Short Communication Anti-tick effects of Stylosanthes humilis and Stylosanthes hamata on plots experimentally infested with Boophilus microplus larvae in Morelos, Mexico

The anti-tick effects of the tropical pasture legumes Stylosanthes humilis and Stylosanthes hamata were evaluated and compared with two common grasses, Cenchurus ciliaris and Andropogon gayanus, in the state of Morelos, Mexico, on plots experimentally infested with larvae of the tick Boophilus microplus. The effect was evaluated by recovery of larvae from the experimental plots by flagging during a 4 week period. The anti-tick effect due to Stylosanthes was significantly higher for S. humilis and S. hamata (p < 0.05) and slightly better for S. humilis (3% survival) than for S. hamata (12% survival). Further studies are required to determine the potential role of Stylosanthes plants for tick control in Mexico. © Rapid Science Ltd. 1998     

Population and clonal level responses of a perennial grass following fire in the northern Chihuahuan Desert

Relationships involving fire and perennial grasses are controversial in Chihuahuan Desert grasslands of southern New Mexico, USA. Research suggests that fire delays the resprouting of perennial grasses well after two growing seasons. However, such results are confounded by livestock grazing, soil erosion, and drought. Additionally, post-fire grass responses may depend on initial clone size. We evaluated the effects of fire, grazing, and clone size on Bouteloua eriopoda (black grama) in southern New Mexico grasslands. Four 2-ha plots were established in each of four sites. Fire and grazing were applied or not applied in 1999 such that four treatment combinations were assigned randomly to plots within each site. Within each plot, small (0–10 cm² basal area), medium (10–30 cm²), and large ( > 30 cm²) clones were initially mapped in five 0.91-m² quadrats where grass attributes and litter cover were evaluated before and at the end of two growing seasons following fire. Maximum fire temperature was also measured. At a population level, canopy and litter cover were each approximately 50% less in burned than unburned areas. However, compared to initial levels, canopy height had increased by 10% at the end of the study, regardless of fire. At a clonal level, basal cover reductions were attributed mostly to large clones that survived fire. Smaller clone densities had decreased by as much as 19% in burned compared to unburned areas, and fire reduced the basal cover of medium clones. Basal and canopy cover, recruitment, and clone basal area decreased with increased fire temperatures. Almost all responses were independent of grazing, and interactive effects of grazing and fire were not detected. Fire did not kill all perennial grass clones, regardless of size. However, rapid responses were likely influenced by above-average precipitation after fire. Future studies in desert grasslands should examine how perennial grass dynamics are affected by fire, precipitation patterns, and interactions with grazing.     

Balance of Competitive and Facilitative Effects of Exotic Trees on a Native Patagonian Grass

The balance between facilitation and competition in plants changes with species characteristics and environmental conditions. Facilitative effects are common in natural ecosystems, particularly in stressful environments or years. Contrarily, in artificial associations of plants, such as agroforestry systems, some authors have suggested that even when facilitative effects may occur, net balance of tree effects on grasses is usually negative, particularly in dry environments. The aim of this study was to determine the net effect of the exotic ponderosa pine on the native grass Festuca pallescens (St. Ives) Parodi in agroforestry systems in Patagonia. Soil water content, plant water status, and relative growth were measured in the grass growing in different treatments (determined by tree cover level) during two growing seasons with contrasting climatic conditions. Facilitative effects of trees over grass water status were recorded only when water availability was high. A net negative effect was detected on dates when soil water content was very low and evaporative demand was high. The strength of these negative effects depended on tree density and climatic conditions, being higher in treatments with lower tree canopy cover. These results indicate that the positive effect of trees could only be expected under relatively low stress conditions. However, relative growth of grasses was always similar in plants growing in forested plots than in open grassland. Differences in biomass allocation for grasses growing in shade and open habitats may reconcile these contrary results. Our results highlight the importance of the physiology of a species (relative drought and shade tolerance) in determining the response of a plant to a particular interacting species.     

Disturbance,drought and dynamics of desert dune grassland,South Africa

A seven-year study of marked plants and plots in Stipagrostis ciliata (Desf.) de Winter dune grassland, in the arid (<100 mm yr^–1) Bushmanland area of the Northern Cape province of South Africa, was designed to test the hypothesis that establishment of ephemeral plants, and recruitment of perennial grasses was dependent upon disturbances that reduced the density of living perennial grass tussocks. In 1989, eight 4 m² plots were cleared of perennial vegetation by uprooting and removing all plants so as to resemble small-scale disturbances made by burrowing mammals or territorial antelope. The vegetation on the cleared plots and surroundings was monitored until 1996. Initial results supported our hypothesis. In wet years, when ephemeral plants were abundant, their average fresh mass was 2–3 times greater per unit area on the cleared plots than in control plots in adjacent, undisturbed grassland. Many Stipagrostis seedlings established in the cleared plots over the two years following clearing but were rare in adjacent areas among established conspecifics. However, a drought in 1992 (11 mm of rain over 12 months) lead to widespread mortality of the perennial grass, killing 56% (range 22–79%) of established tufts. High densities of Stipagrostis seedlings appeared following the drought-breaking rains in January 1993, both in the disturbed plots and in the surrounding `undisturbed' dune grassland. Ephemeral plants established in large numbers throughout the area during the high rainfall year of 1996 and were generally more numerous in the old disturbances than in control plots. Seven years after clearing the biomass of grass on the cleared plots was approximately 34% of the mass removed from the plots in 1989 whereas in the undisturbed grassland biomass was 66% of 1989 levels. Drought had little long-term effect on community composition, and Stipagrostis ciliata constituted 94–98% of plant community before and after drought. Cleared plots were recolonised by S. ciliata, but the contribution of other grass species increased by 6–9%. Synchronous recruitment following occasional drought-induced mortality can generate even-aged populations of the dominant desert dune grasses.     

Relative nutritional quality of C3 and C4 grasses for a graminivorous lepidopteran,Paratrytone melane (Hesperiidae)

Summary We tested the hypothesis that C₄ grasses are inferior to C₃ grasses as host plants for herbivorous insects by measuring the relative performance of larvae of a graminivorous lepidopteran, Paratrytone melane (Hesperiidae), fed C₃ and C₄ grasses. Relative growth rates and final weights were higher in larvae fed a C₃ grass in Experiment I. However, in two additional experiments, relative growth rates and final weights were not significantly different in larvae fed C₃ and C₄ grasses. We examined two factors which are believed to cause C₄ grasses to be of lower nutritional value than C₃ grasses: foliar nutrient levels and nutrient digestibility. In general, foliar nutrient levels were higher in C₃ grasses. In Experiment I, protein and soluble carbohydrates were digested from a C₃ and a C₄ grass with equivalent efficiencies. Therefore, differences in larval performance are best explained by higher nutrient levels in the C₃ grass in this experiment. In Experiment II, soluble carbohydrates were digested with similar efficiencies from C₃ and C₄ grasses but protein was digested with greater efficiency from the C₃ grasses. We conclude (1) that the bundle sheath anatomy of C₄ grasses is not a barrier to soluble carbohydrate digestion and does not have a nutritionally significant effect on protein digestion and (2) that P. melane may consume C₄ grasses at compensatory rates.     

Testing the grass-fire cycle: alien grass invasion in the tropical savannas of northern Australia

Abstract. Invasive alien grasses can increase fuel loads, leading to changes in fire regimes of invaded ecosystems by increasing the frequency, intensity and spatial extent of fires. Andropogon gayanus Kunth. (Gamba grass), a tall perennial grass from Africa, is invading ecosystems in the Top End of northern Australia. To determine whether A. gayanus alters savanna fire regimes, we compared fuel loads and fire intensities at invaded sites with those from native grass savannas. Savanna invaded by A. gayanus had fuel loads up to seven times higher than those dominated by native grasses. This higher fuel load supported a fire that was on average eight times more intense than those recorded in native grass savannas at the same time of year (means 15700 ± 6200 and 2100 ± 290 kW m⁻¹, respectively), and was the highest early dry season fire intensities ever recorded in the Northern Territory. These results suggest that A. gayanus is a serious threat to northern Australia's savannas, with the potential to alter vegetation structure and initiate a grass-fire cycle.     

A mowing experiment to evaluate the influence of management on the activity of host ants of <Emphasis Type="Italic">Maculinea</Emphasis> butterflies

Maculinea butterflies obligatory parasitize certain species of Myrmica ants. Thus, the presence of the host ant species is a limiting factor for the survival of a Maculinea population. Here, we analyse the influence of vegetation structure and ground temperature on ant diversity and abundance on Maculinea habitats, with the final aim of identifying the environmental variables determining patterns of variation in species composition in order to recommend a mowing regime that will promote our three target species: Maculinea teleius, M. nausithous and M. alcon. Experimental plots with different mowing regimes were established at eight sites in South-Eastern Germany, a region which still contains a number of relatively large, stable populations of these threatened butterfly species. Among the seven different ant species recorded, four belong to the genus Myrmica (M. scabrinodis, M. rubra, M. ruginodis and M. vandeli). Among these, M. scabrinodis results most abundant at all sites. In a CCA analysis of environmental variables recorded at the studied plots, ant species diversity appears largely determined by litter cover, mean temperature, and mean grass cover. Mowing once a year, in the second half of September, after the larvae have left their host plants, enhances the abundance of Myrmica ants in the meadows, and would be the best management compromise for all three species.     

Non-indigenous grasses impede woody succession

With the proliferation of old fields and the decline of native grasslands in North America, non-indigenous grasses, which tend to colonize and dominate North American old fields, have become progressively more abundant. These new grasses can differ from native grasses in a number of ways, including root and shoot morphology (e.g., density of root mat, height of shoots), growth phenology (e.g., cool season vs. warm season growth), and plant–soil–water relations due to differences in photosynthetic physiology (C₃ vs. C₄). Woody plants have been slow to colonize some old fields in the prairie-forest border area of North America and it is hypothesized that non-indigenous grasses may be contributing to the poor establishment success of woody plants in this region, possibly through more intense competition for resources. To test this hypothesis, a multi-factorial field experiment was conducted in which water, nitrogen, and grass functional group (non-indigenous C₃ and native C₄ species) were manipulated in a study of survival of oak seedlings. The grass type variously affected some of the different growth measurements, however, the effects of grass type on seedling growth were small compared to the effects on seedling survival. The results showed that when grown under dry conditions, seedlings growing in non-indigenous grasses experienced up to a 50% reduction in survival compared to those growing in native grasses under the same conditions. Analyses of root and shoot competition showed that the cause for the reduced survival in the non-indigenous grasses was due primarily to underground processes. The findings confirmed our initial hypothesis that non-indigenous grasses are likely contributing to the poor establishment success of woody plants in these old fields. However, the explanation for the reduced oak seedling survival in non-indigenous grasses does not appear to be due to reduced resource availability since soil water levels did not differ between non-indigenous and native grass plots and other resource levels measured (light, NO₃, and NH₄) were higher in non-indigenous grass plots under dry conditions. An alternative explanation is that the non-indigenous grasses modify the soil environment in ways that, under dry conditions, are deleterious to emerging oak seedlings. Since current climate projections for the upper Midwest are for hotter and drier summers, the results suggest that the resistance of these old fields to oak encroachment will likely increase in the future.     

Performance of a generalist grasshopper on a C<Subscript>3</Subscript> and a C<Subscript>4</Subscript> grass: compensation for the effects of elevated CO<Subscript>2</Subscript> on plant nutritional quality

The increasing CO₂ concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C₃ than C₄ plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C₃ plants. These hypotheses were tested by growing the grasses Lolium multiflorum C₃) and Bouteloua curtipendula C₄) at ambient (370 ppm) and elevated (740 ppm) CO₂ levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO₂ treatment combinations. As expected, the nutritional quality of the C₃ grass declined to a greater extent than did that of the C₄ grass at elevated CO₂; protein levels declined in the C₃ grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C₃ grass grown under elevated CO₂. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C₃ grass under elevated CO₂. Consumption rates of the C₃ and C₄ grasses were also similar, demonstrating a lack of compensatory feeding on the C₄ grass. We also examined the relative efficiencies of nutrient utilization from a C₃ and C₄ grass by M. sanguinipes to test the basis for the C₄ plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C₄ grass than from the C₃ grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C₃ grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C₃ grass and the better growth performance of M. sanguinipes on this grass at both CO₂ levels, we conclude that C₃ grasses are likely to remain better host plants than C₄ grasses in future CO₂ conditions.     

Defoliation effects on basal cover and productivity in perennial grasslands of Ethiopia

This study aimed to investigate how perennial grass species in Omo National Park (ONP), Ethiopia tolerated defoliation under varying amounts of rainfall. Perennial grasses that have evolved with grazing appear to be generally tolerant to defoliation, although how rainfall influences this tolerance is unclear. Research was conducted in three perennial grasslands where there is a rainfall gradient from north to south (800 – 500 mm yr⁻¹). Grasslands were characterized as either wet, intermediate or dry sites according to their relative position along the rainfall gradient. The wet, intermediate, and dry sites were dominated by two, five, and two grass species, respectively, which comprised 98% of total plant basal cover at each site. Six exclosures containing a total of 12 defoliated and 12 non-defoliated plots (2 × 2 m) were constructed at each site. Hand-clipped defoliation treatments were imposed bimonthly for 18 months (i.e., four rainy seasons, three dry seasons). Repeated measurements of basal cover and biomass production were analyzed for overall response and by species. Basal cover increased (P < 0.05) or remained unchanged for all but one perennial grass species. Biomass production indicated trend for some species but was sensitive to annual rainfall. Overall results indicated that dominant perennial grasses of ONP were tolerant to defoliation, and this tolerance was expressed under all three rainfall levels. In addition, a decrease (P < 0.05) in basal cover was found for grasses in non-defoliated plots for five of nine cases, indicating a negative response to protection from grazing and fire. This revised version was published online in June 2006 with corrections to the Cover Date.     

The role of wild grasses in the management of lepidopterous stem-borers on maize in the humid tropics of western Africa

Sites in the humid forest of Cameroon and the derived savanna of Benin were selected to evaluate the effect of planting border rows of wild host plants on lepidopterous stem-borer infestations and on maize yield. Grass species were chosen that in surveys and greenhouse trials were highly attractive to ovipositing female moths but with offspring mortality of close to 100%, thus acting as trap plants. In Cameroon, elephant grass Pennisetum purpureum Moench significantly lowered infestations of Busseola fusca (Fuller), Sesamia calamistis Hampson and Eldana saccharina Walker and increased yields of maize though the differences were not significant during all three cropping seasons. In 1998 in Benin, the only grass tested, Pennisetum polystachion L., significantly increased parasitism of mainly S. calamistis eggs by Telenomus spp. and larvae by Cotesia sesamiae Cameron and reduced numbers of the cob-borer Mussidia nigrivenella Ragonot. In 1999, three grass species; P. polystachion, Sorghum arundinaceum (Desv.) Stapf and Panicum maximum Jacq. were tested. Panicum maximum was the most efficient species for suppressing S. calamistis and M. nigrivenella infestations and enhancing egg and larval parasitism. In the Benin trials, with the exception of M. nigrivenella damage to cobs, the grass species tested had no beneficial effect on yield because pest densities were too low and also rodent damage to maize was enhanced with grasses in the vicinity of the crop. By contrast, stand losses due to Fusarium verticillioides Sacc. (Nirenberg), were significantly reduced by border rows of grasses.     

Microhabitat use by rodent species in a central Brazilian cerrado

We analysed microhabitat use by the rodents Calomys tener, Necromys lasiurus and Thalpomys lasiotis and the factors that may influence their abundances in “murundu” grasslands (open fields with termite mounds) at Aguas Emendadas Ecological Station, Planaltina, Federal District, Brazil. Two grids with 100 sampling points were established and traps were placed at each intersection of the grid, where five microhabitat variables were also measured. Rodents were trapped from June through October 2008. Microhabitat explained 21% of the variation in community structure, with grass density and the number of termite mounds explaining most of the variation. Necromys lasiurus was most often captured in areas with dense grasses, whereas T. lasiotis and C. tener were most often in areas less dense with grasses.     

Effect of certain herbicide treatments on pasture composition and inoculum of the take-all fungus

The improvement of pastures by the use of a range of herbicides to eliminate grasses, and their effect on populations of the take-all fungus (Gaeumannomyces graminis vartritici=Ggt) were studied in the field (at Esperance Downs, on the south-coast of Western Australia) from 1982 to 1985. Field trials were conducted to evaluate three herbicide treatments (2,4-D amine+propyzamide; 2,4-D amine+paraquat; paraquat/ diquat) and an unsprayed control. A pot trial involving these treatments with two levels of nitrogen was undertaken to confirm treatment effects observed in the field trial. All herbicide treatments resulted in reduced grass composition of pastures, in both the year of spraying and in the second year of pasture, but reduced dry matter production in the year of spraying. In the year of spraying, however, inoculum ofGgt was reduced (P<0.1) only following the 2,4-D amine+propyzamide treatment and was greater (P<0.1) after 2,4-D amine+paraquat treatment than the unsprayed treatment. Despite reduced grass levels in the herbicide-treated plots in the second year of pasture,Ggt inoculum did not differ between treatments, nor did it after a wheat crop which followed a second year pasture. There was high correlation (P<0.001) between disease levels and dry weights of grasses in the pot trial. There was significantly less (P<0.001) grass in pots treated with herbicides compared to the unsprayed control but no difference (P>0.05) was evident between treatments. Inoculum levels were lower (P<0.05) in the treated pots than the unsprayed control with no evidence of differences among treatments (P>0.05). Nitrogen level had no effect on disease (P>0.05). All herbicide treatments tested reduced grass level and total dry matter, both in the field and in pots. Whereas in the pot trial reduced grass levels resulted in reducedGgt inoculum, in the field such a reduction occurred only with the 2,4-D amine+propyzamide treatment and only in the year of spraying. Herbicide treatments had no effect onGgt inoculum in second year of pasture or crop. Unknown soil and environmental factors in the field precluded a simple relationship between grass level in pasture and subsequent level ofGgt inoculum, and where such a relationship did occur (2,4-D amine+propyzamide treatment) it appeared to be shortlived.     

Effects of an African grass invasion on Hawaiian shrubland nitrogen biogeochemistry

African perennial C₄ grasses are highly successful invaders in Hawaiian ecosystems. We examined the effects of African molasses grass (Melinis minutiflora Beauv.) on Hawaiian shrubland nitrogen (N) dynamics without the influence of fire disturbance. Vegetation tissue carbon and nitrogen chemistry, soil inorganic N pools, net N mineralization rates, and total soil N were studied in three adjacent areas: a monospecificMelinis grassland, a mixed grass/shrubland mosaic, and an un-invaded shrubland.Melinis plots within the mosaic area exhibited the largest inorganic N pools and fastest net N mineralization rates, but were temporally variable with grass phenology. Un-invaded shrubland plots contained the smallest inorganic N pools and lowest net N mineralization rates. Grass foliar C:N and litter C:N were lower than those of common shrubland species, providing one possible link between species and ecosystem N dynamics at this site. The combined effects of N cycle modification, successful light competition, and fire-cycle enhancement make the invasion ofMelinis a significant perturbation to Hawaiian shrubland ecosystem function and successional dynamics. ei]Section editor H Lambers     

The invasive grass,Melinis minutiflora,inhibits tree regeneration in a Neotropical savanna

Abstract Exotic grasses are becoming increasingly abundant in Neotropical savannas, with Melinis minutiflora Beauv. being particularly invasive. To better understand the consequences for the native flora, we performed a field study to test the effect of this species on the establishment, survival and growth of seedlings of seven tree species native to the savannas and forests of the Cerrado region of Brazil. Seeds of the tree species were sown in 40 study plots, of which 20 were sites dominated by M. minutiflora, and 20 were dominated by native grasses. The exotic grass had no discernable effect on initial seedling emergence, as defined by the number of seedlings present at the end of the first growing season. Subsequent seedling survival in plots dominated by M. minutiflora was less than half that of plots dominated by native species. Consequently, at the end of the third growing season, invaded plots had only 44% as many seedlings as plots with native grasses. Above‐ground grass biomass of invaded plots was more than twice that of uninvaded plots, while seedling survival was negatively correlated with grass biomass, suggesting that competition for light may explain the low seedling survival where M. minutiflora is dominant. Soils of invaded plots had higher mean Ca, Mg and Zn, but these variables did not account for the higher grass biomass or the lower seedling survival in invaded plots. The results indicate that this exotic grass is having substantial effects on the dynamics of the tree community, with likely consequences for ecosystem structure and function.     

Effects of Frequent Mowing on Survival and Persistence of Forbs Seeded into a Species-Poor Grassland

Many early attempts at tallgrass prairie reconstruction failed to achieve the high species diversity of remnant prairies, and instead consist primarily of C₄ grasses. We hypothesized that frequent mowing of established prairie grasses could create sufficient gaps in the aboveground and belowground environment to allow for the establishment of native forbs from seed. We studied forb seedling establishment in a 25‐year‐old prairie planting in northern Iowa that was dominated by native warm‐season grasses. In winter 1999, 23 species of native forbs were broadcast into the recently burned sod at a rate of 350 viable seeds/m². Treatment plots were mowed weekly for either one or two growing seasons, and control plots were unmowed. Mowed plots had greater light availability than controls, especially when warm‐season grasses began to flower. Overwinter seedling mortality was 3% in mowed treatments compared to 29% in the controls. Forbs in mowed plots had significantly greater root and shoot mass than those in control plots in the first and second growing seasons but were not significantly more abundant. By the fourth growing season, however, forbs were twice as abundant in the mowed treatments. No lasting negative impacts of frequent mowing on the grass population were observed. Mowing a second year influenced species composition but did not change total seedling establishment. Experimental evidence is consistent with the idea that mowing reduced competition for light from large established grasses, allowing forb seedlings the opportunity to reach sufficient size to establish, survive, and flower in the second and subsequent years.     

Effect of soil moisture and clipping stresses on the nutrient (N,P and K) concentration,uptake and use efficiency in one temperate and two tropical grasses

Summary The concentration, uptake and element use efficiency of N, P and K in one C₃ annual (Polypogon monspeliensis) and two C₄ (Echinochloa colonum, an annual, andDichathium annulatum, a perennial) grasses were determined during winter and summer seasons in monocultures raised in field plots at three moisture levels,viz. full, half and one-fourth of field capacity. At each moisture regime the plants were clipped thrice at moderate and severe levels corresponding to 40 and 80% of live green. The concentration of these elements was characteristic of the growth habit of these plants;e.g. the build up of concentration was maximum in leaf of the annuals while it was comparable in crown and leaf of Dichanthium. The N level was maximum in Polypogon. The nutrient use effiency was comparable in the two annuals and maximum K and N use were obtained in Polypogon and Dichanthium, respectively.     

Fungal endosymbionts affect aphid population size by reduction of adult life span and fecundity

The symbiosis between grasses and endophytic fungi is a common phenomenon and can affect herbivore performance through acquired, chemical plant defence by fungal alkaloids. In laboratory experiments, two species of common grass aphids, Rhopalosiphum padi and Metopolophium dirhodum were tested, in a population experiment (on four plant cultivars) and individually (on one plant cultivar) for the effects of the endophyte, Neotyphodium lolii, that forms symbiotic associations with perennial ryegrass Lolium perenne. In the population experiment that lasted for four aphid generations both aphid species showed decreased population sizes when feeding on each of the four endophyte-infected cultivars. Individuals of R. padi tested individually showed reduced adult life span and fecundity when feeding on infected plants. Individuals of M. dirhodum showed no response in any of the traits measured. This suggests that R. padi individuals are more sensitive to endophyte infection than M. dirhodum individuals. However, all infected grass cultivars reduced population sizes of both aphid species over four generations. Therefore, fungal endophytes can reduce populations of aphid herbivores independent of plant cultivars.     

Immunity against Boophilus annulatus induced by the Bm86 (Tick-GARD) vaccine

Friesian cattle were immunized with two inoculations of anti-tick Bm86 (Tick-GARD) vaccine and were challenged 30 or 90 d later with Boophilus annulatus larvae derived from 1.2 g of eggs. No nymphs or adult ticks were found on the immunized cattle during four weeks after challenge. Repeated infestations (2 to 4) with larvae on three other calves during a period of 160 and 390 d after the immunization did not result in development of nymphal and adult stages. In control, non-immunized cattle infested with corresponding batches of larvae 1380 to 4653 replete adult female ticks were collected. Larvae issued from Babesia bovis-infected female ticks transmitted the infection to Bm86-immunized cattle, but the progeny of B. bigemina-infected females did not. Since B. bigemina is transmitted exclusively by nymphal stages of Bo. annulatus these results support the observation that immunity induced by Bm86 affects the larval stage of this tick.     

Field responses to added organic matter, arbuscular mycorrhizal fungi, and fertilizer in reclamation of taconite iron ore tailing

A three season study was conducted to determine the effect of added composted yard waste, arbuscular mycorrhizal (AM) fungi, and fertilizer on plant cover, standing crop biomass, species composition, AM fungal infectivity and spore density in coarse taconite iron ore tailing plots seeded with a mixture of native prairie grasses. Plant cover and biomass, percent seeded species, mycorrhizal infectivity and spore density were greatly increased by additions of composted yard waste. After three seasons, total plant cover was also greater in plots with added fertilizer. Third season plant cover was also greater in plots amended with the higher rate (44.8 Mg ha^{–1) of compost than the moderate rate (22.4 Mg ha-1}). Field inoculation with AM fungi also increased plant cover during the second season and infectivity during the first two seasons. Seeded native species, consisting mostly of the cover species Elymus canadensis, dominated plot vegetation during the second and third seasons. Dispersal of AM fungal propagules into nonmycorrhizal plots occurred rapidly and increased infectivity in compost-amended plots during the third season. In plots with less than 10% plant cover, AM fungal infectivity of inoculated plots was greatly reduced after the second season. The high level of plant cover and the trend of increasing proportion of mycorrhizal-dependent warm-season grasses, along with increases in infectivity, forecast the establishment of a sustainable native grass community that will meet reclamation goals.