Attack rate and prey preference of Lasioseius subterraneous and Protogamasellus mica on four nematode species.

Plant parasitic nematodes are common and important global pests, causing over US$150 billion in crop losses across the agricultural sector worldwide. Meloidogyne javanica and Pratylenchus zeae are two of the most damaging plant-parasitic nematodes and there are limited options for their control. We evaluated the potential of a large (Lasioseius subterraneous) and a small (Protogamasellus mica) mesostigmatan mite as biological control agents of plant-parasitic nematodes. We tested the attack rate and reproductive potential of these two mite species on four nematode species: M. javanica (eggs), Pra. zeae (adults) and two microbivorous nematodes, Mesorhabditis sp. and Aphelenchus avenae (adults for both species). Each mite/nematode combination (1 mite:100 nematodes) was tested in six replicate arenas. In a separate trial, each mite species was presented with 50 A. avenae and 50 Pra. zeae in the same arena to determine prey preference. Both mite species significantly reduced the abundance of all nematode species used in the trials when compared to nematode-only controls. Lasioseius subterraneous consumed all available M. javanica eggs within 72 h. The larger mite had a significantly higher overall attack rate than the smaller mite, each consuming an average of 96 and 72 nematodes, respectively, within 72 h. However, both mites had a similar reproductive rate. Protogamasellus mica displayed a positive preference towards the plant parasitic nematode Pra. zeae over the fungal feeding A. avenae whereas L. subterraneous did not display a prey preference. Our results highlight the potential of these two predators to control plant parasitic nematodes, although further trials under field conditions are needed.

Optimizing Generic Cerambycid Pheromone Lures for Australian Biosecurity and Biodiversity Monitoring.

The cerambycid beetles comprise a diverse family that includes many economically important pests of living and dead trees. Pheromone lures have been developed for cerambycids in many parts of the world, but to date, have not been tested in Australia. In this study, we tested the efficacy of several pheromones, identified from North American and European species, as attractants for cerambycids at three sites in southeast Queensland, Australia. Over two field seasons, we trapped 863 individuals from 47 cerambycid species. In the first season, racemic 3-hydroxyhexan-2-one was the most attractive compound among the eight pheromones tested. Subsequently, we aimed to optimize trapping success by combining this compound with other components. However, neither the addition of other pheromone components nor host plant volatiles improved the efficacy of 3-hydroxyhexan-2-one alone. We also tested a generic pheromone blend developed for North American cerambycids, and found that only the combination of this blend with host plant volatiles improved trapping success. The Australian cerambycid fauna is not well known, and effective lures for use in trapping beetles would greatly assist in the study of this important group. Effective semiochemical lures would also have implications for biosecurity through improved monitoring for invasive species.

Geographical variation, population structure and gene flow between populations of Chrysophtharta agricola (Coleoptera: Chrysomelidae), a pest of Australian eucalypt plantations.

Chrysophtharta agricola (Chapuis) is a pest of commercial eucalypt plantations in Tasmania and Victoria. Vagility of pest populations may result in difficulty predicting temporal and spatial pest outbreaks, and influence genetic resistance to chemical control. Gene flow in this pest species was estimated to assess predictability of attack, the potential efficacy of natural enemies, and the likelihood of resistance build-up. Ten geographic populations of C. agricola (six from Tasmania, one from the Australian Capital Territory, one from New South Wales and two from Victoria) were examined for genetic variation and gene flow using cellulose acetate allozyme electrophoresis. Six enzyme systems (PGI, PGD, PGM, IDH, HEX and MPI) were consistently polymorphic and scorable and were used to quantify estimated gene flow between populations. FST values and analysis of molecular variance indicated that gene flow was restricted between populations. Chrysophtharta agricola exhibited high levels of heterozygosity, probably because of high allelic diversity, and because all loci examined were polymorphic. The southern-most population was the most genetically different to other Tasmanian populations, and may also have been the most recently colonized. Limited gene flow implies that outbreaks of C. agricola should be spatially predictable and populations susceptible to control by natural enemies. Our results also imply that genetic resistance to chemical control may occur under frequent application of insecticide. However, testing population movement between plantations and native forest also needs to be conducted to assess gene flow between forest types.