The Use of Models and Life Tables in Assessing the Role of Natural Enemies

Varley, G. C.; Gradwell, G. R.

doi:10.1007/978-1-4615-6531-4_4

Cited by 4 publications

(7 citation statements)

References 26 publications

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“…MacPhee et al (1988) found that pupal mortality, which they attributed t o predation, was temporally density-dependent in apple orchards between 1967 and 1988. These findings are consistent with results of studies in England, where temporal density-dependent pupal predation was found t o be the only regulating factor, and parasitism by Cyzenis albicuns caused only minor density-independent mortality (Varley & Gradwell, 1968, 1970. Roland found evidence for both spatial and temporal density-dependent predation of winter moth pupae in British Columbia, but found no evidence of regulation by introduced parasitoids (Roland, 1990, and pers.…”

Section: Introductionsupporting

confidence: 87%

“…However, Roland (1990) presented evidence that pupal mortality was as well or better correlated than mortality by introduced parasitoids with population decline in both Nova Scotia and British Columbia. These findings are consistent with results of studies in England, where temporal density-dependent pupal predation was found t o be the only regulating factor, and parasitism by Cyzenis albicuns caused only minor density-independent mortality (Varley & Gradwell, 1968, 1970. MacPhee et al (1988) found that pupal mortality, which they attributed t o predation, was temporally density-dependent in apple orchards between 1967 and 1988.…”

Section: Introductionsupporting

confidence: 85%

“…Carabid and staphylinid bettles are major predators of winter moth pupae in England (Frank, 1967a, b;East, 1974), and have also been implicated along with beetle larvae as major predators of winter moth pupae in British Columbia (Roland, 1990). A large proportion of the predation of winter moth occurs early in the season (45% in the first month), as was also seen in British Columbia (45% by late June) and in England (>50% by August) (Roland, 1990;East, 1974) Mortality due to soil predators was suggested as the principal regulating factor for the winter moth population at Wythani Wood (Varley& Gradwell, 1968,1970Hassell, 1980). Predation was found t o be density-dependent, both spatially (Frank, 1967b;East, 1974) and temporally (Varley & Gradwell, 1968, 1970.…”

Section: Discussionmentioning

confidence: 91%

“…I t has been suggested for studies in Wytham Wood that beetle numbers may be relatively stable and may be partially or completely independent of winter moth numbers since such generalist predators can switch to other foods when winter moth are scarce (Hassell, 1966: Varley & Gradwell, 1971. I t has been suggested for studies in Wytham Wood that beetle numbers may be relatively stable and may be partially or completely independent of winter moth numbers since such generalist predators can switch to other foods when winter moth are scarce (Hassell, 1966: Varley & Gradwell, 1971.…”

Section: Discussionmentioning

confidence: 99%

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Parasitism and predation as agents of mortality of winter moth populations in neglected apple orchards in Nova Scotia

Pearsall

Walde

1994

Ecological Entomology

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1. This study compared the roles of pupal mortality and parasitism in winter moth (Operophtera brurnata) population dynamics in Nova Scotian apple orchards and assessed the importance of beetles as pupal predators.2. The component of pupal mortality termed predation accounted for greater stage-specific mortality of winter moth than parasitism by Cyzenis albicans in four neglected orchards.3. Parasitism by Cyzenis albicans was not spatially density-dependent in any orchard, whereas the predation component of pupal mortality was spatially density-dependent in the two orchards most densely populated by winter moth.4. Field experiments indicated that over 60% of pupal predation may be attributed to beetles, and that about 46% of pupal predation occurred within 4 weeks after pupal drop. .Mortality of introduced populations of winter moth in Nova Scotia resembles that of native populations in England where density-dependent predation regulates the winter moth population and reduces the parasitoid population to minimal levels. The situation in Nova Scotia appears to have changed appreciably since the establishment of parasitoids into the system in the 1950s.

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Section: Introductionsupporting

confidence: 87%

Section: Introductionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Parasitism and predation as agents of mortality of winter moth populations in neglected apple orchards in Nova Scotia

Pearsall

Walde

1994

Ecological Entomology

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“…Table I is an artificial life-table, designed to show the information usually included. Unfortunately, life-tables are usually only prepared for the host insect and if it is hoped to predict the role of a parasitoid or predator, life-tables for these species must also be prepared (Varley, 1970;Benson, 1973a); Varley & Gradwell (1971) have discussed how life-tables and mathematical models may be used to assess the role of natural enemies.…”

Section: No Alivementioning

confidence: 99%

The Biology of Lepidoptera Infesting Stored Products, With Special Reference to Population Dynamics

Benso¹

1973

Biological Reviews

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Summary I. This review provides a background to those aspects of the biology and behaviour of Lepidoptera infesting stored products which may be important in terms of population dynamics. 2. The general biologies of four common species of Phycitid moth are described. 3. Both the fecundity and the fertility of the adult can be influenced by the diet of the female, the size of the female, the numbers of adults per unit area and a variety of environmental factors. 4. Egg mortality may be caused by sterility or cannibalism. Larval mortality may be caused by starvation or cannibalism. Crowding leads to emigration, reduced size and extended developmental period. Pupal and adult mortalities are of minor importance. Pupae may suffer developmental disorders and adults are killed by spiders and lost by emigration. 5. Parasitoids, predators and diseases, which also contribute to mortality of eggs, larvae, pupae and adults, are described. 6. The importance of planning and sampling in order to obtain detailed data on populations are discussed, together with the analysis of the data. 7. It is shown that Lepidoptera which infest stored products and the parasitoids associated with them have proved convenient experimental tools for the elucidation of certain aspects of population dynamics. A small number of studies have succeeded in identifying the main factors or processes responsible for fluctuation or regulation of the densities of these moths.

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Methods for evaluation of natural enemy impacts on invasive pests of wildlands

Driesche¹,

Roy²

2016

Integrating Biological Control Into Conservation Practice

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The Use of Models and Life Tables in Assessing the Role of Natural Enemies

Cited by 4 publications

References 26 publications

Parasitism and predation as agents of mortality of winter moth populations in neglected apple orchards in Nova Scotia

Parasitism and predation as agents of mortality of winter moth populations in neglected apple orchards in Nova Scotia

The Biology of Lepidoptera Infesting Stored Products, With Special Reference to Population Dynamics

Methods for evaluation of natural enemy impacts on invasive pests of wildlands

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