ENTOMOLOGY AND PLANT QUARANTINt: 
35 
EXTENSIVE AREAS OF PINE STANDS MAPPED 
For several years considerable numbers of relief laborers under careful super- 
vision have been assigned during the winter months to the preparation of maps 
showing the location and boundaries of white pine stands. The work is done 
during a season of the year when RHjc^ eradication cannot be carried out 
efficiently. During 1930, 4 J 69,628 acres were so mapped, this acreage includ- 
ing not only the pine stands contained therein but also the area of the sur- 
rounding control zone. Such mapping has been carried out during the last 
several years on 15.938. .j69 acres of control area, most of the work having 
been done since 1932. These maps are proving a great aid to Ribes eradica- 
tion during the summer. 
CULTIVATED EUROPEAN BLACK CURRANT DESTROYED IN LARGE NUMBERS 
Several of the so-called black currants are so highly susceptible to blister 
rust and distribute blister rust spores in such tremendous numbers that they 
constitute an exception to the general rule that a 900-foot border zone around 
pine stands is sufficient to provide protection. The Department accordingly 
recommends that they be destroyed throughout white pine regions. Two such 
susceptible species exist in the Pacific Northwest (Ribes petiolare and R. 
hracteosum ) . The first of these grows in large numbers along some of the 
creeks in the western white pine region of Idaho and is destroyed by the use 
of chemical sprays. The other is not a problem in the principal western 
white pine areas but is of importance locally in parts of the Cascade Moun- 
tains and Sierra Nevada. 
Of the cultivated species, the European black currant (Ribes nigrum) is 
by far the most susceptible, and most of the Dine-growing States have ac- 
cordingly outlawed this species completely. It was originally planted in 
considerable numbers in the Northeastern States, but was the subject of a 
general eradication campaign throughout that area 5 to 10 years ago, so its 
elimination has now been largely accomplished. A like campaign was carried 
out about the same time in the Northwestern and Pacific Coast States where 
\\ estern white pine and sugar pine are of commercial importance. Since 
(.niergenoy relief labor became available, the Lake States have been engaged 
in a similar program. During 1936, 87,226 Ribes nif/rum were eradicated, 
nearly all of which occurred in the Lake States region. 
APPROVAL OF MANY NURSERIES FOR PINE PRODUCTION 
Reforestation has expanded on a tremendous scale since the organization 
of the C. C. C, Soil Conservation Service, and other recently established 
agencies. The nurseries producing the trees for the reforestation program 
have included large numbers of white pines in their stock, and accordingly it 
has becom^e necessary to carry out extensive i^f &e.s-eradication programs 
around these nurseries in order that the young pine trees produced therein 
may be healthy at the time they are sent out. The nurseries that succeed 
in maintaining freedom from Ribes in their environs are issued Federal per- 
mits which enable them to ship their white pine stock interstate. 
Such nursery sanitation work was carried out in 1936 in and around 93 
nurseries, of which 32 were located in the Northeastern States, 18 in the 
southern Appalachian region, 41 in the Lake States, and 2 in the western 
white pine area. These nur.series were growing 134.175.374 white pines. In 
protecting them, 1.058,518 Ribes were destroyed in 1936 on 49,781 acres. 
BLISTER RUST CANKERS MAY BE CUT OUT ADVANTAGEOUSLY ON VALUABLE 
PINES 
In some ca.ses a single blister rust canker is sufficient to girdle and kill a 
pine tree, while in other instances many hundreds of cankers kill all the 
individual branches and thereby destroy the tree. The cankers increase 
in size so long as the trunk or branch on which they are growing continues 
to live, and branch cankers, accordingly, frequently reach the trunk and 
kill the tree, though in the case of large trees this may take from 5 to 20 
J ears or longer. 
During this period of growth the removal of the canker will often save 
individual trees of high esthetic value, a method which has been employed 
effectively in such places as parks and along roadsides. To a limited extent, 
canker removal has been tried in the State forests of New York in connection 
with pruning, thinning, and other work for improvement of stand. 
