Gleice Aparecida de Assis

Silício e imidacloprid na colonização de plantas por Myzus persicae e no desenvolvimento vegetativo de batata inglesa

The aphid Myzus persicae (Sulzer) is a key pest of potato crops, the yield of which depends on insecticides for its control. This research was carried out to verify the effect of silicon and imidacloprid on the colonization of potato plants by M. persicae and its possible positive consequences on development parameters. Five treatments with seven replications were tested: 1- control treatment; 2- 1% silicic acid; 3- imidacloprid at the recommended dosage (252g ha-1); 4- 1% silicic acid and imidacloprid at half recommended dosage (126g ha-1) and 5- imidacloprid at half the recommended dosage (126g ha-1). Twenty days after planting, the plants were infested with ten adult aphids. After 20 days of infestation, the number of nymphs and of adult aphids; the height, the diameter, the number of leaves and the fresh and dried weights of the plants were evaluated. The plants treated with insecticides were not so colonized by the aphids and those with silicon presented lower infestation in relation to the control. In relation to the height, diameter and weights, there was no significant difference among the treatments, however the control presented the lowest number of leaves. Therefore, silicon reduced the colonization of potato by M. persicae and the use of half dosage of imidacloprid (126g ha-1) was equally efficient to prevent the colonization, making silicated fertilization one more strategy to be tested in the integrated management of potato plant pests.

Leaf miner incidence in coffee plants under different drip irrigation regimes and planting densities

O objetivo deste trabalho foi avaliar o efeito de diferentes regimes de irrigacao por gotejamento e densidades de plantio na incidencia do bicho‑mineiro, Leucoptera coffeella, em cafeeiro arabica, ao longo de um ano. O experimento foi realizado em 2008, em delineamento de blocos ao acaso, em parcelas subdivididas no tempo, com quatro repeticoes. Os tratamentos consistiram de quatro regimes de irrigacao por gotejamento – balanco hidrico climatologico, irrigacoes com base nas tensoes de 20 e 60 kPa, e uma testemunha nao irrigada –, os quais foram distribuidos em tres densidades de plantio: 2.500, 5.000 e 10.000 plantas por hectare. As avaliacoes foram realizadas mensalmente entre janeiro e dezembro de 2008. O maior periodo de ocorrencia da praga foi registrado de agosto a novembro, epoca de baixa umidade relativa do ar antecedida por periodo de estiagem. Cafeeiros irrigados apresentaram incidencia de minas intactas 2,2 vezes menor do que as plantas nao irrigadas. A irrigacao e o aumento da densidade de plantio contribuem para a reducao da incidencia do bicho‑mineiro do cafeeiro.

Antioxidants in the control of microorganism contamination and phenol oxidation in Eugenia pyriformis

Uvaia (Eugenia pyriformis) is a fruit tree of the Myrtaceae family. It has recalcitrant seeds of limited longevity, making seed propagation difficult. Micropropagation is an alternative method to obtain a large quantity of progeny plants in a short period of time, by using any part of the plant as explant. The high concentration of phenols associated with the chemical composition of the Myrtaceae, and the presence of microorganisms in the plant material or culture media, can make in vitro propagation difficult and/or impossible. The objective was to evaluate various concentrations of antioxidants affecting the control of microbial contamination and phenol oxidation in vitro in uvaia. A completely randomized design was used, with a 3 (antioxidants PVP, L-cysteine, and ascorbic acid) × 3 (antioxidant concentrations 100, 200, and 300 mg L) × 2 (activated charcoal at 0 and 2 g L) factorial arrangement + 2 additional variables (absence of antioxidants and activated charcoal; absence of antioxidants with 2 g L activated charcoal), with three repetitions comprising four plants each. The percentage of bacterial and fungal contaminations, along with the number of oxidized explants, was evaluated after 7, 14 and 21 days of in vitro cultivation. It was concluded that, where bacterial and fungal contaminations were concerned, in vitro cultivation of uvaia can be performed without the use of antioxidants. PVP or ascorbic acid must, however be used in the process, at a concentration of 300 mg L, along with 2 g L of activated charcoal. This helps to minimize phenol oxidation.