THE FRIT FLY AND ALLIED STEM-BORING DIPTERA IN WINTER WHEAT AND HOST GRASSES

Sampling for stem-boring larvae was undertaken in 1954-56 on ley plots of Lolium perenne, Dactylis glomerata, Festuca arundinacea, F. rubra, Agrostis tenuis and Poa pratensis in randomized experiments at Hurley, Berks. The samples showed infestations by dipterous larvae, mainly species of Oscinella, Meromyza and Opomyza. The larvae showed preferences for specific grass hosts. More larvae were found where plots had been grazed throughout the season than where an early hay cut had preceded grazing. The total numbers of larvae varied between o and 688 per sq.yd. in November.
The larval populations of the leys were reflected in the populations in winter wheat which followed the plough-up of the leys. Populations of up to sixty-five larvae per sq.yd., mostly species of Oscinella , were found in the wheat in March. In 1956 a heavy larval infestation was associated with the death of considerable numbers of wheat plants.     

Earthworm communities in conventional wheat monocropping and low-input wheat-clover intercropping systems

A comparative study was conducted on earthworm communities in a conventional winter wheat monocropping system and a low‐input intercropping system in which successive crops of winter wheat were direct‐drilled into a permanent white clover sward. Earthworm abundance, biomass and species composition under the two cropping systems in the second and third years of successive cropping were assessed each spring and autumn in farm‐scale field plots at four sites using formalin and electrical extraction methods. The wheat‐clover cropping system supported larger earthworm communities (overall mean abundance 548 individuals m^?2, 137 g biomass m^?2) than conventional wheat monocropping (194 individuals m‐2, 36 g biomass m‐2). Between one and five more earthworm species were recorded in the wheat‐clover system than in the wheat system at three out of the four study sites. Wheat–clover cropping especially favoured species belonging to the epigeic and epigeic/anecic ecological groups such as Lumbricus castaneus, L. festivus, L. rubellus, juvenile Lumbricus and Satchellius mammalis. Earthworm communities in the wheat‐clover cropping system were comparable in size and species composition to communities normally found in perennial grassland‐type habitats such as pastures and grass‐legume leys.     

Occurrence of Phialophora radicicola var. graminicola and Gaeumannomyces graminis var. tritici on roots of wheat in field crops

Assessments of Phialophora radicicola var. graminicola (PRG) and Gaeumannomyces graminis var. tritici (GGT) were made by culturing and by direct microscopic examination of pieces of seminal roots from 16 winter wheat crops grown in different cropping sequences and with different phosphate manuring. PRG occurred on all wheat crops, but was abundant only on wheat after grass, where it seemed to delay the onset of damaging take-all by 1 yr. Delayed occurrence of take-all by phosphate fertiliser was not related to differences in populations of PRG. Wheat grown in ‘take-all decline’ soils had only small amounts of PRG, indicating that the development and the decline of take-all epidemics may be influenced by different biological control mechanisms; breaking sequences of wheat crops by 1 yr grass leys might harness the advantages of both mechanisms.     

Unexpected larval habit of Listronotus bonariensis (Coleoptera: Curculionidae) raises questions about population dynamics analysis and management

Listronotus bonariensis (Kuschel) is a pest of agriculturally important graminaceous species, with mining larvae that kill the stems of the host plants. In this study, larval populations were measured in spring and summer in irrigated dairy grassland comprising Lolium perenne L. (cv. Nui) with and without the endophyte Epichloë festucae var. lolii Latch, M.J. Chr. and Samuels and Poa annua L.. Larvae were extracted from tillers taken from the swards of these two grass species and extracted from turves, and L. bonariensis population densities were estimated from tiller and turf larval counts on a m⁻² basis. Over the study period, the total number of larvae and larval densities extracted from turves was on average 2× greater than indicated from tillers. In most seasons, larval densities from turves were significantly higher than those from the tillers, though there was no correlation between tiller and turf larval densities. Mean head capsule widths of larvae emerging from turf samples showed significant seasonal effects compared with tillers, while mean head capsule widths of all four instars were significantly greater when extracted from tillers compared with turves. There was a significant endophyte effect on head capsule widths of larvae collected in summer, but the effect was not consistent across instars or source. Conversely, no significant endophyte effect on head capsule width was found in spring populations from either tillers or turves. This study shows that in irrigated dairy pasture, a high proportion of L. bonariensis larvae can live externally of tillers, presumably among the organic matter around the base of grasses in irrigated dairy pasture, and that density estimates based only on tiller populations will have significantly underestimated actual numbers. Having a precise indication of larval population densities is essential when developing life tables or determining economic damage threshold levels.     

Distribution and abundance of adult Opomyza florum (Diptera: Opomyzidae) in cereal crops and grassland

From 1971 to 1979 counts were made of the numbers of Opomyza florum adults found in vacuum net samples taken from cereal and grass fields on a 62-km² study area in West Sussex. In 2 years, 1974 and 1975, counts were made of the numbers of adults found in similar samples taken from hedgerow grasses. In all years, numbers of adults were highest in winter wheat crops; relatively few were found in other autumn- or spring-sown cereals or in grass fields. Mean numbers (/m²) in winter wheat in June varied from 33.0 in 1974 to only 0.9 in 1977. In most years, the first adults were found in June in winter wheat; numbers reached a peak in July and then declined rapidly. More adults were usually found in winter wheat crops that followed winter wheat in the rotation than in those following grass. Adults were also more abundant in June in winter wheat crops sown relatively early than in those sown late. The current tendencies towards earlier drilling of winter wheat and to the growth of successive wheat crops could increase the pest status of O. florum.     

Vegetative structure,microclimate, and leaf growth of a páramo tussock grass species,in undisturbed,burned and grazed conditions

In neotropical alpine grasslands (páramo), the natural tussock grass vegetation is extensively grazed and occasionally burned. The low productivity of the tussock grass seems to be the reason for the disappearance of this growth form in the most frequently intervened areas. The structure, microclimate and leaf elongation rates of new emerging leaves were studied for the dominant tussock grass species Calamagrostis effusa, at an undisturbed, a moderately grazed (7 year after fire) and a heavily grazed (3.5 years after fire) site. In absence of grazing and burning, the tussocks had a high standing crop (1.07±0.09 kg DW · m^-2) and leaf area per projected tussock cover (LAI: 9.6±1.4). Two thirds of the total mass was dead and more than half of the leaves were in horizontal position. The tussock growth form protects the meristems from severe climatic conditions. At midday, the temperature was higher at meristem level than in the rest of the tussock. At this level, photosynthetic irradiance (PI) was almost extinct at 2.9±0.74% of PI above the vegetation. The red/far red ratio (R/FR) was strongly decreased. Initial leaf elongation of new born leaves was 2.3 mm · day^-1, and constant during the year; estimated net annual production was 198±73.8 g m^-2. At the moderately grazed and the heavily grazed study sites, the tussocks were smaller, greener and more erect than those at the undisturbed site. More PI reached the meristems and R/FR was higher at the base of grazed tussocks. Leaf elongation rates were lower. Most of the litter disappeared during the fires. The lower elongation rate of leaves in the grazed areas might be a response to defoliation, resulting in increased tillering and a lack growth associated with poor temperature insulation and more UV-B damage.     

Establishing Tallgrass Prairie on Grazed Permanent Pasture in the Upper Midwest

The goal of the study was to learn whether native prairie grasses and, eventually, a diverse mixture of native forbs could be incorporated in permanent pastures by means of rotational grazing by cattle. An experiment was established on a farm in northeastern Iowa on a pasture that had never been plowed but had been grazed since the 1880s. One treatment was protected from grazing to test for the presence of remnant vegetation. Andropogon gerardii, Sorghastrum nutans, Panicum virgatum, and Desmanthus illinoensis were introduced in plots first treated with glyphosate; seeds were either drilled (DR) or hand-broadcast and incorporated by controlled cattle trampling (BT). Seedling establishment and aboveground biomass were followed over 3 years. There was no evidence for remnant native plants on uplands, but seven species of native forbs and four native graminoids flowered in exclosures erected within waterways. D. illinoensis initially established up to 12 seedlings/m² but had disappeared from all but one plot by the third year. Variation in native grass establishment among replicate plots within treatments was very high, ranging initially from 0.2 to 9.9 plants/m². In August of the second year, native grasses made up only 8% of the available forage in DR plots and 1% of BT plots. One year later, however, native grasses made up 56% of the available forage in DR plots and 37% of BT plots, and these differences were significant (p = 0.05). A pilot study seeded in late winter (frost seeding) suggested that seeds spread after cattle trampling produced five times more seedlings (2.5/m²) than seeds spread before cattle trampling (0.5/m²). Frost seeding had advantages because it did not require herbicide for sod suppression or tractor access to the site. New plantings could be safely grazed in early spring and late fall, before and after most native grass growth, to offset the negative economic impact of protecting new plantings from burning during the growing season. But this practice precluded subsequent prescribed burning. I propose a strategy for incorporating native wildflowers into the pasture over time with minimum cost.     

Use of ryegrass strips to enhance biological control of aphids by ladybirds in wheat fields

Abstract Non‐crop habitats may play a vital role in conservation biological control. This study tested the effect of ryegrass (Lolium multiflorum L.) strips on aphid and ladybird populations in adjacent winter wheat fields. The field experiment was conducted in three ryegrass‐margin wheat plots and three control plots in 2010 in North China. In spring, the same aphid species, Sitobion miscanthi (Takahashi), was found in both the ryegrass strips and wheat plots. The population density of ladybirds in the ryegrass strips (3.5 ± 0.9/m²) was significantly higher than in the wheat plots (1.5 ± 0.5/m²). We cut the ryegrass, forcing the ladybirds to migrate to the wheat fields. Three and eight days after cutting the ryegrass, the aphid numbers in the ryegrass‐margin wheat plots decreased significantly: they were 19.9% and 53.6%, respectively, lower than in control plots. In the early period of ladybird population development, the percentage of larvae was greater in the ryegrass‐margin wheat plots than in controls, and the peak number of pupae in the ryegrass‐margin wheat plots occurred 5 days earlier than in the control plots. The results suggest that ryegrass strips may promote the development of ladybird populations. Cutting ryegrass can manipulate ladybirds to enhance biological aphid control in wheat fields. The efficiency of this management approach is discussed.     

The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth and yield of winter cereals

In 1986/1987 and 1987/1988 wild rabbits (Oryctolagus cuniculus) were trapped and enclosed in a 0.3 ha site in which two varieties of winter barley (Igri and Panda) and two of winter wheat (Norman and Mission) were grown in a split plot block design experiment. The level of rabbit population was varied to emulate natural variation in numbers throughout the growing season and was regulated to produce a peak density of 77 rabbits ha^-* in the first year, and 33 rabbits ha^-1! in the second year. Grazing was managed by the use of exclosure fences around plots to produce four treatment levels - protected, autumn grazed, spring grazed and totally grazed regimes. Rabbit damage was assessed using stem and leaf damage indices several times through the growth of the crops. Yields were measured in terms of head number, grain weight and total yield. There was no evidence of varietal preference among the four cereal varieties on the basis of damage assessments. In the first year the totally grazed treatment led to an increase in the number of unripe heads present at harvest which would indicate a delayed harvest date in a field crop. Winter wheat showed a trend towards higher yield loss in spring-damaged plots, possibly linked to the time of tillering in this crop. Yield losses overall were highest in those plots grazed in either the autumn or throughout the entire season. The level of peak rabbit population did not appear to influence the degree of loss in either year. The results indicate that there may be a threshold of rabbit damage early in the growth of the crop which contributes most to the yield loss. This emphasises the importance of protecting a winter cereal crop at its establishment phase.     

Habitat and substrate influences on population and production dynamics of a stream caddisfly, Ceraclea ancylus (Leptoceridae)

SUMMARY. Population and production dynamics of Ceraclea ancylus (Vorhies), a leptocerid caddisfly with a univoltine life cycle, five larval instars, and a single cohort population, were examined in Brashears Creek, Kentucky. A systematic sampling approach that included analysis in riffle, pool, and waterwillow bed habitats was used and fourteen sampling transects were taken across Brashears Creek between May 1971 and July 1972. For each of the 70 m² samples taken along a transect, the depth, habitat, and substrate type were recorded. The number of C. ancylus cases and numbers and dry weights of each larval instar were determined. The majority of the C. ancylus population was in the second larval instar in July, the third larval instar in August, the fourth larval instar in September, and the fifth larval instar from October through May. The spring population was 30% of the early instar maximum estimated the previous August. The spatial distribution of C. ancylus reflects a logarithmic pattern with early instar larvae more highly clumped than the late larval instar and pupal populations. Initial standing stock estimates were less than 1% of the standing stock biomass. A production estimate of 9.9 mg/m²·year (dry weight) was determined using the instantaneous growth method, Allen's Curve method, and the Hynes method of estimating secondary production. Turnover ratios (7.0 annual TR, 5.7 cohort TR) were higher than estimates reported as typical for benthic macroinvertebrates because of the low initial to final mean individual weight of the C. ancylus larvae (0.4%). Production estimates calculated for C. ancylus populations in waterwillow bed (4.4 mg/m²·year) and pool (13.7 mg/m²·year) habitats were less than calculated for the riffle population (19.9 mg/m²·year). The annual turnover ratio (10.2) was higher in the pool population than in other habitats because of spring larval migration into the pool from other habitats. A trend of higher production estimates with larger sized substrate particles and increased numbers of particles may reflect the increase in available food sources or attachment sites. The accuracy of production estimates and their applicability to water resource management may be limited by a failure to consider the spatial distributions of the population being sampled and the tendency for sampling procedures to be confined to single habitats.     

Infestation of the white grub Dasylepida ishigakiensis (Coleoptera: Scarabaeidae) in hayfields on Miyako and Ishigaki Islands, Japan

To examine the local distribution of Dasylepida ishigakiensis Niijima et Kinoshita larvae (Coleoptera: Scarabaeidae) on Miyako Island and Ishigaki Island, a survey was conducted in hayfields on the two Islands in February and March 2011. Symptoms of white grub infestation, such as patches of wilted grass and thin, yellow grass stands, were observed in some of the 20 hayfields surveyed on Miyako Island. Three species of white grub were observed there: D. ishigakiensis, Anomala cpustulata cpustulata Matsumura in Hirayama, and Anomala albopilosa (Hope), in the ratio 92:7:1, respectively. The mean population density of D. ishigakiensis in the hayfields was 54.3 m^?2 and the maximum was 225 m^?2. No significant relationship was found between the damage levels of hay grass and the D. ishigakiensis larval densities. In contrast, no damage was observed in the 14 hayfields surveyed on Ishigaki Island, although some D. ishigakiensis larvae were found at a low density in 4 hayfields. In 2006, no D. ishigakiensis larvae were found in sugarcane fields on this island in a separately conducted intensive survey. These observations may suggest that D. ishigakiensis larvae are present in hayfields at a low density but that few individuals occur in sugarcane fields on Ishigaki Island.     

Nest and soil populations of Trinervitermes spp. with particular reference to T. geminatus (Wasmann), (Isoptera), in Southern Guinea savanna near Mokwa,Nigeria

Summary Nest and soil populations of Trinervitermes spp. were estimated on grazed secondary savanna woodland near Mokwa cattle ranch and on primary savanna woodland, 6 km from the ranch. Nest populations were estimated by obtaining a relationship between size of nest and the number of termites in the nest and using the relationship to estimate populations in measured nests within the study area.Mound populations of T. geminatus, by far the most abundant species, were 222 m^-2 at a mound density of 232 ha^-1 at the ranch, and 225 m^-2 at a mound density of 175 ha^-1 on primary savanna woodland. The mound population at the ranch represented a fresh weight biomass of 1.089 g m^-2. Changes in abundance of the mound population of T. geminatus were correlated with breeding and foraging cycles. Maximum numbers (388 m^-2, 2.03 g m^-2) in August/September were reduced by the flight of alates and loss of foragers to predators; thereafter, the population continued to decrease (126 m^-2, 0.57 g m^-2) until the cessation of foraging in April/May and numbers of larvae and nymphs began to increase. Soil and mound sampling in primary and secondary savanna showed that although T. geminatus is a mound inhabiting species, two thirds of the mound plus soil population was outside the mounds giving a total population of 737 m^-2 (3.08 g m^-2). Alate production was estimated at 15.5 m^-2 (0.19 g m^-2) and neuter production at 367 m^-2 (1.66 g m^-2); production/biomass ratio was 1.0 T. togoensis (total population of 21 m^-2) and T. occidentalis (200 m^-2) had 90–96% of the total numbers outside the mounds, indicating that these two species were primarily subterranean.     

Effect of prey concentration on growth of piscivorous Japanese Spanish mackerel Scomberomorus niphonius larvae in the Seto Inland Sea, Japan

Japanese Spanish mackerel, Scomberomorus niphonius, larvae feed almost exclusively on fish larvae from the first‐feeding stage. The relationship between the growth of S. niphonius larvae and concentration of major prey organisms of the larvae, clupeid larvae, was investigated in the Sea of Hiuchi, the central Seto Inland Sea, Japan, from 28 to 29 May 1997. Water temperature, salinity, and the concentration of clupeid larvae had no significant effect on the S. niphonius larval concentration. Mean growth rate of S. niphonius larvae varied between 0.38 and 0.64 mm day^?1. The temperature and salinity had no significant effect on the mean larval growth rate while there existed prey concentration‐dependent growth at lower prey concentration. The relationship between the mean larval growth rate (G_m) and concentration of clupeid larvae (C_C) was expressed by a logarithmic equation: G_m = 0.037 log C_C + 0.441 (n = 16, r² = 0.519, P < 0.01).     

Life history and secondary production of Glossosoma nigrior Banks (Trichoptera: Glossosomatidae) in two Alabama streams with different geology

We studied life history and secondary production of a caddisfly scraper, Glossosoma nigrior, in two Alabama streams. Collier Creek, located within the Appalachian Plateau physiographic province, is underlain by sandstone bedrock, while Hendrick Mill Branch is located in the Valley and Ridge physiographic province with limestone bedrock. G. nigrior populations in both streams exhibited trivoltine life histories, which were attributed to the higher water temperature regimes than those found in more northern streams. Mean larval density (556 m⁻²) and biomass (B) (49.2 mg AFDM m⁻²) were much higher in Hendrick Mill Branch than Collier Creek (78 m⁻² and 6.7 mg AFDM m⁻²). G. nigrior in Hendrick Mill Branch maintained continuous larval growth and higher larval density than Collier Creek throughout the year mainly due to a greater availability of optimal habitat, a more stable hydrology, and warmer winter water temperature. These factors also resulted in the much higher annual secondary production (P) in Hendrick Mill Branch (965 mg AFDM m⁻²; P/B = 18.3) than Collier Creek (115 mg AFDM m⁻²; P/B = 17.9). Gut content analysis revealed that algae (>50%) and detritus (>40%) were the major diet items for G. nigrior, and the majority of secondary production (>80%) was contributed by the consumption of algae. Glossosoma populations play an important role in trophic linkage in these streams with their high production and grazing activities. Handling editor: D. Dudgeon     

Season of grazing and stocking rate interactively affect fuel loads in Baikiaea plurijuga Harms woodland in northwestern Zimbabwe

Wildfire is a major disturbance in Baikiaea plurijuga Harms woodland savannas. We tested the hypothesis that the timing and intensity of herbivory influence fuel loads. We used three stocking rates namely light (three cows and four goats ha^?1), medium (six cows and eight goats ha^?1) and heavy (eleven cows and sixteen goats ha^?1) and three times of grazing namely early‐, middle‐ and late‐growing seasons. Season of grazing and stocking rate influenced herbaceous phytomass. Phytomass was generally the highest (53.5 g DM m^?2) in paddocks grazed during the early growing season and the lowest (27.8 g DM m^?2) in those grazed during the late growing season. Phytomass was also generally the highest (40.4 g DM m^?2) in lightly stocked paddocks and the lowest (32.7 g DM m^?2) in heavily stocked ones. Litter mass was the lowest (160.8 g DM m^?2) in paddocks grazed during the early season whereas there were no differences in ungrazed paddocks and those grazed during either mid‐ or late growing seasons (205.4 g DM m^?2). There was a negative relationship between litter mass and stocking rate. Baikiaea Benth. woodlands should be grazed during either the mid‐ or late‐growing season at stocking rates greater than 0.1 LU ha^?1 to reduce grass fuel loads.     

D-vac sampling for predatory arthropods in winter wheat

We evaluated the D-vac suction machine for sampling predatory arthropods in Oklahoma winter wheat fields. The efficiency of D-vac sampling was low for adult Coccinellidae and Carabidae. Sampling efficiency was greater for coccinellid larvae. Sampling efficiency was high for adult and immature Nabidae and Chrysopidae, for Araneae, and for adult Staphylinidae. For most predators, there were significant correlations between the number of individuals in D-vac samples and the number of individuals per m² in the field. The highest correlation was 0.82 for adult Staphylinidae. Correlations for most predators were <0.60. Significant partial correlations between D-vac sample estimates and ancillary abiotic and biotic variables occurred for most predators, indicating that D-vac sampling efficiency was affected environmental variables. Multiple regression models were constructed to relate population estimates from D-vac sampling to absolute density by adjusting estimates for influential abiotic and biotic environmental variables. Significant regression models were not achieved for adult Coccinellidae or adult Carabidae, and the coefficient of determination was low (0.18) for the model for adult Nabidae. Higher values of R² were achieved for larval Coccinellidae, Chrysopidae adults and larvae, Nabidae nymphs, Araneae, and adult Staphylinidae. Among abiotic variables, air temperature and wind velocity most frequently entered into step-wise regression models. Among biotic variables, wheat plant growth stage and wheat tiller density frequently entered into models.     

Residence time and drift patterns of larval June sucker Chasmistes liorus in the lower Provo River as determined by otolith microstructure

Estimates of age derived from daily ring counts from otoliths and capture rates of larval June sucker Chasmistes liorus were used to determine the relationship between discharge rates of the Provo River and residence time and patterns of larval drift. During 1997, larval drift occurred over a 22 day period when discharge rates were low (mean ±s.d. 3·2 ± 0·0 m³ s^?1). In 1998, larval drift occurred in two separate events over a 40 day period. Discharge was higher during the first larval drift period (19 days; 24·8 ± 1·3 m³ s^?1) and lower during the second larval drift period (17 days; 7·0 ± 0·9 m³ s^?1). In 1997, no larval fish were collected at the lowermost transect on the Provo River (nearest Utah Lake), and few larvae >21 days of age were found. During the first drift period of 1998, larval C. liorus were collected at all transects, and mean age of larvae collected between upstream and downstream transects increased by c. 7 days. During the second drift period of 1998, only a few were collected in the lowermost transects, and age did not increase with proximity to the lake. Patterns in catch and age distribution of larval C. liorus in the lower Provo River suggest that recruitment failure occurs during the larval drift period in years with insufficient discharge to transport larvae into the lake.     

Life cycle and growth ofTrichostegia minor (Curtis) in temporary woodland pools (Trichoptera: Phryganeidae)

Larvae of the caddisTrichostegia minor (Curtis) were collected from four woodland pools in The Netherlands, three of which are temporary, from August 1986 till June 1987. Eggs and larvae of this species proved to be very well adapted to drought, freezing, strongly fluctuating pH and alkalinity levels and prolonged oxygen deficit. The life cycle ofT.minor in a small woodland marsh overgrown byCalla palustris took one year. Adult flight period started at the end of May. Oviposition took place independent of water. Hatching of the eggs started in September and was probably induced by immersion. During the larval stage from September until May, 5 instars could be distinguished by the size of the head capsule. Growth of instars I, II and III during autumn was moderate. Most larvae overwintered as instar III or IV. Possibly there was a larval diapause during winter. In spring rapid growth to instar V took place prior to pupation. Growth rate, expressed as the increase of mean individual dry weight was highest from March to April (2.05±0.75% DW.m^–2.d^–1). In extremely shallow water growth in spring was initially more rapid compared to growth in deeper water. During winter the growth rate decreased to 0.038±0.071% DW.m^–2.d^–1. Net annual production based on the changes of momentary biomass was 183.2±31.7 mg DW.m^–2.y^–1 or 177.2±31.3 mg AFDW.m^–2.y^–1. Production loss during the winter season was 75.1±10.8 mg DW.m^–2.y^–1 or 72.3±10.6 mg AFDW.m^–2.y^–1.     

Host plant choice and location by larvae of the wheat bulb fly (Delia coarctata)

Wheat bulb fly (Delia coarctata Fallen, Diptera: Anthomyiidae) is an important pest of winter wheat in the eastern half of the UK, and in northern and eastern Europe. The larvae must find a host plant and invade a tiller soon after hatching in late January. Chemical controls are costly and weather conditions may reduce their efficacy or prevent their application. Post‐emergence control relies on organophosphate insecticides, which may soon be withdrawn due to concerns about their negative health and environmental effects. Winter wheat (Triticum aestivum L.) is the preferred cereal host, but other winter cereals and related grasses may also be attacked, while oats (Avena spp.) are shunned. In choice test bioassays, neonate larvae chose couch grass (Elytrigia repens (L.) Nevski syn. Elymus repens (L.) Gould, Agropyearon repens (L.) Beauv.) seedlings and exudates over wheat seedlings and exudates, and exhibited geotaxis and negative phototaxis. Analysis of larval trails in choice test bioassays of seedling exudates showed that couch exudates are more attractive than wheat exudates, and that wheat exudates are more arrestant than couch exudates. This suggests that infochemicals isolated from couch, wheat, and oats could be used in wheat bulb fly control; possible delivery mechanisms are discussed. These findings, previous research, and a comparison of the phenologies and geographical distributions of D. coarctata and its hosts suggest that E. repens is the natural host of D. coarctata.     

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year⁻¹ to ponds (up to 5.5 g AFDM m⁻² year⁻¹). Larval production ranged from 0.4 to 7.4 g AFDM m⁻² year⁻¹ among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m⁻² year⁻¹ produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m⁻² and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year⁻¹ (range=21.0–135.2 g AFDM year⁻¹) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year⁻¹ into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r ² =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.