|Cysts on a potato root.|
Species of Globodera have several pathogenic types and occur over much of the world. They have been identified in at least 58 countries. The potato cyst nematode of major concern in North America is G. rostochiensis or the golden cyst nematode which is characterized by gold-colored females. It is under strict quarantine regulations in North America. A related species, identified in 2006 in a field in Idaho, is G. pallida or the pale cyst nematode. Females of this species are characterized as being white or creamy colored.
Eggs of G. rostochiensis hatch due to a stimulant released by potato roots into the soil. At first, juveniles develop within the female. The female gradually turns from white to creamy yellow to gold, and upon death a dark brown cyst forms. From the cyst, juveniles emerge and enter the root system in which they feed. After cycling through three to four juvenile stages, the male leaves the root with a wormlike appearance. Females are spherical; they grow and rupture through the root, protruding their bodies outwardly. Males mate with the protruding female. The time from eggs to adults is between 38 and 48 days depending on temperature and there is one generation per season. Population increase between generations is 12 to 35 fold.
Symptoms and Damage:
Vine symptoms due to infection are similar to that of plant under water stress. There is chlorosis, then wilt and finally early death. Potato roots have small cysts that are dark brown and encapsulate 200 to 500 eggs. Cysts are the bodies of dead females that retain viable eggs. The cysts can persist in the soil for 20 years. Heavy infestations can result in total crop loss of potato. G. rostochiensis has been reported to cause synergistic losses with Rhizoctonia solani and Verticillium dahliae.
The primary method of managing the golden cyst nematode is through strict quarantine regulations. This nematode has been under these regulations on Long Island, NY, and recently the nematode has been identified in Quebec and Alberta, Canada. G. rostochiensis spreads readily through the transport of infected soil on seed tubers, equipment and containers. Planting infected seed tubers will spread the nematode into the soil. Once the nematode is established in the soil, it is nearly impossible to eradicate. Some varietal resistance is known due to a gene bred into a few commercial varieties but is effective only against some pathogenic types of G. rostochiensis and G. pallida. The host range of the golden nematode is limited to tomato, eggplant and a few Solanaceous weeds. Crop rotation is effective and the rotation interval depends on the degree of infestation. Fumigation has been used for quick and drastic reduction in populations. Currently in the U.S.A. there is no non-fumigant nematicide available. Biological controls have not shown much success. Management practices for controlling an infected field requires an integrated approach using various methods over many years. The best approach is not to plant any seed tubers from an infected field or move any equipment off infected fields or storage onto a clean field or into clean storage. Observe quarantine procedures.
Female pale cyst nematode (G. pallida)
Male pale cyst nematode (G. pallida)
Nematodes in Potato: