Mycoherbicides

Fungal pathogens are considered to be the only group of microorganisms with potential for the classical biological control of weeds. These agents of living products control specific weeds in agriculture as effectively they could continue to survive on the weeds year after year over long periods and provide protection unlike the herbicides which are required to be applied season after season or year after year. These organisms have been known as Mycoherbicide indicates that a natural endemic pathogen might be rendered completely destructive to its weed host by applying a massive dose of inoculam at particular stage of weed growth. Since then many fungal herbicides have been developed.

Most popularly used Mycoherbicides

Mycoherbicide	Trade name	Country	Weed controlled
C. gloeosphoroides	Collego	USA	Aeschynomene sp.
C. gloeosphoroides	LUBOA2	China	Cuscuta sp
Cercospora rodmanii	ABG 5003	USA	Eichhornisc crassipes
C. gloeosphoroides	Biomal*	USA	Malva f. sp. malvae pusilla
Phytophthoro palmivora	Devine	USA	Malva f. sp. malvae pusilla
Alternaria cassiae	CASET*	USA	Cassia obustifolia

Characteristics of good Mycoherbicide

They should be

• Culturable in artificial media
• Capable of abundant spore production
• Stable in storage
• Genetically stable
• Effective under field conditions
• Tolerant to variations in temperature
• Compatible with other chemicals/cultural practices.

Most of the recently developed mycoherbicides were found to satisfy these requirements to a great extent. Devine is a liquid formulation consisting of chylamidospores of a pathotype Phytophthora palmivora and is used as a post-emergent mycoherbicide against Morrenia odorata (milk weed vine/strangler vine). Nearly 100 per cent control of the weed is usually obtained and control lasts for two years. Collego is wettable powder formulation of Collectotrichum gloeosporoids f. Sp. aeschenomene and is used for controlling Northern joint with (Aschenomene virginica) in rice and soybean. It is applied aerially or with land based equipments when the weeds have just emerged. Control reported was as high as 90 per cent.

The fungus Cercospera rodamanii has been developed as Mycoherbicide for the control of Eichhornia crassipes. Similarly many pathogens possessing mycoherbicidal properties have been identified. The pathogens derived mycoherbicides normally initiate disease in specific weed population and kill the weeds within 3-5 weeks.

 

Fungi possessing mycoherbicidal activity

Pathogen	Weed controlled	Country
Collectotrichrm furarioides	Asclepias seriaea (Comman milk weed)	USA
Alternaria Sp.	Crisium avense (Canana thistile)	USA
Phomopsis convolvulus	Convolvulus arvenais (field bind weed)	USA
Alternaria crassa	Datura stramonium	USA
Bipolaris halepense	Sorghum halepense (Johnson grass)	USA
Collectrotrichom oriculare	Xanthium spinosum (Spiny cocklebur)	USA
Alternaria helianthi	X. stramarium	USA

The introduction of exotic rust (Puccinia chondrillus) fungi has proved to be successful in the control of skeleton weed (Condrilla juncia) in the wheat belt of Australia.

Parthenium hysterophorus, called as false rageweed/congress weed, is reported to cause allergic responses like respiratory mulfunction and dimities in human. The rust pathogen, Puccinnia abrupta var. parthinicola capable of controlling Parthenium hysterophorus, has also been reported. Mycoherbicides could be developed for integrated use in niche markets. However, efficacy and practicability will be the key determinants of whether or not this technology finds commercial sponsor and user acceptance. It is prudent to speculate that use of Mycoherbicides as biological control will continue to be small but significant component of weed control technology in the future.