BUREAU OF PLANT INDUSTRY. 213 



and the wild <;oosebeiTies averaged 30 bushes per acre. This area is 

 located 20 miles from a phmting of infected pines imported about 

 1900. Apparently it required six years for the disease to spread 20 

 miles from this original center of infection, and another six years be- 

 fore much increase in infection took place in the secondary center at 

 Littleton. The increase in pine infection since 1914 has been very 

 rapitl. On a rod-wide strip GV miles long run from Lisbon to 

 Woodsville and Piermont, N. H,, and from Wells River to Kyegate, 

 Vt., 9.9 per cent of the pines were found infected. Another rod-wide 

 stri}) approximately 22 miles long was run in the vicinity of Lewis 

 and Deerhead, N. Y., and showed that 10.9 per cent of the pines 

 were diseased. From this evidence it is plain that general pine infec- 

 tion is taking place quite rapidly. 



DAMACil': TO PINK. 



Pine infection starts on the needles or small twigs and works back 

 toward the trunk of the tree. It is usually three years, frequently 

 four years, before a blister-rust canker can be recognized without 

 microscopic determination. After the characteristic swelling and 

 iliscoloration of the bark appear the mycelium advances along the 

 branch to the main stem of the tree at the average rate of about 

 '^ inches a yeai". Thus, the greater the distance from the trunk at 

 which infection occurs or the larger the trunk, the longer is the time 

 required to kill the top of the tree. 



Pine seedlings ?> or 4 years old appear to be killed within four 

 years after infection. ]More time is required for the fungus to grow 

 back and girdle larger trees at a vital point on the trunk unless, as 

 quite often happens, a small branch close to the trunk becomes in- 

 fected or the disease attacks the younger portion of the main stem 

 near the tip of the tree. Judging b}' the results in numerous areas 

 of heavil}^ infec"ted native pine, trees 5 to 10 feet high when infected 

 are killed, or at least commercially destroyed, in from 5 to 10 years 

 after infection. Trees 10 to 20 feet high fre({uently have the lower 

 part of the stem girdled in 8 to 10 3'ears after infection, although 1.5 

 years frequently elapse before this occurs. Trees over 20 feet hif^h 

 may suffer seriously in 12 to 15 years, depending on whether the dis- 

 ease attacks the tips of long branches at a distance from the trunk 

 or a small branch close to the trunk, and also on the number of 

 branches infected. Occasionally trees of any size may be killed in a 

 comparatively few years by having a very large number of small 

 twigs infected over the entire crown. Thus, a tree 40 feet high was 

 found to have 200 .se[)arate twig infections on a single main branch, 

 and the entire tree was estimated to have 36,000 separate infections 

 on it. These infections took i)lace in 1914 and 191.'), and the tree is 

 now rapidly dying. Infection of this character takes place only in 

 close proximity to large and heavily infected Kibes bushes. 



RIBKS KRADICATION. 



In the New England States, New York, Minnesota, and Wiscon- 

 sin the work is aimed almost entirely toward perfecting inexpen- 

 sive and efFef"ti\e methods of destroying wild currant and gooseberry 

 bushes; to pi'acticMJ denionsti'iit i')us of these methods 011 local r-ontrf)l 



