Scale insects (Hemiptera: Coccoidea) associated with arabica coffee and geographical distribution in the neotropical region

ABSTRACT Coffee is one of the most important Brazilian agricultural commodities exported, and Minas Gerais and Espírito Santo States are the main coffee producers. Scale insects are important coffee pests, and 73 species of Cerococcidae (3), Coccidae (18), Diaspididae (6), Eriococcidae (1), Ortheziidae (3), Pseudococcidae (21), Putoidae (2) and Rhizoecidae (19) have been associated with roots, branches, leaves, flowers and fruits of Arabica coffee in the Neotropics. Eight species were found associated with Arabica coffee in Minas Gerais and Espírito Santo States in this study, and Coccidae was the most frequent family. Coccus alpinus, Cc. celatus, Cc. lizeri, Cc. viridis, and Saissetia coffeae (Coccidae) were found in both states; Alecanochiton marquesi, Pseudaonidia trilobitiformis (Diaspididae), and Dysmicoccus texensis (Pseudococcidae) were only found in Minas Gerais. Alecanochiton marquesi and P. trilobitiformis are first reported in Minas Gerais, and Cc. alpinus in Espírito Santo, on Arabica coffee. All scale insect species were associated with coffee leaves and branches, except D. texensis, associated with coffee roots. Fourty seven scale insect species have been found occurring in Brazilian Arabica coffee, and in Espírito Santo (28) and Minas Gerais (23). Widespread and geographical distribution of each species found are discussed.

Effects of temperature on the feeding behavior of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) on Bt and non-Bt cotton plants

ABSTRACT The host acceptance behavior and environmental factors as temperature affect the feeding behavior of Lepidoptera pests. Thus, they must be considered in studies about the risk potential of resistance evolution. The current study sets the differences in the feeding behavior of neonate Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) larvae exposed to Bt and non-Bt cotton plants, under different temperatures and time gap after hatching. Two cotton cultivars were used: the Bt (DP 404 BG - bollgard) and the non-transformed isoline, DP 4049. We found that the feeding behavior of neonate A. argillacea is significantly different between Bt and non-Bt cotton. Based on the number of larvae with vegetal tissue in their gut found on the plant and in the organza as well as on the amount of vegetal tissue ingested by the larvae. A. argillacea shows feeding preference for non-Bt cotton plants, in comparison to that on the Bt. However, factors such as temperature and exposure time may affect detection capacity and plant abandonment by the larvae and it results in lower ingestion of vegetal tissue. Such results are relevant to handle the resistance of Bt cotton cultivars to A. argillacea and they also enable determining how the cotton seeds mix will be a feasible handling option to hold back resistance evolution in A. argillacea populations on Bt cotton, when it is compared to other refuge strategies. The results can also be useful to determine which refuge distribution of plants is more effective for handling Bt cotton resistance to A. argillacea.

Effect of temperature on the reproduction of Bracon vulgaris Ashmead (Hymenoptera: Braconidae), a parasitoid of the cotton boll weevil

Estudamos os efeitos da temperatura na reprodução de Bracon vulgaris Ashmead, ectoparasitóide do bicudo-do-algodoeiro, Anthonomus grandis Boheman, em câmaras climatizadas, em temperaturas constantes de 20, 25 and 30ºC, umidade relativa do ar de 70 ± 10 por cento e fotofase de 14 h. As fêmeas do parasitóide produziram mais ovos a 25ºC (124,65 ovos) do que aquelas expostas a 20 (43,40 ovos) e a 30ºC (49,60 ovos). O número médio de larvas parasitadas por fêmea de B. vulgaris a 25ºC(71,75 larvas) foi maior do que a 20ºC (31,40 larvas) e 30ºC (25,15 larvas). As taxas diárias de aumento (r m) foram -0,007 a 20ºC, 0,07 a 25ºC e 0,03 a 30ºC, indicando que a temperatura de 25ºC produziu aumento de 1100 e 133 por cento no valor de r m em relação às temperaturas de 20 e 30ºC, respectivamente. Nos programas de controle biológico do bicudo-do-algodoeiro, usando liberações inoculativas deve-se utilizar fêmeas adultasde B. vulgaris com aproximadamente 5 dias (a 25 ou 30ºC) ou 20 dias de idade (a 20ºC); quando usando liberações inundativas, utilizar fêmeas adultas de B. vulgaris , com idade entre 11 e 31 dias (a 20ºC); 9 e 29 dias (a 25ºC) ou 3 e 14 dias (a 30ºC).

This research studied the effect of temperature on the reproduction of Bracon vulgaris Ashmead, an ectoparasitoid of cotton boll weevil ( Anthonomus grandis Boheman) at constant temperatures of 20, 25 and 30ºC, 70 ± 10 percent RH and a photophase of 14 h. Females of the parasitoid produced a greater number of eggs when exposed to 25ºC (124.65 eggs) in relation to those exposed to 20 (43.40 eggs) and 30ºC (49.60 eggs). The number of parasitized larvae per female of B. vulgaris at 25ºC (71.75) was greater than at 20ºC (31.40) and 30ºC (25.15). The daily intrinsic rates of increase (r m) were - 0.007 at 20ºC, 0.07 at 25ºC and 0.03 at 30ºC, revealing that the temperature of 25ºC produced increases of 1,100 and 133 percent in the value r m in relation to temperatures of 20 and 30ºC, respectively. In programs of biological control of the boll weevil using innoculative releases, adult females of B. vulgaris with approximately five (at 25 or 30ºC) or 20 day old (at 20ºC) should be used; when using innundative releases, adult females of B. vulgaris , with ages between 11 and 31; 9 and 29 or 3 and 14 days, respectively, at 20, 25 or 30ºC should be used.

Effect of gossypol on survival and reproduction of the zoophytophagous stinkbug Podisus nigrispinus (Dallas)

Effect of gossypol on survival and reproduction of the zoophytophagous stinkbug Podisus nigrispinus (Dallas). Gossypol is a sesquiterpene aldehyde found in cotton plants conferring resistance against herbivory. Although the effect of this sesquiterpenoid on insect pests of cotton is known, the interaction of this compound with zoophytophagous predators such as Podisus nigrispinus (Dallas) (Hemiptera, Pentatomidae) has not been studied so far. Thus, the objective of this study was to evaluate the effect of the purified gossypol on nymphs and adults of P. nigrispinus. Nymphs and adults of this predator were fed on Tenebrio molitor pupae and supplemented with solutions of gossypol at concentrations of 0.00, 0.05, 0.10, and 0.20 percent (w/v) during the nymphal and adult stages or, only during the adult stage of P. nigrispinus. The nymphal stage of the predator was, on average, two days longer when suplemmented with gossypol. Emerged adults had lower fecundity and egg hatching, especially at the highest gossypol concentration (0.20 percent) ingested during the nymphal and adult stages. However, this predator was not affected when it ingested the compound only during the adult stage. P. nigrispinus can have delayed nymphal development and lower reproductive performance when ingesting the gossypol during the nymphal and adult stages, but only at higher concentrations of gossypol than that produced by cotton plants.

Efeito do gossipol na sobrevivência e reprodução do percevejo zoofitófago Podisus nigrispinus (Dallas). O gossipol é um aldeído sesquiterpeno produzido pelo algodoeiro que confere resistência contra a herbivoria. A interação deste sesquiterpeno com predadores zoofitófagos, como Podisus nigrispinus (Dallas) (Hemiptera, Pentatomidae), é inexistente apesar do reconhecido efeito do gossipol sobre insetos pragas do algodoeiro. Assim, este estudo avaliou o efeito do extrato de gossipol sobre ninfas e adultos de P. nigrispinus. O predador foi alimentado com pupas de Tenebrio molitor L. (Coleoptera, Tenebrionidae) e suplementado com soluções do gossipol nas concentrações 0, 0,05, 0,10 e 0,20 por cento (peso/volume) durante os estágios ninfal e adulto e somente durante o estágio adulto. A duração do estágio ninfal do predador foi em média dois dias mais longo quando suplementado com gossipol. Adultos oriundos de ninfas suplementadas com gossipol apresentaram menor fecundidade e viabilidade dos ovos, em especial na maior concentração (0,20 por cento). Contudo, adultos não foram afetados quando suplementados com gossipol somente durante este estágio. Os resultados demonstram que a ingestão prolongada do gossipol ocasiona efeito no desenvolvimento e reprodução do predador P. nigrispinus, porém somente em concentração superior àquela produzida naturalmente pela planta de algodão.

The density of females of Palmistichus elaeisis Delvare and LaSalle (Hymenoptera: Eulophidae) affects their reproductive performance on pupae of Bombyx mori L. (Lepidoptera: Bombycidae)

Palmistichus elaeisis Delvare and LaSalle (Hymenoptera: Eulophidae) is a gregarious and polyphagous parasitoid mainly of Lepidoptera pupae. The objective of this paper as to study the developent of parasitoid on Bombyx mori L. (Lepidoptera: Bombycidae) pupae exposed to one, nine, 18, 27, 36, 45 or 54 female P. elaeisis, respectively. The females of the parasitoid remained in contact with pupae for 24 hours in glass tubes (14.0 x 2.2 cm), packed in a climatic chamber regulated at 25 ± 2°C, 70 ± 10 percent relative humidity and photo phase of 12 hours. With the exception of density 1:1 (72.72 percent), in other densities parasitism was 100 percent. Adults of P. elaeisis did not emerge from pupae at densities of 1:1 and 9:1, but 100.0 percent of parasitoid emergence was observed at the density of 45:1 and 54.54 percent at 54:1. The duration of the life cycle of this parasitoid ranged from 20 to 28 days. P. elaeisis produced 49 to 589 descendants per pupa of B. mori. The sex ratio of P. elaeisis ranged from 0.93 ± 0.01 to 0.97 ± 0.01 without differences with 18, 27, 36, 45 and 54 females/host. This parasitoid should be reared with the density of 45 females per pupa of B. mori.

Palmistichus elaeisis Delvare e LaSalle (Hymenoptera: Eulophidae) é um parasitóide polífago, que inviabiliza, principalmente, pupas de lepidópteros. O objetivo desse trabalho foi estudar o desenvolvimento do parasitóide em pupas de Bobyx mori L. (Lepidoptera: Bombycidae) expostas a uma, nove, 18, 27, 36, 45 ou 54 fêmeas de P. elaeisis, respectivamente. As fêmeas do parasitóide permaneceram em contato com as pupas por 24 horas em tubos de vidro (14,0 x 2,2 cm), acondicionadas em câmara climatizada regulada a 25 ± 2°C, 70 ± 10 por cento de UR e fotofase de 12 horas. Com exceção da densidade 1:1 (72,72 por cento), nas demais densidades o parasitismo foi 100 por cento. Adultos de P. elaeisis não emergiram nas densidades de 1:1 e 9:1, mas observou-se 100 por cento de emergência do parasitóide na densidade 45:1 e 54,54 por cento em 54:1. A duração do ciclo de vida desse parasitóide variou de 20 a 28 dias. P. elaeisis produziu de 49 a 589 descendentes por pupa de B. mori. A razão sexual de P. elaeisis variou de 0,93 ± 0,01 a 0,97 ± 0,01 sem diferenças nas densidades de 18, 27, 36, 45 e 54 fêmeas/hospedeiro. Esse parasitóide deve ser criado na densidade de 45 fêmeas por pupa de B. mori.

Occurrence of Anopheles (Nyssorhynchus) rangeli (Gabaldon et al) and Anopheles (Nyssorhynchus) evansae (Brethes) (Diptera: Culicidae) in an Eutrophized Dam

This is the first record of immature stages of species belonging to the subgenus Nyssorhynchus (Blanchard) in eutrophized breeding habitats. Larvae of Anopheles (Nys.) evansae (Brethes), Anopheles (Nyssorhynchus) rangeli (Gabaldon et al), Culex nigripalpus (Theobald) and Culex quinquefasciatus (Say) (Diptera: Culicidae) were collected in a rural eutrophized dam in Rio de Janeiro State, in Southeastern Brazil. Eutrophication was substantiated by the low diversity of mosquitoes, the high incidence of Cx. quinquefasciatus (42 percent) and of Daphinia sp. and, the high levels of both organic nitrogen (0.28 mg/l) and total phosphorus (0.02 mg/l).

Progênie de Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) parasitando pupas de Bombyx mori L. (Lepidoptera: Bombycidae) de diferentes idades / Progeny of Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) parasitising pupae of Bombyx mori L. (Lepidoptera: Bombycidae) of different ages

Palmistichus elaeisis Delvare & LaSalle é um parasitóide pupal natural de pupas de lepidópteros desfolhadores de eucalipto e é considerado um promissor agente de controle biológico. No entanto, o desenvolvimento de técnicas de criação eficientes desse inimigo natural é inicialmente necessário para que ele possa ser utilizado em programas de controle biológico. Pupas de Bombyx mori L. são hospedeiras alternativas em potencial para criação massal de P. elaeisis. Por isto, nós avaliamos a idade mais suscetível do hospedeiro e os efeitos da idade do parasitóide na produção de progênie de P. elaeisis. Pupas de B. mori com 24, 48, 72 ou 96h de idade foram expostas a fêmeas de P. elaeisis de mesmas idades. A duração do ciclo de vida (ovo-adulto) de P. elaeisis não foi afetada pela idade das fêmeas, entretanto, a idade do hospedeiro afetou o desenvolvimento do parasitóide. O melhor parasitismo foi obtido com fêmeas do parasitóide com 72h a 96h e pupas de B. mori com 48h a 72h de idade, que permitiram a elevação da progênie de P. elaeisis.

Palmistichus elaeisis Delvare & LaSalle is a natural pupal parasitoid of eucalyptus defoliator lepidopterans and is considered a promising biocontrol agent. However, the development of efficient rearing techniques for this natural enemy are first required before it can be used in biocontrol programs. Bombyx mori L. pupae are potential alternative hosts for this parasitoid mass rearing, and they are easy to rear. Therefore, we investigated the most suitable host age and the effects of parasitoid age on progeny production of P. elaeisis. B. mori pupae, 24h-, 48h-, 72h- or 96h-old were exposed to P. elaeisis females of similar age. The duration of the life cycle (egg-adult) of P. elaeisis was not affected by the age of the parasitizing female; however, the host age affected parasitoid development. The best parasitization was obtained for 72h- to 96h-old parasitoid females when offered to 48h- to 72h-old host pupae, allowing the synchronized rearing of a large number of P. elaeisis offspring.

Mortality of the defoliator Euselasia eucerus (Lepidoptera: Riodinidae) by biotic factors in an Eucalyptus urophylla plantation in Minas Gerais State, Brazil

Euselasia eucerus (Hewitson, 1872) (Lepidoptera: Riodinidae) is a Brazilian native species commonly found in Eucalyptus plantations. Biotic mortality factors of this defoliator were studied in a Eucalyptus urophylla plantation in Minas Gerais State, Brazil aiming to identify natural enemies and their impact on this insect. Euselasia eucerus had biotic mortality factors during all development stages. The most important were Trichogramma maxacalii Voegelé and Pointel, 1980 (Hymenoptera: Trichogrammatidae) during egg stage (48.9 percent), a tachinid fly (Diptera: Tachinidae) during larval stages (10 percent) and Itoplectis sp. (Hymenoptera: Ichneumonidae) during pupal stage (52.2 percent). The parasitism rate was higher in the basal part of the plant canopy (37.8 percent).

Euselasia eucerus (Hewitson, 1872) (Lepidoptera: Riodinidae) é uma espécie brasileira nativa, comumente encontrada em plantios de Eucalyptus. Um estudo da mortalidade por fatores bióticos desse desfolhador foi feito em um plantio de Eucalyptus urophylla no Estado de Minas Gerais, Brasil, com o objetivo de identificar os inimigos naturais e seu impacto sobre esse lepidóptero. Euselasia eucerus possui fatores bióticos de mortalidade durante todas as suas fases de desenvolvimento. Os mais importantes foram Trichogramma maxacalii Voegelé e Pointel, 1980 (Hymenoptera: Trichogrammatidae) durante a fase de ovo (48,9 por cento), um Diptera: Tachinidae durante a fase de larva (10 por cento) e Itoplectis sp. (Hymenoptera: Ichneumonidae) durante a fase pupal (52,2 por cento). A taxa de parasitismo foi mais elevada na parte basal de plantas de eucalipto (37,8 por cento).

Note on gynandromorphism in the eucalyptus defoliator Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae)

The brown moth Thyrinteina arnobia (Stoll, 1872) (Lepidoptera: Geometridae) is an important pest in Brazilian eucalyptus plantations. A gynandromorph individual of T. arnobia was found in a population of this pest in a laboratory rearing and it is described.

A mariposa marrom Thyrinteina arnobia (Stoll, 1872) (Lepidoptera: Geometridae) é uma praga importante em plantios de eucalipto no Brasil. Um indivíduo ginandromorfo de T. arnobia foi encontrado em uma população desta praga em criação de laboratório e descrito nesta nota.

Prey captured and used in Polistes versicolor (Olivier) (Hymenoptera: Vespidae) Nourishment

The social wasps are predators of many insect species and the study of their preys can reveal the potential of these natural enemies in biological control programs. A total of 240h of collections of preys in 32 nests of Polistes versicolor (Olivier) was carried on in Juiz de Fora, Minas Gerais State, Brazil, from March 2000 to February 2001. The preys captured by P. versicolor were mainly those from the orders Lepidoptera (95.4 percent) and Coleoptera (1.1 percent) while 3.4 percent of them were not identified. Chlosyne lacinia saundersii Doubleday & Hewitson (Lepidoptera: Nymphalidae) was the most collected prey (13.5 percent). The total of 4,015 preys was estimated to be captured per colony of P. versicolor during one year. The species can be used in integrated pest management of herbivorous insects, especially defoliating caterpillars.

As vespas sociais são predadoras de muitas espécies de insetos e o estudo de suas presas pode revelar seu potencial para programas de controle biológico de pragas. Foram realizadas 240h de coleta de presas em 32 colônias de Polistes versicolor (Olivier) no município de Juiz de Fora, MG, de março de 2000 a fevereiro de 2001. As presas capturadas por P. versicolor foram, principalmente, das ordens Lepidoptera (95,4 por cento) e Coleoptera (1,1 por cento) além de 3,4 por cento de indivíduos não identificados. A espécie mais coletada foi Chlosyne lacinia saundersii Doubleday & Hewitson (13,5 por cento) (Lepidoptera: Nymphalidae) e o número total estimado de presas capturadas por colônia de P. versicolor foi de 4.015 indivíduos por ano. Isso mostra que a espécie pode ser utilizada em programas de manejo integrado de pragas de insetos herbívoros, principalmente lagartas desfolhadoras.

Main lepidopteran pest species from an eucalyptus plantation in Minas Gerais, Brazil

Lepidoptera species were monitored in a plantation of Eucalyptus grandis in the Municipality of Bom Despacho, State of Minas Gerais, Brazil from March 1987 to February 1992. A total of 547 species were collected and divided in: primary pests: 13; secondary pests: 20; species without defined importance to eucalyptus: 79; and non-identified species: 435. These four groups had a mean of 5231.29; 338.18; 438.16 and 2222.87 individuals with a total of 8229.87 individuals collected per trap. The number of species without defined importance to eucalyptus, and non-identified species, increased during the collecting period of five years while those of primary and secondary pests showed similar numbers in all years. The most collected primary pests Thyrinteina arnobia Stoll and Stenalcidia sp. (Geometridae) showed higher frequencies during the driest and coldest periods of the year, whereas Psorocampa denticulata Schaus (Notodontidae) was most frequent during periods of higher rainfall. Species of groups III and IV increased in diversity with eucalyptus age. This area has a high probability of outbreaks of eucalyptus defoliating caterpillars, especially T. arnobia. For this reason, lepidopteran pests should be monitored in this plantation during the driest and coldest periods of the year, when they can reach population peaks.

De marzo de 1987 a febrero de 1992 se realizó un monitoreo con trampas luminosas en plantaciones de Eucalyptus grandis en Bom Despacho, Minas Gerais, Brasil. Se recolectaron 547 especies del orden Lepidoptera: plagas primarias: 13; plagas secundarias: 20; especies sin importancia definida para el cultivo de eucalipto: 79; y especies no identificadas: 435. Estos cuatro grupos tuvieron medias de 5231.29; 338,18; 438.16 y 2222.87 individuos por trampa respectivamente, para un total de 8229.87 lepidopteros recolectados por trampa. Durante los cinco años hubo un aumento del número de especies de los grupos III y IV. Las plagas primarias con mayor número de individuos fueron Thyrinteina arnobia Stoll y Stenalcidia sp. (Geometridae), con las mayores frecuencias para los meses más secos y fríos del año. Psorocampa denticulata Schaus (Notodontidae) fue más abundante en los periodos más lluviosos. La probabilidad de brotes de larvas desfoliadoras de eucalipto, principalmente T. arnobia, es alta en la región. Se recomienda hacer el monitoreo de lepidópteros plaga en los periodos más secos y fríos del año, cuando pueden presentar picos poblacionales.

Fertility and life expectancy of the predator Supputius cincticeps (Heteroptera: Pentatomidae) exposed to sublethal doses of permethrin

The stinkbug Supputius cincticeps (Stål) (Heteroptera: Pentatomidae) can be found in agricultural and forest ecosystems feeding primarily on larvae of Coleoptera and Lepidoptera, where it can be exposed to insecticide applications. This study therefore aimed to evaluate the reproductive potential of'S. cincticeps after exposition to sublethal doses of permethrin (5.74 x 10-3, 5.74 x 10-2, 5.74 x 10-1, 5.74 and 57.44 ppb) through the use of a fertility life table. The development cycle of this predator was determined in order to calculate its net reproductive rate (R0), the infinitesimal (rm) and finite (λ) rates of increase in addition to mean generation time (T). The net reproductive (18.31), infinitesimal (rm) (0.050) and finite (λ) (1.051) rates of increase were higher, while generation time (57.93 days) was shorter for S. cincticeps exposed to 5.74x10-1 ppb of permethrin than in the control. This indicates a higher rate of population increase of this predator when exposed to this permethrin dose.

Seletividade de extratos de nim (Azadirachta indica A. Juss.) ao ácaro predador Iphiseiodes zuluagai (Denmark & Muma) (Acari: Phytoseiidae) / Selectivity of neem extracts (Azadirachta indica A. Juss.) to the predatory Mite Iphiseiodes zuluagai (Denmark & Muma) (Acari: Phytoseiidae)

The relative toxicity of the leaf, seed and oil neem cake extracts of Azadirachta indica A. Juss (neem) to the predatory mite Iphiseiodes zuluagai (Denmark & Muma) (Acari: Phytoseiidae) was evaluated. To verify the relative toxicity of these extracts on the predatory mite, discriminatingconcentrations of the extracts were determined for adult females of the Oligonychus ilicis (McGregor) (Acari: Tetranychidae), through the method of concentration-mortality. Coffee leaf disks with 3.5 cm of the diameter were put floating on water and impregnated with dry residue of the extracts. Concentrations of neem extracts which caused mortality (99%) of O. ilicis, after 72h of exposition, were 277.4; 520.9 e 10.9 mg/ml for leaf, seed and oil neem cake, respectively. The discriminating concentration of extract ofoil neem cake for O. ilicis females was highly toxic to I. zuluagai; while extract of leaf and seed were selective to the predatory mite.

A toxicidade relativa dos extratos de folha, semente e óleo de torta de Azadirachta indica A. Juss (nim) ao ácaro predador Iphiseiodes zuluagai (Denmark & Muma) (Acari: Phytoseiidae) foi estudada em laboratório. Foram determinadas concentrações discriminatórias (CLs99) dos extratos de folha, semente e óleo de torta de nim para fêmeas adultas de Oligonychus ilicis (McGregor) (Acari:Tetranychidae), através de bioensaios de concentração-mortalidade. Arenas com 3,5 cm de diâmetro, confeccionadas com folhas de cafeeiro flutuando em água, foram impregnadas com resíduo seco dos extratos e usadas para se estimar a seletividade ao ácaro I. zuluagai. As concentrações dos extratos de nim que mataram 99% de O. ilicis, após 72h de exposição foram: 277,4; 520,9 e 10,9 mg/ml, para folha, semente e óleo de torta, respectivamente. A concentração discriminatória do extrato de óleo de torta de nim para fêmeas adultas de O. ilicis foi altamente tóxica ao ácaro I. zuluagai, as dos extratos de folha e de semente foram seletivos.

Desempenho de Thyrinteina arnobia Stoll (Lepidoptera: Geometridae) em eucalipto e goiaba: o hospedeiro nativo não é um bom hospedeiro? / Performance of Thyrinteina arnobia Stoll (Lepidoptera: Geometridae) on eucalyptus and on guava: isn't the native host a good host?

Plants can develop mechanisms of defense that reduces the effects of herbivore attacks. In response, the herbivores evolve to breaking the defense mechanisms of plants. Herbivores may also escape from the plant defense system by migrating to other host whose defense is not effective against them. In Brazil, outbreaks of the defoliator caterpillar Thyrinteina arnobia Stoll in Eucalyptus sp. are frequently observed. However, the native host of this insect is guava, Psidium guajava where outbreaks are not registered. The absence of outbreaks in P. guajava may be related to the development of defense mechanisms in that specie of Myrtaceae, which has apparently not yet occurred on eucalyptus. Here we investigated the performance of T. arnobia reared on its origin host plant, in comparison with those reared on its exotic host, Eucalyptus sp. The intrinsic growth rate of T. arnobia was higher on eucalyptusthan on P. guajava. It is possible that the defense mechanism on guava plants acts as a chemical barrier, probably reducing the digestibility of the insect, which could affect the development of the current population and the next generations.

As plantas podem desenvolver mecanismos de defesa que reduzem o efeito do ataque de herbívoros. Em resposta, os insetos herbívoros evoluem de forma a quebrar os mecanismos de defesa das plantas. Uma das formas que os insetos têm de escapar do sistema de defesa das plantas é migrar para outros hospedeiros cujo sistema de defesa não seja eficiente a seu ataque. No Brasil, em plantios de Eucalyptus spp., observam-se surtos freqüentes da lagarta desfolhadora Thyrinteina arnobia Stoll, cujo hospedeiro nativo é a goiaba. A não ocorrência de surtos populacionais em goiaba pode estarrelacionada ao desenvolvimento de mecanismos de defesa, nessa espécie de Myrtaceae, o que aparentemente ainda não ocorreu com o eucalipto. Por isso, investigou-se neste trabalho se o desempenho de T. arnobia criada em seu hospedeiro de origem, plantas de goiaba, difere do seu desempenho emhospedeiro exótico, o eucalipto. A taxa intrínseca de crescimento populacional de T. arnobia (rm) foi maior em eucalipto do que em plantas de goiaba. O pior desempenho de T. arnobia em plantas de goiaba possivelmente se deu por atuação do sistema de defesa constitutiva dessas plantas. Barreirasquímicas das plantas de goiaba podem estar atuando principalmente na redução da digestibilidade do inseto, afetando o desenvolvimento da população atual e, por conseguinte, o das próximas gerações.

Efeito da escassez de presa na sobrevivência e reprodução do predador Supputius cincticeps (Stål) (Heteroptera: Pentatomidae) / Effect of prey shortage on the reproduction and longevity of Supputius cincticeps (Stål) (Heteroptera: Pentatomidae)

The effect of prey shortage on the performance of Supputius cincticeps (Stål) females was evaluated at 24.6 ± 0.7oC, 80 ± 4% RH and 12h photophase. Larvae of Tenebrio molitor L. were offered to the females during 24h every one, two, four, six or eight days; pieces of green bean (Phaseolusvulgaris L.) were offered continuously. The percentage of females with egg masses, oviposition period, and the number of egg masses, eggs and nymphs decreased with the increase in the interval without prey, whereas the periods of pre- and pos-oviposition increased. On the other hand, longevity and number of eggs per egg mass were not affected by the prey regimen. The results suggest a trade-off between longevity and fecundity (reduction of fecundity to maintain longevity), which could contribute to the establishment and survival of S. cincticeps during periods of prey scarcity.

O efeito da escassez de presas no desempenho de fêmeas de Supputius cincticeps (Stål) foi estudado a 24,6 ± 0,7oC, umidade relativa de 80 ± 4% e fotoperíodo de 12h. Larvas de Tenebriomolitor L. foram fornecidas às fêmeas durante 24h, a cada um, dois, quatro, seis ou oito dias; pedaços de vagem de feijão (Phaseolus vulgaris L.) foram fornecidos em todos os tratamentos de forma contínua. A porcentagem de fêmeas com posturas, o período de oviposição e o número de posturas, de ovos e de ninfas diminuíram com o aumento do intervalo sem presa. Entretanto, os períodos de pré- viposição e de pós-oviposição aumentaram à medida que o alimento tornou-se menos freqüente, enquanto alongevidade e o número de ovos por postura não foram afetados pelo regime de presas. Os resultados sugerem uma compensação entre a longevidade e a fecundidade (redução da segunda para manter a primeira), o que pode contribuir para o estabelecimento e a sobrevivência de S. cincticeps em condições de escassez de presa.

Seletividade de defensivos agrícolas ao fungo entomopatogênico Beauveria bassiana / Selectivity of insecticides and fungicides to the entomopathogenic fungus Beauveria bassiana

A toxicidade relativa dos inseticidas organofosforados clorpirifós-metílico, dissulfotom, etiom, paratiom-metílico, do organoclorado endosulfam, da mistura do fungicida triadimenol e do inseticida dissulfotom e dos fungicidas inibidores da demetilação de esteróis triadimenol e tebuconazole ao fungo Beauveria bassiana (Balsamo) Vuillemin foi estudada em laboratório. As concentrações dos pesticidas que inibiram 99 por cento do crescimento micelial desse fungo, em miligramas de ingrediente ativo por ml foram: tebuconazole = 0,42; paration-metílico = 1,69; triadimenol = 6,53; triadimenol + dissulfotom = 14,42; clorpirifós-metílico = 31,75; etiom = 7.028,96; endosulfam = 10.326,76 e dissulfotom = 763.959,86. As equações de regressão da inibição do crescimento micelial ( por cento), em função da concentração obtida por ensaio in vitro em meio batata-destrose-ágar (BDA) impregnado com os ingredientes ativos desses compostos, foram usadas para se estimar a seletividade das concentrações prescritas para cafezais, pelos seus respectivos fabricantes. Tebuconazole, paratiom-metílico e clorpirifós-metílico foram altamente tóxicos ao fungo B. bassiana; endosulfam e triadimenol + dissulfotom apresentaram seletividade moderada e triadimenol, etiom e dissulfotom foram seletivos para esse fungo.

The relative toxicity of the insecticides organophosphates methyl-chlorpyrifos, disulfoton, ethion, methyl-parathion, the organochlorinate endosulfan and the mixture of the fungicide triadimenol and the insecticide disulfoton and the sterol demethylation inhibiter fungicide (triadimenol and tebuconazole) to the fungus Beauveria bassiana (Balsamo) Vuillemin was evaluated. Concentrations which inhibited radial mycelium growth (99 percent) of B. bassiana were 0.42; 1.69; 6.53; 14.42; 31.75; 7,028.96; 10,326.76 e 763,959.86 mg i.a/ml of tebuconazole, methyl-parathion, triadimenol, triadimenol + disulfoton, methyl-chlorpyrifos, ethion, endosulfan and disulfoton, respectively. The effects of these products were evaluated based on percentage of inhibition of radial mycelium growth of B. bassiana on potato dextrose-agar impregnated with them, after seven days. Tebuconazole, methyl-parathion and methyl-chlorpyrifos were highly toxic to B. bassiana; endosulfan and triadimenol + disulfoton were moderated toxic; while triadimenol, ethion, and disulfoton were selective to this fungi.

Natural enemies of Coelomera lanio (Coleoptera: Chrysomelidae) in the region of Viçosa, Minas Gerais, Brazil

Coelomera lanio (Coleoptera: Chrysomelidae) is the most important defoliator of Cecropia trees. Natural enemies of C. lanio collected in the region of Viçosa, State of Minas Gerais, Brazil were identified on field observations in a forest fragment and on laboratory analyses. Individuals of C. lanio were not found on Cecropia pachystachya trees colonized by Azteca mülleri (Hymenoptera: Formicidae). The majority of the egg masses of C. lanio collected in the field were found to be parasitised by a species of the family Eulophidae (Hymenoptera), while larvae of this pest were attacked by a parasitoid of the family Tachinidae (Diptera). Individuals of Oplomus catena (Heteroptera: Pentatomidae) were observed preying on C. lanio larvae. The fungus Beauveria bassiana was found growing on larvae, pupae and adults of C. lanio while the fungus Metarhizium anisopliae only affected pupae of this insect in laboratory conditions.

Efeito da Densidade de Presas e do Acasalamento na Taxa de Predação de Fêmeas de Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) em Condições de Laboratório e Campo / Effect of Prey Density and Mating Status on Predation Rate of Females of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) in Laboratory and Field Conditions

The predation rate of unmated and mated females of Podisus nigrispinus (Dallas) was evaluated on different densities of Alabama argillacea (Huebner) caterpillars (50 ± 10 mg), in laboratory and field conditions. In the laboratory, the predator females were maintained in 500 ml plastic jars with five different densities of prey (one, two, four, eight, and 16). In the field, caterpillars at the same densities were caged on flowering cotton plants. Under both conditions, females gained weight and increased the predation rate when the availability of prey increased, although higher values were obtained for females kept in the laboratory. Weight gain and predation rate did not differ between unmated and mated females under both conditions. In the field, P. nigrispinus searched 94.7 percent of the available foliar area under low prey density, and 21.2 percent under high prey density. The estimated handling time and attack rate were, respectively, 3.37 ± 0,82h and 0.076 ± 0.013h-1 in the laboratory, and 3.33 ± 0.93h and 0.017 ± 0.003h-1 in the field. The functional response corresponded to a type II for both conditions. The number of killed caterpillars observed and estimated by the model were highly correlated for both laboratory (r = 0.78) and field (r = 0.70) conditions.

Avaliou-se a taxa de predação de fêmeas virgens ou acasaladas de Podisus nigrispinus (Dallas) em diferentes densidades de lagartas de Alabama argillacea (Huebner) em condições de laboratório e de campo. Em laboratório, empregaram-se potes plásticos de 500 ml contendo fêmeas do predador, uma folha de algodão e lagartas de A. argillacea (50 ± 10 mg) nas densidades de uma, duas, quatro, oito e 16 lagartas. No campo, algodoeiros na fase de florescimento foram engaiolados, sendo empregadas as mesmas densidades de lagartas que no laboratório. Em ambas as condições, as fêmeas de P. nigrispinus apresentaram ganho de peso e aumento de sua taxa de predação com o aumento da densidade de lagartas de A. argillacea, mas com valores maiores para fêmeas em laboratório. Nas duas condições, o ganho de peso e a taxa de predação foram semelhantes para fêmeas virgens ou acasaladas. No campo, P. nigrispinus explorou 94,7 por cento e 21,2 por cento da área foliar disponível na menor e maior densidade de presas, respectivamente. O tempo de manipulação e a taxa de ataque estimadas foram de 3,37 ± 0,82h e de 0,076 ± 0,013h-1 em laboratório, e de 3,33 ± 0,93h e de 0,017 ± 0,003h-1 em campo. A resposta funcional em laboratório e no campo foi caracterizada como do Tipo II. Os números observados e estimados de lagartas predadas pelo modelo foram significativamente correlacionados com as condições de laboratório (r = 0,78) e de campo (r = 0,70).

Lepidoptera pests collected in Eucalyptus urophylla (Myrtaceae) plantations during five years in TrÛs Marias, State of Minas Gerais, Brazil

Lepidoptera pest species from eucalyptus were collected in Eucalyptus urophylla plantations in the region of TrÛs Marias, State of Minas Gerais, Brazil, every 15 days from June 1989 to June 1994 with five light traps. Twelve primary and 15 secondary pest species were collected in the period with an average of 13,387 and 812 individuals per light trap, respectively. Most collected primary pest species were Stenalcidia grosica (Geometridae), Iridopsis subferaria (Geometridae), Eupseudosoma aberrans (Arctiidae) and Psorocampa denticulata (Notodontidae), totalizing for the study period an average of 5,450, 2,162, 2,436 and 1,458 individuals per light trap, respectively. Idalus admirabilis (Arctiidae) was the most collected secondary pest species, averaging 652 individuals/trap. Most primary pest species were collected during the dry season, from April to July, whereas most secondary pest species were collected during the rainy season, from January to March. These differences on seasonal occurrence between the two groups could be due to the fact that many secondary pest species of Eucalyptus in Brazil pupate in the soil, and they need humidity to complete its pupal stage.