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July 9, 2004
From: European and Mediterranean Plant Protection Organization (EPPO)
Reporting Service 2004, No. 05 [edited]

2004/077
Surveys on quarantine pests done in Bulgaria from 2001 to 2003

From 2001 to 2003, official surveys were carried out in Bulgaria on the following pests:

Potato pests
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Potato cyst nematodes: _Globodera pallida_ [Gp] and _G. rostochiensis_ [Gr] (both EPPO A2 list).

From 2001 to 2003, potato samples were analyzed for the presence of these 2 nematodes.

Samples were collected as follows:

- 2001: 188 samples from 1395.114 tons of imported seed potatoes; 265 soil and 164 tuber samples from 261.91 ha of seed potato production areas.
- 2002: 250 samples from 2313.93 tons of imported seed potatoes; 351 soil and 146 tuber samples from 151.9 ha of seed potato production areas.
- 2003: 321 samples from 2757.575 tons of imported seed potatoes, 392 soil and 201 tuber samples from 247.25 ha of seed potato production; 340 soil samples from 571.68 ha of ware potato production areas.

Gp was never detected during these surveys (there had been some records in the past, see EPPO RS 98/122). Gr was found in several samples corresponding to a total area of 96 ha. On these infested plots, cultivation of seed potatoes, and any other propagation material, is prohibited.

Gp: Absent, found in the past but no longer present, confirmed by survey.
Gr: Present, found in a few areas (96 ha total), under official control.

Other potato nematodes: _Ditylenchus destructor_ [Dd] (EU Annexes), _Meloidogyne chitwoodi_* [Mc], _M. fallax_ * [Mf] (both EPPO A2 list).

From 2001 to 2003, potato samples were analyzed for the presence of these nematodes.

Samples were collected as follows:

- 2001: 45 samples from 1395.114 tons of imported seed potatoes; 164 tuber samples from 261.91 ha of seed potato production areas.
- 2002: 250 samples from 2313.93 tons of imported seed potatoes; 146 tuber samples from 151.9 ha of seed potato production areas.
- 2003: 128 samples from 2757.575 tons of imported seed potatoes, 165 tuber samples from 247.25 ha of seed potato production.

Dd: Present, found sporadically in small areas (0.5 ha in 2002).
Mc, Mf: Absent, confirmed by survey.

Tomato spotted wilt tospovirus and Stolbur phytoplasma (on potato).

From 2002 to 2003, ELISA were performed on 388 plant samples from 399.15 ha of seed potatoes. Tomato spotted wilt tospovirus was detected in 2 samples in 2003. Stolbur phytoplasma was found in 2 samples in 2002. Infected crops were downgraded as ware potatoes.

Source: NPPO of Bulgaria, 2004-05.

[Both Gp and Gr are at very low levels. Of all the crop pests worldwide, Gr is one of the most difficult to control. Once established, it is difficult to eradicate, because the nematodes survive for up to 30 years as eggs protected by the durable cyst wall. The strategy for limiting spread, once the potato cyst nematodes are introduced, is to integrate control measures, in particular, the use of pesticides, resistant varieties, and crop rotation.

Gc can be controlled using seeds of 3 cultivars, segregating for resistance to 2 pathotypes of Glr (Ro1 and Ro2) and 2 pathotypes of Gp (Pa2 and Pa3), that have been released by Cornell University and USDA/ARS. The resistance is suitable for North American production, and was developed as a preemptive safeguard that could be used if pathotypes of Gp, which are prevalent in many other potato production areas of the world, are ever introduced into North America. The combined resistance in this germplasm is from _S. tuberosum_ ssp _andigena_ and _S. vernei_.

References:

<http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G053S1.HTM#Management:>
<http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G053s2.htm>
- Mod.DH]