Rogue River courier. (Grants Pass, Or.) 1886-1927, 1910-12-02
The Pear Blight and the Best
Way of Getting 1t Under Control
Byp J. O'Gara. Copyrighted by Mail Tribme0

0uUlDbI Vi plOoDOAAAS
comparatvely easy to discover the
methods by which the germs were
carried about. Not only In natural
infections, but in those artificially
produced with pure cultures, insects
were found visiting the blighted BIOS
SONS. The germ multiplies In the
nectaries of the blossoms as readily
as It does in a culture medium, since
the nectar glands exude sugary SOL
ution which furnishes the organism
the necessary food supply. The en-
lyme or ferment given off as a by
product by the germ dissolves the
delicate cells beneath, permitting the
germs to pass downward with the
greatest OF ease. Ordinarily, the en-
tire pear is sealed up with an air
tight and water-tight cuticle COM
posed Of a thin layer Of the same
composition as cork. Even the
breathing pores are plugged up dur
ing the dormant season Of the tree
so as to prevent evaporation from the
tissues. This cuticle keeps out the
pear blight unless 1t Is injured or
broken. The nectary Is not covered
by cuticle and Is, therefore, an easy
for the germs to enter. The gummy
exudate pushes out OF the infected
blossoms adding to, or even taking
the place OF the nectar; and honey
!. bees, wild bees, wasps, flies, and
perhaps fifty other species of insects
visiting the pear blossoms or apple
, blossoms carry the germ-infected
material. When once the insects
mouth parts and feet are infected,
blossoms which it visits thereafter
become in turn, infected as the in
sects drop off a few germs into the
, hectares The blight virus being al
so a sticky material and usually re-
quiring a considerable mass, speak
ing from the microscopic standpoint
to produce infection, is not blown by
, the wind. OF course, the negative
; OF such proposition is hard to prove
concluslvely, but experiments have
been made to decide this matter by
: covering blossoms with mosquito net
q ting along the side OF artificially in
a fected flowers, and is was readil!
! found that the uncovered flower Wis
: tied by insects contracted the blight
v while those covered by bags, mos
q quito netting and other materia
n which kept out insects remained fre
q from the disease. Occasionally,
!. humming bird visits the infecte
:. blossoms. This has been observe
q in number OF instances. Doubles
"a birds get the gummy material o
4 their feet and carry the blight Ion
~ distances. However, we look upo
~ insect distribution as by far the mos
~ immediate means OF infection, esp'
70 cially in blossoms; in carrying tn
~ blight from flower to flower, tree
~ tree and orchard to orchard, a
- though doubtless occasional long di
~ distance distribution is accomplishe
~ by birds or some other agencies, II
N cluding man himself After the bio
Al soming period is over, or even befo
be II Is entirely finished, blight may
,s found attacking the tender twig
no Our common insects have been four
A. TO be active agencies in not only d
he distribution OF the disease, but
,w puncturing the tissues and there
nv introducing the germs into the
IN While II Is easy TO prove that inset
1, case some OF the infections OF sor
mr. OF the twigs, II is not absolutely c'
be tain that they do all the inoculatir
,ho Twigs are sometime found WI
- blight started in the axils OF I
or leaves or in the tender bark where
.ho punctures can be found on care
,do examination II Is possible that
,uv germ may enter in damp weatl
INV through growth cracks where
Al cuticle Is ruptured, exposing the 4
,vo der tissues.
be That insects really carry p
,ra- blight germs on their feet and mo,
hen parts have proved by captur
on these insects In infected orchards {
old allowing them to walk about on T
nj pared culture plates known as P'
her dishes, which contained q substa
has In which germs might make grow
= n In from "a TO as hours colonies
,ro. germs would be found growing II
iye- the points where the insects wal
res upon the culture medium. BY
the oculating growing shoots from N
,ths cultures typical cases OF blight W
Toes produced
In the numerous experiments
,rm have been made atomizing the Sc
,rcd on the tissues, II has resulted 1
tho failure in most cases, except WI
NO. punctures through the cuticle h