Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a process and a
composition for controlling undesirable vegetation.
More particularly, the present invention is directed
to a process for controlling the growth of velvetleaf
by applying Colletotrichum spores thereto.
This invention also relates to the growing
of a fungus, Colletotrichum coccodes (Wallr.) Hughes,
collecting spores, concentrating the spores and for-
mulating the spores for application over geographic
areas to control undesirable vegetation, namely velvet-
leaf (Abutilon theophrasti Medic.). According to the
invention, after application the spores germinate9
infect the velvetlea-f and result in a pathogenic
disease which terminates or reduces the growth of the
undesirable plant.
Velvetleaf, often called button-weed or
elephant-ear, is an erect annual broadleaf plant
species from 0.3 to 3m in height, but generally grows
to just above thecrop in which it is growing. It is a
prolific seed producer with 17~000 seeds per plant
being produced on average. The seeds can persist in
the soil for up to 50 years and are unaffected by pas-
sage through animals or by ensilement.
Velvetleaf is widely distributed -throughout
most of the United States and much of southeastern Canada.
It is considered as one of the most common and costly
weeds in the North Central region of the United States.
- 1 - ~
~2~ 5S
This weed species occurs in waste places, vacant lots,
gardens and cultivated fields. Velvetleaf is a serious
weed problem in corn7 soybeans, cotton, wheat, oats,
barley, sugarbeets, sunflower, tomato and other culti-
vated crops. Infestations of this weed presently cause
significant yield reductions in these crops and the problem
is increasing due to the prolific seed production of
velvetleaf and the difficulty in the control thereof.
In most cropping systems~ chemical herbicides
have been developed to provide acceptable to excellent
control of many grass and broadleaf weeds. However,
widespread and continuous use of certain herbicides
has favored the establishment of problem, difficult to
control weeds such as velvetleaf. A cornbination of
chemical herbicides and cultivation are presently used
to control velvetleaf populations in various crops, but
these methods are inadequate for the control of velvet-
leaf as infestations of this weed are continuing to
increase in size and in nurnber. Problems with cultiva-
tion for the control of velvetleaf includeo
1. appropriate timing to avoid injury to
the crop plants is difficult,
2. lack of control of late germinating plants,
3. it cannot be used in new cropping systerns
such as solid seeded soybeans (SSS).
The problems associated with the present
chemical herbicides for velvetleaf control include:
1. lack of soil persistence resulting in no
control of late germinating ve~vetleaf
20 most chernical herbicides cause some det-
rimental effects to the growth of the crop,
3. chemical herbicides may adversely affect
non-target organisms,
4. toxic residues of chemical herbicides may
persist in the environment or contaminate
our food.
Dinqley, J.M. and Gilmour, J.W., New Zeal. J.
For. Sci. 2(2): 192 (1972) discloses the C. coccodes
(Wallr.) Hughes fungus in order to distinguish it from
the C. acutatum, to which the studies refer. Stevenson,
W R., Evans, G.E~, and Barksdale, T.H., P1. Dis. Rept.
62(11): 937 (1978) discloses the losses in fresh market
tomato crops produced by anthracnose disease caused by
C. coccodes (Wallr.) Hughes among others, and the develop-
ment of tomato cultivars with genetic resistance to the
disease.
Although many patents deal with the fungal
control of vegetation, none of them disclose the use of
Colletotrichum coccodes (Wallr.) Hughes for this treat-
ment. Such patents include the following:
U.S. Patents: 3,087,865 Drake et al
3,300,390 Tiner et al
3,308,038 Rhodes et al
3,150,062 Greenberg et al
3,357,895 Che-rry
3,361,555 Herschler
3,999,973 Templeton
4 9 061,488 Mann
4,162,912 Charudattan
4,390,360 walker
5~
In a broad aspect, -the present invention
relates to a process for controlling undesirable
vegetation by appling Colletotrichum cocco~es spores
onto the undesirable vegetation or onto the situs of
the undesirable vegetation.
The preferred composition which is used in
the process according to the invention comprises
Colletotrichum coccodes spores in an agricultural
carrier preferably having a spore concentration of
1 x 107 to 1 x 109 spores per ml of carrier.
The process according to the invention is
especially useful for the control of velvetleaf
(Abutilon theophrasti) which involves the application
of a spore suspension of a fungus, Colletotrichum
coccodes which results in a debilitating disease of
velvetleaf. The fungal spore application provides a
unique narrow spectrum herbicide for the control of a
single noxiousweed species, velvetleaf in soybeans,
corn and other crops.
Ihe preferred agricultural carrier comprises
water, with or without 1% by weight gelatin, the spores
being uniforrnly dispersed in the carrier.
The spore containing composition is preferably
applied at the cotyledon to 6-leaf stage of velvetleaf,
and under warm and moist conditions. m e composition may
be applied onto the leaf surface of the velvetleaf.
The organism, C. coccodes has been deposited
and can be obtained from the permanent collections of
~22~55
the Biosystematic Research Institute Agriculture Canada,
Ottawa, Canada where it has been deposited under an
unrestricted deposit as C. coccodes D~OM 183088.
The fungus produces necrotic spots (lesions)
on the leaves of velvetleaf which coalesce and cause
the death of leaves and stems. When the fungus infects
young velvetleaf plants, a devastating blight develops
and most diseased plants are killed~
C.coccodes can be grown on solid or in
liquid media for spore production. Media can be potato
dextrose, malt extract, V-8, or beef extract. For pro-
duction of larger quantities of spores liquid media is
used. For example:
Formula 1 - Modified Beef Extract
dextrose10.67g
nutrient broth 10.69g
peptone 0.44g
distilled water
(to make)1000 ml
Formula II - Richard's Modified V-8 Medium
sucrose 10.00g
KNO3 10.00g
g 4 2 2.50g
2 4 g
FeC13 0.02g
V-8 juice150 ml
distilled water
(to make)1000 ml
Liter flasks containing 500 ml of the liquid
media are inoculated with spores and incubated at 28C
with occasional agitation for 5 to 10 days. The contents
-- 5
of the flasks are then filtered to remove fungal mycelium.
The remaining liquid containing the Eungal spores is
centrifuged in a refrigerant centrifuge. The supernatant
is discarded and the spore concentrate is collected and
stored at 4C prior to application.
The spore concentrate is mixed with an agri-
culturally acceptable diluent or carrier for application
to the target weed, such as velvetleaf. The preferred
carrier is water containing 1% gelatin and the spore
concentrate is uniformly dispersed in the carrier. The
spore suspension (formulation) is sprayed onto the leaf
surface of the undesirable vegetation at a preferred
rate of 107 to 109 spores per m2 in 47 to 187 ml of
water per m2.
The velvetleaf isolate of C.coccodes does not
damage soybean, corn, and other crop plants and can be
used in these crops to control velvetleaf. me preferred
application is at the cotyledon to 6~1eaf stage of velvet-
leaf with the associated environmental conditions being
warm and moist. Repeat applications of the spore formul-
ation may be required and control is improved if the
growth of the associated crop is vigorous.
The invention will now be illus-trated by means
of the following non-limitating examples.
Example 1. Growth Chamber Studies
Cultures of C. coccodes are grown on malt
agar in petri dishes and when the cul-tures are sporu-
lating, small portions of the agar (about 1 cm3) are
removed and used for inoculation of culture flasks.
250 ml flasks containing 75 ml of modified beef extract
-- 6
media are aseptically inoculated with an agar cube.
Flasks are incubated on a rotary shaker (250 rpm) at
20 to 25C for 5 to 10 days. The cultures are then
filtered to remove mycelia, the remaining liquid con-
taining the spores is centrifuged in an IEC B20A
refrigerated centrifuge (870 rotor) at 7000 rpm for 20
minu-tes. The spore concentrate is resuspended in dis-
tilled water to reach a final spore concentration of
1 x 107 spores per ml. Velvetleaf plants growing
within controlled environment chambers are inoculated
by spraying the spore suspension onto the plant surface
until runoff occurs.
Optimum conditions for spore germination,
infection and disease development wexe determined.
Warm temperatures and free moisture are required for
spore germination and infection cf host plant material.
These processes occur best when temperatures are 24 to
30C and when a saturated atmosphere is maintained for
8 to 24 hours. After infection occurs higher tempera-
tures accelerate disease development with 30C night
and 35C day temperatures being optimum. All growth
stages tested (cotyledon to the 12-leaf stage) were
equally susceptible to infection.
Example 2. Field Studies
A. Spore preparation
Cultures of C coccodes are grown on PDA
plates for 1 to 2 weeks. When cultures are sporulating,
spores are aseptically suspended in 10 ml o-f sterile
water by swirling. Spore suspension is then transferred
to 1 L flasks containing 500 ml of Richard's Modified
V-8 medium. Cultures are then incubated at 28C for
-- 7
6-9 days with occasional swirling. Spores are harvested
by filtration through 2 layers of cheesecloth followed
by centrifugation in 250 ml bottles in a Beckman JA-14
rotor at 4,000 RPM for 15 minutes at 15C. Pellets of
spores are resuspended in distilled water and rinsed
twice with distilled water followed by centrifugation
each time. Spores are then stored at 4C. Yields
exceed 6 x 10 spores per liter of growth media used.
B. Formulation and application
Spores are resuspended in 1% gelatin concen-
tration and are adjusted to apply 107 or 109 spores
per m2 in 47, 94, or 187 ml per m2~
C. Fl d control for velvetleaf
When one application of spores is applied under
warm field conditions, velvetleaf biomass is reduced by
85% as compared to unsprayed control within 3 weeks after
spraying. The fungus spreads from infected foliage to
surviving foliage or new growth and suppresses velvet-
leaf growth for the rest of the growing season.
