With few exceptions, you pay your money and take your chances 

 in regard to infection with viruses when you purcliase tree stocks. 

 Progress is being made when nurseries start from original clean 

 source materials, but it will take several years until large numbers 

 are built up, particularly with patented varieties. In addition, 

 grower reluctance to pay premiums for certified virus-free trees 

 delays the cleanup of U.S. material. This is due to the extra time 

 and effort it takes to certify and maintain a virus-free program 

 by the fruit tree industry. 



Until the purchaser demands and is willing to pay for trees 

 certified and indexed as to trueness to name and~Freedom from virus, 

 he has only the reputation of the seller and nursery to fall back 

 on. 



Problems with stock-scion incompatibilities like the presently 

 looming brown-line-decline syndrome with some East Mailing types 

 are suspected to be pathogenic in nature and may be the result of 

 a combination of viral or mycoplasmal pathogens. 



The relationship of stock-scion in regard to known clean 

 materials is particularly important. It is not good to use virus- 

 clean materials in one of the components while the virus content 

 of the other is unknown. One may contain a latent or "hidden" 

 virus that may damage the other clean component. This was well 

 pointed out in the decline of Virginia Crab resulting in stem-pit- 

 ting of the latter hardy stock material. Both parts of a two part 

 tree must receive a clean bill of health to receive potential bene- 

 fits of either of the components. In addition, as pointed out by 

 van Oosten, the use of virus-free bud sources is only one of the 

 ingredients of a healthy industry. Equally important is the care- 

 ful attention shown to non-viral aspects of tree selections. Fac- 

 tors such as fruit finish, trueness to name, stability of the germ- 

 plasm and a history of the susceptibility of the selection to known 

 apple virus infections are other important and desirable facts. 

 Given this information, the grower has a better guarantee of what 

 the potential of his purchased trees will be in his future orchards. 

 In today's competitive markets, with increasing production costs, 

 all factors that can be ascertained should be made available to 

 the orchardist especially in regard to purchasing his basic ingred- 

 ient, his trees. 



Tests at the Maine Station have demonstrated that considerable 

 differences in regard to fruit finishing characteristics occur in 

 selections of Golden Delicious even though they are free from virus 

 infection. Some virus-free selections produce badly russeted fruit 

 year after year compared to others which develop good fruit finish 

 when growing side by side in the same orchard and receiving identi- 

 cal production practices. (Table 1) 



