High qualified strawberry (Fragaria × ananassa) planting material, mainly for export, is produced by Dutch growers on circa 1100 ha field area in The Netherlands. Planting stock must be destroyed if strawberry tarsonemid mite (Phytonemus pallidus) or infection by the plant parasitic nematode Meloidogyne hapla is found by the Dutch Quality Board. Also the nematode Pratylenchus penetrans can attack strawberry plants severely. The presence of tarsonemid mites in plant material can result in a considerable loss of production. Until 2007 in The Netherlands mother planting stock for runner production was treated with methyl bromide (MeBr) to eliminate tarsonemids. This chemical disinfestation method is banned since 2008. From 2007 the choice was made to optimize the Controlled Atmosphere Temperature Treatment (CATT) to provide a non-chemical and sustainable method for future disinfestation. By application of CATT during 48 h at a temperature of 35°C and 50% CO 2 mortality of the tarsonemid mites is over 99.8%. No harmful irreversible results of CATT on vitality of mother plants in the field and runner production are found. From 2009 CATT is up scaled to a commercial level and widely applied by Dutch producers of planting stock. As a spin-off also plant parasitic nematodes are reduced by application of CATT. Understanding of the influence of different factors during CATT creates also possibilities for optimization this treatment to control P. penetrans and M. hapla in strawberry plants or in the soil particles attached to the roots. Application of an optimized CATT can prevent further dispersion of these plant parasitic nematodes in the strawberry chain.
Abstract. Until 2008 methyl bromide (MeBr) was used in The Netherlands for fumigation of strawberry runners, intended as mother planting stock, to make them free of contamination by strawberry tarsonemid mites (Phytonemus pallidus). As an alternative of MeBr fumigation a 48 h CATT method was developed and scaled up by Wageningen UR in cooperation with the plant propagating association Plantum. This results in an excellent disinfection and a mortality of 99.8% of the strawberry tarsonemid mite. This method provides a healthy production of highly qualified strawberry runners in the field. From 2009 CATT is up scaled to a commercial level and widely applied by Dutch nurseries. In 2011 this CATT method was successfully modified to eradicate also root knot nematodes Meloidogyne hapla (>99.7% mortality), which was not effectively controlled by MeBr fumigation. For an effective killing of the root knot nematodes, temperature must be raised to 40• C. In several experiments the optimum for a high mortality of both tarsonemids and nematodes was studied. This leads into an adapted CATT of 20 hours at a temperature of 35• C and 50% CO 2 followed by 20 hours at a temperature of 40 • C. In 2012 this adapted CATT was successfully upgraded and tested under field conditions.
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