Groen en groente : kansen en risico's groen-blauwe dooradering voor de vollegronds groenteteelt

We described risks and chances of Green-Blue Veining (i.e. land and water non-crop elements) in the agricultural landscape for vegetable cropping, as to insect pest outbreaks, and pest control by natural enemies, respectively. The possible role of Green-Blue Veining as a source of pest development seems small as compared to other sources, such as crops rests, plant material, other cropfields, winter crops, etc, but could not be excluded. The physical risk that high woody elements, such as hedges and tree lines may concentrate individuals of pest species at the lee side, where consequently pests may develop, cannot be excluded, too. In addition, the risk that higher field temperature as a consequence of windbreak may favour pest species more than natural enemies, cannot excluded. The only remedy is making conditions for natural enemies as favourable as possible. Moreover, high woody windbreaks favour crop growth. Alternative wild host plants for thirty pest species have been listed, risks described, and prevention measures proposed. Ecological conditions for natural enemies have been listed, qualitative, quantitative and spatial conditions as well. Optimalisation of lay-out and management of Green-Blue Veining by minimising conditions for pest species as well as maximising conditions for enemies seems prospective. Many studies at the landscape level, or including landscape parameters as independent variables show a positive correlation between pest control and/or enemy abundance at the one hand, and area of Green-Blue Veining and nature, and landscape patchiness at the other hand. There are a few minor exceptions, with no effect (two datasets) or a reverse effect (two datasets) by a part of Green-Blue Veining combined with a pest controlling effect of the complementary part. A negative correlation with total area of nature and/or of Green-Blue Veining has not been found. A lot of reserach on this topic is still going on, and there are many open questions to answer. Therefore, it has been concluded preliminary that - provided ecological conditions are optimal - chances of Green-Blue Veining as the basis condition for pest control by natural enemies exceed its risks as a source for pest outbreak. Therefore, this pest-controlling function of GBDA may be considered as a life support function, as a service from nature to agriculture