SAFETY FIRST IX TREE PLANTING 



667 



is certain to malvc trouble if it once enters the region of 

 the western tive-needled pine. It constitutes an additional 

 reason for fearing the movement of parasites from East 

 to W'est. The forester should profit by the costly lessons 

 of the fruit grower, and take advantage of natural bar- 

 riers to hold the forest parasites we now 

 ha\e til the regions they now occupy. 



\\'iiAT Can Be Done Auolt It? 



Only a part of the pests we should fear 

 have been mentioned in this article. The 

 list of dangerous insects is particularly in- 

 complete, as the writers make no pretense 

 of entomological knowledge. IJut enough 

 has been said to make it very evident that 

 importation of additional foreign diseases, 

 and the man-aided spread across the conti- 

 nent of parasites now limited to certain re- 

 gions of our own country, is a serious 

 menace to the future of American forestry. 

 How then can we decrease this menace? 



It is always possible for insects or fun- 

 gus spores to be carried from one point 

 to another on any commodity. However, 

 plant parasites seldom invade new regions 

 unless carried on or in some part of the 

 plant they attack. With agricultural plants 

 any part of the plant is likely to harbor a 

 parasite, and exclusion of pests is there- 

 fore very difficult. With forest and orna- 

 mental trees the problem is easier. Ver\- 



method of long-distance transfer of tree parasites is on 

 nursery stock, and in the materials in which that stock 

 is packed. 



The early attempt to pre\ent transmission of disease 

 in nursery stock shipments was by inspection. Much dis- 



THE DEADLY CITRUS CANKER 



Burning a diseased grapefruit tree with a crude oil blow-torch — the only method 

 the disease can be killed without handling the diseased parts and spreading the 



few serious diseases of trees are carried in seed. Timber 

 still bearing bark is capable of harboring many pests, 

 but is not often shipped from one forest region to an- 

 other except in the case of railroad ties and telegraph 

 and telephone poles. This is a very efficient method of 

 spreading the chestnut blight however. The principal 



Fro7n U. S. D. A. Bulletin JOO. 



KEEP THIS OUT OF THE EAST 



The Pacific Coast yellow pine mistletoe, a very harmful western parasite, known to be capable of 

 attacking eastern and European pines. Its seed may be carried on nursery stock from the West. 

 Shipment of western stock to the East is therefore dangerous. 



eased material has been kept out in this way, and 

 great good has been done. But every one conver- 

 sant with the situation realizes that inspection is 

 only a partial safeguard. Blister rust and mistle- 

 toe may not show any conspicuous evidence of 

 their presence on trees till two years or even 

 more after infection takes place, so that stock 

 carrying these parasites is very likely to pass as 

 healthy. The most dangerous organisms, those 

 which have not been serious pests in their native 

 habitats, are still less likely to be caught by in- 

 spectors. Even so conspicuous and well known a 

 disease as the chestnut bark disease can easily get 

 past an inspector, as has already been too often 

 proved. In the effort to meet this failing, the 

 authorities have established quarantines against 

 importations of certain plants. This improves 

 the situation somewhat, but is also only a very 

 partial safeguard. Following the .\merican prin- 

 ciple of allowing the maximum liberty of action, 

 quarantines have been established only w'here the 

 danger was positively known to be great and immediate. 

 ]\Iost of the quarantines have not been instituted until 

 the parasite concerned had already become established 

 somewhat in the country. 



It is therefore evident that present inspection and quar- 

 antine measures are inadequate. They do not by any means 



by which 



infection. 



