Increasing high quality production of organically grown apples through asystem's approach including management of Vf scab resistance.

摘要

Gross organic apple production/ha and percentage class 1 fruit are too low to ensure increase of organically grown apples in The Netherlands. Pesticide use in organic apple production in North-West Europe does not fit with consumers expectations. In an experimental orchard of Applied Plant Research Fruit (PPO-Fruit) at Randwijk, The Netherlands, a production system was tested to increase high quality production and reduce the use of organic pesticides, especially against apple scab. The new cultivars 'Santana' and 'Topaz' were used. These cultivars are Vf scab-resistant and have a low need for thinning. A scab resistance management system was developed to prevent the loss of Vf scab resistance. Only five to ten sprayings of sulfur per year against scab and powdery mildew were applied and no other organic pesticides such as copper and lime sulfur against scab and mildew were used. This is low compared to the Dutch average of 20-30 sprayings. It appeared that 'Santana' was not susceptible to rosy apple aphid and other aphids. Other pests and diseases were controlled according to the Dutch organic standards. After 7 years, the orchard was still scab-free although scab was present in other organic orchards in the vicinity of the experimental orchard. Other experiments with Vf scab-resistant management show the additional importance of planting exclusively Vf-resistant cultivars in Vf orchards, spacing and the use of fences between Vf and the neighbouring orchards using fungicide treatment at infection peaks. Gross production of the experimental orchard in Randwijk was high (average 45 t/ha for 'Santana' and 37 t/ha for 'Topaz' in the 3rd to 7th growth years), compared with the Dutch average (23 t/ha). The average percentage of class 1 fruits over the years for 'Santana' was 69%. For 'Topaz' the percentage of class 1 fruits dropped from 75-79% in the first three years to 25% in the last year. This was due to russeting of the stem cavity.