5 o8 



Garden and Forest. 



[Number 356. 



degrees, and sprinkled overhead twice a day, but after the 

 weather is warm enough they will do better in a cold frame, 

 the pots being plunged to the rim in leaves, and the plants 

 shaded lightly during the hottest part of the day. Plenty of air 

 by night and day should be given when the weather is favora- 

 ble. Watering and syringing must be carefully attended to, 

 and a sharp lookout must be kept for green fly and other 

 insects, as they would soon destroy the plants if allowed to get 

 a footing. Should they appear, the plants must be fumigated 

 or dipped in a solution of tobacco-water or other insecticide ; 

 the latter method is more troublesome, but is the more 

 effective. 



Tarrytown, N. Y. /' llluxm Scott. 



Spraying for Black-knot upon Cherries and Plums. 



IN the spring of 1893 some experiments were begun at the 

 Cornell Station to determine, the value of the Bordeaux 

 mixture in controlling the black-knot of Plums and Cherries. 

 This disease has proved fatal to so many trees, and even 

 entire orchards, that it is a continual menace to the growers of 

 these fruits. It probably has caused greater losses in New 

 York than the dreaded peach-yellows, and during some sea- 

 sons it has spread with such rapidity that all efforts for its con- 

 trol were practically useless. The disease has consequently 

 had its own way in the large majority of cases. 



All scientists now agree in ascribing the cause of black-knot 

 to a fungus ; but, although the parasite has long been known, 

 its life-history has not yet been completely worked out. It is 

 known, however, that the fungus produces large numbers of 

 spores, and these are supposed to obtain an entrance into the 

 host plant some time during the warmer months. Just how or 

 when this takes place still remains to be shown. Humphrey 

 says * that the knots first appear in the fall as "slight swell- 

 ings of the branch." I have failed to find any distinct indica- 

 tion of the knots before early spring ; yet there appears to be 

 little doubt of the fact that most, if not all, of the newly in- 

 fested parts fail to show the presence of the fungus by the for- 

 mation of new knots until the following spring or early sum- 

 mer. In other words, it now seems probable that infection 

 takes place during one season, but well-developed knots do 

 not appear until the following year. 



Several experiments were planned with the above theory as 

 a basis. The fungicide used was the Bordeaux mixture, as 

 this has become to be recognized as our most efficient com- 

 pound for the prevention of fungous diseases. The trees se- 

 lected for the work were Plums and Cherries, but only one 

 case, that of some Cherry-trees, will be here mentioned. The 

 trees were mostly sprouts which had been allowed to grow to a 

 height of eight to ten feet. They sprang from the roots of 

 some Morello trees which were set many years ago, and at the 

 time of the beginning of the treatments the old trees and the 

 younger ones were thoroughly entangled, and they were also 

 well covered with knots. The thicket, tor so it might be called, 

 was divided into two nearly equal parts by cutting out the 

 brush on a line passing nearly through the centre. One 

 part was sprayed, but the other remained untreated. No knots 

 were cut out during the first year. 



The first application was made March 29th, 1893, and this 

 was followed by others upon the following days : April 18th, 

 May 6th and 30th and June 13th. Notes taken June 13th show 

 that new knots were forming as abundantly upon the treated 

 as upon the untreated half. No further treatments were made 

 during this year. 



The first application in 1894 was made April 9th. This was 

 repeated on the 25th of the same month, and at this time all 

 the knots were removed from the entire thicket. They ap- 

 peared to be equally abundant upon each plot, and for greater 

 accuracy in drawing conclusions, the number cut from each 

 side was counted. Additional applications were made May 

 21st, June 6th and 27th, July 10th and 20th and August 1st. 



On November 26th all the knots were again cut out and 

 counted. A comparison of the numbers of knots cut in the 

 spring of 1894 and of those cut in the fall should indicate to 

 a greater or less degree the value of the treatments. But 

 whether the treatments of 1893 are wholly or only partially in- 

 strumental in bringing about the final result cannot now be 

 stated with certainty. The results were these : 



In the spring of 1894 the number of knots cut from the 1111- 

 sprayed trees was 2,002, and from the sprayed trees 1,155. 



In the autumn of 1894 the number of knots cut from the 

 unsprayed trees was 3,466, and from the sprayed trees 165. 



These figures show an enormous gain in favor of the sprayed 

 portion. And this gain is emphasized still more if it is as- 



;i ' Eighth Annual Report Massachusetts State Agricultural Station, p. 205. 



sumed, as may justly be done, that the same ratio of increase 

 in the number of knots shown in the unsprayed plot would 

 also have taken place in the sprayed ^portion, provided no 

 treatments had been made. In this cast the 165 knots cut in 

 the fall must be compared, not with the 1,155 knots cut in the 

 spring, but with 2,000, since this is within a fraction of the 

 number assumed to have been produced, had no application 

 been made. 



It cannot be held that absolute protection has been effected 

 by the treatments, but it is not very often that such a state- 

 ment can be made, even with plant-diseases, which are now 

 regularly treated by the use of fungicides. One must also take 

 into consideration that the sprayed trees were standing so 

 near to the other portion of the row that the branches of the 

 two lots almost touched each other. In addition to this, the 

 knots had been allowed to remain on the trees until all the 

 winter spores had been disseminated and the spread of the 

 disease had been favored as much as possible. If we knew 

 more regarding the time and manner of infection we should 

 know better when and how to apply the treatment so that it 

 would be most effective. If the results of further experimen- 

 tation agree with thecase mentioned above, we may soon have 

 a definite direction for the treatment of this fungus as we now 

 possess in thecase of other plant-diseases over which we once 

 had no control, but for which we now have practical and effi- 

 cient remedies. 



Cornell University. E. G. Lodeman. 



[The practical importance of experiments on the best 

 way of preventing diseases caused by fungi is so great that 

 we invite attention to a few points in the interesting 

 account given above. The fungus producing the black- 

 knot has two well-known forms of spores — the asco- 

 spores, which mature in midwinter and are discharged in 

 early spring, disappearing usually during the month of 

 April, and the conidia, which mature in early summer. 

 With regard to the existence of other forms of spores infor- 

 mation is very scanty, but it is probable that, whatever 

 may be the other forms, they mature in the autumn, or, at 

 least, in late summer. Since the number of knots on the 

 sprayed and unsprayed trees was not counted before the 

 spraying, one cannot be certain that the numbers 2,002 

 and 1,155 do not represent the original proportion of knots 

 on the unsprayed and sprayed trees previous to the experi- 

 ments, especially in view of the statement that at the time 

 the knots were cut and counted " they appeared to be 

 equally abundant upon each plot.'' In other words, while 

 at a rough estimate they seemed equally abundant, on 

 actual count they were found to bear the proportion of 

 4 to 2.3. 



A comparison of the figures given for 1893 and 1894 is 

 interesting. On April 25th, 1894, all the knots were re- 

 moved from both the sprayed and unsprayed trees, and yet 

 on the following 26th November there were 3,466 knots on 

 the unsprayed, and only 165 on the sprayed trees. This 

 result, so very different from that of the previous year, 

 leads us to examine more closely into the method of the ex- 

 perimenting during the two years. In 1893 the trees were 

 sprayed on March 29th, April 1 8th, May 6th and 30th and 

 June 13th ; that is, they were sprayed at a time of the year 

 when the Bordeaux mixture might be supposed to destroy 

 the ascospores which were germinating and capable of 

 producing new knots. On the other hand, the conidia of 

 1893 would not be malured naturally until after the date of 

 the last spraying. 



In 1S94, however, the dates of spraying were April 9th 

 and 25th, May 21st, June 6th and 27th, July 10th and 20th 

 and August 1st. In 1894, therefore, the spraying began at 

 a date when some of the ascospores might already have 

 germinated, and was continued during the period when the 

 conidia would have matured and germinated. We might 

 then suppose, assuming the favorable result as shown by 

 the proportion of 3,466 to 165 in November, 1S94, to be due 

 to the spraying, that the conidia were decidedly more active 

 in spreading the knot than the ascospores. This involves 

 also the supposition that the knots removed in November, 

 1S94, were the result of infection by conidia during the 

 summer of 1894. In such a case the knots, judging by 

 previous experience, would have been small. On this 



