STRAWBERRY NURSERIES: SUMMARIES OF ALTERNATIVES AND TRIALS IN DIFFERENT GEOGRAPHIC REGIONS
| Autor: | S.W. Mattner, R. C. Mann, R. K. Gounder, Ian Porter |
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| Rok vydání: | 2006 |
| Předmět: | |
| Zdroj: | Acta Horticulturae. :187-192 |
| ISSN: | 2406-6168 0567-7572 |
| DOI: | 10.17660/actahortic.2006.708.30 |
| Popis: | Worldwide, only a limited number of trials have been conducted in the strawberry nursery industry to investigate alternatives to methyl bromide (MB) for soil disinfestation, in contrast to the large number conducted in the strawberry fruit industry. Moreover, the development of alternatives for nurseries is proving more difficult than for the fruit industry because of the higher levels of pathogen, weed and nematode control that are required. Consequently, many strawberry nursery industries from around the world have applied for, and been granted, critical use exemptions (CUE) from the MB phase-out, on grounds that there are no technical alternatives to soil fumigation with MB for runner production. The physical properties of alternative fumigants generally make application more difficult. The most promising, commercially-available alternatives have difficulty in achieving acceptable efficacy against pests, and in matching yields, plantback times, and propensity to cause crop phytotoxicity. Despite this, in three key regions, 1,3-D/Pic and Pic alone have resulted in significant reductions in pathogen populations and disease incidence equivalent to that with MB/Pic. Furthermore, preliminary results in Australia with cyanogen and methyl iodide/Pic indicate that these products may offer better results than previous alternatives evaluated because their physical properties are more similar to MB. In several regions of the world e.g. northern Europe, plug plants (containerised transplants produced in soilless media) have gained acceptance for many short season strawberry crops. Plug plants decrease growers' reliance on soil fumigants because they reduce or eliminate the need for production in soil. However, the broad-scale adoption of plugs for long season production is proving difficult, owing to a lack of knowledge of the altered physiology of plug plants and their higher cost. In spite of the variable results obtained with alternatives, use of virtually impermeable films (VIFs) has halved the amount of 1,3-D/Pic required for effective soil disinfestation in Spain, and also offers a means to reduce the amount of MB/Pic required for soil fumigation and global emissions of MB. INTRODUCTION Worldwide, most strawberry nursery plants are produced under phytosanitary controls or 'certification', where regulations generally require that soils be disinfested. Effective soil disinfestation is extremely critical for the strawberry nursery industry as it ensures the production of 'certified' transplants that minimise the spread of diseases to the strawberry fruit industry. Methyl bromide/chloropicrin mixtures have been adopted throughout the world because of their broad-spectrum control of pathogens and weeds, their ability to induce an 'increased growth response' in crops, and their ease of use. The most, prominent pathogens controlled include those that cause major loss in the fruit industry viz. Phytophthora spp., Verticillium dahliae, Pythium spp., Rhizoctonia spp., Cylindrocarpon spp., and Fusarium spp. (Duniway, 2002). Finding alternatives to MB for the strawberry nursery industry worldwide is proving more difficult than for the strawberry fruit industry because of the complex number of factors that needs to he taken into account when adopting an alternative. The volatile naProc. 0 Int. Strawberry Symposium Ed. G. Waite Acta Hort. 708, ISHS 2006 187 ture of formulations of methyl bromide/chloropicrin (MB/Pic) mixtures provides growers with an easy and reliable method of fumigation in a wide range of climatic conditions, soil types and cropping conditions, and this has ensured that strawberry nursery and fruit industries have remained highly productive. Most alternative fumigants have higher boiling points and lower vapour pressures than MB, and therefore do not move through soil profiles as readily as MB. This factor is often exacerbated in regions where strawberry nursery transplants are grown because of the climatic conditions that are required for their production i.e. high elevations and/or low temperatures, and high soil moisture. This paper discusses some of the issues that need to be overcome to increase the rate of ado tion of alternatives in strawberry nursery industries. INDUSTRY REQUIREMENT FOR METHYL BROMIDE The strawberry nursery industry relies on rigorous screening of varieties for high health, which includes virus testing of nuclear material and routine soil disinfestation. At present, three of the four generations (nuclear-foundation-mother-runners) are grown in disinfested soils to ensure that disease does not increase progressively through the multiplication process. In spite of this, nursery plants have been shown to contain low levels of specific diseases such as P cactorum even with the use of MB/Pic mixtures (DeCal et al., 2004). Most of the nuclear stock is produced in hydroponic substrate systems, and in some countries with smaller crop production there is potential for the next generation foundation stock to also be produced in hydroponics. To date, only a small proportion of mother stock and runners ( |
| Databáze: | OpenAIRE |
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