Impact of citrus species on the biological characteristics and life table parameters of Eutetranychus orientalis (Klein) (Acari: Tetranychidae)

Biological characteristics and life table parameters of Eutetranychus orientalis (Klein) were revealed on four different citrus species: grapefruit (Citrus paradisi Macf. cv. Star Ruby), lemon (C. limon (L.) Burm. f. cv. Meyer), mandarin (C. reticulata Blanco cv. Okitsu) and orange (C. sinensis L. cv. Washington Navel) under laboratory conditions. Results show that oviposition period, fecundity, and life table parameters varied significantly depending on the host plant species. Furthermore, host plant species had little effect on immature development, except for the teleiochrysalis and total developmental period, which was significantly shorter on lemon (13.77 days for females, 12.67 days for males). Total mean numbers of eggs laid by E. orientalis was 15.92 on mandarin and 29.78 on lemon. In addition, intrinsic rate of increase (rm), net reproductive rate (R0), finite rate of increase (λ) and doubling time (DT) are 0.12 day–1, 10.41 ♀/♀, 1.13 day–1 and 5.59 days for lemon, 0.17 day–1, 22.36 ♀/♀, 1.19 day–1 and 4.04 days for grapefruit, respectively. However, shortest and longest mean generation times (To) were obtained at 18.26 days on orange and 19.37 days on grapefruit. Our results demonstrate that intergeneric differences of Citrus should be considered when determining E. orientalis population abundance and dynamics in field conditions.

Effect of Different Temperatures on the Life Table Parameters of Rhyzobius Lophanthae Blaisdell (Coleoptera: Coccinellidae)

The purple scale predator, Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) is known as coccidophagous ladybird predator, and effective against scales’ insects. The present study aimed to evaluate the optimum temperature for the species to be more efficient. In this study, the life table parameters of R. lophanthae were determined on different temperatures at 4, 16, 18, 20, 22, 24, 26, 28, 30 and 32 °C and 60% RH, by calculations using RmStat-3 software according to Euler-Lotka equation. The results showed that the intrinsic rates of increase (rm) were 0.016, 0.022, 0.030, 0.052, 0.056, 0.068, 0.120, 0.142, 0.132, 0.021 females/females/day, respectively, while the net reproductive rates (R0) were 7.082, 9.514, 11.960, 50.906, 54.150, 49.525, 56.883, 80.944, 31.149, 1.882 females/females/generation, respectively. The mean generation times (T0) were 125.966, 104.602, 84.009, 75.742, 71.511, 57.568, 33.801, 30.866, 25.978, 30.759 days, respectively. Total productivity rates (GRR) were 34.865, 39.210, 48.216, 201.990, 209.469, 166.207, 177.779, 303.751, 105.751, 12.622 egg/female, respectively. The study concluded that 26-30 °C was the optimum temperature range for the efficient role of R. lophanthae under laboratory conditions. From the results, it is still needed to do more studies on the interactions of pests, predators with environmental conditions.

Morphological, Molecular Characterization, Life Cycle And Age Specific Life Table Parameters of Coconut Rugose Spiralling Whitefly, Aleurodicus Rugioperculatus Martin: An Exotic Pest of India

The present study aimed at reporting the incidence of exotic pest on Coconut rugose spiralling whitefly, Aleurodicus rugioperculatus Martin in Tamil Nadu, India. The taxonomical, morphometric, molecular characterization, life cycle and age specific life table parameters of the exotic pest were studied on coconut during 2017-19. The results revealed that rugose spiralling whitefly (RSW) is an exotic and polyphagous in nature and had total life period of 56.33± 1.01 days which includes 6.9±0.88, 19.57±2.17, 10.9±0.78 and 26.00±2.34 days of egg, nymphal, pupal and adult period, respectively. The rugose spiralling whitefly male adult was 2.6300± 0.0596 mm in length and 2.1220± 0.0576 mm width and female adult were 3.1460± 0.0329 mm in length and 2.1654± 0.0246 mm width. A. rugioperculatus was bigger than other previously reported whiteflies in India. The operculum was wrinkled and having compound pores with dagger shaped axial pores. Ligula of A. rugioperculatus extended beyond vasiform orifice. The identity of the species was further confirmed through amplification of mitochondrial COI gene 249 bp was obtained for all the isolates which were sequenced. The sequenced DNA product was submitted to NCBI- Gen Bank (Accession No. MT540964, MT679537, MT679538, MT679539, MT679540 and MT682638). Since, it is a first study on the age specific life table parameters of A. rugioperculatus and the results revealed that the net reproductive rates (Ro) 24.08 females/female/generation, intrinsic rate of increase 0.0646/day, finite rate of Increase (λ) 1.066/ day, mean fecundity (F) 41.28 eggs/female and mean generation time (T) 49.25 days, respectively

Evaluating the effects of Bt protein Vip3Aa on immature Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

Background Genetically modified (GM) crops have become a common tool for managing insect pests of economic importance. However, before their commercialization, bio-safety evaluation on non-target arthropods such as pollinators and biological control agents is a pre-requisite to save services rendered by them in agro-ecosystem. Results In the present experiment, the potential adverse effects of Bt protein (Vip3Aa) were studied on the life table parameters (pupation and emergence rates, 7-day larval weights, larval development time, and adult weight) of a predatory beetle, Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) in the laboratory. P. japonica was exposed to Bt protein incorporated in synthetic diet at the rate of 200 µg/g of fresh weight of diet. Temporal stability, bioactivity and the uptake of insecticidal protein were confirmed by enzyme-linked immunosorbent assay and a sensitive insect bioassay. The results indicated that pupation and adult emergence rates did not differ significantly from that of negative control (pure synthetic diet). Similarly, the fresh weight of male and female adults emerged in Vip3Aa treatment (2.87 mg and 3.86 mg, respectively) did not vary significantly from that of the negative control treatment (2.66 mg, 3.75 mg). However, the time taken by the larvae to complete their development (12.70 days) was significantly extended than that of the negative control (10.21 days). In contrast, the tested life-table parameters of P. japonica were adversely affected when fed on synthetic diet containing boric acid (positive control) indicating experimental fitness to detect adverse effects. Conclusions On the basis of the results, it is suggested that GM crops expressing Bt protein (Vip3Aa) are safe for non-target insects such as P. japonica and are compatible with other biological programs for the integrated management of insect pests.

Lethal and sublethal effects of bifenazate on the biological parameters of Tetranychus truncatus Ehara (Acari: Tetranychidae)

Tetranychus truncatus Ehara (Acari: Tetranychidae) is one of the serious pests that infests different agricultural crops in field and greenhouse crops, and its distribution is limited to mostly Asian countries. The experiments were conducted to know the effectiveness of different concentrations of bifenazate against the T. truncatus, and to evaluate and compare the demographic parameters of T. truncatus on host plant Lablab purpureus (L.) Sweet (Fabaceae), which were obtained from females treated with bifenazate. The LC15, LC30, LC50 and LC90 values are determined through the bioassay from the results of the first application of bifenazate on adult females of T. truncatus. The LC15, LC30, LC50 and LC90 concentrations of bifenazate were 0.417, 1.028, 2.591 and 24.792 ml/l, respectively. The response of adult females against the two lethal concentrations (LC15 and LC30) was mostly alike but had a little bit difference. The differences in life table parameters were observed between control and treated spider mites. The results demonstrated that LC15 and LC30 of bifenazate could reduce the survival rate, oviposition period, fecundity and longevity of females of T. truncatus and it significantly affected the developmental times, especially larval duration and fecundity of T. truncatus. Life-table parameters of T. truncatus were much reduced in LC15 and LC30 compared to the control and their growth and other factors showed significant differences. The present study showed that the lower lethal concentration (LC15 and LC30) of the tested acaricide showed negative effects on survivorship and life-table parameters of the subsequent generation of T. truncatus.

Nondetrimental impact of two concomitant entomopathogenic fungi on life history parameters of a generalist predator, Coccinella septempunctata (Coleoptera: Coccinellidae)

The non-persistent impact of biocontrol agents can be revealed for pest control when associated entomopathogenic fungi (EPFs) negatively affect the natural enemies. In this assay, impacts of Beauvaria bassiana (Balsamo) Vuillemin, and Metarhizium anisopliae (Metschnikoff) Sorokin were studied for their compatibility or side effects on life table parameters of an important generalist predator, Coccinella septempunctata L. The results indicated non-significant impacts of both EPFs on life table parameters of C. septempunctata. The development time (egg-adult) was not significantly different in control (69.79 days) and EPFs treated C. septempunctata (69.35–80.07 days). Both fungi did not induce any significant changes in the fecundity, adult pre-oviposition period (APOP), total preoviposition period (TPOP), and mean generation time (T) as compared to control treatment. Similarly, no difference in fecundity rate of C. septempunctata was observed after EPFs treatment (287.7–288.5) compared to control (290.0). The highest net reproductive rate (R0) occurred in control (87.05 offspring individual−1) and M. anisopliae (86.31 offspring individual−1) as compared to B. bassiana treated beetles (76.97 offspring individual−1). The age-specific fecundity curves indicated that the C. septempunctata had a similar fecundity rate in both EPFs treatments and control. This study demonstrates no significant side effects of B. bassiana and M. anispoliae on the performance and biology of C. septempunctata. Considering the compatibility of both EPFs with C. septempunctata, their combinations can be recommended in various integrated pest management programs.

Temperature-based phenology model for predicting the present and future establishment and distribution of recently invasive Spodoptera frugiperda (J. E. Smith) in India

Fall armyworm, Spodoptera frugiperda (J. E. Smith) is a polyphagous and highly destructive invasive insect pest of many crops. It was recently introduced into India and widely reported in almost all parts of India. Development of a temperature-based phenology model for predicting its rate of development and distribution will help in understanding the establishment and further spread of introduced invasive insect pests. Development, survival and reproduction parameters of S. frugiperda at six constant temperature conditions (15, 20, 25, 27, 30 and 35°C) were investigated and further validated with data generated under fluctuating temperature conditions. The estimated lower developmental threshold temperatures were 12.1°C for eggs, 11°C for larvae, 12.2°C for pupae, 15.13°C for males and 12.66°C for females. Degree-day (DD) requirements for the development of the different stages of S. frugiperda were 50, 250 and 200 DD for egg, larva and pupa, respectively. The best-fitted functions were compiled for each life stage to yield a phenology model, which was stochastically simulated to estimate the life table parameters. The developed phenology model predicted temperature ranges between 27 and 30°C as favourable for S. frugiperda development, survival and reproduction. The results revealed that maximum net reproductive rate (215.66 females/female/generation) and total fecundity (981.08 individuals/female/generation) were attained at 30°C constant temperature. The mean length of generations decreased from 74.29 days at 15°C to 38.74 days at 30°C. The maximum intrinsic rate of increase (0.138 females/female/day) and shortest doubling time (4.9 days) were also observed at 30°C. Results of simulated life table parameters showed high temperature-dependent development of S. frugiperda and complete development within all the tested constant temperature ranges (15–35°C). Simulated life table parameters for predicting risk indices of S. frugiperda in India indicated a significant increase in activity indices and establishment risk indices with a higher number of generations during future (2050 and 2070) climatic change scenarios compared to present conditions. Our results indicate that India will be highly suitable for the establishment and survival of S. frugiperda in future time periods.