1910] DISEASES OF PLANTS. 657 



to Senecio vulgaris or Nicotiana affinis. The disease originates in the soil, in 

 which it is thought oospores of the fungus hibernate. 



Methods of control as outlined include sterilization by steam, also amputat-- 

 ing diseased portions and treating the roniaining portion as a cutting. 



Dry-rot of turnips. — Sug'gestions regarding control, A. H. Cockayne {Jour. 

 Agr. [New Zeal], 17 (1918), No. 2, pp. 7i-7S).— Results of investigational work 

 in the field and laboratory are presented showing that infection by Phoma napo- 

 brassicce appeared sooner on early than on late sowings of various crucifers 

 and increased until September, although not much loss occurred in July. All 

 varieties of swedes so far as studied are about equally susceptible. Infected 

 soils show earlier than clean land the appearance of dry-rot, which may be 

 delayed by the application of lime. Swedes under cover keep better than those 

 in the field, though earthing up reduced infection. An outline of suggested 

 work is given with reference to reduction of loss from dry-rot. 



Orchard experimental work by Stoke Fruitgrowers' Association (Jour. 

 Agr. [Neiv Zeal.], 17 (1918), No. 4, pp. 225-230).— In this report, read by W. O. 

 Hyde, experiments are described in which lime-sulphur proved superior to 

 atomic sulphur as a general fungicide in orchards. The invigorating effect 

 of spring applications of Bordeaux mixture to apple trees was confirmed, as 

 was also its favorable action against black spot when properly followed by 

 lime-sulphur as compared with an application of lime-sulphur alone. Weak 

 copper sulphate as a summer spray for apple trees proved impracticable. An 

 application of oil following a fungicide proved uneconomical. Naphthalene 

 lime-sulphur gave promising results as a commercial fungicide and a contact 

 insecticide. Proper timing of orchard cultivation is considered important in 

 connection with fungus infection of orchard trees. It was found that lime- 

 sulphur 1 : 125 and atomic sulphur 15 lbs. to 100 gal. of water applied in summer 

 produced no scorching. Bordeaux mixture is a more effective spray for 

 peaches than is lime-sulphur. 



Treatment of apple canker diseases, J. 0. Whitten (Missouri Sta. Bui. 16S 

 (1919), p. 54)- — The author recommends for the conti'ol of apple canker the 

 pruning out of limbs that are dead or practically destroyed. The limbs should 

 be cut close and the wounds painted with common paint containing corrosive 

 sublimate. Where canker occurs in patches on the limbs or side of the tree 

 the wound should be scraped clean and painted with disinfected paint. It is 

 claimed that 80 per cent of canker infection may be avoided by reducing the 

 number of unnecessary wounds during pruning and cultivation. 



Apple powdery mildew a serious menace to orchards, D. P. Fisher (Better 

 Fruit, 13 (1919), No. 10, pp. 3-6, figs. 6). — It is stated that apple powdery mil- 

 dew (Podosphwra leucotricha) is now commonly found in all of the major 

 apple growing districts of the Pacific Northwest, causing loss in which the 

 injury to the tree extends over nfore than one season. Though the disease 

 is as yet localized, It is feared that favoring conditions may make it general 

 over this region. A discussion is given of its relations to such factors as wind, 

 precipitation, dew, and temperature. The fungus is also occasionally found 

 on pears in this section. 



At Wenatchee, Wash., it was found that, while pruning could be made a 

 valuable supplement to spraying, the latter used alone was in the end more 

 economical. Of the means employed, ammoniacal copper carbonate appears to 

 be the best single spray for all seasons, though it is thought that neutral 

 Bordeaux mixture may prove as effective and perhaps cheaper. Copper 

 sprays are regarded as a costly and makeshift supplement to sulphur sprays 

 during the period of burning sunlight when sulphur sprays are unsafe, although 



