Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
2000-05-15
2004-03-09
Levy, Neil S. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C424S405000, C424S406000, C424S407000, C424S408000, C424S409000, C424S421000, C424S646000, C424S647000, C424S648000, C424S084000, C514S499000, C514S502000
Reexamination Certificate
active
06703036
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved stomach-action molluscicides. stomach poisons or edible baits containing them and their use in killing, controlling and/or inactivating molluscs, in particular, slugs and snails. More particularly, the present invention relates to a stomach-action molluscicide containing at least one additive, which is specifically included to increase the efficacy of such a molluscicide and which lowers the cost of production of such a molluscicide.
BACKGROUND TO THE INVENTION
Slugs and snails are major pests of agriculture in many parts of the world. The ecologies of different types of molluscs, which can be either terrestrial or aquatic, are very different and they usually require different types of treatment. The snail species,
Cepaea hortensis, Theba pisana, Helix aspersa, Cernuella virgata
and Achatina spp and the slug species,
Deroceras reliculatum, Arion hortensis, Milar budapestensis
and
Limax maximus
are of particular interest as targets. The common garden snail,
Helix aspersa
and the grey field slug,
Deroceras reticulatum,
are common garden pests throughout Australia. On the other hand, there are groups of snails, which have been introduced into Australia in the twentieth century that are ever increasing in number. These are the white Italian snail,
Theba pisana,
and the vineyard or Mediterranean snail,
Cernuella virgata,
which both cause extensive crop damage.
Significant crop damage by molluscs also occurs in northern Europe, the Middle East, North and Central America, South East Asia, Japan and New Zealand. In many cases, the rise to pest status of the slug or snail in question is a consequence of change—either in distribution (as in the case of accidental or deliberate introductions) or in agricultural practice, where crops or systems of cultivation may enable populations to rise to pest levels. Slugs are a major agricultural pest which cause significant crop damage by burying themselves in the soil and then moving along into holes drilled for planting new crop seeds in. Once the seed has been placed in the drill holes, they eat the inside out of the new seed, thereby potentially destroying the whole planting.
Chemical methods (i.e. the use of molluscicides), involving the use of stomach poisons for the control of such pests, are well known. Molluscicides containing metaldehyde and methiocarb have been in use for some while. The use of metal complexes in stomach-action molluscicides was first proposed by Henderson et al. in “Aluminium(II) and Iron(III) complexes exhibiting molluscicidal activity,” Australian Patent AU-B-22526/88. In one of their studies, these workers compared the relative toxicities of some aluminium and iron salts and chelates and their efficacies as stomach poisons, by injecting known amounts into the gut lumen of molluscs and they found that, in fact, the metal chelates were more toxic than their corresponding salts. Metal chelates were also first trialed by Henderson et al as contact-action poisons. In one particular study, Henderson used the metal chelate, FeEDTA, as the toxic agent, finding it just as effective as various salts of Fe(III). (Henderson, I. F. et al, in “A New Group of Molluscicidal Compounds,” BCPC mono., (1989), 41, “Slugs and Snails in World Agriculture”, pp 289-294 eds. Henderson, I. F., British Protection Council, Farnham, U. K.).
More recently, Puritch el al in “Ingestible Mollusc Poisons,” International Patent Application No. WO 96/05728 claimed a terrestrial mollusc stomach poison containing, as the active ingredient, either ferric edetate or the ferric hydroxy-ethyl derivative of edetic acid. These workers have also shown that mixtures of iron salts such as ferric sulphate, ferric chloride or ferric nitrate when mixed together with disodium EDTA or EDTA, as such, are toxic to the slug species,
Deroceras reliculatum.
The term “stomach-action molluscicide” is used herein in its broadest sense and includes a molluscicide, which is capable of being ingested into the stomach of the mollusc in an effective amount so as to kill and/or inactivate the mollusc.
The term “metal complexone” is used in its broadest sense and refers to a chelate of a metal with at least one ligand of the complexone type. The term “complexone” as used herein refers to an organic ligand containing at least one iminodiacetic group —N(CH
2
CO
2
H)
2
, or two aminoacetic groups —NHCH
2
CO
2
H
2
, or a derivative of either of these where the —CH
2
group is substituted, which form complexes with most cations. Suitable complexones include those disclosed in Wilkinson, G., “Comprehensive Coordination Chemistry,” Volume 2, Chapter 20.3, pp 777-792 which is incorporated herein by reference.
In general, most toxic compounds are also repellent and the interaction of toxicity with repellency prevents the ingestion of sufficient poison to kill the mollusc. Therefore, the essential problem that an effective stomach-action molluscicide has to overcome is that of palatability since in order for it to be effective, it must be ingested by the mollusc. Although Puritch et al claimed that their formulations provide a palatable molluscicide, indeed tests carried out on these formulations by the present inventor revealed the acidic, and hence possibly unpalatable, nature of these formulations. It is believed that a significant proportion of the efficacy, claimed by Puritch et al, is possibly due to the molluscicidal formulation of either ferric edetate or the ferric hydroxy-ethyl derivative of edetic acid, or indeed, mixtures of iron salts, such as ferric sulphate, ferric chloride or ferric nitrate, when mixed together with disodium EDTA or EDTA, acting as a contact poison rather than an ingestible poison. It is further believed that the claimed palatable nature of these formulations arises not so much from the inclusion of the specific active ingredient, but rather from the elements of the “inert” carrier containing bran/flour and a phagostimulant, which would cause the bait to be sufficiently palatable to allow ingestion.
The present inventor therefore initially sought to develop a molluscicide, wherein the active ingredient itself was more palatable, efficacious and also one which was not harmful to the environment. In this, the present inventor was successful and developed and made an application for a patent, International Patent Application No: PCT/AU97/00033, for a stomach-action molluscicide, containing the hydroxy compound, [Fe(OH)EDTA]
2−
or its dimer, [EDTA-Fe—O—Fe-EDTA]
4−
as the active ingredient, which was found to be more palatable to molluscs and therefore also more efficacious.
The present inventor serendipitously discovered that the addition of K
2
CO
3
or CaCO
3
as a filler to a molluscicidal bait containing FeEDTA, resulted in a bait that was more effective than with no additional filler being added. These fillers also fortuitously acted as pH adjusters which effectively adjusted the pH of the bait to around 8. At low pH, the Fe(III) atom in FeEDTA is surrounded by the two nitrogen atoms and the four oxygen atoms, provided by the hexadentate ligand, EDTA, and a water molecule acting as an additional seventh donor ligand. At a pH above 7, the water molecule is replaced by either an —OH group or an —O— group. At a pH of between 7 and 10, the species present in the majority are [Fe(III)(OH)EDTA]
2−
or its dimer, [EDTA-Fe—O—Fe-EDTA]
4−
with Fe(III)EDTA being present in the minority. The hydroxy compound and its dimer are in equilibrium, the relative amounts depending on the moisture of the pellet. According to F. G. Kari et al, Environ. Sci. Technol., (1995), 29, 1008, at a pH of about 8 to 8.5, there is virtually no Fe(III)EDTA present at all. The present inventor has found that molluscicides having a pH of greater than 7, but less than 9 or 10 appear to be more palatable than those having a pH of 7 or below. In addition, at higher pH, the Fe(III) ions are more readily replaced bv Ca
2−
ions, liberating the Fe(III
Burns Doane Swecker & Mathis L.L.P.
Levy Neil S.
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