Res. J. Agric. & Biol. Sci., 3(6): 979-982, 2007
register for use. W ith the increasing concern about the vectors of the pathogens which if controlled will reduce
use of pesticides in agriculture, there is the need to incidence and severity of the bacterial diseases [2 0 ,6 ].
develop alternative plant protection strategies [1 0 ]. Amusa [2 ] reported controlling the cassava green spider
Some pesticides have lost their effectiveness because of m i t e M o n o n y c h e llu s ta n a jo a B o n d a r .( A c a r i :
the development of resistant pathogens [2 ]. The perceived Tetranychdae) using Typhlodromalus. aripo (Acari:
negative effects of fungicides bactricides and pesticides phytoseiidae) significantly reduced the severity of
on agricultural land and water, and their possible cassava bacterial disease in the transitional forest zone.
toxicity to man and animals, has resulted in the The knowledge of the fact that microbial toxins like
consideration of more environmentally friendly control any other toxins can be inactivated or detoxified has
measures. Biological control of plant diseases lacks been exploited in plant disease (involving toxic
most of the limitations of chemical pesticides. metabolites) management based on the fact that
However, biological control of plant diseases has reduction in the toxicity of metabolite produced by
been used in the management of plant pathogens plant pathogens will confer resistance or tolerance on
generally [1 2 ,1 3 ,1 4 ]as been said about its potential in the the host plant. Microorganisms form an exotic source
control of bacterial diseases of crops [1 5 ] nce this of enzymes, which are capable of inactivating synthetic
paper present the present status of the biological c h e m ic a ls tha t a re po te ntia lly p h yto to x i c [ 2 1 ]
control of bacterial diseases of plants in Nigeria: detoxification of pathogen toxin combined with
Problems and Prospects biocontrol efficacy has been well established with
Pantoea dispersa, which offered an excellent biocontrol
Biological Control of Plant Diseases: Biological against sugarcane leaf scald disease caused by
control of disease is the employment of natural Xanthom onas alblineans [ 2 2 ] . T his host–pathogen
enemies of pests or pathogens in the eradication or interaction, the antagonistic bacterium detoxified
control of their population. It could also be inform of albicidin toxin produced by the pathogen.
induction of plant resistance using non-pathogenic or The most recent methods of managing plant
incompatible micro-organisms. Over the years farmers diseases use pathogen produces toxic metabolites which
in Nigeria has employed the use of composted organic is responsible for disease condition in plants in Nigeria
materials such as plant debris and animal manure to is the use of toxic metabolites of the pathogen in
add nutrient to the soil in other to increase it fertility. screening for the resistance [2 3 ,2 4 ]. There are a number of
According to Muhammad et al [1 6 ] use of composted instances [2 5 ,2 6 ,2 7 ] where the use of culture filtrate and
organic materials do not only improves plant growth extra-cellular enzymes have proved to be more durable
but also makes them less prone to infections by soil in their effects and these have the advantage of not
inhabiting pathogens. Krause et al., [1 5 ] ported that requiring repeated periodic applications as in the case
Rhizobacteria from composted suppress the severity of with chemical fungicides. However, much research
bacteria leaf spot of Radish. work has been done with regards to fungal disease
However, this biological control method only control but research has just commenced on the
suffices for backyard farming where household waste management of bacteria diseases using this methods.
(composts) is used as manures. Resulting from success
recorded from the backyard farming activities, several Problems: In recent years, there has been substantial
researches were initiated at research centers and interest in the biological control of plant pathogens
Universities on the use of composted agricultural and especially bacteria world over [1 2 ,2 8 ,1 3 ,1 4 ,2 9 ,3 0 ,1 5 ]. W hile
industrial wastes to suppress plant diseases of economic biological control agents have been introduced
plants [1 6 ,1 7 ,1 8 ,1 9 ]. successfully into commercial horticulture for control of
The aim of these researches was to identify the crown gall[3 1 ], caused by Agrobacterium tumefaciens,
microbes responsible for the disease suppression and and fire blight of pear [3 2 ], caused by Erwinia
subsequent use of such in biocontrol. However, despite amylovora, and other bacterial diseases of commercial
the effort, the result only gave lights to the use of crops has been effectively managed with biological
some bacterial such as Bacillus cereus, Bacillus controlling agents. Biological control of bacterial
subtilis, Pseudomonas spp and some fungus such as diseases of crops has not been successvely implimented
Trichoderma spp and Gliocadium spp in the control of in Nigeria. Reason for this emmanted from lack of
fungal diseases [1 6 ,1 7 ,1 8 ,1 9 ]. adequate fund to conduct research on biological control
Bacterial diseases has continued to cause series of of plant diseases.W here funds were made available, it
set back to farming in Nigeria, efforts to control is only for the biocontrol of invertebrate pests (insects).
bacterial diseases of some crops has been very difficult. More over research is still being single handedly
However, since synthetic chemicals are not available funded by the Government while Industries and
and biological agents have not been fully identified, Multinationals like oil companies do not support
Research efforts was towards the identification of research in agriculture.
Res. J. Agric. & Biol. Sci., 3(6): 979-982, 2007
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