MARCH 29, 1900. 



The Weekly Florists' Review. 



509 



eating the same. It goe.s without say- 

 ing that ordinai-y sprays will !)(> of 

 little curative effect upon a i)lant 

 when the living vegotine threads of 

 its fungus parasite penelratrs to all 

 parts. 



In California the reader has seen 

 the rust upon roses much worse than 

 here — when every leaf upon some 

 shruhs was badly affected. In such a 

 warm climate, wlien the plants retain 

 their foliage thi'oughoul the year, the 

 dark winter spores, not being needed, 

 are omitted, and the orange colored 

 form of summer is perennial. There 

 are many of the rusts in the warmer 

 parts of the earth that grow continu- 

 ously, while the same kinds of plants 

 with us are exempt, presumaldy due 

 to the uncongenial nature of our cli- 

 mate. In passing it may be said that 

 the chrysanthemum rust produces 

 only the summer form in the green- 

 house, and the hardy out-of-door 

 sorts seem to be exempt from the dis- 

 ease. 



The Rose Anthrachose. 



(Gloeospnriuni rosae Hals.) 



The chief feature of this disease is 

 the scarcity of leaves. Instead of a 

 plant with foliage upon all the canes, 

 there are but few leaves upon some 

 stems, while others are entirely de- 

 foliated. The whole plant is infested 

 with the fungus, and this parasite 

 so saps the vitality and interferes 

 with the processes of growth that the 

 leaves, even if they were healthy in 

 themselves, are unable to perform 

 their work. The fact is that the leaves 

 are infested with the anthracnose fila- 

 ments, and soon after falling, if not 

 before, they will show the spore for- 

 mation of the anthracnose fungus, 

 Gloeosporium rosae Hals. In general 

 appearance and habits of growth this 

 fungus is quite similar to the one 

 causing the anthracnose of the rasp- 

 berry, named Gloeosporium venetum; 

 possibly it is identical and if so the 

 presence of the one is a menace to 

 the host of the other. 



The rose plant is most likely at- 

 tacked while young, or at least it is 

 to be presumed that the young por- 

 tions of a plant are most susceptible. 

 The attack is from without, and the 

 spores tailing upon the surface of the 

 young, tender canes, and leaves as 

 well, there germinate and produce, in 

 a short time, an affected spot. If this 

 takes place in a cane, it is natural to 

 suppose that the portion above the 

 infested part will be girdled, in so far 

 as the attack is great, and this will 

 interfere with the direct support by 

 the whole plant of the part beyond the 

 diseased place. Besides this, the fun- 

 gus spreads, and more rapidly, in the 

 direction toward the tip of the cane. 

 It is not unusual for a diseased plant 

 to send up apparently healthy shoots 

 from near the base of the stem, these 

 in turn to become infested. 



Roses that have a sickly color to 

 the foliage, with the leaves falling 

 prematurely, especially from the tips 



of the canes, may be suspected as vic- 

 tims of the*" anthracnose. A hand lens 

 should be sufficient to assist in 

 finding pinkish blotches upon tin- 

 leaves, particularly those that lie upon 

 the moist earth beneath the haU'-di>- 

 folialcd iilant. Similar but better de- 

 lined pimples usually occur upon some 

 portion of the cane. 



It will be gathered from these re- 

 marks that rose anthracnose is a spe- 

 cific disease, caused by a well defined 

 fungus that grows rapidly from spores, 

 penetrates the substance of stem and 

 leaf, and finally causes defoliation and 

 death of cane. The anthracnose, lie- 

 cause of its multitude ot spores pro- 

 duced in pimples on leaves, particu- 

 larly fallen ones, and the canes, and 

 the ease with which they are trans- 

 ported by water, also rapidity of ger- 

 mination, all combine to make this 

 fungous enemy of the roses very con- 

 tagious. 



This class of fungi in which the 

 Gloeosporium belongs is amenable to 

 treatment by fungicides. A coating of 

 the Bordeaux mixture or cupram upon 

 the leaves and stems prevents in large 

 degree the entrance of the germs. 

 Therefore all rose-houses where there 

 is any anthracnose should be sprayed 

 with one of the above compounds. It 

 goes without further saying that all 

 plants that are nearly leafless from 

 this cause should be either cut down 

 ■(' to the soil or thrown bodily into 

 the burn-heap. 



The Rose Leaf Spo'. 

 (Cercospora rosaeicola Pass.) 



Somewhat similar to the leaf blight 

 previously mentioned is the leaf spot 

 due to the fungus Cercospora rosaei- 

 cola Pass. This produces spots that 

 are of a gray color with a dark pur- 



■ border and the spores are long and 

 borne in little tufts upon the surface 

 of the central portion of the dead 

 areas. In microscopic structure the 

 leaf spot and the leaf blight are very 

 different, the former having the spores 

 upon the tips of threads which pre- 

 viously have grown through the sto- 

 mates. The leaf blight has the spores 

 borne internally in small pits and are 

 poured out in a viscid coil when the 

 part is moistened. 



These facts are given to show that 

 while to the naked eye the differ- 

 ences between the two herein named 

 fungi are not apparent, under the 

 microscope they are widely unlike and 

 the treatment that will work admir- 

 ably for one may not answer for the 

 other. 



As yet this leaf spot is not com- 

 mon, but when found at all is often 

 quite destructive. From the nature of 

 the fungus it is inferred that it is to 

 ''e easily controlled by fungicides. For 

 example, its cousin, Cercospora beti- 

 cola Sacc, is the common beet leaf 

 spot with which there have been many 

 experiments, and it is found very 

 amenable to treatment with the Bor- 

 deaux mixture and other standard 

 fungicides. 



Black Speck of Roses. 



( I^ilo[)ijlus cry^talinus Todf.l 



Complaints have come to the writer 

 from time to time with regard to a 

 speck upon the rose plants. This 

 trouble is due to the indirect, and not 

 the intentional, action of a fungus, 

 and in this respect is quite unusual and 

 merits a word of consideration. The 

 lungus that is the source of trouble is 

 somewhat closely related to the coarse 

 one that thrives upon bread, and is 

 very damaging to sweet potatoes in 

 the storage bin, causing the soft rot. 

 In short, it is one of the molds and 

 grows ujjon organic substances, and 

 not, as before stated, u[)on the rose. 



The fungus in question is Pilobolus 

 crystalinus Tode, and forms in large 

 numbers upon the manure used to 

 cover the bed where roses are grow- 

 ing. As it matures, a dark oval ball 

 or sac is produced, filled with spores 

 of the pilobolus. This black sac is 

 supported upon a swollen stalk rising 

 from the surface of the manure, and 

 when mature the enlarged portion, 

 filled with liquid, suddenly forces off 

 the spore sac and collapses, throwing 

 the ball of spores into the air. These 

 dark spore sacs are covered with 

 moisture as they are discharged and 

 will adhere to any object which they 

 may strike in their flight. 



The writer has examined houses 

 where this fungus has developed ex- 

 tensively upon the manure and count- 

 ed as many as a hundred specks to the 

 square inch upon the white woodwork 

 surrounding the bed. An examination 

 of the perpendicular sash in dividing 

 walls in greenhouses will show, from 

 the numerous spore specks adhering, 

 that the height to which the dark sacs 

 are thrown is fully ten feet; but there 

 is a rapid falling off in the number 

 upon any given area when the height 

 of two or three feet is reached. 



These specks, of course, from what 

 has been written, may be upon any 

 plant that is within range, but the.v 

 do no further harm than the disfigure- 

 ment thereby produced. They are 

 more often met with in rose houses, 

 because there the manure is more fre- 

 quently left upon the surface than 

 with other kinds of plants. 



If a remedy is sought it may be 

 found in dispensing with the manure 

 on the surface, stirring it at frequent 

 intervals to prevent the fungi from 

 I ^uig time to mature their dark 

 shells containing the '-shot" in the 

 form of spores, so to speak, or by 

 using some fungicide as a spray upon 

 the manure that will kill the" mold. 

 However, as a rule the bombardment 

 does not last long and no vigorous 

 measures are generally called for in 

 this case. 



An illustrated article by the writer 

 upon this subject appeared in the 

 American Florist for April 30. 1S9S. 



Bronzing of the Rose. 



As a last trouble to be mentioned at 

 this time, attention may be called to 

 a peculiar discoloration of the leaves 



