Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata.

FIELD OF THE INVENTION

This invention relates to the use of a coleopteran active B. thuringiensis or its delta endotoxin in controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata, a method of controlling Chrysophtharta bimaculata by applying an effective amount of coleopteran active B. thuringiensis or its delta endotoxin to an area infested by Chrysophtharta bimaculata, and insecticidal compositions for controlling Chrysopht¬ harta bimaculata.

BACKGROUND OF THE INVENTION

Commercial preparations of Bacillus thuringiensis are used worldwide for biological control of pest insects. The advantages of these bacterial insecticides are that they are highly selective for a very limited range of target insects and are biodegradable.

Commercial preparations of Bacillus thuringiensis can be, applied right up to the time of harvest with no adverse effects.

Bacillus thuringiensis is a rod shaped, aerobic, spore forming bacterium uniquely characterized by the production during the sporulation process of one or more inclusions, referred to as parasporal crystals. These crystals are composed of high molecular weight proteins, referred to as delta-endotoxins. The delta-endotoxins are the active ingredient in available commercial preparations of Bacillus thuringiensis.

Many B. thuringiensis strains with different insect host spectra have been identified. They are classified into different subspecies based on their flagellar antigens. Of particular interest is Bacillus thuringiensis subspecies kurstaki and subspecies aizawai used for the control of lepidopteran pest insects, Bacillus thuringiensis subspecies israelensis used for the control of dipteran pest insects and Bacillus thuringiensis

subspecies tenebrionis and Bacillus thuringiensis subspecies San Diego used for the control of coleopteran pest insects.

The first isolation of a coleopteran toxic Bacillus thuringiensis was reported in 1983 (A. Krieg et al., Z. ang. Ent. 96, 500-508, European Patent Publication EP 0149162 A2).

The isolate, which was designated Bacillus thuringiensis subsp. tenebrionis, has been deposited with the German Collection of Microorganisms under accession number DSM 2803. Bacillus thuringiensis subsp. tenebrionis was isolated in 1982 from a dead pupa of the mealworm, Tenebrio molitor (Tenebrionidae, Coleoptera). The strain produces within each cell one spore and one insecticidal parasporal crystal which is of flat plate-like form with an edge length of about 0.8 μm to 1.5 μm. It belongs to serotype H8a,8b and pathotype C of Bacillus thuringiensis (Krieg et al., System.Appl.Microbiol. 9, 138-141, 1987, US patent 4,766,203, 1988).

It is only toxic against certain leaf eating beetle larvae (Chrysomelidae), but ineffective against caterpillars (Lepidoptera), mosquitoes (Diptera) or other insects.

Coleopteran active Bacillus thuringiensis has been shown to be an effective control agent for the Colorado potato beetle larvae. After uptake of crystals and spores from coleopteran active Bacillus thuringiensis or isolated crystals larvae, and to a certain extent adults, of the Colorado potato beetle (Leptinotarsa decemlineata) stop feeding. Larvae stages L1-L3 die within 1-3 days (Schnetter et al., in "Fundamental & applied aspects of invertebrate pathology", eds. R.A. Samson et al., Proceedings of the

4th Int. colloquium of Invertebrate Pathology, p. 555, 1986).

The activity of B. thuringiensis subsp. tenebrionis and San Diego has further been confirmed against the elm leaf beetle Xanthogaleruca luteola, and for B. thuringiensis subsp. tenebrionis activity has also been demonstrated against the cereal leaf beetle Oulema melanopa (Lema melanopa(L.)).

However, it has also been found that coleopteran active B. thuringiensis does not exhibit activity towards all insects within the Chrysomelidae. It has for example been found that it has no activity towards the small black flea beetle, Phyllotreta atra and the small striped flea beetle, Phyllotreta undulata, and only minor activity against

the banded cucumber beetle, Diabrotica balteata, and the asparagus beetle, Crioseres asparagi.

Four commercial products of coleopteran active Bacillus thuringiensis have been developed for the control of coleopteran pests. NOVODOR ^® from Novo Biokontrol, Novo Nordisk A/S, TRIDENT ^® from Sandoz, and DiTerra ^® from Abbott Laboratories Inc. all based on Bacillus thuringiensis subspecies tenebrionis, and the commercial product M-one ^® from Mycogen Corporation based on a closely related strain Bacillus thuringiensis subsp. San Diego.

The Tasmanian leaf beetle Chrysophtharta bimaculata is a major forrest pest responsible for much damage caused by defoliation of eucalyptus trees.

SUMMARY OF THE INVENTION

It has now been found that coleopteran active B. thuringiensis delta endotoxin exhibits activity towards a Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata. This invention consequently relates to the use of coleopteran active B. thuringiensis or its delta endotoxin in controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata.

The present invention also relates to a method of controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata by applying an effective amount of a coleopteran active B. thuringiensis or its delta endotoxin to an area infested by Chrysophtharta bimaculata.

The invention further relates to insecticidal compositions for controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above the present invention in its first aspect relates to the use of coleopteran active B. thuringiensis products such as, NOVODOR ^® , for controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata.

In its second aspect the invention relates to a method of controlling the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata by applying an effective amount of a coleopteran active B. thuringiensis product to an area infested with said Tasmanian eucalyptus leaf beetle. In this context the expression "effective amount" should be understood as single or repeated applications of from 0.5 1/ha to 8 1/ha of flowable preparations or 0.25 kg/ha to 5 kg/ha of powder or granular preparations.

The invention in its third aspect relates to pesticidal compositions or preparations comprising the coleopteran active B. thuringiensis delta endotoxin product in admixture with an agriculturally acceptable diluent or carrier for use in controlling Chrysophtharta bimaculata.

The compositions of the invention can take any form known in the art for the formulation of agrochemicals, for example, a suspension, a dispersion, an aqueous emulsion, a dusting powder, a dispersible powder, an emulsifiable concentrate or granules. Moreover they can be in a suitable form for direct application or as a concentrate or primary composition which requires dilution with a suitable quantity of water or other diluent before application.

The concentration of the insecticidally active B. thuringiensis delta endotoxin in the compositions of the present invention when used alone or in combination with another pesticide, as applied to trees or other plants is preferably within the range from about 0.5 to about 25 per cent by weight, especially 1 to 15 per cent by weight.

The coleopteran active B. thuringiensis preparation or the compositions of the invention can be applied directly to the tree or other plant by, for example, spraying or dusting at the time when the pest has begun to appear on the tree or plant.

The preferred mode of application is by spraying. It is generally important to obtain

good control of pests in the early stages of pest development s this most effectively prevents defoliation or other crop damage.

The invention is illustrated in the following example showing a specific embodiment of this invention. The example should in no way be construed as limiting for the scope of the invention as defined in the appended claims.

EXAMPLES

In a number of field trials the product NOVODOR ^® FC was evaluated for its efficacy against the LI & L2 larval stages of the Tasmanian eucalyptus leaf beetle Chrysophtharta bimaculata. In the trial the insecticide was applied to various eucalyptus crops as indicated below:

The NOVODOR ^® FC product is an aqueous flowable concentrate formulated with microbial stabilizers, detergents and suspension aids.

Example 1

Product: NOVODOR ^® FC Pest: Chrysophtharta bimaculata Crop: Eucalyptus regnans 1 - 2 m tall Location: Westfield 100 Plantation site, Florentine Valley, Tasmania. Objective: To evaluate the efficacy of NOVODOR ^® FC against the larval stages of Chrysophtharta bimaculata under Tasmanian conditions

Application: Tractor mounted mistblower. 380 1/ha Trial design: 50 ha block: half sprayed with cypermethrin and half with

NOVODOR ^® FC

Dose: Product Dose/ha

NOVODOR ^® FC 5.0 liters cypermethrin 10 g ai/ha control Timing: Application took several days so some NOVODOR ^® treated trees may have received the treatment later than optimal Assessments: Random trees: eggs and larvae on 10 shoots/tree, precount and 25 shoots/tree post spray counts

Results: Product Dose/ha % reduction eggs and larva

NOVODOR ^® FC 5.0 77.8 cypermethrin 10 g 90.1 control

Comments: Surviving L3 and L4 NOVODOR ^® FC treated larvae appeared healthy, but their gegarious behaviour was disturbed. Treated areas were less defoliated than untreated control areas

Conclusion: NOVODOR ^® FC gave a reasonable control of early instar C. bimaculator larvae

Example 2

Product: NOVODOR ^® FC Pest: Chrysophtharta bimaculata Crop: Eucalyptus delegatensis established in 1983 Location: Smith Plains Plantation, Devonport District, Tasmania Objective: To evaluate the efficacy of NOVODOR ^® FC applied from the air against the larval stages of Chrysophtharta bimaculata under

Tasmanian conditions

Application: Helicopter application: 20 - 100 1 ha Trial design: Single block treatments

Dose: Product Dose/ha

NOVODOR ^® FC 5.0 liters cypermethrin 10 g ai control Timing: late december 1989 (20/12/89) Assesments: larval mortality Results: Product Dose/ha % mortality

NOVODOR ^® FC 5.0 1 87 cypermethrin 10 g 97 Conclusion: NOVODOR ^® FC gave good control of C. bimaculator larvae, when aerial application was adequately done

Example 3

Product: NOVODOR ^® FC

Pest: Chrysophtharta bimaculata

Crop: Eucalyptus regnans 1-2 m tall

Location: Westfϊeld 100 Plantation site, Florentine Valley, Tasmania. Objective: To evaluate the efficacy of NOVODOR ^® FC against the larval stages of Chrysophtharta bimaculata under Tasmanian conditions

Application: Motorised knapsack sprayer 930 1/ha Trial design: Randomise plot design: part rows with 2 rows between treatments Dose: Product Dose/ha

NOVODOR ^® FC 5.0 liters cypermethrin 10 g ai/ha cypermethrin 20 g ai ha control

Timing: early L2 on 30th November 1989 Assessments: The number of larval masses on each of 10 marked trees per plot.

Unmarked trees were destructively sampled to determine the average number of larvae per mass at both pre spray (29/11/89)

and post spray counts (4/12/89). The average increase in growth was assessed on the destructively sampled trees.

Results: Product Dose/ha % population av.increase reduction in growth cm

Comment: The assesment was probably too early to note the full effect of the treatment, which is apparent at 10 - 14 days

Conclusion: NOVODOR ^® FC gave a reasonable control of C. bimaculator larvae, and a worthwhile advantage growth over chemical treatments.