' ^ \ ^-''' ,i 1893 j ,^ ^— /^ '^ 



Tylenchus and Root-gall. 



(With twenty original figures, on wood, drawn with the camera lucida. ) 

 By N. A. COBB. 



Life Histohy op Tylenchus Arenaeius. 



To the Director of AgriouUiire, 



Sn-, Pretty Oully Scrub, 2t) April, 1890. ' 



I send you u sninll potato showing a disease or parasite that affects the skin. 

 It comes in small knobs at first, and gradually spreads over the potato. I think it is some 

 insect in the ground, as it comes on the roots of the potato first, like knots on a stout 

 thread. On about an acre and a half of ground I sowed two bags of lime and one bag of 

 salt, but it had no effect. It has been in my paddock for the past four or five jears, and 

 is constantly growing worse. It affects parsnips, maiigels, and the roots of the peach 

 trees, and I have seen it on the roots of large Swede turnips ; and I am inclined to think 

 it kills the newly sown turnip. I have sown turnips three times since February ; after 

 coming through the ground they gradually grow yellow and die off. The last time I 

 dusted them with lime just after they broke the ground, but it did no good ; they died off 

 like the rest. My soil is rich scrub land, and I manure it well. It has been under crop 

 for the last twelve or fourteen years. If there is any practical remedy will yon oblige by 

 letting me know at your earliest convenience. I enclose some of the "soil with the potato. 



Yours respectfully, 



William EASsoy. 

 In accordance with Mr. Eas.son's suggestion that it was au insect pest that 

 was giving him so much trouble, the specimens accompanying the foregoing 

 Tetter were forwarded to the Consulting Entomologist of the Department, 

 who reported that the disease was certainly not due to the attack of any 

 insect. The specimen was therefore forwarded to me. After a short 

 examination I wrote to the Director of Agriculture that although the 

 specimen was not such as to permit me to say with certainty, yet from what 

 Icould discover, and from Mr. Easson's description of the manner in which 

 his various crops were afl'ected, I had little doubt that liis land was infested 

 with a destructive Nematode worm, similar to that which has proved so 

 disastrous to the sugar-beet crop in Europe, and that if my suspicion was 

 correct, it was important that the matter be at once and thoroughly investi- 

 gated; and concluded by desiring that further specimens, both of various 

 diseased roots and of surface and sub-soils, should be forwarded to me for 

 further examination. 



In accordance with my request Mr. Easson forwarded various samples, as 

 will be seen by reading the following letter: — 

 To the Director of Agrieid(vn-e. 



Sir, Pn-tty Gully .Scrub, 19 May, 1890. 



I have sent by this nnvil two packets containing samples of soil and root-s — 

 potato, parsnip, and peach-tree roots. The disease can bo clearly seen on the parsnip and 

 potato, and a little on the peaeh-ttco roots. I have seen it nnich thicker on peacli-tree 

 roots than on the sample. The potato is taken from four drills planted about Christmas. 

 They were well dunged with pig-sty manure. The potato was planted on the dung, then 

 covered, then a bag of lime sown on the top in the drills, then covered over again. The 

 four drills were al>out 200 yards long, so I think they had a fair trial of limcj but it ha<l 



