DESCHIETERE, Johan, I.C. (Zwijnaardsesteenweg 518, Gent, B-9000, BE)
OSINGA, Anne, J. (Dirk van Voornestraat 12, AC Rockanje, NL-3235, NL)
DESCHIETERE, Johan, I.C. (Zwijnaardsesteenweg 518, Gent, B-9000, BE)
| CLAIMS 1. An insecticidal composition comprising a mixture of a polymer binder and a suspension of one or more entomopathogens, characterised in that the mixture comprises an oily substance in a ratio to the polymer binder allowing migration of the entomopathogens out of said composition. 2. Composition according to claim 1, characterised ir that the ratio of the oily substance to the polymer binder is 30% at maximum. 3. Composition according to claim 1 or 2 , characterised in that the migration is a continuous migration . 4. Composition according to any one of the claims 1- 3, characterised in that the entomopathogens comprise organisms such as bacteria, viruses, fungi, nematodes, protozoans capable of infecting and killing insects. 5. Composition according to any of the claims 1-4, characterised in that the oily substance comprises fat. 6. Composition according to any of the claims 1-5, characterised in that the oily substance comprises Ondina oil like Ondina EL, Shellsol T and/or Tween, in particular Tween 20. 7. Composition according to any of the claims 1-6, characterised in that the fungi comprises any known or to be selected- for isolate of Beauveria bassiana and/or Metarhizium anisopliae . 8. Composition according to any of the claims 1-7, characterised in that the polymer binder comprises polyurethane , polyvinylacetate , acrylate possibly a foam based acrylate coating, and/or polyvinylalcohol . 9. Composition according to any of the claims 1-8, characterised in that the composition comprises a maximum of 55%, in practise around 40%, spores of fungi of the entomopathogens relative to the oily substance. 10. Composition according to claim 9, characterised in that the oily substance comprises Shellsol T. 11. Composition according to any of the claims 1-10, characterised in that the composition comprises insect growth regulators such as pyriproxifen and/or triflumuron. 12. Insect screen or netting or cloth material provided with a coating which comprises the composition according to any of the claims 1-11. 13. Insect screen or netting or cloth material according to claim 12, characterised in that the screen, netting, or cloth is coated with the composition. 14. Insect screen or netting according to claim 12 or 13, characterised in that the screen, netting, or cloth is provided with insect attracting substances and/or means, be these physical (e.g. colour) or chemical means (attractive volatile organic compounds) . 15. Container or spray can comprising a composition according to any of the claims 1-11. |
PROLONGED PERIOD OF OPERATION
The present invention relates to an insecticidal composition comprising a mixture of a polymer binder and a suspension of one or more entomopathogens .
Such a composition is known from US-5 , 141 , 744. In example 8 therein water swollen pieces of water retentive polymers were added to an aqueous suspension of
entomopathogens in the form of fungal pathogen {Beauveria bassiana) spores in order to prepare macrogels in a process called hydromacroencapsulation . The entomopathogens are suspended in an aqueous solution of a gel forming matrix in the presence of the polymer and thereafter gelated by means of a gelling agent for long time storage. The macrogel composition may thereafter be applied in particular sprayed on the spot .
Apart from the fact that the manufacturing process is relatively complex, on the spot application of the
composition means that infection of in this case mosquitoes or other susceptible arthropods with the fungi is initiated instantaneously, and thereafter has a short effective working duration.
It is an object of the present invention to provide a more effective composition having a longer duration of effectiveness .
Thereto the composition according to the invention is characterised in that the mixture comprises an oily
substance in a ratio to the polymer binder allowing
migration of the entomopathogens out of the composition. It is an advantage of the composition according to the present invention that a release function concerning migration of entomopathogens through the polymer binder and through the external surface of the composition is created. By influencing the actual ratio between the oily substance and the polymer binder the resistance experienced by the fungal spores or any other entomopathogenic agent and their degree and speed of migration can be influenced. Adjustment of the ratio allows for a longer effective period during which the potential harmful insects, if allowed to get in contact with the insecticidal composition, are infected with the migrated entomopathogens. This also has a
favourable effect in terms of reducing their lifespan and thus their ability to transmit harmful pathogens to humans or livestock, and in addition it prevents the harmful insects from successfully developing resistance against the applied entomopathogens, in particular if a substantial part or all of these entomopathogen-infected insects die before they are capable of transmitting harmful pathogens to humans or livestock (Read et al . 2009) . By adjusting the mentioned ratio the binder also prevents the water
requiring entomopathogens from drying out, which prolongs their lifetime within the composition.
The oily substance provides a carrier for the
entomopathogens to diffuse continuously to the outer surface of the composition. Advantageously there exists a continuously replenished presence of potentially active entomopathogens at the outer surface which in turn
provides, if the harmful insects make contact, a longer duration of effectiveness.
The composition may have the form of possibly pre- expanded spheres, but may also have the form of powder, or spray. The composition can be sprayed on a mosquito screen or netting, or cloth, or directly on surfaces visited by harmful arthropods in order to have the entomopathogenic agent destroy the insects before being capable of infecting humans or livestock with disease-causing pathogens or cause nuisance .
Example 1
Metarhizium dissolved in oil sprayed in a pottery pot where Anopheles gambiae mosquitoes where subjected to during 17 hours with around 4 x 10 10 conidia/m 2 resulted in a 100% mortality within 10 days (Farenhorst et al . 2008). On average 95% of the dead mosquitoes showed fungal growth in the form of a white mold emerging from the cadaver and producing new spores for inducing further infections.
Example 2
Spores of Metarhizium and/or Beauveria bassiana are mixed in an oily substance like Ondina EL, and/or Shellsol T, and suspended in a polymer such as polyurethane or acrylate whereto cellulose fibers may be added. The thus obtained composition may be sprayed on an object, such as a sheet of paper, a screen, wall, netting, or cloth. Example 3
As in example 2 the oil comprising the spores is prepared. The polymer is applied to the object and dried. Thereafter the oil spores suspension is sprayed onto the polymer. This has the advantage that the oil spores mixture is not subjected to higher temperatures of between 35-55
°C, in particular 40-50 °C due to the drying of the polymer, which makes the insecticidal composition longer effective.
Example 4
A preferred embodiment of the composition uses polyvinylalcohol (PVA) , which is a water soluble synthetic polymer, which is not affected by oil and not toxic to the spores. PVA is also available on the market in variants that are not soluble in water of around 25 °C or lower.
Advantageously such a PVA coating does not dissolve in rainwater. To 50% soft PVA, 50% water has been added, which was mixed with Shellsol T wherein the spores of Beaveria bassiana were stirred. Advantageously this composition can be dried in the air and no forced drying is required. This embodiment showed very good results in terms of mosquito mortality .
Example 5
Beauveria bassiana spores in a 5 ml spore mix was stirred with Shellsol oil. 5 ml of a 10% polymer binder mixed with the oil-spore mix was applied on paper with a coating machine in a 12 μτη thick layer. Paper is a medium which absorbs oil very well. The mosquitoes if subjected during 2 hours to the coated paper all died within 15 days.
Example 6
Same as the composition of example 5, but now Tween 20 was added to the oil-spores mixture, as a stabilizer and an emulsifying agent. The applied soap of a 10%
concentration of Tween 20 was helpful with the mixing of oil and spores, but in a pure form it had a negative effect on spore survival due to it being too sticky. The
mosquitoes if subjected during 2 hours to the coated paper all died within 6 days.
It appeared that in those tested cases wherein moderate results were achieved in terms of mortality of the mosquitoes, that allowing the coating, such as applied on the paper, to dry for several days to one week or longer the results improved. This is possibly due to the sweating out of an increasing number of spores to the surface of the composition .
It turned out that to ensure a proper binding of spores to the mosquitoes, the spores should preferably be dry and powdery on the surface and not binding too much to a sticky oil, fat or coating. Spores stay dormant inside the composition as they only germinate on and subsequently grow inside the mosquitoes and then need carbohydrates.
As opposed to Metarhizium which was less effective and only survived on paper for 2-4 weeks, Beauveria
bassiana spores in a concentration of 4 x 10 10 were still viable, infective and virulent to mosquitoes 7 months after being coated in Shellsol on paper. Thereafter all
mosquitoes were still killed within 12 days after exposure.
Insect attracting substances (kairomones like 1- octen-3-ol, ammonia, 2 -oxopentanoic acid, and the like) and/or means to induce contact between harmful insects and the proposed formulations (e.g. substrate colour) are considered for incorporation in the formulations to enhance effectivity, as well as means to reduce environmental influences (e.g. UV light) that may impair the effective period of the formulation.
In general a maximum of 40% spores relative to the oily substance, such as Shellsol T, is preferred in
practise. An upper limit of 55% spores can be included in the oily substance, and such a mixture can then be mixed in the binder in order to prepare a coating.
Applying too much oil makes the composition too sticky, whereas applying too much polymer binder prevents the entomopathogens , in particular the fungi, to migrate out of the composition unhampered. A maximum percentage of 30% oil/spores solution relative to the binder material preserves a continuous migration to the outer surface of the insecticidal composition.
It may be preferred to add insect growth regulators such as pyriproxifen and/or triflumuron to the composition.
References Farenhorst M, et al . (2008) African water storage pots for the delivery of the entomopathogenic fungus Metarhizium anisopliae to the African malaria vectors Anopheles gambiae s.s. and An. funestus . Am. J. Trop. Med. Hyg. 78(6) :910- 916.
Read, A. F. et al . (2009) How to make evolution-proof insecticides for malaria control. Plos Biol. 7(4) :e!000058
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