Plant Sanitation. 



222 



[March, 1012, 



Since the last edition, the names of 

 nearly 200 Roses have been added to the 

 list at the end of the book, which gives 

 for each variety a reference to the 

 instruction suitable for its treatment. 

 This list is interesting from another 

 point of view, for it is probably a fairly 

 • 



complete enumeration of the Roses now 

 commonly cultivated in gardens. Taken 

 all round, this little book is, perhaps, 

 one of the most useful and generally 

 appreciated of the National Rose So- 

 ciety's publications.— White Rose. 



PLANT SANITATION. 



NOTES BY THE GOVERNMENT 

 ENTOMOLOGIST. 



E. Ernest Green, f.e.s. 



Eel-worms.— Some tea seedlings have 

 been sent in from the Ambawella dis- 

 trict, with the characteristic symptoms 

 of eel-worm infection. The collar and 

 tap-root are irregularly thickened and 

 rugose, the bark being of a corky tex- 

 ture, with many decaying cavities. On 

 stripping off the diseased bark of these 

 roots many eel-worms are exposed, some 

 of them in the encysted condition of 

 Heterodera, but others of a worm-like 

 form, 



My correspondent reports :— " In my 

 nurseries the leaves of the small plants 

 turn yellow, and— when such plants are 

 pulled up— their tap-roots are found to 

 be eaten through. No big plants suffer. 

 This disease runs right through some of 

 the beds." 



In the ' Tropical Agriculturist ' of July 

 and August, 1909, a similar attack is des- 

 ciibed, and photographs of the injured 

 roots of tea seedlings are shown in the 

 November number of the same volume. 



This pest, so far as tea is concerned, 

 appears to be confined to quite young 

 plants. As soon as the taproots have 

 penetrated to the deeper layers of the 

 soil they appear tc be immune from 

 attack. I have never seen any signs of 

 trouble from eel-worms on older plants 

 in the field. Though principally a pest 

 of the nursery, it is possible that plants 

 grown from seed at stake, in infected 

 soil, might suffer. 



When once the pest has appeared in 

 the nursery, it is useless to attempt to 

 save the younger plants. The larger 

 plants, that have already formed strong 

 taproots, may be planted out with 

 safety, after which the remaining seed- 

 lings (in the infested beds) should be 

 pulled up and burned. The ground 

 should then receive a heavy dressing of 

 quick-lime and be allowed to lie fallow 

 tor some months, — the longer the better. 

 It is said that the young worms are able 

 to remain alive in soil devoid of vegeta- 



tion for months, apparently without 

 taking any nourishment. When fresh 

 plants are placed in such infested soil, 

 the worms enter the rootlets and feed 

 upon the tender tissues. When fully 

 grown, the females become encysted and 

 assume a globular or pear-shaped form, 

 and develop large numbers of eggs. 

 The resulting young worms usually 

 leave that plant and wander in the soil 

 in search ot fresh rootlets. 



One of the principal causes of trouble 

 in tea nurseries is the bad habit of utiliz- 

 ing the same ground for several consecu- 

 tive years, during which time the eel- 

 worms become more and more concen- 

 trated in the soil. No damage may have 

 been noticeable during the first year, 

 though it is probable that a few isolat- 

 ed plants may have been attacked. 

 During the process of making up the beds 

 for the second year, the infected soil is 

 distributed over a wider area, with the 

 result that a larger number of plants are 

 attacked and thousands of young worms 

 are liberated from them. In the third 

 year, by a similar process, whole beds 

 may be affected, when the resulting 

 damage to the seedlings is at once 

 patent. 



Thorough dessication of the soil has an 

 inhibitive effect upon the development 

 of the worms. The old-fashioned plan 

 of burning the soil to be utilized in 

 nurseries would be a still better safe- 

 guard. Another method of disinfecting 

 soil has been suggested in a Bulletin 

 issued by the United States Department 

 of Agriculture. It is there advised that 

 seed beds and nurseries should be steri- 

 lized before planting by means of For- 

 maldehyde (commonly known as For- 

 malin). The treatment is described as 

 follows :— 



"The formaldehyde method consists 

 essentially of treating the soil with a 

 weak solution of 1 part commercial for- 

 maldehyde. It has been found that 

 a solution of 1 part commercial form- 

 aldehyde in 100 parts of water is effec- 

 tive against the root-knot nematode in 

 shallow beds when applied at the rate 

 of 1 to 1£ gallons (or more in the case of 



