United Stales )Department of Agrirc;ulture,
BUREAU OF PLANT INDUSTRY-Circular No. 38.
B. 1% GALLOWAY. Chief Of BureI P
EIRk(I' Ik\N (A IR0.\V1, RI Si" N T I "! I
AM EII(CA. ||'\ ^'
i ) PE I. EY S'- .\A I)U(ING,
/',' ,,'..* .t, Of ficc of h( i rt iys H iIt vs,. iln Forest I ,
ID I);-, tile past decade an intelligent appreciaitinoi of forestry mueth-
ods hlas been developed in this country. This ihas produced in the
Northeastern and North-Central St:tes an 1 ), .1 -ii._'ly insistent demand
for .\ iiii, trees suitable for th purpose 'es o)f reforestation at a reasonable
price. A 1.01_'C import trade lias therefore developed. The white pine
(Pitnus srobuls L.) has been the principal timber tree of the section
above mentioned, and very InatuIrally it hias bec('ome thle pril iip.1 species
used in reforestation. I ence, the im port trade is largely concerned with
this single -I, i, -, and white-pine trees are now coinii ,, into the country
at the rate of several millions a :.,.ir. ThIis is t.,lii,._ place with abso-
lutely no inspection 1.-21.1 itions other than local ones, which are utterly
inadequate to deal with the problem.
American plant, llil..,-t- have been anticilathi- tle introduction
of the Er,,i ,i blister rust (l' P rid rnitm shtroti Klebahn) on tlie white
On June 5, 190i)), Mr. C. I. l'ettis, New York State lForester, asked
the writer to examine some three-year-old -, lliii' which were imported
this -1ri), from (Germany. No fruiltw bodies were found present ()on
these trees; but a foreman who had planted others of the same lot
observed that s()me were al)pparently diseased and gave so good a
description that the writer was convinced that 1"' ridlcrmu i lit .strobi
had actually been imported on tlhe trees. A personal ('examination onil
.June S of somle thr, 'v-,k .i-old trees which had been imported in 19(i,
resulted in the discovery of fruit ii2 bodies of the l'' ii-,u- Further
search has shown that the disease is present, so far as now known,
only in trees from J. Hleins S;ine, of ialstenbhek. (ermianv. Fur-
ti ih it lias thus far lIeien found only in tr('ees which are now
I ii. :t."'l
EUROPEAN CURRANT RUST ON WHITE PINE.
three years old, i. e., of the .-...liii: of 1906. But trees from this
nursery have been distributed throughout the Northeastern States and
Ontario. Trees of the same age from other European nurseries have
been examined, but none of the disease has yet been found in them.
It is apparent, then, that a very severe and general infection of the white-
pine -',:-1iijs took place in this nursery in the year 1907. This con-
clusion results from the two facts (1) that the fruiting bodies are situ-
ated on the wood formed in the second year and (2) that the fungus is
known to incubate for at least a full year on white pine before fruiting.
Because of the general distribution of the disease in Europe all imported
white-pine trees must be under suspicion until proved free of this fungus.
LIFE HISTORY OF THE FUNGUS.
The fungus PIeridermirnm strobi Klebahn was at first thought to be a
distinct species, but has 1-1qii niitl.N been proved to be one stage of
the blister rust of currants and gooseberries known as Cronartium
ribicola Fisch. de Waldh.a
The life history of the fungus is as follows: Spores from an infested
currant or gooseberry bush are blown to some neighboring white-pine
tree. There they germinate and attack the bark of young stems and
branches. The mycelium vegetates in the soft inner bark until the
second spring after infection took place. Early in the second spring
the diseased bark becomes thickened and the stem of the yuui'- tree
becomes swollen at the infected place for a length of one to several
inches. In Germany the fruiting bodies break through the bark from
April 20 to June 1. The fruiting bodies at first are light orange in
color, rounded more or less, and project from the surface of the bark
from [-,."i^]tlI to one-fourth of an inch. Later they break open irreg-
ularly and the spores are scattered by the wind. After the spores are
scattered there is left a whitish membrane which is v,-iy fi.,_'ile and
which also is soon blown away or washed off by rain. This leaves only
the empty fissures in the bark through which the fruiting bodies extruded
as evidence of the presence of the fungus. These fissures are very char-
acteristic to one who is skilled in such matters, usually i,.iig somewhat
wavy in outline, longer than broad, and with the edges of the bark
slightly elevated by the escaping spores. The spores produced on the
white pine in turn infect currant leaves upon which they may alight.
Here thile period of incubation is relatively short, var.iii. from 15 to 40
On the currant the fruiting bodies app .ir at first as tiny reddish dots
on the under surface of the leaves. Later, the fruiting bodies form
small thread-like tendrils, also on the under surface of thle leaf. These
spores may infect either the currant or the white pine. The spores pro-
a Arthur, J. C., North American Flora, vol. 7, pt. 2, p. 122. P'n7.
duced on thit white pit' can llot (irectiyv inIfect the w hile plin I ut muwt-
attack the currantii ()i tin(l curri;it tin ri-t is n tl() kiltio to 1w piren -
nIial, but Ion tl l whlit, ti'ic it remi:ils alive ;is 1( a_ tOw stei iior b t ih
which it inltf-s.
FIELD CHARACTERS OF THE DISEASE.
Thie characters Ientioned kelow aipply Illv ly to th diseas- ill thlrc-
yeair-iold tri-s, as tais, ath tle oly oes e P't se(n lwhich w aff'cteiI.
IThei' l'eted trc hias a peculi r si-lith' ntd appeara:ti lce' so far a: s tlie top
is cotcelrni, d, \ihil tile sti, iis sw(di(- ll (i r ienlarged :,n o(irillally. .Ne(w
'21,' \([i is n itlich shorter than on I nol l I li . d'i,,, Inev\ r 1,il over o, e-
half tihe normal 1' ith. Tlie stein is swoll'tnt at t lt inlccted tilac ;lam
is usually soinlew l}at spimtleiC ltit (L. lil sonei' ,:ase-s it is swollen i lti( ,_
the entire 1, IIl_ l (4 tile second vvar's growth, lhnt willi thlis lapplens it
is swollen i ,,-,Iarly, the bark having a huiichy ;ipl earallc nc ill places.
A se,'in li, With all abnormally tliik stemil or one Wihich is irregularly
thlickeleid without anlly tappari-nt injury to) tli bark is di-seased. A inor-
mial sewlliii, will have a ste-I whichl is (luite iuniformi in size throughout
each year's _'. 'it. AnyI injury, sucih :Is a lbruisc, will cause swelling\
only at the f...' f tlhe brokeI n airk. t)f course thlie fruit, b' odies thiel-
selves are tihe best character bvy whici to ri *.niz th infe-std wliity pines
or currants, bult on tihe former they are preseit on'ly i llite spri,, -. while
onil thle latter they are present during tie late sumnnier and fall.
11 In r.- is a native rust of wild currants which is common in some
sections, and this Imust not be confused with ( 'rntin i in r'ibicolt, whi(l
is entirely distinct and of ditTfferent appearances.
DAMAGE CAUSED BY THE RUST.
The know ,1 ,' possi -esd by American pathologists as to the amount
of l.iii.,:, caused !)y thle rust is mostly based on statmenliets iln iuro-
pean literature. 0n tlhe currant there is very sminall (1 il, I but this
is tile mIost 1 _', rouIs -.''' in tihe life history of thie fungus, o"i'.- to
thi' possible infection of ally I.. ji=lhol-I,= white pines. (in the white(
pinle t le ii i ,_':e is very considerable. o';:,_. trees are kille(l outriglht
and small braincheis o hit_, trees are kilhln. In certain places inll
Euirope, notably ill IIHollandl, at (ldenhurg, (;erany., and at Moscow,
hRussia, this disease is so serious that tIn, cultivation of white pine Lias
been a!bandmoned. InI other places tli rus-t is aibundlant, anl especially
ill tile vicinity of lIamliir_. (wrilletalNy.
METHODS OF COMBATING THE RUST.
Very briefly stated, the practical mtetiihodls ofi comat,,- tills disease
are as follows:
(1) Examine all currant busl-s near infected plantatiotns or n--urselries
of white pine andI burn all that are affected ; or, better. destroy ;all cur-
Cil. :; i
ECtOlIEAN C/rfZANT I ST ON WiHl1IJ: I'lN1F.
4 EUROPEAN CURRANT RUST ON WHITE PINE. <-_--
rants in the vicinity, if practicable. This should be done from July 15 -i
to the fall of the currant leaves. _
(2) Inspect imported white-pine trees and burn all that show any >-
evidence of the disease.
(3) Inspect for at least two years all white pines located near infected' >
currant bushes and burn all that become infected.
0(). iji- to the peculiar character of this disease it can not be detected
in white-pine seedlings by any possible method of dock inspection
unless the fruitiii. bodies are present or have been present. The fungus
lives for one year in the bark without giving external signs of its pres-
ence and can not possibly he detected during this period. In order to
have effective inspection of affected trees in the field the most expert
supervision is necessary. (reat care must be taken that every seed-
ling is located and examined, all dead and dying ones removed and
burned, and every suspicious looking tree burned. Wherever necessary,
the Office of Investigations in Forest Pathology will give advice and
supervision. Each State is now taking up the problem and will, it is
hoped, be able to cope with the situation. In view of the great danger
from this disease it seems best to advise that no more white-pine seed-
lings be imported.
It is believed that all large recent importations of European stock
have been located and so can be promptly inspected, but it is entirely
probable that many private importations have been made which have
not been located. It is imperative that the presence of all such stock
should be reported to the State or National authorities, so that prompt
inspection can be made. Otherwise all efforts that are now being made
to eradicate the disease may be in vain.
JAMES WILSON, I D.....L. T
Secretary of Agriculture.
WASHINGTON, D. C., July 3, 1909.
0 8 .S DEPOSITORY"
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