FREDERICK, Md. - Each
year, noxious weeds cut U.S. crop
«elds, reduce use of pastures, and
Ist millions of dollars in ex
pensive weed control measures.
Most of the culprits, ironically,
are not native North American
weeds at all, but species ac
cidentally introduced from other
countries. Having left their natural
enemies behind, these exotic
plants often spread unhindered
through U.S. crop and pasture
land, especially where con
ventional control by herbicides and
tillage is inadequate or infeasible.
Help, however, is on the way.
Leafy spurge, curly dock, yellow
starthistle, musk thistle, and other
serious weed pests are being
reunited with their disease-causing
enemies at a unique U.S. Depart
ment of Agriculture quarantine
facility in Maryland. Agricultural
Research Service scientists
William L. Bruckart and Dennis R.
Johnson and project associates
Demetrios J. Politis and Sherry K.
m
inter of the USDA Plant Disease
ivesearch Laboratory in
Frederick, Md. are importing
pathogenic “rust” fungi into the
United States to attack these exotic
pests.
A rust fungus introduced into the
environment should spread in area
and concentration, markedly
reducing the' infestation of a
particular weed for years to come,
according to the four scientists.
For fanners who find herbicides
and cultivation too expensive or
infeasible, biological control may
mark the difference between
productive and virtually useless
land, plant pathologist William
Bruckartsaid.
Finding a safe, yet highly ef
tective rust to fit that bill,
however, is a time-consuming
task, according to Bruckart.
Fungal pathogens must first be
Ullected in the countries where
they convolved with exotic weeds.
After being gathered as dried
spores or infected plant parts, the
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Noxious weeds reunite with exotic enemies
fungi are shipped to Frederick and
stored in liquid nitrogen. Then
begins the patient process of
discovering which fungi are the
most deadly to spurge, thistle, and
other weeds, and yet pose no threat
to U.S. crops.
“We spray the spores onto weed
plants grwon in our containment
greenhouse,” said Demetnos
Pohtis, whose yellow starthistle
research is funded by the state of
California. “It can take as long as
three weeks to determine if a
particular strain of fungus is ef
fective against the weed.” Once
the most potent strain of pathogen
is identified and found to be safe
near U.S. crop plants, great
quantities of the fungus can be
reared for release.
“Before a promising isolate of
rust can be released, however, it
must be tested on at least 56 closely
related or economically important
plants,” said Sherry Turner, who
studies leafy spurge on a
cooperative grant from Montana
State University. “We can’t in
troduce a rust that attacks crops as
well as weeds.”
Fortunately, most rusts are
“host specific” and won’t attack
plants other than their host weed.
Yet becasue of the ptential risk m
bringing unknown plant pathogens
into the Umted States, physical
security at the Fredenck Plant
Disease Lab is tight. The
Frederick lab, in fact, is the only
USDA facility authorized by
APHIS, the USDA’s Animal and
Plant Health Inspection Service, to
import such agents.
Turner and her colleagues work
m double-walled “containment”
greenhouses kept at slightly
negative air pressure (air flows in,
not out) to prevent fungus spores
from escaping. Scientists entering
the greenhouses must don gowns,
and caps similar to those worn by
hospital doctors. Personnel exit
through a shower, and all
materials leaving the greenhouse
must be sterilized beforehand.
A local Veterinarian will be at our Mill on
Saturday. May Ist, from 9-12 AM
MANURE SAMPLE
Biological control’s potential for
success, however, eases the
tedium of these necessary
procedures. Fredenck scientists
led by R. G. Emge (now retired)
recently used an introduced rust to
decimate Eurasian “rush skeleton
weed,” Chondrilla juncea, a
serious Wheatland pest in the
Pacific Northwest.
Following the lead of Australian
scientists at the Commonwealth
Science & Industrial Research
Governor signs Noxious
Weed bill into
HARRISBURG - Gov. Dick
Thornburgh has signed legislation
creating a special committee with
broad authority and strong en
forcement powers to control
noxious weeds that pose a threat to
public health, crops and livestock,
agricultural land, gardens and
lawns.
The governor said H.B. 1429,
sponsored by House Majority
Leader Sam Hayes (R., Blair),
establishes the Noxious Weed
Control Committee, composed of
the secretaries of the departments
of Agriculture and Environmental
Resources, the executive director
of the Pennsylvania Game Com
mission and the chairmen of the
state House and Senate
agricultural committees.
He said the committee is
charged with developing a noxious
weed list, which must include
Canada thistle, chicory, Johnson
grass, marijuana and multiflora
rose. Landowners who have
noxious weeds growing on their
property are required to destroy
them to prevent reproduction and
spread.
Organization in France and
Australia, the Fredenck scientists
isolated a potent strain of the
exotic fungi Puccima chondrillma
and applied it to skeleton weed'in
greenhouse and field tests. The
results were astounding.
As reported in the 1981
Phytopathology article by Emge
and colleagues J. Stanley Melchmg
and C. H. Kingsolver, “rusted"
skeleton weed produced 65 percent
fewer seeds the first year and 94
percent fewer the second year.
“Our current law controlling
noxious weeds has been regarded
by some as ineffective,” Thorn
burgh said. “Several plants con
sidered injurious to agriculture are
not regulated. A |l5 penalty for
property owners who fail to
destroy weeds is insufficient, and
local officials are hesitant to en
force the law.”
The governor said that under the
new law :
*The Noxious Weed Control
Committee can revise the noxious
weed list whenever necessary.
Milk referendum opponents to meet
LANCASTER - Dairy
producers opposed to the Penn
sylvania milk reierendum will hold
meetings in Blue Ball, Lancaster
County, on Monday and in
Myerstown, Lebanon County, on
Wednesday.
The Lancaster County meeting
will be held Monday at 7:30 p.m. at
the Blue Ball Fire Hall, near the
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During the second season, two
thirds of the rusted plants died
prematurely. An this weed control
resulted from only one application
of the fungus.
“We are very encouraged by our
major success with skeleton
weed,” said William M. Dowler,
director of the Plant Disease
Laboratory. “Work underway now
should lead to equally significant
improvements in the control of
leafy spurge, thistle, and other
noxious weeds.”
law
’Violators can be charged with
either a summary or misdemeanor
offense, facing up to a $2,500 fine
and/or one year imprisonment.
•The state ' Department of
Agriculture has broad law en
forcement powers.
“While most property owners
comply with requests to destroy
noxious weeds, this stronger
authority is necessary because of
the harm these weeds can cause
our agricultural community,” the
governor said.
intersection of Rt. 23 and Rt. 322.
The Lebanon County meeting will
be held Wednesday at 7:30 p.m. at
Friedens Lutheran Church,
Myerstown, at the intersection of
Rts. 422 and 645,
The meetings are sponsored by a
group of concerned dairy
producers, who have formed the
No Milk Tax Committee.
10/15
Financing
Available
of-*