100 



THE AGRICULTURAL NEWS. 



JrxE 16, 191- 



PLANT DISEASES. 



DISSEMINATION OF ANGULAR LEAF 

 SPOT OF COTTON. 



The Journal of Agricultural liesearch. Vol. A'lII, 

 pp. 4o7-7.5 contains a detailed account by Mr. \l. ('. Faiil- 

 •wetter, South Carolina Experiment Station, of studies in 

 the method.? of distribution of the bacterium producing 

 angular leaf spot. 



Artificial infections are easily secured by spreading 

 TDacterial suspensions on the upper or under sides of the 

 leaves, the familiar water-soaked spots appearing u.suall_v 

 in seven to ten days. 



The source of the first infections of the season is not 

 yet determined. Large numbers of seedlings raised indoors 

 during the winter showed no sign of the disease. In the 

 latfc spring two instances cf cotyledonary infection occurred 

 in the greenhouse. An acre field planted in April remained 

 free of natural infections until August Another field 

 planted in May developed considerable disease in the seed- 

 lings Another experiment gave forty-five diseased plants out 

 of 36,568 at the end of twenty days. From the lot of seed 

 which gave most infections (()'46 per cent.) 1,218 seedlings 

 raised in the greenhouse in August showed no instance of the 

 disease. 



In the plots under observation no definite evidence of 

 any dissemination of the disease by insects was noted. 



The most important positive information obtained in the 

 investigations came from observations made in a field in 

 which a long row cf plants was artificially infected. The 

 ensuing .spread of the disease was charted, and the results 

 point to the conclusion that the predominant factor in the dis- 

 tribution of the disease is wind-blown rain. This accords with 

 the known ability of the bacterium to produce infection on 

 healthy leaves provided a film of water is present. A 

 continuation of the studies is proposed in which closer atten- 

 tion will be given to the meteorological factors favouring the 

 spread of the disease. 



SOURCE OF THE CITRUS CANKER INFEC- 

 TION IN SOUTH AFRICA. 



In the issue of thi.s .Journal dated March 10, 1917, 

 appeared a review of Scienoe Bidlelin No. 8, of the S. A. 

 Union Department of Agriculture, on citrus canker in South 

 Africa. 



The occurrence of the disease in South Africa was 

 ?ittributed, on the strength of definite statements in that 

 liulletin, to an importation of grape-fruit trees from Florida 

 in 1905-6. 



A letter has now been received from Mr. Wilmon Newell, 

 Commissioner of the St ite Plant Board of Florida, enclosing 

 cojiies of communications on this subject, received from the 

 T'nion Secretary for Agriculture, the Chief of the Division of 

 Horticulture, and the Government Horticulturist. 



From the information thus supplied it appears that 

 although the affection was first noticed on the Florida trees, 

 which proved very susceptible, it is equally possible that the 

 disease originated from Japanese stocks imported about 

 the same time. These have proved highly resistant, but are 

 not necessarily immune — a condition which favours introduc- 

 tions by reason of the restricted lesions escaping notice. 

 That Japan and not Florida was the source of infection 

 appears to be certain from the following statement made by 

 Mr. Newell: — 



'The first introduction of citrus canker into Florida has 

 been very definitely and conclusively established as being 

 in November of 1912, and from our knowledge of the condi- 

 tions existing in Florida with reference to this disease, it is 

 impossible, in the opinion of all authorities conversant with 

 the situation here, that the disease should have been intro- 

 duced into South Africa from Florida at so early a date 

 as 1906.' 



This assignment of a definite date to the beginning of the 

 Florida infection may .set at rest in most cases the apprehen- 

 sions that have been felt with regard to the effect of past 

 introductions of nursery stock from Florida into the West 

 Indies. 



W.N. 



TRIAL OF AGRICULTURAL TRACTORS. 



A large amount of attention is being given at present in 

 England to the employment of tractors for ploughing and 

 other agricultural purposes. In a recent issue of The Field 

 (March 5, 1917) reports appear of several official trials and 

 demonstrations which seem to have been very satisfactory. 

 Iteference is made to the 'Dugout' Daimler tractor and to 

 the Bates Steel Miile tractor, both of which are illustrated 

 at work. The latter gave excellent results on old pasture 

 land near Lewes recently, while a trial with a Ford tractor 

 is described as follows: — 



'The Royal Agricultural Society, at the request of the 

 Board of Agriculture, tested two agricultural tractors last 

 week in Cheshire. The.se tractors were manufactured by 

 Mr Ford, of America, who has placed at the disposal of the 

 Government all plans and specifications of his machine, as 

 well as the services of his experts. The tractors, it is 

 understood, may be made by British firms provided they are 

 not .sold but used by the Government. 



"The following report has been submitted by the Judges: 



"At the request of the Royal Agricultural Society of 

 England we have examined two Ford tractors rated at 25 h.p. 

 at working ploughing 



' First, cross -ploughing a fallow of strong land in a dirty 

 condition and subsequently in a field of lighter land which 

 had seeded itself down into rough grass and which afforded 

 every opportunity (^f testing the motor on the level and on 

 a steep hill. 



"In the first trial a two-breast Oliver plough was used, 

 ploughing on an average 5 inches deep with !G inches width 

 of furrow, subse<|uentlj' with a three furrow (Jockahutt plough 

 at the same depth with breast pitched 10 inches. 



'In the second trial the three-furrow plough was used, 

 ploughing an aver-ige of (i inches deep. 



"In both cases the motor did its work with ease, and on 

 a measured acre the time occupied was one hour thirtj- 

 minutes, with a cmsuraption of 2 gallons of piirattin per acre. 



"These results we consider very satisfactory. 



"The ploughs were not quite suitable to the land, and 

 the tractors cons^-ijuently were working at some disadvantage. 



