Patent Abstract:
the present inventors have found that the contrasting chemical , physical and environmental characteristics of alpha and beta endosulfan provide an opportunity to formulate an effective endosulfan formulation with lower risk to the environment . accordingly , the present invention provides a method for controlling or reducing pest numbers in an area affected or likely to be affected by pests , the method comprising applying to the area an endosulfan formulation , the formulation comprising beta endosulfan and alpha endosulfan , wherein the ratio of beta to alpha endosulfan in the formulation is at least 3 . 5 : 6 . 5 w / w .

Detailed Description:
in order that the nature of the present invention may be more clearly understood preferred forms thereof will now be described with reference to the following figures in which : [ 0053 ] fig2 . shows persistence of the acute toxicity of various endosulfan formulations towards helicoverpa larvae . sicot 50 plants , grown in the field at narrabri nsw , australia , were sprayed until runoff with 0 . 5 % ( a ) and 0 . 25 % ( b ) active ingredient endosulfan formulations or with blank formulation . treatments were : alpha - endosulfan ( 85 % alpha - isomer : 15 % beta - isomer ); beta - endosulfan ( 95 % beta - isomer : 5 % alpha - isomer ); commercial endosulfan ( thiodan — aventis cropscience pty ltd — 70 : 30 w / w alpha to beta endosulfan ); blank formulation ( no active ingredient ). formulations were prepared to mimic the formulation of the commercial pesticide . leaves ( 10 ) from each treatment were picked at various days after endosulfan application and provided to 5 first instar helicoverpa larvae . leaves were kept in agar tubs to retain leaf quality and after 4 days at 25 ° c . the survival rates of the larvae was determined . [ 0054 ] fig3 . crop damage by helicoverpa larvae following treatment with various endosulfan formulations . 4dat1 = 4 days after treatment 1 , 7dat1 = 7 days after treatment 1 , 4dat2 = 4 days after treatment 2 , 7dat1 = 7 days after treatment 2 , and 11dat1 = 11 days after treatment 2 . [ 0055 ] fig4 . number of helicoverpa larvae following treatment with various endosulfan formulations . 4dat1 = 4 days after treatment 1 , 7dat1 = 7 days after treatment 1 , 4dat2 = 4 days after treatment 2 , 7dat1 = 7 days after treatment 2 , and 11dat1 = 11 days after treatment 2 . the endosulfan formulations of the present invention can be prepared using techniques known in the art . generally , the formulation is prepared such that the endosulfan can be delivered to the pest by ingestion and / or contact . technical grade endosulfan is a brown crystalline substance consisting of alpha and beta isomers in the ratio of approximately 70 : 30 , and has a purity of about 94 to 99 %. many formulations containing endosulfan are commercially available . pesticide manufacturers make use of various inert ingredients ( such as alcohol solvent emulsifiers ; petroleum distillate emulsifiers ; suspension agents , water , clay , and wetting agents ; and talc ) to produce these formulations . in general , commercially available formulations are purchased by the consumer as an emusifiable concentrate ( typically about 35 % endosulfan w / v ) or as ulv formulations ( typically about 25 % endosulfan w / w ). however , endosulfan is also available in other forms including as a wettable powders , aqueous suspensions , dusts , granules and baits . emulsifiable concentrates can at least contain between 15 and 40 % active agent mixed with an emulsifier and a suitable solvent . commercially available formulations are typically diluted in water by the consumer before use to a concentration around 0 . 5 % endosulfan which forms an oil - in - water emulsion that is usually applied as a spray . in one example , an endosulfan emulsified concentrate contains ( figures for 1 l of concentrate ) 350 g / l of technical grade endosulfan ( 99 % purity ), 37 g of alkyl phenol ethoxylate and 33 g of calcium dodecyl benzene sulfonate as emulsifiers , with the balance being an aromatic hydrocarbon as solvents . a further example of an oil - in - water endosulfan emulsion is provided u . s . pat . no . 5 , 531 , 995 which discloses a formulation comprising 190 g / l to 350 g / l endosulfan , 150 g / l to 400 g / l of the methyl ester of rosin ; 30 g / l to 200 g / l of at least one surfactant ; water to make up to one liter , but not less than 200 g / l ; and optionally up to 200 g / l of at least one polar solvent which is at least partially soluble in water . the surfactant can , for example , be alkoxylated triglycerides such as ethoxylated castor oil , ethoxylated propoxylated castor oil ; or alkoxylated sorbitan fatty esters . ultra low volume ( ulv ) endosulfan formulations generally do not contain water but do possess high - boiling point solvents . they are solvent / mineral based formulations generally comprising about 25 % endosulfan and are designed to be applied neat by aerial application or small droplet applicators . one example of an ulv endosulfan formulation comprises ( figures for 1 l of concentrate ) about 242 g / l of technical grade endosulfan ( 99 % purity ), 3 g of alkyl phenol ethoxylate and 7 g of calcium dodecyl benzene sulfonate as emulsifiers , 10 g of epoxidised soybean oil as a stabiliser , and 350 ml of mineral oil and the balance being an aromatic hydrocarbon as solvents . further examples of such formulations are provided in u . s . pat . no . 3 , 952 , 102 and u . s . pat . no . 3 , 996 , 375 . u . s . pat . no . 3 , 952 , 102 discloses an ulv endosulfan formulation comprising 60 to 84 . 5 weight % of a solvent mixture of 1 . 5 to 2 . 5 parts by weight of a vegetable oil consisting of rapeseed , cottonseed , peanut , sunflower , or safflower oil , and from 0 . 5 to 1 . 5 parts by weight of an aromatic hydrocarbon having a boiling range of from 170 ° c . to 250 ° c . consisting of one or more alkyl benzenes having 9 to 11 carbon atoms ; or 1 - or 2 - methyl naphthalene ; and from 0 . 5 to 6 weight % of an epoxide selected from the group consisting of epichlorohydrin , epoxypropane , styrene oxide , phenylepoxy propane , and an epoxide of an unsaturated vegetable oil . endosulfan formulations of the present invention can also take the form of an ultra low / emulsifiable concentrate ( ul / ec ). these formulations are solvent / mineral oil based and generally about 240 g / l endosulfan . they are designed to be applied neat or diluted with water by spray . an example of an endosulfan ul / iec formulation comprises contain ( figures for 1 l of concentrate ) 242 g / l of technical grade endosulfan ( 99 % 0 purity ), 30 g of alkyl phenol ethoxylate and 40 g of calcium dodecyl benzene sulfonate as emulsifiers , log of epoxidised soybean oil as a stabiliser , and 350 ml of mineral oil and the balance being an aromatic hydrocarbon as solvents . endosulfan formulations have also been prepared as microemulsions . these are stable , water based dispersions of two immiscible liquids with adjusted emulsifiers with little or no solvent . microemulsions are diluted with water prior to spray . an example of an endosulfan microemulsion comprises ( figures for 1 l of concentrate ) about 35 3 g / l of technical grade endosulfan ( 99 % purity ), 20 g of polycarboxylate copolymer as a dispersant , log of nonionic ethoxylate as a wetting agent , 40 g of propylene glycol as an humectant , and 60 ml of aromatic hydrocarbon as a solvent , with the balance being water . wettable powders can contain between 15 and 50 % active ingredient ( technical ) with clay and wetting agents as inert ingredients . the commercial product is diluted in water before spraying . an example of an endosulfan wettable powder formulation comprises ( figures for 1 l of concentrate ) about 505 g / l of technical grade endosulfan ( 99 % purity ), 20 g of polyalklaryl sulphonate or sodium ( or calcium ) lignosulfonate as a dispersant , log of nonionic ethoxylate as a wetting agent , with the balance being clay or talc . an example of an aqueous suspension of endosulfan is provided in u . s . pat . no . 4 , 804 , 399 which discloses a liquid pesticidal composition in the form of a concentrated aqueous suspension consisting essentially of 15 to 50 % by weight endosulfan , an alkali metal salt of sulfosuccinic acid semiester prepared by reaction of a polyglycol ether of a condensation product of ( c 8 - c 12 )- alkylphenol and formaldehyde with maleic anhydride and an alkali metal sulfite , and an alkali metal salt of a ligninsulfonic acid in admixture with identical parts of a swelling alkaline earth metal silicate . u . s . pat . no . 5 , 753 , 591 also discloses an aqueous suspension endosulfan concentrate . in this case the formulation comprises endosulfan , a surfactant combination of a neutralized phosphoric ester based on an ethoxylated alkylphenol and an ethoxylated alkylaryl - and alcohol phosphate ester . u . s . pat . no . 5 , 653 , 973 provides an example of a bait for lepidopteran species comprising endosulfan . the endosulfan formulations of the present invention can be encapsulated in microcapsules as generally described in u . s . pat . no . 5 , 549 , 903 and u . s . pat . no . 6 , 294 , 570 . the formulations of the present invention can be prepared by the same techniques currently used to prepare endosulfan pesticides with the exception of the increased amount of beta endosulfan when compared to alpha endosulfan . this higher ratio of beta to alpha endosulfan can be achieved by any technique known in the art . it can also be achieved by using the method of the sixth aspect of the present invention . using this method , substantially pure formulations of beta endosulfan and alpha endosulfan can be obtained and mixed to the desired ratios . endosulfan formulations of the present invention will contain at least one acceptable carrier . suitable carriers are well known to those skilled in the art , where the carrier ( s ) will depend upon the type of formulation . for instance , emulsified concentrates are diluted in water before use , whereas ulv formulations at least comprise a solvent . the endosulfan formulations of the present invention can be applied to an area using the same techniques used with currently available endosulfan formulations . liquid formulations can be applied by spraying ( for example , aerial or boom spray ) or by air blasting . application rates vary considerably on the crop and target pest . examples of application rates for cotton crops are approximately 3 l / ha for ulv formulations and 735 gai / ha for water in emulsion formulations . the method of separating a mixture of alpha and beta stereoisomers may include the following steps : ( a ) providing a solution of commercial endosulfan being a mixture of alpha and beta endosulfan , in a solvent . the concentration of the solution depending on the solvent and the temperature of the solvent . for example , at a concentration of 20 g / l in 60 - 80 petroleum ether at 25 ° c . ( b ) cooling said solution . the temperature of cooling depending on the solvent . for example , at − 20 ° c . for a solution in 60 - 80 petroleum ether . ( d ) filtering the resultant crystalline precipitate and washing with the same cooled solvent to provide crystals of primarily beta - endosulfan . ( e ) evaporating solvent from the residual supernatant solution to provide crystals of primarily alpha - endosulfan . beta endosulfan enrichment was also achieved in the following manner . commercial endosulfan ( 70 % alpha : 30 % beta , 5 g ) was added to refluxing hexane ( 25 ml ) and sufficient dichloromethane was added gradually until the endosulfan had just dissolved . the solution was allowed to cool to room temperature then cooled further overnight in a freezer at − 20 degrees . the crystals of beta - endosulfan were filtered and washed with a small volume of hexane . the residue from concentration of the supernatant mother liquor in a solvent evaporator comprised enriched alpha - endosulfan . a single recrystallisation of the beta - endosulfan crystals from dichloromethane - hexane ( 70 : 30 ) gave the purified isomer ( 99 . 5 % beta ; 0 . 5 % alpha ). trials were conducted using beta - enriched formulations according to the invention which were compared with alpha - enriched formulations and commercial formulations ( alpha to beta ratio 70 : 30 ). the trials were conducted to minic conditions that occur in the field . the endosulfan formulations were prepared by diluting the following concentrate ( figures for 1 l of concentrate ) in water : 364 g / l of 96 % technical grade endosulfan , 37 g of nonyl phenol ethoxylate , 33 g of 60 % calcium dodecyl benzene sulfonate in 2 - ethylhexanol with the balance being an aromatic solvent . results from this trial indicated that the beta - enriched formulation was approximately equally toxic to helicoverpa in comparison to the commercial formulation over a nine - day period ( fig2 ). this experiment was performed using cotton plants under australian field conditions in april , when mean daily maximal temperatures were 27 . 0 ° c . and mean daily minimal temperatures were 11 . 8 ° c . in australia , endosulfan is used to control helicoverpa in the warmer month of december ( mean daily max . 32 . 9 ° c ., min . 17 . 6 ° c .). it was predicted that the alpha - isomer would volatilise at a greater rate under these conditions and that its persistence on the cotton plant would be reduced as a result . a small plot replicated ground trial was conducted during the 2000 / 2001 cotton season to evaluate the efficacy of a 240 g a . i ./ l β - endosulfan formulation in comparison to the commercial product thiodan ( aventis cropscience pt7 ltd — 70 : 30 w / w alpha to beta endosulfan ), for the control of heliocoverpa spp . in cotton . the trial was conducted near boggabri in the namoi valley of north - western new south wales , australia . the following treatments were evaluated in the trial : 1 . β - endosulfan ( 95 %), α - endosulfan ( 5 %) at 368 g ai / ha 2 . β - endosulfan ( 95 %), α - endosulfan ( 5 %) at 735 g ai / ha 3 . thiodan at 735 g ai / ha 4 . untreated control the beta enriched formulations were prepared generally as described above in example 2 , however , as they only contained 240 g a . i ./ l , endosulfan , the extra volume was made up by additional aromatic solvent . the trial was laid out using a randomised complete block design with four replicates . plots were 6 m wide by 15 m long , with treatments applied to the centre two rows only . the treatments were applied twice , 7 days apart , using a 2 m wide boom spray . assessment for helicoverpa control were carried out prior to each treatment application and every 3 to 4 days after treatment application , until the treatments were reapplied or the trial was concluded . assessment was accomplished by counting the number of helicoverpa eggs and larvae , and the number of damaged squares and bolls on 20 randomly selected cotton terminals per plot . the helicoverpa population was 30 % heliocoverpa armigera at the commencement of the trial and over the duration of the trial the proportion of h . armigera increased . leaf samples , consisting of approximately 200 g of leaf , were collected four and seven days after each treatment and analysed by gas chromatography / mass spectroscopy to determine relative levels of α - endosulfan , β - endosulfan and endosulfan sulfate . all treatments provided equivalent and significant control of the helicoverpa population present in the trial ( fig3 and 4 ). no significant rate response was detected in the control provided by β - endosulfan enriched formulation as the application rate decreased from 735 g ai / ha to 368 g ai / ha . residue analyses found that the ratio of endosulfan sulfate to β - endosulfan residues increased over time in all leaf samples . however , the ratio was five times higher in leaves treated with thiodan than in leaves treated with β - endosulfan ( table 3 ). this is in agreement with levels of endosulfan sulfate found in leaves of other plants after treatment with individual isomers ( chopra and mahfouz , 1977 ; mukherjee and gopal , 1994 ). for instance , 14 days after treatment a - endosulfan treated tobacco plants contained 0 . 5 ppm endosulfan sulfate where as β - endosulfan treated plants contained 0 . 1 ppm of the toxic metabolite . the results of the field trial demonstrate equivalent efficacy of a β - 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