Miguel Michereff Filho

Effects of delayed mating and male mating history on the reproductive potential of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

Abstract  1 Despite the importance of Leucoptera coffeella (Guérin‐Mèneville) in coffee production worldwide, there is a lack of information on its reproduction. This knowledge will help in mass rearing, and support the development of behavioural control techniques for this insect. The present study determined the effects of delayed mating and previous matings of male L. coffeella on fecundity, egg viability and frequency of female remating.

Resistance of Brazilian diamondback moth populations to insecticides

Plutella xylostella e uma praga recorrente em brassicas de todo o mundo. No Brasil, normalmente exige grande numero de pulverizacoes de inseticidas, que pode levar a rapida evolucao da resistencia. Avaliou-se a suscetibilidade de populacoes brasileiras da traca das cruciferas aos inseticidas abamectina, deltametrina e espinosade. Bioensaios de imersao de folhas foram utilizados para determinar a mortalidade, sendo os dados obtidos apos 48 h de exposicao aos inseticidas e submetidos a analise de Probit. A populacao de Bonito-PE apresentou a maior razao de toxicidade (20,2 vezes) para abamectina em relacao a populacao de referencia. Os valores de CL50s para deltametrina variaram entre 85,2 - 360,1 mg L-1, demonstrando alta sobrevivencia das populacoes a este inseticida com relacao a dose de campo (7,5 mg L-1). Entretanto, as razoes de toxicidade das CL50 estimadas foram muito baixas (variando de 2,2 a 4,2 vezes). A maioria das populacoes apresentou razoes de toxicidade para espinosade, variando de 2,3 para 5,1 vezes, embora os valores de CL demonstram alta suscetibilidade delas a dose de campo para espinosade (120 mg L-1). Apenas a populacao de Bonito PE apresentou resistencia a abamectina, enquanto todas as populacoes de P. xylostella estao resistentes a deltametrina, mas suscetiveis ao espinosade particularmente devido a ausencia de pressao de selecao com este nestas areas.

Relações entre atributos do solo e atividade de formigas em restingas

In restinga soils with sand-quartzous constitution the influence of the organic fraction and biological activity on soil key functions is increased, e.g., the capacity of recycling and storing nutrients. The analysis of soil attributes and edaphic fauna at sites under different vegetation cover types is important to understand the behavior of these environments. In this study, chemical, physical and microbiological soil attributes of restinga sites and their relationships with ant populations under different vegetation types in the state of Sergipe were evaluated. Samples of six vegetation types (three sites per cover) were collected, four of which in the area of Caju (forest, ginger-grass, coconut palm plantation and brushwood) and two in the area of Pirambu (dune plateau forest and dune footslope forest). Chemical attributes were analyzed in samples collected from the layers 0-5 and 5-20 cm and the microbial activity evaluated by hydrolysis of fluorescein diacetate, in samples collected from the 0-10 cm layer. The organic fragment mass was evaluated at different depths. Ant communities with activity on the soil surface were considered for evaluation. The principal component analysis was used to compare the sites. The organic compartment attributes (organic C, dissolved organic C and organic fragments) were very sensitive to modifications in the vegetation cover at Caju sites, isolating the native forest sites from the disturbed ones and the ginger-grass site from the coconut palm and brushwood sites. Soil solution attributes influenced by sea-salt spray (electric conductivity, K, Na and Mg) distinguished the Pirambu from the Caju sites. The ant groups had a high level of specialization. Canonical correspondence analysis indicated a low percentage of variance of distribution of these groups and isolated the forest sites from other uses, indicating the existence of other attributes to be considered for distribution.

Host range and whitefly transmission efficiency of Tomato severe rugose virus and Tomato golden vein virus in tomato plants

Begomoviruses are the most important viruses affecting tomato (Solanum lycopersicum) crops in Brazil. Tomato severe rugose virus (ToSRV) is the most predominant species, followed by Tomato golden vein virus (TGVV). We evaluated the putative effect of host range and whitefly transmission efficiency on the predominance of ToSRV. Whitefly (Bemisia tabaci, B biotype or MEAM 1) vectors carrying the two viruses were allowed to freely inoculate plants of 27 species, maintained in cages. Visual and PCR detection indicated that ToSRV could infect five plant species and TGVV could infect six species. Transmission studies were performed in single or double infections in tomato plants. ToSRV infected a higher percentage of plants than TGVV (single or mixed inoculation) in all trials. The rates of acquisition of ToSRV and TGVV, however, did not differ significantly between insects fed on tomato leaves with single or mixed infections. A higher transmission efficiency of ToSRV by whiteflies under the agricultural conditions of tomato cultivation in Brazil may thus contribute to the predominance of ToSRV in the field.

Sprinkler and drip irrigation in the organic tomato for single crops and when intercropped with coriander

The objective of this study was to evaluate the influence of both sprinkler and drip irrigation systems on the organic production of the tomato, cultivar Duradouro, when cultivated both as a single crop and intercropped with coriander. The experiment was carried out in the Distrito Federal, Brazil, using a randomized block design with six replications and a 2 x 2 factorial arrangement for the treatments. There was no significant interaction between the factors of irrigation system and cropping system. The productivity and mass of the tomato fruits were not affected by the treatments, but for the coriander, productivity was higher under the sprinkler system. Drip irrigation hindered the development of late blight (Phytophthora infestans) and reduced the percentage of rotten fruit, whereas the incidence of powdery mildew (Leveillula taurica) and infestation by the tomato leafminer (Tuta absoluta) were higher under the sprinkler system. The volume of soil exploited by the roots of tomato plants was higher with the sprinkler system, while the water productivity index with the drip system was 47% higher than with the sprinkler system. Firmer fruits were produced under drip irrigation. The cultivation system had a significant effect on the occurrence of insect pests, with the tomato intercropped with coriander showing a lower percentage of damaged fruit due to the Tomato Leafminer and to Spodoptera eridania.

Comportamento de acasalamento do bicho-mineiro-do-cafeeiro, Leucoptera coffeella (Guérin-Mèneville) (Lepidoptera: Lyonetiidae)

Despite the importance of Leucoptera coffeella (Guerin-Meneville) in coffee production worldwide, there is a lack of information on its reproductive biology. This knowledge will help in mass rearing, as well as support the development of behavioral control techniques for this insect. The purpose of the study was to determine the periodicity of mating and male capture and describe the mating behavior L. coffeella. In laboratory, we observed the periodicity of mating with virgin couples of different ages, zero to five days after emergence. Male activity was studied in a 0.7 ha coffee plantation, cv. Catuai, where Delta traps were installed at 0.5 m above ground, using either virgin females or rubber septa lured with the synthetic sex pheromone. The sequence of mating behavior was studied by making visual observations and recorded of pairs placed on individual plastic tubes. Mating occurred between 4h and 6h of photophase, when the highest frequencies involved pairs with ages of one and three days after emergence, with peak of mating occurring in 5th hour of photophase. The young or old pairs showed significantly copulation frequency and the peak of matings advance in 1h. The highest male capture occurred at 12p.m. and 13 p.m. by traps with virgin females or traps with synthetic sex pheromone lures, respectively. L. coffeella is one insect with diurnal mating and the mating behavior was not different from what is know for other Lepidoptera species.

Efeito da adubação química na infestação do ácaro rajado e na produção do morangueiro

Effect of chemical fertilization on two-spotted-spider mite infestation and strawberry yield The effect of N:K relationship was evaluated when applied through fertigation, on two-spotted-spider mite, Tetranychus urticae, infestation and on the yield of two strawberry cultivars. Strawberry plants received weekly doses of N and K (g/plant) by drip irrigation: 0.27 and 0.13; 0.27 and 0.50; 0.27 and 0.76 and control (water+micronutrients). Fruits were collected twenty two times during crop cycle. Marketable, non-marketable fruits and other yield parameters were evaluated. Leaf nutrient content analysis was performed to determine the nutritional condition of the plants. Population density of T. urticae was evaluated weekly. A significant interaction between K doses and pest population was observed. Higher doses of the nutrient reduced the number of eggs and active forms of the pest population and the cultivar Diamante showed the smallest pest density. K and P showed negative correlation with both variables, but N showed a positive one. No effects were observed of fertilization on yield parameters due, probably, to the high mite infestation (>40 individuals per leaflet) in all treatments during most of the crop cycle. Solely the use of different N:K ratios on the strawberry fertilization management at this specific experimental condition, was not sufficient to control two-spotted spider mite nor to reduce losses caused by that pest.