Plant protecting and regulating compositions – Plant growth regulating compositions – Micro-organisms or from micro-organisms
Reexamination Certificate
1999-03-22
2001-07-24
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Micro-organisms or from micro-organisms
Reexamination Certificate
active
06265347
ABSTRACT:
BACKGROUND OF THE INVENTION
Weeds are a tremendous problem for farmers and growers throughout the world. It has been estimated that about 41% of the cost of plant protection is for the control of weeds. Herbicides are applied to more acres than fungicides and insecticides combined. Weeds act as alternate hosts for insects, fungi, bacteria, and viruses. They affect man, not only by competing with crop plants, but by poisoning range animals, interfering with right-of-ways and roadways, decreasing forest production, and marring landscapes.
Weeds compete with crops for moisture, light, and nutrients and can inhibit crop growth and reduce yields. Competition can be particularly detrimental in tree crops when young trees are being established. In citrus and other tree crops the most problematic weeds are some annual and perennial grass weeds, which are also among the world's worst weeds in many crops worldwide. Some notable examples are: large crabgrass (
Digitaria sanguinalis
[L.] Scop.), crowfootgrass (
Dactyloctenium aegyptium
[L.] Willd.), johnsongrass (
Sorghum halepense
[L.] Pers.), bermudagrass (
Cynodon dactylon
[L.] Pers.), guineagrass (
Panicum maximum
Jacq.), southern sandbur (
Cenchrus echinatus
L.), Texas panicum (
Panicum texanum
Buckl.), and yellow foxtail (
Setaria glauca
[L.] Beauv.).
The use of chemical pesticides in agriculture is currently a major concern in the U.S. Because herbicides are so widely used in agriculture, and because they are often applied directly to the soil, the potential for their movement into groundwater by leaching is perhaps greater than any other pesticide. Other inadequacies of chemical controls include lack of residual control, injury to non-target organisms, undesirable residues in harvested products, and carryover in subsequent crops.
Therefore, the use of bioherbicides is becoming an increasingly important alternative to chemical herbicides. This importance is exemplified by several patents which have been issued for bioherbicides and their use. Some of these patents, by way of illustration, are as follows: U.S. Pat. No. 3,849,104 (control of northern jointvetch with
Colletotrichum gloeosporioides
Penz.
aeschynomene
); U.S. Pat. No. 3,999,973 (control of prickly sida [teaweed] and other weeds with
Colletotrichum malvarum
); U.S. Pat. No. 4,162,912 (control of milkweed vine with
Araujia mosaic
virus); U.S. Pat. No. 4,626,271 (cyanobacterin herbicide); U.S. Pat. No. 4,915,726 (biological control of dodder); U.S. Pat. No. 5,256,627 (control of nutsedge using Curvularia and Fusarium fungi).
The bioherbicide technology involves mass production, formulation, and inundative application of highly virulent, host-specific plant pathogenic microorganisms at a time conducive for disease development on a population of weeds. This technology has wide commercial applications in weed management. The major challenges to the bioherbicide technology are host-specificity (which typically limits use to one weed per pathogen) and inadequate weed control.
BRIEF SUMMARY OF THE INVENTION
The subject invention concerns materials and methods useful in weed control. More specifically, the subject invention concerns the use of a combination of fungal pathogen isolates to provide enhanced control of multiple weed species. In a specific embodiment, the subject invention provides materials useful in the control of pigweed, sicklepod, and showy crotalaria.
In a preferred embodiment specifically exemplified herein, bioherbicidal control of pigweed (
Amaranthus hybridus
L.), sicklepod (
Senna obtusifolia
[L.] Irwin & Barneby), and showy crotalaria (
Crotalaria spectabilis
Roth.) was achieved using a multiple pathogen strategy consisting of four pathogens applied in a single postemergent spray. The pathogens used were
Phomopsis amaranthicola
sp. nov. Rosskopf et al., (PA, pigweed pathogen), Alternaria cassiae Jurair & Khan (AC, major host, sicklepod; alternative host, showy crotalaria),
Colletotrichum dematium
(Pers.ex. Fr.) Grove f.sp crotalariae and
Fusarium udum
Butler f.sp. crotalariae (Kulkarni) Subramanian (CD and FU: showy crotalaria pathogens). The mixture of these pathogens was able to control all three weed species.
The practice of the subject invention typically involves the use of a composition comprising spores from the above fungal pathogens in association with an agricultural carrier wherein the spores are in a concentration of from about 1×10
4
spores/ml of carrier to about 1×10
9
spores/ml of carrier. The concentrated spore formulation can be adapted for distribution such that the spores germinate and infect target weeds.
In a further embodiment, the subject invention discloses the fungal pathogens
Drechslera gigantea, Exserohilum rostratum,
and
Exserohilum longirostratum.
These fungal pathogens can be applied alone or in a mixture to control target grass weeds. Also, compositions comprising spores from these novel fungal pathogens can be used as described herein.
The possibility of controlling several weeds, especially grasses, by a mixture of multiple pathogens, each of which is effective against some but not all hosts, is a novel approach that has not been previously demonstrated with bioherbicides. So far, the emphasis has been on the use of a single, host-specific pathogen to control a single weed. In accordance with the subject invention it is not only possible to control the specific weed hosts of individual pathogens, but also to increase the spectrum of weeds controlled by using the mixture. Such broad-spectrum activity, resulting from advantageous interaction among the pathogens, is a key aspect of this approach. Use of formulations that promote and augment the efficacy of the pathogens, such as an emulsion or other carrier, is another aspect of the subject invention.
DETAILED DISCLOSURE OF THE INVENTION
The subject invention provides a method for controlling multiple weeds using a mixture of fungal plant pathogens. The materials and methods of the subject invention can be used to enhance the efficacy of bioherbicides by increasing the spectrum of weeds controlled and the level of control (i.e., broad-spectrum control and high level of efficacy).
In a preferred embodiment, the compositions of the subject invention comprise three or more fungal isolates. Advantageously, the composition has activity against multiple weeds.
The fungal isolates can be combined according to the subject invention and applied to target weeds. Generally, the application is done by use of the spore form of the fungal pathogen. The fungi of the subject invention can be grown on solid or in liquid media. Solid media that can be used include water agar, potato dextrose agar, V-8 agar, and string bean agar (strained extract of macerated string beans solidified in agar). Spores can be produced on solid V-8 medium exposed to fluorescent light. Specifically, solid media can be, for example, water agar, potato dextrose agar (Difco), lima bean agar (Difco), corn meal agar (Difco), potato-carrot agar (Tuite 19), or Desmodium agar (blend 10 g Desmodium plant parts or plant extracts in 1000 ml water and solidify with 20 g agar).
For large scale production in fermentation tanks, a liquid medium is typically used, for example:
TABLE 1
Formula I: - Modified Richard's Solution - V-8*
Sucrose
50
g
Potassium nitrate
10
g
Potassium phosphate, monobasic
5.0
g
Magnesium sulfate · 7H
2
O
2.50
g
Ferric chloride
0.02
g
V-8 juice
15
ml
Distilled water to make
1000
ml
*Trademark, The Campbell Soup Company for mixed vegetable juices.
Formula II: Modified Richard's Solution-Distillers Solubles. Same as Formula I above but substitute 15 g Distillers solubles for V-8 juice.
Formula III: Modified Richard's Solution-Brewersyeast. Same as Formula I above but substitute 15 g brewers yeast for V-8 juice.
Formula IV: Modified Richard's Solution-Torula Yeast. Same as Formula I above but substitute 16 g torula yeast for V-8 juice.
Formula V: Oatmeal solution-4%+2% s
Chandramohan Sankaranarayanaiyer
Charudattan Raghavan
Clardy S. Mark
Saliwanchik Lloyd & Saliwanchik
University of Florida
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