DISEASES OF PLANTS. 241 



Marked differences in susceptibility between different varieties of olive to 

 olive knot are reported. The nature of tlie disease has been quite thoroughly- 

 determined, and it has been found tliat the best method of prevention and control 

 is to cut out knots at the first appearance in the orchard, so as to prevent the 

 disease attacking the whole orchard. 



A study of the oak fungus {Armillaria sp.) has shown that it is a very 

 destructive plant disease which may be controlled, under some conditions, by 

 trenching, and under other conditions the fungus may be destroyed by means of 

 carbon bisulphid. It is stated that citrus, prune, peach, apricot, and almond 

 trees are attacked by this fungus, while pears, black walnuts, and figs are 

 inuuune to it. 



Some notes are given on the curly top disease of sugar beets, in which the 

 possible relationship to an organism transmitted by insects is pointed out. 



Attention is called to fruit stains, spots, and rots caused by the wither-tip 

 fungus {Collet otrichum glceosporioides) , and it is stated that the oil from 

 lemons and oranges is toxic to the fruit rind when present in very small 

 amounts, if the surrounding atmosphere is moist. Oil spot injury is said to be 

 identical in appearance with the so-called green spot. 



Report on economic mycolog'y, E. S. Salmon et ai.. {Jour. Southeast. Agr. 

 Col. Wye, No. 22 {1913), pp. 3S7-496, pis. 19, figs. 11).— A report is given on the 

 special investigations noted below, or previously (E. S. R., 32, pp. 148, 547) 

 from other sources. 



Besides a list of diseases most frequently sent in for examination and report, 

 more particular mention is made of the silver leaf fungus {Stereum pur- 

 pureum), a mild outbreak of corky scab {Spongospora solani), isolated out- 

 breaks of wart disease {Chrysophlyctis endobiotica), crown gall of alfalfa 

 {Urophlgctis alfalfce), and the bi'own rot fungus {Sclerotinia fructigena) 

 attacking frequently and severely cherries, plums, and apples. 



The American gooseberry mildew is reported upon as extending its acreage 

 considerably during the last few years. Pruning of diseased bushes is being 

 evaded, in spite of penalties, by many growers on account of the view that the 

 practice is unprofitable and disastrous to the bushes. Spraying experiments 

 against the mildew (E. S. R., 29, p. 249) have been followed up by biological 

 studies, which are reported, and by comparative tests at three centers, lime 

 sulphur and liver of sulphur being used. The former preparation gave decid- 

 edly the better results as a fungicide, and it proved also to be remarkably 

 adherent when once dry, even under exposure to heavy rains. Studies in the 

 life history of the fungus show that berries cari-ying the winter stage may 

 infect the soil under the bushes and spread the disease the following year. 

 Early pruning is regarded as of primary importance and spraying at certain 

 times as a valuable adjunct. Varieties are listed as suited to different strengths 

 of lime sulphur to be employed, and desirable conditions and management 

 recommended are outlined. 



Annual report of division of botany, 1913—14, I. B. P. Evans {Union So. 

 Africa Dept. Agr. Rpt. 1913-14, pp. 14^-158). — This includes investigations on 

 forage crops, poisonous plants, and noxious weeds, as well as on various plant 

 diseases. 



The most important plant diseases noted during the year are said to have 

 been club root of cabbage and cauliflower {Plasmodiophora hrassicce), stem rot 

 of cabbage {Phoma brassicw), and a disease of loganberry, {Hendersonia rubi). 



The reports of van der Byl on th^ mottling disease of Acacia mollissima have 

 already been noted (E. S. R., 33, pp. 151, 523). 



A report on coconut palm troubles in Portugese East Africa includes a leaf 

 spot {Pestalozzia palmarum), bud rot {Bacillus coli), two fungus diseases of 



