gestione della vegetazione spontanea nelle colture frutticole

Orchards weed management is frequently based on periodical mowing of vegetation between the rows and herbicides application under the trees. This last technique can count nowadays with few herbicides, since several efficient active ingredients have been excluded from the Integrated Production Management because of their high toxicity and prolonged persistence in the environment. The study comprised two tests: 1. ¿Low toxic herbicides comparison¿ (Table 1), aimed at finding strategies for chemical weed control that satisfy both environmental sustainability and efficiency requirements. In order to delay as much as possible weed growth, the convenience of adding a residual herbicide application in fall or in early spring was assessed. 2. ¿Comparison of alternative techniques for weed control¿ (Table 2), aimed at identifying techniques to improve chemical weed control strategies and at assessing the efficiency of weed control strategies alternative to the use of chemicals. Efficacy of herbicides application without water, tillage, mowing and pyroweeding was therefore assessed. Both tests were conducted in Manta (Cn). The apple orchard selected for the study belonged to a medium size farm, representative of western Piedmont fruit production area in terms of production techniques. Test n.1 was run in years 2007/08 and 2008/09, test n.2 in 2008/09. Weed analysis was conducted for both tests by recording soil cover (%) and weed density (plants m-2). Fruit size was recorded at harvest. Test n.1 - low toxic herbicides comparison showed a high efficiency of mixtures containing glyphosate and a residual herbicide both when distributed in fall and in spring. Applications with glyphosate + oxadiazon in early autumn, the ones with glyphosate + flazasulfuron in late autumn and the ones with glyphosate + pendimetalin in early autumn significantly controlled weed growth until late spring. Glyphosate and flazasulfuron mixture showed poor efficacy in perennial weeds control, such as Cynodon dactylon. Differently, glyphosate and pendimetalin mixture was very efficient in controlling perennial weeds, Epilobium spp. being the only exception. Epilobium spp. is known however to be scarcely sensible to glyphosate. Application of glyphosate and carfentrazone mixture in late spring showed a good efficacy in controlling most of weed species, except than Epilobium spp. Test n.2 - comparison of alternative techniques for weed control highlighted tillage and mowing as valid strategies for weed control. Tillage is efficient in weed control and it only requires three interventions, same as chemical strategies do. Mowing thoroughly controlled weed growth but it required four interventions. It is important to underline that an increase in the presence of Portulaca oleracea was assessed in both mechanical theses, due to the fragmentation of Portulaca individuals already present in the field. Pyroweeding and application of glyphosate at very low volume required five interventions and did not show relevant results. The efficiency in weed control of glyphosate at very low volume was much lower than for glyphosate at normal volume, possibly because of an incorrect adjustment of product spraying technique. In both tests no significant correlation was found between treatments and fruit size.