16 The Bulletin. 



Spread by Commerce in Nursery Stock. — All the means thus ±ar 

 considered contribute to the spread of the San Jose Scale to a lim- 

 ited extent — not more than a few miles at most. But by the ship- 

 ment of infested trees from place to place the scale may be spread 

 over gi'eat distances. If a nursery in California or Oregon were in- 

 fested and trees were ordered by a grower in ISTorth Carolina, they 

 would be dug and shipped, with scales attached, and the infestation 

 would begin where the trees were planted. 



We have seen that the insects have a tendency to settle near the 

 buds. ISTow if a nurseryman desires to propagate a variety, it is 

 done by cutting the buds and placing them in a young tree. If the 

 tree from which the buds are taken be infested with scale, the nur- 

 seryman is likely to introduce the insect into his nursery, and then 

 send it out to his customers on the trees which they purchase. 



We can see, therefore, that although the San Jose Scale has very 

 limited natural powers of spread, it is nevertheless able to spread 

 with considerable rapidity, aided, as it is, both by accidental causes 

 and by the hand of man. 



KINDS OF PLANTS ATTACKED. 



The San Jo^e Scale is not capable of living and thriving on all 

 kinds of plants, and it is extremely important that the grower should 

 know which ones are most liable to attack. It is primarily a pest of 

 orchard frees and it is an exception, rather than the rule, to find 

 it on any other. Of the orchard fruits, peaches, plums, apples, pears, 

 and cherries seem to be worst attacked and die most readily in the 

 order named. Certain varieties, especially of pears, seem to show 

 considerable resistance, the Keiffer, Leconte, and Garber seeming to 

 be less attacked than others, though by no means exempt. 



Currants, Gooseberries, Eoses, Grapes, Osage-orange, Thornapple 

 and Japan Walnut are quite subject to the San Jose Scale, though 

 not so readily attacked as the orchard fruits. Then there comes a long 

 list of other plants upon which it is of accidental or rare occurrence, 

 such as Persimmon, Walnut, Poplar, Chestnut, Sumac, Catalpa, 

 Willow, Linden, Ash, Dog^^'ood, Elm, Maple, Spruce, Cedar, Straw- 

 berry, Raspberry, Milkweed, and even Crab-grass. But it must be 

 remembered that its occurrence on these last is unusual, and as a 

 rule they are not attacked even though they stand close to orchard 

 trees that are badly infested. 



Forest and shade trees are very seldom infested with the San Jose 

 Scale and are not appreciable factors in harboring or spreading 

 infection. Growers often make serious and ridiculous mistakes on 

 this point and give up hope because they imagine that the "scale is in 

 the woods," or they try to destroy the forests which they suspect. 



