450 



Yearbook^ of Agriculture 1949 



fungus and bacterial diseases, the grow- 

 ing of limited quantities in quarantine 

 is the only practical method of han- 

 dling such introductions. Some virus 

 diseases have a number of widely differ- 

 ent hosts. Some ornamental plant, for 

 example, may be the means by which 

 a destructive forest-tree virus might 

 gain entrance. 



Diseases and insects do not respect 

 the boundaries between the United 

 States and Mexico and Canada. Fly- 

 ing beetles or migrating birds that 

 carry spores on their feet cannot be 

 inspected. So all three countries have 

 a joint interest in preventing new in- 

 sects and diseases from becoming 

 established in North America. Most 

 tropical-tree pests fortunately do not 

 thrive in our more northern climate, 

 with its different tree species, but the 

 pines in the high mountains of Guate- 

 mala, for example, may have parasites 

 that are not present here. 



A strengthening of the inspection 

 and quarantine force to handle more 

 adequately the importations coming 

 into this country is needed. The in- 

 creasing number of airplane flights and 

 the volume of commerce in veneer logs 

 and packing material pose difficult 

 problems. 



We have no method of forecasting 

 whether an introduced insect or dis- 

 ease will be more or less destructive in 

 this country than it is in its native 

 home. Foreign pests generally become 

 well established in this country before 

 their presence is discovered. Much 

 more information is needed on forest 

 diseases and insects, both in our own 

 country and abroad. Definite surveys, 

 such as those called for under the 

 Forest Pest Control Act, will build up 

 our information so that (at least when 

 a new local outbreak shows up) a de- 

 cision can be made as to whether it is 

 something new to this country. Study 

 of foreign disease reports is helpful. 

 Few of our American tree species are 

 grown in foreign countries, and ad- 

 vance information on their parasites, 

 therefore, is not available. 



The systematic planting of our im- 



portant American trees in different 

 foreign regions is needed as a basis for 

 determining the diseases and insects of 

 those areas that may be destructive to 

 our trees and need to be guarded 

 against. There are some such plantings 

 in foreign countries and these should 

 be studied. Such information is valu- 

 able in preventing potentially danger- 

 ous diseases and insects from entering 

 this country. This same information 

 would be helpful in promptly handling 

 an outbreak, if the disease or insect 

 should get a start in this country. 



Many plantings of American trees 

 can be made at forest schools and forest 

 experiment stations in foreign coun- 

 tries at no cost other than supplying 

 the seed. Some information can be 

 obtained on their diseases and insects 

 from foreign scientists, but occasional 

 inspections by American scientists will 

 be needed. As an incentive to this 

 project, arrangements might well be 

 made in this country to plant foreign 

 trees and make reports to the foreign 

 scientists on their growth, diseases, and 

 insect pests. 



As our American forests become less 

 productive on account of new disease 

 and insect attacks, we will have urgent 

 need for new species of trees for plant- 

 ing and hybridization. So these system- 

 atic plantings of the exotics in forest 

 blocks will prove a most valuable addi- 

 tion to our own forestry as well as give 

 our foreign cooperators information on 

 diseases and insect pests of their native 

 trees. 



G. F. GRAVATT, a graduate of Vir- 

 ginia Polytechnic Institute, is a forest 

 pathologist in the Bureau of Plant 

 Industry, Soils, and Agricultural Engi- 

 neering. He is the leader of the program 

 for the development and distribution 

 of blight-resistant chestnuts and has 

 studied other introduced diseases. He 

 has long recognized the danger to 

 American forests from the introduced 

 epidemic diseases and has consistently 

 advocated the necessity for stronger 

 protective measures to exclude them 

 from the United States. 



