Earth Mite Research Articles

Feeding by redlegged earth mite (Halotydeus destructor) on seedlings influences subsequent plant performance of different pulse crops

Damage caused by redlegged earth mite to seedlings of 6 pulse species and its effect on subsequent plant growth and grain yield were examined under controlled and field conditions. Seedling damage caused by redlegged earth mite affected subsequent plant growth and reduced seed yield, but the responses varied among different pulse species. Field pea and yellow lupin were the most susceptible at seedling stage and flowering, but only yellow lupin suffered significant reduction in grain yield (30%) in the field. Narrow-leafed lupin suffered moderate damage, faba bean slight damage, while chickpea and lentil suffered little or no damage. The practical implications of these results are discussed.

Effect of seedling damage by redlegged earth mite, Halotydeus destructor, on subsequent growth and development of yellow lupin, Lupinus luteus, in the glasshouse

Redlegged earth mite (Halotydeus destructor) causes feeding damage to some pulse species at the seedling stage. To quantify the effect of this damage on subsequent plant growth and development, an experiment was conducted in the glasshouse using yellow lupin, Lupinus luteus cv. Motiv, which is highly susceptible to the mites. After emergence, plants were infested with 0, 100, 150, and 250 mites/plant, collected from the field. Fourteen days after application, mites were removed. Damage to plants was estimated at seedling stage, flowering time, and maturity. At seedling stage (on Day 14), feeding damage scores to cotyledons and true leaves were greater at higher mite densities. Damaged plants produced fewer nodules, fewer lateral roots, and less dry weight than the control. On Day 35, severely damaged plants failed to recover and on the surviving plants, cotyledons and true leaves died earlier than on the plants without damage. On Day 78, when plants were flowering, the surviving plants produced fewer nodules and branches, and less dry weight per plant than the control. The flowering time of plants with the mite treatments was delayed by up to 6 days compared with the controls. The final shoot dry weight, pod number, seed number, and seed yield per pot were significantly reduced by the mite treatments. Feeding by H. destructor on seedlings of yellow lupin caused a reduction in seed yield of 58% at the highest mite density treatment. This significant economic loss needs to be confirmed under field conditions, but it signifies the need to develop appropriate control measures for this pest.

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.

Volatiles from Trifolium as feeding deterrents of redlegged earth mites

Abstract The volatile compounds produced by the leaves of Trifolium glanduliferum , T. strictum and T. subterraneum were collected by trapping on Tenax TA adsorbent and the major components were identified by GC–MS. The volatiles obtained from T. glanduliferum and T. strictum were shown to deter the redlegged earth mite ( Halotydeus destructor ) from feeding, whereas those from T. subterraneum did not. β-Ionone and coumarin, detected in the volatiles of T. glanduliferum , T. strictum , showed strong deterrent activity at 100 ppm. Phenylethanol, a component of the volatiles of T. strictum , was inactive.

The biology of Penthaleus species in southeastern Australia

AbstractEarth mites are major pests of pastures and crops within southern Australia. While the biology and ecology of the redlegged earth mite (Halotydeus destructor) have been studied extensively, the blue oat mite (Penthaleus major) and its recently discovered relative, Penthaleus falcatus, have received little attention. The distribution of H. destructor, P. major and P. falcatus is described in Victoria, Australia, and the inland borders in central New South Wales are re‐described. A new undescribed Penthaleus species identified from mallee samples is recognized, and its restricted distribution in Victoria is mapped. Electrophoretic data and the complete absence of males indicate that all Penthaleus species are obligate thelytokous parthenogens. The three Penthaleus species differ in clonal diversity. All species are pests of pastures and/or crops, however the preferred plant hosts of P. major and P. falcatus differ. Tolerance of a commonly used pesticide (omethoate) differs between the species. P. falcatus shows the highest LC50, and may be responsible for pesticide control failures. Rearing methods for P. major and P. falcatus are described. The large differences between these blue oat mite species point to difficulties in interpreting early published data that failed to distinguish them.

Levels of isoflavonoids as indicators of resistance of subterranean clover trifoliates to redlegged earth mite Halotydeus destructor

The extracts, obtained with methanol from crushed trifoliates and from the surface layer of the trifoliates, contained isoflavones in both the free and bound forms as the major components, compounds known to exhibit feeding deterrence towards the redlegged earth mite. The levels of these compounds were quantified and showed considerable variation in extracts of one susceptible variety and four varieties with differing levels of resistance. The relative resistance of the five varieties established from field observations was compared with the amounts of isoflavone derivatives obtained in the two extracts. A better ranking of resistance was found with levels of isoflavones on the leaf surface than with the total amount of isoflavones in the trifoliates. These results suggest a simple method for determining the relative resistance of subterranean clover to the mite.

European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), as a predator of the redlegged earth mite, Halotydeus destructor (Tucker) (Acarina: Penthaleidae)

The European earwig, Forficulaauricularia L., consumed the redlegged earth mite, Halotydeusdestructor (Tucker), under laboratory conditions. Although female earwigs consumed more mites at the lowest density of 25 mites per petri dish, there was no difference between males and females at the two higher densities of 50 and 75 mites per dish. The addition of vermiculite to the dish to simulate habitat diversity had a negative impact on the consumption rate.

Efficacy of insecticides against the lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae), and other arthropods in lucerne

AbstractNine insecticides were evaluated in lucerne for control of the lucerne flea, Sminthurus viridis. Carbaryl, chlorpyrifos, omethoate and isofenphos were the most effective. Each gave immediate control and the highest levels of persistence. Efficacy data of the insecticides against aphids, leafhoppers, earth mites and total numbers of predators are also given. Omethoate and chlorpyrifos were the most effective chemicals overall, although further information on their effects on the predator complex is required to support their recommendation. Carbaryl and fenvalerate showed promise for differentiating between damage by three major pests.

Efficacy of insecticides against the lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae), and other arthropods in lucerne

Nine insecticides were evaluated in lucerne for control of the lucerne flea, Sminthurus viridis. Carbaryl, chlorpyrifos, omethoate and isofenphos were the most effective. Each gave immediate control and the highest levels of persistence. Efficacy data of the insecticides against aphids, leafhoppers, earth mites and total numbers of predators are also given. Omethoate and chlorpyrifos were the most effective chemicals overall, although further information on their effects on the predator complex is required to support their recommendation. Carbaryl and fenvalerate showed promise for differentiating between damage by three major pests.

Soil microflora as hosts of redlegged earth mite (Halotydeus destructor)

Soil microflora as hosts of redlegged earth mite (<i>Halotydeus destructor</i>)

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.

Host Plant Acceptance by Redlegged Earth Mite, Halotydeus destructor (Tucker) (Acarina: Penthaleidae)

Host plant acceptance behavior of redlegged earth mites (Halotydeus destructor) on cotyledons of subterranean clover (subclover) lines was investigated in the laboratory. Sustained feeding consisted of a series of short bouts of feeding; rather than one long period of feeding. H. destructor preferred to feed at mite-damaged rather than undamaged sites on cotyledons. With time the numbers of mites feeding in aggregations increased, as mites were attracted to damaged patches. Most feeding occurred in aggregations, and mites in such groups benefited by greater weight gain. The sequence of foraging leading to feeding was similar between subclover lines, however, feeding and aggregation activities were markedly reduced on a resistant line. Host plant acceptance occurred during probing but only after some feeding had occurred.

Resistance of seedling white clover cultivars to redlegged earth mite &lt;i&gt;Halotydeus destructor&lt;/i&gt;

Two glasshouse pot bioassays were conducted in Perth, Western Australia, in 1994 which compared the seedling resistance of subterranean clover (Trifolium subterraneum L.) with New Zealand white clover (Trifolium repens L.) cultivars ‘Grasslands Huia’, ‘Grasslands Tahora’, ‘Prop’, ‘Grasslands Pitau’ and ‘Grasslands Kopu’ to redlegged earth mite (Halotydeus destructor) (Acarina: Penthaleidae). Plant wet weights, mite development and survival and plant damage scores were monitored. Subterranean clover was more resistant to redlegged earth mite than white clover in both experiments. The white clover cultivars, ‘Grasslands Pitau’ and ‘Grasslands Kopu’ had lower cotyledon damage scores and higher yields than the other white clover cultivars.

Seasonal occurrence and abundance of redlegged earth miteHalotydeus destructor(Acari: Penthaleidae) in annual pastures of southwestern Australia

AbstractSeasonal occurrence and abundance of redlegged earth mite,Halotydeus destructor(Tucker), was measured by weekly sampling in grazed annual pastures near Keysbrook (1990–1992) and Narrogin (1991–1992) in southwestern Australia. Mites were active for 27 weeks from the late autumn (May) to mid-spring (October), completing three generations at approximately 8 week intervals. The summer is spent as diapause eggs in the cadavers of adult female mites. In 1991 and 1992, activeH. destructorwas on average twice as abundant at Keysbrook (mean 11,300 mites/m2), as at Narrogin (mean 6400 mites/m2). Three times more eggs were laid at Keysbrook than Narrogin (mean 8500 and 2900 eggs/m2respectively). Rainfall at Keysbrook was twice that at Narrogin, and temperatures were higher. We suggest that the rate of oviposition was less at Narrogin, probably because of resource limitation. The mature adult sex ratio was female biased, but was lower at Keysbrook (0.669) than at Narrogin (0.813).Neozygites acaridis, a fungal disease, was detected in less than 4% of the population, mainly in adult mites in late spring. Rainfall and temperatures were lower in the spring of 1992 than 1991 at both sites. Pasture was grazed considerably shorter in the spring of 1992, and numbers ofH. destructorwere lower, but numbers of eggs laid in the two years were similar. We suggest that active mite mortality was greater in spring of 1992, probably due to lower relative humidity. There were fewer adult mites in spring, and fewer diapausing eggs in summer at both sites in 1992 (36,600 diapause eggs/m2) than in 1991 (148,000 diapause eggs/m2). It is proposed that controlling mites in spring should lead to lower numbers of diapause eggs in summer and of mites emerging in autumn.

The response of the major crop and pasture pest, the red-legged earth mite (Halotydeus destructor) to pesticides: dose-response curves and evidence for tolerance

We describe an assay for testing the response of the adult red- legged earth mite, Halotydeus destructor, to pesticides. This assay is used to generate dose response curves for an organophosphate (omethoate) and an organochlorine (endosulphan) commonly used to control these mites, as well as a synthetic pyrethroid (alfamethrin). Comparisons of the populations from five sites around Victoria indicated tolerance to omethoate. A heritable basis for the tolerance was demonstrated by comparing the stocks after they had been reared under laboratory conditions for a generation. No tolerance of endosulphan was detected, although this chemical was not used heavily at any of the sites. Some tolerance of alfamethrin was also suggested. These results suggest that alternative methods for controlling this pest will eventually need to be considered.

Mass rearing Halotydeus destructor (Tucker) (Acari : Penthaleidae) for use in summer screening of Trifolium subterraneum (L.) for mite resistance

Summary. Controlled environment experiments were conducted to establish some of the requirements for successful mass rearing of Halotydeus destructor (redlegged earth mite). Numbers of mites reared on Vicia sativa (common vetch) cv. Blanchefleur grown alone or on a mixture of vetch with Trifolium subterraneum (subterranean clover) cv. Goulburn, were significantly higher than those on subterranean clover or Arctotheca calendula (capeweed) alone. Populations reared on vetch grown in a sandy soil were significantly higher than those reared on vetch grown in a loamy soil, pure sand or pure loam. Covering the soil surface with a natural pasture mulch increased mite numbers compared with leaving the soil bare or placing plant pots inside ventilated cages. Subsequent changes in rearing methodology produced enough mites to enable summer screening of subterranean clover lines for resistance to H. destructorfor the first time. Over 20 000 mites can be produced from vetch at one time for screening tests throughout the year.

The Effect of Volatile Metabolites of Lipid Peroxidation on the Aggregation of Redlegged Earth Mites Halotydeus destructor (Acarina: Penthaleidae) on Damaged Cotyledons of Subterranean Clover

Redlegged earth mites (Halotydeus destructor) aggregated in larger numbers on cotyledons of subterranean clover (Trifolium subterraneum L.) previously damaged either by mite feeding or by mechanical injury than on undamaged cotyledons. This effect lasted for up to 7 days. The total volatile fractions derived from crushed cotyledons and its three major components, 2-(E)-hexenal, 1-octen-3-ol, and 1-octen-3-one, were tested for their effect on the aggregation of mites. Significantly more mites gathered on detached cotyledons treated with the metabolites at low concentrations than on controls, with 2-(E)-hexenal being the most effective. Mites were repelled by higher concentrations of the metabolites and 1-octen-3-one, the most active, killed mites at high concentrations. Fewer mites aggregated on DGI007 (resistant) than on Dalkeith (susceptible) cotyledons treated with droplets of the metabolites. The three volatile metabolites were recovered from the headspace of undamaged and of damaged cotyledons. Crushed cotyledons of Dalkeith produced higher levels of 2-(E)-hexenal and lower levels of 1-octen-3-one than undamaged cotyledons. The results suggest that damage-induced metabolites enhance the aggregation of redlegged earth mites at low concentrations and reduce aggregation at high concentrations.

Pathogenesis-Related Proteins in Trifolium subterraneum: A General Survey and Subsequent Characterisation of a Protein Inducible by Ethephon and Redlegged Earth Mite Attack

One of the chief predators of subterranean clover (Trifolium subterraneum) pastures is redlegged earth mite (Halotydeus destructor; RLEM). Subterranean clover pathogenesis-related (PR) proteins induced by RLEM attack and ethephon treatment were surveyed, and PR proteins with peroxidase, β-1,3-glucanase and chitinase activities were detected. A protein co-migrating with a chitinase activity, induced by RLEM predation and treatment with ethephon, was isolated. It was purified and the N-terminal amino acid sequence determined. Using a degenerate oligonucleotide primer designed from this sequence, a corresponding cDNA fragment was amplified by reverse transcriptase-PCR, then cloned, and used as a probe to screen a subterranean clover cv. Karridale genomic library. The cDNA and a 97% homologous genomic clone were sequenced and the deduced amino acid sequence revealed an open reading frame of 157 amino acids capable of encoding a peptide of 16 478 Da. Significant homology (80%) was found between this protein and an abscisic acid (ABA)-responsive protein from Pisum sativum of unknown function which is an intracellular pathogenesis-related (IPR) protein. The gene encoding this protein also has homology to pea ‘disease response resistance genes’ and to proteins from other plant species in the PR-10 family. The induced protein was designated TsPR-10a due to its homology to other PR-10 proteins. Genomic Southern analysis indicates that the gene encoding this protein, designated Ypr10a, is a member of a multigene family with at least three members. Northern blot analysis indicates that the subterranean clover Ypr10a mRNA, or homologous transcript, level is strongly induced by ethephon treatment in both root and aerial tissues of 3 week old plants. The rapid induction kinetics of Ypr10a mRNA under ethephon treatment, its correlation with a putative chitinase activity, and homology to other PR-protein genes, suggests a pathogenesis-related role for TsPR-10a protein in subterranean clover.

Examination of the involvement of mechanical strength in antixenotic resistance of subterranean clover cotyledons to the redlegged earth mite (Halotydeus destructor) (Acarina: Penthaleidae)

AbstractResistance involving penetrability of cotyledons of subterranean clover Trifolium subterraneum (Leguminosae) by the redlegged earth mite, Halotydeus destructor Tucker, was examined in this study using several approaches. Values of penetrability, presented as mechanical strength measured with a penetrometer with a tubulated probe, of cotyledons tested 11–13 days after seeding, from nine varieties of two subspecies of subterranean clover (T. subterraneum subsp. yanninicum and subsp. brachycalicinum) were negatively correlated with feeding damage caused by H. destructor in both 3 h pairwise choice tests in a Petri dish with detached cotyledons, and in 2 week multiple choice tests in containers with seedlings. Simulation tests with different artificial membranes (Parafilm and Gladwrap) making up sachets, containing 5% glucose as a feeding stimulant, indicated that within 3 h H. destructor preferred membranes with lower strength. Field-collected young adults had significantly higher physical fitness to feed and/or gather on the artificial membrane sachet containing 5% glucose, than those from the laboratory culture, when the sachet was compared with cotyledons of either resistant (DGI007) or susceptible (Dalkeith) varieties in the choice tests. Electron microscopic observations of mite infested cotyledons of the resistant variety (DGI007) reveal that upper epidermal cell walls around penetration holes are bent inwards. Anticlinal cell walls of palisade cells appear buckled following attack by H. destructor. The results from these studies were taken as further evidence for the involvement of mechanical factors in antixenotic resistance of subterranean clover cotyledons to H. destructor.

The foraging behaviour of redlegged earth mite,Halotydeus destructor(Acarina: Penthaleidae), in an annual subterranean clover pasture

AbstractThe foraging behaviour of the redlegged earth mite,Halotydeus destructor(Tucker), in annual pasture was documented and the relative numbers of individuals foraging on subterranean clover,Trifolium subterraneum(Leguminosae), capeweed,Arctotheca calendula(Compositae) and grasses (mainlyLolium rigidum(Gramineae)), estimated in winter and spring in south-western Australia. The main feature ofH. destructorforaging behaviour was the presence of aggregations ranging in size from 3–36 individuals on the adaxial surfaces of the upper canopy of the pasture. Most aggregating individuals were feeding, while most solitary and paired individuals were searching. There was no evidence that individuals aggregated for reproductive behaviour; the adult sex ratio was similar to that of the population even though immatures were under-represented in aggregations. During winter the distribution of numbers ofH. destructoron subclover, capeweed and grasses in the upper canopy of pasture was similar to the estimated ground cover of these plant species. However, individuals showed host-plant selection for subclover when feeding. During spring, when the pasture plants were flowering, there were moreH. destructorin capeweed flowers than in aggregations on subclover foliage. The capeweed flowers were shown to enhance the rate ofH. destructorreproduction in a laboratory experiment. MostH. destructorwere on or near the soil surface, with 10% at any one time on the upper canopy of the pasture.H. destructoris polyphagous, and behaved in pasture as a selective opportunist feeder.