12. 



Control of Nematode Diseases In Western Europe 



Apart from a few special treatments, such as the hot water 

 treatment of flower bulbs and shallots, and the methylbromide fumi- 

 Tation of seed of clovers, teazel and onions, control of nematodes is 

 >.lone in three ways: /J\rirT7\ 



1) by chemical treatment of the soil /a^ aO'-'^* ^^ 



2) by using resistant varieties of crops 



3) by crop rotation. 



1, Chemical treatment Y^Nv mass. ^''^C^ 



^^ " ^'' v"^.^ 



The possibilities of chemical treatment of the soil in 

 Western Europe are limited by economical and climatic factors. 

 Chemical treatment comes only into consideration for horti- 

 cultural crops and ornamental plants and is always relatively 

 expensive in comparison to the same treatment in the United 

 States of America. 



Of the climatic factors the overall low temperature 

 limits treatment even by the most favorable fumigant, DD, to 

 the summer months. In the Netherlands treatments with this 

 nematicide before April and later than August carry the risk 

 of damage to the plants. Ethylene dibromide and Nemagon are 

 for this reason practically useless. 



Recently Stauffers Vapam and N321 (Crag Mylone) have 

 been tested. On very light sandy soils a very good kill was 

 obtained by treatment in November (SEIKHORST, BIJLOO and 

 KLIimKEnBEHG 19bb, KLInKEWBEF.G and SEINHORST 1936). Econom- 

 ically this is a very favorable time for treatment. However, 

 on other than these very light soils the effect of Vapam was 

 highly insufficient. 



For European conditions a soil fumigant should be active 

 at some 10°C lower than the optimum for DD. 



2. Breeding resistant varieties of crop plants 



The oldest European work on resistance against nematodes 

 was on the resistance of rye against stem eelX'form, but so far 

 thg breeding of red and white clover resistant against stem 

 nematodes (BINGEFORS 1937, FRANDSEN 1951, DIJKSTPA 1936, 1957) 

 and of potatoes resistant against Heterodera rostochiensis 

 (ELLEKBY, I9I18, 1952, TOXOPEUS and DUYSIAN 1952, HUYSHAlM 1936) 

 have been more successful. 



A. Resistance against stem nematodes 



Rye, A few of tho many local rye varieties in western 



