Paras . C : 1 



MEADOW OR ROOT-LFSION NEMATODES (PRATYLENCHUS SPP.) 



The genus Pratylenchus is made up of several species, all of which are 

 known plant parasites. As a group, these nematodes are widely dis- 

 tributed, have an extensive host range, and rank as one of the most 

 important plant-parasitic genera. All old host lists should be used 

 with caution because considerable changes have been taking place in 

 the taxonon^r of this group. A monograph (Sher and Allen, 1953) revis- 

 ing the genus and adding three new species to it has marked the begin- 

 ning of more attention being paid to the taxonomy of these important 

 parasites in various parts of the world. Additional new species were 

 described along with a study of morphological variation within certain 

 of the species (Taylor and Jenkins, 1957) in a paper. It also contains 

 some very worthwhile suggestions regarding consideration of morpho- 

 logical variation and their expression which ought to be considered by 

 anyone doing taxonomic work, particularly with economically important 

 genera which will be intensively studied for many years to come. 



The useful, but now outdated, key to Pratylenchus species from Sher 

 and Allen (1953) is furnished in these Notes. In addition there is 

 given a listing of the Pratylenchus spp. to date with citations where 

 information can be obtained. It is suggested that forms which may not 

 be identified readily be sent to workers who are specialize ng in the 

 taxonomy of this genus. 



The Pratylenchs are primarily root-parasites and may be endo- or ec to- 

 parasitic in habit. Infections may give rise to disease symptoms of 

 various kinds according to the hosts involved. In general, the damage 

 resulting is what would be expected of a plant debilitated ty increas- 

 ing amounts of root injury and loss. In boxwoods, a characteristic 

 bronze coloration of the foliage has been noted, and foliar discolora- 

 tions in other kinds of plants may also suggest the below-ground pres- 

 ence of these nematodes. 



Meadow nematodes in various stages of their life cycle are to be found 

 in soil samples. These nematodes are known to evacuate root tissues 

 which are decaying, and thus may be overlooked if root examination 

 alone is relied upon. Infected roots may be stunted and show spots, 

 streaks, or encircling bands of discolored necrotic tissue. These 

 symptoms are not exclusive for Pratylenchus , although they are usually 

 found when these nematodes are the parasite involved. The nematodes 

 can enter into the root tissues, migrate within the root, and complete 

 their life cycle. The external feeding sites, places of entry, and 

 other damaged areas of the root may serve as portals of entry for other 

 infective soil microorganisms. 



It is important to remember that these nematodes usually leave roots 

 when decay sets in and that most of the species are reported to be 

 unable to withstand drying. Both of these factors can effect chances 

 of finding the nematode in older infections or in samples of soil and 

 plants which become dry before being processed. 



