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F»ut)lish&cl at 18 South ATiark.e-t St., San Jose^, Ceil. 



V'OH'MK XIX. NrMBKK 50. 



MAY, 1903. 



Monthly, 50 Cents a ^■EAK. 



Pests and Diseases of Deciduous Fruits 



By JoHn Isaac 



{Paper rciut al //if /■'nii/ (/roiucrs' (oiiioi/ioii. i.o.s .higc/cs 1 



You will often hear the statemeni 

 made by ptople who look regretfully 

 back to (he good old times that the 

 fruit industry i.s going to the bow- 

 wows because there are such swarms 

 of diseases and pests now to be com- 

 batted, and that, when they were boys, 

 such things were unknown. Now, the 

 fact is that, although not generally 

 known, they existed as much then as 

 they do tod.iy, but in those good old 

 times fruit growing was an incident, 

 not a busines.s, and commercial or- 

 (■hard.« were rare. Our fathers grew a 

 few trees for family use. If 

 they bore good fruit, well and 

 good; if the fruit was small 

 and scrubby, no questions were 

 asked as to the reason, and the young 

 folks still ate it with a relish and re- 

 member its good qualities today. If 

 the tree sickened and died, it couldn't 

 be helped, and no especial attention 

 was paid to it. 



Of recent years, fruit eating is be- 

 - coming more and more general. Fruit 

 has become an article of merchandise. 

 It is found on every table and in vari- 

 ous forms. In the struggle for a better 

 market, a wider demand . and larger 

 prices, every class of fruit has been 

 wiand^rfully improved, and the full 

 strength of the tree has been forced 

 into the fruit, while the tree itself, as 

 a rule, has become more and more 

 delicate, bearing at an earlier age. 

 passing its season of usefulness sooner 

 and succumbing' more readily to the 

 .ittacks of disease and insects. Then, 

 loo, in our efforts to produce superior 

 Iruits, we have paid more attention 

 10 their ailments. We have studied 

 iheir requhfments and their suffer- 

 ings rlo:;er. and are now aware of veg- 

 rtable troubles that were wholly un- 

 known or unnoticed by our ancestors. 

 So much Is this true that vegetable 

 pathology and entomology have prac- 

 tically stepped from the unknown into 

 the ranks of the sciences within the 

 pasf century. 



The reasons, then, why we have more 

 troubles to overcome in our orcliards 

 than our ancestors had are that we 

 know more about those troubles, that 

 A-e have more trees to be attacked, 

 and that our trees are more delicate. 

 There i» yet another reason. In our 

 fforts to get the best, we have scoured 

 the world over for varieties imported 

 them from all parts of the globe, and 

 with them have also imported pests 

 nnd di«':isHS (hat w.fi- hitherto un- 



knuw to us. There is no such thing, 

 it is said, as unalloyed good, and so 

 in this case, in our efforts to improve 

 our stock, we have become the agents 

 for the introduction of unnumjbered 

 ills and many pests which were orig- 

 inally confined to a limited area, but 

 which liave now become almost world- 

 wide. 



Now, the matter that bothers us is 

 how to preserve what is good for us 

 and eradicate that which is ill, and 

 it is to this end that some of the ablest 

 minds of the age have devoted their 

 lives, and we have numerous methods, 

 preventive and curative, adapted to 

 the various diseases or pests to be 

 reached. 



Tree diseases may be roughly classed 

 under two hears, fungus and bacterial. 

 Among the former we have peach curl 

 leaf, shot-hole fungus of the apricot, 

 apple scab, rose rust, mildew and many 

 other forms, with which we are all 

 too well acquainted. The cause of 

 curl leaf is a parasitic fungus, "ex- 

 cacus deformans." This disease ap . 

 pears early in the spring at the time 

 when the trees are making their most 

 vigorous growth and the tender leaves 

 offer it the most favorable conditions 

 for growth. It has its origin from two 

 sources, the perennial My<elium. which 

 remains dormant from a previuu,'; s.a- 

 son. and from the dormani spores shed 

 the preceding year, which have formed 

 lodgment on the twige and branches 

 of the tree, awaiting the favorable con- 

 ditions for growth which the spring 

 affords when they spring into active 

 life, atack the new leaves and tendei 

 growth and spread with wonderful rap- 

 idity, very soon involving the whole 

 tree. Moist conditions are favoral)Ic 

 to the growth of this fungus, hence we 

 usually find it worse in wet seasons or 

 in sections where there is much mois- 

 ture in the air. while it is lesr, viru- 

 lent in its attacks in the dryer locali- 

 ties .ind dies out as the summer ad- 

 vances. 



The history of the peach curl leaf 

 is in .1 general way the history of most 

 of the fungus diseases which attack 

 our fruit, and their treatment is large- 

 ly the same. For a winter wash, the 

 salt, sulphur and lime is the most ap- 

 proved of our known remedies. This is 

 excellent, both as a fungicide and as 

 an insecticide, and should be thor- 

 oughly applied as late in the season as 

 il is safe to use it. 



Whtn the young leaf or fruit buds 

 begin to swell it is too late to apply 

 it. After the trees are in leaf the 

 Bordeaux mixture of reduced strength. 

 2 pounds of sulphate of copper 2 

 pounds of lime and 50 gallons of wa- 

 ter, may be safely used and is recom- 

 mended. 



The second group of diseases are 

 those of bacterial origin, and here we 

 have a class that is more than usually 

 difficult to reach. I believe It is even 

 yet a mooted question whether these 

 bacteria can be classified as of animal 

 or vegetable origin, but it is certain 

 that their work is carried on beneath 

 the surface and spread through the sap 

 of the tree, and we have so far discov- 

 ered no remedy that does not damage 

 or destroy the tree. In this class we 

 find the pear blight, which has wrought 

 such destruction in our state; the olive 

 knot and kindred diseases. The dis- 

 ease, in these cases, finds entrance in 

 some tender part of the plant. In the 

 case of the pear blight, through the 

 blossoms largely, and being taken up 

 in the sap spreads through the cam- 

 bium layer and gradually involves the 

 whole tree. It is insidious in its work 

 and often passes unnoticed until the 

 greatest damage is accomplished. The 

 germs in soine of the.se diseases may 

 he carrier by the wind, but more fre- 

 (luently inseits are the principal ve- 

 hicles of their spread. In the case of 

 riear blight there is little question but 

 that our honey bees are an important 

 source of infestation, flying as they 

 do from blossom to blossom and carry- 

 ing the germ of the most susceptible 

 point of entry of the plant. At the 

 same time. I question very much the 

 advisability of shutting the bees out 

 of the orchards, as other insects and 

 wild bees, which cannot be removed, 

 are equally culpable. 



The remedy for this disease is to 

 injure the trees. When the tree is mak- 

 ing its most vigorous growth, the sap 

 is flowing freely, and it is thtn that 

 the germs spread most rapidly. As 

 the season advances the growth stops, 

 the wood hardens and the disease is 

 checked. If the trees are neglected, 

 uncared for and stunted, the disease 

 will be largely checked. The disease 

 mav be largely stopped to some ex- 

 tent if when the first evidence of it 

 are observed the diseased portion is 

 cut back well below the point of at- 

 tack. The trees should be gone over in 



