Transfer of Cry1F from Bt maize to eggs of resistant Spodoptera frugiperda.

The intergenerational transfer of plant defense compounds by aposematic insects is well documented, and since 2006, has been shown for Cry toxins. Cry toxins are proteins naturally produced by the soil bacterium Bacillus thuringiensis (Bt) and its genes have been expressed in plants to confer insect pest resistance. In this work we tested if non-aposematic larvae of a major maize pest, Spodoptera frugiperda, with resistance to Cry1F, could transfer Cry1F from a genetically engineered maize variety to their offspring. Resistant 10-day-old larvae that fed on Cry1F Bt maize until pupation were sexed and pair-mated to produce eggs. Using ELISA we found that Cry1F was transferred to offspring (1.47-4.42 ng Cry1F/10 eggs), a toxin concentration about 28-83 times less than that detected in Cry1F Bt maize leaves. This occurred when only one or both sexes were exposed, and more was transferred when both parents were exposed, with transitory detection in the first five egg masses. This work is an unprecedented demonstration that a non-aposematic, but resistant, species can transfer Cry1F to their offspring when exposed to Bt host plant leaves as immatures.

Life-History Traits of Spodoptera frugiperda Populations Exposed to Low-Dose Bt Maize.

Exposure to Bacillus thuringiensis (Bt) toxins in low- and moderate-dose transgenic crops may induce sublethal effects and increase the rate of Bt resistance evolution, potentially compromising control efficacy against target pests. We tested this hypothesis using the fall armyworm Spodoptera frugiperda, a major polyphagous lepidopteran pest relatively tolerant to Bt notorious for evolving field-relevant resistance to single-gene Bt maize. Late-instar larvae were collected from Bt Cry1Ab and non-Bt maize fields in five locations in Brazil, and their offspring was compared for survival, development, and population growth in rearing environment without and with Cry1Ab throughout larval development. Larval survival on Cry1Ab maize leaves varied from 20 to 80% among the populations. Larvae reared on Cry1Ab maize had seven-day delay in development time in relation to control larvae, and such delay was shorter in offspring of armyworms from Cry1Ab maize. Population growth rates were 50-70% lower for insects continuously exposed to Cry1Ab maize relative to controls, showing the population-level effect of Cry1Ab, which varied among the populations and prior exposure to Cry1Ab maize in the field. In three out of five populations, armyworms derived from Bt maize reared on Cry1Ab maize showed higher larval weight, faster larval development and better reproductive performance than the armyworms derived from non-Bt maize, and one of these populations showed better performance on both Cry1Ab and control diets, indicating no fitness cost of the resistance trait. Altogether, these results indicate that offspring of armyworms that developed on field-grown, single-gene Bt Cry1Ab maize had reduced performance on Cry1Ab maize foliage in two populations studied, but in other three populations, these offspring had better overall performance on the Bt maize foliage than that of the armyworms from non-Bt maize fields, possibly because of Cry1Ab resistance alleles in these populations. Implications of these findings for resistance management of S. frugiperda in Bt crops are discussed.

Desenvolvimento, consumo ninfal e exigências térmicas de Orius thyestes Herring (Hemiptera: Anthocoridae) / Development, nymphal consumption and thermal requirements of Orius thyestes Herring (Hemiptera: Anthocoridae)

A temperatura e o alimento têm um importante papel no desenvolvimento e nas atividades de adultos de espécies de Orius, e esses parâmetros biológicos são fundamentais para propósitos de criação massal de inimigos naturais e seu uso em programas de controle biológico. O objetivo deste trabalho foi avaliar a influência de diferentes temperaturas no desenvolvimento ninfal do predador Orius thyestes Herring alimentado com ovos de Anagasta kuehniella (Zeller). Também foram determinadas as exigências térmicas e o consumo ninfal. O experimento foi conduzido em câmaras climáticas a 16, 19, 22, 25, 28 e 31 ± 1°C, UR de 70 ± 10 por cento e fotofase de 12h. O. thyestes apresentou cinco ínstares. O período ninfal foi cerca de seis vezes maior a 31°C (9,8 dias) do que a 16°C (58,2 dias). A menor sobrevivência ninfal do predador foi a 16°C, com somente 40 por cento das ninfas atingindo a fase adulta. Maiores percentagens de sobrevivência das ninfas foram observadas a 22°C (96,4 por cento), 25°C (94,5 por cento) e 28°C (100 por cento). Cada ninfa de O. thyestes consumiu 39,4 ovos de A. kuehniella. O predador apresentou temperatura base e constante térmica para a fase ninfal de 12,8°C e 173,82 graus-dia, respectivamente. O intervalo mais adequado para o desenvolvimento de O. thyestes situa-se entre 22°C e 28°C. O. thyestes provavelmente encontra melhores chances de colonização e estabelecimento em regiões tropicais e subtropicais.

Temperature and food play an important part in the development time and adult activities of Orius species, and these biological parameters are important for purpose of mass rearing of natural enemies for use on biological control programs. The objective of this research was to evaluate the influence of different temperatures on nymphal development of Orius thyestes Herring when fed with Anagasta kuehniella (Zeller) eggs in climatic chambers at 16, 19, 22, 25, 28 and 31 ± 1°C, 70 ± 10 percent RH and 12h photophase. The thermal requirements and nymphal consumption were also determined. O. thyestes presented five instars. The nymphal period was about six times shorter at 31°C (9.8 days) than at 16°C (58.2 days). Nymph survival was lowest at 16°C, with only 40 percent of the nymphs reaching adult stage. The higher nymph survival were found at 22°C (96.4 percent), 25°C (94.5 percent) and 28°C (100 percent). Each nymph of O. thyestes consumed 39.4 eggs of A. kuehniella. The lower temperature threshold and thermal constant for the nymphal development of O. thyestes were 12.8°C and 173.82 day-degrees, respectively. The interval from 22°C to 28°C is more suitable for nymphal development of O. thyestes. O. thyestes finds probably better chance for colonization and establishment in tropical and subtropical regions.

Adequabilidade de diferentes substratos à oviposição do predador Orius insidiosus ( Say ) ( Hemiptera: Anthocoridae ) / Suitability of different substrates for oviposition of the predator Orius insidiosus ( Say ) ( Hemiptera: Anthocoridae )

Fêmeas de Orius insidiosus (Say) colocam seus ovos endofíticamente, em diversas plantas, e um obstáculo para a criação massal desse predador é a seleção de um substrato de oviposição que seja de fácil obtenção e aceito pelo inseto. O objetivo deste estudo foi avaliar a preferência e a adeqüabilidade de diferentes substratos de oviposição para O. insidiosus. Os testes foram conduzidos em câmaras climatizadas reguladas a 25 ± 1°C, UR de 70 ±10 por cento e fotofase de 12h. Os substratos avaliados quanto à preferência e adequabilidade foram caule de caruru (Amaranthus viridis L.), caule e vagem de feijão (Phaseolus vulgaris L.), vagem de feijão-de-vagem (Phaseolus vulgaris L.) e inflorescências de picão-preto (Bidens pilosa L.). Na adequabilidade também foi avaliado o caule de poaia-do-campo (Spermacoce latifola Aubl.). Fêmeas submetidas aos testes com e sem chance de escolha preferiram ovipositar em inflorescências de picão-preto. O período de pré-oviposição foi influenciado pelo tipo de substrato, sendo menor na presença da inflorescência de picão-preto (3,0 dias) e no feijão, tanto no caule (3,1dias) como na vagem (3,7 dias) comparado aos demais substratos. O período de oviposição, bem como a longevidade foram cerca de três a quatro vezes menores na presença do caule de poaia-do-campo (8,9 dias). O número total de ovos/fêmea de O. insidiosus foi maior em inflorescências de picão-preto (163,3 ovos). Os resultados indicam a adeqüabilidade das inflorescências de picão-preto como substrato de oviposição para O. insidiosus, sendo o preferido nos testes, com e sem chance de escolha, e onde as fêmeas apresentaram melhor performance reprodutiva.

Efeito da densidade de ninfas de Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) no consumo alimentar e aspectos biológicos de Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae) / Effect of ninfal density of Ashis gossypi Glover, 1877 (Hemiptera, Aphididae) on feed consumption and biological aspects of Orius insidiousus (Say, 1832) (Hemiptera, Anthocoridae)

Effect of ninfal density of Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) on feed consumption and biological aspects of Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae). The influence of different densities of A. gossypii (10, 20, 30, 40, 50, 60 nymphs/day) on consumption rate, development time, survival, and reproduction of Orius insidiosus (Say, 1832) was investigated. The trials were carried out in climatic chamber at 25 ± 1 ºC, 70±10 percent RH, and photoperiod 12:12h (L:D). Consumption rates of nymphs and adults increased under a linear form as the densities of aphids increased. Development time was longest when reared in 10 nymphs density (15.4 days). Nymphal survival was different under the densities of A. gossypii and no significant difference for the periods of preoviposition (4.8 days) and oviposition (8.9 days) were found. The oviposition increased with the prey densities (2.00, 11.33, 10.67, 21.30, 17.89 and 53.38 eggs), as well as the viability: 0.00, 52.49, 57.86, 58.14, 50.11 and 72.89 percent, respectively. Nymphs of A. gossypii as prey were suitable for the complete development of O. insidiosus

Biologia de Orius insidiosus (Say) (Hemiptera: Anthocoridae) Alimentado com Caliothrips phaseoli (Hood) (Thysanoptera: Thripidae) / Biology of Orius insidiosus (Say) (Hemiptera: Anthocoridae) Fed on Caliothrips phaseoli (Hood) (Thysanoptera: Thripidae)

The biology of Orius insidiosus (Say) fed on thrips Caliothrips phaseoli (Hood) was studied in a climatic chamber at 25±1°C, 70±10 percent RH and 12h photophase. Nymphal developmental time (10.2 days) was the same for males and females. The durations of the nymphal instars were 1.9, 1.7, 1.4, 1.8 and 3.1 days for the 1st, 2nd, 3rd, 4th and 5th instars respectively. Nymphal survival was 69 percent, and the highest mortality occurred at the 2nd instar. O. insidiosus consumed 73.7 C. phaseoli throughout its nymphal stage. The amount of prey fed upon by O. insidiosus nymphs increased during the successive instars: 6.1, 9.0, 11.4, 16.7 and 29.3 thrips from the 1st to the 5th instar respectively. Females laid 77.8 eggs. Egg development in O. insidiosus took 5.3 days and only 71.6 percent of the eggs hatched. Female longevity was significantly higher (21 days) than that of males (12.4 days); consequently, females ate more thrips (159.1) than the males (60.7). The search time of O. insidiosus was the same for all instars. Thus, adults of C. phaseoli were proved suitable to the development and reproduction of the predator O. insidiosus.

A biologia do percevejo predador Orius insidiosus (Say), utilizando como alimento, adultos de Caliothrips phaseoli (Hood), foi estudada em câmara climática com temperatura de 25±1°C, 70±10 por cento de UR e 12h de fotofase. O período de desenvolvimento ninfal foi de 10,2 dias, não apresentando diferença significativa para machos e fêmeas. A duração do estágio ninfal foi 1,9, 1,7, 1,4, 1,8 e 3,1 dias para o 1°, 2°, 3°, 4° e 5° ínstares, respectivamente. A viabilidade ninfal foi de 69,0 por cento, sendo que a maior mortalidade ocorreu no 2° ínstar (16,0 por cento). O. insidiosus predou 73,7 tripes durante todo o estágio ninfal. O consumo de presas pelas ninfas de O. insidiosus aumentou com os sucessivos instares: 6,1, 9,0, 11,4, 16,7 e 29,3 tripes do 1° ao 5° ínstares, respectivamente. Não houve diferença no tempo de busca para os diferentes ínstares do predador, sendo que durou em média 52 min., a captura da presa foi dificultada pela intensa reação de defesa apresentada pela mesma, que consistiu na sua maioria, em saltos e pequenas corridas. As fêmeas ovipositaram 77,8 ovos com viabilidade de 71,6 por cento e com um período embrionário de 5,3 dias. A longevidade das fêmeas (21 dias) foi significativamente maior que a dos machos (12,4 dias). O consumo das fêmeas foi de 159,1 tripes e o dos machos de 60,7 tripes. Não foi observada diferença no tempo de busca para os diferentes instares de O. insidiosus. Os resultados indicam que adultos de C. phaseoli são presas adequadas ao desenvolvimento e reprodução do predador O. insidiosus.