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Title: A rapid method of sampling for aphids on strawberries
Author(s): B. D. Frazer (author), Robert R. McGregor (author)
Date: 1990
Abstract: A rapid system of sampling for strawberry aphids, Chaetosiphon fragaefolii (Cockerell) was developed for use by pest management scouts. Regression equations relating mean numbers of aphids/leaf, variances of those means and the proportion of unifested leaves (Po) were developed from samples of aphids from single leaves. Using the equations, mean aphid density per leaf and standard errors can be estimated from Po and the sample size. The accuracy of the estimations were tested on data from 155 samples from commercial strawberry fields sampled by a professional pest management company. Means estimated from Po were sufficiently accurate for the intended purpose and only 2 hours were required to sample 300 leaves compared to 16 hours when all aphids on all leaves were counted from only 80 leaves. An electronic recorder was programmed to prompt an IPM scout for data entry, allow correction of errors and permit sampling from different subplots within a field.
Department: Biology

Title: Exclusion fences reduce colonization of carrots by the carrot rust fly, Psila rosae (Diptera: Psilidae)
Author(s): Robert S. Vernon (author), Robert R. McGregor (author)
Date: 1999
Abstract: The effectiveness of exclusion fences in preventing the colonization of carrot plantings by the carrot rust fly, Psila rosae (F.), was tested in small field plots. Fenced enclosures were surrounded by panels of mesh nylon window screen l20cm high. Control enclosures were left unfenced. Although the number of first generation P. rosae adults captured on yellow sticky traps was not significantly different between control and fenced enclosures, the number of second generation adults emerging within enclosures was significantly higher in control enclosures than in fenced enclosures. The percentage of unmarketable carrots, % damaged carrots, % urunarketable yield, % damaged yield, and number of lesions per carrot were all significantly higher in control enclosures than in fenced enclosures. We conclude that exclusion fences impede the colonization of carrot plantings by P. rosae and reduce damage to carrots. The results are discussed as they relate to pest management methods for thc carrot rust fly.
Department: Biology

Title: Egg loads and egg masses: Parasitism of Choristoneura rosaceana eggs by Trichogramma minutum after inundative release in a commercial blueberry field
Author(s): Robert R. McGregor (author), Gillian Caddick (author), Deborah Henderson (author)
Date: 2000
Abstract: Inundative releases of Trichogramma minutum Riley were made in a commercial blueberry field in British Columbia, Canada, to determine the extent of dispersal of adult wasps, and to determine whether complete parasitism of eggs within egg masses of the target host [oblique-bandedleafroller (OBLR), Choristoneura rosaceana(Harris)] occurred. Three weekly releases of wasps were made from a single release point in the center of each field during the flight of first generation OBLR adults. Sticky trap, sentinel egg mass and target-host egg mass data all indicated only a limited range of dispersal of T. minutum within the field. In addition, only partial parasitism of egg masses of the target host occurred even in close proximity to the release point. We discuss the importance of determining the response of Trichogramma females to previously-parasitized eggs when using Trichogramma wasps for biological control of lepidopterous species that oviposit large egg masses. [Publisher abstract]
Subject(s): Biological control, Egg parasitoid, Blueberries, Inundative release, Leafroller, Lepidoptera, Tortricidae, Hymenoptera
Department: Biology

Title: Leaf damage and prey type determine search effort in Orius tristicolor
Author(s): Sherah VanLaerhoven (author), David R. Gillespie (author), Robert R. McGregor (author)
Date: 2000
Abstract: Components of search effort were determined for adult females of Orius tristicolor (White) (Hemiptera: Anthocoridae) on bean, Phaseolus vulgaris L., leaves with either western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) or twospotted spider mites, Tetranychus urticae (Koch) (Acari: Tetranychidae) as prey. In the absence of prey, females of O. tristicolor allocated significantly more search time to leaves damaged by western flower thrips than to leaves damaged by twospotted spider mites, artificially damaged leaves or undamaged leaves. In the presence of prey, search time increased with increasing amounts of leaf damage for both prey species, but was not affected by prey species. Amounts of leaf damage or type of prey did not affect giving‐up‐time. The proportion of predators that successfully located thrips increased with increasing amounts of thrips damage on leaves. Females of O. tristicolor appeared to follow some simple, behavioural rules‐of‐thumb for allocation of search effort. The presence and type of damage determined the initial effort allocated to searching a leaf. Subsequent effort was determined by successful capture of prey, regardless of species. The implications of these results for application of Orius spp. for biological control are discussed. [ABSTRACT FROM AUTHOR]
Department: Biology

Title: Intraguild predation by the generalist predator Dicyphus herperus on the parasitoid Encarsia formosa
Author(s): Robert R. McGregor (author), D. R. Gillespie (author)
Date: 2005
Abstract: Predation was measured in the laboratory by Dicyphus hesperus females on patches of greenhouse whitefly (Trialeurodes vaporariorum) pupae. The patches contained different proportions of unparasitized pupae and those parastisized as nymphs by Encarsia formosa. Dicyphus hesperus fed readily on parasitized pupae and the number of parasitized pupae consumed increased with the proportion available indicating a capacity for intraguild predation. However, D. hesperus females did not display a preference for feeding on parasitized pupae versus unparasitized pupae. Dicyphus hesperus adults were released at three densities into greenhouse enclosures containing tomato plants harbouring greenhouse whitefly and immature E. formosa. Numbers of killed and parasitized whitefly nymphs and pupae and the total number of healthy whitefly were compared among Dicyphus density treatments. On upper leaves, the amount of predation on whitefly nymphs was higher at the highest predator density than at the lower density or in enclosures where D. hesperus was not released. On lower leaves, the number of parasitized pupae was lowest with the highest predator density indicating a negative effect of intraguild predation by D. hesperus on E. formosa. Despite this, Dicyphus density did not affect the density of whitefly in the presence of E. formosa. The results are discussed as they relate to concurrent use of D. hesperus and E. formosa for regulation of greenhouse whitefly populations. [Publishers abstract]
Subject(s): Dicyphus hesperus, Encarsia formosa, Intraguild predation, Biological control, Generalist predator, Trialeurodes vaporariorum, Miridae
Department: Biology

Title: Size-selective oviposition by parasitoids and the evolution of life-history timing in hosts: Fixed preferences vs frequency-dependent host selection
Author(s): Robert R. McGregor (author), Bernard D. Roitberg (author)
Date: 2000
Abstract: The influence of size-selective oviposition behaviour by parasitoids on the evolution of life-history timing in their hosts was examined using an optimization model of a two-stage life history similar to a genetic algorithm. Host populations with varying durations of early-larval development were subjected to selection in scenarios where parasitoids had fixed preferences for oviposition on late-stage larvae, or those where parasitoid attack was dependent on the relative frequencies of the two life stages present in the population. Fixed preference for oviposition on late-stage larvae caused positive directional selection on the duration of early-larval development. Surviving individuals remained for as long as possible in the first stage of development in order to avoid parasitoid attack. Frequency-dependent parasitoid attack, in contrast, caused maintenance of variation in the duration of early-larval development. The influence of the fitness payoffs of different life stages on the plasticity of size-selective oviposition behaviour is discussed, as are possible implications of the model results for parasitoid-host population dynamics.
Department: Biology

Title: Prey feeding increases water stress in the omnivorous predator Dicyphus hesperus
Author(s): Alice Sinia (author), Bernard Roitberg (author), Robert R. McGregor (author), D.R. Gillespie (author)
Date: 2004
Abstract: The effects of water stress (produced by water deprivation and prey feeding) on plant feeding were investigated in the omnivorous predator Dicyphus hesperus Knight (Hemiptera: Miridae). The objective was to determine if prey feeding aggravated water deficits and thus increased plant feeding. We measured plant feeding in a factorial experiment where female D. hesperus were prepared for experiments by providing or withholding water and/or prey for 24 h. We then evaluated the amount of plant feeding on Nicotiana tabacum seedlings by the direct observation of insects at three different densities of the prey, Ephestia kuehniella eggs. The amount of plant feeding, as measured by frequency of plant feeding bouts and time spent plant feeding during observation, was significantly greater for water-deprived individuals than for those that had been provided with water. Individuals that had been provided with prey fed on plants at a significantly higher frequency than prey-deprived individuals at two of the prey densities used in the experiment. These results support the hypothesis that plant feeding in zoophytophagous Hemiptera facilitates prey feeding by providing water that is essential for predation. [ABSTRACT FROM AUTHOR]
Department: Biology

Title: Temperature dependant survival and hatching rates of seven species of Coccinellidae
Author(s): B.D. Frazer (author), Robert R. McGregor (author)
Date: 1992
Abstract: The eggs of seven species of locally occurring coccinellids were reared at constant temperatures. The survival of eggs to hatching, rate, and thermal requirements for hatching were determined. The results were used to evaluate the importance of thermal adaptation of coccinellids in selecting them as biological control agents and in determining the relative species composition of locally occurring faunas of coccinellids.
Department: Biology

Title: Sampling plan for Dicyphus hesperus (Heteroptera: Miridae) on green house tomatoes
Author(s): Juan A. Sanchez Sanchez (author), Robert R. McGregor (author), David R. Gillespie (author)
Date: 2002
Abstract: Dicyphus hesperus Knight has good potential as a biological control agent for greenhouse pests in greenhouse tomato crops. The spatial distribution of Dicyphus hesperus was studied and a sampling plan was developed to monitor this species in greenhouse-grown tomatoes. Adults and nymphs are distributed in a more aggregated pattern among plants than within plants. The strong, significant relationship between the mean population density and the proportion of occupied sample units (leaves or plants) makes it possible to use a binomial or presence-absence sampling approach. Presence-absence sampling is an efficient method for crop management purposes because less time is needed to process the samples compared with a method where all insects are counted. At high densities, considering a sample unit to be occupied only when there are more than a determined number of individuals reduces considerably the optimum sample size required.
Subject(s): Binomial sampling, Dicyphus herperus, Spatial distribution
Department: Biology

Title: Searching behaviour of adult female Coccinellidae (Coleoptera) on stem and leaf models
Author(s): B.D. Frazer (author), Robert R. McGregor (author)
Date: 1994
Abstract: Behaviour of locally occurring adult females of seven species of coccinellids was assessed on wooden dowel and paper models that mimicked branching patterns and arrangements of leaf attachments to stems. Ambient temperature and hunger of the beetles were controlled. The movements up or down the main branch of the branch models when contacted from a side branch, duration of searching, and method of leaving leaf models were recorded for 20 beetles of each species.Each species responded to the seven models with different frequencies of behaviours that reflected species-specific modifications of the taxes that lead coccinellids to the tops and terminal parts of plants. Some beetles consistently modified the pattern of responses on die models that was displayed by die species as a whole. The individual modifications could be selected for. The differences in frequencies of behaviours were judged to be sufficient to result in differences in the efficiency with which plants with different architectures were searched.
Department: Biology

Title: The effects of mullein plants (Verbascum thapsus) on the population dynamics of Dicyphus hesperus (Heteroptera: Miridae) in tomato greenhouses
Author(s): Robert R. McGregor (author), Juan Antonio Sanchez (author), David R. Gillespie (author)
Date: 2003
Abstract: The response of Dicyphus hesperus Knight (Heteroptera: Miridae) to whitefly populations in tomato greenhouses was measured in the presence and absence of mullein (Verbascum thapsus L.) as an alternative host plant. The dynamics of the D. hesperus population on tomato (Lycopersicon esculentum Mill.) and on mullein plants were followed through an entire growing season. In houses with mullein plants, more predators occurred on mullein when whitefly density was low on tomato. A mark-release-recapture experiment where rabbit IgG was used as an external marker showed that D. hesperus adults moved from mullein plants to tomato plants. D. hesperus was always more abundant in houses with mullein than in the houses with tomato plants alone. Movements between tomato and mullein plants are discussed as a strategy to optimize predator foraging. The use of mullein as an alternative host plant may contribute to the establishment of D. hesperus and help to preserve the predator population when prey on tomato crops is scarce.
Subject(s): Dicyphus hesperus, Trialeurodes vaporariorum, Predatory Heteroptera, Generalist predators, Verbascum thapsus, Alternative host plant, Omnivory
Department: Biology

Title

Bactericera cockerelli (Sulc), tomato/potato psyllid (Hemiptera: Triozidae)

Author(s)

Robert R. McGregor (author), P. G. Mason (editor), D. R. Gillespie (editor)

Date

2013

Abstract

Book Description "Biological control programmes in Canada 2001-2012": This volume (71 chapters), the fifth in a series documenting biological control programmes in Canada, presents new information on specific insect, weed or plant diseases, some of which are updates of on-going studies on historical biological control projects while other chapters report on biological control efforts for new emerging invasive alien species. In each case, information is presented in a consistent and logical manner, starting with the pest status in Canada, followed by a comprehensive background on previous studies, review of the use of biological control in these programmes, and an evaluation of the biological control efforts and future needs in research or implementation activities. A total of 64 chapters is dedicated to biological control case studies over the past 11 years - 36 on insect pests of agricultural importance and forestry or ornamental pests; 18 on the control of weeds for crops, rangeland, pastures or aquatic areas; and 10 on the biological control of plant disease causal agents. This book is intended for researchers and students in biological control, pest management, ecology and risk assessment.

Chapter 14 "Bactericera cockerelli (Sulc), tomato/potato psyllid (Hemiptera: Triozidae)": This chapter describes the pest status and biological control (parasitoids, predators and pathogens) of B. cockerelli [Trioza cockerelli] (tomato/potato psyllid) in Canada.

Department

Biology

Title: Potential use of Dicyphus hesperus Knight (Heteroptera: Miridae) for biological control of pests of greenhouse tomatoes
Author(s): Robert R. McGregor (author), David R. Gillespie (author), Donald M.J. Quiring (author), Mitch R.J. Foisy (author)
Date: 1999
Abstract: The potential of Dicyphus hesperus Knight as a predator of greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch, was assessed in the laboratory and in a tomato greenhouse. D. hesperus adults fed readily upon both pest species in the laboratory, and nymphs completed development from egg to adult on either whitefly or mites. Whitefly, however, were a superior food for growth and development of D. hesperus compared to mites. Development time was shorter and resulting adult body size was larger for nymphs reared on whitefly compared to those reared on mites. In a greenhouse release, adults oriented to and oviposited on whitefly-infested sentinel plants but did not orient to mite-infested sentinel plants. D. hesperus adults oviposited on greenhouse tomatoes and their progeny completed development in a greenhouse in which both whitefly and mites were present. The results are discussed as they relate to the use of D. hesperus for biological control of pests of greenhouse vegetables.
Department: Biology

Title: Parasitism of the eggs of Lygus shulli and Lygus elisus (Heteroptera: Miridae) by Anaphesiole (Hymenoptera: Mymaridae)
Author(s): Robert R. McGregor (author), David R. Gillespie (author), Donald M. J. Quiring (author), Dawn Higginson (author)
Date: 2000
Abstract: Females of the egg parasitoid Anaphes iole Girault (Hymenoptera: Myrmaridae) accepted and oviposited in eggs of both Lygus shulli Knight and L. elisus Van Duzee (Heteroptera: Miridae) when presented on sections of green bean pod in the laboratory. Resulting A. iole larvae developed normally on eggs of both host species and emerged as adults. The wings of A. iole emerging from L. shulli eggs were significantly larger than those from L. elisus probably because the eggs of L. shulli were larger. Anaphes iole females parasitized only approximately 50% of the eggs available of either host species. This may indicate that 50% of the hosts were suitable and rejected, that 50% were unsuitable for oviposition, or that the structure of bean pods prevents females from finding or ovipositing in 50% of hosts. Anaphes iole has potential for biological control of Lygus spp. on greenhouse vegetables in southwestern British Columbia.
Department: Biology

Title: Cumulative temperature requirements and development thresholds in two populations of Dicyphus hesperus (Hemiptera: Miridae)
Author(s): David R. Gillespie (author), J. Antonio Sanchez Sanchez (author), Robert R. McGregor (author)
Date: 2004
Abstract: Cumulative temperature requirements and development thresholds were determined for two populations of Dicyphus hesperus Knight, 1943 to compare their suitability for use in biological control in greenhouse vegetable crops. The populations were from near Summerland, British Columbia, Canada (49°36′N, 119°40′W, at 334 m elevation) and from near Woody, California, United States of America (35°42′N, 118°50′W, at 500 m elevation). Eggs of the California (CA) population had a higher cumulative temperature requirement for hatch than those of the British Columbia (BC) population. Males of the CA population had a slightly lower cumulative temperature requirement for development from hatch to adult than males of the BC population. The populations did not differ with respect to development thresholds. Males of the CA population experienced higher mortality during development at 35 °C than BC males or females of either population. Males and females of both populations developing at 35 °C were significantly smaller than those developing at more moderate temperatures. The differences between populations with respect to development were biologically trivial. With respect to the effects of temperature on development time under greenhouse conditions, the two populations appear to be equally suitable for use in greenhouses.
Department: Biology

Title: Olfactory responses of the omnivorous generalist predator Dicyphus hesperusto plant and prey odours
Author(s): Robert R. McGregor (author), D.R. Gillespie (author)
Date: 2004
Abstract: Responses of female Dicyphus hesperus Knight (Heteroptera: Miridae) to the odours of plants and prey were tested in the laboratory using a Y-tube olfactometer. Females were attracted to the odour of tomato leaves infested with nymphs of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), compared to uninfested leaves. No such attraction occurred to tomato leaves infested with two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae). When females were simultaneously presented with the odours of whitefly and mite-infested leaves, no preference for either odour was recorded. Similarly, females were attracted to the odour of pepper leaves infested with green peach aphids [Myzus persicae (Sulzer) (Homoptera: Aphididae)] compared to uninfested leaves, but were not attracted to the odour of pepper leaves infested with eggs of cabbage loopers, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae). When aphid-infested and looper-egg-infested pepper leaves were presented simultaneously, no preference for either odour was detected. The results are discussed as they relate to the evolution of infochemical use in generalist omnivorous predators. [ABSTRACT FROM AUTHOR]
Department: Biology

Title: Plant preference in relation to life history traits in the zoophytophagous predator Dicyphus hesperus
Author(s): Juan A. Sanchez (author), David R. Gillespie (author), Robert R. McGregor (author)
Date: 2004
Abstract: Dicyphus hesperus Knight (Heteroptera: Miridae) is an omnivorous predator used to control pests of greenhouse vegetables. Plant preferences and life history traits were studied using nine plant species: Lycopersicon esculentum Mill. (Solanaceae), Capsicum annuum L. (Solanaceae), Verbascum thapsus L. (Scrophulariaceae), Nepeta cataria L. (Lamiaceae), Stachys albotomentosa (Lamiaceae), Nicotiana tabacum L. (Solanaceae), Vicia sativa L. (Fabaceae), Zea mays L. (Gramineae), and Chrysanthemum coronarium L. (Asteraceae). Plants were selected from among potential target crops, natural hosts, plants used for mass rearing, and plants on which D. hesperus has not been reported. Plant preference was measured by multi-choice host plant selection and oviposition assays. Development and reproduction were measured on each of the plant species on both a plant diet alone and on a plant diet supplemented with Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Dicyphus hesperus females and nymphs expressed a preference for some plants over others. Plant preference ranged from low preference plants, such as Z. mays, V. sativa, C. coronarium, and C. annuum, to high preference plants such as V. thapsus, N. tabacum, and S. albotomentosa. When E. kuehniella eggs were supplied, there were few differences in the development time and fecundity of D. hesperus among plants, with the exception of corn and broad bean, where fecundity was lower. On a plant diet alone, nymphs were able to complete their development on V. thapsus, C. annuum, and N. cataria. However, mortality and development time were much lower on V. thapsus than on C. annuum and N. cataria. On most of the plant species D. hesperus did not lay any eggs when fed on a plant diet alone. On V. thapsus, females laid a few eggs and lived longer than when fed on prey. Dicyphus hesperus females tended to prefer host plants on which nymph survival without prey was greatest. [ABSTRACT FROM AUTHOR]
Department: Biology

Title: Leaves or fruit? The potential for damage to tomato fruits by the omnivorous predator, Dicyphus hesperus
Author(s): Robert R. McGregor (author), D.R. Gillespie (author), C.G. Park (author), D.M.J. Quiring (author), M.R.J. Foisy (author)
Date: 2000
Department: Biology

Title: Plant feeding in an Omnivorous Mirid, Dicyphus Hesperus: Why plant context matters
Author(s): David R. Gillespie (author), Sherah L. VanLaerhoven (author), Robert R. McGregor (author), Shannon Chan (author), Bernard D. Roitberg (author)
Date: 2012
Abstract: True omnivores that feed on both plant and animal tissues are not additive combinations of herbivore and predator (carnivore). Because true omnivores must distribute adaptive feeding decisions among two disparate tissue types, understanding the context that plants provide for foraging is important to understand their role in food webs. We varied prey and plant resources to investigate the plant context in an omnivorous true bug, Dicyphus hesperus. The contribution of plant species to fitness was unimportant in water acquisition decisions, but affected numbers of prey consumed over longer periods. In plant communities, in the absence of prey, D. hesperus moved to plants with the highest resource quality. Unlike pure predators facing declining prey, omnivores can use a nondepleting resource to fund future foraging without paying a significant cost. However, the dual resource exploitation can also impose significant constraints when both types of resources are essential. The presence of relatively profitable plants that are spatially separate from intermediate consumer populations could provide a mechanism to promote stability within food webs with plant-feeding omnivores. The effects of context in omnivores will require adding second-order terms to the Lotka-Volterra structure to explicitly account for the kinds of interactions we have observed here.
Department: Biology