Redlegged Earth Mite Halotydeus Destructor Research Articles

Effectiveness of spring spraying targeting diapause egg production for controlling redlegged earth mites and other pests in pasture

Earth mites are a complex of related species introduced into Australia in the early part of last century that cause economic damage to crops, especially canola, and to pastures. A general method of chemical control aimed at interrupting the life cycle at the most effective stage, by spraying in the spring before the mites enter diapause, has recently been adopted for controlling earth mites, particularly the redlegged earth mite Halotydeus destructor (Tucker). Here we use paired-paddock treatments and field enclosures to test the effectiveness of this method on pest populations of H. destructor as well as on other pests over two seasons at multiple pasture sites in Victoria. Halotydeus destructor numbers at the start of the winter growing season were suppressed by up to 85%, but this control level was not sustained. The numbers of H. destructor and other pests were similar to or higher than those in the unsprayed areas by spring. Spring spraying is, therefore, a useful means of suppressing H. destructor in early autumn, but its effects disappear relatively quickly over time in Victoria. This strategy also has little impact on the control of the blue oat mite Penthaleus major (Duges) and other phytophagous invertebrate pests.

Invertebrate pests of canola and their management in Australia: a review

Abstract In Australia, canola is subject to attack by at least 30 species of invertebrate pests, although the composition of this pest complex can vary between regions. Mites (e.g. the redlegged earth miteHalotydeus destructorand the blue oat mitesPenthaleusspp.), lucerne flea (Sminthurus viridis) and false wireworms (e.g. the grey false wirewormIsopteron punctatissimusand the bronzed field beetleAdelium brevicorne) are the major pests threatening the seedling establishment, whereas aphids (the cabbage aphidBrevicoryne brassicae, the turnip aphidLipaphis erysimiand the green peach aphidMyzus persicae), the native budworm (Helicoverpa punctigera), the diamondback moth (Plutella xylostella) and the Rutherglen bug (Nysius vinitor) can cause irregular and unpredictable damage to the flowering and podding plants. Current tactics of pest management for canola rely largely on the use of synthetic pesticides, but this single‐technology approach is likely to incur negative effects on natural enemies and the risk of pest resistance. Thus, the sustainable production of canola requires integrated pest management (IPM) strategies, in which cultural control, crop resistance and biological control are used as important components, with chemical inputs applied only when absolutely needed to restrict pests from reaching economically damaging densities. Such IPM strategies should be built around a fundamental understanding of pest ecology at both regional and local farm levels and the integration of renewable technologies. Therefore, future research efforts need to be focused on the canola‐cropping system, with a particular emphasis on the impact of pest species, natural enemies of the pests, varietal resistance to pests and the spatial ecology of pest species.

Predatory mites from crops and pastures in South Africa: potential natural enemies of redlegged earth mite Halotydeus destructor (Acari: Penthaleidae)

A survey was conducted in crops and pastures in the Western Cape Province of South Africa, in a search for predatory mites that could have potential for introduction into Australia as biological control agents of redlegged earth mite Halotydeus destructor (Penthaleidae). A total of over 1200 specimens was examined, and 56 species of predatory mites belonging to 14 families were found. Information is presented for 33 known species, including synonymy and bibliography, geographic distribution, and biology where known. Eight species in six families are described as new¨®Bdellodes edentata sp. nov. (Bdellidae), Hypoaspis calcarata sp. nov. (Laelapidae), Hypoaspis muellerae sp. nov. (Laelapidae), Macrocheles propinquus sp. nov. (Macrochelidae), Gamasiphoides lootsi sp. nov. (Ologamasidae), Gamasiphoides rykei sp. nov. (Ologamasidae), Pachylaelaps meganalis sp. nov. (Pachylaelapidae), and Rhagidia meyerae sp. nov. (Rhagidiidae). Fifteen species could not be fully identified because suitable specimens were not available. Of the 41 species that could be identified, nine are already present in Australia. A further 20 species are not known from Australia, but were rare in South Africa and therefore unlikely to be useful predators. Twelve species occurred in significant numbers in South Africa and are not known from Australia. Most of these are known or believed to be generalist predators, and are therefore unlikely to be approved for introduction into Australia. Chaussieria capensis (Anystidae) was considered to have potential and has been studied further. The survey did not identify any other species that were considered to be suitable as biological control agents.

Role of Alkaloids in Resistance of Yellow Lupin to Red-Legged Earth Mite Halotydeus destructor

Eleven varieties of Lupinus luteus were tested in choice and no-choice experiments for their resistance to feeding by the red-legged earth mite (Halotydeus destructor). Three were found to show resistance, and the alkaloid fraction from these varieties strongly deterred mites from feeding. The alkaloid components of the extracts, lupinine, a number of acyl derivatives of lupinine, and sparteine were tested for deterrent activity. Sparteine was the most potent, with significant activity at 0.001% concentration. Quantitation of the levels of nonpolar alkaloids in the cotyledons and leaves of the 11 varieties was by gas chromatography–mass spectrometry. An inverse correlation was found between the concentrations of these alkaloids and the damage caused by the mites; varieties with levels <100 μg/g (fresh wt) showed a high damage index. The involvement of sparteine and the bipiperidine alkaloid ammodendrine in the deterrence to mite feeding is discussed.

Cold storage of Halotydeus destructor (Acari: Penthaleidae) for use in experiments.

Survival of medium sized nymphal stages of redlegged earth mite Halotydeus destructor (Tucker) (mainly tritonymphs and deutonymphs) stored under low temperature (1.5 degrees C) in sealed plastic boxes remained more than 50% after 12 days of storage, with some mites surviving for up to eight weeks. Adding fresh subclover leaves into the storage box increased the survival rate of mites from 12% to 28%, 19 days after the storage started. Mites stored for two weeks at low temperatures showed feeding activity in a screening experiment similar to mites collected directly from the field. This indicated that cold storage of redlegged earth mite can be used to build up mite numbers for large screening experiments, or to extend the period of availability of mites collected from the field. However, their reproductive ability was greatly reduced after three weeks at low temperature. Thus, care should be taken when using mites for experiments measuring reproduction. The implications of low temperatures for reducing field populations of mites in midwinter are also discussed.

Role of isoflavonoids in resistance of subterranean clover trifoliates to the redlegged earth mite Halotydeus destructor

Mature leaves of variety SE014 of Trifolium subterraneum are resistant to the redlegged earth mite (Halotydeus destructor). Compounds with feeding deterrent activity present in the leaves were isolated and identified by using a membrane bioassay technique. The free isoflavones, formononetin, genistein, and biochanin A, their corresponding 7-O-glucosides, and biochanin A 7-O-glucoside-6″-O-malonate and genistein 7-O-glucoside-6″-O-malonate, were active. In addition, the biosynthetic precursors of formononetin and genistein, 2,5,7-trihydroxy-4′-methoxyisoflavanol and 2,5,7,4′-tetrahydroxyisoflavanol, also were deterrent to the redlegged mites. The relative activity of these compounds was determined and some structure-activity correlations are noted. The constitutive defense mechanism that contributes to the resistance of subclover trifoliates to the mite contrasts with the induced chemical mechanism previously found for subterranean clover cotyledons.