Bioherbicides are biologically based agents for controlling weeds. They provide an environmentally friendly alternative to chemical herbicides which can pollute the environment and affect human health. The first commercial bioherbicides appeared in the 1980s. They included Devine, a mycoherbicide that controls the weed Morrenia odorata through a pathogenic fungus. Since then, many microbes have been screened for their ability to act as bioherbicides. While bioherbicides show promise, challenges remain in developing agents that are effective, host-specific, and genetically stable under field conditions. Improved formulation and targeting of specific weed species could help increase their use in agriculture as an alternative to chemical herbicides

1. PRESENTED BY:VIKRANT MEHTA
ROLL NO. : 301105022

2. A bioherbicide is a biologically based control
agent for weed. In irrigated agriculture, weed
control through chemical herbicides, creates
spray drift hazards and adversely affects the
environment. Besides, pesticide residues
(herbicides) in food commodities, directly or
indirectly affect human health. These lead to the
search for an alternate method of weed
management, which is eco-friendly.

3. Commercial bioherbicides first appeared in the
market in USA in early 1980s with the release of
the products Devine ,Collego and Biomal.
Devine, developed by Abbott Laboratories,USA,
the first mycoherbicide derived from fungi
(Phytophthora palmivora Butl.), is a facultative
parasite that produces lethal root and collar rot
of its host plant Morrenia odorata (stangler
wine)and persists in soil saprophytically for
extended periods of residual control. It was the
first product to be fully registered as a
mycoherbicide.

4. The initiative for using pathogens, phytotoxins from
pathogens, and other microorganisms as biological
weed-control agents began about three decades ago.
Since then, numerous microbes have been screened for
phytotoxic potential, and several dozens evaluated as
bioherbicides as reported by various researchers and
summarized (e.g., Hoagland, 1990, 2001; TeBeest,
1991). Due to the interest in this area, many other weed
pathogens and phytotoxins (from pathogenic and non-
pathogenic microorganisms) will be discovered that
possess bioherbicidal activity. Most bioherbicides have
been targeted toward agronomic weeds, but these
agents may also be useful to control weeds in
nonagronomic areas (recreational areas, forests, rights-

5.  Approach
 Classical – agent selection, inoculation, self-
perpetuating, long term protection.
 Inundative – mass production, application at high
inoculum levels over a localized area, short term,
repeated application.
 Augmentation – re-establishment of a classical agent.
 Classes
 Mycoherbicide – fungal pathogen
 Bioherbicide – fungi and bacteria

6.  Bruckart and Dowler, 1986: rust fungi are
effective biological control agents - USDA
 Templeton, 1988: predicted widespread
adoption can be achieved
 Strobel, 1991: predicted that bioherbicide
use will realize a tremendous increase in
agriculture

7.  Demand for decreased use of pesticides
 Large areas where herbicide application not
possible or not cost effective
 Damage to the environment
 Contamination of our water supply
 High yield losses still occur
 $619 million in vegetable, $441 million in fruit and
nut crops in the US

8.  Produce abundant and durable inoculum
in culture
 Be target specific
 Be genetically stable
 Be capable of killing a significant portion
of the weed population under a variety of
environmental conditions (weed densities)
Boyetchko, 1997

9.  Herbicide resistant weed population
 Detrimental effects on non target organisms
 Native plants

10. FUNGI
BACTERIA
VIRUS

11. Trait Bacteria Fungi Virus
Culture Easy Easy Host
Specificity Excellent Good Excellent
Field Performance Variable Variable Unknown
Formulation Variable Excellent Unknown
Effectiveness Variable Variable Excellent
Genetic stability High Medium Unknown

12.  Pathogens of plant (i.e. bioherbicides) are
generally host specific.
 Cherrington, C. A. and L. F. Elliott. 1987.
Incidence of inhibitory pseudomonads in the
Pacific Northwest. Plant and Soil 101:159-
165.
 Isolated pseudomonads from downy brome, winter
barley, winter wheat, pea, lentil roots
 Found 106 - 108 CFU per gram dry weight
 Found isolates that reduced downy brome root
growth but not wheat root growth

13.  Kennedy, A. C., L. F.
Elliott, F. L. Young and C.
L. Douglas. 1991.
Rhizobacteria suppressive to
the weed downy brome.
Soil Sci. Soc. Am. J. 55:722-
727
 1000 isolates, 18 inhibitory to
downy brome and not wheat
 Reduced DB population up to
30%
 Reduced DB shoot weight up
to 42%
 Increased winter wheat yields
35%
 Both in greenhouse and in
field trials in eastern
Washington

14. Many fungi have been shown to exhibit broad
spectrum weed control ranges.

15. WEED PATHOGEN REFERENCE
1. Velvet Colletotrichum Hodgson et al.,
leaf coccodes, 1988
Fusarium lateritium Walker, 1981
2.Wild oat Septoria tritici Madariaga and
Scharen, 1985
3.Water Alternaria eichhorniae Shabana, 1987
hyacinth
4.Sickle pod Pseudocercospora Hofmeister and
nigricans Charudattan,
1987
5.Barnyard Cochliobolus lunatus Scheepens, 1987
grass

16. PATHOGEN WEED SPECIES OR REFERNCE
FAMILY
Alternaria cassiae Sicklepod Boyette, 1988;
Coffee senna Charudattan et
Showy crotalaria al., 1986; Walker, 1982,
1983
Amphobotrys ricini Members of Holcomb et al., 1989;
Euphorbiaceae Whitney
and Taber, 1986
Colletotrichum Members of Daniel et al., 1973;
gloeosporioides Leguminosae, Mortensen
Malvaceae, and Makowski, 1997
Convolvulaceae
(dodders)
Myrothecium Sicklepod; various Walker and Tilley, 1997
verrucaria species of
other plant families

17.  Xanthomonas campestris pv. poannua -
postemergence activity on annual bluegrass
in bermudagrass lawns (Johnson, 1994:
Johnson, Wyse, Jones, 1996).
 Pseudomonas syringae pv. tagetis - Canada
thistle in soybean (Johnson, Wyse, Jones,
1996).

18. In most instances the potential risks associated with the
use of Bioherbicides may includes certain concerns
such as:-
 worker exposure and safety
 Plant host range
 effects to nontarget organisms
(competition/displacement of beneficial
microbes in the community)
 production of chemicals that are persistent or
toxic to mammalian systems

19. Puccinia melampodii, a rust fungus isolated in Mexico, was approved
for release in Australia in an integrated strategy to manage
the highly allergenic weed, Parthenium hysterophorus, even though
it could also sporulate on several marigold and sunflower cultivars
(Evans, 2000). The Australian Quarantine and Plant Inspection
Service concluded that the actual and potential hazards involved
in not attempting to control this weed were significantly greater
than the perceived risks to nontarget plants.
One of the major hurdles in the use of bioherbicides is the risk
associates with that of secreted metabolites.

20. Fungi secrete a wide range of metabolites, some of which
are important medicines or research tools (Vey et al.,
2001). Some of these metabolites are highly toxic
(fumonisins, ochratoxins, patulin, zearalenone) or
carcinogenic (moniliformin, aflatoxin). A large amount
of data has accumulated on mycotoxin contamination
of foodstuffs and the risk these metabolites (mostly
from saprophytic fungi) pose to human and animal
health (Abramson, 1998). In contrast less is known
about metabolites from fungal biocontrol agents,
particularly those from commercialized
mycoherbicides, mycoinsecticides, and
mycoparasiticides (Strasser et al., 2000; Vey et al.,
2001).

21. There are two particular areas where there appears to
be cause for optimism in the mycoherbicides field;
the use of virulent pathogens for the treatment of the
cut stumps of weedy trees in forest ecosystems, and
weed control targeted at the leisure industry (Evans
et al., 2001). A recent example of the former concerns
using the silver leaf fungus, Chondrostereum
purpureum, for control of black cherry (Prunus
serotina: Rosaceae); an invasive North American
species which is a serious threat to conifer
plantations, as well as to native woodlands in the
Netherlands (De Jong et al., 1990)

22. The bioherbicide, Biochons, is currently being
marketed by Koppert Biological systems as an
environmentally friendly solution to
undesirable tree regrowth. The use of this
pathogen for management of weedy, endemic,
deciduous trees in conifer plantations and
amenity areas is also being evaluated in
Canada(Prasad,1994).

23. In complete contrast, advanced technology and large
companies are currently involved in the development of
bioherbicides in Japan, not only in crop protection but
also in the highly lucrative leisure industry. The most
troublesome weed in golf courses is annual bluegrass
(Poa annua) and chemical herbicides are either nonselective
or now considered to be environmentally
undesirable. A highly specific, bacterial endophyte,
Xanthomonas campestris pv. poae, has recently (1997)
been registered under the name Campericos, and
constitutes the first bacterial herbicide to reach the
commercial market (Imaizumi and Fujimori, 1998).

24. There is no doubt that formulation has played a key
role in the marketing of bioherbicides, such as
Campericos, in order to overcome problems with
storage,establishment and efficacy in the field.
Essentially formulation is mixing the active
ingredient, in this casethe biological propagule,
with a carrier or solvent andother adjuvants in
order to develop a product which can be stored,
for at least 1 year, effectively applied to the target
weed with safe and consistent results.

25. The development of bioherbicides are less expensive than
for chemical herbicides (Templeton et al., 1986). For
example, the cost of developing COLLEGO was
approximately $1.5 million in research and development
in the late 1970s and early 1980s (Heiny and Templeton,
1993), and the cost of developing BIOMAL was estimated
to be about $2.6 million(J.R. Cross, Philom Bios, personal
communication).These development costs, compared to
the $30 millionore more to discover and develop a
chemical herbicide, make bioherbicide development quite
favourable (Heiny and Templeton, 1993).

26. The role of biomicrobial herbicides in agriculture,
however, is still problematic and insignificant.
Nevertheless, because of pressures to reduce the
reliance on chemical herbicides, bioherbicides could
make a significant contribution to weed control. In
the future, once the well-documented constraints
have been overcome, particularly through improved
target selection, formulation and marketing.

27. Prospects for the development and utilization of bioherbicide technology for major
rice weeds are very good. Work in this area is preliminary for the most part, but
virulent pathogens of some potential weed targets have been identified and initial
laboratory and field results are encouraging. Increased activity in basic and applied
science and in biotechnology have a definite role to play in development,
implementation, and advancement of this weed control strategy in tropical and
subtropical regions. Virulence, efficacy, fermentation, formulation, and application
are aspects of prime importance. Industry must become more involved in small niche
markets, and techniques must be developed for subsistence farmers as well as modern
ones. There is likely to be increased pressure from public and governmental bodies to
reduce the use of chemical herbicides. We are challenged to find acceptable, effective
complementary weed control tactics.

28.  Advances in bioherbicides development—an
overview: R. Mohan Babu, , A. Sajeenaa, K.
Seetharamana, P. Vidhyasekarana, P.
Rangasamy, M. Som Prakash, A. Senthil Raja,
K.R. Biji
 BIOHERBICIDES: RESEARCH AND RISKS-
ROBERT E. HOAGLAND, C. DOUGLAS
BOYETTE, and MARK A. WEAVER
Southern Weed Science Research Unit, USDA-
ARS, Stoneville, Mississippi, USA

29. HAMED K. ABBAS Crop Genetics and Production
Research Unit, USDA-ARS,Stoneville, Mississippi, USA.
•CURRENT STATUS OF BIOHERBICIDE
DEVELOPMENT AND PROSPECTS FOR RICE IN ASIA
- Alan K. Watson.
Plant Science Department, McGill University, 21,111
Lakeshore Road,Canada.
•Boyetchko, S. M. 1997. Principles of biological weed
control with microorganisms. HortSci. 32(2):201- 205.
•Cherrington, C. A. and L. F. Elliott. 1987. Incidence of
inhibitory pseudomonads in the Pacific Northwest. Plant
and Soil 101:159-165.

30.  Kennedy, A. C., L. F. Elliott, F. L. Young and C.
L. Douglas. 1991. Rhizobacteria suppressive to
the weed downy brome. Soil Sci. Soc. Am. J.
55:722-727
 Heiny, D.K., Templeton, G.E., 1993. Economic
comparisons of mycoherbicides to conventional
herbicides. In: Altman, J. (Ed.),Pesticide
Interactions in Crop Production. CRC Press,
Boca Raton, FL, pp. 395–408.

31. Bayot, R., A.K. Watson, and K. Moody.
1992. Control of paddy and aquatic weeds by
pathogeninPhilippinesIn:
IntegratedManagement of Paddy and Aquatic
Weeds and Prospects for Biological Control.
Food and Fertilizer Technology
Center, Taipei, Taiwan.