Community Stability and the Strategy of Biological Control

1965 ◽  
Vol 97 (8) ◽  
pp. 887-895 ◽  
Author(s):  
K. E. F. Watt
Keyword(s):  
Biological Control ◽  
Trophic Level ◽  
Community Organization ◽  
Biological Control Agent ◽  
Trophic Levels ◽  
Food Plants ◽  
Pest Species ◽  
Community Stability ◽  
The Mean ◽  
The Relationship

AbstractCommunity organization is defined as the mean number of trophic links connecting species of different trophic levels in a community. For the special purposes of this paper, competition is assumed to occur whenever two species are known to eat the same food species. Community stability is defined as the reciprocal of the mean, for all species, of the standard error of logarithms of annual collection sizes. It is thus a measure of stability over time of the species populations in a community. Several authors writing about the relationship between community organization and community stability have insisted that the stability of a complex ecological system increases with the number of avenues by which energy can flow through it. This theory does not seem consistent with the observation that some insect pest species of notorious instability are attacked by a great number of entomophagous species. In this paper we seek additional evidence bearing on the relationship between community organization and stability, using computer analysis of data collected by the Canadian Forest Insect Survey on forest Macrolepidoptera and their food plants. After considering our results, and those of other workers, we postulate the following hypothesis. Stability at any herbivore or carnivore trophic level increases with the number of competitor species at that level, decreases with the number of competitor species that feed upon it, and decreases with the proportion of the environment containing useful food. If this hypothesis is valid, too much competition in the entomophagous trophic level will not allow the species in that level to be instable enough to control an unstable pest. Therefore, the best type of biological control agent is one that has no direct competitor species. Also, the most unstable biological control agents, and hence those capable of controlling an unstable pest, will be polyphagous.

Historical changes in mean trophic level of southern Australian fisheries

2014 ◽  
Vol 65 (10) ◽  
pp. 884 ◽  
Author(s):  
Heidi K. Alleway ◽  
Sean D. Connell ◽  
Tim M. Ward ◽  
Bronwyn M. Gillanders
Keyword(s):  
Trophic Level ◽  
Spatial Data ◽  
South Australia ◽  
Trophic Levels ◽  
High Trophic Level ◽  
Fishing Pressure ◽  
Time Line ◽  
The Mean ◽  
Mean Trophic Level ◽  
Catch Statistics

Decreases in the mean trophic level (MTL) of fishery catches have been used to infer reductions in the abundance of high trophic level species caused by fishing pressure. Previous assessments of southern Australian fisheries have been inconclusive. The objectives of the present study were to provide more accurate estimates of MTL using disaggregated taxonomic and spatial data. We applied the model of MTL to fisheries catch statistics for the state of South Australia from 1951 to 2010 and a novel set of historical market data from 1936 to 1946. Results show that from 1951 to 2010, MTL declined by 0.16 of a trophic level per decade; a rate greater than the global average of 0.10 but equivalent to similar regional investigations in other areas. This change is mainly attributable to large increases in catches of sardine, rather than reductions in the catches of high trophic level species. The pattern is maintained when the historical data is included, providing a time line from 1936 to 2010. Our results show a broadening of the catch of lower trophic levels and suggest care in interpretation of MTL of catches because reductions do not necessarily reflect change in high trophic level species by fishing pressure.

Fisheries

2007 ◽  
Author(s):  
John R. Beddington ◽  
Geoffrey P. Kirkwood
Keyword(s):  
Trophic Level ◽  
Global Scale ◽  
Trophic Levels ◽  
Predatory Fish ◽  
Apex Predators ◽  
The North ◽  
The Mean ◽  
Mean Trophic Level ◽  
Global Statistics ◽  
United Nations Food

The depletion of fish stocks on a global scale is well documented. The United Nations Food and Agriculture Organisation collects statistics on fisheries from all states and, despite obvious shortcomings in the data, a clear picture has been available for some time. Garcia and Grainger (2005) have succinctly documented the position from the latest available date: in 2003, only 3% of stocks were underexploited and 26% moderately exploited, while 52% were fully exploited, 16% were overfished, 7% were depleted, and 1% were recovering from earlier depletion. These global statistics mask two important phenomena. The first, highlighted by Pauly et al. (1998), is that fisheries are increasingly focusing on species lower down in the food-web and the second, highlighted by Myers and Worm (2003, 2005), is that large predatory fish have been particularly reduced in abundance. Both of these analyses are somewhat flawed. In the case of Pauly et al. there are two problems: the first is that the metrics used for the mean trophic level are presented as simple numbers with no estimates of error or indeed sensitivity. In such a situation, the changes in mean trophic levels are hard to interpret, particularly where the mean trophic level changes by at most around 10% over four decades. The second problem has been highlighted by a recent paper by Essington et al. (2006). They point out that in the periods when according to the analysis of Pauly et al. the mean trophic level was declining, in most cases catches of apex predators and indeed all upper trophic levels increased (an exception is the North Atlantic). In the case of the Myers and Worm analysis, they used the catch per unit of effort (CPUE) as an index of abundance. As discussed later in this chapter, there are problems with this, but more importantly for some key apex predators, in particular large tunas, the CPUE declines in the early stages of the fishery, where catches are small, but remains relatively stable under a regime of much higher catches. In such a situation, the interpretation that the CPUE reflects changes in abundance is clearly problematic.

Population dynamics and foraging behaviour of Diaeretus leucopterus (Hymenoptera: Braconidae), and its potential for the biological control of pine damaging Eulachnus spp. (Homoptera: Aphididae)

1996 ◽  
Vol 86 (4) ◽  
pp. 397-405 ◽  
Author(s):  
S.T. Murphy ◽  
W. Völkl
Keyword(s):  
Biological Control ◽  
Foraging Behaviour ◽  
Biological Control Agent ◽  
Host Density ◽  
Scientific Basis ◽  
Control Agent ◽  
Foraging Activity ◽  
Parasitism Rates ◽  
The Mean ◽  
The Impact

AbstractThe Palaearctic pine aphids, Eulachnus agilis (Kaltenbach) and Eulachnus rileyi (Williams) have both been introduced into other continents where they have been reported causing damage to economically important pines. In Euorpe, they are attacked by the specialist parasitoid Diaeretus leucopterus (Haliday) which has been suggested as a possible biological control agent. Here we report on several aspects of the ecology of the parasitoid, conducted on E. agilis in Germany in 1993–94, to provide a more scientific basis for judging its potential for use in biological control. Parasitism of all instars in the field rarely exceeded 10% and was independent of host density. A high percentage of parasitized aphids were hyperparasitized. Measurements of the impact over 16 weeks in a greenhouse-release experiment showed that parasitism rates increased from 2 to 19% but were insufficient to suppress the aphid population below a damaging level. There was evidence of a density-dependent response. Studies on foraging behaviour showed that female parasitoids searched pines by quite extensive walks. There was no relationship between the number of aphids per tree and number of ovipositions, and the mean number of ovipositions per female per tree was 2.5 ± 0.4 eggs. The majority (55.1%) of encountered aphids did not respond to the parasitoids. However, female parasitoids attacked a much higher proportion of aphids that did respond but oviposition success on this group was poor. The number of aphid-infested needles on seedlings increased significantly owing to the parasitoid's foraging activity. On the basis of these results, it is suggested that D. leucopterus is only likely to be of benefit in biological control if used in conjunction with other complementary natural enemies.

scholarly journals Antiviral Protection and the Importance of Wolbachia Density and Tissue Tropism in Drosophila simulans

2012 ◽  
Vol 78 (19) ◽  
pp. 6922-6929 ◽  
Author(s):  
Sheree E. Osborne ◽  
Iñaki Iturbe-Ormaetxe ◽  
Jeremy C. Brownlie ◽  
Scott L. O'Neill ◽  
Karyn N. Johnson
Keyword(s):  
Biological Control ◽  
Biological Control Agent ◽  
Control Strategies ◽  
Control Agent ◽  
Malpighian Tubules ◽  
Contributing Factors ◽  
Content Type ◽  
The Relationship ◽  
Wolbachia Density ◽  
Host Tissues

ABSTRACTWolbachia, a maternally transmitted endosymbiont of insects, is increasingly being seen as an effective biological control agent that can interfere with transmission of pathogens, including dengue virus. However, the mechanism of antiviral protection is not well understood. The density and distribution ofWolbachiain host tissues have been implicated as contributing factors by previous studies with both mosquitoes and flies.Drosophilaflies infected with five diverse strains ofWolbachiawere screened for the ability to mediate antiviral protection. The three protectiveWolbachiastrains were more closely related and occurred at a higher density within whole flies than the two nonprotectiveWolbachiastrains. In this study, to further investigate the relationship between whole-flyWolbachiadensity and the ability to mediate antiviral protection, tetracycline was used to decrease the abundance of the high-density, protectiveWolbachiastrainwAu prior to viral challenge. Antiviral protection was lost when the density of the protectiveWolbachiastrain was decreased to an abundance similar to that of nonprotectiveWolbachiastrains. We determined theWolbachiadensity and distribution in tissues of the same five fly-Wolbachiacombinations as used previously. TheWolbachiadensity within the head, gut, and Malpighian tubules correlated with the ability to mediate antiviral protection. These findings may facilitate the development ofWolbachiabiological control strategies and help to predict host-Wolbachiapairings that may interfere with virus-induced pathology.

scholarly journals Overfishing of marine resources: some lessons from the assessment of demersal stocks off Mauritania

2014 ◽  
Vol 72 (2) ◽  
pp. 414-427 ◽  
Author(s):  
B. Meissa ◽  
D. Gascuel
Keyword(s):  
Trophic Level ◽  
Rapid Development ◽  
Fishing Effort ◽  
Trophic Levels ◽  
Production Model ◽  
Comparative Approach ◽  
Small Scale ◽  
Fishing Pressure ◽  
Ecological Requirements ◽  
The Mean

Abstract The recent, rapid development of fishing in Mauritania offers a good case study for a comparative approach of the resilience of the species exploited there, in the face of increasing fishing pressure. First, we assessed the health of 22 demersal stocks with differing ecological requirements, demographic strategies, and states of exploitation. A dynamic production model was fitted in a framework of Bayesian statistics to abundance indices estimated from scientific trawl surveys or commercial catch per unit efforts. We show that 12 of the 22 stocks assessed are overexploited and 3 are fully exploited. The combined assessment of all 22 stocks demonstrates an overall overexploitation, with total demersal biomass decreasing by ∼75% since 1982 and fishing effort 30% higher than that at maximum sustained yield (40% higher for finfish). Second, relations between states of stocks and life history traits were analysed. The stocks of large and vulnerable species currently undergo the highest fishing pressure and are those that are the most overexploited. At the scale of the community represented by the stocks considered, surveys-based indictors of the mean intrinsic vulnerability, the mean maximum length, and the mean trophic level exhibit a significant decrease from 1990 to 2010. Changes observed in catch-based indicators depend on fishing strategies and are impacted by the recent development of the small-scale fishery. But indicators expressed as a function of a multiplier of fishing effort or fishing mortality clearly decrease, thus confirming that the intensification of exploitation leads to communities dominated by smaller species and lower trophic levels. We conclude that large and high trophic level species, such as white grouper, meagre, guitarfish, and smooth-hound, are markers of ecosystem health and should be considered as sentinel species.

Some parasites of Segestes decoratus Redtenbacher (Orthoptera: Tettigoniidae) and their possible use in the biological control of tettigoniid pests of coconuts in papua new guinea

1987 ◽  
Vol 77 (3) ◽  
pp. 515-523 ◽  
Author(s):  
G. R. Young
Keyword(s):  
Biological Control ◽  
Papua New Guinea ◽  
Palm Oil ◽  
Biological Control Agent ◽  
New Guinea ◽  
Control Agent ◽  
Pest Species ◽  
Cultural Methods ◽  
Oviposition Sites ◽  
Methods Of Control

AbstractA number of tettigoniids belonging to the genera Sexava, Segestes and Segestidea are responsible for severe defoliation of coconut palm, oil palm and Pandanus spp. in Papua New Guinea. Most chemical and cultural methods of control are either impractical or uneconomic. The possibility of biological control was examined with reference to some of the natural enemies of Segestes decoratus Redtenbacher, in particular a parasite of nymphs and adults, Stichotrema dallatorreanum Hofeneder, as well as the egg parasites Triteleia atrella (Dodd), a species of Tetrastichus near T. dubius (Waterston) and a second species of Tetrastichus. It was concluded that S. dallatorreanum contributed to the control of Segestes decoratus in areas with an evenly distributed rainfall and that the parasite had potential as a biological control agent in areas where it is not endemic against pest species of Sexava, Segestes and Segestidea. A survey of the egg parasites showed that they were not effective in controlling the pests as they were only able to parasitize eggs in exposed oviposition sites. Egg predators of unknown identity were responsible for higher egg mortality than were the egg parasites.

A European pest to control a New Zealand weed: investigating the safety of heather beetle, Lochmaea suturalis (Coleoptera: Chrysomelidae) for biological control of heather, Calluna vulgaris

2000 ◽  
Vol 90 (2) ◽  
pp. 169-178 ◽  
Author(s):  
P. Syrett ◽  
L.A. Smith ◽  
T.C. Bourner ◽  
S.V. Fowler ◽  
A. Wilcox
Keyword(s):  
Biological Control ◽  
New Zealand ◽  
National Park ◽  
Biological Control Agent ◽  
Calluna Vulgaris ◽  
Control Agent ◽  
Food Plants ◽  
Invasive Weed ◽  
Heather Beetle ◽  
Lochmaea Suturalis

Heather, Calluna vulgaris (L.) Hull, is a serious invasive weed in the central North Island of New Zealand, especially in Tongariro National Park, a World Heritage Area. Heather beetle, Lochmaea suturalis (Thomson), is a foliage-feeding pest of Calluna in Europe, that was selected as the most promising biological control agent for introduction into New Zealand, because it causes high levels of damage to Calluna in Europe. Host-range tests indicated that L. suturalisposes a negligible threat to native New Zealand plants. Cultivars of Callunagrown as ornamentals are suitable food plants, but are unlikely to be severely affected because L. suturalis requires a damp understorey of moss or litter for successful oviposition and pupation, which is rarely present in gardens. However, mosses and litter occurring under Calluna stands in Tongariro National Park are suitable substrates for eggs and pupae. Lochmaea suturalis released in New Zealand has been freed of parasitoids and a microsporidian disease that attack the beetles in Europe.

scholarly journals Virulence of four entomopathogenic nematode against different stages of the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Mürşide Yağcı ◽  
Tuğba Akdeniz Fırat ◽  
F. Dolunay Erdoğuş ◽  
Müge Şahin
Keyword(s):  
Biological Control ◽  
Ceratitis Capitata ◽  
Biological Control Agent ◽  
Entomopathogenic Nematode ◽  
Fruit Fly ◽  
Adult Mortality ◽  
Control Agent ◽  
Mediterranean Fruit Fly ◽  
Pest Species ◽  
Negative Effects

Abstract Background Ceratitis capitata Wiedemann (Diptera: Tephritidae) (Mediterranean fruit fly), is one of the important polyphagous pest species in the world that harms almost all fruits causing significant yields losses. Control of this pest which is on the quarantine list of many countries is highly important. Due to the negative effects of chemical control on the environment and human health, biological control approaches have gained importance. Entomopathogenic nematodes (EPNs) are a potential biological control agent that can be used for effectively controlling the Medfly. Results In this study, effects of four EPNs species on larvae, pupae and adults of Medfly were investigated under laboratory conditions. Four different concentrations of EPNs species were used against each stage of the pest. It pest showed different sensitivity to different concentrations of each of the tested EPNs. High mortality rate of 94% was caused by Heterorhabditis bacteriophora (11 KG),, followed by H. bacteriophora (TOK-20) with 91%, Steinernema carpocapsae (85%) and S. feltiae (Tokat-Emir) with 71% at highest concentration (200 IJ/larvae. The highest effect on adult mortality (100%) was recorded by the species S. feltiae (Tokat-Emir) at the highest concentration (200 IJ/adult) in the trials, followed by H. bacteriophora (11 KG) with 92%, H. bacteriophora (TOK-20) with 91% and S. carpocapsae (Tokat-Bakışlı05) with 87.37% mortality rates at the same concentrations. Conclusions It was determined that the EPNs tested in this study had insecticidal properties and they might be used in biological control programs against the Medfly.

scholarly journals Compatibility of Atheta coriaria with other biological control agents and reduced-risk insecticides used in greenhouse floriculture integrated pest management programs for fungus gnats

2006 ◽  
Vol 138 (5) ◽  
pp. 712-722 ◽  
Author(s):  
S. Jandricic ◽  
C.D. Scott-Dupree ◽  
A.B. Broadbent ◽  
C.R. Harris ◽  
G. Murphy
Keyword(s):  
Biological Control ◽  
Integrated Pest Management ◽  
Pest Management ◽  
Biological Control Agent ◽  
Entomopathogenic Nematode ◽  
Steinernema Feltiae ◽  
Pest Species ◽  
Insect Growth Regulators ◽  
Fungus Gnats ◽  
Atheta Coriaria

AbstractFungus gnats (FG) (Diptera: Sciaridae: Bradysia spp.) are economically important pests of greenhouse flowers. Larvae feed on root tissue and transmit a variety of phytopathogens. Atheta coriaria (Kraatz) (Coleoptera: Staphylinidae) is a new biological control agent (BCA) for FG. To support its successful use by the greenhouse industry, its compatibility with current integrated pest management (IPM) programs used in floriculture was assessed. This included investigations of prey preference, possible detrimental interactions with other soil-dwelling BCAs, and the toxicity to A. coriaria of registered and novel insecticides. Atheta coriaria showed little preference among eggs of different pest species or between pest eggs and eggs of the intraguild predator Hypoaspis aculeifer (Canestrini) (Acari: Mesostigmata: Laelapidae). It preferred FG 1st-instar larvae to larvae and pupae of other soil-dwelling pests. The entomopathogenic nematode Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) was compatible with A. coriaria, but H. aculeifer mites fed on A. coriaria larvae. Insect growth regulators with limited contact activity (e.g., diflubenzuron) were compatible with adult A. coriaria and had minimal effects on larvae compared with other insecticides. Atheta coriaria can be incorporated into an IPM program for FG if harsh insecticides are avoided, but interactions with predatory mites, as well as its effectiveness against other greenhouse pests when FG are present, require further investigation.

Multi-Center Calibration of the Second Reference Material for Thromboplastin, Rabbit, Plain, Coded CRM 149R

1991 ◽  
Vol 65 (03) ◽  
pp. 263-267 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Reference Material ◽  
Standard Error ◽  
Standard Errors ◽  
Sensitivity Index ◽  
Long Term Stability ◽  
Significant Bias ◽  
The Mean ◽  
The Relationship ◽  
International Sensitivity Index

SummaryIn a collaborative trial of eleven laboratories which was performed mainly within the framework of the European Community Bureau of Reference (BCR), a second reference material for thromboplastin, rabbit, plain, was calibrated against its predecessor RBT/79. This second reference material (coded CRM 149R) has a mean International Sensitivity Index (ISI) of 1.343 with a standard error of the mean of 0.035. The standard error of the ISI was determined by combination of the standard errors of the ISI of RBT/79 and the slope of the calibration line in this trial.The BCR reference material for thromboplastin, human, plain (coded BCT/099) was also included in this trial for assessment of the long-term stability of the relationship with RBT/79. The results indicated that this relationship has not changed over a period of 8 years. The interlaboratory variation of the slope of the relationship between CRM 149R and RBT/79 was significantly lower than the variation of the slope of the relationship between BCT/099 and RBT/79. In addition to the manual technique, a semi-automatic coagulometer according to Schnitger & Gross was used to determine prothrombin times with CRM 149R. The mean ISI of CRM 149R was not affected by replacement of the manual technique by this particular coagulometer.Two lyophilized plasmas were included in this trial. The mean slope of relationship between RBT/79 and CRM 149R based on the two lyophilized plasmas was the same as the corresponding slope based on fresh plasmas. Tlowever, the mean slope of relationship between RBT/79 and BCT/099 based on the two lyophilized plasmas was 4.9% higher than the mean slope based on fresh plasmas. Thus, the use of these lyophilized plasmas induced a small but significant bias in the slope of relationship between these thromboplastins of different species.

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