Kann die Überwachung der Eiablage des Apfelwicklers Carpocapsa (Cydia) pomonella L. die Flugkontrolle ersetzen?

Ohne Zusammenfassung     

An assessment of potential of hybrid poplar for planting in the Virginia Piedmont

Poplar species grow well across the temperate zone, but hybrid varieties have not previously been evaluated for planting in the Virginia Piedmont region. The top 12 clones in height growth and rust resistance from a screening trial involving 98 hybrid poplar varieties of three taxa (Populus deltoides × P. maximowiczii, DxM; P. deltoides × P. nigra, DxN; P. deltoides × P. trichocarpa, DxT) were selected for planting in replicated yield trials at two locations in the Virginia Piedmont. Results through the first four growing seasons showed that the DxM taxon had the most rapid height development. It was, however, the taxon most affected by a late spring frost at the Appomattox-Buckingham State Forest site and by Septoria stem canker at the Reynolds Homestead site. Analysis of variance of clonal and location effects showed highly significant differences among replicates within location and among clones within taxon. Among seven clones within the DxM taxon, pairwise comparison tests of height growth identified two groups: a group of four better clones that were significantly different (p = 0.05) from a second group of three. These early results suggest that multi-selection criteria, including growth, disease and frost resistance, are important when developing hybrid poplar clones for planting in the Piedmont region.     

Low light intensity and flower bud abortion in Asiatic hybrid lilies. I. Genetic variation among cultivars and progenies of a diallel cross

Summary When Asiatic lilies are forced during the winter period, additional light is needed to prevent flower bud abscission and flower bud blasting. Growth room experiments showed considerable differences among eight lily cultivars in their response to low light. Among these cultivars, Connecticut King and Enchantment appeared to be the most sensitive to low light conditions while Uncle Sam and Scout were the least sensitive.Analysis of an incomplete diallel cross between nine cultivars showed significant differences in general combining ability (GCA) for flower bud abortion, number of buds, forcing time, plant height and leaf scorch under winter greenhouse conditions. Enchantment had the highest positive GCA for bud abortion, indicating a high sensitivity to low light conditions. Uncle Sam had the lowest GCA. Pirate and Scout appeared to have a high GCA for sensitivity to leaf scorch. Connecticut King was found to be a probable source of cytoplasmic male sterility. The data suggest that male sterility is associated with better response to low light conditions.     

Residual effects of the Xa-4 resistance gene in three rice cultivars when exposed to a virulent isolate of Xanthomonas campestris pv. oryzae

Summary F₂ plants of five, and F₃ plants of three, crosses between genotypes carrying the race-specific resistance gene Xa-4 and genotypes not carrying this gene were inoculated with two isolates of Xanthomonas campestris pv. oryzae. Half the tillers of each plant received isolate PX061, avirulent on the Xa-4 gene, the other half of the tillers received isolate PX099, virulent for the Xa-4 gene. The F₂ and F₃ populations segregated for a single dominant resistance gene, Xa-4.The parental, F₂ and F₃ genotypes not carrying Xa-4 had mean lesion lengths between 28 and 29 cm for both isolates. The Xa-4 carrying parents showed a mean lesion length of 2.7 cm with the avirulent isolate and of 12.4 cm with the virulent isolate. The Xa-4 carrying F₂ and F₃ genotypes had mean lesion lengths of 5.2 and 20.1 cm for the two isolates, respectively. These observations strongly indicate that the Xa-4 gene, carried by the rice genotypes studied (IR28, Cisadane and BR51-282-8), had a considerable residual effect when exposed to virulent isolate PXO99.     

The importance of abortive stoma penetration in the partial resistance and nonhost reaction of adult barley and wheat plants to leaf rust fungi

Summary Early stages of the infection process of Puccinia hordei isolate 1.2.1 and of a P. recondita f.sp. tritici isolate were studied on adult plants of four barley lines and one wheat line. Two of the barley lines are extremely susceptible to P. hordei, the other two have a very high level of partial resistance.A histological study based on a trypan blue staining indicated that stoma penetration by P. hordei isolate 1.2.1 was equally successful on the susceptible as on the partially resistant adult barley plants. Abortion of substomatal vesicles was rare in all lines. These results do not support a hypothesis that mechanisms of partial resistance in adult plants differ from those in seedlings by a substantial abortive stoma penetration.Also in the nonhost combinations wheat-P. hordei and barley-P. recondita f.sp. tritici inhibition of stoma penetration and of substomatal vesicle development appears to play a biologically insignificant role in adult plants.The proportion of stoma penetration on the leaf sheaths of two of the barley lines was as high as on the leaf blades of the flag leaf and the leaf below the flag leaf. There was no evidence for stomatal exclusion as a crucial factor in the relatively low infectibility of leaf sheaths to leaf-blade specialized rust species.     

Main stem movement of Atlantic salmon parr in response to high river temperature

Atlantic salmon become thermally stressed when water temperatures exceed 23 °C. To alleviate this stress, they behaviourally thermoregulate by moving to patches of cold water, often forming large aggregations. These patches are known as thermal refuges. Given the consensus that climate change will increase temperatures in Atlantic salmon catchments, thermal refuges will become increasingly important in minimising summer mortalities. While the behaviour of salmonids within thermal refuges is fairly well understood, less is known about their main stem movement in search of thermal refuges or its thermal and temporal cues. We detail the results of a PIT telemetry study to investigate the main stem movement behaviour of thermally stressed Atlantic salmon parr in a temperature‐impacted river. PIT antennas placed around two thermal refuges and at the upstream and downstream limits of their surrounding reach were used to record the movement of salmonids during a heatwave. We observed parr movement at the upstream and downstream antennas 135 min prior to the occurrence of the midpoint of aggregations in the thermal refuges, indicating that Atlantic salmon parr make reach‐scale movements in search of cool water prior to aggregating. Logistic regression showed that the number of degree hours >28 °C predicted the occurrence of main stem movement with a good degree of accuracy, indicating that this temperature represents a fundamental threshold causing Atlantic salmon parr to move towards cool water. Such data could be instrumental in allowing river managers to place limits on human activity within rivers, allowing salmon populations time to recover following heat stress events.     

Multiple watershed alterations influence fish community structure in Great Plains prairie streams

Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third‐order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream‐associated and impoundment‐associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row‐crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream‐species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species.     

Alkalinity and Hardness: Critical but Elusive Concepts in Aquaculture

Total alkalinity and total hardness are familiar variables in aquatic animal production. Aquaculturists—both scientists and practitioners alike—have some understanding of the two variables and of methods for adjusting their concentrations. The chemistry and the biological effects of alkalinity and hardness, however, are more complex than generally realized or depicted in the aquaculture literature. Moreover, the discussions of alkalinity and hardness—alkalinity in particular—found in water chemistry texts are presented in a rigorous manner and without explanation of how the two variables relate to aquaculture. This review provides a thorough but less rigorous discussion of alkalinity and hardness specifically oriented toward aquaculture. Alkalinity and hardness are defined, their sources identified, and analytical methods explained. This is followed by a discussion of the roles of the two variables in aquaculture, including their relationships with carbon dioxide, pH, atmospheric pollution, ammonia, and other inorganic nitrogen compounds, phytoplankton communities, trace metals, animal physiology, and clay turbidity. Liming and other practices to manage alkalinity and hardness are explained. Changes in alkalinity and hardness concentrations that occur over time in aquaculture systems are discussed. Emphasis is placed on interactions among alkalinity, hardness, water quality, and aquacultural production.     

Effects of Co‐stocking Smallmouth Buffalo,Ictiobus bubalus,with Channel Catfish,Ictalurus punctatus

Proliferative gill disease (PGD) in catfish is caused by the myxozoan Henneguya ictaluri. The complex life cycle requires Dero digitata as the oligochaete host. Efforts to control PGD by eradicating D. digitata have been unsuccessful. Smallmouth buffalo, Ictiobus bubalus, (SMB) are opportunistic bottom feeders and a putative option for controlling D. digitata. In 2011, 15 ponds (0.4 ha) were stocked with 5000 channel catfish, Ictalurus punctatus; 7 of these 15 ponds were also stocked with 300 SMB fingerlings. There were no differences in benthic invertebrate numbers or water quality variables between ponds with or without SMB. At harvest, there were no differences in percent survival, total weight, or catfish feed conversion ratio. In the second year, 18 ponds (0.4 ha) were stocked with 6000 channel catfish. Half the ponds were also stocked with 300 SMB. Sentinel fish were used to estimate disease severity, and pond water was collected for molecular estimation of H. ictaluri actinospore concentrations. Similar to the first year, there were no differences between treatments in any variable tested, including PGD severity in sentinel fish and parasite concentrations in pond water. Under these study conditions, presence of SMB did not have a measureable effect on PGD incidence, parasite density, or overall catfish production.