380 



THE AGRICULTURAL NEWS. 



November 21, 1914'. 



FUNGUS NOTES, 



THE DAMPING OFF OF SEEDLINGS. 



Indications are received from time to time of trouble 

 experienced from the damping off of seedlings of limes, 

 tobacco, onions and other plants. 



In the current volume of the Ayricultural News, 

 |)p. 78-9, some information was given as to methods of soil 

 sterilization l\v means of steam and of formalin; while in 

 the same volume, p. 1.58, the author's summary was reprinted 

 from a paper l>y .lames .Johnson, of the University of Wiscon- 

 sin, in which, as a result of considerable research, the use is 

 recommended (a) of some form of heat sterilization, or (b) of 

 formalin, 1 part in 50, applied on open beds, at the rate 

 • )f 1 quarts to the .^^quare foot of soil, which are then 

 covered for forty-eight hours to keep in the fumes. 



The use of sulphuric acid, 1 oz. to 1 gallon or 

 stronger, for a similar purpose, is reported to give good 

 results in dealing with damping otf of pine seedlings, accord- 

 ing to two i)apers, by P. Spaulding, and by C. Hartley and 

 T. (.'. Merrill, in Phytopathohxiy. Vol. IV, pp. 73-92. In 

 the latter papir it is pointed out that the method is doubt- 

 fully practicable for less resistent plants nidess the acid is 

 neutralized with lime before sowing. 



What will appeal more to West Indian planters, who do 

 not as a rule have sufficient use for a steam sterilization plant, 

 and who find formalin expensive, is the outline given by 

 Spaidding of a series of outdoor tests of modifications of 

 nursery methods. Each bed in. the series was -1 feet by 

 12 feet in area, and was raised about 3 inches above the 

 paths. The soil was a very rich, sandy loam, which had been 

 used for years as a vegetable garden, and was very uniform 

 throughout the aiea occupied by the experiments. Pmus 

 seeds were used. Equal quantities of water were given 

 except where otherwise stuted. Notes of the results were 

 taken one month after germination. .\ second test gave 

 Ijractically identical results. 

 Bed. Treatment. i Result. 



1. Very heavily manured 



2. Over 6 inches of top soil re- 



placed by dredged sand 



3. Over fi inches of top soil re- 



placed by sterile claj- subsoil 



4. Watered twice as heavily as rest 

 -i. Kept as dry as possil)le* 



8. 

 9. 



10. 



11. 



Constantlv shaded 

 Check 



One foot high Ijoard sides 

 Quarter-inch of fine gravel over' Practically free, 

 soil 



Over .50 per cent. loss. 

 Germination slow and 

 poor, no damping off. 

 Practically free. 



Total loss. 



About 25 per cent, of 



loss. 

 Total loss. 



About 50 per cent. loss. 

 About 35 per cent. loss. 



tibility to reinfection, dependent on its organic content. 

 In circumstances where treatment of the whole bed Ls 

 considered impracticable, it might still be feasible to use 

 sufficient sterilized soil to test the effect of covering the l>ed.s 

 to the depth required l>y the seedlings in their susceptible 

 stages. Where fuel is plentiful, soil for this purpose may be 

 prepared by the old-fashioned .system of roasting, either by- 

 lighting a fire on the' surface of the bed, or by heating the 

 soil on an iron plate or some such receptable over a fire. It 

 is not sufficient merely to warm the soil; it must be thorough- 

 ly heated and kept hot for some time. At the same time 

 care must be taken not to let it get so dry as seriously to 

 impair its fertility by charring the contained organic matter. 

 Number 9 is a modification of the common practice 

 of covering the seed bed with sand, and is well worth trial 

 where the material is obtainal)le. 



Watered through tiles 6 inches 



below surface 

 Check 



The results illustrate 



Over 75 per cent. loss. 



About 35 per cent. loss, 

 clearly the well-known influence 

 • xerted by excessive watering, shade, and the pre.sence of 

 '.rganic matter in the soil, and No, 3 is especially interesting 

 lis .showing the effects to be obtained from the use of subsoil,, 

 sterile by reason of its situation, and presumably less liable to 

 iid'ection when in use, owing to its comparative freedom from 

 iiganic matter, A test of the effect of artificially sterilized 

 -■•il used in a similar manner is not included in the series: 

 -uch effect is likely to be determined by its degree of suscep- 



* Tlu- lo: 



occim-ffl inuuediately after a series of daily 



SPRAYING OF GROUND NUTS FOR 

 LEAF RUST. 



ill. \V. Robson, Curator of the Botanic .Station, ilont- 

 serrat, has recently reported the results obtained this year 

 from the spraying of ground nuts with Bordeaux mixture 

 for the control of the prevalent rust fungus, Uredo arachidis. 



Previous experiments, recorded in the Reports of the 

 Botanic Station, Montseri-at, for 1910-11 and 1911-12 were 

 inconclu.sive. 



On the present occasion, a plot of the Gambia variety was 

 equally divided, and one-half was sprayed twice, using a force 

 pump with 80 tti. pressure, and a Mistry .Junior nozzle. 



At reaping tinie the pustules of the fungus were abun- 

 dant as usual on the unsprayed portion, while on the sprayed 

 plants they were difficult to find. The nuts were carefully 

 picked and weighed, and the results obtained are given as 

 foUow's: — 



As rea|)ed. Dried nuts. Per acre. 



Spraved 296 lb. 148 ». 1,779 ft, 



Unsprayed 208 „ 104 „ 1,248 „ 



The yield of the sprayed plot was thus 531 ft, or 42 per 

 cent, more than that of the unsprayed plot. 



There was no striking difference in the appearance of the 

 two sections at reaping time, i.e, there was not a browning 

 or wilting of the" foliage as had been noticed on a previous 

 occasion, but the growth of weeds had been much more 

 vigorous on the unsprayed portion, and the inference is that 

 this was due to the extra vigour of the sprayed plot. 



The difference in the time of application of the Bordeaux 

 mixture, as compared with the 1911 experiments, was as 

 follows: in 1911 the plot was planted on May 31, and 

 sprayed on August 16, and again on September 19, i.e. 77 and 

 111" days after planting; in 1914 the plot was planted oa 

 May 5, sprayed for the first time on July 7, and agaia 

 on .July 21, i e. 63 and 77 days after planting. 



That this difference in the time of application has led to 

 the improvement in the results obtained by spraying, obviously 

 needs confirmation; l;>ut whatever the reason, Mr, Rob.son 

 considers that this year the application has had decided 

 results. 



The degree of infestation of the plants by this fungus 

 depends largely on conditions of soil and climate. Whea 

 the conditions are favourable to the host, only the leaves 

 which are approaching .senility are infested; in other circum- 

 stances the fungus can be so severe as to kill the plants 

 outright. The improvement to be e.xpected from spraying 

 must therefore vary considerably from one place to another,, 

 and from year to year. 



