Home About us Contact
|
Home About us Contact | ||
|
|
||
Emergence Rate (emergence + rate)
Selected AbstractsEffects of relative humidity on cocoon formation and survival in the braconid wasp Cotesia glomerataPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2008JUN TAGAWA Abstract The effects of relative humidity (RH) on cocoon formation and survival in the braconid parasitoid wasp Cotesia glomerata (L.) (Hymenoptera: Braconidae) are investigated under various humidity conditions (50, 75, 90, 95 and 100% RH) at 20 °C and under an LD 16 : 8 h photoperiod. The mortality rate at the time of egression from hosts under 100% RH is significantly higher than for other RHs. Cocoon clusters formed at 100% RH spread significantly more than those formed at 50, 75, or 90% RH. Developmental periods differ significantly among RHs under which wasps developed. The mean period from the egression from hosts to adult emergence is 8.7 days when developed at 50,95% RHs, and 8.0 days at 100% RH. The emergence rates of C. glomerata that are maintained under the same humidity conditions after egression from hosts are not significantly different among RHs. However, emergence rates from cocoons that are transferred from 100% RH to 50 and 75% RH are < 70%, although the rates are > 90% in most cases. Some wasps do not emerge from cocoons: more than 60% die after adult eclosion at all RHs; the relative frequency of adult deaths is approximately 90% at 50% RH. Relative humidity influences the cluster and cocoon status strongly: both good clusters and cocoons are formed at low RHs. Emergence rates from cocoons of different ranks are significantly different: the rates of low-rank cocoons are low at low RHs. The survival of C. glomerata is affected strongly by RH through cocoon formation. [source] Dispersal and influences on movement for Anoplophora glabripennis calculated from individual mark-recaptureENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2005J.S. Bancroft Abstract We conducted an individual mark-release-recapture experiment on the beetle, Anoplophora glabripennis Motchulsky (Coleoptera: Cerambycidae). This invasive beetle has been introduced from Asia to Europe and North America and poses a serious threat to several important species of tree. Eradication efforts may benefit from knowledge of dispersal behaviour. Trees were cut and held to determine emergence rate of A. glabripennis. Unique marks were painted onto 912 beetles released into a group of 165 trees in Gansu, China. Data on subsequent sightings of beetles were used in a truncated diffusion model to calculate flight distances. Characteristics of the trees and climatic information were used in statistical tests for influence on movement. A total of 2245 sightings of beetles were observed and 29% of marked beetles were resighted. The scanning technique using binoculars was 90% effective in finding beetles and provided 81% accuracy for determining the sex of the beetles. Experimental manipulation of density quantified how A. glabripennis congregated on unoccupied trees and were repulsed from crowded hosts. The seasonal emergence rate of adults declined exponentially from July 20 to August 5. The results suggested A. glabripennis fly to nearby host trees at a rate of 34% per day. Median flight distance was estimated at 20 m per day. Statistical analysis with a generalized linear model tested the beetle's propensity to leave a tree and distance of flight. Generally, beetle movement showed a significant response to beetle density, weather conditions, beetle size, and tree size, in that order. The techniques developed here improve on previous recapture techniques to quantify dispersal and can be useful for analysing populations of other organisms. [source] Comparative Effects of NaCl and Polyethylene Glycol on Germination, Emergence and Seedling Growth of CowpeaJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2002B. Murillo-Amador Abstract Seeds of Paceño and Cuarenteño cultivars of cowpea (Vigna unguiculata L. Walp.) were tested for salt and drought tolerance at germination, seedling emergence and early seedling growth in NaCl and PEG-8000 solutions of different osmotic potentials (0, ,0.2, ,0.4, ,0.6, and ,0.8 MPa). Daily and final germination and emergence percentage, as well as germination and seedling emergence rate, and seedling growth were recorded under controlled conditions. Results showed that germination and emergence rate were delayed by both solutions in both cultivars, with differences between cultivars among growth stages, given that cultivar Cuarenteño, showed a higher germination rate than Paceño in NaCl, but Paceño was less affected by NaCl and PEG solutions at the emergence stage. Sodium chloride had a lesser effect on both cultivars in terms of germination rate, emergence rate and the final germination and emergence percentage than did PEG-8000. This conclusively proves that the adverse effect of PEG-8000 on germination, emergence and early seedling growth was due to the osmotic effect rather than the specific ion. Seedling growth was reduced by both stresses, but NaCl usually caused less damage than PEG to cowpea seedlings, suggesting that NaCl and PEG acted through different mechanisms. Zusammenfassung Vergleich der Wirkungen von NaCl und Polyethylenglykol auf die Keimung, das Auflaufen und das Sämlingswachstum von Kuhbohne Samen von Paceño- und Cuarenteño-Kultivaren von Kuhbohne (Vigna unguiculata L. Walp.) wurden hinsichtlich Salz- und Dürretoleranz zum Zeitpunkt der Keimung, des Sämlingsauflaufens und des frühen Sämlingswachstums in NaCl- und PEG-8000-Lösungen mit unterschiedlichem osmotischen Potential (0, ,0.2, ,0.4, ,0.6 und ,0.8 MPa) untersucht. Tägliche und abschließende Keimungs- und Auflaufprozente sowie Keimung und Sämlingsauflaufrate und Sämlingswachstum wurden unter kontrollierten Bedingungen bestimmt. Die Ergebnisse zeigen, dass die Keimung und die Auflaufrate durch beide Lösungen verzögert wurden bei beiden Kultivaren, wobei Unterschiede zwischen den Kultivaren hinsichtlich der Wachstumsstadien auftraten; der Kultivar Cuarenteño zeigte eine höhere Keimungsrate als Paceño in NaCl, während Paceño weniger beeinflusst wurde durch NaCl und PEG-Lösungen im Auflaufstadium. Natriumchlorid hatte einen geringeren Einfluss bei beiden Kultivaren hinsichtlich der Keimungsrate, der Auflaufrate und der abschließenden Keimungs- und Auflaufprozente als PEG-8000. Dies bestätigt, dass der ungünstige Einfluss von PEG-8000 auf die Keimung, das Auflaufen und das frühe Sämlingswachstum eine Folge des osmotischen Einflusses und nicht einer spezifischen Ionenwirkung ist. Sämlingswachstum war durch beide Behandlungen beeinträchtigt, aber NaCl zeigte meist eine geringere Schädigung als PEG bei Kuhbohnensämlingen; das lässt vermuten, dass NaCl und PEG durch unterschiedliche Mechanismen einwirken. [source] Laboratory and field evaluations of extracts from Rhododendron molle flowers as insect growth regulator to imported cabbage worm, Pieris rapae L. (Lepidoptera:Pieridae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001G. H. Zhong The insect growth regulating properties of rhodojaponin-III (Abbr. R-III) and ethyl acetate (EtOAc) extract from Rhododendron molle G. Don flowers against imported cabbage worm, Pieris rapae L., were determined under laboratory and field conditions. The values of IC50 (the median of concentration for inhibiting weight increase) for R-III and EtOAc extract were 6.78 p.p.m. and 70.29 p.p.m. against 3rd instar larvae and 13.72 p.p.m. and 346.00 p.p.m. against 5th instar larvae, respectively. R-III and EtOAc extract also could reduce pupating rate, pupal weight, emergence rate and extend the duration of development. Thus development of insects was inhibited significantly and development index decreased. R-III would be superior to toosendanin as insect growth regulator. EtOAc extract 1000 p.p.m. mixture with molosultap 500 p.p.m. could achieve an effective control rate of 87.34% against P. rapae in field trials when adjusted cumulative insect-days were used as index. [source] Indirect facilitation and competition in tree species colonization of sub-Mediterranean grasslandsJOURNAL OF VEGETATION SCIENCE, Issue 3 2006Georges Kunstler Abstract: Questions: In the absence of herbivores, what is the importance of shrub facilitation for the colonization of grasslands by Fagus sylvatica and Quercus pubescens? Is there an indirect facilitative effect of shrubs on tree seedlings by limiting herb competition? Location: Causse du Larzac, southern Massif Central, France. Methods: We conducted field experiments on the facilitative role of shrubs in seedling emergence and survival, in relation to potential negative effects of shading and the presence of herbs. The effects of shade and herbs on allocation and root morphology were analysed in a pot experiment. Results: According to these experiments, the establishment of both tree species was facilitated by shrubs, but the two species differed in the processes underlying this facilitation. Shade directly facilitates the emergence rate of both species. Shade also indirectly facilitates Fagus survival by limiting herb competition. No indirect facilitation of Quercus survival was detected. These differences reflect variation in the tolerance of herb competition by seedlings of the two species. The tolerance of herb competition by Quercus seedlings allows regeneration over a wide area under each shrub and some regeneration events in grasslands at low grazing intensity. In contrast, for Fagus, only a narrow area under each shrub is suitable; regeneration is zero in grassland. The high tolerance of herb competition by Quercus seedlings may result from the avoidance of root competition. Conclusions In grasslands with severe drought stress, and almost obligatory shrub facilitation for tree seedling regeneration, the tolerance of herb competition may alter the precise role of facilitation in the colonization process. [source] Adenanthera pavonina trypsin inhibitor retard growth of Anagasta kuehniella (Lepidoptera: Pyralidae)ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 4 2010Maria Lígia Rodrigues Macedo Abstract Anagasta kuehniella is a polyphagous pest that feeds on a wide variety of stored products. The possible roles suggested for seed proteinase inhibitors include the function as a part of the plant defensive system against pest via inhibition of their proteolytic enzymes. In this study, a trypsin inhibitor (ApTI) was purified from Adenanthera pavonina seed and was tested for insect growth regulatory effect. The chronic ingestion of ApTI did result in a significant reduction in larval survival and weight. Larval and pupal developmental time of larvae fed on ApTI diet at 1% was significantly longer; the larval period was extended by 5 days and pupal period was 10 days longer, therefore delaying by up to 20 days and resulting in a prolonged period of development from larva to adult. As a result, the ApTI diet emergence rate was only 28% while the emergence rate of control larvae was 80%. The percentage of surviving adults (%S) decreased to 62%. The fourth instar larvae reared on a diet containing 1% ApTI showed a decrease in tryptic activity of gut and that no novel proteolytic form resistant to ApTI was induced. In addition, the tryptic activity in ApTI -fed larvae was sensitive to ApTI. These results suggest that ApTI have a potential antimetabolic effect when ingested by A. kuehniella. © 2010 Wiley Periodicals, Inc. [source] Biological and biochemical characteristics for quality control of Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae) reared on a liver-based dietARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2008Luca Sighinolfi Abstract Biological and biochemical parameters of a flightless strain of Harmonia axyridis, fed on a pork liver,based artificial diet and on Ephestia kuehniella eggs as controls, were compared. The diet-grown larvae showed a significantly longer developmental time and a lower adult emergence rate compared to control larvae. The weights of the newly emerged adults were significantly higher for adults fed E. kuehniella eggs during their larval stages than fed the artificial diet. In contrast, larval food source had no effect on the duration of the pre-oviposition period or adult longevity. For adults fed on E. kuehniella eggs as larvae, a significantly longer pre-oviposition period, lower daily weight gain and fecundity were found for the diet-fed females compared to those fed on E. kuehniella eggs throughout the life span. The adult food source had no significant effect on longevity and fertility. Lower amino acid and fatty acid contents (in particular C16:1 and C18:3n-3) were found for the prepupae and newly emerged females obtained from diet-reared larvae compared to controls. Deficiencies in fatty acids C16:1 and C18:3n-3 were also observed in females obtained from E. kuehniella egg-reared larvae and fed on diet from adult emergence. The analyses of the foods showed deficiencies in artificial diet, especially for some amino and fatty acids. The results suggest a non-optimal composition of the artificial diet and some possibilities for its improvement. However, this polyphagous predator could be reared from first instar larvae to fully reproductive adults on a pork liver,based artificial diet. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley-Liss, Inc. [source] Vegetative growth and development of irrigated forage turnip (Brassica rapa var. rapa)GRASS & FORAGE SCIENCE, Issue 4 2008J. E. Neilsen Abstract Field and greenhouse experiments were conducted to identify visual markers and predictors of changes in the vegetative growth rate of forage turnip (Brassica rapa var. rapa) as a potential tool to improve the timing of inputs of N and irrigation to periods of maximum demand. The onset of root expansion, which was associated with a colour change and the death of cotyledons, was identified as a critical marker for the beginning of the rapid growth of the crop and the accumulation of starch in the storage root but indicators of subsequent changes in vegetative growth rate were not identifiable. The results suggested that management inputs can be more readily targeted to the beginning of the exponential growth phase but targeting of later vegetative growth stages will remain arbitrary. The vegetative growth and development of the crop was also studied to elucidate the process of leaf emergence and senescence (turnover) as they affected both leaf and root yield. The sequential senescence of leaves, which began immediately after cotyledon death, and translocation of carbohydrate to the storage root, coupled with high leaf area index (LAI), probably account for the high growth rates of 220 kg ha,1 day,1 maintained for periods of 10 weeks after the onset of root expansion. High yields can be expected if high LAI is maintained by ensuring that leaf emergence rates are not limited by nutrient or water deficiencies and leaves are protected from insect pests. Forage turnip is particularly robust because new leaf continues to emerge as older and damaged leaves senesce and carbohydrate is stored as starch in the storage root. [source] Soil Temperature and Planting Depth Effects on Tef EmergenceJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2009S. Evert Abstract Tef [Eragrostis tef (Zucc.) Trotter] is an annual C4 grass crop that originated in Ethiopia. It has potential as a grain crop in the Great Plains because of its tolerance to drought and high temperatures. In Ethiopia, tef seed is typically broadcast on the soil surface and lightly incorporated. Shallow planting depths are used because the seed is very small and emergence can be limited by soil crusting. If planting equipment is to be used, planting depth may be important for successful tef production. The objective of this study was to identify optimal depths and soil temperatures to aid in developing tef planting recommendations for the central Plains. Tef was planted at five depths (0, 0.6, 1.3, 2.5 and 5.0 cm) in pots filled with a silt loam soil, and pots were placed in growth chambers at four temperature regimes (day/night: 15/19 °C; 19/23 °C; 23/27 °C and 27/31 °C). No plants emerged from the 5.0-cm depth, so this depth was not included in the analysis. Emergence was greatest for planting depths of 0.6 and 1.3 cm and lower at 0 and 2.5 cm depths. Temperature did not affect final emergence, measured 21 days after planting (DAP), but did influence emergence rates during the first 9 DAP. Plant dry matter production increased as planting depth increased, but plant dry matter per pot was not different among planting depths greater than 0.9 cm, suggesting that compensation between plants across different plant densities began early in the plants' life cycles. Our results show that tef seed can emerge from depths between 0.6 and 1.3 cm and that soil temperatures below 19 °C can slow emergence but should not affect final stands. [source] Effects of relative humidity on cocoon formation and survival in the braconid wasp Cotesia glomerataPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2008JUN TAGAWA Abstract The effects of relative humidity (RH) on cocoon formation and survival in the braconid parasitoid wasp Cotesia glomerata (L.) (Hymenoptera: Braconidae) are investigated under various humidity conditions (50, 75, 90, 95 and 100% RH) at 20 °C and under an LD 16 : 8 h photoperiod. The mortality rate at the time of egression from hosts under 100% RH is significantly higher than for other RHs. Cocoon clusters formed at 100% RH spread significantly more than those formed at 50, 75, or 90% RH. Developmental periods differ significantly among RHs under which wasps developed. The mean period from the egression from hosts to adult emergence is 8.7 days when developed at 50,95% RHs, and 8.0 days at 100% RH. The emergence rates of C. glomerata that are maintained under the same humidity conditions after egression from hosts are not significantly different among RHs. However, emergence rates from cocoons that are transferred from 100% RH to 50 and 75% RH are < 70%, although the rates are > 90% in most cases. Some wasps do not emerge from cocoons: more than 60% die after adult eclosion at all RHs; the relative frequency of adult deaths is approximately 90% at 50% RH. Relative humidity influences the cluster and cocoon status strongly: both good clusters and cocoons are formed at low RHs. Emergence rates from cocoons of different ranks are significantly different: the rates of low-rank cocoons are low at low RHs. The survival of C. glomerata is affected strongly by RH through cocoon formation. [source] The Effect of Fruit Age on Seed Germinability of a Heterocarpic Species, Atriplex sagittataPLANT BIOLOGY, Issue 6 2004B. Mandák Abstract: Atriplex sagittata is an annual heterocarpic plant that produces three different fruit types (termed A, B, and C). To examine the consequence of heterocarpy on germinability patterns over long time periods, we compared seed germinability of different fruit types that had been stored for up to 8 years. While germinability of non-dormant type C fruits in distilled water was high (up to 100 %) in the first 2 years, it rapidly decreased over time. Dormant fruit types A and B showed increased germinability up to 7 years, though loss of germinability was lower for type B than for type A fruits. Eight-year-old fruits of all types had significantly lower germinability than younger fruits, probably due to loss of viability. Heterocarpy, therefore, ensures that emergence rates for seedlings of A. sagittata will be maintained over relatively long periods, even in years of strong disturbance when all adult plants may be destroyed. The experiment further showed that germinability of all fruit types in high concentrations of salt, as compared with water treatment, changed over the course of 8 years. Whilst dormant types (A and B) of A. sagittata show increased germinability with age of the seed in water treatment, they significantly lose germinability over time with salinity treatment. Type C fruit was not influenced by salt in the first year, but germinability rapidly decreased with time. It follows that the species is able to germinate under high salt concentration in the first year, but this advantage gradually disappears. [source] Tolerance of barley seed germination to cold- and drought-stress expressed as seed vigourPLANT BREEDING, Issue 3 2003O. Chloupek Abstract In barley, high seed vigour is a precondition for rapid and homogenous field emergence and good malting quality. Seed vigour was defined as germination percentage under stress conditions (10°C, drought stress - 2 Bars) in 7-8 barley varieties grown in 7-8 locations in the Czech Republic over 7 years. Three of the 7 years were not suitable for high seed quality, probably because of unsuitable weather, as average seed vigour reached only 61, 77 and 86%, respectively. In the remaining 4 years, the average vigour exceeded 94%. The impact of variety on seed vigour was higher in the ,bad years' and the impact of location was higher in the other years. Varieties with higher vigour from all locations in the ,bad years' were identified. Lower vigour was related to the high occurrence of fungi (indicated by ergosterol assays) and to lower field emergence rates of seed samples. The results support the possibility of selecting for improvement of barley seed vigour, which is related to tolerance to various conditions during emergence and to homogenous malting. [source] Seasonal variations in production and development of leather leaf fern leaves,ANNALS OF APPLIED BIOLOGY, Issue 2 2003J O STRANDBERG Summary Production and development of leatherleaf fern leaves were studied using containerised plants growing in a shade house. Leaf development was partitioned into seven arbitrary development stages; the time needed for leaves to progress through each developmental stage was used to measure days required to reach maturity. Measurements were made twice each week throughout 1997. Means and variances with in emergence rates of new leaves and time needed for new leaves to pass through six leaf development stages were calculated for 26 14-day periods throughout the year and compared with degree days, solar radiation, soil temperature, and daylight hours accumulated during the periods. Leaf production rates ranged from 0.15,0.73 leaves day,1 plant,1. The average time from emergence to maturity was 22.6 days. Both leaf production and development rates varied greatly with the seasons, and were strongly associated with the weather variables measured, but significant cyclic rate fluctuations unrelated to weather were also detected. Leaf emergence rates were more strongly related to average soil temperature, whereas leaf development rates to maturity were more strongly related to solar radiation and degree days. [source] The role of successional stage and small-scale disturbance for establishment of pioneer grass Corynephorus canescensAPPLIED VEGETATION SCIENCE, Issue 3 2010Okka Tschöpe Abstract Question: Which mechanisms promote the maintenance of the protected pioneer grass Corynephorus canescens in a mosaic landscape? Which are the interactive effects of small-scale disturbances, successional stage and year-to-year variation on early establishment probabilities of C. canescens? Location: Brandenburg, NE Germany. Methods: We measured emergence and survival rates over 3 yr in a sowing-experiment conducted in three successional stages (C. canescens -dominated site, ruderal forb site and pioneer forest) under two different regimes of mechanical ground disturbance (disturbed versus undisturbed control). Results: Overall, disturbance led to higher emergence in a humid year and to lower emergence in a very dry year. Apparently, when soil moisture was sufficient, the main factor limiting C. canescens' establishment was competition, while in the dry year, water became the limiting factor. Survival rates were not affected by disturbance. In humid years, C. canescens emerged in higher numbers in open successional stages while in the dry year, emergence rates were higher in late stages, suggesting an important role of late successional stages for the persistence of C. canescens. Conclusions: Our results suggest that small-scale disturbances can promote germination of C. canescens. However, disturbances should be carefully planned. The optimal strategy for promoting C. canescens is to apply disturbances just before seed dispersal and not during dry years. At the landscape scale, a mosaic of different vegetation types is beneficial for the protected pioneer grass as facilitation by late-successional species may be an important mechanism for the persistence of C. canescens, especially in dry years. [source] | |||||||||||||||||||||||||