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

Effects of three different host plants on two sex life table parameters of the fall armyworm Spodoptera frugiperda

The fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) is a major phytophagous pest that invaded China in late 2018, posing a serious threat to local agricultural production. Therefore, we investigated the effects of maize, soybean, and sweet potato on the growth, development, and reproduction of S. frugiperda under laboratory conditions. The developmental period of the egg-larval stage was significantly longer when S. frugiperda fed on sweet potato (28.94 days) compared to maize (16.19 days) and soybean (17.82 days). Sweet potato feeding significantly prolonged the pupal period, but this effect was not observed in the adult stage. Spodoptera frugiperda larvae fed on sweet potato had the lowest pupal weight (116.18 mg) and pupation rate (68.19%). The mean fecundity of females significantly differed among the plants, with egg production being highest for insects fed on maize (996.17 eggs) and lowest for those fed on sweet potato (319.28 eggs). Spodoptera frugiperda fed on sweet potato exhibited the smallest net reproductive rate (47.892), lowest intrinsic rate of increase (0.083 day-1), lowest finite rate of increase (1.086 day-1), and longest mean generation time (46.806 days). Overall, S. frugiperda can survive and complete its entire life cycle on all three host plants.

Induced biochemical variations in maize parental lines affect the life table and age-specific reproductive potential of Spodoptera frugiperda (J.E. Smith)

In recent years, the fall armyworm, Spodoptera frugiperda has rapidly emerged as a global invasive pest, challenging the maize production and leading to considerable economic losses. Developing resistant hybrids is essential for sustainable maize cultivation, which requires a comprehensive understanding of resistance traits and the underlying mechanisms in parental lines. To address this need, the present study aimed to identify the sources of resistance, age and stage-specific effects and role of phytochemicals in plant defense against S. frugiperda in thirty diverse maize parental lines [17 female (A) and 13 male (R) lines]. The study revealed that the larvae fed on maize A-lines CML 565, AI 501, AI 544 and PDIM 639, and R-lines AI 125, AI 542, AI 155, AI 1100 and PML 105 exhibited a reduced intrinsic (r) and finite rate of increase (λ), and net (R0) and gross reproduction rates (GRR); while, increased mean generation time (T) and doubling time (DT). Among these, A-lines CML 565, PDIM 639 and AI 544, and R-lines AI 125, AI 155 and AI 1100 showed higher detrimental effect on reproductive value of S. frugiperda. Aforesaid A- and R-lines were also found with greater increase in insect-induced test phytochemicals compared to other lines, accounting for 25.0 to 72.8% variation in the life table parameters, indicating antibiosis effect on S. frugiperda. Among the test phytochemicals, tannins, CAT, PAL, TAL and APX inflicted greater effect, indicating their role in induced-biochemical defense against S. frugiperda.

Age-Stage, Two-Sex Life Table Analysis of Riptortus pedestris (Hemiptera: Alydidae) Across Different Soybean Varieties

Riptortus pedestris (Hemiptera: Alydidae) is an economically important pest of soybeans, significantly affecting their quality and market value. This study aims to evaluate the adaptability of R. pedestris to different soybean varieties and provide a foundation for selecting resistant varieties and developing effective integrated pest management strategies. Seven widely planted varieties (Beidou No. 3, Jiyu 47, Jiyu No. 80, Jiyu No. 90, Jiyu 203, Kangxianchong No. 6, and Kangxianchong 12) were selected for testing, and the developmental and population parameters of R. pedestris were measured using an age-stage, two-sex life table method. Notable differences were found in the developmental period, female longevity, and total preoviposition period (TPOP) of R. pedestris across diverse varieties. For those feeding on Kangxianchong 12, the nymph stage (14.73 ± 0.11 days), total longevity (37.35 ± 1.12 days), total female longevity (38.83 ± 1.80 days), and fecundity (38.86 ± 3.27 eggs per female) were all remarkably longer than on the other varieties. Additionally, the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and average generation time (T) of R. pedestris varied significantly between soybean varieties. The lowest r (0.0789 ± 0.0075 per day) and λ (1.0821 ± 0.0081 per day) values were recorded for Kangxianchong No. 6, while the highest were for Jiyu 47 (r = 0.0933 ± 0.0070 per day, λ = 1.0978 ± 0.0076 per day). The R0 and T values for R. pedestris on Kangxianchong 12 (R0 = 16.33 ± 3.24 offspring per female, T = 31.18 ± 0.79 days) were remarkably higher than those of the other six varieties, suggesting that Kangxianchong 12 and Jiyu 47 are preferred hosts, whereas Kangxianchong No. 6 is less preferred. These results provide valuable insights for optimizing soybean cultivation and managing R. pedestris.

Managing ecosystem services in oleaginous forests for bioenergy provision and climate change mitigation

Oleaginous forests provide diverse ecosystem services, including timber, seed yield (a vital feedstock for biodiesel production), and substantial carbon savings. These carbon savings encompass carbon sequestration related to timber growth and carbon savings resulting from substituting fossil fuel with biodiesel. However, oleaginous forests are vulnerable to seed wasp attacks (disservice), which significantly threaten both seed yield and carbon savings. Using an integrated ecological-economic model that includes Faustmann's Land Expectation Value model and a pest damage control model, we aim to understand the intricate relationship among multiple ecosystem services and disservices of oleaginous forests. The results reveal four distinct phases contingent on varying pesticide application rates: the pesticide under-use phase, substitution phase, complementary phase, and over-use phase. Notably, a potential avenue to minimize pest damage is identified during the complementary phase by reducing the optimal rotation age at the expense of decreased carbon sequestration and bioenergy provision, posing a challenge to climate change mitigation. These findings have implications for formulating policies to manage conflicting ecosystem services of energy forests, offering valuable insights into the intersection of sustainable forest management and climate policy.

Trypanosoma cruzi infection reduces the population fitness of Mepraia spinolai, a Chagas disease vector

The hematophagous insect Mepraia spinolai (Hemiptera: Reduviidae: Triatominae) is naturally infected with the protozoan parasite Trypanosoma cruzi, the agent of Chagas disease in humans. In this study, we compared the demographic parameters of M. spinolai with and without T. cruzi infection. We collected the immature life table data of 479 M. spinolai individuals of control cohort (reared on mice without T. cruzi infection) and 563 M. spinolai individuals of treatment cohort (reared on mice with T. cruzi infection). Nymphs were maintained in individual compartments inside a growth chamber (26°C; 65-75%) until adult emergence; moulting and survival were recorded daily. For the adult life table study of the control, we used 24 pairs of adults from the control cohort. For the adult life table study of T. cruzi-infected cohort, 25 infected females were paired with 25 males from the control cohort. Life table data were analysed using bootstrap-match technique based on the age-stage, two-sex life table. The preadult survival rate (0.5282) of the control cohort was significantly higher than that of the infected cohort (0.2913). However, the mean fecundity of reproductive females (Fr  = 22.29 eggs/♀) and net reproductive rate of population (R0  = 5.07 offspring/individual) of the 0.5th percentile bootstrap-match control cohort were not significantly different from those of the infected cohort (Fr  = 23.35 eggs/♀, R0  = 3.77 offspring/individual). Due to the shorter total preoviposition period and higher proportion of reproductive female, the intrinsic rate of increase (r = 0.0053 d-1 ) and finite rate of increase (λ = 1.0053 d-1 ) of control cohort of M. spinolai were significantly higher than those of the T. cruzi-infected cohort (r = 0.0035 d-1 , λ = 1.0035 d-1 ). These results suggest that T. cruzi infection reduces the population fitness of the Chagas disease vector M. spinolai.

Life table study of Spodoptera frugiperda at different wheat stages and the effect of larval population density on wheat yield

BACKGROUND

Spodoptera frugiperda is an invasive, widespread agricultural pest in China. However, there have been no reports assessing feeding damage on wheat caused by S. frugiperda. To clarify the fitness and potential damage of S. frugiperda to wheat, this study analyzed the population parameters of S. frugiperda fed on wheat in a laboratory and simulated the potential damage in field conditions.

RESULTS

The population parameters of S. frugiperda were compared using life tables on wheat at the seedling and adult plant stages. The adult female longevity of S. frugiperda varied from 12.29 days on seedling plants to 16.60 days on adult plants. Egg production was significantly higher when fed on wheat at the seedling stage (646.34 eggs) than when fed on adult plants (495.86 eggs). On wheat at the seedling and adult plant stages, the mean generation times were 35.42 and 38.34 days, respectively, and the intrinsic rates of increase were 0.15 and 0.14, respectively. Spodoptera frugiperda completed development and increased its population in wheat at both plant growth stages. In the field, the effect of different larval densities on the 1000-kernel weight of wheat was significantly different. An action threshold of 40 larvae per m2 was estimated, and the higher population densities caused a yield loss of 17.7%.

CONCLUSION

Spodoptera frugiperda can complete its life cycle on wheat at different stages. Wheat can serve as an alternative host for S. frugiperda. If S. frugiperda reaches 320 larvae per m2 density during wheat growth, it will cause yield loss exceeding 17%. © 2023 Society of Chemical Industry.

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.

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.

Oviposition Preference and Age-Stage, Two-Sex Life Table Analysis of Spodoptera frugiperda (Lepidoptera: Noctuidae) on Different Maize Varieties

Host plants play an important role in the growth, development, and reproduction of insects. However, only a few studies have reported the effects of maize varieties on the growth and reproduction of S. frugiperda. In this study, a free-choice test was used to evaluate the oviposition preferences of female adults on ten common maize varieties and ten special maize varieties. The population fitness of S. frugiperda on six different maize varieties was also examined using the age-stage, two-sex life table method. The results showed that S. frugiperda oviposited and completed its life cycle across all maize cultivars. Moreover, the S. frugiperda females exhibited a significantly higher oviposition preference on the special maize varieties than on the common maize varieties. The highest number of eggs and egg masses occurred on Baitiannuo and the lowest on Zhengdan 958. The egg + larval stage, preadult, pupal stage, adult, APOP, TPOP, and total longevity of S. frugiperda were significantly shorter on the special maize varieties than on the common maize varieties. The fecundity, oviposition days, pupal weight, and hatching rate of S. frugiperda were significantly higher on the special maize varieties than on the common maize varieties. Specifically, S. frugiperda had the highest fecundity, female, and male pupal weight on Baitiannuo. Moreover, the net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) of S. frugiperda were the greatest on Baitiannuo, whereas the shortest mean generation time (T) occurred on Zaocuiwang. The lowest R₀, r, and λ, and longest T occurred on Zhengdan 958, suggesting that Zhengdan 958 is a non-preferred host plant compared to the other tested maize varieties. The findings of this study can provide a reference for the rational planting of maize and provide basic scientific information for the management of S. frugiperda.

Effects of drought stress and plant cultivar type on demographic characteristics of the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

Drought is a substantial threat to cereal production under global climatic change scenarios, albeit its aftermath on arthropod pests is yet contentious. To address this issue, demographic characteristics of Metopolophium dirhodum (Walker, 1849) (Hemiptera: Aphididae) were studied on one drought-susceptible wheat cultivar and one drought-tolerant wheat cultivar under different water treatments. Some physiological and biochemical features of wheat cultivars including leaf soluble sugar and proline contents and antioxidant enzymes activities were also investigated. Significant differences occurred in the developmental period, survival, and fecundity of M. dirhodum between wheat cultivars under various water treatments. The impact of intermediate and severe water stress on M. dirhodum was neutral and negative for the tolerant cultivar and negative for the water-susceptible cultivar, respectively. Under severe water stress, on both wheat cultivars, the aphids had low net reproductive rates and finite and intrinsic rates of increase in comparison with those reared on unstressed plants. In total, drought resulted in lower growth of population and reduced survival of aphids. Hence, in the context of projected climatic changes, acute water deficiency could probably result in reducing the abundance and menace of outburst of M. dirhodum. However, it should be noted that the potential likelihood of M. dirhodum eruptions can be drastically affected by the degree of drought intensity and host plant cultivar.

The biological and physiological responses of Leptinotarsa decemlineata Say (Col. Chrysomelidae) to different potato cultivars

BACKGROUND

The use of pest-resistant or less susceptible plant varieties is of great importance for integrated pest management programs. This study was conducted to evaluate the resistance of seven potato cultivars to a major pest, namely the Colorado potato beetle (CPB), by measuring its bio-physiological aspects.

RESULTS

The longest developmental time and the lowest survival rate of CPB were detected on cultivar 'Manitou.' Although the larvae fed voraciously, the food conversion efficiency was the lowest on this cultivar leading to the lowest relative growth rate. Furthermore, larvae reared on Manitou had the lowest total protease activity and specific activity values of cathepsin B compared to the larvae reared on other cultivars. Additionally, the cluster analysis showed that the Manitou cultivar was the least suitable (partially resistant) CPB. Moreover, the results indicated that the protein content was the lowest in the Manitou cultivar; conversely, this cultivar was rich in polyphenol and flavonoid compared to Agria and Santae cultivars.

CONCLUSION

The overall results in this study indicated that the Manitou cultivar might be a good candidate to be incorporated into integrated pest management programs. © 2022 Society of Chemical Industry.

Improvement of Bemisia tabaci (Hemiptera: Aleyrodidae) Fitness on Chinese Kale upon Simultaneous Herbivory by Plutella xylostella (Lepidoptera: Plutellidae)

Simple Summary

Different herbivores feeding on the same plant can interact through plant-mediated effects. Cotton whitefly and diamondback moth are two of the most destructive pests in the world, and they often occur together in cruciferous plants. However, how the performance and fitness of them are affected when co-occurring in the same host plant remains unclear. The present study demonstrates that cotton whitefly has become a dominant competitor by gaining increased fitness benefits when it is mixed with DBM on the same host plant irrespective of sequences of their arrival, which may be one of the reasons for the rapid expansion and outbreak of the whitefly population worldwide.

Abstract

Bemisia tabaci and the diamondback moth (DBM), Plutella xylostella, are two major cosmopolitan pests that often occur together and cause severe economic losses to cruciferous crops. However, little is known about how they interact with each other. To determine the effects of defense responses induced by the two pests on the biology and population dynamics of the herbivores, we studied the performance and fitness of B. tabaci and DBM when they damaged Chinese kale simultaneously and in different orders. The results showed that DBM pre-infestation shortened the developmental duration, increased longevity, oviposition days, and fecundity of B. tabaci. Meanwhile, the intrinsic rate of increase (r), net reproductive rate (R₀) and finite rate of increase (λ) of B. tabaci increased significantly with dual infection as compared with only B. tabaci infestation. In contrast, B. tabaci pre-infestation reduced the longevity and oviposition days of DBM, but the population parameters r, R₀, and λ did not vary significantly compared with only DBM infestation. Thus, co-infestation of B. tabaci and DBM was beneficial to the performance of the B. tabaci population. The present findings highlight that B. tabaci has become a dominant competitor when mixing with DBM on the same host plant.

Host-Plant Variations Affect the Biotic Potential, Survival, and Population Projection of Myzus persicae (Hemiptera: Aphididae)

The green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), a polyphagous insect pest is a major threat to a wide range of crops worldwide. Aiming to evaluate the life history traits of M. persicae, feeding on different host plants, we used five vegetables: cabbage, Brassica oleracea (Brassicaceae); chinese cabbage, B. rapa (Brassicaceae); chili pepper, Capsicum annum (Solanaceae); crown daisy, Chrysanthemum coronarium (Asteraceae); and eggplant, Solanum melongena (Solanaceae). TWOSEX-MSchart software was used for the statistical analysis about the age-stage, two-sex life table theory. The highest fecundity (69.65 individuals) rate of M. persicae, intrinsic rate of increase (r = 0.425 d-1), finite rate of increase (λ = 1.531 d-1), net reproductive rate (R0 = 69.65 offspring), and shortest mean generation time (T = 9.964 d) were recorded on the chili pepper plant. Whereas, lower fitness occurred on cabbage. The findings attained from population growth parameters indicate that chili pepper is the most susceptible plant, while cabbage is resistant to aphids. Population projection results also supported this statement, as the final total population size on cabbage was significantly lower than other plants. The reported information would be useful for devising integrated pest management programs, particularly those involving M. persicae. This information also suggests the adaptability of M. persicae causing economic damage to these vegetable cultivars.

Antibiosis to Metopolophium dirhodum (Homoptera: Aphididae) in Spring Wheat and Emmer Cultivars

Yield losses caused by pests, including aphids, can be substantial in cereals. Breeding for resistance against aphids is therefore desirable for enhancing the economic and environmental sustainability of cereal production. The aim of our study was to reveal the degree of antibiosis against Metopolophium dirhodum (Walker) (Homoptera: Aphididae), in four cultivars of spring wheat, Triticum aestivum L. ('Alicia', 'Odeta', 'Libertina', 'Astrid'), and two cultivars of emmer, Triticum turgidum ssp. dicoccum (Schrank ex Schübler) Thell. ('Rudico', 'Tapiruz') (both Poales: Poaceae) under controlled laboratory conditions. Using age-stage, two-sex life table, we quantified responses of M. dirhodum to each cultivar and to project population growth. The spring wheat and emmer cultivars varied in their suitability to M. dirhodum. The cultivar most susceptible to M. dirhodum was the emmer cultivar 'Rudico'; the projected population size of M. dirhodum on this cultivar was one order of magnitude larger than those on other cultivars. The most resistant cultivar was the spring wheat cultivar 'Libertina'. Since emmer is commonly used as a gene source for breeding T. aestivum, we advocate that care be taken to avoid the transmission of genes responsible for suitability to aphids from emmer to T. aestivum.

Sublethal effects of three insecticides on fitness parameters and population projection of Brevicoryne brassicae (Hemiptera: Aphididae)

The cabbage aphid, Brevicoryne brassicae (L.), is one of the major insect pests of cole crops in Iran. In most instances outbreaks are normally kept under control by application of insecticides. In this study, the sublethal effects (LC30) of three insecticides, acetamiprid, buprofezin, and thiamethoxam-lambda cyhalothrin, (TLC) were evaluated on the population growth rate of the progeny of insecticide-treated cabbage aphid adults. The age-stage, two-sex life table method was used to analyze the collected data. The results indicated that the insecticide applications affected the duration of the preadult period, their survival, reproduction, life span/longevity, and consequently, the population growth rate of the F1 generation. The indicators of the greatest sublethal effects were noted in the progeny of the TLC-treated adults. These included the lowest net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and the longest mean generation time (T). The highest values of r, λ, R, and the lowest value of T occurred in the control group followed by, in order, the acetamiprid and buprofezin groups. These research findings will be useful in the development and implementation of future aphid management programs.

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.

The Population Growth of Spodoptera frugiperda on Six Cash Crop Species and Implications for Its Occurrence and Damage Potential in China

Simple Summary

The fall armyworm Spodoptera frugiperda is an invasive pest, which can cause severe economic losses by larvae feeding on a variety of crops. To develop effective control technology, it is particularly necessary to study the basic biology and ecology of this invasive insect. This experiment investigated the development, survival, and reproduction and population growth of S. frugiperda on six cash crop species. This study indicated that S. frugiperda fed on maize and wheat had shorter preadult developmental durations, higher preadult survival, greater pupal weights and higher fecundity compared to the other four plants. Moreover, although the young larvae of S. frugiperda feeding on Chinese cabbage had a high mortality rate, the old larvae were voracious, which might still cause economic losses to Chinese cabbage. Our results showed that S. frugiperda could cause great economic losses to these cash crops, which should attract the attention of agricultural management departments.

Abstract

Spodoptera frugiperda is a significant migratory invasive pest, identified as a serious threat to agricultural production and food security in China. However, to our knowledge, the effects of most host plants on the biological characteristics of S. frugiperda have not been well studied. To develop effective management strategies for S. frugiperda in its new invasive habitat, basic biological and ecological knowledge of this pest are crucial requirements. Here, we examined the effects of six cash crops maize, wheat, soybean, tomato, cotton and Chinese cabbage on the development, survival, fecundity of S. frugiperda by using the age-stage, two-sex life table. The preadult stage, adult preoviposition period and total preoviposition period of S. frugiperda were shortest on maize and wheat but were longest on tomato. Fecundity was greatest on maize and wheat but smallest on tomato. The highest intrinsic rate of increase, finite rate of increase, net reproductive rate and the shortest mean generation time were recorded on maize. This present study showed that S. frugiperda could cause great economic losses to these cash crops, which should attract the attention of agricultural management departments. Our findings provide useful information in predicting population dynamics and understanding the potential damage that could be incurred by S. frugiperda invasion.

Development, Reproduction, and Life Table Parameters of the Foxglove Aphid, Aulacorthum solani Kaltenbach (Hemiptera: Aphididae), on Soybean at Constant Temperatures

We investigated several characteristics of the development and reproduction of the aphid Aulacorthum solani raised on soybean (Glycine max) at 10 constant temperatures between 2.5 and 30 °C, and described the relationship between temperature and several critical biological characteristics using mathematical models. We found that A. solani could survive and reproduce on soybean at temperatures ranging from 5 to 27.5 °C. High fecundity was observed at temperatures from 12.5 to 20 °C. The lower developmental threshold and thermal constant for this species’ nymphal stages were estimated to be 5.02 °C and 131.2 degree-days, respectively, using a linear model. The upper developmental threshold was estimated to be 33.9 °C using the Lactin-2 model. The optimum temperature for nymphal development was estimated to be 26.9 °C. The maximum total fecundity was estimated as ca. 76.9 nymphs per adult at 18.1 °C. The daily fecundity sharply increased at earlier adult ages, and slowly decreased thereafter until final parthenogenesis occurred, over a range of temperatures from 12.5 to 25 °C. The maximum daily fecundity was estimated to be ca. 6.1 nymphs per adult per day for a 5.2 day old of adult at 21.3 °C using an age- and temperature-dependent model of adult fecundity. In terms of life table statistics, the intrinsic rates of increase and the finite rate of increase were both highest at 25 °C, while the net reproductive rate was highest at 20 °C.

The Survival and Reproduction of Rhopalosiphum padi (Hemiptera: Aphididae) on Different Plants: Exploring the Possible Host Range for a Serious Wheat Pest

Rhopalosiphum padi (L.) is one of the most economically important pests of wheat worldwide; however, the host ranges of R. padi remain unclear. Particularly, it is unknown which plants R. padi can survive and reproduce on after the harvest of crops. The results revealed that the survival, developmental times, longevity, and fecundity of the aphid varied among the 13 Gramineae weeds, with the life-history parameters significantly differing. The virginoparae could survive long-term and reproduce on 11 of the 13 weeds. Gramineae weeds can possibly play a significant role in the buildup of R. padi populations as reservoirs. The virginoparae could survive long term and reproduce on Iris lactea Pall. var. chinensis (Fisch.) Koidz (Liliflorae: Iridaceae), Iris tectorum Maxim. (Liliflorae: Iridaceae), Cyperus rotundus L. (Cyperales: Cyperaceae), and Brassica oleracea L. var. capitata (Rhoeadales: Cruciferae), but not on Fagopyrum esculentum Moench (Polygonales: Polygonaceae), F. tataricum (L.) Gaertn. (Polygonales: Polygonaceae), Chlorophytum comosum (Thunb.) Baker (Liliflorae: Liliaceae), and Ophiopogon japonicas (Thunb.) Ker-Gawl (Liliflorae: Liliaceae). Rhopalosiphum padi can survive and reproduce on non-Gramineae plants of different families. Detailed host range information would be helpful for more effective control of insect pests. The design and implementation of sustainable pest management strategies should consider the aphid population on weeds and other host plants.

Heat sensitivity of eggs attributes to the reduction in Agasicles hygrophila population

Agasicles hygrophila has been introduced worldwide as a control agent for the invasive weed Alternanthera philoxeroides. However, global warming has potential impact on its controlling efficacy. The aim of this research was to explore the primary factors responsible for the greatly reduced A. hygrophila population in hot summers. To imitate the temperature conditions in summers, different developmental stages of A. hygrophila were treated with high temperatures from 32.5 °C to 45 °C for 1-5 h. Based on the survival rate, the heat tolerance of each developmental stage was ranked from lowest to highest as follows: egg, 1st, 2nd, 3rd instar larva, adult and pupa. Eggs showed the lowest heat tolerance with 37.5 °C as the critical temperature affecting larval hatching. Heat treatment of the A. hygrophila eggs at 37.5 °C for 1 h decreased the hatch rate to 24%. Our results indicated that when compared with the control at 25 °C, 1 h treatment at 37.5 °C prolonged the duration of the egg stage, shortened the duration of oviposition and total longevity, and changed the reproductive pattern of A. hygrophila. The net reproductive rate, intrinsic rate and finite rate were all significantly reduced. The results suggest that low heat tolerance of the eggs was the major factor responsible for the reduction of A. hygrophila populations, and the key temperature was 37.5 °C. Therefore, appropriate measures should be taken to protect eggs in order to maintain the efficacy of A. hygrophila in the biological control of A. philoxeroides in hot summers.

Density-Dependent Demography and Mass-Rearing of Carposina sasakii (Lepidoptera: Carposinidae) Incorporating Life Table Variability

Carposina sasakii Matsumura is one of the most destructive fruit-boring pests of pome and stone fruit trees in eastern Asia. Because larvae complete their development inside a single fruit, larval density per fruit is a critical factor in their survival, development, and fecundity. The effect of larval density was examined to determine the ideal density for devising an economic and sustainable mass-rearing system for harvesting of C. sasakii. Mass production of insects of the same age of a specific stage is not only important in biological control, but also in pheromone extraction, culturing of entomopathogenic nematodes and fungi, etc. Life history data for six larval densities (1-5, 6-10, 11-15, 16-20, 21-30, and 31-40 larvae/apple) were collected at 25.5 ± 0.5°C, 75.0 ± 5.0% RH, and a photoperiod of 15:9 (L: D) h. Data were analyzed using the age-stage, two-sex life table. The results showed that the highest preadult survival rate (42.00%), fecundity (104.70 eggs), and population parameters (intrinsic rate of increase r = 0.0718 d-1, net reproductive rate R0 = 23.03 eggs, and finite rate of increase λ = 1.0744 d-1) were observed at a density of 1-5 larvae/apple. However, when the rearing costs and production rate were considered, the density of 16-20 larvae/apple was the most economical for mass-rearing C. sasakii in order to achieve a daily harvest rate of 1,000 pupae (from 273 apples per day). To ensure the sustainability of the mass-rearing system, we included the life table variability in the harvesting strategy.

Demographic characteristics and population projection of Phytonemus pallidus fragariae reared on different strawberry cultivars

The strawberry mite, Phytonemus pallidus fragariae (Banks) (Acari: Tarsonemidae), is one of the most important pests of greenhouse grown strawberry plants. Field grown strawberries may also be infested by the pest in high humid conditions. Life tables give the most comprehensive description of the development, survival, stage differentiation, reproduction and consequently population growth of a population, and thus it is an important base of population ecology and pest management. In this study, to provide a comprehensive evaluation of an ecology-based and cost-effective control program, life history and demographic parameters of the strawberry mite were studied. The experiment was conducted under laboratory conditions providing 20 ± 1 °C, 80 ± 10% RH and L16:D8 photoperiod. The data were analyzed based on the age-stage, two-sex life table theory. The population parameters net reproduction rate (R₀ = 6.14 offspring), intrinsic rate of increase (r = 0.1317 day^-1), and finite rate of increase (λ = 1.1407 day^-1) on cv. Aromas were lower than those on the other cultivars tested. Based on the population characteristics, Aromas is a less favorable cultivar for the population growth of strawberry mite.

Demography and Uncertainty of Population Growth of Conogethes punctiferalis (Lepidoptera: Crambidae) Reared on Five Host Plants With Discussion on Some Life History Statistics

The development, survival, and fecundity data of Conogethes punctiferalis (Guenée) (Lepidoptera: Crambidae) reared on chestnut (Castanea mollissima Blume), maize (Zea mays L.), sunflower (Helianthus annuus L.), hawthorn (Crataegus pinnatifida Bunge), and apple (Malus domestica Miller) were collected at 25 ± 1°C and 70 ± 5% RH. Raw data were analyzed and compared by using the age-stage, two-sex life table. The mean fecundity (F) was the highest (282.3 eggs per female) when larvae were reared on chestnut. The lowest mean fecundity (19.2 eggs per female) occurred on apple. The net reproductive rates (R0) were 134.52, 106.77, 30.29, 27.61, and 8.63 offspring on chestnut, maize, sunflower, hawthorn, and apple, respectively. The intrinsic rates of increase (r) were 0.1359, 0.1326, 0.0807, 0.0811, and 0.0448 d-1 on chestnut, maize, sunflower, hawthorn, and apple, respectively. Computer projections based on the age-stage, two-sex life table revealed the stage structure and variability of the population growth of C. punctiferalis. Our results demonstrated that although chestnut and maize were the most suitable host plants for C. punctiferalis, the moths were also able to develop and reproduce on sunflower, hawthorn, and apple.

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.

Demography and Mass-Rearing Harmonia dimidiata (Coleoptera: Coccinellidae) Using Aphis gossypii (Hemiptera: Aphididae) and Eggs of Bactrocera dorsalis (Diptera: Tephritidae)

We compared rearing Harmonia dimidiata (F.) (Coleoptera: Coccinellidae) on four combinations of Aphis gossypii Glover (Hemiptera: Aphididae), and eggs of Bactrocera dorsalis Hendel (Diptera: Tephritidae), using the age-stage, two-sex life table. The four combinations were: both larvae and adults were reared on aphids; larvae were reared on aphids and adults were reared on fresh fruit fly eggs; larvae were reared on lyophilized fruit fly eggs and adults were reared on aphids; and larvae were reared on lyophilized eggs and adults were reared on fresh eggs. The highest intrinsic rate of increase (r = 0.1125 d-1) and net reproductive rate (R0 = 260.7 offspring) were observed when both larval and adult stages of H. dimidiata were reared on A. gossypii. When B. dorsalis eggs were used as rearing media for larvae, adults, or both, the values of r and R0 were significantly decreased. The lowest values (r = 0.0615 d-1 and R0 = 38.6 offspring) were observed when both larvae and adults were reared entirely on B. dorsalis eggs. Despite the lower r and R0 values, our results showed that B. dorsalis eggs could be considered as an adequate, less expensive alternative diet for rearing H. dimidiata because of the time and labor savings resulting from the ease of preparation and the ability to store the eggs for timely usage. The mass-rearing analysis showed that the most economical rearing system was to rear larvae on A. gossypii and adults on B. dorsalis eggs.