Degradation of lignified secondary cell walls of lucerne (Medicago sativa L.) by rumen fungi growing in methanogenic co-culture

Aims: To compare the abilities of the monocentric rumen fungi Neocallimastix frontalis, Piromyces communis and Caecomyces communis, growing in coculture with Methanobrevibacter smithii, to colonize and degrade lignified secondary cell walls of lucerne (alfalfa) hay. Methods and Results: The cell walls of xylem cylinders isolated from stems of lucerne contained mostly xylans, cellulose and lignin together with a small proportion of pectic polysaccharides. All of these major components were removed during incubation with the three fungi, and differing cell wall polysaccharides were degraded to different extents. The greatest dry weight loss was found with N. frontalis and least with C. communis, and scanning electron microscopy revealed that these extensively colonized different cell types. C. communis specifically colonized secondary xylem fibres and showed much less degradation than N. frontalis and P. communis. Conclusions: Neocallimastix frontalis and P. communis were efficient degraders of the cell walls of lucerne xylem cylinders. Degradation occurred of pectic polysaccharides, xylan and cellulose. Loss of lignin from the xylem cylinders probably resulted from the cleavage of xylan releasing xylan–lignin complexes. Significance and Impact of the Study: Unlike rumen bacteria, the rumen fungi N. frontalis, P. communis and C. communis are able to degrade lignified secondary walls in lucerne stems. These fungi could improve forage utilization by ruminants and may have potential in the degradation of lignocellulosic biomass in the production of biofuels.     

Effect of Cottony Snow Mold on Mortality and Biomass of Calamagrostis canadensis under Controlled-Environment Conditions

A low-temperature basidiomycete (LTB), the causal agent of cottony snow mold, was evaluated as a potential biological control agent for marsh reed grass (Calamagrostis canadensis [Michx.] P. Beauv.), a native grass of the North American boreal forest. Marsh reed grass and 2-year-old white spruce trees (Picea glauca [Moench] Voss) were inoculated with LTB and incubated for 12 weeks in a cold chamber to determine whether the fungus was pathogenic to these species. The fungus was not pathogenic to white spruce but was to marsh reed grass, causing 15% mortality and 64% reduction in dry weight of aboveground plant matter. In a second experiment, two clones of marsh reed grass were inoculated with an isolate of LTB and incubated for 8, 14, and 20 weeks in a cold chamber. Maximum response in the grass to the LTB treatment occurred after 20 weeks of incubation, with decreases of 97, 97, and 63%, respectively, in tiller number, dry weight of aboveground plant matter, and plant height. The LTB is a potential biological control agent of marsh reed grass.     

Effects of glycerol on the growth,adhesion, and cellulolytic activity of rumen cellulolytic bacteria and anaerobic fungi

The effect of glycerol on the growth, adhesion, and cellulolytic activity of two rumen cellulolytic bacterial species,Ruminococcus flavefaciens andFibrobacter succinogenes subsp.succinogenes, and of an anaerobic fungal species,Neocallimastix frontalis, was studied. At low concentrations (0.1–1%), glycerol had no effect on the growth, adhesion, and cellulolytic activity of the two bacterial species. However, at a concentration of 5%, it greatly inhibited their growth and cellulolytic activity. Glycerol did not affect the adhesion of bacteria to cellulose. The growth and cellulolytic activity ofN. frontalis were inhibited by glycerol, increasingly so at higher concentrations. At a concentration of 5%, glycerol totally inhibited the cellulolytic activity of the fungus. Thus, glycerol can be added to animal feed at low concentrations.     

Fructose-containing carbohydrates in the tuberous root of Gomphrena macrocephala St.-Hil. (Amaranthaceae) at different phenological phases

Gomphrena macrocephala St.-Hil. (Amaranthaceae) is a perennial herb that grows spontaneously in the cerrado and is characterized by well-defined phenological phases throughout the year. Soluble carbohydrates are the main reserve compounds of the tuberous root and constitute approximately 50% of the dry weight. These sugars were partially characterized as fructans forming a single homologous series, different from inulin, the most common fructan of dicotyledons. The mean molecular weight of polysaccharides was high and reached 37 kDa in the dormant phase. Fructan spherocrystals were detected in the tuberous root after treatment with ethanol, being associated with the parenchyma of secondary xylem. The content, composition and mean molecular weight of fructans were related to phenology. In late dormancy, there was a marked increase in monosaccharides, particularly fructose, and a concomitant decline of polysaccharides, probably as a result of fructan breakdown. During sprouting and in the vegetative phase, the contents of oligosaccharides and low molecular weight polysaccharides increased. A gradual rise in the molecular weight of polysaccharides occurred during the reproductive phase and at early dormancy, concurrently with decreasing levels of oligosaccharides. The capacity of G. macrocephala to accumulate readily accessible sugars, such as fructans, instead of starch, in response to environmental changes, may be of considerable advantage, since the cerrado is often subjected to seasonal drought and burnings.     

Best host‐plant attribute for species–area relationship,and effects of shade,conspecific distance and plant phenophase in an arthropod community within the grass Muhlenbergia robusta

Increased understanding of the species–area relationship (SAR) can improve its usefulness as a tool for prediction of species loss for biodiversity conservation targets. This study was conducted: (i) to determine the best plant attribute for the SAR in the community of arthropods living within the grass Muhlenbergia robusta; (ii) to determine the contribution of phenophases of plant foliage (dry and fresh), shade and conspecific distance to the variation in arthropod richness within the plant; (iii) to determine the best functional model of changes in the abundance, diversity and biomass in communities of arthropods in response to increases in plant size; (iv) to determine the best host‐plant attribute for prediction of these community attributes; and (v) to determine the effect of the plant phenophase, shade and M. robusta isolation on the abundance, diversity and biomass of the arthropod community. The above‐ground dry weight of grass was found to be the best host‐plant attribute for the SAR, while the light environment explained the arthropod richness within the grass, with higher richness observed in shaded environments. This study also showed that the best functional mathematical models for estimation of changes in the abundance, dry weight and diversity of arthropods in response to increases in grass size (dry weight) are the power model, exponential model and logarithmic model, respectively. Furthermore, the host‐plant foliage phenophase, shade and the isolation of M. robusta with other conspecifics had no effect on the abundance, biomass or diversity per basal area of the grass.     

The role of extracellular polysaccharides produced by the terrestrial cyanobacterium Nostoc sp. strain HK-01 in NaCl tolerance

The terrestrial cyanobacterium Nostoc sp. HK-01 was more tolerant to NaCl stress than the aquatic cyanobacterium Anabaena sp. PCC 7120 (also called Nostoc sp. PCC 7120) which is similar to Nostoc sp. HK-01 in phylogeny. We determined the amount of extracellular polysaccharides (capsular and released polysaccharides) from the cells of both strains cultured with or without 200 mM NaCl. The amount of capsular polysaccharides from Nostoc HK-01 reached approximately 65% of the dry weight whereas that from Anabaena PCC 7120 only occupied approximately 18% of the dry weight under NaCl stress. Anabaena PCC 7120 grew well under NaCl stress when both polysaccharides from Nostoc HK-01 were added to the culture. However, Anabaena PCC 7120 barely grew under NaCl stress when both of its polysaccharides were added. Extracellular polysaccharides from Nostoc HK-01 contained abundant fucose and glucuronic acid in comparison with those from Anabaena PCC 7120. Under NaCl stress, the composition ratios of sugars in the extracellular polysaccharides from Anabaena PCC 7120 hardly changed in comparison with those in ordinary culture conditions. By contrast, the composition ratios of sugars in the extracellular polysaccharides from Nostoc HK-01 changed under NaCl stress. These results suggest that the effect of extracellular polysaccharides from Nostoc HK-01 on NaCl tolerance comes from the increased amount of capsular polysaccharides, the sugar composition, and the change of the sugar composition ratio under NaCl stress.     

Phytoremediation Effect and Growth Responses of Cynodon spp. and Agropyron desertorum in a Petroleum-Contaminated Soil

In order to compare the petroleum tolerance and phytoremediation ability of a native grass, Agropyron desertorum (desert Wheatgrass) with Cynodon spp. (Bermuda grass) in a petroleum hydrocarbon-contaminated soil, a 7-month greenhouse experiment was performed. There were 4 soil treatments with 0% (uncontaminated soil), 2%, 4%, and 12% (w_oil/w_soil) petroleum concentration. Parameters including shoot and root fresh weight and dry weight, root penetration depth and root density depth, soil respiration, and total petroleum hydrocarbons (TPH) degradation were measured during and after experiments. The results showed an increase in shoot fresh weight of A. desertorum in soil polluted with 2% petroleum sludge compared to the uncontaminated soil, whereas the growth of Bermuda grass significantly decreased in corresponding treatment. Root growth of A. desertorum was decreased in 2% and 4% petroleum sludge, whereas it was increased in Bermuda grass species. Overall, root fresh weight of Bermuda grass was higher than that of A. desertorum in all treatments. Significant increase in microorganisms' activity was observed in the presence of petroleum sludge and plants in soil compared with uncontaminated soil without plants, and the highest soil respiration (37.6 mg C-CO₂/kg soil day) has been observed in the rhizosphere of Bermuda grass in treatment with 12% petroleum sludge. Plants had a significant role in the degradation of soil contaminants as TPH degradation in planted soils was significantly higher than that in unplanted soil (TPH degradation (%) was 30.4 and 38.9 in A. desertorum and Bermuda grass, respectively, whereas it was just 13.3 in unplanted soil). The rhizosphere of Bermuda grass had significantly less residual TPHs compared to A. desertorum. The results indicated that both Cynodon spp. and A. desertorum had a peculiar tolerance to petroleum pollution. Therefore, as Bermuda grass has already been suggested to be a typical and efficient species for phytoremediating petroleum-contaminated sites, A. desertorum may also prove to be a suitable native alternative.     

Weathering of134/137Cs following leaf contamination of grass cultures in an outdoor experiment

Summary After spraying grass cultures with rainwater collected after the Chernobyl reactor accident, the time-dependence of the weathering of leaf contamination of^134/137CS was determined. Hereby the influence of rain and of biomass increase due to growth was considered. Two effective half-lives were found of 6 d and more than 60 d in rain-protected grass for the activity per area (corresponding to 8 d and more than 60 d when related to the activity per dry weight) and 2 d and 30 d in rain-exposed grass for the activity per area (3 d and 23 d when activity per dry weight is considered). These half-lives represent the initially rapid (for about 90% of the activity) and later slow (for the residual about 10%) decrease of the Cesium content in grass. They might be due to different weathering mechanisms whereby the translocation of the radionuclides from the leaf surface into the plant interior and the loss of wax particles might be of importance.     

Efficacy of Exserohilum longirostratum on barnyard grass (Echinochloa crus-galli spp. crusgalli) under field conditions

An isolate of Exserohilum longirostratum obtained from Rottboelia cochinchinensis in Malaysia was highly pathogenic to barnyardgrass (Echinocloa crus-galli,) a serious weed in rice fields in Malaysia. In glasshouse trials, high levels of barnyardgrass control were achieved when E. longirostratum was applied as a conidial concentration at 10⁵ conidia/mL. This conidial concentration may not be sufficient for field use; therefore, a mini plot trial was carried out to assess the bioherbicidal potential of the fungus and the efficacy of different inoculum types under field conditions. Excellent barnyard grass disease as indicated by Area Under Disease Progress Curve (AUDPC) was achieved with mycelium (AUDPC = 583.8 unit²); mycelium + pretichlaclor (AUDPC = 610.4 unit²) and conidia alone (AUDPC = 468.3 unit²) compared to conidia + pretichlaclor (AUDPC = 395.8 unit²). Although conidia caused lower disease severity on barnyard grass compared to mycelium, this inoculum equally reduced the competition from barnyard grass as indicated by lower mean dry weight and fewer barnyard grass tiller numbers. Positive correlations between AUDPC of rice and its tiller number and AUDPC of rice and its dry weight were recorded while negative correlations were observed for the AUDPC of barnyard grass and its tiller number and AUDPC of barnyard grass and its dry weight. These findings confirmed that E. longirostratum applied either in the form of conidia or mycelium was effective against barnyard grass under field conditions.     

Fatty Acid and Chlorophyll Levels of Coastal Bermudagrass during the Day and during Maturation

Lipids were extracted from fresh, field-grown coastal bermudagrass (Cynodon dactylon (L.) Pers.) and the fatty acids determined by gas chromatography. Total fatty acid levels (dry weight basis) increased during the day and reached a single maximum at sunset in 2-week-old grass; whereas, in older grass, the fluctuations in fatty acid levels showed two maxima. The first maximum occurred 4 h after sunrise and the second maximum occurred at sunset. Total fatty acid levels, based on dry weight, decreased during the first 6 weeks of growth and changed very little after an additional 4 weeks' growth in bermudagrass leaf blades. Chlorophyll levels (dry weight basis) continuously decreased during the entire growth period (10 weeks). Chlorophyll alb ratios increased at sunset in 2- and 6-week-old grass, but this ratio did not change during the day in subsequent growth stages. The results of these experiments show that stages of maturity affected fatty acid fluctuations during the day as well as total fatty acid and chlorophyll levels in Coastal bermudagrass leaf blades. Chlorophyll alb ratios varied independently of fatty acid levels.     

Incidence of honeydew in southern pine-hardwood forests: implications for adult parasitoids of the Southern Pine Beetle,Dendroctonus frontalis (Coleoptera: Scolytidae)

The incidence of homopteran honeydew was measured under pines and hardwoods located within 10 Dendroctonus frontalis Zimmermann infestations on the Talladega National Forest (Alabama) during summer, 2000. There were more honeydew droplets beneath hardwood trees compared to pines, but no difference beween D. frontalis infested and uninfested pines. The number of honeydew droplets per tree differed between sampling dates, likely due to the effect of mean weekly temperature and rainfall on homopteran populations. The presence of honeydew on hardwoods may explain why D. frontalis parasitoids forage in areas that lack hosts and suggests that the fecundity of D. frontalis parasitoids may not be limited by adult nutrition.     

Stable isotope evidence for impala Aepyceros melampus diets at Akagera National Park,Rwanda

Stable isotope analysis of tooth enamel was used to investigate the relative proportions of grass and browse in seasonal and overall diets of impala Aepyceros melampus at Akagera National Park, Rwanda. Bulk enamel samples suggest that on average, impala ate c. 86% C₄ grass year‐round, far more than in most previously studied impala populations across Africa. Intra‐tooth samples show that seasonal changes in the proportion of C₄ grass versus C₃ browse are minimal (c. 10%), the diet being dominated by C₄ grass year‐round in contrast to other impala populations that consume ≥50% browse during the dry season. Intra‐tooth oxygen isotope values track carbon isotope changes to a moderate degree, but are not patterned clearly enough to permit identification of wet versus dry seasons. As other studies have shown that impala select high‐protein diets, the foraging behaviour at Akagera is probably because of the availability of palatable grass for much of the year in the edaphic grasslands around the lacustrine environments of the eastern portions of Akagera National Park.     

Functional biodiversity of lipids in Antarctic zooplankton: Calanoides acutus, Calanus propinquus, Thysanoessa macrura and Euphausia crystallorophias

Zooplankton samples were collected in January 1993 off Dronning Maud Land along a transect from open waters to the marginal ice zone close to the Antarctic ice shelf. Thysanoessa macrura was caught in open waters while Calanoides acutus and Calanus propinquus were mainly sampled between ice floes in the marginal ice zone. The “ice-krill”Euphausia crystallorophias was found over the shelf directly associated with ice floes. T. macrura had a lipid content up to 36% of its dry weight with the dominant lipid class, wax ester, accounting for 45–50% of the total lipid. The predominance of 18:1 fatty alcohols is the striking characteristic of the wax esters. Small specimens of E. crystallorophias had lipid levels up to 26% of their dry weight with, unexpectedly, triacylglycerols being the dominant lipid (up to 41% of total lipid). The small levels of wax esters in these animals (3–6% of total lipid) had phytol as a major constituent. Large specimens of E. crystallorophias had up to 34% of their dry weight as lipid, with wax esters (47% of total lipid) dominated by 16:0 and 14:0 fatty alcohols as the major lipid. Calanus propinquus had lipid levels of up to 34% of their dry weight, with triacylglycerols (up to 63% of total lipid) being the dominant lipid. High levels of 22:1 (n-9) fatty acid were present in the triacylglycerols. Calanoides acutus had lipid levels up to 35% of the dry weight with wax esters accounting for up to 83% of total lipid. High levels of (n-3) polyunsaturated fatty acids were recorded with 20:5(n-3), 22:6(n-3) and 18:4(n-3) being the dominant moieties. On the basis of their lipid compositions we deduce that: (1) Calanoides acutus is the strictest herbivore among the four species studied, heavily utilizing the typical spring bloom; (2) T. macrura is essentially omnivorous, probably utilizing the less defined bloom situations found in oceanic waters; (3) E. crystallorophias is an omnivore well adapted to utilize both a bloom situation and to feed on ice algae and micro-zooplankton associated with the ice; (4) Calanus propinquus seems to be the most opportunistic feeder of the four species studied, probably grazing heavily on phytoplankton during a bloom and, during the rest of the year, feeding on whatever material is available, including particulates, flagellates and other ice-associated algae. We conclude that the different biochemical pathways generating large oil reserves of different compositions, enabling species to utilize different ecological niches, are major determinants of biodiversity in polar zooplankton. Accepted: 22 June 1998     

Extraction of chitin and chitosan from larval exuvium and whole body of edible mealworm,Tenebrio molitor

The purpose of this study was to investigate the production of chitin and chitosan from both the exuvium and whole body of mealworm (Tenebrio molitor) larvae. Chitin from the exuvium and whole body of T. molitor larvae was chemically extracted with acid and alkali solutions to achieve demineralization (DM) and deproteinization (DP), respectively. The average DM (%) and DP (%) on a dry weight (DW) basis was 32.56 and 73.16% from larval exuvium, and 41.68 and 91.53% from whole body, respectively. To obtain chitosan, chitin particles from the exuvium and whole body of T. molitor larva were heated at various temperatures in different concentrations of NaOH. Average chitin yields were 18.01% and 4.92% of DW from the exuvium and whole body, respectively. The relative average yield of chitosan from whole body was 3.65% of DW. On average, over 90% of chitosan derived from whole body was deacetylated. The viscosity of chitosan from whole body was ranged from 48.0 cP to 54.0 cP. The chitin content of dry and wet byproducts from whole body were 17.32% and 16.94% respectively, compared to dry weight. The chitosan contents of byproducts on a DW basis were 14.48% in dry and 13.07% in wet byproduct. These results indicate that the exuvium and whole body of T. molitor larva may serve as a source of chitin and chitosan for use in domestic animal feed.     

Acetylene reduction assay on white clover genotypes and on grass/clover swards

Acetylene reduction assay was used to measure the nitrogenase activity of white clover genotypes in pots and of grass/clover swards in situ. Much of the variation in nitrogenase activity of single genotypes and hybrid populations was associated with plant dry weight. After adjustment for plant dry weight it was concluded that there was limited scope for selection for increased nitrogenase activity. In plant breeding this technique would seem to have greatest application in the selection for continued nitrogen fixation activity in the presence of inhibitory factors such as high levels of mineral nitrogen. The in situ studies revealed differences in nitrogenase activity of grass/clover swards based on contrasting cultivars of white clover. These differences were due to variation in clover density and also to variation in activity per unit clover dry weight. It was concluded that the variation in nitrogenase activity per unit dry weight reflected differences in growth pattern of the cultivars in the autumn when these assays were made. The in situ studies offer a means whereby the nitrogenase activity of cultivars and selected families can be monitored under varying levels of mineral nitrogen and other husbandry treatments without disruption of the sward.     

Biocontrol of Late Blight Disease (Phytophthora capsici) of Pepper and the Plant Growth Promotion by Paenibacillus ehimensis KWN38

For field application of a bacterial strain used to control Phythophthora capsici, we will need a biologically and economically efficient carrier medium. The known antagonist Paenibacillus ehimensisKWN38 was grown in a grass medium where it showed high antifungal and lytic enzyme activities. To demonstrate the potential of P. ehimensisKWN38 for biocontrol of late blight disease in pepper, pot trials were conducted by treating the 1‐month‐old plants with water (W), a selected grass medium (G3), G plus P. ehimensisKWN38 inoculation (G3P) or synthetic fungicide (F). The shoot dry weight in G3P was higher than that in W and F treatments at 15 days after zoospore infection (DZI). The root dry weight in G3P was also higher than that in W. The root mortality of G3 and W increased over 58 and 80% at 15 DZI, and some plants in those treatments wilted due to the failure of root physiology. The plants in G3P and F survived well because of their better root health conditions. Soil cellulase activity of G3P was consistently higher than that of W and F at earlier observation times (0, 2 and 6 DZI). The root β‐1,3‐glucanase activity of G3P promptly increased to maximum shortly after zoospore infection and reached the maximum value of 51.12 unit g^?1 of fresh weight at 2 DZI. All these results indicate that inoculation of P. ehimensisKWN38 to the root zone of potted pepper plants increases plant growth, root and soil enzyme activities and alleviates the root death caused by infection with P. capsici zoospores.     

Thermoregulation in four species of tropical solitary bees: the roles of size,sex and altitude

Body temperatures during free flight in the field, warm-up rates during pre-flight warm-up, and temperatures during tethered flight are measured for four tropical solitary bee species at three sites of differing altitude in Papua New Guinea. All four species are capable of endothermic preflight warm-up; three species give slopes of thoracic temperature on ambient temperature of significantly less than 1, indicating regulation of thoracic temperature. In the kleptoparasitic Coelioxys spp. (Megachilidae) and Thyreus quadrimaculatus (Anthophoridae), warm-up rates and thoracic temperatures in flight are low by comparison with the two provisioning species Creightonella frontalis (Megachilidae) and Amegilla sapiens (Anthophoridae). In both C. frontalis and A. sapiens thoracic temperatures correlate positively and significantly with both ambient temperature and body mass. In A. sapiens, body mass increases with altitude; this can be interpreted as a response to lower ambient temperatures at higher altitude, an example of Bergmann's rule. In both A. sapiens and C. frontalis populations at higher altitude have higher thoracic temperatures independent of differences of body mass, suggestive of additional morphological or physiological adaptation to lower ambient temperatures. In A. sapiens there is no qualitative difference in body temperatures between males and females after controlling for body mass, while male C. frontalis have significantly lower thoracic temperatures than females of the species. This difference between A. sapiens and C. frontalis is discussed with reference to variation in mating systems found in the Apoidea.Abbreviations C.R.I. Christensen Research Institute - P.N.G. Papua New Guinea - SFT stable flight temperature - T _a ambient air temperature - T _ab abdominal temperature - T _dif the temperature difference between thorax and abdomen - T _ex thoracic temperature excess - VFT voluntary flight temperature     

IMPORTANCE OF TIME OF GERMINATION AND SOIL DEPTH ON GROWTH OF PROSOPIS GLANDULOSA (LEGUMINOSAE) SEEDLINGS IN THE PRESENCE OF A C4 GRASS

In an investigation of the causes of the invasion of woody plants into grasslands, competition between seedlings of Prosopis glandulosa Torr. and Bouteloua curtipendula (Michx.) Torr. was examined. Introduction of P. glandulosa into a B. curtipendula neighborhood significantly reduced P. glandulosa dry mass when compared to P. glandulosa growth alone. The greater the time interval from P. glandulosa germination to addition of B. curtipendula, the less interference the grass had on woody plant growth. Reciprocally, the greater the time interval from B. curtipendula germination to addition of P. glandulosa, the more interference the grass had on woody plant growth. Prosopis glandulosa belowground dry mass was <0.02 g (all in the upper 30 cm of soil) when planted after B. curtipendula at any soil depth, but if planted alone its root dry mass ranged from 2 to 8 g depending on depth. Prosopis glandulosa seedling dry mass increased linearly with soil depth, while B. curtipendula dry mass reached a plateau. In general, belowground dry mass of P. glandulosa was distributed throughout the soil depth examined (decreasing with depth), while 80% of B. curtipendula dry mass was found in the upper 30 cm of soil, suggesting a partitioning of soil resources. Data suggest that P. glandulosa and perhaps other shade-intolerant woody species that establish in grasslands do so in disturbances or vegetation gaps. Gaps may close, but by this time woody plant roots are below grass roots, thus partitioning soil resources and reducing interspecific competition.     

Biology,demography and community interactions of Tarsonemus (Acarina: Tarsonemidae) mites phoretic on Dendroctonus frontalis (Coleoptera: Scolytidae)

1 Dendroctonus frontalis, the southern pine beetle, is associated with a diverse community of fungi and mites that are phoretic on the adult beetles. Tarsonemus ips, T. kranzti and T. fusarii (Acarina: Tarsonemidae) may interact within this community in ways that link the population dynamics of D. frontalis, the mites and three dominant species of fungi. We explored species associations by comparing the dietary suitability of different fungi for Tarsonemus spp. 2 All three mite species fed and reproduced at high rates when feeding on the bluestain fungus, Ophiostoma minus, which is an antagonist of D. frontalis larvae. 3 Mites also had positive population growth rates when feeding upon Ceratocystiopsis ranaculosus, one of the mycangial fungi, but could barely reproduce when feeding upon Entomocorticium sp. A, the mycangial fungus that is most suitable for D. frontalis. 4 During the time from colonization of a tree by D. frontalis adults until departure from the tree of their progeny (≈ 40 d at 30 °C), mite populations feeding upon O. minus can increase by factors of up to 209 (T. fusarii), 173 (T. ips) or 384 (T. krantzi). These high growth rates are allowed by rapid development (age of first reproduction = 8–9 d), high fecundity (≈ 1 egg/d) and high longevity (> 28 d). 5 Precocious mating increases the chance that females are mated prior to colonizing a new tree and arrhenotokous parthenogenesis permits reproduction by unmated females. 6 Tarsonemus mites may introduce negative feedback into D. frontalis population dynamics by generating indirect interactions between D. frontalis and O. minus.