Milford chronicle., 1939-03-17
WHITE PINE BLISTER
RUST SURVEY In STATE
Us. Bureau Estimates White Pine
Trees In State Worth Sl5O.OOO

neeuled pines states that slight,
less than 5000 ornamental whit,
pine trees and approximately 81
acres of planted native and natural
lied white pine stands have been 10
Gated and charted in the State. The
total value Of these trees is conser.
vatively estimated at $150,0OO. The
white pine, in addition to enjoying
wide recognition as an ornamental
tree, Is recommended by the State
Forestry Department as a refores-
tation tree comparable in growth
rate to the fast growing loblolly pine
indigenous to the lower half Of the
State. The survey has been under
way In the State since August 1898.
The blister rust of five needle
pines, (Cronartium ribicola) often
called white pine blister rust, is a
fungus disease of European origin.
In 1897 1t was found to have invaded
Delaware and unless adequate pro-
lection measures are taken may do
considerable damage to five needle
pines. II is believed to have been
brought into this country in New
England about 1900 and has spread
to practically every part of the coun-
try where five needle pines grow ex-
cept a limited region south of Vir-
ginia. The disease does not spread
directly from one white pine to an
other, as does many fungus diseases,
but requires the presence of an al
ternate host plant in the form of
wild or cultivated currant or goose
berry bushes commonly referred to
as Ribes.
Briefly stated the life cycle of the
disease is as follows: Spores are
produced on the infected parts of the
diseased white pine tree in the
spring of the year and are carried
by the wind for long distances. I'm
der favorable conditions these
spores infect the leaves of currant,
gOOseberry and Towering currant
bushes, forming an orange cOlored
rust on the under surface of the leaf.
This rust then spreads from one leaf
to another on the same bush Or other
bushes in the immediate vicinity. Be-
ginning about midsummer, spores
which may infect the white pines
are produced on the leaves of the
bushes. The disease enters the pine |
needles and grows downward into |
the bark, causing what is known as
the canker. The infection progress
es downward in the branch and ,
limb, killing it as the result of grid
ling. Later 1t may enter the trunk.
killing the top of the tree, growing
down the trunk until the entire tree
IS killed. Occasionally trees are kill
ed as a result of the girdling of a
large number of branches. The dis
ease parts of the tree show a vary
ng amount Of swelling with yellow
of the bark. Mature
,ankers when fruiting show white
)listers bursting through the bark
rom which orange colored spores
IRE expelled in great numbers. In
Iddition to the swelling and yellow
the diseased sections
an be identified by dark brown or
orange colored spots
sually about 1-16 inch in diameter.
"The distance the disease spreads
aries with the ability of the spores
D live under variable degrees of sun
ght, temperature and moisture. I'm
er ideal conditions the disease may
pread from diseased pine up to $50
r more miles to currant or goose
erry bushes. Under average condi-
ons the disease will not spread
lore than 900 to 1000 feet from
ushes to pine except in the case of
le European Black Currant which I
lay spread disease for Y of mile
r more. The control lies in the de-
ruction Of all currant and goose J
erry bushes within at least 900 $
et OF the pines and all European 7
lack Currants within one mile of n
10 pine. =
Beginning about 1916 represen-
tives of the U. S. Department of
griculttIre carried on a frequent
spectiOn throughout the State. but O
, disease was found until the fall -
ese inspections 1t was recommend =
that European Black Currants be =.
stroyed since they are frequently i
sponsible for the long distance =
read of the disease. This variety h,
currant was to a large degree fo
minated in the State as a result
this work. however, few bushes a,
This eradication of Eu- M
pean Black Currants is believed to -
largely responsible for the delay tv
the disease having become estab- NJ
he'd in the State.
Delaware Is fortunate in that wi
Id gooseberries and currants are lis
all probability not present in the
ite. In many states in the east as Co
II as the white pine regions of the Df
eat Lakes and the west, wild
and currants are so hi
lndant that In many cases it is MI
possible to attempt to eradicate
m, which will in all probability HC
ult in the complete elimination tol
five needle pines over many thou
IDS of acres. Gooseberries and am
rants are seldom grown CONNER Fr
lily in Delaware and therefore are I
considered as highly important. be,
At present an intensive survey is ing
ne conducted to determine def !
sly whether or not wild or escap- str
cultivated gooseberries or. cur roo
is are present in the State. An mi mi
,mpt is also being made to deter F
e to what extent cultivated BUSH for
are grown for commercial or 20, 20,
ne use. This work is being car -
on under the direction of the r
S. Bureau Of Entomology and DIV ,