HETERORHABDITIS BACTERIOPHORA INSECTICIDE COMPOSITIONS AND RELATED PROCESSES

Abstract: Provided is an insecticidal composition comprising an effective amount of a juvenile infective-stage of insecticidal entomopathogenic Heterorhabditis bacteriophora hybrid strain Hb (NJ), or mutants or variants thereof and a biocompatible carrier therefor. The insecticidal compositions provided have improved insecticidal activity compared to known insecticidal compositions containing a known H. bacteriophora nematode HBHP88. Also disclosed is a process for reducing the population of soil-inhabiting insects in soil by applying to a soil locus infected with such insects the above-described insecticidal composition. Additionally, the Hb (NJ) hybrid nematode strain is provided.

Description: Heteror abditis Bacteriophora Insecticide Compositions and Related Processes FIELD OF INVENTION This invention relates to novel insecticide compositions comprising infective-stage heterorhabditid hybrid nematodes with enhanced insecticidal effectiveness, novel nematodes having said characteristics, and process for reducing soil-inhabiting insect pest populations by applying an effective amount of said insecticide composition to the infected locus. BACKGROUND OF INVENTION Insecticide compositions having as an ingredient a biological insecticide or entomopathogenic nematodes offer an attractive field of biological control agents for use against soil-inhabiting insect pests. They offer many important advantages over available chemical insecticides. Advantages of insecticide nematodes include high virulence, broad host range, safety, exemption from government registration and ease of mass production. Nematodes of the family Heterorhabditidae form a unique symbiotic association with Photorhabdus bacteria. They are pathogenic to a diverse group of insects. Heterorhabditids are hermaphroditic. In general, infective juveniles penetrate into the hemocoel of their host insects such as white grubs, usually through the gut or spiracles. Heterorhabditids have a dorsal tooth that might also facilitate penetration in other areas (e.g., intersegmental membranes). Bacteria from the digestive system of the nematodes are released within the host, and the host dies from septicemia, typically within 48 h. The nematodes feed, develop, mate and reproduce within the host cadaver, and, often after multiple generations, infective juveniles are again produced, emerge, and seek new host insects. It is desired to provide insecticide compositions comprising insecticide nematodes which provide improved effectiveness against soil-inhabiting insect pests, novel nematodes providing the improved effectiveness, and the process for controlling soil-inhabiting insect pests by use of such improved insecticide nematodes, and process and device for producing said improved insecticide nematodes. SUMMARY OF INVENTION Provided by this invention are novel insecticide compositions and an improved process for controlling soil-inhabiting insect pests by applying said novel insecticide composition having an effective amount of infective-stage entomopathogenic nematodes of this invention to the infested locus. The insecticidal compositions of this invention comprise an effective amount of a juvenile infective-stage of an insecticidal entomopathogenic nematode having insecticidal properties of Hete orhabdilis bacteriophora hybrid strain HB (NJ) and effective variants, mutants or hybrids thereof and a biocompatible carrier therefor. Also, provided by this invention are the novel entomopathogenic nematodes of the insecticidal compositions of this invention, which have high effectiveness in controlling soil-inhabiting insects including an increased pathogenicity to diverse insect hosts and an enhanced fecundity. DETAILED DESCRIPTION OF THE INVENTION The hybrid strain of Heterorhabditis bacteriophora HB (NJ) was attained by hybridizing a large series of wild-type isolates of H. bacteriophora obtained from soil samples collected from four different habitats. The habitats were turf, turf with scattered trees, weedy field and weedy field with scattered trees. The habitats represented many collection sites. The enhanced properties of the hybrid strain include enhanced patho¬ genicity or infectivity to diverse insect hosts and increased fecundity. Infectivity is determined by the following test. The standard test of infectivity used is to apply 50 infective juveniles to the top of a sand column (5 cm diameter x 5 cm high) with a target insect (the wax moth, GaUeria mellonella) at the bottom. The test is typically run at 25°C and the sand contains 10% moisture by weight. The nematodes are allowed 24 h to find the target insect and at that point the insect is removed, rinsed in distilled water and incubated for a further 24 h at 25 °C to allow the nematodes time to develop in the host. The host is then dissected and the number of nematodes that successfully established in the host is counted. In two tests of 20 replicates each, HB (NJ) had a mean infectivity rate of 10.45 and 11.1 nematodes per host (SE = 1.053 and 1.095 respectively) with all hosts having been infected and killed during the experiment. In comparable tests, the HB (NJ) strain showed results much superior to results of two known H. bacteriophora strains (HBNC and HBHP88). They killed only 50% and 70% of the hosts, respectively, and had mean infectivity rates of only 0.08 and 1.20 nematodes per host, respectively. Infectivity rates against other insects indicate similar superiority ofthe HB (NJ) strain. Fecundity is determined by the following test. The standard test of fecundity is to quantify the number of new infective juveniles produced from single hosts (GaUeria mellonella) of a standard weight (0.24-0.26 gms) and with a standard inoculation of infective juveniles (n = 20) at 25°C. For 30 replicates with HB (NJ), a mean fecundity level of 383,046.7 (SE = 15212.9) was obtained. Indications are that the fecundity of HB (NJ) is superior. The Heterorhabditis bacteriophora hybrid strain HB (NJ) provided by this invention has a deposit number of ATCC . The insecticidal compositions can be in the form of an aqueous spray composition, in the form of gel pellets or granules made using calcium alginate or other suitable carriers, in the form of a solid sheet, and the like. The carriers, which immobilize the nematodes or partially desiccate them, reduce their metabolism and improve their tolerance to temperature extremes. Nematodes are also commercially available on a moist substrate such as sponge, vermiculite, and peat, although extended storage at room tem¬ perature is generally poor because nematode viability declines rapidly. The Heterorhabditid compositions of this invention are suitably stored at 10°C- 15°C and the organisms should be maintained in the presence of oxygen. Nematodes can be applied with common agrichemical equipment including small pressurized sprayers, mist blowers, electrostatic sprayers, fan sprayers, and helicopters. Entomopathogenic nematodes can withstand appli¬ cation pressures of 300 lb/in 2 and can be delivered with all common nozzle type sprayers (e.g., "01 " nozzles) with openings as small as 50 microns in diameter. However, some types of pumping equipment produce a considerable amount of heat, and should the temperature in the sprayer plumbing rise above 32°C, the nematodes could be adversely affected. Fortunately, this rarely occurs and is usually only a problem when the spray tank is almost empty and little water is available as a heat sink. Field concentrations exceeding 2.5 billion nematodes/ha (1 billion/acre) are usually applied to ensure that a sufficient nematode population will come in contact with the target insects to provide control. A high concentration is needed to overcome the negative impacts of the abiotic and biotic soil environ¬ ment. High nematode concentrations are also needed against certain insects which only remain in soil for a few days before tunneling into roots, such as cabbage maggots (D. radicum), and against insects which are not highly sus¬ ceptible to nematode infection because of their small size and active movement. For example, high nematode concentrations are desirable against early immature stages of mole crickets (Scapteriscus spp.), root maggots (Delia spp.). and corn rootworms (Diabrotica spp.) An extensive discussion of formulation and application applicable to providing the insecticidal compositions of this invention and the processes of this invention is found in the treatise Entomopathogenic Nematodes in Biologi¬ cal Control, editors Randy Gaugler, Ph.D. and Haπy K. Kaya, Ph.D., Chapter 9. Formulation and Application Technology, by Ramon Georgis, CRC Press (Boca Raton, Ann Arbor, Boston), 1990. The GaUeria mellonella recognized test for evaluating insecticidal activity of nematodes is carried out as follows: Whatman No. 1 filter paper is placed in 35 mm petri dishes. A GaUeria mellonella host is placed on the filter paper. In 500 microliters of water, 100 juvenile nematodes are suspended. The aqueous suspension is placed on the filter paper by wetting the filter paper in several locations. If the GaUeria mellonella host has turned red at the end of the test period, this is a showing that the GaUeria mellonella host is dead. In the GaUeria mellonella bait method for isolating nematodes, the GaUeria mellonella infected with Heterorhabditis bacteriophora normally die and turn a red color. The soil samples taken are 2 cm in diameter and 15 cm in length. In providing the Heterorhabditis bacteriophora hybrid strain HB (NJ) of this invention, about 150 Heterorhabditis bacteriophora isolates were utilized. The crossbreeding used to provide the HB (NJ) strain involve conventional procedures. Changes and modifications of the invention provided will be apparent to those skilled in the art and to the extent they are within the spirit of this invention, are intended to be within the scope thereof.

Claims: What is Claimed is: 1. An insecticidal composition useful in reducing the population of one or more soil-inhabiting insects comprising an effective amount of a juvenile infective-stage of an insecticidal entomopathogenic nematode having insecticidal properties of Heterorhabditis bacteriophora hybrid strain Hb(NJ) or effective variants or mutants thereof and a biocompatible carrier therefor. 2. A composition of Claim 1 wherein the nematode is Heterorhabditis bacteriophora hybrid strain Hb(NJ). 3. A process for reducing the population of soil-inhabiting white grubs or other insects comprising applying to a soil locus infested with said insects an insecticidal composition comprising an effective amount of an infective- stage of an insecticidal entomopathogenic nematode having insecticidal properties of Heterorhabditis bacteriophora hybrid strain Hb(NJ)) or variants or mutants thereof. 4. A process of Claim 3 wherein the nematodes are the infective-stage of Heterorhabditis bacteriophora hybrid strain Hb(NJ) nematodes. 5. A nematode of Heterorhabditis bacteriophora hybrid strain HB (NJ) capable in the juvenile infective-stage of reducing the population of one or more soil-inhabiting insects when applied to the infested soil locus. 6. A juvenile infective-stage of the nematode of Claim 5.

Inventors: GAUGLER RANDY, STUART ROBIN, GAUGLER, RANDY, STUART, ROBIN
Applicants: UNIV RUTGERS, RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
Application year: 1996
Main classification: C12N5
IPC codes: A01K67, A01N63