bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential for biological control of native competing vegetation using native herbivores
Authors: Valenti Michael A. , Berryman Alan A. , Ferrell George T.
Published: March 2003

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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

1 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.
The effect of drought stress and temperature on spread of barley yellow dwarf virus (BYDV)
Authors: Smyrnioudis I. N. , Harrington R. , Katis N. , Clark S. J.
Published: March 2003

1 The effect of drought stress and temperature on the dispersal of wingless aphids Rhopalosiphum padi (L.) and the pattern of spread of BYDV (barley yellow dwarf virus) within wheat plants in controlled environment chambers was quantified. Combinations of three different drought stress levels, unstressed, moderate and high stress level, and three different temperatures, 5 ± 1 °C, 10 ± 1 °C, and 15 ± 1 °C, were investigated.

2 With increased temperature there was an increase in the mean distance of visited plants from the point of release and in the number of plants visited and infected with BYDV. Drought stress had no effect on mean distance moved by aphids at any temperature or on plants infected with virus at 10 °C and 5 °C. When plants were drought stressed, the numbers of plants visited and infected were greater at 15 °C than at 10 °C and 5 °C.

3 A greater proportion of plants visited by aphids was infected with BYDV when plants were stressed than when not stressed. At 15 °C a greater proportion of these plants was infected than at lower temperatures. There was no difference between treatments in the numbers of aphids present at the end of the experiment.

4 It is concluded that drought stress and temperature are of considerable importance in virus spread.
Orientation of Colorado potato beetle to natural and synthetic blends of volatiles emitted by potato plants
Authors: Dickens Joseph C.
Published: March 2003

1 Behavioural responses of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), to volatiles emitted from solanaceous host plants (potato and tomato), a non‐host legume (soybean), and 13 synthetic blends or three individual chemicals emitted by potato plants were investigated in laboratory bioassays.

2 Both male and female CPB were attracted to volatiles emitted by mechanically damaged potato foliage, but not to mechanically damaged tomato foliage; CPB offered a choice between the two damaged solanaceous plants did not show a preference.

3 Among 16 odourous blends or individual chemical components of potato plant emissions tested, six blends were attractive, two were repellent, and eight elicited no preference in laboratory bioassays. Volatile blends containing relatively high amounts of the green leaf volatiles (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol, or the sesquiterpene β‐ caryophyllene, were unattractive or repellent. Minimal blends attractive to CPB were comprised of (Z)‐3‐hexenyl acetate (±)‐linalool and methyl salicylate: the combination of all three chemicals elicited sexually dimorphic attraction of males; two component blends comprised of (Z)‐3‐hexenyl acetate and either (±)‐linalool and methyl salicylate attracted both sexes. Individual compounds were inactive. No significant difference was noted between two attractive blends, or an attractive synthetic blend vs. mechanically damaged potato foliage.

4 These results show that CPB are attracted to blends of specific chemicals emitted by their host plants and provide a basis for the use of plant attractants as a component of integrated management of pestiferous populations.
Effectiveness of gypsy moth mating disruption from aerial applications of plastic laminate flakes with and without a sticking agent
Authors: Thorpe K. W. , Leonard D. S. , Mastro V. C. , McLane W. , Reardon R. C. , Sellers P. , Webb R. E. , Talley S. E.
Published: March 2003

1 The plastic laminate flake formulation, Disparlure II, is currently the only gypsy moth mating disruption product available for aerial application. The elimination of a sticking agent from the formulation would reduce costs, simplify application, and make it possible to apply the product without specialized equipment.

2 A test was conducted in wooded plots in Virginia during 1997 and 1998 to determine whether a sticking agent is necessary. Treatment effectiveness was assessed from the rates of male moth capture in pheromone‐baited traps and mating success of both laboratory‐reared and wild females.

3 Male moth capture was reduced 75.6 and 92.9% in plots treated with flakes without and with a sticking agent, respectively. The percentage of mated females that produced egg masses with more than 5% fertile eggs was reduced by 86.3 and 99.5% in plots treated with flakes without and with a sticking agent, respectively.

4 Moth capture and mating success of laboratory‐reared females did not differ significantly between plots treated with flakes with and without a sticking agent. However, the consistently greater reduction in mating success in both years provides strong evidence that mating disruption is less effective when flakes are applied without a sticking agent. The proportion of wild egg masses collected in 1998 with more than 5% fertile eggs was significantly higher under the no‐sticking agent treatment.

5 In special situations where the use of a sticking agent may be problematic, such as in residential areas, the data indicate that a high level of mating disruption is likely to occur even without the use of a sticking agent.
Seasonal synchrony of life cycles between the exotic predator, Pseudoscymnus tsugae (Coleoptera: Coccinellidae) and its prey, the hemlock woolly adelgid Adelges tsugae (Homoptera:Adelgidae)
Authors: Cheah Carole A. S. ‐J. , McClure Mark S.
Published: March 2003

1 The seasonal synchrony between the exotic predator, Pseudoscymnus tsugae and its prey, the hemlock woolly adelgid, Adelges tsugae, was investigated in field cages and in the forest in Connecticut, U.S.A. from 1997–1999.

2 In early spring, egg to adult development took 45 d at 18.7 °C, 39.7 d at 20.2 °C and 31.5 d at 22.7 °C. Earliest emerging F1 adults mated and oviposited in the same year. whereas F1 and F2 females emerging later in the summer mated and reserved most of their egg complement for the following year.

3 A second generation of P. tsugae is possible in Connecticut but may be delayed by cool mid‐spring temperatures. Individuals of three generations of P. tsugae, including overwintering survivors, may coexist in July and August and adults can be found year‐round with A. tsugae in infested hemlock forests.

4 A linear regression model for development from egg to adult under field temperatures gave good agreement with results from constant temperature findings. The model predicted a lower development threshold of 9.5 °C and a sum of effective temperatures of 405 day °C. Development time of P. tsugae is shorter relative to its prey A. tsugae and generation time ratios of predator to prey was 0.16–0.5, with an advantage conferred on the coccinellid.

5 Overwintering ability and behaviour were determined in 1998–1999 and adults remained on infested hemlock branches throughout a mild winter, becoming reproductively active in mid‐April. Peak oviposition period extended from April to July, in synchrony with peak oviposition and developing stages of two generations of A. tsugae.
Insect growth‐reducing and antifeedant activity in Eastern North America hardwood species and bioassay‐guided isolation of active principles from Prunus serotina
Authors: Omar S. , Lalonde M. , Marcotte M. , Cook M. , Proulx J. , Goel K. , Durst T. , Philogène B. J. R. , Arnason J. T.
Published: March 2003

1 Thirty extracts of wood and bark of hardwood trees from Eastern North America were examined for insect growth‐reducing activity in a bioassay with European corn borer, Ostrinia nubilalis, and an antifeedant bioassay with the rice weevil, Sitophilus oryzae.

2 Nine of the bark extracts and four of the wood extracts showed significant growth reducing effects at 0.5% in meridic diets, whereas only two bark extracts and one wood extract showed significant antifeedant effect at the same concentration.

3 Slower growing tree species were more biologically active than fast growing ones. Isolation of the bioactive compounds in one of the active species, Prunus serotina, showed that naringenin, its derivative methoxynaringenin, and eriodictyol were responsible for the antifeedant effects.
Recapture of Ips typographus L. (Col., Scolytidae) with attractants of low release rates: localized dispersion and environmental influences
Authors: Franklin Anne J. , Debruyne Catherine , Grégoire Jean‐Claude
Published: March 2003

1 The dispersal of Ips typographus L. (Col., Scolytidae) was studied using a mark–release–recapture approach in a grid of traps equipped with pheromone lures of release rates of about 8.4 mg/day of 2‐methyl‐3‐buten‐2‐ol (MB) and 0.29 mg/day of (S)‐cis‐verbenol (cV) in experiment 1, and 1.2 mg/day of MB and 0.04 mg/day of cV in experiment 2.

2 We investigated whether beetle dispersal reflected the simple diffusion pattern observed in previous I. typographus experiments, for which attractant release rates generally approached 50 mg/day of MB and 1 mg/day of cV. We also examined how environmental parameters (wind) and human activities (felling) could influence the beetles' flight.

3 The recapture percentage was higher in experiment 1 than in experiment 2: respectively, 7.0% (with 64 traps) and 2.3% (with 100 traps) of the beetles that took off were caught in the traps.

4 With the higher release rate (experiment 1), trap catches decreased with increased distance, whereas with the lower release rate (experiment 2), trap catches rose between 50 and 100 m then decreased with increasing distance.

5 Flight was little orientated by prevailing wind directions, a feature probably explained by the low wind speeds (0–1.2 m/s) observed throughout the study.

6 High trap catches of unmarked beetles close to areas undergoing thinning activities suggest that the presence of freshly cut spruce and larch material could have an influence on dispersal, attracting the beetles into the felling area. Spatial analyses show that capture patterns were autocorrelated up to distances of about 250 m.
Arthropod diversity of exotic vs. native Robinia species in northern Arizona
Authors: Degomez Tom , Wagner Michael R.
Published: March 2003

1 Arthropods were collected on native locust, Robinia neomexicana A. Gray, and exotic Robinia pseudoacacia L. in northern Arizona over a 2‐year period to determine the number of arthropod species and number of individuals present.

2 More arthropod species were found on the native (251) than on the exotic Robinia (174).

3 Greater species diversity was likewise found on the native than the exotic. The five most numerous insects collected each year accounted for 81% to 91% of the total number collected on the exotic and native Robinia in 1997 and 1998. Only 12 species occurred on both the native and exotic Robinia in both years.

4 These findings are discussed in the context of using exotic trees in plantations and ecological theory regarding rates of arthropod species accumulation on exotic hosts.
Plant quality vs. risk of parasitism: within‐plant distribution and performance of the corn leaf aphid, Rhopalosiphum maidis
Authors: Gonzáles Wilfredo L. , Gianoli Ernesto , Niemeyer Hermann M.
Published: March 2003

1 Colonies of the aphid Rhopalosiphum maidis on Johnsongrass, Sorghum halepense, usually occur inside the whorl. The present work assessed the role of two biotic factors, plant quality and parasitism by Lysiphlebus testaceipes, in determining within‐plant distribution and performance of R. maidis. The mean relative growth rate of aphids inside the whorl and on a mature leaf was compared, and the concentration of hydroxamic acids in those tissues determined as an indicator of plant quality. Parasitism effectiveness and parasitoid behaviour were evaluated using three treatments: aphid colonies placed (1) wholly inside the whorl, (2) on the inner and outer surfaces of the whorl, and (3) on a mature leaf.

2 The mean relative growth rate of aphids was lower on the whorl than on the mature leaf, and hydroxamic acid concentration in the whorl was higher than in the mature leaf.

3 The number of parasitized dead aphids (mummies) inside the whorl was considerably lower than in the other two treatments. Mummies were present in 80% of the replicates in the whorl, whereas mummies were present in all replicates of the other treatments.

4 Host location time of the parasitoid was increased on the mature leaf compared with the other treatments. No significant differences in the residence time of the parasitoid in the aphid colony occurred between treatments.

5 Host location time showed a negative correlation, and residence time of the parasitoid a positive correlation with the number of aphids on the outer surface of the whorl.
Pheromone‐mediated mass trapping and population diversion as strategies for suppressing Carpophilus spp. (Coleoptera: Nitidulidae) in Australian stone fruit orchards
Authors: James David G. , Vogele Beverley , Faulder Richard J. , Bartelt Robert J. , Moore Christopher J.
Published: March 2003

1 Five experiments were conducted during 1995–99 in stone fruit orchards on the Central Coast and in inland New South Wales, Australia, on the use of synthetic aggregation pheromones and a coattractant to suppress populations of the ripening fruit pests Carpophilus spp. (Coleoptera: Nitidulidae).

2 Perimeter‐based suppression traps baited with pheromone and coattractant placed at 3 m intervals around small fruit blocks, caught large numbers of Carpophilus spp. Very small populations of Carpophilus spp. occurred within blocks, and fruit damage was minimal.

3 Carpophilus spp. populations in stone fruit blocks 15–370 m from suppression traps were also small and non‐damaging, indicating a large zone of pheromone attractivity.

4 Pheromone/coattractant‐baited suppression traps appeared to divert Carpophilus spp. from nearby (130 m) ripening stone fruit. Ten metal drums containing decomposing fruit, baited with pheromone and treated with insecticide, attracted Carpophilus spp. and appeared to reduce populations and damage to ripening fruit at distances of 200–500 m. Populations and damage were significantly greater within 200 m of the drums and may have been caused by ineffective poisoning or poor quality/overcrowding of fruit resources in the drums.

5 Suppression of Carpophilus spp. populations using synthetic aggregation pheromones and a coattractant appears to be a realistic management option in stone fruit orchards. Pheromone‐mediated diversion of beetle populations from ripening fruit may be more practical than perimeter trapping, but more research is needed on the effective range of Carpophilus pheromones and the relative merits of trapping compared to attraction to insecticide‐treated areas.
Disruption of sexual communication in the mirid bug Lygocoris pabulinus by hexyl butanoate
Authors: Groot Astrid T. , Drijfhout Falko P. , Heijboer Anneke , Van Beek Teris A. , Visser J. Hans
Published: March 2003

1 The metathoracic scent gland in Lygocoris pabulinus contains mostly hexyl butanoate. As secretions of this gland in Heteroptera may serve as an alarm pheromone, we determined whether hexyl butanoate is released by disturbed bugs, and whether this compound disrupts sexual attraction of L. pabulinus males towards females.

2 Undisturbed males and females, and disturbed males released less than 100 ng/h hexyl butanoate, whereas disturbed females released a highly variable amount, ranging from 25 ng/h to more than 1 μg/h.

3 In the field, traps with virgin females and rubber septa containing 20 mg hexyl butanoate, caught a total of one male in a month. In control traps without hexyl butanoate, 36 males were caught in the same period.

4 In Y‐track olfactometer tests, males were not attracted to virgin females when a dispenser with 20 mg hexyl butanoate was placed in the bottle with females. Males were attracted to females when the dispenser was placed downwind from the females, but upwind from the point of male release.

5 These results suggest that males are not repelled by hexyl butanoate, but that this compound inhibits sex pheromone release in females. Application possibilities for pest management are discussed.
Distribution and abundance of aphidophagous hoverflies (Diptera: Syrphidae) in wildflower patches and field margin habitats
Authors: Sutherland Jamie P. , Sullivan Matthew S. , Poppy Guy M.
Published: March 2003

1 The spatial and temporal variations in aphidophagous syrphid abundance were recorded over two seasons in wildflower resource patches sown in a winter barley crop and associated field margins. Standard census techniques and sticky board trapping were used to assess numbers of syrphids, whilst weekly flower head counts were used to quantify the floral resources available in each of the patches.

2 The field margin supported a greater diversity and density of syrphids than the within‐crop wildflower patches, despite having a relatively lower flower head density. Presumably this was in response to other resources that field margins offer, namely additional aphid resources, shelter from predation, lekking sites and suitable flight‐paths.

3 The commonest species of syrphid, Episyrphus balteatus, demonstrated a very positive habitat association with the field margin and was rarely reported in the field patches. Therefore, it may be an unsuitable candidate for the biological control of aphids via augmentation of numbers using non‐host resources.

4 Patch size and shape had little effect on the spatial distributions of syrphids, probably because of the adult syrphids' high mobility.

5 Of greater influence was the number of flowers contained in each habitat patch. Typically, patches with higher numbers of flowers had significantly greater aggregations of hoverflies. Habitat manipulation by the provision of flowers in patches seems to increase the local density of hoverflies. Further work is necessary to establish the importance of flower density in enhancing the control of pest populations.
Influence of crop edges on movement of generalist predators: a diffusion approach
Authors: Bommarco Riccardo , Fagan William F.
Published: March 2003

1 Diffusion models were applied to recapture data for the generalist predator Pterostichus cupreus (Coleoptera: Carabidae) moving between two adjacent crop habitats (perennial ley and annual barley) first excluding, and then including, terms in the model quantifying the influences of edges on beetle movements.

2 Adult beetles were released at the centre of experimental 3 × 3 m plots that overlapped the edge separating perennial ley (mixed perennial crop of grass and clover) and annual barley crops, both early and later in the growing season.

3 Mathematical description of the data improved when the attractive or repulsive effects of habitat edges on dispersal were considered in the model.

4 Early in the season, when a sharp habitat edge was present, P. cupreus beetles appeared ‘attracted’ to ley.

5 Diffusion rates were consistently higher in barley than in ley early in the season, and vice versa late in the season. These patterns were probably linked to variation in prey availability.

6 Despite the risk of experiencing food limitation in the annual crop, our analyses suggest that these beetles regularly move from ley into the early barley habitat and then continue to disperse within the barley, providing opportunities for enhanced biological control of pest species.
A field experiment on the effectiveness of spiders and carabid beetles as biocontrol agents in soybean
Authors: Vichitbandha Patchanee , Wise David H.
Published: March 2003

1 Spiders and carabid beetles are abundant generalist predators that prey upon insect pests of soybean. A field experiment was conducted to determine the impact of spiders and carabids on soybean yield. Prior to planting, three 7 × 7 m plots were fenced in order to reduce spider and carabid immigration. Carabids that emerged within the plots were not removed, but spiders that ballooned into these predator‐reduction plots or that entered by climbing the fence were removed by pitfall trapping and searching the vegetation. Three unmanipulated, unfenced plots served as the control treatment.

2 Densities of spiders on soybean vegetation, and activity‐densities of spiders and carabids determined by pitfall trapping, were c. 75% lower in the spider‐carabid reduction treatment than in control plots. Despite clear differences between treatments in numbers and activity of these major generalist predators, the weight of soybeans harvested did not differ between control and spider‐carabid reduction plots.

3 Paralleling the absence of an effect of predator reduction on soybean yield was the absence of any significant difference between treatments in densities of whiteflies (Aleyrodidae), leafhoppers (Cicadellidae), thrips (Thysanoptera), Lepidoptera larvae and herbivorous Coleoptera.

4 Our experiment provides no evidence that spiders and carabid beetles at ambient densities affect soybean yield. Low populations of pest species or low predation pressure on soybean pests by spiders and carabids at the ambient densities of this experiment could be responsible for this result.
Climate change and the outbreak ranges of two North American bark beetles
Authors: Williams David W. , Liebhold Andrew M.
Published: March 2003

Abstract

 One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. Southern pine beetleDendroctonus frontalisand mountain pine beetleDendroctonus ponderosaeundergo regional outbreaks that result in large‐scale disturbances to pine forests in the south‐eastern and western United States, respectively.

 Our objective was to investigate potential range shifts under climate change of outbreak areas for both bark beetle species and the areas of occurrence of the forest types susceptible to them.

 To project range changes, we used discriminant function models that incorporated climatic variables. Models to project bark beetle ranges employed changed forest distributions as well as changes in climatic variables.

 Projected outbreak areas for southern pine beetle increased with higher temperatures and generally shifted northward, as did the distributions of the southern pine forests.

 Projected outbreak areas for mountain pine beetle decreased with increasing temperature and shifted toward higher elevation. That trend was mirrored in the projected distributions of pine forests in the region of the western U.S. encompassed by the study.

 Projected outbreak areas for the two bark beetle species and the area of occurrence of western pine forests increased with more precipitation and decreased with less precipitation, whereas the area of occurrence of southern pine forests decreased slightly with increasing precipitation.

 Predicted shifts of outbreak ranges for both bark beetle species followed general expectations for the effects of global climate change and reflected the underlying long‐term distributional shifts of their host forests.
Lepidopteran pest populations and crop yields in row intercropped broccoli
Authors: Hooks Cerruti R. R. , Johnson Marshall W.
Published: March 2003

Abstract

To determine how the presence of non‐host plants impact populations of lepidopteran pests and yield of broccoli, Brassica oleracea var. italica L., broccoli was intercropped with tomato, Lycopersicon esculentum Miller, or yellow sweetclover (YSC), Melilotus officinalis L., and compared with broccoli monoculture grown at two densities (high and low).

During a 1997 study, numbers of early instar imported cabbageworm, Artogeia rapae L., were greater in broccoli monoculture compared with intercropped plantings. In contrast, late instar A. rapae numbers were significantly higher in intercropped broccoli during most of the season, indicating greater survival of early instar stages in intercropped habitats.

Cabbage looper, Trichoplusia ni Hübner, eggs and larvae were more abundant in broccoli monoculture than intercropped broccoli in 1997. In addition, T. ni populations were found at significantly lower levels in broccoli‐YSC compared with broccoli‐tomato habitat throughout the season.

During a 1998 study, numbers of early and late A. rapae instars were greater in intercropped broccoli on most sampling dates.

The mean percentages of harvested broccoli heads infested with insects and associated frass were higher in monocultures than intercropped treatments in 1997. Additionally, a significantly lower number of contaminants were found in the crowns of broccoli harvested from broccoli‐YSC (YSC) compared with broccoli‐tomato (tomato) habitat. However, broccoli heads were significantly smaller in intercropped habitats.

Variations in insect responses and challenges to using crop diversification as a management tool are discussed.
Selective toxicity of some pesticides to Pullus mediterraneus Fabr. (Coleoptera: Coccinellidae), a predator of Saissetia oleae Bern. (Homoptera: Coccoideae)
Authors: Ba M'hamed T. , Chemseddine M.
Published: March 2003

To contribute to the development of IPM strategies in olive groves, the selectivity of several insecticides to Pullus mediterraneus Fabr. (Coleoptera: coccinellidae) was investigated in the laboratory. The study assessed the toxicity of seven chemical pesticides and one bacteriological insecticide to adult P. mediterraneus.

The LC50 was estimated by applying the pesticides on the dorsal side of adults. Lambda‐cyhalothrin, methomyl and cypermethrin resulted in the highest toxicity followed, in decreasing order of toxicity, by malathion, fenthion and dimethoate. Parathion had the least effect on the coccinellid.

Consumption of Bacillus thuringiensis bacteria (applied as a commercial formulation), over a period of 10 consecutive days, resulted in low mortality of adult P. mediterraneus.

The results of these laboratory experiments indicate that the most widely used chemical pesticides were toxic to P. mediterraneus. Their use in olive groves must take account of the activity period of this predator. In contrast, B. thuringiensis seemed to be a suitable candidate to be included in pest management systems.
Insecticidal activity of Piper tuberculatum Jacq. extracts: synergistic interaction of piperamides
Authors: Scott I. M. , Puniani E. , Durst T. , Phelps D. , Merali S. , Assabgui R. A. , Sánchez‐Vindas P. , Poveda L. , Philogène B. J. R. , Arnason J. T.
Published: March 2003

Abstract

 The insecticidal activity of the neotropical pepper Piper tuberculatum Jacq. and its isolated piperamides was studied. Bioassays with the mosquito Aedes atropalpus L. assessed the relative toxicity of the whole extract of Piper tuberculatum and four of the piperamides, which were isolated and identified, then prepared synthetically.

 The results confirm that P. tuberculatum leaf extracts are as effective as black pepper seed extract and provide an alternative pepper insecticide from a more convenient source, the leaves.

 Experiments with piperamides showed that the tertiary and quaternary mixtures have greater‐than‐additive toxicity compared to single compounds or binary mixtures. One of the four amide compounds, 4,5‐dihydropiperlonguminine, was the most acutely toxic in mosquito larvae bioassays.

 A study of piperamide levels from different P. tuberculatum populations in Costa Rica determined that they were relatively homogeneous. Piper tuberculatum from only one of the five sites had higher levels of one piperamide, 4,5‐dihydropiperine, in both leaf and stem parts. One explanation for differences in the amide concentrations between populations is that one site is ecologically unique compared to the other four.
Sex pheromone of apple fruit moth Argyresthia conjugella (Lepidoptera: Argyresthiidae)
Authors: Jaastad Gunnhild , Bengtsson Marie , Anderson Peter , Kobro Sverre , Knudsen Geir , Witzgall Peter
Published: March 2003

The apple fruit moth Argyresthia conjugella Zell. (Lepidoptera: Argyresthiidae) is the most important pest of apple in Scandinavia. It invades apple orchards and can destroy an entire crop during years of poor flowering and fruitsetting of its principal host, mountain ash Sorbus aucuparia. We investigated the female sex pheromone of apple fruit moth in order to develop a reliable lure, which can be used to detect migration of apple fruit moth into orchards and thus to avoid preventive insecticide sprays.

 Pheromonal compounds obtained by solvent extraction of excised A. conjugella female pheromone glands were identified by coupled gas chromatography/electroantennography and gas chromatography/mass spectrometry. Two compounds (Z)‐11‐hexadecenyl acetate, and the analogous alcohol (Z)‐11‐hexadecen‐1‐ol, elicited a strong response from male antennae. (Z)‐11‐hexadecenyl acetate was highly attractive in field trapping tests, whereas as little as a 1%‐addition of (Z)‐11‐hexadecen‐1‐ol strongly reduced male attraction.

 (Z)‐13‐octadecenyl acetate, a previously reported sex attractant, had no effect on A. conjugella male attraction.