30 F Strawberry Plant De-infestation F www.actpub.co.uk THE FRUIT GROWER • SEPTEMBER 2013 C ontrolled Atmosphere Temperature Treatment (CATT) is a non-chemical and sustainable method of de- infesting plant material from insect pests. Strawberry plants are treated after cold storage and before planting for 48 hours at a temperature of 35C and 50% CO2. This gives excellent de-infestation and 99.8% mortality of Strawberry Tarsonemid Mites, and leads to the production of high quality strawberry runners in the field. Since 2009 CATT has been up-scaled to a commercial level and widely applied by Dutch plant propagators. INTRODUCTION Until 2008 methyl bromide fumigation was used in The Netherlands to de-infest strawberry mother planting stock from Strawberry Tarsonemid Mites (Phytonemus pallidus). After cold storage in early spring the strawberry runners were treated in a specially equipped fumigation chamber. This treatment was highly effective and killed at least 99.8% of the tarsonemid mites. But, because of the unfavourable side effects of methyl bromide on the ozone layer, it was internationally agreed by the Montreal Protocol in 1987 to phase out the use of this fumigant. In the Netherlands this method of fumigating strawberry mother plants was banned in 2008. As an alternative to methyl bromide fumigation the Controlled Atmosphere Temperature Treatment (CATT) was developed and scaled up by Wageningen UR in cooperation with the plant propagating association Plantum (www.plantum.nl). EXPERIMENTS AND RESULTS After a lot of experiments in 2006-2008 it was found that a 48 hour CATT treatment of cold-stored plants at a temperature of 35C and 50% CO2 was most effective. Boxes containing bare-root cold-stored plants (packed in plastic bags to avoid dehydration) in -1.0C storage are removed from the cold store in early March and warmed for 48 hours to 10-12C. Subsequently the plastic bags are removed and the bundles of strawberry plants are placed upright just before CATT treatment. CATT treatment provides excellent de-infestation and 99.8% mortality of Strawberry Tarsonemid Mites (Phytonemus pallidus) (Figure 1). As a side effect, the Two Spotted Spider Mite (Tetranychus urticae) is also eradicated. Plant vigour and establishment in the field after CATT treatment was comparable to plants fumigated with methyl bromide (Picture 1). Recently it was also found that the plant parasitic nematodes Meloidogyne hapla and Pratylenchus penetrans can be considerably reduced by CATT. Clean source material on nematode-free soil prevents an increase in the nematode population, resulting in reduced use of chemical soil disinfectants. In 2011 the standard 48 hour CATT method was successfully modified to eradicate root knot nematodes Meloidogyne hapla (>99.7% mortality), which was not effectively controlled by methyl bromide fumigation. However, for effective CATT: a new method for the de-infestation of strawberry planting stock by Gijs van Kruistum and Hans Hoek of Applied Plant Research, and Jan Verschoor of Food and Bio-based Research, Wageningen UR, The Netherlands.