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A forma de controlar o pedrado da macieira assenta, essencialmente, na aplicação repetida de fungicidas. A utilização sucessiva das mesmas famílias de fungicidas, levanta a preocupação do risco de desenvolvimento de resistências. Realizaram-se ensaios de campo em dois pomares que representam diferentes pressões de desenvolvimento da doença e ensaios in vitro com conídios provenientes destes pomares. No pomar de alto risco, os resultados demonstram a existência de resistência in vitro comprovada pela falta de eficácia das estrobilurinas no ensaio de campo. Por seu lado, no “pomar de baixo risco”, cerca de 1/3 dos conídios germinaram, contudo, este facto não se reproduziu no ensaio de campo.

Efeito da cobertura do solo com manta Ecoblanket no desenvolvimento das infestantes em pomares de pessegueiros na região da beira interior

Peach production is an important agricultural activity in the center of Portugal, which is the main region of stone fruit production. This region is characterized by hot and dry summers, that can actively accelerate the organic matter degradation and, thus, increase the susceptibility to erosion and decrease the soil capacity to retain nutrients. To evaluate the relationship of peach production activity and soil characteristics, a long-term project was installed based on 31 peach orchards covering the main peach production area. The main objective was to find out the influence of peach production activity on soil characteristics with special reference on organic matter content. Orchards were monitored since establishment, collecting soil samples at establishment time and after 4 years. Plant development was monitored annually by the evaluation of trunk cross-sectional area and nutrition status by foliar analysis at 100 to 120 days after blooming. Simultaneously, weed development in the row and inter-row was evaluated. Results indicated that peach orchards are very heterogeneous over the first years after planting. After 4 years from the initial 31 orchards, only 23 remained, corresponding to 26% of uprooting orchards, mainly related with Pseudomonas syringae complex incidence. In90% of the orchards the soil content in potassium was classified as high (100-200 mg kg-1; LQARS, 2006) and very high (>200mgkg1; LQARS, 2006). Nevertheless, according to nutritional analysis, the leaf potassium content was classified as low in 35% of the orchards, considering the reference interval of 2to 3% for this nutrient. Nitrogen leaf content was below reference interval in17% of the orchards, and in 22% was above this interval. All orchards use weed cover at inter-rows, mowed regularly. Weeds were controlled in rows using herbicides. Considering the 23 orchards, Organic Matter content increased 0.68% in the row and 0.18% in the interrow, after 4 years.