54 EXPERIMENT STATION. [Jan. 



Ekl AYokms on Lettuce {Ileterodera radiclcola 



(Greef.), Mull.). 



BY G. E. STONE. 



There was recently sent into the station a number of small, 

 greenhouse-grown lettuce plants which were badly infected with 

 eel worms. A^jparently the whole crop in a large house was 

 similarly affected. It is quite unusual, so far as our observa- 

 tions go, for eel worms to attack lettuce, the only other instance 

 being about ten years ago, in a greenhouse which had been used 

 for growing lettuce and cucumbers in the usual rotation for 

 some time ; that is, two or three crops of lettuce were grown in 

 the fall and winter, followed by a crop of cucumbers in the 

 sjDring and early summer. We have frequently grown lettuce in 

 soil which was badly infested by eel worms without the slightest 

 indication of root infection. This has been the experience of 

 many growers, inasnnich as eel worms occur in numerous 

 houses devoted to lettuce growing. 



In the house previously referred to as being contaminated 

 with nematodes^ ten years ago, the lettuce plants were infected 

 only once, notwithstanding the fact that eel worms were in the 

 soil for quite a time both before and after this infection. 



The nematode^ {Ileterodera radiclcola (Greef.), Midi.) is 

 known to affect a very large number of plants, and it evidently 

 has decided preferences as to its host. Such plants as cucum- 

 bers, melons, tomatoes, roses, violets, mustard, rape, etc., are 

 always susceptible, but why eel worms should attack lettuce 

 only at certain periods, nnd thou severely, is a mystery. 



A recent correspondent writes ns from the south that his 

 carnations have been badly affected by eel worms, but we have 



* Nematodes are also known aseol worms. 



