REPORT OF THE BOTANIST 247 



SESSIONAL PAPER No. 16 



In an orchard wbere good cultivation and the general clearing up uf refuse are 

 practised and the proper sprayings for apple scab given, the disease is not likely to be 

 troublesome. Hardiness of the variety is important, since, apparently, the fungus 

 can only gain entrance to the woody parts as a result of some injury such as that done 

 by frost, sun scald, etc. 



Where the cankers are already in evidence, they should be cut out with a draw- 

 knife or other instrument. Tn doing this, care must be taken to cut well beyond the 

 limits of apparent disease as shown by discolouration. The cut surface should then 

 be treated with some good disinfectant like bichloride of mercury (Corrosive subli- 

 mate), one part in one thousand of water and painted over with coal-tar or with paint 

 free from turpentine. In spraying, attention should be given to the covering of tbe 

 limbs and trunks with the spray mixture. Rotting apples should be gathered up and 

 destroyed. 



N.B. — While corrosive sublimate is in many respects the most powerful and 

 satisfactory disinfectant in such cases, too great caution cannot be exercised in ita 

 use on account of its intensely poisonous nature. Furthermore, it is strongly cor- 

 rosive to iron and the solution should always be made up and kept in wood or glass 

 vessels. A convenient form is the tablet, obtainable at most chemists, containing 

 such an amount that one tablet to a pint of water gives a solution of one to one 

 thousand strength. 



bitter rot op apples (Glomerella Rufomaculwis, [Berk.] Spauld. & Von Sch.) 



This is one of the most serious enemies of the apple crop in many of the apple- 

 growing regions of the United States. In this country, it may be looked for in the 

 warmer districts, but it is probable that many reported cases, particularly of canker 

 injury, have been really due to the Black Bot. 



The disease causes two well-marked and distinct effects, a canker on the twigs 

 and young branches and a rotting of the fruit. In contrast to Black Rot, however, 

 it is the disease on the fruit which is most destructive. A small, brown spot is first 

 noticed, which rapidly extends under favourable conditions, the tissues becoming soft 

 and wet. Later, the surface sinks, becomes shrivelled and wrinkled, and the dead 

 tissues finally becomte dry and corky in texture. As the disease progresses, numbers 

 of spore-pustules appear on the surface of the affected area, beginning to show near 

 the centre and following the spread of the disease. These are filled with pink spores. 



While the disease may attack the fruit at almost any stage if the climatic con- 

 ditions are favourable, it is chiefly noticed as the fruit approaches maturity, and hence 

 the term Bipe Rot is also given to it. Hot, wet weather is particularly suitable for 

 the rapid spread of the fungus. Fruit in an advanced stage of the rot generally falls 

 to the ground, while the less badly attacked apples may be found still on the tree. 



Control. 



It is important to prune out and destroy all cankered branches, since on these 

 cankers are produced the crop of spore pustules of the parasite. Spores from these 

 infect other twigs and give rise to a second crop which serves as a starting point of 

 the fruit infection. Destruction of attacked fruit is also important. In addition, 

 spraying with Bordeaux mixture or other fungicide is necessary. Tbe first spraying 

 should be given about forty days after the petals have fallen and be followed by three 

 more at intervals of about two weeks. The number of sprayings, however, and tbe 

 intervals between them will depend upon the prevailing weather conditions. 



