Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1897-04-01
PARASITIC PLANT DISEASES.
A Lecture on The Ways in Which They Are
Spread.

a lecture on the spread of parasitic dis
eases among plants was recently ueiN
cred, before the Massachusetts HorllG wv,
| tural Society by DR. Erwin f. smith
assistant pathologist. division OF Vese,
! table physiology and pathology, United
States department of agriculture. WASH
ington, ID. c. He said, in part: .,
Il shall for the most part neglect ~ tn ne
well known dissemination of parasites
by wind and water. and deal CHEEKY WIN
| the methods which are to larger eM-
tent within our control. Farmers, lruit-
are not infrequently responsible for the
spread of diseases. There are now SO
many who grow crops for market, anu
the competition is so close and the pro
fits so small that even the most expert
enced must stop every leak in ms eA-
penses. Therefore the avoidance of para
site diseases is most important,
Most diseases which prevail extern
sively and are known as catching dis
eases are due to parasites. These piant
parasites are plants or animals when
have in some way lodged on or gained
an entrance into the 'host-plant' ana
there multiply to its detriment. Many OF
these organisms are exceedingly small,
so as to be overlooked. and are well pro
speak of saprophytes and parasites, the
former being fungi which derive their
nourishment from dead and decaylns
| substances. and the latter nourshed AT
| The most of this address will be devoted
| to showing how certain parasites succeed
| in getting from one plant to another. II
| is commonly assumed that their repro
| ductive bodies, floating through the air:
lodge on the plants; but l am inclined
] to believe that often the chief danger OF
| infection lies in other directions for rea-
sons which I will now explain.
! I'D. Spread by insects: The gnaw-
| ings. borings and punctures of insects
| though often injurious, are by no means
Al. ;,,,,, ,t.1, tl,nNr I'D
Pear blight: 1t has been discovered that
| the germs of this disease We're carried ON
the mouth parts of bees, which haa
| visited blghted pear blossoms: that the
| bees passed from such flowers to healthy
| ones: and that subsequently the blight
appeared on the latter. 1t was also
| shown that flowers covered with mosqui-
| to net remained free from blight. while
the unprotected. insect-visited ones
blighted freely. Apparently pear blight
| is disseminated only through the agency
| from the tree in the form of small sticky
| or gummy masses. and probably all the
| spring outbreaks of pear blight start
from them as a result OF insect visits;
| cucumbers. musk melons, pumpkins and
squashes: This is due to a sticky white
| micro-organism which fills the water
| ducts of the plants and causes Il sudden
collapse of the plant. 1t is readily com
municated by the striped cucumber beetle
| and by squash bugs. The insects carry
| the. vdrulent sticky germs on their beaks
and deposit them in the next plant bitten.
| Bacterial brown rot of the potato. toma-
| to and egg plant: The department of
agriculture has recently published
| bulletin on this subject. Insects feed on
| the diseased plants that are swarming
with the parasite. and go to other plants
| which are bitten and subsequently be-
come diseased The disease may he
known by the sudden wilt of the foliage
| the stems becoming brown internally and
| shrivelling.
"(2) Spread by snails and slugs The
| damage done by these animals as carriers
| Of disease is greater than the injuries
| they induce by feeding. ! shall refer to a
few cases only. O. Wagner's Expert
name of Wagner experimental with
| downy and powdery mildews, as comyce-
| tous fungi: and rust fungi Snals We're
transferred from diseased to healthy
plants and the latter became infected.
| fhey We're fed various parasitic fungi
and subsequent examination of the cX-
creta showed that the spores of these
| fungi passed through the animals unin-
| iured and in condition to terminate. 90
| Mr.. Galbraith. an Englishman. living in
| the Seychelles islands. has found snails
largely responsible for a disease of the
vanilla prevalent in those islands. 60
| The bacterial brown rot of cabbage; this
blackens the vines, causes the leaves to
| fall off and prevents the formation OF
heads. | have found that the common
greenhouse slug disseminates the micro
organism to which this is due and insects
also probably carry the disease.
't3.) Spread through the manure pile.
Rarnyard manure always contains great
variety Of organisms. most of which are
harmless to plants. But sometimes spores
of parasites get in through fodder or bed
ding and oftener through mouldy or rot
| ting vegetables thrown on the pile. a.
The watermelon wilt: This disease lives
over winter in the dead stems and grows
eadily in manure. | Investigated a case
where a planter in South Carolina lost
nearly his whole crop by this disease. the
plants being most severely attacked in
The place which had been most carefully
Ilanured. In order to have a fine crop
the planter had raked stubble from the
whole farm, including refuse from the
last years melon field. where there had
been some disease, and made compost
heap in his barnyard. He had unwit-
tlngly made an immense culture bed of
his manure pile. and when the infected
manure was put under his melon hills
tle most disastrous results followed.
o. Smut diseases: Some of the smut
| diseases are well known to be transmits
slble through fresh manure. and this
should never be used on fields of cereals.
Cd Other diseases: Cucumbers, turnips
and other plants have become diseased
that manure should at least be kept free
| rom the rubbish of plants that have been
diseased. a. Certain parasitic diseases
live and multiply in the soil as sapro-
phytes. ready when opportunity offers to
become parasites. These soil fungi get
from field TO field. sometimes by irriga-
| ton or by floods sometimes by the plough
or tools. Onion smut. potato scab. etc,
are examples of these soil parasites. ]
snail mention particularly only one type
the Fusiorium diseases Of the United
pants subject to them. m all the trouble
is due to parasitic clogging of the
water ducts. The plants | have found
so affected are cotton. COW pea. water
melon, cabbage. potato. tomato, sweet
potato and pineapple. The cause of the
II ouble is too frequent growing of the