Brígida Souza

Suitability of leguminous cover crop pollens as food source for the green lacewing Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae)

Diversification of crops with species that provide suitable pollen for predators may reduce pest population on crops by enhancing predator effectiveness. In this paper we evaluated the suitability of leguminous cover crop pollens to the predatory green lacewing Chrysoperla externa (Hagen). The predator is commonly found in coffee agroecosystems and the plant species tested were pigeon pea and sunn hemp, which are used in organic coffee systems. Newly emerged females and males of C. externa were reared on diets containing pollen of pigeon pea, sunn hemp, or castor bean, used as a control. The reproductive success of C. externa was evaluated when females fed the pollen species and when honey was added to the diets, to verify the predator need for an extra carbohydrate source. Similar intrinsic growth rates were found for females fed on pigeon pea pollen and on sunn hemp pollen but these rates increased significantly when honey was added to the diets. Females fed with pigeon pea pollen plus honey and with sunn hemp pollen plus honey had higher intrinsic growth rates than those fed with castor bean pollen plus honey. Females fed on castor bean pollen only or on honey only, did not oviposit. Leguminous pollen species were equally suitable for C. externa especially when they were complemented with honey. The results suggest that to successfully enhance predator effectiveness, organic coffee plantation should be diversified with plant providing pollen in combination with plant providing nectar.

Seletividade de Inseticidas a Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae)

The objective of this work was to evaluate the effect the insecticides endosulfan (1.05 g a.i./L), esfenvalerate (0.075 g a.i./L), fenpropathrin (0.09 g a.i./L), trichlorfon (0.09 g a.i./L) and triflumuron (0.0375 g a.i./L), used to control Alabama argillacea (Hubner), on eggs and larvae of Chrysoperla externa (Hagen), under greenhouse conditions. Egg viability, duration of the embryonic period and survival of first-instar larvae ecloded from treated eggs were evaluated. For first, second and third-instar larvae treated with the insecticides, subsequent survival of the larvae and pupae, as well as viability of the eggs produced by the emerged adults, were evaluated. The insecticides esfenvalerate and triflumuron caused a significant increase in the embryonic period of C. externa. Endosulfan, fenpropathrin, trichlorfon and triflumuron were highly toxic to larvae, with mortality rates ranging from 71% to 100%. Esfenvalerate caused only about 20% mortality of the first- and third-instar larvae and 38% of the second-instar larvae. Besides causing low larval mortality, esfenvalerate did not affect pupae survival or the reproductive capacity of the adults in the studied period, thus showing good potential for use in integrated pest management in cotton crops.

Biologia e não-preferência para oviposição por Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae) em cultivares de algodoeiro

Os objetivos deste trabalho foram avaliar alguns aspectos biologicos das fases de ovo e de ninfa de Bemisia tabaci (Gennadius) biotipo B e avaliar a nao-preferencia para oviposicao em testes com e sem chance de escolha e sua correlacao com o numero e tipo de tricomas nas cultivares de algodoeiro (BRS Ipe, BRS 186-Precoce 3, BRS Acala, BRS Verde, BRS 200-Marrom, BRS Cedro, BRS Ita 90-2 e BRS Aroeira). Os experimentos foram realizados em câmaras climatizadas (28 ± 2oC, 70 ± 10% UR e fotofase de 14h), e em casa-de-vegetacao. A viabilidade dos ovos nao foi afetada pelas cultivares de algodoeiro, porem, a sobrevivencia no periodo de ovo a adulto foi influenciada pelo hospedeiro. Nao houve efeito das cultivares na duracao da fase de ovo, do segundo, terceiro e quarto instares nem no periodo de ovo a adulto. As ninfas que se desenvolveram na cultivar BRS Ipe tiveram o primeiro instar alongado, diferentemente daquelas desenvolvidas nas demais cultivares. As cultivares BRS Aroeira, BRS Verde e BRS Ita 90-2 apresentaram baixo numero de ovos nos testes com e sem chance de escolha, indicando um possivel mecanismo de resistencia, mas nao foi possivel estabelecer uma correlacao entre a densidade de tricomas e a nao-preferencia para oviposicao.

Resposta funcional de Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) alimentada com Schizaphis graminum (Rondani) (Hemiptera: Aphididae)

The functional response of Chrysoperla externa (Hagen) fed on Schizaphis graminum (Rondani) was studied under five densities of prey. The experimental design was completely randomized with five treatments and ten replications. The tests were conducted in growth chambers at 25 ± 1oC, RH of 70 ± 10% and photophase of 12 hours. Consumption increased in function of prey density in all instars. However, consumption tended to stabilize when a pre established average density of prey was offered, except for the first instar, which showed a constant increase in aphid consumption. The duration of the first and third instars and of the larval phase, as a whole, increased in function of the increased availability of prey. The duration of the second instar, however, decreased in function of increased prey availability. The results for the 1st, 2nd and 3rd instars and the larval phase showed a Type II functional response. Handling and searching time was evaluated for the average density of offered prey. The lowest searching time was verified for second instar larvae while the first instar showed the highest searching and handling time. Handling time dimi-nished progressively with larvae development.

Biologia de Aphis gossypii Glover, 1877 (Hemiptera: Aphididae ) em abobrinha cultivar caserta (Cucurbita pepo L.) em diferentes temperaturas

As cucurbitaceas apresentam grande demanda no mercado mundial e uma das principais pragas que atacam essas culturas e o pulgao Aphis gossypii. Assim, objetivou-se estudar aspectos da biologia desse afideo em funcao 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 agar-agua. Em cada placa foi deixada uma ninfa recem-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% UR e fotofase de 12 horas. O delineamento foi inteiramente casualizado, com 60 repeticoes. Verificou-se que as temperaturas afetaram o desenvolvimento de A. gossypii. Menor duracao do periodo ninfal e maior producao diaria de ninfas foram observadas a 24 e 27oC. A temperatura de 30oC provocou efeito deleterio, causando 68% de mortalidade na fase ninfal.

Efeitos de inseticidas usados na cultura do algodoeiro sobre Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae)

The physiological action of the insecticides trichlorfon, triflumuron, endosulfan, fenpropathrin, chlorpiryfos, tebufenozide and esfenvalerate to 2nd-instar larvae of Chrysoperla externa (Hagen) and subsequent effects on 3rd-instar larvae, pupae and adults were evaluated. The bioassays were carried out under greenhouse conditions. The effect on larvae fed on eggs of Anagasta kuehniella (Zeller) treated with the insecticides was evaluated, as well as the contact effect on 2nd-instar larvae kept on sprayed cotton plants. The survival percentage of individuals in the second- and 3rd-instar and in the pupae stage was determined. For adults, the daily and total production of eggs during 30 days, the viability and the fertility of eggs were evaluated. Endosulfan, tebufenozide and esfenvalerate were selective to 2nd-instar larvae by contact on sprayed plants as well as by suction of treated eggs. For 3rd-instar larvae, neither endosulfan, tebufenozide, esfenvalerate nor triflumuron were harmful. The survival of pupae from treated 2nd-instar larvae with fenpropathrin and tebufenozide was not affected. Trichlorfon, fenpropathrin and tebufenozide caused no reduction in the total number of eggs produced by females derived from 2nd-instar larvae fed with treated eggs of A. kuehniella. Females originated from larvae that kept contact with sprayed cotton plants with esfenvalerate, had no significant reduction in the total egg production. Although tebufenozide affected the reproductive traits of C. externa, it can be recommended for controlling the pests on cotton crop in association with inundative releases of this predator.

Influência de Diferentes Dietas em Fases Imaturas de Ceraeochrysa cubana (Hagen) (Neuroptera: Chrysopidae)

Larval and pupal development of the predator Ceraeochrysa cubana (Hagen) on different diets was evaluated. Larvae (20/treatment), were reared in laboratory at 20 ± 2 oC, 70 ± 10 % RH and 12 hours photophase on the following diets; eggs of Anagasta kuehniella; Toxoptera sp.; Pinnaspis sp.; eggs of A. kuehniella + Toxoptera sp.; eggs of A. kuehniella + Pinnaspis sp.; Toxoptera sp. + Pinnaspis sp.; and eggs of A. kuehniella + Toxoptera sp. + Pinnaspis sp. In all treatments, larvae fed on A. kuehniella eggs, showed shorter larval and pupal duration, higher number of adults, with viability of 75, 70, 95 and 80 % for treatments eggs of A. kuehniella, eggs of A. kuehniella + Toxoptera sp.; eggs of A. kuehniella + Pinnaspis sp., respectively. The diets with Toxoptera sp., Pinnaspis sp. and eggs of Toxoptera sp. + Pinnaspis sp. were the least suitable for the development of the predator with viability as low as 0; 5; and 15 %, respectively.

Eficiência de Chrysoperla externa (Hagen, 1861)(Neuroptera: Chrysopidae) no controle de Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae) em pimentão (Capsicum annum L.)

Avaliou-se a eficiencia de larvas de primeiro instar de Chrysoperla externa no controle Myzus persicae em pimentao, em experimentos realizados em câmara e sala climatizadas a 25 ± 1oC, UR de 70 ± 10% e fotofase de 12 horas. Larvas de C. externa recem-eclodidas foram liberadas em discos foliares, contendo 5; 10 ou 20 ninfas do afideo, acondicionados em placas de Petri. Em um segundo experimento, larvas do predador foram liberadas nas proporcoes 1:5, 1:10 e 1:20, em plantas inoculadas com 60; 100 e 140 ninfas do pulgao. O potencial predatorio de C. externa nos discos foliares foi influenciado pela densidade inicial do pulgao. A eficiencia do predador nas densidades de 5; 10 e 20 pulgoes foi de 100%; 96,7% e 79,3%, respectivamente. A eficiencia das larvas em eliminar as populacoes do pulgao nas plantas de pimentao variou em funcao do tempo. Na proporcao 1:5, a eliminacao das ninfas ocorreu entre um e dois dias apos a liberacao do predador, enquanto nas proporcoes 1:10 e 1:20 o periodo de quatro dias nao foi suficiente para que os pulgoes fossem eliminados. As larvas de C. externa quando liberadas nas tres proporcoes promoveram reducoes na populacao de M. persicae, se comparada a testemunha. No entanto, nas proporcoes 1:5 e 1:10 o predador se mostrou mais eficiente.

Aspectos biológicos de Chrysoperla externa (Hagen, 1861)(Neuroptera: Chrysopidae) em casa-de-vegetação

Objetivou-se estudar em casa-de-vegetacao alguns aspectos biologicos das fases imaturas e adulta de Chrysoperla externa (Hagen), alimentando suas larvas com ovos do piralideo Anagasta kuehniella (Zeller) e os adultos com dietas artificiais. O periodo embrionario foi determinado utilizando-se tubos de vidro de 2,5 x 8,5 cm, gaiola plastica transparente de 2,5 x 1,0 cm e tubo de pvc de 10,0 x 10,0 cm (com e sem umidificador). Os aspectos biologicos das fases de larva e pupa foram determinados confinando-as em tubos de vidro e gaiolas plasticas e os adultos em gaiolas de pvc de 10,0 x 10,0 cm, alimentando-os com levedo de cerveja + mel, extrato de soja + mel e polen + mel, nas consistencias semiliquida e pastosa. O periodo embrionario nao foi influenciado pelo tipo de recipiente, variando de 6,3 ± 0,2 a 7,6 ± 0,7 dias. Quando os ovos foram mantidos nas gaiolas plasticas, a viabilidade foi de 71,0%; contudo, naquelas de pvc e sem umidificador, obtiveram-se 88,0 ± 5,0%. A duracao do primeiro e segundo instares nao foi influenciada pelo tipo de recipiente; larvas de terceiro instar confinadas em tubos de vidro apresentaram uma duracao de 2,3 ± 0,1 dias e aquelas criadas em gaiolas plasticas de 1,6 ± 0,1 dias. A maior capacidade predatoria (2.630,0 ± 224,8 ovos) foi obtida para larvas de terceiro instar mantidas em tubos de vidro, constatando-se um consumo de 1.919,9 ± 151,6 ovos quando mantidas em gaiolas plasticas fixadas em folhas do algodoeiro. A duracao e a viabilidade dessa fase tambem nao foram influenciadas pelo tipo de recipiente de criacao, com uma variacao de 5,5 ± 0,4 a 6,1 ± 0,4 dias e 67,9 ± 3,9 a 74,4 ± 3,9%, respectivamente. A duracao e a viabilidade da fase de pupa nao foram afetadas pelo tipo de gaiola, constatando-se uma media de 13,5 ± 0,3 dias e 60% de pupas viaveis. Com relacao a fase adulta, verificou-se que a dieta constituida por levedo de cerveja + mel, na forma semiliquida ou pastosa, proporcionou os melhores resultados, obtendo-se uma fecundidade total de 387,8 ± 86,2 e 221,0 ± 41,4 ovos/femea, respectivamente. As femeas alimentadas com esse mesmo tipo de dieta na forma semiliquida foram as mais longevas, vivendo cerca de 45 dias.

Desenvolvimento e reprodução de Sipha flava (Forbes) (Hemiptera: Aphididae) em diferentes temperaturas

The aphid Sipha flava (Forbes) is a pest on elephant grass, but little is known about its biology. The objective of this work was to evaluate the temperature effects on the development, survival and reproduction of S. flava fed on Pennisetum purpureum. Twelve-hour-old nymphs were individualized on sections of elephant grass blades and maintained at 12, 16, 20, 24, 28 and 32 degrees C+/-1 degrees C, UR 70+/-10% and 12 h photophase. A total of 150 nymphs were used per treatment divided in 30 replicates, using a totally random design. The lower threshold temperatures (LTT) for first, second, third and fourth instars were 0.83, 1.05, 3.01 and 4.98 degrees C, respectively, indicating a change in thermal requirements as the development progress. The LTT for the whole nymphal stage was 2.08 degrees C, pointing to the tolerance of this species to low temperatures. A significant reduction in survival was observed at high temperatures (28 and 32 degrees C). Although the reproductive periods were longer and insects lived longer at 12 degrees C as compared with those at higher temperatures, the total fecundity was substantially reduced. The overall life cycle duration was almost twice as long at 12 degrees C than at 24 degrees C. The greatest daily production of nymphs and greatest number of nymphs produced overall occurred at 24 degrees C. The temperatures of 20 degrees C and 24 degrees C were more suitable to S. flava development and reproduction.