Biological control of purple loosestrife

Details Biological control of purple loosestrife Biological control of purple loosestrife

1999-01-29

2001-07-31

Yucel, Remy (Department: 1636)

Chemistry: molecular biology and microbiology

Micro-organism, per se ; compositions thereof; proces of...

Fungi

C435S243000

Reexamination Certificate

active

06268203

ABSTRACT:

BACKGROUND OF THE INVENTION
Purple loosestrife (
Lythrum salicaria
) is an aggressive invasive weed that forms uniform stands that replace diversified native flora, including important waterfowl food plants. Purple loosestrife forms dense stands where it destroys wetlands by reducing water flow and drying out the soil. Many wetlands in North America have major infestations of purple loosestrife. It has no natural enemies on the continent, neither native herbivores nor pathogens, that presently suppress invasive populations of purple loosestrife. Further, its growth is so dense that most wetland wildlife cannot use it as habitat. Moreover, it is not a preferred food for native animals in North America.
A number of characteristics have enabled purple loosestrife to become a problem. A single, mature plant can produce 2.5-million seeds annually. Established plants grow more than 2 meters tall with 30-50 stems forming wide crowns that dominate a plant canopy. Also, a strong rootstock serves as a storage organ providing resources for spring growth and regrowth if the above-ground shoots are destroyed. R. F. Nyvall,
Mycologia,
87:501-506 (1995).
The U.S. Department of Natural Resources as well as most states in the U.S. have declared it a noxious weed and require that it be controlled. It is also on the Noxious Weed List in Alberta, Manitoba, and numerous municipalities in Canada. Governmental agencies have been trying to control the spread of purple loosestrife by various means including cutting it, pulling it out, spraying it with herbicides and burning it. Some of the control methods make the situation worse by killing surrounding plants so the purple loosestrife seedlings have no competition. For example, the seemingly obvious solution of pulling it up by the roots does not work. The whole root mass must be removed, causing extensive disturbance to the soil, and creating the very habitat in which this plant thrives. Also, all of the plant must be removed, because it can regenerate from a tiny piece of crown, stalk or leaf buds. Chemical herbicides such as Roundup® or Rodeo® are not desirable because they kill essentially all the wetland plants since they are not selective for purple loosestrife.
In addition to there not being acceptable chemical herbicides for purple loosestrife, environmental concerns make biological control a potentially attractive alternative to traditional methods of weed control. Biological control of purple loosestrife began in Germany in the 1960's. It was found that certain species of beetles (
Galerucella calmariensis, G. pusilla,
and
Hylobius transversovittatus
) could help control the spread of the weed. In 1991, the Canadian government approved the introduction of these predators of purple loosestrife as biological control agents. In 1992, the United States Department of Agriculture approved the release of these beetles as biological control agents in the U.S.
Unfortunately, it takes quite a long time (3-5 years) for these beetles to become established in an area, if they become established at all. Further, even if they become established in an area, they may not significantly impact purple loosestrife for at least 2-3 years because the plant is so resilient. Moreover, the beetles do not always kill the crown of the plant, so they may not consistently prevent seed production by the plants. The seed bank of purple loosestrife is viable for approximately nine years.
To date, no mycoherbicides have been developed from pathogens of purple loosestrife either in Europe or North America. In fact, disease symptoms are rarely observed in Europe and no pathogens have been isolated from purple loosestrife in Europe with the exception of a nematode Meloidogyne sp. reported to feed on roots in the former USSR. R. F. Nyvall,
Mycologia,
87:501-506 (1995).
Thus, there remains a continuing need for a means to safely and effectively control the spread of purple loosestrife. There is further a long-felt, unresolved need to produce an herbicidal composition that can be sprayed, or similarly administered, onto purple loosestrife or other noxious weeds to selectively control the weeds in environments with mixed populations of useful plants, such as in a protected wetland.
SUMMARY OF THE INVENTION
The present invention provides a novel isolated and purified culture deposit ATCC no. PTA-223 that effects control of purple loosestrife (
Lythrum salicaria
). The culture may be isolated from cultivated plant material of the genus Lythrum. The cultivated plant material may be living plant tissue, dead plant residue or soil. The culture was deposited Jun. 15, 1999 in the American Type Culture Collection, 10801 University Blvd., Manassas, Va. 20110-2209, under the provision of the Budapest Treaty, and assigned ATCC accession number PTA-223. The culture may be mixed with or impregnated in an acceptable carrier to make an herbicidal composition. The carrier may be diatomaceous earth, alginate or clay. Further, the carrier may be a liquid. The carrier may also be an adjuvant, or alternatively, at least one adjuvant may be added to the herbicidal composition. The adjuvant may be an effective plant-tissue penetrating adjuvant. It may be water-miscible or water-dispersable. The adjuvant may be methylated seed oil. The culture of the present invention may be in the spore form. The effective amount of the culture is in the range of 1×10
2
to 1×10
12
spores per ml. It may be in the range of 10
4
to 10
9
spores per ml, or in the range of 10
5
to 10
8
spores per ml. The herbicidal composition may contain a germination activator, i.e., a compound or mixture of compounds that enhance spore generation. Examples of germination activators include, but are not limited to, monosaccharides, disaccharides, polysaccharides, amino acids, peptides, peptones, proteins, inorganic salts, and other solutes.
The present invention also provides a method for controlling purple loosestrife comprising applying an herbicidally effective amount of the above-described herbicidal composition onto a target purple loosestrife plant or onto the situs of a target plant (i.e., the area around the target plant). The herbicidal composition is applied at least once, but may be applied a plurality of times. Further, the method provides for the controlling of the target plant for multiple growing seasons.
DETAILED DESCRIPTION OF THE INVENTION
Lythrum cultivars were obtained from the Morden Research Station in Morden, Manitoba and independently from Behnke Nurseries in Maryland. These cultivars were propagated in the greenhouse and grown together with other cultivars and weedy lythrum in a loosestrife nursery. One of the inventors observed that some of the cultivars growing in the greenhouse were dying from what appeared to be a plant disease. The sick plants would begin to wilt, and then completely dry out and die. Most of the sick plants were of the cultivar, “Morden Gleam”, which is a hybrid created from crossing the cultivar “Morden Pink” (
Lythrum virgatum
) with the native, winged loosestrife (
L. alatum
). The two species of Lythrum are different species from the weedy purple loosestrife (
L. salicaria
). Although the
L. virgatum
and
L. alatum
are distinct species, they are closely related and will occasionally cross to produce hybrids, as occurred in the creation of the hybrids “Morden Rose” and “Morden Gleam.” Artificial crosses, however, made between the two species have rarely produced seed that will germinate.
The inventor gave some of the infected plant material to one of the other inventors, who isolated the pathogen from the cultivars. The inventor then took some of the original isolate, put it into culture and then sprayed it onto weedy purple loosestrife plants (
Lythrum salicaria
). The inventor was able to reisolate the fungal pathogen from the weedy purple loosestrife plants. It was also observed that weedy purple loosestrife plants developed the same symptoms as in the “Morden Gleam” plants. Therefore, even though fungal pathogen was initially isolated from a hybrid cross

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