|Alfalfa Stem Nematode
Ditylenchus dipsaci (Kuhn) Filipjev PDF
R. N. Peaden, G. D. Griffin, and J. L. Kugler
Container ...Bench or flat deep enough to allow root
Source ......Nematodes growing on sterile callus
tissue; nematodes are extracted and prepared as a
Plant Age .... 2 weeks.
........Greenhouse flats or bench.
1 Resistant ....No swelling or distortion
Values for resistant standards include totals of l's and 2's.
DISTRIBUTION AND SEVERITY OF STEM NEMATODE
Stem nematode, Ditylenchus dipsaci (Kuhn) FilipjevClick on the map above for a larger version. Se e also the KEY.
|SOURCE OF INOCULUM
Name ........R. N. Peaden
SCIENTISTS WITH EXPERTISE
Name ..... G. D. Griffin
Name ........R. N. Peaden
Name ......J. L. Kugler
CORRELATION TO FIELD REACTION
Field reactions will be similar to greenhouse tests. However, results may be more variable or take longer to develop.
Races of Ditylenchus dipsaci are known to occur. The alfalfa race can parasitize and increase the mortality rate of non-host plants, but no population of the alfalfa race has been found that can reproduce on plants other than alfalfa and sanfoin.
Nematode culture for inoculationcan be obtained from plantsgrowing in the green house or the field. It may be necessary to surface sterilize before proceeding with inoculation (3).
RANGE OF CONDITIONS
Best results are obtained in a high humidity environment. This can be obtained by covering containers with wetted cheesecloth or clear plastic germination domes. A plastic covering over the cheesecloth minimizes evaporation and creates a high humidity atmosphere. A second inoculation with 200 nematodes per plant should be made two weeks after the intial inoculation.
Evaporation retarding agents may be useful in the nematode suspension for inoculation preparation. An environment minimizing loss of soil moisture should be maintained. If flood irngation is used, the soil surface should be as flat and uniform as possible. Avoid uneven watering in flats. Nematodes will become concentrated in low areas.
Inoculate with the nematode suspension directly into the row at the time of seeding before covering the seed. This will result in some resistant seedling death when the nematodes feed at thegrowth point of the seedling embryo.
Mature plants can be screened by adding inoculum directly over the crown buds and covering with soil. Maintain good soil moisture.
1 . Elgin, J. H., Jr., B. D. Thyr, and B. J. Hartrnan. 1984. Stem Nematode Resistance. Pp.30-32 In Standard tests to characterize resistance in alfalfa cultivars. USDA-ARS. Misc. Pub. No. 1434.
2. Griffin, G. D. 1984. Nematode parasites of alfalfa, cereals, and grasses. Pp. 243-321. In Plant and Insect Nematodes. W. R. Nickle, ed. New York: Marcel Dekker.
3. Krusberg, L. R., and S. Sardanelli. 1984. Technique for axenizing nematodes. J. of Nematology. 16:348