bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predator–prey interactions: olfactory adaptations of generalist and specialist predators
Authors: Dickens Joseph C. 
Published: March 2003

Summary1 Olfactory responses of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), a generalist predator, Podisus maculiventris (Say) (Hemiptera, Heteroptera: Pentatomidae) (Pm), and a specialist predator, Perillus bioculatus (F.) (Hemiptera, Heteroptera: Pentatomidae) (Pb) were investigated. Volatiles tested included 20 compounds emitted by undamaged potato plants (Solanum tuberosum), plants that had been artificially damaged, or plants damaged by feeding by CPB larvae.2 Coupled gas chromatography/electroantennogram detector (GC/EAD) recordings revealed five compounds for which reliable responses were recorded from CPB antennae: (E)‐2‐hexen‐1‐ol, (Z)‐3‐hexen‐1‐ol, (±)‐linalool, nonanal, methyl salicylate, and indole. Both Pm and Pb responded selectively to the same compounds as the CPB with exceptions: (1) (Z)‐3‐hexenyl butyrate elicited reliable responses for both Pm and Pb, and (2) (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol were inactive for Pm and Pb under these conditions. Dose–response curves showed that CPB was at least 100 times more sensitive to (E)‐2‐hexen‐1‐ol than were the predators. Both predators were more sensitive to each of the other compounds than were CPB. Both CPB and Pm were attracted to a five component blend comprising (E)‐2‐hexen‐1‐ol, (Z)‐3‐hexen‐1‐ol, (±)‐linalool, nonanal and methyl salicylate. However, attraction of CPB to the blend occurred only with lower doses of (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol.3 These results show that the herbivore (CPB) has olfactory receptors which are more sensitive to constitutive host plant volatiles, e.g. green leaf volatiles, while both generalist (Pm) and specialist (Pb) predators are more sensitive to systemic volatiles produced in response to prey feeding. Keywords Colorado potato beetle, constitutive compounds, host plant, induced compounds, olfaction, Perillus bioculatus, Podisus maculiventris, predator, prey, tritrophic.
The influence of understory nectar resources on parasitism of the spruce budworm Choristoneura fumiferana in the field
Authors: Cappuccino Naomi , Houle Marie‐José , Stein Jayson 
Published: March 2003

SUMMARY1 Nectar provided by flowering plants has been suggested as an important factor enhancing parasitism rates of herbivorous insects. Artificial nectar has been shown to increase parasitoid longevity and fecundity in laboratory studies.2 We studied the influence of understory nectar on parasitism of the spruce budworm Choristoneura fumiferana in a field experiment in which we either removed understory flowering herbs or sprayed a sucrose solution on the understory vegetation in 0.25 ha quadrats.3 Cohorts of laboratory‐reared second instars were transferred the field to evaluate parasitism in the quadrats. The larvae were harvested as fifth instars and reared for parasitoids.4 Parasitoids of early instars caused greater mortality in the supplemental sucrose treatment than in the vegetation‐removal treatment or the control. Parasitoids of older larvae did not respond to the treatments. Larger‐scale treatments may be necessary to elicit a response by the larger parasitoids that attack older larvae.
Potential for biological control of native competing vegetation using native herbivores
Authors: Valenti Michael A. , Berryman Alan A. , Ferrell George T. 
Published: March 2003

Summary1 The use of native natural enemies to combat native pests has received proportionately less consideration than other viable approaches to biological control. Successful attempts at augmentation, conservation, preservation, and enhancement of the effectiveness of natural enemies have been limited.2 However, this approach to biological control should be re‐examined, placing emphasis on intentional manipulation of population dynamics to encourage the natural tendencies of populations to grow in the absence (or during the delay in resurgence) of certain regulating forces.3 We discuss theoretical and empirical evidence that suggests native herbivorous insects have the potential to be manipulated successfully as biological control agents for native competing vegetation.
Survival, growth and gall formation by Phytolyma lata on Milicia excelsa established in mixed‐species tropical plantations in Ghana
Authors: Nichols J. Doland , Ofori Daniel A. , Wagner Michael R. , Bosu Paul , Cobbinah Joseph R. 
Published: March 2003

Summary1 Milicia excelsa (Moraceae) is an important timber tree in much of Africa and when grown in monocultural plantations has been subject to nearly complete destruction by gall‐forming psyllids in the genus Phytolyma.2 We tested the impact on susceptibility to Phytolyma spp. of planting Milicia excelsa in various densities and species mixtures. Replicated plantings consisting of 11, 25, 50 and 100% Milicia in mixtures with Terminalia superba (Combretaceae) were established at a site surrounded by natural forest and in an agricultural area.3 In addition at the agricultural site, 50–50 mixtures of Milicia excelsa with Albizia adianthifolia (Mimosaceae), Tectona grandis (Verbenaceae), Khaya ivorensis. (Meliaceae), Ceiba pentandra (Bombacaceae) and a mixture combining all species were planted.4 Two months after planting, gall numbers were significantly lower in the 11% Milicia mixtures at the forest site. Gall numbers were also significantly lower at the forest site than at the agricultural site, for all densities of Milicia. At 6 months, dieback of Milicia resulting from gall formation had taken place equally on all seedlings, but survival of seedlings at the forest site was 40% higher than at the agricultural site.
Vertical dispersal of the two‐spotted spider mite Tetranychus urticae, and the predatory mite Phytoseiulus persimilis on dwarf hops
Authors: Lilley R. , Campbell C. A. M. , Ridout M. S. 
Published: March 2003

Summary1 The pattern of dispersion within plants of the two‐spotted spider mite, Tetranychus urticae, and its predator, the phytoseiid Phytoseiulus persimilis, was studied on the dwarf hop variety First Gold from May to September in 1997 and 1998.2 Spider mite populations developed on the lower leaves initially but, by late July, as the numbers of mites increased, most were found towards the top of plants. From early August, the numbers of spider mites decreased most rapidly on the upper parts of plants.3 Where P. persimilis was released, the predator maintained the numbers of T. urticae below those found on non‐release plots throughout the season.4 By early August, the predator’s pattern of dispersion was similar to that of the pest.5 Predators spread to non‐release plots by 20 June in 1997 and 24 July in 1998 and eventually became more numerous than on the plots where they had been released.
Life cycle and biological control of the Eucalyptus snout beetle (Coleoptera, Curculionidae) by Anaphes nitens (Hymenoptera, Mymaridae) in north‐west Spain
Authors: Rivera Adolfo Cordero , Carbone Serena Santolamazza , Andrés José A. 
Published: March 2003

Summary1 Gonipterus scutellatus is a weevil that has become a pest in most Eucalyptus plantations in Africa, America and Europe. The egg parasitoid Anaphes nitens has been introduced into many countries as a biological control agent. Even if control has been successful in most countries no detailed study of the interactions between both species has been published.2 Gonipterus scutellatus was detected in 1991 in north‐west Spain and A. nitens was introduced in early 1994. Here we report on the results of a 2‐year study of parasitism in a field plot and a survey of 16 localities in North‐west Spain. In 1996, parasitism was so intense (80–100% of eggs) that G. scutellatus became locally extinct, and as a consequence A. nitens disappeared. In 1997, G. scutellatus recolonized the area and was followed by its parasitoid, but parasitism was low in spring, probably because the parasitoid population needed 3 weeks to achieve a similar size as in 1996. Consequently, damage to the trees was extreme in 1997. We interpret these results as population fluctuations due to parasitoid–host interactions and suggest that parasitoids should not to be so effective as to locally extinguish their host to be useful for biological control.3 The analysis of parasitism level in 16 localities indicates that A. nitens is highly efficient in finding G. scutellatus egg‐masses. At a small spatial scale (single trees) positive density dependence was detected where parasitism was low and inverse density dependence where parasitism was high.
Suitability of the biomass crop Miscanthus sinensis as a host for the aphids Rhopalosiphum padi (L.) and Rhopalosiphum maidis (F.), and its susceptibility to the plant luteovirus Barley Yellow Dwarf Virus
Authors: Huggett D. A. J. , Leather S. R. , Walters K. F. A. 
Published: March 2003

Summary1 The reproductive performance of two aphid pest species, Rhopalosiphum padi and Rhopalosiphum maidis, was investigated on two seedling growth stages of Miscanthus sinensis, rhizomatous M. sinensis‘Giganteus’ and barley. Rhopalosiphum padi was unable to complete its development on Miscanthus. Rhopalosiphum maidis was most fecund on rhizomatous plants compared with seedling stages.2 The ability of R. maidis to transmit the RPV isolate of Barley Yellow Dwarf Virus (BYDV) to M. sinensis seedlings was further investigated. Following successful transmission, host plant symptomology and the effect of infection on the yield of Miscanthus were investigated. Total above soil biomass was reduced by around 23% following infection.3 The inability of R. padi to utilize Miscanthus is reviewed in light of this species’ origin and inability to utilize C4 host plants.4 The potential pest status of R. maidis on Miscanthus is discussed together with the impact that Miscanthus cultivation could have on the ecology of this aphid species and BYDV in the U.K.
Genetic differentiation of the green spruce aphid (Elatobium abietinum Walker), a recent invader to Iceland
Authors: Sigurdsson V. , Halldórsson G. , Sigurgeirsson A. , Thórsson Æ. TH. , Anamthawat‐Jónsson K. 
Published: March 2003

Abstract1 The RAPD method (Random Amplified Polymorphic DNA) was used to investigate genetic diversity of the green spruce aphid, Elatobium abietinum Walker, a pest introduced recently to Iceland.2 This aphid in Iceland comprised two polymorphic populations, one in the east and the other in the west of the country. The genetic variation between sites within a population was continuous and appeared to be in good agreement with geographical distances.3 In the eastern population the variation was greater between sites than within sites, whereas in the western population the pattern of variation appeared to be the opposite. This overall greater genetic variation in the eastern population could be due to its having been colonized earlier than the western one.4 The study also demonstrated a close relationship between the green spruce aphid in Iceland and aphids from Denmark, which agrees with their assumed origin. The differences in introduction time, adaptation and competitiveness between the two Icelandic populations are discussed.
Performance of the fir coneworm Dioryctria abietivorella (Grote) as affected by host species and presence or absence of seed cones
Authors: Trudel Richard , Bauce Éric , Guertin Claude , Cabana Jean 
Published: March 2003

Abstract1 Larval performance of Dioryctria abietivorella (Grote) (Lepidoptera: Pyralidae) was compared when insects were reared in white spruce, black spruce and Jack pine seed orchards. For each species, half of the insects developed in the presence of cones, while the other half was maintained on branches without cones.2 Significantly faster development rates were observed on spruce species when compared to Jack pine. Significant differences in survival were also recorded between the different feeding treatments.3 The presence of seed cones on spruce species significantly increased insect mean weight compared with branches without cones, but no significant differences were noticed between the different tree species with cones.4 White spruce is the most suitable host tree for fir coneworm feeding and the availability of seed cones plays an important role in determining D. abietivorella larval performance.
Seasonal patterns of egg parasitism and natural biological control of rice brown planthopper in Indonesia
Authors: Claridge M. F. , Morgan J. C. , Steenkiste A. E. , Iman M. , Damayanti D. 
Published: March 2003

Summary1 Egg mortality is known to be an important factor in brown planthopper (BPH) (Nilaparvata lugens) population dynamics in tropical Asia, but few quantitative data are available on the role of egg parasitoids.2 Field studies are reported at two sites in Java, Indonesia, over a period of 4 years in both wet and dry seasons, where no chemical pesticides were used. Rice plants previously infested in the laboratory with BPH eggs were exposed to natural parasitism and predation in experimental fields for periods of 5 days.3 Egg batches were dissected from both experimental and control plants after field exposure at seven fortnightly intervals through the rice growing season and BPH nymphs and adult parasitoids were allowed to emerge.4 Parasitism by species of Oligosita (Hymenopera, Trichogrammatidae) and Anagrus (Hym., Mymaridae) varied between 18% and 61% in dry, and from 1% to 65% in wet, seasons. There was generally a trend from low to higher rates through wet seasons, contrasting with more uniform higher levels through dry seasons.5 Reduction in BPH survival as a result of egg parasitism varied between 29% and 91%. Generally parasitism was density independent.6 It is suggested that lower initial levels of parasitism in dry seasons may be due to the longer fallow period between dry and wet, than between wet and dry, resulting in lower local populations of appropriate natural enemies.7 Unlike previous studies in Asia, little evidence was found for egg predation as an important mortality factor.8 The conservation of egg parasitoids should form part of any rice pest management programmes in tropical Asia.
Spatial dispersion and sampling of citrus whitefly, Dialeurodes citri, for control decisions in a citrus orchard
Authors: Argov Yael , Rössler Yoram , Voet Hillary , Rosen David 
Published: March 2003

Summary1 Monitoring the citrus whitefly Dialeurodes citri (Ashmead) in citrus orchards in Israel is necessary for control decisions in IPM in the period before the establishment of natural enemies. The main damage caused by D. citri is due to sooty mould, which colonizes the sweet secretions of this pest.2 Using Taylor’s Power Law to describe the variance–mean relationship, the dispersion of the citrus whitefly was found to be aggregated at all developmental stages. The action threshold was estimated using regression of sooty mould level on egg or larval counts.3 Two‐stage sampling plans were constructed in different pest generations, for eggs and larval stages, on the basis of the variance between leaves on a tree and the variance between trees in a plot.4 Fixed sample size plans were prepared, with possible numbers of trees and the numbers of leaves per tree to be sampled, in order to attain a given precision level.5 Sequential sampling plans were also drawn up, on the basis of four leaves per tree, where trees are sampled until a decision can be reached. The maximum number of trees to be sampled was set according to the corresponding fixed sample size plan.6 Simulation of the sequential sampling plans showed them to be highly reliable in terms of the decision reached with economy in sample size for high and low infestation levels.
Resistant cabbage cultivars change the susceptibility of Plutella xylostella to Bacillus thuringiensis
Authors: Schuler Tanja H. , Van Emden H. F. 
Published: March 2003

Summary1 Laboratory studies demonstrated that the susceptibility of larvae of the lepidopteran crucifer pest Plutella xylostella to the insect pathogen Bacillus thuringiensis (Bt) was influenced by the host plant.2 Larvae reared on the resistant cabbage cultivars Minicole F1 and Red Drumhead were significantly more susceptible to Bt (the LC50 fell to one half) than larvae fed leaves of susceptible cultivars.3 However, a third resistant cultivar, Aquarius F1, had no synergistic effect on Bt‐related mortality.4 Actual uptake of Bt was monitored in the bioassays, as a preliminary experiment showed that the plant resistance reduced consumption of Bt‐treated leaf discs. However, differences in feeding rate did not explain the observed differences in mortality.
Modelling Beauveria bassiana horizontal transmission
Authors: Long David W. , Drummond Francis A. , Groden Eleanor , Donahue Darrell W. 
Published: March 2003

Summary1 We modelled horizontal transmission of Beauveria bassiana in Colorado potato beetle (CPB) between larval cadavers and soil inhabiting prepupae.2 The rate of disease transmission, based on the probability of a prepupa contacting sporulating cadavers on the soil surface, is a non‐linear function of cadaver density and also dependent upon temperature.3 The spatial pattern of cadavers is needed to estimate prepupal contacts with cadavers. Observational field studies determined Johnson distributions to model the spatial pattern of cadavers and prepupae in the field. The model also implicitly incorporates within‐field larval spatial pattern into estimates of field‐level horizontal transmission.4 Potential for horizontal transmission is higher in simulations using weather data from the warmer year of 1995, than in simulations of the cooler growing season of 1993.5 Simulations of CPB populations under northern Maine climatic conditions recorded in 1993 and 1995 suggest that horizontal transmission can range from 3 to 24% depending upon the timing of primary infection of larvae in the field.6 Two simulated sequential applications of B. bassiana targeted at peak first instars resulted in maximum horizontal infection in both years.7 Sensitivity analysis suggests that horizontal transmission is most sensitive to changes in the proportion of cadavers that sporulate and least sensitive to changes in the time between larval death and the onset of cadaver sporulation.8 Field validation of the model indicates good prediction of one measure of horizontal infection, the proportion of prepupae which eventually sporulated after being released in controlled field experiments.
First use of pheromones to detect phenology patterns and density relationships of pine sawflies in German forests
Authors: Herz Annette , Heitland Werner , Anderbrant Olle , Edlund Helén , Hedenström Erik 
Published: March 2003

Abstract1 Monitoring studies of pine sawflies with pheromone traps were performed for the first time in Germany. Pheromone traps baited with species‐specific pheromone substances were installed in pine forests at different locations in Bavaria, Brandenburg and Lower Saxony during two years.2 It was possible to track the flight phenology of Diprion pini, Gilpinia pallida and Neodiprion sertifer reliably and to get information about the number of generations of these species in 1997 and 1998.3 A clear relationship between trap catch and population density could not be detected, but qualitative changes in trap catch caused by different density levels were observed.4 For D. pini, trap catches were different among endemic populations of different forest types. Furthermore, catches of males reflected the results from the regular cocoon collections by foresters during the previous winter.5 For N. sertifer, trap catches in endemic populations were well separated from trap catches on sites with higher sawfly densities. However, no significant correlation between trap catch and sawfly density or defoliation level could be found. These results suggest that the efficacy of the pheromone traps probably varied with biological features (sex ratio, density level, immigration) of the particular population.
Insecticide resistance in populations of Tuta absoluta (Lepidoptera: Gelechiidae)
Authors: Siqueira Herbert Álvaro A. , Guedes Raul Narciso C. , Picanço Marcelo C. 
Published: March 2003

Abstract1 Control failures of insecticides used against the tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in Brazil led to the investigation of the possible occurrence of resistance of this insect pest to abamectin, cartap, methamidophos and permethrin.2 The insect populations were collected from seven sites in the states of Minas Gerais, Rio de Janeiro, and São Paulo. These populations were subjected to concentration–mortality bioassays using insecticide‐impregnated filter papers.3 We were unable to obtain a single population which provided a susceptibility standard for all insecticides tested. Therefore, the resistance levels were estimated in relation to the most susceptible population to each insecticide. Resistance to abamectin and cartap were observed in all populations when compared with the susceptible standard population, with resistance ratios ranging from 5.2‐ to 9.4‐fold and from 2.2‐ to 21.9‐fold for abamectin and cartap, respectively. Resistance to permethrin was observed in five populations with resistance ratios ranging from 1.9‐ to 6.6‐fold, whereas resistance to methamidophos was observed in four populations with resistance ratios ranging from 2.6‐ to 4.2‐fold.4 The long period and high frequency of use of these insecticides against this insect pest suggest that the evolution of insecticide resistance on them has been relatively slow. Alternatively, the phenomenon might be widespread among Brazilian populations of T. absoluta making the finding of suitable standard susceptible populations difficult and leading to an underestimation of the insecticide resistance levels in this pest.5 Higher levels of resistance to abamectin, cartap and permethrin are correlated with greater use of these compounds by growers. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.
A critique of silvicultural approaches to managing defoliating insects in North America
Authors: Muzika R. M. , Liebhold A. M. 
Published: March 2003

Abstract1 A variety of silvicultural techniques have been suggested for managing forest defoliating insects. The objectives focus on minimizing defoliation or minimizing damage from defoliation.2 The theoretical foundations of many approaches have been built upon observation and correlation, and very little reliable empirical evidence exists to support the objectives of silvicultural manipulations. Existing experimental data have yielded inconsistent results.3 We review the conceptual framework and underlying assumptions of the major silvicultural approaches recommended or in use in North America.4 Well‐designed, long‐term studies are needed to clarify the effect of silviculture on defoliators and their effect on forests.