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Meloidogyne incognita and M. javanica galls on sugar beet tap root
Photograph courtesy of Mariana P. Beckman, DPI

Nematology Section

Compiled by Jason D. Stanley, M.S., Maria de Lourdes Mendes, Ph.D., Renato N. Inserra, Ph.D., and Janete A. Brito, Ph.D.

This section analyzes soil and plant samples for nematodes, conducts pest detection surveys and provides diagnosis of plant problems, in addition to completing identification of plant parasitic nematodes involved in regulatory and certification programs. State of Florida statutes and rules mandate the principal part of the regulatory activity of the section. Analyses of plant and soil samples include those from in-state programs, plant shipments originating in Florida destined for other states and countries, as well as samples intercepted in Florida from outside the United States.

Nematodes of Special Interest

Foliar nematodes of the genus Aphelenchoides are common in Florida and parasitize both ornamental plants and horticultural crops such as strawberries. These nematodes are also able to feed on fungi and can be reared in dishes containing fungal mycelia in appropriate media. The most economically important species of these nematodes are A. besseyi, A. fragariae and A. ritzemabosi. Ornamentals infected by these nematodes are unmarketable due to defoliation and leaf damage. Symptoms include necrosis, chlorosis, discoloration and distortion of leaf tissues. In addition to causing leaf damage, these species can also infect flowers to induce flower abortion. Nematode infections are favored by persistently humid conditions and drops of water on plants. These conditions support nematode movement from the soil to the plant leaves and subsequent penetration and invasion of the leaf tissues. Cultural practices to reduce excess moisture on the foliage, such as encouraging good ventilation, avoiding overhead irrigation, use of clean stock and rigorous sanitation practices, can help prevent infection by these damaging nematodes.

Beta vulgaris L. (sugar beet) is an industrial crop commercially grown in mainly temperate climates for sugar production due to its high concentration of sucrose in the tap root. Worldwide, the three largest producers of sugar beet are the European Union, Russia and the United States. In the Unites States, over 1,000,000 acres of sugar beets were harvested in 2008 from California, the Pacific Northwest and other temperate states. Sugar beets are not a major crop in Florida, but the related table beets (Beta vulgaris) are often grown in home gardens in many areas of the state. Many root-knot nematode species parasitize sugar beet and could threaten table beets. In Florida, Meloidogyne incognita and M. javanica are the most damaging species. They induce large galls, necrosis and proliferation of small fine feeder roots that are also significantly galled. The distorted and malformed tap roots that result from the root-knot nematode infection are neither palatable nor marketable. Examples of root-knot nematodes recently found on sugar beets are listed below.

Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949, (the southern root-knot nematode) was found infecting the roots of Beta vulgaris (sugar beet). (Marion County; N09-01260; Dr. Maria de Lourdes Mendes, University of Florida; 20 October 2009.)

Meloidogyne javanica (Treub, 1885) Chitwood, 1949, (the Javanese root-knot nematode) was also found infecting the roots of this industrial crop, Beta vulgaris (sugar beet). (Marion County; N09-01260; Dr. Maria de Lourdes Mendes, University of Florida; 20 October 2009.)

Collectors submitting five or more samples that were processed for nematological analysis in September - October 2009