Exposure of insects and host plants to different concentrations of CO2 affects the performance of Mahanarva spectabilis (Hemiptera: Cercopidae) in successive insect generations.

The performance of three successive generations of Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) fed on four forages exposed to environments with different CO2 concentrations was evaluated. In the first bioassay, we utilized the following scenarios: A) plants and insects were kept at high and constant CO2 (700 ppm) and B) the insects were kept at CO2 700 ppm and fed on plants from the greenhouse (average of 390 ppm). In the second bioassay, we utilized the following scenarios: C) plants and insects were kept in a greenhouse and D) the insects were kept in the greenhouse and fed on plants kept at CO2 700 ppm. The survival and duration of the nymphal and adult stages and the number of eggs/female of M. spectabilis were evaluated. It was only possible to evaluate the cumulative effects of the increase of CO2 on three successive generations of M. spectabilis kept in a greenhouse, due to the reduced survival of the insects in the first generation in the laboratory. A greater direct than indirect effect of the CO2 level on the performance of M. spectabilis was observed. Furthermore, it should be considered that the effect of CO2 elevation on the survival, periods of development, and fecundity, when taken together, can significantly impact the population dynamics of M. spectabilis in future climate scenarios.

Pollen as a component of the diet of Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidade) / Pólen como componente da dieta de Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidade)

Abstract The properties of maize pollen in the diet of Doru luteipes were determined by biological responses of the predator feeding on natural preys and artificial diet. The biological parameters of D. luteipes fed on Spodoptera frugiperda (Smith, 1797) eggs, maize pollen, Rhopalosiphum maidis (Fitch, 1856) + maize pollen and R. maidis were assessed. The effect of pollen on artificial diet on the biological variables of the predator nymphs and adults were also evaluated. Time span of nymphal development was greater for D. luteipes exclusively fed on earwigs, with the lowest rate of nymph survival. However, maize pollen plus earwigs in the diet provided the predator´s highest survival rate, whilst percentage of fertile females was double when fed on diets composed of S. frugiperda and R. maidis eggs. Development period decreased when D. luteipes nymphs consumed artificial diet plus pollen but there were high fecundity rates (number of laying/female and total egg/female) and a greater percentage of fertile females when they were fed on maize pollen.

Resumo Os benefícios do pólen de milho na composição da dieta de Doru luteipes foram determinados por meio das respostas biológicas desse predador alimentado com presas naturais e dieta artificial. Inicialmente, avaliaram-se parâmetros biológicos de D. luteipes alimentados com: ovos de Spodoptera frugiperda (Smith, 1797), pólen de milho, pólen de milho e Rhopalosiphum maidis (Fitch, 1856) e R. maidis. Posteriormente, verificou-se o efeito da presença do pólen em dieta artificial nas variáveis ​​biológicas de ninfas e adultos do predador. O período de desenvolvimento ninfal foi maior para D. luteipes alimentado, exclusivamente, com pulgões, sendo esta dieta a que propiciou menor sobrevivência ninfal. No entanto, a adição de pólen de milho na dieta com pulgões proporcionou maior taxa de sobrevivência do predador e, o percentual de fêmeas que ovipositaram foi praticamente o dobro em relação às dietas compostas por ovos de S. frugiperda e R. maidis. Quando ninfas de D. luteipes consumiram a dieta artificial adicionada com pólen verificou-se redução no período de desenvolvimento ninfal e quando o pólen de milho foi fornecido apenas na fase adulta houve uma maior fecundidade (número de posturas/fêmea e total de ovos/fêmea) e porcentagem de fêmeas que ovipositaram.

How Do Collaria oleosa and Brachiaria spp. Respond to Increase in Carbon Dioxide Levels?

The current study determines the indirect effect of CO2 level increase on Collaria oleosa (Distant, 1863) (Hemiptera: Miridae) fed on Brachiaria spp. (Poaceae), at two trophic levels, and evaluates resistance to these forages against the insect pest. Mirid bug nymphs and host plant were maintained under four climate environments: (1) nymphs and plants kept at 400 ppm CO2 level; (2) nymphs kept at 400 ppm CO2 level and fed on plants grown at 700 ppm CO2 level; (3) nymphs kept at 700 ppm CO2 level and fed on plants grown at 400 ppm CO2 level; (4) nymphs and plants kept at 700 ppm CO2 level. A totally randomized design was employed with 50 replications. Mean duration and survival of each instar and nymphal phase of insect, subjected to different climate scenarios and food sources, were evaluated. High CO2 levels promote changes in the plant, which trigger changes in the biology of C. oleosa, especially when the insects are kept at the current CO2 level. Moreover, since longer developmental period and shorter survival rates will induce the reduction of the number of generations and number of specimens, it may be underscored that B. brizantha species resistance will be maintained in future climate scenarios. Similarly, genotypes of B. ruziziensis demonstrated that they will be resistant at current and future CO2 levels.

Pollen as a component of the diet of Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidade).

The properties of maize pollen in the diet of Doru luteipes were determined by biological responses of the predator feeding on natural preys and artificial diet. The biological parameters of D. luteipes fed on Spodoptera frugiperda (Smith, 1797) eggs, maize pollen, Rhopalosiphum maidis (Fitch, 1856) + maize pollen and R. maidis were assessed. The effect of pollen on artificial diet on the biological variables of the predator nymphs and adults were also evaluated. Time span of nymphal development was greater for D. luteipes exclusively fed on earwigs, with the lowest rate of nymph survival. However, maize pollen plus earwigs in the diet provided the predator´s highest survival rate, whilst percentage of fertile females was double when fed on diets composed of S. frugiperda and R. maidis eggs. Development period decreased when D. luteipes nymphs consumed artificial diet plus pollen but there were high fecundity rates (number of laying/female and total egg/female) and a greater percentage of fertile females when they were fed on maize pollen.

Biological Performance and Preference of Mahanarva spectabilis (Hemiptera: Cercopidae) for Feeding on Different Forage Plants.

The performance and preference of Mahanarva spectabilis (Distant) for feeding on different forage species were evaluated. The survival and duration of the nymphal period, longevity and fertility of adults, and food preferences (free choice) of adults of M. spectabilis were evaluated in a greenhouse trial, and food preferences of adults were also evaluated in laboratory tests without a choice of host plant. In the field, the numbers of plants with spittle masses were evaluated by forage sampling. Lower levels of nymph survival were observed in the greenhouse on Molasses grass, Jaraguá, Tanzânia, and Makueni. The duration of the nymphal period did not differ significantly on different forage species; however, the longevity and fertility of adults were significantly lower on Cynodon and Brachiaria decumbens Stapf. In the free-choice preference test, adult insects were attracted most strongly to B. decumbens and Jaraguá, with intermediate attraction to Brachiaria brizantha (Hochst ex A. Rich) Stapf and Pioneiro. In the test without host choice, insects exhibited lower excretion rates on Tanzânia, Cynodon, Jaraguá, B. brizantha, and Molasses grass, and those fed on Cynodon, Jaraguá, Molasses grass, and Makueni also exhibited reduced body mass. In the field, Pioneiro had the highest number of spittle masses, followed by Roxo de Botucatu. Thus, Molasses grass, Tanzânia, Makueni, and Jaraguá plants are less suitable food sources for M. spectabilis nymphs and adults. Additionally, although Jaraguá was less favorable to nymphs, it attracted food-seeking adults; hence, these plants have potential for use in control of M. spectabilis.

Induction of resistance of corn plants to Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) by application of silicon and gibberellic acid.

The aim of this study was to evaluate the effects of silicon application and administration of the phytohormone gibberellic acid on resistance of the corn plants to the fall armyworm (FAW), Spodoptera frugiperda, and their vegetative characteristics. We evaluated larval and pupal duration, survival and biomass, and adult longevity, malformation and fecundity of S. frugiperda after feeding on plant matter treated with silicon and/or gibberellic acid. The feeding preference of FAW first-instar larvae, the total leaf area consumed by the insects, and the vegetative parameters of corn plants were also evaluated. No significant differences were observed in the measured parameters of larval and pupal stages of S. frugiperda in response to silicon or gibberellic acid. In adult stage insects, the number of eggs per female was significantly reduced in insects derived from larvae fed plants treated with silicon or gibberellic acid. In a non-preference test, 48 h after release, caterpillars preferred control untreated plants and consumed less matter from plants that had received hormonal treatment (gibberellic acid). Gibberellic acid also altered the vegetative characteristics of plants, by increasing their height, shoot fresh and dry mass, and silicon content. We conclude that gibberellic acid can alter the vegetative characteristics and silicon uptake of corn plants, leading to a reduction in their consumption by S. frugiperda larvae and a decrease in female insect oviposition.

How will Mahanarva spectabilis (Hemiptera: Cercopidae) Respond to Global Warming?

The aim of this study was to determine the favorable constant temperature range for Mahanarva spectabilis(Distant) (Hemiptera: Cercopidae) development as well as to generate geographic distribution maps of this insect pest for future climate scenarios. M. spectabilis eggs were reared on two host plants (Brachiaria ruziziensis(Germain and Edvard) and Pennisetum purpureum(Schumach)), with individual plants kept at temperatures of 16, 20, 24, 28, and 32 °C. Nymphal stage duration, nymphal survival, adult longevity, and egg production were recorded for each temperature*host plant combination. Using the favorable temperature ranges for M. spectabilis development, it was possible to generate geographic distribution. Nymphal survival was highest at 24.4 °C, with estimates of 44 and 8% on Pennisetum and Brachiaria, respectively. Nymphal stage duration was greater on Brachiaria than on Pennisetum at 20 and 24 °C but equal at 28 °C. Egg production was higher on Pennisetum at 24 and 28 °C than at 20 °C, and adult longevity on Pennisetum was higher at 28 °C than at 20 °C, whereas adult longevity at 24 °C did not differ from that at 20 and 28 °C. With these results, it was possible to predict a reduction in M. spectabilis densities in most regions of Brazil in future climate scenarios.

How many adults of Mahanarva spectabilis (Hemiptera: Cercopidae) should be used for screening Brachiaria ruziziensis (Poales: Poaceae) resistance?

This study determined the number of spittlebug adults, Mahanarva spectabilis Distant (Hemiptera: Cercopidae), that should be used in selection tests of the forage grass, Brachiaria ruziziensis (Germain and Evrard). In this study, 0, 1, 2, 4, or 8 M. spectabilis adults were kept in plants for 4 or 8 d per experimental plot. After these periods, the insects were removed from the plants and chlorophyll content, damage score, dry weight, fresh weight, and percent dry matter of shoots were evaluated. Chlorophyll content decreased significantly with higher density of M. spectabilis in plants exposed to the pest for 4 or 8 d. Plants that were exposed to eight spittlebugs for 8 d showed a approximately 60% loss of chlorophyll content. When the forage was infested with eight adults for 4 d, the average damage score was 3 (50% of the leaf area was affected). The damage score and fresh and dry weights of the forage did not change depending on the exposure time of the plants to the spittlebugs. The percentage of dry matter of the plants infested was higher with the increase insect density and exposure time for all densities. Thus, the minimum recommended number is eight M. spectabilis adults for 4 d in resistance tests of B. ruziziensis to this pest species.

Spittle protein profile of Mahanarva spectabilis (Hemiptera: Cercopidae) fed various elephant grass genotypes.

An understanding of the interaction between spittlebugs and forage grasses is essential for establishing factors that favor productive pastures. In the present study, we evaluated the protein profiles of the spittle of Mahanarva spectabilis (Distant, 1909) (Hemiptera: Cercopidae) fed various elephant grass genotypes. Each plant was infested with a single fifth-instar M. spectabilis. After 24 h, samples of the spittle produced by each nymph were collected and stored at -20°C, after which their protein profiles were analyzed. The exclusivity or interactions of the proteins present in the spittle produced by the insects revealed the susceptibility of the tested genotypes. The results indicate that groups of genotypes show identical spittle protein profiles when subjected to attack by spittlebugs. Resistant and susceptible elephant grass genotypes exhibited high similarity indices within each group. The similarity index was low for the resistance control species (Brachiaria brizantha) compared with that of the tested elephant grass genotypes. Qualitative and quantitative studies of the proteins expressed in the most promising materials will be performed in an ongoing genetic improvement program seeking to develop genotypes resistant to spittlebugs, which are the main biotic pests of elephant grasses.

Genetic variability of Mahanarva sp (Hemiptera: Cercopidae) collected from different sites in Brazil.

Spittlebugs are the leading cause of damage to tall grasses. Annual losses are estimated to reach 2.1 billion dollars in sugarcane crops and grazing land throughout the world. Correct identification of these species is difficult due to similarities in color, body size and male genitalia. Molecular markers have been useful in the identification and assessment of genetic diversity of many species. We investigated the genetic diversity of the spittlebug species Mahanarva fimbriolata, M. spectabilis and M. liturata and looked for markers that could aid in their identification. DNA from 34 spittlebug specimens, collected from six different regions of Brazil (Brasília, Campo Grande, Valença, Presidente Prudente, Juiz de Fora, and Porto Alegre), was analyzed with 29 RAPD primers, generating 501 polymorphic markers. High genetic variability was found among individuals M. fimbriolata (0.37), M. spectabilis (0.18) and M. liturata (0.69). Species-specific molecular RAPD markers were identified for each of the three species; these could be used as auxiliary tools for their correct identification.