Phytoplasma Flavescence dorée (FD) is transmitted in vineyards by leafhopper Scaphoideus titanus, which is the only known vector of this disease. Dispersal of vector and phytoplasma to regions distant from focal points is primary through infected planting material. Presence of infected grapevine plants and vector are primarily responsible for epidemic of this disease. In regions where FD is present, dispersal dynamic by vector is 5-10 km a year (EPPO-dsqpFD). Spontaneous spread of phytoplasma and vector is of great importance in Serbia, considering the numerous extensive vineyards.

 All European countries affected with epidemic of FD defined strict rules, primary concerning the control measures against leafhopper S. titanus and eradication of infested plants. Monitoring and control of vector, as a monophagous species leading to great epidemics in vineyards with severe loses, represents the most important measure of control and prevention. Epidemic situation complicates by the fact that symptoms start to express 1-2 years after initial infection. Thus, success in eradication of disease and improvement of phytosanitary situation can  be estimated in third year after control measures had been carried out. Conventional measures include phytosanitary inspection of vineyards and elimination of infected vines (in some cases removing plant parts with localized symptoms), destroying natural reservoirs of phytoplasma, monitoring and control of vector.

Suggested measures of control and prevention of FD vector S. titanus in vineyards of Serbia are based on experience of other countries dealing with problem of grapevine yellows and control measures they conducted, as well as, positive results in control of FD. This problem is covered by special instruction by Plant Protection Head Office, at Ministry of Agriculture in Serbia. In regions where presence of FD was confirmed by PCR analysis (focal points), following measures must be carried out: 

1. Eradication and burning down infected vines at the end of grapevine vegetation.
2. Monitoring the appearance of first symptoms during vegetation and elimination of all suspicious vines.
3. Monitoring the appearance of Scaphoideus titanus and other potential vectors.
4. Destroying “wild grapevine” in narrow and wider surroundings before chemical treatments.
5. Destroying abandoned vineyards in narrow and wider surroundings or in mother plant vineyards.
6. Control of S. titanus larva with contact insecticides (2 treatments in interval of 10 days), during second half of June in all vineyards where vector is present. In mother plant vineyards, as well as in propagation vineyards, number of treatments must be higher (control of imagoes after their emergence, 3   treatments in intervals of 10 days).
7. Regular inspection of mother plant and propagation vineyards on presence of phytoplasmatic plants and vectors.
8. Regular inspection of mother plant and propagation vineyards on presence of S. titanus and detection of phytoplasma with PCR analysis.
9. Inspection of grapevine grafts with PCR method on presence of phytoplasma.
10. Inspection of grapevine grafts on presence of Scaphoideus titanus eggs.

Measures from 1 to 6 must be conducted by all owners of vineyards, while measures from 7 to 10 will be assigned to authorized Regional Plant Protection Services.

According to phenology of S. titanus in Serbia, in endangered regions where appearance of FD could be expected, chemical treatments must be carried out between June 10 and 20, when population of S. titanus mainly consists of larval instars (L2-L5). Suggested period for treatments overlaps with emergence of leafhopper Hyalesthes obsoletus, vector of Stolbur phytoplasma, covering that way control of vectors of two most important phytoplasmas in vineyards of Serbia. Last few years, progressive dispersal of Stolbur phytoplasma was registered in vineyards of south and southeast Europe, with threatening attributes of epidemic (Batlle et al., 2000; Palermo et al., 2004). Selection of proper time for treatments can vary in relation to weather conditions, but following must be previously taken into consideration:

• larval instars are inert and don’t leave the host plant
• larval instars are more susceptible to insecticides
• determined chemical treatments against larva prevent emergence of imagoes infected with phytoplasma and their dispersal to neighboring plants and vineyards
• Persistence of suggested insecticides is 10-15 days, enabling protection of treated plants for period of 25 days, during massive activity of Scaphoideus titanus, with possibility of protection even longer, against later hatched L1 larva.
• Control of S. titanus in stage of imagoe can cause effect of "induced dispersion", i.e. escape of imagoes from treated vineyards.
• Chemical treatments in second half of June, besides elimination of Scaphoideus titanus, can also have negative influence on population density of leafhoppers Hyalesthes obsoletus and Reptalus panzeri vectors of Stolbur.

• Considering the insecticides application technique in extensive vineyards (manual atomizer), control of S. titanus larva can give satisfying results.

 Proposed insecticides gave positive results in control of FD vector in preliminary experiments. In regions where S. titanus is present, 2 treatments during second half of June are enough, while in focal regions, third treatment is necessary, 10-15 days after second.

Work program for 2005 and 2006 includes complex survey of biology and ecology of S. titanus in Serbia, as well as, adequate chemical control measures, including alternative methods, especially biological. Results of this investigation will explain problem with selection of right time and number of treatments, effective insecticides and their side effects. Control of vector in larval stage seems most effective solution, considering the unknown status of phytoplasmatic plants on numerous localities where the vector is present. Number of treatments can be higher in endangered regions, mother plant vineyards and in process of planting material production.   

In experimental conditions S. titanus was detected to transmit chrysanthemum phytoplasma (CY phytoplasma 16SrI-B), from infected chrysanthemum to grapevine (Alma et al., 2001). Besides that, FD is successfully transmitted by vector from grapevine to clover, and reverse, from clover to grapevine (Alma et al., 1993). FD phytoplasma has been recently detected for the first time on Clematis vitalba in Italy (Angelini et al., 2004). Clematis vitalba is close to grapevine and common species in vineyards in Serbia, hence, represents natural reservoir of this phytoplasma. During conducted survey, infected Clematis vitalba plants with phytoplasmatic symptoms were registered on several localities in Serbia. Samples of these plants will be analysed with molecular method and results could be very important for identification of FD in native flora. Accidental introduction of FD from native flora to vineyard, by polyphagous cicadas, can reach dramatic level if some of them are monophagous, such as  S. titanus or polyphagous vectors with preferences to grapevine (Cixiidae spp.). In that case, monophagous cicada could be responsible for further transmition of inoculum from infected to healthy grapevine. Latest investigations showing rise in number of phytoplasmatic plants in vineyards of Hungary (Palermo et al., 2004) indicate that besides bindweed (Convolvulus arvense), main source of Stolbur phytoplasma is nettle (Urtica dioica) and some species from the family Solanaceae. Therefore, besides suggested control measures, in and around vineyards, it’s important to destroy all weeds and wildly growing grapevine, as potential reservoirs of phytoplasma inoculum for infection of vectors.

Alma A., A. Arzone and D. Bosco (1993). Grapevine MLO transmission by insects. Extended abstract 11th Meeting ICVG. Montreux. Switzerland. 6-9 September, 1993 (Federal Agricultural Research Station of Changins. Nzon. Switzerland), 84-85.

Alma A., S. Palermo, G. Boccardo and M. Conti (2001). Transission of Chrysanthemum yellows, a subgroup 16SrI-B phytoplasma, to grapevine by four leafhopper species. Journal of Plant Pathology, 83 (3):181-187.

Angelini A., F. Squizzato, G. Lucchetta and M. Borgo (2004). Detection of a Phytoplasma Associated with Grapevine Flavescence dorée in Clematis vitalba. European Journal of Plant Pathology, 110 (2): 193-201.

EPPO-dsqp: http://www.eppo.org/QUARANTINE/bacteria/Flavescence_doree/PHYP64_ds.pdf

Palermo S., M. Elekes, S. Botti, I. Ember, A. Alma, A. Orosz, A. Bertaccini and M. Kölbe. 2004. Presence of Stolbur phytoplasma in Cixiidae in Hungarian vineyards. Vitis, 43(4): 201-204.

Department of Plant Pests, Institute for Plant Protection and Environment Belgrade

Banatska 33, Zemun, tel/fax: 011 2611 762, E-mail: titanus_serbia@hotmail.com