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GRIFA ETC
Università degli studi Milano – Bicocca
16-17 Ottobre 2002
Entomopathogenic nematodes in
biological control: reality and prospective
Manuele Ricci e Adriano Ragni
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Entomopathogenic Nematodes
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Taxonomy
 Phylum
 Class
 Order
 Sub-order
 Super-family
 Family
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Nematoda
Secernentea
Rhabditida
Rhabditina
Rhabditoidea
Steinernematidae (25 species )
Heterorhabditidae (10 species)
MODE OF ACTION
Nematodes seek for insect host
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MODE OF ACTION
Nematodes penetrate into the insect host
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MODE OF ACTION
Nematodes release their symbiotic bacteria
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MODE OF ACTION
Insect dies due to the bacteria propagation
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MODE OF ACTION
Nematodes develop and reproduce in the host
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MODE OF ACTION
Nematodes leave the insect cadaver
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Nematode: a syringe for bacteria?
No, it is always a symbiosis
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SYMBIOSIS BETWEEN NEMATODES
AND BACTERIA
NEMATODE ADVANTAGES
BACTERIUM ADVANTAGES
 Nematodes feed on bacteria that grow
 Bacteria, without living inside the nematode
inside the insect body
intestine, cannot live by itself outside the
insect host
 Nematodes feed the insect tissues
Bacteria can only reach the insect by
depleted by the bacterium growth
means of the nematodes
 Nematodes can overcome the insect

immune-system by the immune-depression
action that bacteria cause to the insect
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Bacteria can overcome the insect
immune-system by the immunedepression action that nematodes cause
to the insect
NEMATODES AND THEIR SYMBIOTIC
BACTERIA
Nematode genus
STEINERNEMA
Nematode genus
HETERORHABDITIS
Symbiotic bacteria
genus
XENORHABDUS
Symbiotic bacteria
genus
PHOTORHABDUS
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Foraging Strategies and Insect Hosts
Cruiser
Ambusher
Static Insects (es. Otiorhynchus sp.) Dinamic Insects (es. Sciarids)
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Life Cycle of Entomopathogenic Nematodes
Steinernematids
Eggs
J1
J2
J2D
J3
Dev. in stress
J4
IJ
Normal Dev.
Males
Females
Eterorhabditids
J1-J4
IJ
Eggs
Hermaphrodites
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IJ
Hermaphrodites
Hermaphrodites
Males
Females
Eggs
Target:
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Otiorhynchus sulcatus
Other Target Insects
Insect Pests
Crops
Scarabeids:
Popilia japonica, Maladera matrida
Phyllopertha horticola, Aphodius spp.
lawns, orchards, nurseries,
Curculionids:
Otiorhynchus spp., Conorhychus
mendicus, Balaninus elephas,
Diaprepes abbreviatus, Cylas
formicarius
sweet potatoes
ornamentals, berries,
citrus, sugar beet,
chestnuts
Diptera:
Sciarids, Forids, Scatopsids, Cecidomids
mushrooms, greenhouses
Lepidoptera:
Nottuids
vegetables
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Entomopathogenic Nematode Production
In Vivo
In solid
In Vitro
In liquid
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Entomopathogenic Nematode Formulation
Old
In Sponge
In Clays
In Granules
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Actual
Innovative
under development
FIELD APPLICATION
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PROSPECTIVES
New Target:
Grillotalpa grillotalpa
Melolontha melolontha
Leaf miners
Fruit flies
Bactrocera sp.
Ceratitis sp.
Ragoletis sp.
Extended applications:
Foliar
Indoor
cockroach
flies
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Market Needs:
Low production costs
Technology
New strains
Higher infectivity
Higher production
Extended shelf life
Technology
New strains
Dry conditions
New applications:
Extreme environmental conditions:
cold
warm
dry
Symbiotic Bacteria exploitation
NEW ENTOMOPATHOGENIC NEMATODE
ACTIVE AT LOW TEMPERATURES
MARKET NEEDS
A product to control soil inhabiting insect pests
(weevil, grubs) at low temperatures (4-8°C).
(1996: Only Netherlands spent 2 Million US$ against
only 1 weevil species: Otiorhynchus sulcatus)
AVAILABLE PRODUCTS
CHEMICALS: few, not effective, not friendly
BIOLOGICAL: nematodes but at T°C above 12°C
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NEW ENTOMOPATHOGENIC NEMATODE
ACTIVE AT LOW TEMPERATURES
• A nematode strain has been discovered and it is very active against O.
sulcatus larvae even at 3°C
• The strain is effective against larvae of B. elephas at 8°C
• The strain belongs to Steinernema kraussei species
• The strain can be reproduced in vivo at 15°C
• The strain can be produced in liquid culture at 20°C without loosing its
cold activity
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ENTOMOPATHOGENIC NEMATODE SYMBIOTIC BACTERIA:
A NOVEL SOURCE OF INSECTICIDAL TOXINS
PHOTORHABDUS
Before 1996 entomopathogenic nematodes symbiotic bacteria were know to act
ONLY by means of nematodes
Different laboratories in the word, found out that symbiotic bacteria may have direct
(ingestion) activity against insect pests
Symbiotic bacteria (or their metabolites) have been patented for their use as:
- insecticide
- fungicides
- antibacterial activity
- anti-tumor activity
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ENTOMOPATHOGENIC NEMATODE SYMBIOTIC BACTERIA:
A NOVEL SOURCE OF INSECTICIDAL TOXINS
PHOTORHABDUS
1. Introduces a conceptual change in the mechanism of action of nematodes as
bioinsecticides.
2. Might offer a cost efficient simplification over the use of the symbiotic complex
nematode-bacterium for the control of certain insects.
3. Allows for the development of new bioinsecticide products for foliar application.
4. Might indicate the existence of a new group of microorganisms with insecticidal
capabilities similar to the Bacillus thuringiensis.
5. Can generate a new battery of genes originated in Photorhabdus spp. for inducing
insect resistance in transformed plants.
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ENTOMOPATHOGENIC NEMATODES
CONCLUSIONS
 For the soil dwelling insect pests, there are few
chemical insecticides available and with little efficacy
 Nematodes seek for insects and kill them
 Insects cannot easily develop resistance toward the
nematode-bacterium complex
 Entomopathogenic Nematodes are safe for the environment
 Entomopathogenic Nematodes may be used for IPM programs
 Due to their demonstrated safety, they are
exempted from the registration, in most countries
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