December, 1912. 



THE CANADIAN HORTICULTURIST 



279 



Iivvcstigatiofv Work on Little Peach and Yellows 



Prof. L. Caesar, Provincial Entomologist, Guelph, Ont. 



AS MOST of the peach growers pro- 

 bably know, I spent almost all this 

 summer in the Niagara district in 

 order that I might have a better oppor- 

 tunity to study Little Peach and Yellows 

 and carry on investigation work on these 

 diseases. As many growers no doubt 

 would like to hear what line these inves- 

 tigations took and what results have 

 been obtained, I have prepared the fol- 

 lowing account of my work. 



In studying diseases one naturally tries 

 to discover the cause, but I have not at- 

 tempted to do so, because I know that if 

 one were to endeavor to find this in the 

 case of either Little Peach or Yellows, it 

 would almost certainly mean years of 

 the most careful laboratory and field 

 work, with the probability of ultimate 

 failure ; for many good students of plant 

 diseases have endeavored to find the 

 cause of Peach Yellows and failed. More- 

 over, I learned in the autumn of 191 1 

 that Dr. Duggar, formerly -oi Cornell 

 University, but now of the Botanical 

 Gardens, St. Louis, was working on 

 these diseases and thought he had at last 

 found a clue that might lead to the dis- 

 covery of the cause. (For the sake of 

 those who think that a powerful micro- 

 scope would reveal the presence of some 

 very minute causal organism I may state 

 here that no microscope shows any or- 

 ganism to be present nor can any or- 



•A paper read at the recent anmial conveation 

 of tih© Ontario Fruit Growers' Association. 



ganism as yet he gotten to grow in any 

 culture. So that, whatever the cause is, 

 it is very different from that which pro- 

 duces Pear Blight or any of our other 

 common diseases.) Feeling, therefore, 

 that the study of the cause should be 

 left to others better qualified for the 

 work, I have devoted my whole attention 

 to discovering if possible in what way or 

 ways the diseases are spread and at what 

 time or times of the year this takes 

 place, and also how long a period may 

 elapse from the inoculation of a tree un- 

 til it shows clear symptoms of disease. 

 If we get definite knowledge on these 

 points we can then hope to simplify and 

 improve our methods of control whether 

 the cause is discovered or not, though we 

 sincerely hope it will be. 



In determining how the diseases are 

 spread I have thought of the following: 

 First, pits from diseased trees; second, 

 buds from diseased trees; third, bees 

 carrying pollen or nectar from diseased 

 to healthy blossoms ; fourth, rubbing or 

 injuring healthy trees with diseased ones 

 when removing the latter from the or- 

 chard or in any other way; and fifth, 

 pruning tools used on diseased and then 

 on healthy trees. Experiments have been 

 planned, and carried out to test all of 

 these possible methods of spreading 

 Yellows and Little Peach. 



In the autumn of 191 1, with the as- 

 sistance of Mr. Nelson, of Fonthill, and 

 Mr. Harkness, of the Experimental Sta- 



Northumberland and Durham'* First Prize Half Car-load of Fruit at the Ontario Horticultural Exhibition 



This half car load was the finest exhibit of fruit ever shown in Eastern Canada. It consisted 



entirely of Spies. There wero three hundred boxes. Each box contained exactly, one 



hundred applee, twenty to a layer. 



tion, six hundred and thirty-one pits 

 from 'diseased trees were gathered. Mr. 

 Harkness planted three hundred and 

 thirty-one of these at the Experimental 

 Farm ; eight germinated and grew. I 

 planted one hundred at Guelph ; seven 

 germinated and grew, thus making a 

 total of twenty-one diseased pits in all 

 that grew, or about three and one-third 

 per cent. Of the healthy, pits used as. 

 checks, Mr. Harkness got twenty and 

 one-half per cent., Mr. Nelson forty-five! 

 and one-half per cent., and I got sixty-; 

 eight per cent, to grow. The seedlings^ 

 from the diseased pits, though not quite 

 so vigorous on the average as those from 

 healthy ones, show no sign yet of disease 

 but will be kept for several years to see 

 whether it develops. 



OTHEE TESTS 



Believing that a further test of pits 

 should be made, I have, with the aid of 

 Mr. W. E. Biggar, the Provincial In- 

 spector, and Mr. Spencer, of the On- 

 tario Agricultural College, Guelph, ga- 

 thered a few more than two thousand 

 five hundred pits this fall from trees se- 

 lected by myself in each case. A few of 

 these trees showed symptoms of disease 

 very distinctly, most of them only mod- 

 erately so, and one tree from which four 

 hundred pits were taken would have 

 escaped the notice of nine out of ten in- 

 spectors. The pits were gathered in 

 October and to make sure that there 

 could be no mistake, the fruit in every 

 case was collected directly from the trees. 

 The four hundred pits mentioned above 

 are being kept separate to see if any 

 larger percentage of them will grow than 

 of those gathered from trees showing 

 the symptoms fairly clearly. 

 BUDS 



Several experimenters have proved 

 that Yellows and Little Peach can be 

 spread by using buds from diseased 

 trees, but I thought that we should test 

 tliis our.selves and see not only how long 

 it would be before the seedlings or trees 

 thus budded would develop the symp- 

 toms, but also what variation there 

 would be in the length of this time. Ac- 

 cordingly, healthy trees, four years old, 

 in a young orchard on the Experimental 

 Farm were budded. The buds in each 

 case were taken from healthy looking 

 .shoots on diseased trees about half of 

 them from Yellows and half of them from 

 Little Peach. Each tree had at least 

 four buds inserted into it, all of which 

 took. Each budded branch has l>een 

 tagged so that track can be kept of it. 

 In addition, one hundred seedlings from 

 healthy pits were budded in a similar 

 manner, so that we might be able to 

 compare the result on thc.se with thai 

 on the older trees. Nearly all of the 

 buds on these seedlings also took. The 

 budding was for the most part done by 

 Mr. J. W. Smith's best budder, whcse 



