Alexandre Faria da Silva

Estimativa de Trichogramma pretiosum para controle de Tuta absoluta em tomateiro estaqueado

The objective of this work was to estimate the ideal number of Trichogramma pretiosum Riley to be released in field for the tomato leafminer control Tuta absoluta (Meyrick). An experiment was carried out in a greenhouse, in which tomato plants with 60 days, after the transplantation, were infested with 200 eggs of Anagasta kuehniella (Zeller), an alternative host, in the subsequent ratios: 70% of eggs were put on the top of the plants, 24% on the medium height and 6% on the very bottom of the plants. Females of T. pretiosum were released following the ratios of 1, 2, 4, 8, 16 and 32 parasitoids per host egg. Independently of the three distinct plant parts (top, medium or bottom), the ratio of 16 parasitoids per host egg delivered the best results. This ratio value was closer to the ideal number for field releasing in commercial crop production of stalked tomato, aiming the tomato leafminer control.

Biological characteristics of Trichogramma pretiosum and Trichogramma acacioi (Hym.: Trichogrammatidae), parasitoids of the avocado defoliator Nipteria panacea (Lep.: Geometridae), on eggs of Anagasta kuehniella (Lep.: Pyralidae)

The objective of this investigation was to study Trichogramma pretiosum and T. acacioi (Hymenoptera: Trichogrammatidae), parasitoids of the avocado defoliator Nipteria panacea (Lepidoptera: Geometridae) on the eggs of the alternative host Anagasta kuehniella (Lepidoptera: Pyralidae) aiming to use them for biological control of this pest in avocado orchards. The cubic model presented better adjustment for duration of the life cycle of T. pretiosum and T. acacioi with the host A. kuehniella which shows that development rate of these species increases with temperature within the range tested. The number of individuals of both Trichogramma species emerged per egg from this host was higher than one. The quadratic model was significant for viability of T. pretiosum and T. acacioi. This parameter was more affected by extreme temperatures and higher emergence rates of adults of both parasitoids species occurred at temperatures of 20, 25 and 30°C.

Selection of Trichogramma species for controlling the Diamondback moth

Biological characteristics of the egg parasitoids Trichogramma acacioi, T. atopovirilia, and T. bennetti were studied to select the one with better performance on the control of the Diamondback moth, Plutella xylostella. Parasitism rate, viability, and sex ratio were studied. Parasitism rate ranged from 1.67 to 41.33%. T. atopovirilia and T. acacioi were respectively the most and less aggressive species. The viability ranged from 6.20% for T. acacioi to 53.34% for T. atopovirilia. There were no differences on sex ratio (P < 0.05) that remained above 0,88. T. atopovirilia was the species with best performance in the laboratory when rearing on the Diamondback moth eggs.

Priming and drying on the physiological quality of eggplant seeds

We evaluated the effect of the priming with polyethyleneglicol (PEG) 6000 followed or not of drying on two lots of eggplant seeds with medium and low vigor respectively. The seeds were submitted to the treatments of priming with PEG 6000 in the osmotic potentials of -0.6, -0.9 and -1.2 MPa during 48 or 96 hours of priming with and without subsequent drying. For the soaking of seeds in osmotic solutions, these were placed over three sheets of paper boxes such germitest gerbox conditioning moistened with each solution in a 3:1 ratio. The control group was represented by unprimed seeds. The priming for both lots provided higher values in relation to the vigor through the first counting of germination, seedlings and primary root length, germination and emergence rates, emergence and dry weight of seedlings when compared to the non-primed seeds. These results were not verified for germination; significant differences practically were not observed in relation to the controls. Improvements in relation to the vigour were not higher on lot 2 than those obtained on lot 1. The priming with PEG 6000 with subsequent drying increased the vigor of eggplant seeds of the cultivar Morro Grande in relation to those non-primed, however, without differences in the germination.

Tabela de vida de fertilidade de cinco linhagens de Trichogramma pretiosum Riley (Hym.: Trichogrammatidae) criadas em ovos de Tuta absoluta (Merick) (Lep.: Gelechiidae), sob temperaturas constantes e alternadas

The objective of this research was to construct a life table for five strains of Trichogramma pretiosum, in eggs of Tuta absoluta, for the constant and alternate temperatures, using the data of the biological characteristics and of the capacity of parasitism. The mean generation time (T), for in the constant temperatures, except for the strain L2, presented an inverse relationship with the thermal elevation for the other strains of T. pretiosum. The mean generation time (T) it was smaller, for all the strains, in the temperature of 30°C. The maximum capacity of increase of the population measured by Ro, happened at the temperature of 25°C, for the strains L2, L5 and L6. Except for the strain L4, all the others showed a direct relationship of the intrinsic rate of increase (rm) with the elevation of the temperature. It was due to environmental characteristics where the strains had been found.

First report of parasitism of the Trichogramma bruni Nagaraja (Hymenoptera: Trichogrammatidae) in eggs of urbanus proteus (L.) (Lepidoptera: Hesperiidae) in snap beans (Phaseolus vulgaris) ( L.)

Aiming to verify the presence of eggs parasitoids of the genus Trichogramma, for using in the biological control of insects pests, were collected eggs from long tailed skipper butterfly, a lepidopteran defoliator of snap beans, which presented eggs with parasitism characteristics (dark eggs). The eggs were taken to the laboratory were 44.9% of parasitism was verified. Viability was 96.3%, with an average of 6.6 individuals per egg and a sexual ratio of 0.93. Male specimens were identified as Trichogramma bruni Nagaraja. It is the first report of parasitism in this host and culture.

INFLUÊNCIA DA DENSIDADE DE OVOS DE Spodoptera frugiperda EM ALGUNS ASPECTOS BIOLÓGICOS DE TRÊS ESPÉCIES DE Trichogramma

O objetivo do presente trabalho foi determinar as isotermas de sorcao das espigas de milho para diversas condicoes de temperatura e umidade relativa do ar e ajustar diferentes modelos matematicos aos dados experimentais. Para obtencao do teor de agua de equilibrio higroscopico das espigas de milho foi utilizado o metodo estatico, em câmaras com temperatura controlada, contendo no seu interior dessecadores com solucoes salinas saturadas. A temperatura variou entre 10 e 50°C e a umidade relativa entre 0,11 e 0,84 (decimal). As amostras foram pesadas periodicamente, sendo o equilibrio higroscopio alcancado quando a variacao da massa das amostras foi igual ou inferior a 0,01 g. Os modelos matematicos recomendados pela ASAE foram ajustados as dados experimentais. Para a avaliacao do grau de ajuste de cada modelo considerou-se a magnitude do coeficiente de determinacao ajustado, erros medio relativo e estimado, e a verificacao do comportamento da distribuicao dos residuos. Conclui-se que a higroscopicidade da espiga de milho segue a mesma tendencia da maioria dos produtos agricolas e que os modelos de Chung-Pfost Modificado, Halsey Modificado e Oswin Modificado representam adequadamente o fenomeno.

Lepidopteran pests associated with the soybean cultivars phenology

Lepidopteran pests are one of the major constraints to the soybean production potential, whose defoliating caterpillars can occur throughout the crop cycle causing serious damage. Therefore, the objective was to study the population fluctuation of lepidopteran pests and the association of species with the growth stages of soybean cultivars in the Cerrado of Piaui State, Brazil, in order to obtain data to support integrated pest management in the crop. The experiments had as a source of variation thirteen cultivars with fourteen evaluations. The design used was completely randomized in split plots being the cultivars plots and subplots the cultivars phenological stages. The monitoring was conducted by shake-cloth method at random points. Weekly samplings were performed. Generally, species of lepidopteran pests occurred in all soybean phenological stages, especially Chrysodeixis includens and Anticarsia gemmatalis that were present from the beginning to the end of the crop.

Parâmetros biológicos e exigências térmicas de Trichogramma pretiosum sobre ovos de Helicoverpa armigera

The objective of this work was to determine the biological parameters and thermal requirements of Trichogramma pretiosum TM strain reared on Helicoverpa armigera eggs. A card containing 20 eggs of H. armigera was offered for each T. pretiosum female, at temperatures of 18, 20, 22, 25, 28, 30 and 32°C. All life stages of T. pretiosum were observed under the given temperature conditions. The optimum temperature for the parasitism of T. pretiosum was 25°C, and the highest longevity was found at the same temperature. The highest parasitoid emergence rates occurred at temperatures of 22, 25 and 28°C. The highest proportion of T. pretiosum individuals emerged per egg was observed at 18°C. Concerning the sex ratio, the highest proportion of females occurred at 28°C, and the highest percentage of parasitism viability was observed at this same temperature. The lowest thermal threshold for total preimaginal development and thermal requirements of T. pretiosum were 10.82°C and 134.55 degree-days, respectively. The estimated number of generations of T. pretiosum in the average temperatures of municipality of Bom Jesus, state of Piauí, Brazil is four per month.

Seleção de espécies de Trichogramma visando o controle da traça-das-crucíferas

Foram estudados os aspectos biologicos das especies Trichogramma acacioi, T. atopovirilia e T. bennetti, com o objetivo de selecionar aquela com melhor desempenho, para utilizacao no controle da traca-das-cruciferas, Plutella xylostella. As caracteristicas biologicas avaliadas foram parasitismo, viabilidade e razao sexual. A taxa de parasitismo variou entre 1,67 e 41,33%, sendo o maior valor observado para o T. atopovirilia e, o menor, para T. acacioi. A viabilidade variou entre 6,20% para T. acacioi a 53,34% para T. atopovirilia. Nao houve diferenca significativa para a razao sexual, (P<0,05), que ficou acima de 0,88. T. atopovirilia foi a especie de melhor desempenho em laboratorio quando criada sobre ovos da traca-das-cruciferas.