A METHOD AND COMPOSITION FOR OBSERVATION AND CONTROL OF PITYOGENES CHALCOGRAPHUS

Abstract: The methylester of 2,4-decadienoic acid in combination with chalcogran is used for observation and control of Pityogenes chalcographus. A composition comprising an inert carrier contains as active ingredient a combination of the two substance.

Description: The present invention relates to a method for observ­ ation and control of the six-spined bark beetle, Pityogenes chalcographus, and the invention also relates to a composi­ tion for this. The interest in biological methods for the control of insect pests has been intensified during the last 10 years or more, and particularly so the interest in the use of the so-called pheromones, ie the characteristic scent substances through which animal species, such as insects, communicate and which initiate a behavioural re­ sponse or a biological activity. Some pheromones for control of pest insects have also been commercially available for several years now. The advantages of using pheromones for this purpose is their high selectivity, from which follows that they do not affect the environment. In contrast to conventional chemical pesticides the activity of pheromones for this purpose is directed almost entirely to the specific insect pest, and as pheromones are naturally occuring sub­ stances they do not give rise to resistance problems. Phero­ mones are active in extremely small quantities and they are biologically degradable. One area in which the use of pheromones is of parti­ cular importance is the control of forest insect pests as costly forest losses are suffered each year due to attacks of insects, both in the form of direct damages, where the trees are killed, and in the form of losses in growth and increment, which show up in the long run. The six-spined bark beetle attacks spruce, Picea abies, and can give rise to serious damage. Like most bark beetles it breeds in the nutritious phloem between the bark and the wood. For the six-spined bark beetle the male is the first to attack and boring in he releases aggregation pheromones which attract both sexes. The attraction of further males helps him to break down the resistance of the tree in the form of an abundant flow of resin. When the male has excavated a nuptial chamber a female is allowed into this and after mating the laying of eggs starts and the first female is followed by several others. Through the US patent 4205084 it is previously known that the chemical compound 2-ethyl-1,6-dioxaspiro[4.4]­ nonane, with the trivial name chalcogran, attracts bark beetles of the order Pityogenes chalcographus and can be used for selective control of these. However, the attracting effect of chalcogran is not sufficient for the substance to be used alone as an effecient control compound for Pityo­ genes chalcographus. According to the present invention it has been found that the methyl ester of 2,4-decadienoic acid in combination with chalcogran has a very good attracting effect on indi­ viduals of both sexes of Pityogenes chalcographus and the combination can thus be used for efficient observation and control of Pityogenes chalcographus. Methyl-2,4-decadienoate is a per se known compound which among other things occurs naturally as aromatic compound in pears. The methyl ester of 2,4-decadienoic acid can eg be prepared according to the process disclosed by L. Crombie in J. Chem. Soc. 1955, 1007. The present invention thus relates to a method of observing and controlling Pityogenes chalcographus using known techniques for observation and control of insects according to which traps are baited with attracting sub­ stances or according to which attracting substances are emitted over areas to cause confusion and distort the normal behaviour of the insects whereby the attractant comprises a combination of methyl-2,4-decadienoate and chalcogran. Attractant pheromones can be used for control of insects according to three methods: 1) for observing and monitoring the population 2) for direct control by trapping 3) for direct control by confusion According to the present invention methyl-2,4-deca­ dienoate in combination with chalcogran can be used for control of Pityogenes chalcographus according to any of the above methods. According to the first method traps baited with the attractant are used. Males and females are then attracted to the traps and the catch gives informa­ tion on the presence of the insect and the population den­ sity, information which can then be used to determine the appropriate moment for use of conventional pesticides and the amounts required to avoid overdosage. According to the second method baited traps are also used but in this case they are employed for direct killing of the trapped insects. Trap catching is according to the invention also used for the concenctration of the attack of bark beetles to selected trees in a tree stand which have been treated with the active attractant combination according to the invention and which trees attract the bark beetles. When the beetles have killed selected trees and the egg produc­ tion is finished the trees can be felled and the production of larvae destroyed by barking. As has been indicated above pheromones are active in very small quantities and the combinations of the inven­ tion are thus suitably used in some type of composition or with some technique which allows slow release and prefer­ ably controlled release. Compositions comprising solid or liquid carriers can be utilized, eg water, acetone, organic solvents, different mineral oils and vegetable oils, talcum, silica and different plastic materials. The substances can further be incorporated in a tablet or cap­ sule or some other kind of dispenser which permits slow release. The effect of the combination qf the methyl ester of 2,4-decadienoic acid and chalcogran can be further im­ proved by addition of substances from the groups terpenes, terpene alcohols, lower aliphatic and cycloaliphatic alcohols with 2 to 6 carbon atoms as well as by the addition of per se known pheromones. As examples of such effect improving substances can be mentioned, alpha- and betapinene, camphene, alphaterpinene, terpinols, alpha-ter­ pineol, terpinen-4-ol, thujanol, ethanol, 2-methylbutan-2-­ ol, 1-hexanol, cyclohexanol, 2-methyl-3-buten-2-ol, 2-­ metylbutyne-2-ol, ipsdienol, cis-verbenol and ipsenol. It is particularly preferred to use the combination of the ester and chalcogran in further combination with one or several monoterpenes, particularly -beta-pinene, +alpha-­ pinene, -alpha-pinene and camphene. Another preferred addition to the combination is the lower alcohol methyl-butenol, which may be replaced by methylbutanol or methylbutynol, which acts as a solvent and which is preferably used with combinations of chalcogran, the methyl ester and cis-verbenol. According to the invention methyl-2,4-decadienoate is used in combination with chalcogran and a substantially increased effect in the attraction of Pityogenes chalco­ graphus is obtained compared with the use of solely chal­ cogran. Chalcogran exists in several isomeric forms and is used in the form of any of these or as a racemate, as previously known. In the same manner methyl-2,4-decadien­ oate can be used as a racemate or in the form of one or several of its four isomers. The combination shall contain effective amounts of the respective substances for the desired attraction and in the combination the weight ratio of methyl-2,4-decadienoate to chalcogran is suitably within the range of from 1:10000 to 100:1 and preferably within the range of from 1:100 to 50:1. It is usually suitable to have almost the same amounts of the two substances or more of chalcogran than of the ester. The present invention also relates to a composition for attracting Pityogenes chalcographus which comprises an inert carrier and as active component a combination of methyl-2,4-decadienoate and chalcogran. The weight ratio between the methyl ester and chalcogran in the combination is suitably within the range of from 1:10000 to 100:1 and preferably within the range of from 1:100 to 50:1. Further embodiments of the compositions according to the invention comprise, besides the combination of chal­ cogran and the methyl ester, additional substances from the groups terpenes, terpene alcohols, lower alcohols and pheromones as disclosed above. The method and the composition according to the inven­ tion are based on the attractant effect of the combination of methyl-2,4-decadienoate and chalcogran. A racemate or one or several of the possible isomers of the methyl ester can be used. A certain improvement of the effect seems to be obtained with the trans-cis isomer and thus it is especially preferred to use this in the method and the composition of the invention. The invention is further illustrated in the following examples, which, however, are not intended to limit the same. Example 1 The attracting effect of methyl-2,4-decadienoate in combination with chalcogran was investigated in a labora­ tory test. In this test a laminar air flow with a speed of 2 m/sec was created over an area covered by filter paper. A capillary with the substances was placed upwind. The bark betlees were released 10 at a time 14 cm downwind from the capillary. Those which walking orient themselves within a circle having a radius of 1.5 cm out from the capillary are considered as having given a positive response to the attractant. The method is further described by Byers, J.A. and Wood, D.: J. Chem. Ecol. 7 :9-18, 1981. The results of a test series carried out with the given technique is shown in the Table. It is evident that the combination of methyl-2,4-decadienoate and chalcogran in corresponding amounts attracts 70% of the females and 40% of the males while the methyl ester alone or chalcogran alone at the most attracts 10% of the insects. Table : Attraction of Pityogenes chalcographus to an attractant consisting of methyl-2,4-decadienoate in combination with chalcogran. 1) The absolute amount = 2.2 g/min times the given values. Examples 2 - 5 Examples 2 to 5 give the results of field tests in spruce forests at different locations and thus with varying populations of Pityogenes chalcographus. Tubular traps were baited with the respective active substances and placed between the trees. The results are given as number of trapped insects. When chalcogran was used alone the traps were baited with 100 mg of chalcogran and for the combination the traps were baited with 100 mg of chalcogran and 100 mg of the ester. The mixture of terpenes comprised -beta-pinene, +alpha-pinene, -alpha-pinene and camphene. The traps were baited with 100 mg chalcogran, 100 mg methyl ester and 4×10000 mg of the terpenes. The traps were baited with 100 mg of chalcogran, 100 mg of the methyl ester and 10000 mg of the respective terpene. The traps were baited with 100 mg chalcogran, 100 mg methyl ester and for the second composition 1500 mg of 2-methyl-3-butene-2-ol and 100 mg cis-verbenol.

Claims: 1. A method of observing and controlling Pityogenes chalcographus using known techniques for observation and control of insects according to which traps are baited with attracting substances or according to which attracting substances are emitted over areas to cause confusion and distort the normal behaviour of the insects, characterized in that the attractant comprises a combination of methyl-­ 2,4-decadienoate and chalcogran. 2. A method according to claim 1, characterized in that the attractant further comprises one or several mono­ terpenes. 3. A method according to claim 2, characterized in that the monoterpene is -beta-pinene, +alpha-pinene, -alpha-­ pinene and/or camphene. 4. A method according to claim 1, characterized in that the attractant further comprises cis-verbenol and 2-methyl-3-butene-2-ol. 5. A composition suitable for observation and control of Pityogenes chalcographus comprising an inert carrier, characterized in that it as active ingredient contains a combination of methyl-2,4-decadienoate and chalcogran. 6. A composition according to claim 2, characterized in that the weight ratio of methyl-2,4-decadienoate to chalcogran is within the range of from 1:10000 to 100:1. 7. A composition according to claim 5 or 6, character­ ized in that it further comprises one or several monoterpenes. 8. A composition according to claim 7, characterized in that the monoterpene is -beta-pinene, +alpha-pinene, -alpha-pinene and/or camphene. 9. A composition according to any of claims 5 to 8, characterized in that it further comprises cis-verbenol and 2-methyl3-butene-2-ol.

Inventors: BERGSTROM, GUNNAR, BIRGERSSON, GORAN, BYERS, JOHN, LOFQVIST, JAN, Bergström, Gunnar, Birgersson, Göran
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: A01N43
IPC codes: A01N37, A01N31, A01N43, A01P19