EELWORM GALLS 107 



Aphehnckus Ormerodis Ritz. Bos, also on Strawberries. 

 Herevodera radicicola Greeff, on Cucumbers, Tomatoes, 



Beet, and Clover. 

 HeUrodera Schachtii Schmidt, on Beet, Hops, and various 



Crucifers. 

 Tylenchus Davainii Bastian, on Mosses. 

 Tylenchus devastatrix Kiihn, on Rye, Beans, Oats, Wheat, 



Clover, Hops, and Hyacinths. 

 Tylenchus fucicola De Man, on Algae. 

 Tylenchus graminis Hardy, on Grasses. 

 Tylenchus millefolii F. Low, on Milfoil. 

 Tylenchus tritici Roffredi, on Grasses and Wheat. 



Aphelenchus fragariae causes remarkable enlargement and 

 fasciation of the stems of the Strawberry ; the entire plant 

 is sometimes modified, and resembles a cauliflower. The 

 leaves are more or less deformed, usually with one lobe 

 instead of three. The worms swarm in the tissues, and 

 may be found from April to September. 



Aphelenchus Ormerodis also attacks the Strawberry, giving 

 rise to galls which superficially resemble those caused by 

 A. fragariae, but the affected stems are white, the leaves 

 yellowish, and the worms live between the sheath and the 

 stem. 



Heterodera radicicola causes nodular swellings on the stem 

 of the Common Couch Grass, also on Swede, Tomato, 

 Cucumber, and other cultivated plants. Miss Ormerod first 

 reported the occurrence of this pest, known as the "root- 

 knot " eelworm, in Britain. It causes swellings or "knots" 

 up to 6 mm. in diameter on the rootlets, and larger hyper- 

 trophies on the thicker roots. 



Heterodera Schachtii causes latera.1 swellings on the slender 

 root -fibres of the Cabbage, Turnip, and Charlock, and also 

 does much damage to Beet. Its life-history has been investi- 

 gated by Kiihn. The female may be foimd attached to the 

 rootlets. At her death 300 or more ova are liberated, which 

 at once attack neighbouring rootlets, and give rise to nodular 

 swellings thereon. 



