f)« 



SCIK.NTIFIC AGRICULTURK 



Xcivember. 1921 



tissues known as the p^iloeiu. lu the 

 phloem it gives rise to a necrosis or death 

 of the tissue. Since it is in the phloem 

 that most of the conduetiou of elaborated 

 food takes place, those parts awaiting sup- 

 plies of food for their development will 

 receive only a much reduced amount. This 

 is the case wit^ the tubers and the stolons 

 bearing the tubers. Hence those tubers 

 which do develop are small and are borne 

 on short underground stems. Moreover 

 the infective principle passes down the 

 parts of the phloem not killed and reaches 

 tlie vascular tissues of the developing tu- 

 ber. In it, therefore, there may also be 

 phloem-necrosis, \\7neu such a tuber is 

 cut across, or ■when it is pared to expose 

 the vascular tissues, these are seen to be 

 browned. The general tenii " nei-necrosis'' 

 is used to indicate such an appearance, 

 but it must be recollected that net-necrosis 

 may be caused by other conditions than 

 those in leaf-roll. Moreover the tubers 

 from a plant with leaf-roll do not neces- 

 sarily develop net -necrosis, for they may 

 not be affected soon enough, nor suffi- 

 ciently severely, to cause necrosis in the 

 vaKcular tissues. A further effect on the 

 plant is exhibited in the next generation 

 for tubers from diseased plants, and es- 

 pecially those with net-necrosis, frequently 

 develop very weak, spindling sprouts. 



The yield from leaf-roll plants is mater- 

 ially reduced, in manv cases being nothing 

 at all. 



Infection. 



The tubers transmit the disease as in the 

 case of mosaic, but an additional fact must 

 be mentioned, namely, that in the progeny 

 of plants with leaf-roll there is a much more 

 rapid depreciation in yield and accentua- 

 tion of the disease than is the ease with 

 mosaic. 



Tests conducted in Maine show tjiat 

 aphids again are the only insects of im- 

 portance in transmitting leaf-roll. The 

 seed-cutting knife is not a factor in the 

 spread of the disease. 



Varietal susceptibility : 



Red varieties are usually more su.scep- 

 tible than white varieties. Garnet Chili. 

 Davies Wari-ioi-. Irish Cobblei-. Early Pur- 

 ilMii. Early Six Weeks, Dakota Red and 

 .Ml- In tyre develop the disea.se more .severely 

 than ("arman. Oreen Mountain, and Em- 

 pire State. Tlie last named at times ap- 



l)ears to be free and at others is severel\ 

 affected, due in all probability to lack of 

 inoenlation by aphids. 



Control 

 The same points mentioned for the con- 

 trol of mosaic applv to tjie control of 

 leaf-roll. 



SPREAD OF THE EUROPEAN CORN' 

 BORER. 



The investigational w<u-k in connection 

 with the European C(»rn Borer outbreak 

 has led to the discovery of a considerably 

 increased number of host plants of this 

 l)est which now amcunt to approximately 

 forty, including a.sters. dahlias, peas, beans, 

 celei-y, etc. On August 24, the Hon. S. F. 

 Tolmie visited the outbi-eak and was great- 

 ly impressed w-ith the .seriousness of the 

 pest. On account of the unanticipated 

 spread of the European Corn Borer, an in- 

 crease was made in the number of scout- 

 ing crews and the work re-organized. Up 

 to Augu.st 27, 53 townships had been scout- 

 •ed. 36 of which were found infested, and 

 17 uninfested. As 36 townships were found 

 infested in 1920, this brings the total up to 

 72. In an endeavour to maintain the quar- 

 antine, fall fairs are being clo.sely watc-hed, 

 as well as the main higjiways leading oui 

 of the infested area. ]\Iany shipments of 

 flowers and vegetables consigned to points 

 in the United States have also been in- 

 spected. Supplements Nos. 1 and 2 to 

 quarantine No. 2 (domestic) were signed 

 on August 26 and September 6 respec- 

 tively. These supplements quarantiii;' 

 townships found infested by the corn borer 

 this season. :\Ir. H. G. Crawford of Ot- 

 tawa, and ^Ir. J. G. Spencer of Guelph 

 have prepared a Crop Protection Leaflet 

 dealing with the control of the Corn Bor- 

 er, copies of whicji may be obtained from 

 the Publications Branch. Dep. of Agri- 

 culture. Ottawa. 



MAKING THE PRAIRIES HOMELIKE 



About five million trees per year are 

 sent out free by the Dominion Government 

 Forest Nursery Station at Indian Head. 

 Saskatchewan, to farmers t(» plant shelter- 

 belts about their farms and buildings. The 

 farmers pay th(> express cliarges on the 

 trees and agree !<> cultivate the ground 

 before and after setting out the plantation. 



