Tratamiento térmico bajo AC para el control de plagas y nematodos en la multiplicación de fresa

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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. ontrolled Atmosphere Temperature Treatment (CATT) is a non-chemical and sustainable method of deinfesting 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.

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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

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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

THE FRUIT GROWER • SEPTEMBER 2013

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and the new method: shorter treatment of 40 hours and increased temperature in the second phase to 40C. After treatment and a short storage period, the samples, including untreated, were planted on 8 May 2012. The new CATT treatment proved to be equally as successful as the standard method (Picture 2). No differences between the varieties (Darselect, Elsanta, Figaro, Korona, Sonata, Symphony and Honeoye) were observed. The upper limit of 40C is critical during the treatment as just 1.0C over this limit results in clear damage. Uniform temperature distribution during treatment is required, so the plants should not to be packed too tight in the box during treatment. Also sufficient humidification and control of the oxygen concentration is important. It was concluded that no harmful irreversible results of this adapted CATT method on the vitality of mother plants and on runner production were noticed.

SPIN-OFF eradication of root knot nematodes, the temperature must be raised to 40C. In several experiments the optimum for high mortality of both tarsonemids and nematodes was studied. This led to an adapted CATT of 20 hours at a temperature of 35C and 50% CO2 followed by 20 hours at a temperature of 40C (Table 1).

CATT is now a proven commercial method, widely applied by Dutch producers of mother planting stock. It offers production of healthy high quality strawberry runners in the field. Two commercial companies provide the CATT protocol as a phytosanitary treatment of strawberry runners (Picture 3). These companies (Ruvoma, Montfoort NL - email info@ruvoma.nl -

APPLICATION AND CONCLUSIONS In 2012 this adapted CATT method was successfully tested under field conditions with a wide range of mother planting stock, originating from different nurseries. 16 samples of 5,000 to 10,000 strawberry plants, each of different varieties, origin and plant types (SE2, A, A+ and light waiting-bed plants), treated according to the standard method: 48 hours at 35C

and Van Acht Cooling, Sint-Oedenrode NL - email info@vanacht.nl) are treating strawberry plants from outside the Netherlands. The application of the optimized CATT will prevent further dispersion of plant parasitic nematodes in the strawberry production chain. In the international trade in plant materials and products there is further potential for the application of CATT for the sustainable treatment of insect, mite and nematode pests. This is confirmed by the very positive results of preliminary experiments on a range of pests and fresh products at Wageningen UR. ◆ THE FRUIT GROWER • SEPTEMBER 2013

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