Brachiaria ruziziensis responses to different fertilization doses and to the attack of Mahanarva spectabilis (Hemiptera: Cercopidae) nymphs and adults.

Cropping practices are necessary in order to help reduce the population of pest insect, such as the induction of resistance through fertilization. Therefore, this study aimed to assess alterations on the production and quality of Brachiaria ruziziensis when receiving the fertilization composed by the macronutrients NPK and/or exposed to the attack of Mahanarva spectabilis nymphs and adults. B. ruziziensis plants were fertilized according to the recommendation (R), half of the recommended fertilization (H), or non-fertilization (C). They were also exposed to different M. spectabilis nymph and adult densities. The damage, regrowth, and bromatological components were evaluated. The fertilization treatment promoted a higher M. spectabilis nymph survival on B. ruziziensis; however, it reduced the damage caused by the forage exposed to nymphs and adults of pest insect, and it did not alter the quality of the signal grass. Moreover, the fertilization treatment enabled forage recovery, even when exposed to 5 nymphs or 10 spittlebug adults.

Development of the spittlebug Mahanarva fimbriolata under varying photophase conditions.

The effects of varying photophase conditions on biological parameters of Mahanarva fimbriolata (Stal) (Hemiptera: Cercopidae), nymphs and adults were evaluated. Eggs of a late developmental stage were placed near sugarcane roots (cultivar RB739735) maintained in a greenhouse (21 ± 7 °C, 90 ± 10% RH). Nymphs and adults were exposed to the following photophase conditions: (a) 13:11 L:D as nymphs and adults, (b) 13:11 as nymphs and 12:12 as adults, (c) 12:12 as nymphs and adults, and d) 12:12 as nymphs and 13:11 as adults. Exposure of nymphs to 13 hr of light significantly reduced the duration of the nymphal stage and the number of nymphs that matured to adults. The duration of the nymphal stage was longer in individuals developing into females than in those developing into males. There was an increase in the longevity of adults kept at 13 hr of light since the nymphal stage. The average longevity of adult males and females was approximately the same. The sex ratio was similar under all photophase conditions. The life cycle of insects kept at 12 and 13 hr of light during nymphal and adult stages respectively was extended. The total life cycle was significantly longer in M. fimbriolata females than males. The different photophase conditions did not affect the reproductive potential of M. fimbriolata. Females produced more diapausing than non-diapausing eggs, except when under 13- and 12-hr light conditions. There was no significant difference in the number of diapausing and non-diapausing eggs produced by females under the other photophase conditions.

Biologia de Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) em abobrinha cultivar caserta (Cucurbita pepo L. ) em diferentes temperaturas / Biology of Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) on squash cultivar caserta (Cucurbita pepo L. ) in different temperatures

As cucurbitáceas apresentam grande demanda no mercado mundial e uma das principais pragas que atacam essas culturas é o pulgão Aphis gossypii. Assim, objetivou-se estudar aspectos da biologia desse afídeo em função da temperatura na cultivar de abobrinha Caserta (Cucurbita pepo L.). Utilizaram-se discos foliares (2,5cm de ∅) acondicionados, com a face abaxial para cima, em placas de Petri (5cm de ∅) contendo uma lâmina de ágar-água. Em cada placa foi deixada uma ninfa recém-nascida, acompanhandose o seu desenvolvimento ao longo de todo o ciclo de vida, em diferentes temperaturas (18, 21, 24, 27 e 30±1ºC), 70±10 por cento UR e fotofase de 12 horas. O delineamento foi inteiramente casualizado, com 60 repetições. Verificou-se que as temperaturas afetaram o desenvolvimento de A. gossypii. Menor duração do período ninfal e maior produção diária de ninfas foram observadas a 24 e 27ºC. A temperatura de 30ºC provocou efeito deletério, causando 68 por cento de mortalidade na fase ninfal.

The cucurbitaceous plants are always on demand in world market and one of the main pests on these crop is the aphid Aphis gossypii. This work aimed to study the biological aspects of A. gossypii on the Caserta (Cucurbita pepo L.) cultivar in different temperatures. To determine the biological aspects of A. gossypii, nymphs were kept on leaf disks (2.5 cm ∅) with the abaxial side up in Petri dishes (5 cm ∅) containing a thin layer of agar-water. Each dish contained one nymph of the first instar of the aphid. The development and the other biological parameters were evaluated in different temperatures (18, 21, 24, 27 e 30±1ºC), 70±10 percent RH and 12h photophase. The experiments were complete randomized design with 60 replicates. The results showed that the temperature influenced the development of A. gossypii. The shorter nymphal period and higher daily nymph s production were observed at 24 and 27 ºC. The temperature of 30 ºC was deleterius inducing to 68 percent of mortality at the nymphal stage of A. gossypii.