitness costs in resistant populations of N. lugens. This study provided valuable information for facilitating the development of nitenpyram-resistance management strategies.