8 



AMERICAN FORESTRY 



Photograph by A. B. Brooks. 



PULLING WILD GOOSEBERRY BUSHES WITH THE DERBY HOOK 



Large bushes like this one are well anchored and require considerable labor to uproot. The 

 work is made easier by special implements invented for the purpose. Many of the bushes are 

 smaller and less expensive to destroy. The average cost of clearing the land of wild goose- 

 berry and currant bushes was 35 cents per acre in 1920. This low cost was obtained by 

 employing scientific methods in locating wild currant and gooseberry bushes. Costs are 

 expected to be still further reduced in areas where wild bushes are very numerous, as a 

 result of successful experiments in destroying such bushes by spraying them with chemicals. 



over an area. In the summer and fall of 1920, Dr. Pick- 

 ler and Mr. Hodgkins conducted a survey to determine the 

 effect of control work done at Lenox four years before. 

 They made a similar survey in an area from which the 

 currant and gooseberry bushes have never been removed. 

 This area is located in the Berkshire region, at New 

 Boston, Massachusetts, not far from Lenox. Climatic 

 conditions in these localities are similar. Careful in- 

 spection was made of 20,605 P me trees under 20 feet 

 high. Plots consisting entirely of young 

 pine growth were selected, so that each 

 tree could be thoroughly examined, and 

 every white pine on the plot was in- 

 cluded in the survey. The resulting data 

 show that since 1916, with not to ex- 

 ceed 80 per cent of the currants and 

 gooseberries removed, the rate of blister 

 rust infection is approximately 2100 per 

 cent less at Lenox than at New Boston, 

 where no bushes have been removed. 

 Blister rust infection at New Boston, 

 since 191 6, has taken place at the rate 

 of 571 blister rust cankers in 10,000 

 pines. At Lenox, in the same period, 

 the rate has been only 26 cankers in 

 10,000 trees, or less than one-twentieth 

 of the amount of infection found at New 

 Boston. It should be noted that in and 

 surrounding the survey plots at Lenox, 

 an average of 47 currant and gooseberry 

 bushes per acre was found in 1920. The 

 average height of these bushes, however, 

 was only 1.3 feet. It is apparent, there- 

 fore, that when the Lenox area was 



covered by the crews in 1916, small 

 bushes were missed and others have 

 since developed from seeds and sprouts. 

 Dr. Pickler classified the bushes accord- 

 ing to origin, and found that 18 per cent 

 had been overlooked in 191 6, 62 per 

 cent were seedlings that grew since 191 6, 

 and 20 per cent were sprouts that de- 

 veloped as a result of breaking off the 

 tops of the bushes instead of uprooting 

 them. 



The results of Dr. Pickler's study 

 merely confirm the conclusions previous- 

 ly reached by scientific investigators. It 

 has long been known that the blister 

 rust must pass through two stages of 

 development on currant or gooseberry 

 leaves, before it can infect the white 

 pine trees. At last year's conference, 

 Dr. H. H. York reported that he found 

 the sporidia which produces the disease 

 in the pines, to retain their germinating 

 power for a period of less than ten 

 minutes, even when the humidity and 

 temperature are favorable to long life of 

 the spores. This explains the reason that under ordi- 

 nary forest conditions, currants and gooseberries do not 

 need to be uprooted farther than 200 to 300 yards 

 from pines. 



In the majority of cases, currants and gooseberries 

 cause infection on pine trees only within a limited radius. 

 This is demonstrated by studies made of the percentage 

 of pine infection in the zones around isolated currant 

 and gooseberry bushes, or groups of bushes. With the 





Photograph by A. B. Brooks. 



A FEW SKUNK CURRANT PLANTS FROM A CONTROL AREA 



Skunk currant grows as a mat of tangled, prostrate stems in moist localities. The bushes 

 shown were pulled by a crew and piled for burning. Although finding and uprooting the 

 skunk currant plants is tedious work, the inspectors find that the crews do itl efficiently. 

 On 77 acres of swampy land, a crew removed 34,752 skunk currant plants in the first working, 

 and only 46 additional plants were found when the checking crew went over the ground again. 



