Fungi and bacteria are considered the most effective biological control agents against nematodes. They act directly through antagonism of plant-parasitic nematodes or indirectly by producing compounds that promote plant growth or induce resistance. Common fungal control agents include Trichoderma, Catenaria, and Aspergillus which repel or kill nematodes through various mechanisms. Bacterial control agents like Pseudomonas, Agrobacteria, and Pasteuria also antagonize nematodes through toxins, antibiotics, or by attaching and restricting movement. Nematode suppressive soils naturally limit nematode populations through parasitism and antibiosis from biological control agents, though soil properties and plant species can influence the level of suppression

1. BIOLOGICAL CONTROL AGENTS
AGAINST NEMATODES AND
NEMATODE SUPRESSIVE SOILS

2. 2. Biological control agents(BCAs)
2.1 Their General Categorization And Effect
• Fungi and bacteria currently considered the most effective BCAs
• Others BCAs like viruses and predaceous mites are less effective
• Challenges in testing BCAs’ benefits:
Mass culture, formulation, application method and interaction with
seed and media
• Their mode of action is ether directly or indirectly
• Direct antagonism against the PPNs or indirectly promoting hormones
• BCAs and their metabolites are responsible for PPN management

3. 2.1 Their General Categorization And Effect
Mechanism of BCAs action against PPNs:
i. Produce plant growth promotors
ii. Produce active compounds ang growth hormones
iii. Produce lytic enzymes and antibiotics to suppress pathogens
iv. BCAs can prime for PPN resistance
v. Interact with roots to prime plants against RKN infection
vi. Trap nematodes
vii. Are parasite of nematode at all stages

4. Fungal control
• Fungal BCAs include: Trichoderma, Catenaria, Aspergillus and
Pochonia
• Endophytic nematodes colonize roots and enhance plant defense
• They repel the juveniles stage 2 away from roots
• Retard PPN development
• Lower PPN’s fecundity
• Trichoderma spp. kill RKN in the root system
• Pochonia induce resistance against M. incognita
• They also target cyst nematode Globodera spp.

5. Bacterial control
• Bacterial species of genera Pseudomonas, Agrobacteria, Rhizobium,
Arthrobacter and Pasteuria control PPNs
• Their mode of actions are antagonism, antibiotic production and
induced resistance
• B. thuringesis produces toxic particles of cry protein while B cereus
raise secretion of repellent substances
• Pasteuria spp. Spores attach to surface of the nematode. The germ
tube grows into the nematodes body
• The spores restrict nematode movement and the female produces few
or no eggs
• Their endospore is resistant to drying, heat and shearing hence a good
biocontrol

6. Nematode suppressive soils
• They are soils in which pathogens can not persist or cause disease
• Biological activity of such soils is shown when its suppressiveness is
removed by biocides, reduce multiplication of nematodes and is heat
sensitive
• Parasitism and antibiosis by BCAs were suggested in repressive soils
• Soil suppression acts against certain PPN species
• Soil properties and plant species influenced level of suppression
• Plant genotype control magnitude of BCA induced resistance
• Soil sterilization affects PPN and other biological organisms