10 The Bulletin. 



Spread hy Wind. — N'otice that we have said that the young insects are 

 very, very small ; therefore, if a wind blows through the orchard during 

 the breeding season (from April to December) the young crawling in- 

 sects are liable to be blown about from place to place like particles of 

 dust. Indeed, in almost every case where a large orchard becomes in- 

 fested it is to be noted that it spreads most rapidly in the direction of 

 the prevailing winds. Of course it is mere chance whether the young 

 insects which are thus blown from one tree will find lodgment on an- 

 other, and these winds no doubt leave many thousands to die on the 

 ground. But it is perfectly evident that many are spread from tree to 

 tree by this means. 



Spread hy Birds. — If a bird alights in a scale-infested tree at any time 

 during the breeding season some of the young insects may crawl upon its 

 feet or feathers and be carried off into other trees, there to crawl off 

 again. There can be no doubt that they are often established on new 

 trees in this way. We have frequently found in our inspections that the 

 portion of a tree close around an old bird's nest may be thickly infested, 

 while other parts may be slightly infested or almost entirely free from 

 the insect. In towns and villages we have found similar evidence, the 

 lower branches, next to the street or walk, being most frequently in- 

 fested, thus indicating that the English Sparrow plays an important 

 part in its spread in such places. 



Spread by Insects. — Insects play a part in the spread of this pest 

 similar to that of the birds. Especially during the blossoming season, 

 many insects are busy going from tree to tree and are thus liable to 

 spread the young scale insects. 



Spread hy Commerce in Nursery Stock. — All the means thus far con- 

 sidered contribute to the spread of the San Jose Scale to a limited ex- 

 tent — not more than a few miles at most. But by the shipment of in- 

 fested trees from place to place the scale may be spread over great 

 distances. If a nursery in California or Oregon were infested and trees 

 were ordered by a grower in J^orth 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. 

 Now if a nurseryman desires to propagate a variety, it is done by cut- 

 ting the buds and placing them in a young tree. If the tree from which 

 the buds are taken be infested with scale, the nurseryman is likely to 

 introduce the insect into his nursery, and then send it out to his cus- 

 tomers 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. 



What Kinds of Plants May be Infested?— The San Jose Scale is 



not capable of living and thriving on all kinds of plants, and it is ex- 

 tremely important that the grower should know which ones are most 

 liable to attack. It is primarily a pest of orchard trees and it is an ex- 

 ception, rather than the rule, to find it on any other. Of the orchard 



