CORESTA Congress, Kyoto, 2004, PPOST 06

The prevention of TSWV attack in the Burley fields in Romania

Central Research Station for Tobacco Culture and Industrialization, Bucharest, Romania.
The Burley cultivars are very sensitive to virosis, in general, and to TSWV, in particular.Yield and quality of the obtained tobacco largely depend on the prevention of this virus, and this is managed by the chemical control of Thrips tabaci Lind., the main vector for the spread of the virosis from a plant to another. This virus does not spread through tobacco seed, but it spreads in the field with the tobacco seedling, by the thrips, at high temperatures and low humidity, at transplantation. The most efficient method for the TSWV control is the integrated management of the pest. The chemical control has an important role, followed by the rotation with crops resistant to this pest. The method of biological control, using the biostimulator acibenzolar-S-metal, was one of the objectives during the researches in 2002-2003. The researches were conducted in two different climatic and soil areas, one with higher temperatures and low humidity, on a richer soil, of type chernozem at the Experimental field Biled, county Timis and the other, with lower temperatures and high humidity on an alluvial soil, at the Experimental field Decea, county Alba. The experimental variants were :V1. Acibenzolar -S - methyl 0.01 % c.p. + acetamiprid 0.025 % c.p.; V2. Acibenzolar-S-methyl 0.01% c.p. + imidacloprid 0.04% c.p.; V3. Acetamiprid 0.025 % c.p.; V4 Imidacloprid 0.04 % c.p.; V5. Acibenzolar-S-methyl 0.01% c.p., V6. Untreated check (c.p. = commercial product). The first treatment was made for the tobacco seedling, with 3 - 5 days before transplantation in the field and the second treatment was made after 20 days from transplantation. The observations concerning the phyto - toxicity of the used products were made at three days after the first treatment. The frequency of the attacked plants was determined in the field after the second treatment, for the both experimental fields.Following the researches, the conclusions are : the products used in the period 2002-2003 were not phyto-toxic for tobacco; the frequency of the attacked plants for the untreated check was of 9.7 % at the Experimental field Biled, for the variants acibenzolar-S-methyl plus acetamiprid or imidacloprid was below 1,0 %, for the variant with acetamiprid was of 1.2 % and for imidacloprid was of 1.1 % ; at the Experimental field Decea, for the untreated check, the frequency of the attacked plants was lower, of 6.5 %, the temperature being normal for the area, and humidity was a little bit higher than that recorded at the Experimental field Biled, these being less favourable conditions for the tobacco thrips ; for the both fields, in the variant with acibenzolar-S-methyl, the frequency of the attacked plants was between the values of the treated variants with insecticides and those of the untreated check, of 3.9 % at Biled and of 2.8 % at Decea; this hormone products induce a systemic acquired resistance (SAR) to the tobacco plants; this substance has the capacity of elicitors and systematically induce a defense reaction in the tobacco plants.