Tech. D:l 



LOCATION AND ISOUTION OF NEt4AT0D'?S FRQ-l PLANT TISSU-^S 



A. Direct examination of plant tissues is often an important part of 

 processing the plant sample in order to find nematodes and to dis- 

 cover evidence of their activities. The latter is frequently the 

 only clue to the presence of nematodes of the external-feeding or 

 ectoparasitic type, particularly when an inadequate soil sample 

 accompanies the specimen. The use of the binocular, steroscopic, 

 dissecting microscope aids in examination of the suspected plant 

 parts. Immersing the material in a shallow dish of water is 

 usually necessary when fine root structures are being examined or 

 if looking for nematodes at the plant's surface. 



The typical eel-shaped nematode is usually seen as a glistening, 

 white or translucent form, often first noted because of its body 

 movement. Swollen, sedentary females and cysts are usually opal- 

 escent, but may range in colors from white or yellow to brown. 

 Some forms may be obscured by the matrix of their egg masses or by 

 aggregations of small soil particles adhering to them. Teasing the 

 plant tissues apart is usually necessary. Tissues in advance of 

 lesions may harbor more parasitic forms than in obviously decayed 

 areas. 



Nematode disease symptoms are for the most part not to be considered 

 as having exact diagnostic value because other organisms and con- 

 ditions do cause similar plant responses. The best rule is to make 

 the diagnosis on the basis of the nematode forms recovered from the 

 host tissues or, in the case of root ectoparasites, on the basis of 

 neraatodes recovered from the rhizosphere. However, there is con- 

 siderable value in using plant symptoms as clues to the possibility 

 of plant-parasitic nematodes being involved. Roots are therefore 

 checked for galls, lesions, cortical sloughing, stunting, dead root- 

 tips, and distortions. Foliar parts are checked for lesions, dis- 

 colorations, and distortions. 



B. Isolation of nematodes from pLant tissues can be done in a number of 

 ways, the choice depending upon the kind of nematode involved, the 

 type and size of the sample, and the quantity of nematodes required. 



1. Teasing of suspected diseased plant parts in a watch-glass con- 

 taining water is usually the manner in which plant samples are 

 first examined and nematodes recovered for identification. 



2. Prolonged soaking of small fragments of plant parts in water may 

 be necessary for the recovery of nematodes from light infections 

 or from tissues which have become dry. Breaking or cutting the 

 plant parts into small pieces expedites the release or movement 

 of nematodes from the tissues in all of the methods suggested 

 here. A harmless wetting agent such as Triton may also have value 

 when added to water used for washing or soaking of samples in any 

 of these methods. 



