Host selection, development, survival, and reproduction of turnip aphid (Homoptera: Aphididae) on green and red cabbage varieties

Different Tea Germplasms Distinctly Influence the Adaptability of Toxoptera aurantii (Hemiptera: Aphididae)

Aphids are typical phloem-sucking insect pests. A good understanding regarding their feeding behavior and population dynamics are critical for evaluating host adaptation and screening of aphid-resistant resources. Herein, the adaptability of Toxoptera aurantii (Boyer) (Hemiptera: Aphididae) to different hosts was evaluated via electropenetrography and an age-stage, two-sex life table on six tea germplasms: Zikui (ZK), Zhongcha108 (ZC108), Zhongcha111 (ZC111), Qianmei419 (QM419), Meitan5 (MT5), and Fudingdabaicha (FD). Our findings revealed that the feeding activities of T. aurantii differed considerably among the host plants. T. aurantii exhibited significantly more pathway activities on ZK and FD than on the other hosts. However, the duration of feeding of T. aurantii on ZK phloem considerably decreased compared with those of the other germplasms. Life parameters indicated that T. aurantii exhibited the highest intrinsic rate of increase (r), net reproductive rate (R0), and finite rate of increase (λ) on MT5, and the maximum values of total longevity and oviposition period were recorded on FD; these variables were reduced significantly on ZK. The results of our study demonstrate that T. aurantii can successfully survive on the six tea germplasms; however, ZK was less suitable for T. aurantii and should be considered as a potential source of resistance in breeding and Integrated Pest Management.

Effects of host plant on the development and reproduction of Agrotis ipsilon (Lepidoptera: Noctuidae) on horticultural crops

One of cosmopolitan pest, Agrotis ipsilon (Lepidoptera: Noctuidae), causes serious economic damages in horticultural crops. This pest is difficult to manage and causes irreversible damage because its larvae stay in the ground at day and cut the plant stems at night. Thus, this study compared the host fitness of A. ipsilon among nine major horticultural crops in Korea. Among the nine crops, the population of A. ipsilon failed to complete its development in spinach, cucumber, melon, and kidney bean. The host effects on development and reproduction of A. ipsilon were further investigated in the remained five crops (i.e., napa cabbage, soybean, perilla, corn, and pepper). Host plants significantly (P < 0.05) affected the development-related factors (i.e., developmental time, survivorship, and weight) of A. ipsilon eggs, larvae, and pupae. They also affected the adult reproduction-related factors including preoviposition period, oviposition period and number, and longevity except for the prepupa stage. A positive relationship was found between biological factors (i.e., development- and reproduction-related factors). Among the nine crops in this study, napa cabbage showed the highest suitability for the A. ipsilon populations. These findings in this study would be helpful to understand the ecology and develop the management tactics of A. ipsilon in horticultural crops.

Comparative bionomics and life table studies of Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) on three cabbage varieties

Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) are important pests of brassica crops, causing significant yield losses on cabbage in Ghana. To inform the development of ecologically sound and sustainable pest management strategies for these pests, their biological and population growth parameters were studied on three cabbage varieties (Oxylus, Fortune, and Leadercross). The study was conducted in a screen house under ambient conditions at 30 ± 1°C and 75 ± 5% RH and 12:12 h photoperiod from September to November 2020. The parameters of the preadult developmental period, survival rates, longevity, reproduction, and life table were evaluated following the female age-specific life table. There were significant differences in the nymphal developmental time, longevity, and fecundity on the cabbage varieties for both aphid species. The highest population growth parameters, net reproductive rate (R₀), intrinsic rate of increase r, and finite rate of increase (λ) were recorded on Oxylus variety for both L. e. pseudobrassicae and M. persicae. The lowest was recorded on Leadercross variety for L.e pseudobrassicae and Fortune for M. persicae. The results from this study suggest that Leadercross is a less suitable host for L. e. pseudobrassicae and Fortune for M. persicae, thus, should be considered as less susceptible varieties for use in primary pest management by small-scale farmers or as a component of an integrated pest management strategy for these pests on cabbage.

Effects of Elevated CO2 on the Fitness of Three Successive Generations of Lipaphis erysimi

Simple Summary

Global warming caused by the increase in atmospheric CO₂ concentration is becoming a major environmental issue. Lipaphis erysimi is one of the most damaging pests of cruciferous crops worldwide, and L. erysimi has strong adaptability to the environment and reproductive capacity. The age-stage, two-sex life table is currently used by many researchers in place of the traditional age-specific life table, providing many details such as fitness and potential damage. In this study, the individual fitness and population dynamics parameters of three successive generations of L. erysimi were analyzed using the age-stage, two-sex life table. The results show that a high CO₂ concentration had a cumulative effect on the survival rate and fecundity of L. erysimi, and elevated CO₂ had a negative effect on the individual fitness parameters of L. erysimi. The life expectancy (e_xj) is significantly lower in elevated CO₂ than that in ambient CO₂ treatment in the three successive generations, indicating that L. erysimi was more sensitive to CO₂ concentration and the life of L. erysimi was shortened under elevated CO₂. Additionally, we can find that elevated CO₂ has a short-term effect on the population parameters, including the intrinsic rate of increase (r) and finite rate of increase (λ) in L. erysimi. Through the data from this experiment, we believe that the individual and population fitness of L. erysimi will be decreased under elevated CO₂, which indicates that the damage caused by L. erysimi may be reduced in the future with increasing CO₂ levels.

Abstract

To assess the effect of elevated CO₂ on the development, fecundity, and population dynamic parameters of L. erysimi, the age-stage, two-sex life table was used to predict the individual fitness and population parameters of three successive generations of L. erysimi in this study. The results show that a significantly longer total pre-adult stage before oviposition (TPOP) was observed in the third generation compared with the first generation of L. erysimi under the 800 μL/L CO₂ treatment. The fecundity is significantly lower in the 800 μL/L CO₂ treatment than that in the 400 μL/L CO₂ treatment in the third generation of L. erysimi, which indicates that elevated CO₂ had a negative effect on the individual fitness parameters of L. erysimi. Additionally, the life expectancy (e_xj) is significantly lower under the 800 μL/L CO₂ treatment than that under the 400 μL/L CO₂ treatment in the three successive generations. A significantly higher intrinsic rate of increase (r) and finite rate of increase (λ) were found in the second generation compared with those in the first and third generations of L. erysimi under the 800 μL/L CO₂ treatment. Moreover, significantly lower r and λ were observed under the 800 μL/L CO₂ treatment compared with those under the 400 μL/L and 600 μL/L CO₂ treatments in the first generation of L. erysimi, which indicates that elevated CO₂ has a short-term effect on the population parameters (r and λ) of L. erysimi. Our experiment can provide the data for the comprehensive prevention and control of L. erysimi in the future with increasing CO₂ levels.

Cheilomenes sexmaculata (Coccinellidae: Coleoptera) as a potential biocontrol agent for aphids based on age-stage, two-sex life table

The Zigzag ladybird beetle, Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae), is a biological control agent that feeds on a variety of aphid species. Life table and predation data of C. sexmaculata were collected under laboratory conditions at 25±2⁰C, 60±5% RH and L14: D10 h in connection with feeding on four different aphid species; Lipaphis erysimi (Kaltenbach), Myzus persicae (Sulzer), Aphis nerii (Boyer de Fonscolombe) and Diuraphis noxia (Mordvilko). Larval development of C. sexmaculata was long when fed on M. persicae (12.18 days) and shorter on D. noxia (10.64 days). The male’s lifespan was longer on M. persicae (26.70 days) and shorter on L. erysimi (23.67 days). Fecundity was maximum when the beetle was fed D. noxia (316.8 eggs/female) and minimum on M. persicae (199.1 eggs/female). Net reproductive rate, intrinsic rate of increase and finite rate of increase were highest on D. noxia with values of 158.4 (offspring individual^-1), 0.22 d^-1, and 1.24 d^-1, respectively whereas the respective parameters were lowest on L. erysimi (99.5 offspring individual^-1, 0.19 d^-1, and 1.20 d^-1, respectively). However, the mean of the generation (T) was shorter on A. nerii (22.48 d^-1) and longer on M. persicae (24.68 d^-1). Based on life table parameters obtained under laboratory conditions, the most appropriate host of C. sexmaculata was D. noxia. This study should help us to improve mass rearing and use of C. sexmaculata in the biological control of aphids on field and horticultural crops.

First Report and Distribution of the Indian Mustard Aphid, Lipaphis erysimi pseudobrassicae (Hemiptera: Aphididae) on Cabbage (Brassica oleracea var capitata) in Ghana

The presence of large colonies of aphids is associated with a devastating novel necrotic disease of cabbage (Brassica oleracea var. capitata) in Ghana that is thought to be of viral etiology. In this study, we used molecular taxonomic tools to identify the aphid species present on these diseased cabbage plants. This was confirmed using two key features for morphological identification, involving the length of cornicles and shape of cauda for the wingless forms of the aphids. Two species of aphids were identified and their distribution in Ghana indicated. One was the generalist aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) but the most abundant was the brassica specialist aphid, Lipaphis erysimi pseudobrassicae (Davis) (Hemiptera: Aphididae), which is one of the most destructive pests of brassica crops in some countries in Africa and other parts of the world. L. erysimi has been reported in Benin, Mali, South Africa, India, China, and United States, but this is the first formal report of L. erysimi pseudobrassicae in Ghana. The correct identification of L. erysimi is crucial, suggesting that it has recently become one of the most common species of aphid found on cabbage plants in Ghana.

Demographic Parameters of Lipaphis erysimi (Hemiptera: Aphididae) on Different Cultivars of Brassica Vegetables

Demographic parameters of the turnip aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae), which is a serious pest of Brassica crops worldwide, were evaluated on five major Brassica vegetables (three varieties of Brassica oleraceae (Linnaeus) (Brassicaceae: Brassicales); kohlrabi, cabbage and ornamental cabbage, and two subspecies of Brassica rapa (Linnaeus) (Brassicaceae: Brassicales); Chinese cabbage and bak choi). The study was carried out under laboratory conditions at 25 ± 1°C, 70 ± 5% RH and 16:8 (L:D) h. Preadult developmental time, survival rate, female longevity, reproduction, and life table parameters were evaluated according to the age-stage specific life table method. The highest population growth parameters, i.e., net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were recorded on kohlrabi (R0 = 30.45 offspring, r = 0.2174 d-1, λ = 1.2429 d-1). These parameters were the lowest on Chinese cabbage (R0 = 13.00 offspring, r = 0.1503 d-1, and λ = 1.1621 d-1) and bak choi (R0 = 16.30 offspring, r = 0.1614 d-1, λ = 1.1752 d-1). The results attained from population growth parameters, together with population projection estimation based on the age-stage, two-sex life table theory, indicated that both Chinese cabbage and bak choi were less suitable hosts for turnip aphids and should be considered as a possible source for developing resistance in breeding programs and integrated pest management strategies.

Age-Stage, Two-Sex Life Tables of the Lady Beetle (Coleoptera: Coccinellidae) Feeding on Different Aphid Species

Life table and predation data were collected for Coccinella septempunctata (Linnaeus) (Coleoptera: Coccinellidae) feeding on three different host aphid species, Aphis craccivora (Koch) (Hemiptera: Aphididae), Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae), and Myzus persicae (Sulzer) (Hemiptera: Aphididae), under laboratory conditions, using age-stage, two-sex life table. The preadult developmental period of C. septempunctata was the shortest on M. persicae (21.12 d) and the longest on A. craccivora (28.81 d). Net reproductive rate (R0) ranged from 77.31 offspring per individual on A. craccivora to 165.97 offspring per individual on M. persicae. Mean generation time (T) ranged from 39.10 d on M. persicae to 51.96 d on L. erysimi. Values of the intrinsic rate of increase (r) decreased in the order M. persicae, A. craccivora, and L. erysimi (0.1302, 0.0864 and 0.0848 d-1, respectively). The highest finite rate of increase (λ) was observed on M. persicae (1.1391 d-1) and the lowest was observed on A. craccivora and L. erysimi (1.0903 and 1.0885 d-1, respectively). This information will be useful in relation to the mass rearing of C. septempunctata in biological control systems.

Population Growth of Dysaphis pyri (Hemiptera: Aphididae) on Different Pear Cultivars With Discussion on Curve Fitting in Life Table Studies

Population growth parameters of the Dysaphis pyri (Boyer de Fonscolombe) (Hemiptera: Aphididae) were evaluated on four different cultivars (Coscia, Ankara, Williams, and Santa-Maria) of pear (Pyrus communis L.) under field conditions in the Van region of Turkey. Aphids were kept on leaves of 10-yr-old pear trees in Plexiglas clip-cells (20 mm in diameter and 10 mm in height, with the upper side covered with muslin). For the description of the stage differentiation during population growth, we analyzed raw data of developmental time, survival, and fecundity using the age-stage, two-sex life table to take the variable developmental rate among individuals into account. Results indicated that the Coscia and Ankara cultivars are less favorable hosts for D. pyri because of the longer preadult developmental time, higher preadult mortality rate, and lower total fecundity on these cultivars. The intrinsic rate of increase (r), the net reproduction rate (R0), and the finite rate of increase (λ) values were lower on the Coscia and Ankara cultivars. We discussed the application of the Weibull function, polynomial model, and Enkegaard model in life table studies. Because these models are often inaccurate in describing survival and reproduction parameters, we suggest that their application in life table research should be reevaluated.

Report of the turnip aphid, Lipaphis erysimi (Kaltenbach, 1843) from Missouri, USA

The turnip aphid, Lipaphis erysimi (Kaltenbach, 1843), is one of the most destructive pests in the United States. It has been reported in 33 states, but had not been reported in the state of Missouri. In this study we report this species for the first time in Missouri.

Demographic Assessment of Plant Cultivar Resistance to Insect Pests: A Case Study of the Dusky-Veined Walnut Aphid (Hemiptera: Callaphididae) on Five Walnut Cultivars

To provide a comprehensive evaluation of walnut cultivar resistance to the dusky-veined walnut aphid, Panaphis juglandis (Goeze), we collected the life table data of this aphid reared on five cultivars of walnut ('Akça I,' 'Chandler,' 'Fernette,' 'Fernor,' and 'Pedro') under field conditions. The raw data of the developmental time, survival rate, and fecundity was analyzed using the age-stage, two-sex life table to account for the variable developmental rate and stage differentiation among individuals. Due to the species' longer immature developmental time, shorter adult longevity, shorter reproduction period, and lower fecundity, the net reproduction rate (R0=5.9 offspring), intrinsic rate of increase (r=0.0983 d(-1)), and finite rate (λ=1.1034 d(-1)) were the lowest when aphids were reared on the Fernor cultivar, while those reared on Akça I exhibited the highest population parameters (R0=18.0 offspring, r=0.2031 d(-1), and λ=1.2252 d(-1)). Based on the population characteristics, Fernor is a less favorable cultivar for the development and reproduction of P. juglandis. We also demonstrated the advantages of using bootstrapping for the analysis of standard errors of developmental time, longevity, fecundity, and other parameters as well. Our results indicated that demographic analysis of pest development, survival, and reproduction based on the age-stage, two-sex life table offers a comprehensive assessment of pest growth potential on different crop cultivars.