Showing papers in "Agricultural and Forest Entomology in 2006"

Interactions among fire, insects and pathogens in coniferous forests of the interior western United States and Canada

Abstract: Natural and recurring disturbances caused by fire, native forest insects and path- ogens have interacted for millennia to create and maintain forests dominated by seral or pioneering species of conifers in the interior regions of the western United States and Canada. 2 Changes in fire suppression and other factors in the last century have altered the species composition and increased the density of trees in many western forests, leading to concomitant changes in how these three disturbance agents interact. 3 Two- and three-way interactions are reviewed that involve fire, insects and path- ogens in these forests, including fire-induced pathogen infection and insect attack, the effects of tree mortality from insects and diseases on fuel accumulation, and efforts to model these interactions. 4 The emerging concern is highlighted regarding how the amount and distribution of bark beetle-caused tree mortality will be affected by large-scale restoration of these fire-adapted forest ecosystems via prescribed fire. 5 The effects of fire on soil insects and pathogens, and on biodiversity of ground- dwelling arthropods, are examined. 6 The effects of fire suppression on forest susceptibility to insects and pathogens, are discussed, as is the use of prescribed fire to control forest pests.

The effects of floral understoreys on parasitism of leafrollers (Lepidoptera: Tortricidae) on apples in New Zealand

Abstract: Field and laboratory experiments on the conservation biocontrol of lepidop- teran leafroller pests were carried out in apples at Lincoln, New Zealand. 2 Apple understoreys were planted with replicated treatments of alyssum (Lobularia maritima), phacelia (Phacelia tanacetifolia) and buckwheat (Fagopyrum esculentum). 3 Rates of parasitism of experimentally released larvae of the light-brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), by Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) were signifi- cantly lower in phacelia and control treatments, and leafroller pupae were significantly more abundant in controls than in buckwheat and alyssum treatments. 4 Naturally occurring leafroller damage was up to 29% lower above all the floral understorey treatments compared with controls and there were more than twice as many D. tasmanica cocoons in the alyssum and buckwheat treatments than in controls. 5 Suction sampling of the understoreys gave D. tasmanica adult densities that were significantly more abundant in alyssum compared with other treatments. Numbers of Anacharis zealandica (Hymenoptera: Figitidae) (a parasitoid of larvae of the predatory brown lacewing) did not differ between treatments. 6 In the laboratory, flowering buckwheat and alyssum enhanced D. tasmanica longevity by up to 78% compared with the control, and buckwheat also enhanced potential fecundity by 62%. 7 In choice experiments, leafroller larvae in the laboratory consumed more than three-fold more apple leaf material than they did of the three understorey species, although alyssum increased leafroller fecundity and longevity. 8 The use of floral understoreys for conservation biocontrol of apple pests is discussed, along with the potential negative effects of some flowering species on pest populations and orchard agronomic practices.

Expression of Bacillus thuringiensis Cry1Ac protein in cotton plants, acquisition by pests and predators: a tritrophic analysis

Abstract: Studies have shown that Cry proteins of the bacterium Bacillus thuringiensis expressed in transgenic plants can be acquired by nontarget herbivores and preda- tors. A series of studies under field and controlled conditions was conducted to investigate the extent to which Cry1Ac protein from Bt transgenic cotton reaches the third trophic level and to measure the amount of protein that herbivores can acquire and expose to predators. 2 Levels of Cry1Ac in Bt cotton leaves decreased over the season. Among herbi- vores (four species), Cry1Ac was detected in lepidopteran larvae and the amount varied between species. Among predators (seven species), Cry1Ac was detected in Podisus maculiventris and Chrysoperla rufilabris . 3 In the greenhouse, only 14% of the Cry1Ac detected in the prey ( Spodoptera exigua larvae) was subsequently found in the predator P. maculiventris. Detection of Cry1Ac protein in Orius insidiosus , Geocoris punctipes and Nabis roseipennis was probably limited by the amount of prey consumed that had fed on Bt cotton. 4 Purified Cry1Ac was acquired by the small predatory bug G. punctipes but at much higher concentration than found in plants or in lepidopteran larvae. 5 Bt protein was shown to move through prey to the third trophic level. Predatory heteropterans acquired Cry1Ac from prey fed Bt cotton, but acquisition was dependent on the concentration of Cry1Ac conveyed by the prey and the amount of prey consumed. The type and availability of prey capable of acquiring the protein, coupled with the generalist feeding behaviour of the most common predators in the cotton ecosystem, probably constrain the flow of Cry1Ac through trophic levels.

Insecticidal activity of garlic juice in two dipteran pests

Abstract: 1 Botanical products excluding pyrethroids constitute a small, but growing portion of the U.K. pesticides market. With increasing legislative pressure upon chemical pesticides such as organophosphates, interest in this sector is increasing steadily. 2 Garlic Allium sativum L. juices and extracts form the basis of several commercially available pest control products, but the performance of these products is variable, possibly due to lack of quality control upon batches of materials in the manufacturing process. 3 Some garlic products designed for use in the food industry are subjected to rigorous batch-control to ensure organoleptic consistency. We studied the insecticidal efficacy of a commercially produced food grade garlic juice using two target dipteran pests, Delia radicum (L.) and Musca domestica L. 4 Exposure of the two species to different concentrations of garlic juice revealed variability in insecticidal effect across life stages. LC50 values recorded for D. radicum were: eggs (7-day exposure) 0.8%; larvae (24-h exposure) 26.4%; larvae (48-h exposure) 6.8%; and adults (24-h exposure) 0.4%. LC50 values recorded for M. domestica were: eggs (7-day exposure) 1.6%; larvae (24-h exposure) 10.1%; larvae (24-h exposure) 4.5%; and adults (24-h exposure) 2.2%. 5 Mortality rates caused by the garlic juice were comparable with those obtained with the organophosphate pesticide Birlane®, indicating parity of effect at various concentrations depending on life stage. 6 We conclude that this product may provide an effective, naturally-derived insecticide for use in agricultural systems against dipteran pests.

Arthropods within the woody element of hedgerows and their distribution pattern

Abstract: 1 The diversity and abundance of arthropods within hedgerows was investigated using insecticide fogging. In total, 13 390 arthropods were collected from 181 m3 of hedge (2% of the total volume). The taxonomic diversity of the total sample included 51 families in 13 orders, all within the phylum Arthropoda. Five orders accounted for 90% of all arthropods: Araneae, Coleoptera, Diptera, Hemiptera and Hymenoptera. The predators were the dominant functional group accounting for 40% of the total sample. 2 The linear distribution of hedgerow arthropod assemblages was investigated by sampling arthropods in 13 hedges at seven equidistant points along each hedge. Abundance of most arthropod taxa and the four functional groups (predators, parasitoids, herbivores and scavengers) consistently showed a clumped distribution along hedges, with high numbers at both ends and in the middle section. Hedge ends were defined either as a node, where the hedge intersected with another hedge, or as a gateway prior to an adjacent landscape feature such as a wood. Aggregation of arthropods at the nodes may reflect preferable microclimatic conditions at hedgerow junctions, whereas aggregation at a gap suggests the gap acted as a barrier to movement. The aggregation at the centre remains unexplained but may be a manifestation of the movement of individual arthropods along the hedgerow. 3 The great abundance and diversity of arthropods found in the present study emphasizes the status of hedges as one of the most important noncrop habitats on farmland. The arthropods that they contain may act as food for other farmland species, aid pest control and contribute to crop pollination.

Verbenone-releasing flakes protect individual Pinus contorta trees from attack by Dendroctonus ponderosae and Dendroctonus valens (Coleoptera: Curculionidae, Scolytinae)

Abstract: In a study site in interior northern California, twenty individual lodgepole pines Pinus contorta were sprayed with a suspension of DISRUPT Micro-Flake ® Verbenone (4,6,6-trimethylbicyclo(3.1)hept-3-en-2-one) Bark Beetle Anti- Aggregant flakes (Hercon Environmental, Emigsville, Pennsylvania) in water, with sticker and thickener, from ground level to a height of 7 m. Twenty trees sprayed with just water, sticker and thickener served as controls. All trees were baited immediately after spraying with mountain pine beetle Dendroctonus ponde- rosae aggregation pheromone lures, and lures were refreshed after 4 weeks. 2 Trees treated with verbenone had significantly lower attack density by D. ponde- rosae than controls at 2, 4, 6 and 8 weeks after application of flakes. 3 None of the treated trees was attacked by red turpentine beetle Dendroctonus valens , whereas control trees averaged nearly two D. valens attacks per tree, 8 weeks after treatment. 4 A dry frass index, used to predict ultimate tree mortality, was significantly higher in control trees than treated trees for all four sampling intervals. This index proved to be a significant predictor of ultimate tree mortality. 5 Ten months after application, treated trees showed significantly lower mortality than control trees.

Patterns in the within‐tree distribution of the emerald ash borer Agrilus planipennis (Fairmaire) in young, green‐ash plantations of south‐western Ontario, Canada

Abstract: 1 The emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a serious exotic pest of ash trees (Fraxinus spp.) in North America, and is responsible for the deaths of millions of trees in Ontario and Michigan. One of the greatest challenges facing the successful management of the pest is the ability to accurately detect its presence in a tree. 2 Observations were made on A. planipennis larval feeding galleries found within 65 young, green-ash trees cut from plantations in Essex County, Ontario, Canada. The within-tree distributions of feeding galleries were described in relation to height-above-ground, stem diameter, bark thickness and stem aspect. 3 Galleries were not distributed randomly or evenly; minimum boundaries of stem diameter and bark thickness and a maximum boundary of height-above-ground were detected. Indications of maximum boundaries for stem diameter and bark thickness were also observed. Galleries were found most often on the south-west side of the tree. 4 Using the technique of upper boundary regression, we were able to identify significant quadratic relationships between A. planipennis gallery density and stem diameter and bark thickness, as well as a significant negative linear relationship between gallery density and height-above-ground. 5 Agrilus planipennis gallery density in newly-infested trees was lower than in previously-infested trees, and was observed to peak at smaller stem diameters and bark thicknesses than in previously-infested trees. 6 Survey teams would increase their probability of detecting new A. planipennis infestations by initiating searches for exit holes and feeding galleries in trunk sections and branches of approximately 7 cm in diameter.

Effects of reduced pesticide dosages on carabids (Coleoptera: Carabidae) in winter wheat

Abstract: 1 The effects of reduced insecticide and herbicide dosages on total dry mass of carabids and their generic components were examined using fenced pitfall traps in winter wheat fields on three farms in Southern Zealand, Denmark. 2 The estimated total dry mass of carabids increased by 25% when the pesticides were reduced to one fourth of the normal application rates. 3 At reduced dosages, the activity of the genus Pterostichus was increased by 62%. The activities of Loricera and Demetrias were increased by 67% and 56%, respectively, although significant interaction terms indicated that the dosage effect was not uniform for these genera on all farms. Calathus tended to be more numerous with reduced pesticide applications. By contrast, catches of Bembidion, Synuchus and Trechus decreased by up to 45% at reduced dosages. 4 A higher weed cover due to reduced herbicide applications probably benefited most species, except those having habitat associations with sparse vegetation such as the field-inhabiting Bembidion and Synuchus. 5 The higher activity of larger carabids may lead to enhanced predation on smaller carabids and hence different carabid assemblages.

Recruitment of native parasitoids by an exotic leaf miner, Cameraria ohridella: host-parasitoid synchronization and influence of the environment

Abstract: 1The horse-chestnut leaf miner, Cameraria ohridella, is a moth of unknown origin that has recently invaded Europe and severely defoliates the European horse-chestnut, an important ornamental tree. 2Several indigenous parasitoids have colonized this new host, but parasitism remains low. One of the hypotheses suggested to explain the low parasitism is that candidate parasitoids emerge too early in spring to attack the first host generation and, thus, need early-occurring leaf miners as alternate hosts. This hypothesis was tested by observing the synchronization between the phenology of the moth and that of its main parasitoids, and by comparing parasitism rates and parasitoid richness in different environments with various levels of biological diversity. 3In spring, the bulk of the parasitoids emerge at least 5 weeks before the occurrence of the first suitable larvae of C. ohridella whereas most parasitoid adults reared outdoors die within 5 weeks after emergence. 4Parasitism rates and parasitoid richness do not increase with biological diversity, suggesting that most parasitoids attacking the first generation of C. ohridella do not come from alternate hosts. Parasitism does not increase later in the year in the subsequent generations, when host-parasitoid synchronization becomes less critical. 5We conclude that, although the spring emergence of parasitoids is not synchronized with the phenology of C. ohridella, the parasitoids attacking the first generation are probably old or late-emerging adults of the overwintering generation. The lack of synchronization is probably not the only reason for the poor recruitment of native parasitoids by C. ohridella.

Attack preference of Ips pini on Pinus ponderosa in northern Arizona: tree size and bole position

Abstract: 1 The present study investigated the influence of tree size and bole position on selection of ponderosa pines (Pinus ponderosa Dougl. ex Laws.) by Ips pini Say (Coleoptera: Curculionidae: Scolytinae) in a northern Arizona forest. Ips pini were attracted to lower and upper bole positions with pheromone lures, and the number of attacks counted. In addition, tree phloem and bark thickness, resin flow in response to wounding and characteristics of tree water and carbon relations were all measured. 2 Bark thickness was the most strongly related tree characteristic to number of I. pini attacks. Thin bark and a high number of attacks occurred at the lower bole position of 10-cm diameter trees and upper bole positions of 23-, 35-, and 50-cm diameter trees. 3 Phloem thickness increased directly with tree size, was greater at the upper bole compared with the lower bole, but was not associated with number of attacks. 4 Resin flow did not differ strongly over tree sizes or bole positions, and was not related to number of I. pini attacks. Attacks were not related to characteristics of tree carbon and water relations measured during I. pini flights.

Effects of delayed mating on reproductive output of female oriental beetle Anomala orientalis (Coleoptera: Scarabaeidae)

Abstract: 1 Although management of the oriental beetle Anomala orientalis (Waterhouse) by mating disruption shows promise across a range of agricultural systems, relatively little is known about aspects of the reproductive biology of this species relevant to its management. We studied the effects of delayed mating on several aspects of the oviposition behaviour and biology of the oriental beetle using females mated in the laboratory at 4–13 days posteclosion. 2 Females exhibited a gradual decline in fecundity with increased age at mating that was largely a function of a decline in duration of the oviposition period, as well as lower female fertility: females mated at 11 days were less likely to lay any fertile eggs. However, egg fertility did not vary with female age at mating. 3 Because mating delay did not affect longevity, females mated at older ages experienced decreased oviposition periods; however, females laid more eggs per day with increased age at mating, which partially offset shorter oviposition periods. 4 A mating delay of ≥ 6 days relative to females mated within the first day of reaching sexual maturity resulted in an approximately 35–50% lower mean fecundity. 5 These results suggest that, for mating disruption to be a successful management tool for the oriental beetle, mating must be prevented rather than delayed. We compare the findings of the present study with the published research on delayed mating in moths and discuss the importance of these results in relation to management of the oriental beetle using female sex pheromones.

Feeding on roots in the humus layer by adult pine weevil, Hylobius abietis

Abstract: 1 The consumption by adult pine weevil, Hylobius abietis, of the bark of roots present in the humus layer was assessed in a field study conducted in southern Sweden during two years (1998 and 2002). The study sites were divided into two areas: (i) a shelterwood where 80–100 mature Scots pine trees per hectare remained after cutting and (ii) a clearcut where no trees were left. 2 On average, 3741 m2 per hectare of root bark was present in the humus layer, of which 135 m2 was not coniferous but comprised species such as bilberry and broadleaved trees. 3 The mean area debarked by pine weevils was 2.9 m2 per hectare; 2.6 m2 of conifer roots and 0.3 m2 of bilberry roots. Roots of broadleaved trees were almost never consumed. No clear preferences for roots of a specific level of vitality were observed. 4 No consistent difference between the shelterwood and clearcut was found, either in the amount of root bark area available or in the extent of root feeding by pine weevil. 5 A weak negative correlation between debarked areas on roots and seedlings was found, indicating that root feeding may have reduced damage to seedlings. 6 It is concluded that conifer roots in the humus layer constitute a major food source for the pine weevil and can be utilized for a considerable period in both clearcuts and shelterwoods.

Distribution and population genetic structure of the Mediterranean pine shoot beetle Tomicus destruens in the Iberian Peninsula and Southern France

Abstract: 1 The Mediterranean pine shoot beetle Tomicus destruens has long been indistinguishable from its congeneric Tomicus piniperda. Both species attack pines, and can be found in sympatry. The geographical distribution of T. destruens is still unclear in most of the Mediterranean Basin. 2 We aimed to describe the geographical distribution and zones of sympatry of both species in the Iberian Peninsula and France, and to study the molecular phylogeographical pattern of T. destruens. 3 Tomicus spp. adults were sampled in Portugal, Spain and France, and a portion of the mitochondrial genes COI and COII was sequenced for 84 individuals. Sequences were aligned to a data set previously obtained from French localities. 4 Tomicus destruens was found in all populations, except for one locality in Portugal and in the Landes (France). It was in sympatry with T. piniperda in two locations on Pinus pinaster and one location on Pinus radiata. 5 Within-population genetic diversity was high, but we found a significant pattern of spatial distribution of genetic variation, as well as a significant effect of the host tree. 6 The data suggest the existence of two glacial refugia, from which T. destruens recolonized its current range. One refugium was located in Portugal where the beetle probably evolved on P. pinaster. The corresponding haplotypes show a West–East frequency gradient. The other refugium was probably in the eastern range, where the beetles evolved on Pinus halepensis and P. pinea. The corresponding haplotypes show an East–West frequency gradient.

Factors affecting willow leaf beetles (Phratora vulgatissima) when selecting overwintering sites

Abstract: Leaf beetles are major pests in willow plantations used as short-rotation coppice for biomass production. The beetles overwinter mainly outside the plantations. An understanding of the factors affecting adult leaf beetles seeking overwintering sites may provide information that could be valuable when developing methods to control the beetles. 2 We conducted a field experiment in a willow plantation with a high abundance of the leaf beetle, Phratora vulgatissima. We positioned overwintering con- structions (OWCs) made out of bundles of reed (Phragmites australis) outside the plantation. 3 Leaf beetles preferred (i) to fly towards silhouettes; (ii) OWCs positioned 1.5 m above the ground compared with ones 0.5 m above the ground; (iii) OWCs orientated vertically compared with OWCs orientated horizontally; and (iv) reeds of a diameter of approximately 5 mm. 4 Leaf beetle size was not correlated with reed diameter. 5 It is concluded that the leaf beetle P. vulgatissima selects an overwintering site based on factors at both larger and smaller scales. The possibilities for using OWCs made of reed bundles as tools to monitor and control are discussed.

Adult large pine weevils Hylobius abietis feed on silver birch Betula pendula even in the presence of conifer seedlings

Abstract: 1 The feeding preference of the adult pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) for Betula pendula Roth was studied in no-choice and paired-choice feeding experiments. 2 In the first no-choice test, large quantities of silver birch bark in Petri dishes were consumed; on average, the daily consumption of each weevil was 67 mm2. 3 In the second no-choice test, the weevils were offered 1-year-old silver birch seedlings for 6 days. Initially, the weevils fed mostly on the stem bases; later, they moved upward to feed on other parts of the stems. In addition to the main shoots, scars caused by gnawing were also found on leaf bases, blades, veins and petioles. Feeding resulted in the death of the main stems in 15% of the seedlings. 4 In the paired-choice tests, the conifers were preferred to silver birch, even though a large amount of silver birch was also consumed in the presence of conifers. 5 In the paired-choice tests, equal amounts of Scots pine and Norway spruce were always consumed. When hybrid aspen was offered, only small amounts were gnawed.

Potential of a synthetic aggregation pheromone for integrated pest management of Colorado potato beetle

Abstract: The relative number of colonizing adult Colorado potato beetles (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) coming to pitfall traps baited with the aggregation pheromone (S)-3,7-dimethyl-2-oxo-oct-6- ene-1,3-diol ((S)-CPB I) and the use of the pheromone in a trap crop pest management strategy were evaluated in the field for the first time. 2 More than five-fold more adult L. decemlineata were caught in pitfall traps baited with the pheromone compared with controls. However, attraction to the pheromone diminished after 5 days in the field. 3 In the trap crop management strategy, more colonizing adults were present in pheromone-treated rows of potatoes compared with untreated middle rows. 4 Significantly fewer L. decemlineata egg masses and larvae were found in potato plots that were bordered by pheromone-treated rows, or bordered by imida- cloprid þ pheromone-treated rows, or rows treated at-planting with imidaclo- prid compared with untreated (control) potato plots. 5 Densities of L. decemlineata egg masses and larvae and percentage defoliation were significantly lower, and marketable tuber yield significantly higher, in conventional imidacloprid-treated potatoes compared with all other treatments. 6 Although our results demonstrate the potential for use of the aggregation pheromone in the management of L. decemlineata in the field, more research is needed to optimize the release rates of the attractant and incorporate control methods for cohabiting pests.

Phenology of Eucalyptus weevil, Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), and chrysomelid beetles in Eucalyptus globulus plantations in south-western Australia.

Abstract: 1 In south-western Australia, Eucalyptus globulus plantations are defoliated by a complex of beetle species, yet only scant information exists on these species under such climatic conditions. To improve management of these defoliating beetles in the region, canopy fogging and shoot clipping were conducted in plantations between 1999 and 2002 to identify and document the phenology of the beetle species present. 2 Eucalyptus weevil, Gonipterus scutellatus, was the most common and destructive defoliating beetle. Gonipterus scutellatus undergoes one principal generation each year with a lesser second generation or cohort in some seasons, which contrasts greatly with reports of two to four annual generations for the species in other regions. This limited reproduction by G. scutellatus may be due to the limited availability from summer onwards of new flushing foliage, which is essential for feeding and oviposition. 3 Several species of chrysomelid beetles were collected in plantations, but these were present in much lower numbers than G. scutellatus and were only a minor concern. However, some species, such as Chrysophtharta variicollis, appear to be capable of developing short-lived outbreaks. 4 A diverse suite of natural enemies was fogged from plantations but they were significantly less abundant than defoliating beetles and are not likely to provide significant control of beetles. 5 In terms of managing these defoliating beetles, monitoring and control should focus on G. scutellatus, and be conducted during spring when most damage occurs.

Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae) in south-western Virginia

Abstract: Competitive interactions among two specialist predators, Laricobius nigrinus and Sasajiscymnus (Pseudoscymnus) tsugae , and a generalist predator, Harmonia axyridis Pallas, of hemlock woolly adelgid, Adelges tsugae were evaluated in hemlock stands in south-western Virginia. The two specialist predators are part of a biological control program for A. tsugae , and the potential for competition among these species and previously established generalist predators in the field is unknown. 2 Adult predators were evaluated in branch cages during spring and summer at two field sites infested with A. tsugae . Using females only in 2003 and sexual pairs in 2004, predator survival and net reproduction were examined, as well as their feeding and impact on A. tsugae when present alone and in conspecific and heterospecific groupings. 3 Predator survival was not affected by the presence of additional predators. Total feeding was greater for all species when placed in predator groupings, suggesting that interactions do not significantly interfere with feeding activity. Net reproduc- tion per predator was negatively affected by conspecifics, but unaffected by het- erospecifics, indicating that direct or indirect intraspecific interference may occur. In spring, L. nigrinus showed the greatest impact on A. tsugae , and H. axyridis had the greatest impact during summer. 4 These results suggest that it would be beneficial to utilize multiple predator species combinations over single species when implementing biological control for A. tsugae . Low-density releases are also recommended to reduce intraspecific interference.

A migration analysis of Sogatella furcifera (Horváth) (Homoptera: Delphacidae) using hourly catches and a three-dimensional simulation model.

Abstract: 1 Migrations of Sogatella furcifera captured in Japan in the 2003 season were analysed using hourly catches and a simulation model. 2 The catch data showed several clear migration peaks, with average durations of 4 h. The peaks were separated from each other by approximately 12 h, corresponding to the observed fact that planthoppers take off at dusk or dawn. 3 The simulation model comprised two components: a numerical weather forecast submodel, MM5, and a particle dispersion submodel, GEARN. The simulation model used three-dimensional meteorological data and calculated the relative aerial density of migrating planthoppers to allow analysis of the timing and area of migrations in Japan. 4 The simulation model, together with the hourly catches, enabled an estimation of migration source regions. 5 Possible migration sources during our hourly observation period were located in the coastal area of Fujian province in China, as well as Taiwan.

Fecundity, longevity and establishment of Otiorhynchus sulcatus (Fabricius) and Otiorhynchus ovatus (Linnaeus) (Coleoptera: Curculionidae) from the Pacific North‐west of the United States of America on selected host plants

Abstract: 1 The fecundity, longevity and establishment of Otiorhynchus sulcatus and Otiorhynchus ovatus from the Pacific North-west U.S.A. was studied on five selected host plants: Picea abies‘Nidiformis’, Picea glauca‘Conica’, Taxus baccata, Rhododendron catawbiense‘Boursault’ and Fragaria×ananassa‘Totem’. 2 Teneral adults were used to study adult longevity and reproductive success. Leaves of these host plants were used for sustenance for 9 months. Larval establishment was studied by infesting potted host plants with eggs. 3 Fragaria×ananassa‘Totem’ produced the longest survival, shortest preoviposition time, the greatest number of eggs, and the highest fertility for adults of both species. Picea spp. were not good adult hosts for O. sulcatus. Taxus was a good adult host for O. sulcatus, but was a nonhost for adults and larvae of O. ovatus. 4 Adult hosts did not affect preoviposition time or egg viability with O. ovatus adults. With O. sulcatus, preoviposition time was greatly increased and egg viability was < 50% on Picea spp. 5 The best larval host was F.×ananassa‘Totem’ for O. sulcatus and P. glauca‘Conica’ for O. ovatus. Rhododendron was a poor larval host for both species. 6 When all of the studies on these two pests are considered, O. sulcatus appears to have varying host preferences from among its many geographical areas of occurrence whereas O. ovatus has a more universal host selection.

Migration, trapping and local dynamics of whiteflies (Homoptera: Aleyrodidae)

Abstract: 1 The ability to quantify whitefly migration provides a tool that can contribute to an improved understanding of the epidemic development of whitefly-transmitted viruses. 2 In an attempt to develop a protocol for estimating whitefly immigration and emigration rates in an annual crop, new traps and sampling devices were tested in the field and models for population dynamics were developed. 3 An estimate of immigration rate was derived from the growth of a natural population of Trialeurodes vaporariorum (Westwood) in the beginning of a crop cycle before offspring of immigrants contributed to population growth. 4 A model for changes in whitefly density during an entire bean (Phaseolus vulgaris L.) crop cycle, including an immigration parameter, was also developed. 5 Non-attractant window traps surrounding an annual field crop were assumed to intercept whiteflies immigrating into and emigrating away from the crop. Captures on these traps could not categorically be identified as immigrants or emigrants, but the cumulated captures nevertheless explained 66% of the variation in population density found within the field. Hence, window traps may be used as an efficient and reliable alternative to yellow sticky traps, aspirator methods and leaf-turn methods, etc., for estimating whitefly densities in field crops.

Models for spring migration of two aphid species Sitobion avenae (F.) and Rhopalosiphum padi (L.) infesting cereals in areas where they are entirely holocyclic

Abstract: 1 Cereals can be attacked severely by the grain aphid, Sitobion avenae (F.), and the bird cherry-oat aphid, Rhopalosiphum padi (L.). The time of migration from winter hosts in spring is important regarding input to decision support systems concerning insecticide treatment of aphids. 2 The present study aimed to construct two separate migration models, which could be used immediately for advisors and farmers but also be part of a decision support system for the chemical control of aphids in winter wheat and spring barley. 3 Winter wheat (Triticum sativum Lam.) and spring barley (Hordeum vulgare L.) fields were monitored from 1991–2005 for the occurrence of grain aphids and bird cherry-oat aphids, and the data were used to construct migration models. 4 The models were constructed based on all 9 years data and subsequently validated by using all 9 years data, excluding 1 year at a time. 5 The migration model for the grain aphid producing the best forecast was obtained with migration date M (number of days from 1 June), degree-days (DD) of April (Ta) and DD of May (Tm), with the model being M= 265.0 − 10.2 loge(Ta) − 35.1 loge(Tm). 6 The migration model for the bird cherry-oat aphid producing the best forecast was obtained with migration date M (number of days from 15 May), DD of April (Ta) and DD from 1–15 May (Tm1), with the model being M= 294.4 − 34.7 loge(Ta) − 22.5 loge(Tm1). 7 The models only worked well in areas where the grain aphid and the bird cherry-oat aphid are entirely holocyclic.

Synthetic amides toxic to the leaf-cutting ant Atta sexdens rubropilosa L. and its symbiotic fungus

Abstract: 1 Nine synthetic amides similar to natural N-piperidine-3-(4,5-methylenedioxyphenyl)-2-(E)-propenamide and N-pyrrolidine-3-(4,5-methylenedyoxiphenyl)-2-(E)-propenamide were synthesized and identified by their spectroscopic data. 2 The toxicity of these synthetic amides to the Atta sexdens rubropilosa workers and the antifungal activity against Leucoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, were determined. 3 Workers ants that were fed daily on an artificial diet to which these compounds were added had a higher mortality rate than the controls for N-pyrrolidine-3-(3′,4′-methylenedioxyphenyl)-2-(E)-propenamide and N-benzyl-3-(3′,4′-methylenedioxyphenyl)-2-(E)-propenamide at a concentration of 100 µg/mL. 4 The completely inhibition (100%) of the fungal growth was observed with N-piperidine-3-(3′,4′-methylenedioxyphenyl)-2-(E)-propenamide and N,N-diethyl-3-(3′,4′-methylenedioxyphenyl)-2-(E)-propenamide at concentrations of 50 and 100 µg/mL and N-pirrolidine-3-(3′,4′-methylenedioxyphenyl)-2-(E)-propenamide at a concentration of 100 µg/mL. 5 The possibility of controlling these insects in the future using synthetic piperamides that can simultaneously target both organisms is discussed.

Seasonal changes in the distribution of green spruce aphid Elatobium abietinum (Walker) (Homoptera: Aphididae) in the canopy of Sitka spruce

Abstract: 1 Seasonal changes in the distribution of green spruce aphid Elatobium abietinum (Walker) within the canopy of 20–25-year-old Sitka spruce are described based on data from two low-altitude sites (310–420 m above sea-level), two mid-altitude sites (500–550 m a.s.l) and one high-altitude site (610 m a.s.l). 2 Aphids were counted throughout the canopy on shoots representative of all needle age-classes present at each whorl of branches. Counts were made during the middle week of each month from September to July for 4 years (1999–2003), and mean E. abietinum densities at each canopy position were calculated separately for each month and for the low-, mid- and high-altitude sites. 3 During September to November, the highest densities of E. abietinum occurred on 3–4-year-old needles on branches low in the canopy. Over the winter and spring, the centre of the aphid’s distribution shifted outward and upward, so that by June of the next year the highest aphid densities occurred on current and 1-year-old needles on branches near the top of the tree. 4 The aphid distribution was re-set each year during July, at the time when the nutrient quality of the host was in decline and E. abietinum populations were decreasing. Aphid densities decreased less on 3–4-year-old needles than on current and 1-year-old needles, suggesting that older needles were a superior food resource at this time of year and in the autumn. However, other factors, such as higher temperatures in the upper canopy during the summer or differential mortality caused by natural enemies, could also have contributed to the change in distribution. 5 The outward and upward shift in the aphid distribution over the winter period provided no evidence that aphids at positions lower and deeper in the canopy were better insulated from freezing temperatures and had higher over-winter survival rates. Mean air temperatures at the top and bottom of the canopy during the winter were also found to differ by only 0.1–0.2 °C. 6 The percentage of the total aphids per tree that occurred on current or 1-year-old needles varied widely between seasons and between sites. Consequently, sampling programmes designed to estimate total population numbers of E. abietinum have little option but to sample needles throughout the canopy, and at regular intervals during the period when the aphid is abundant.

Analysis of population genetic structure of two closely related tortricid species of economic importance on macadamias and litchis in South Africa

Abstract: 1 The macadamia nut borer Thaumatotibia (Cryptophlebia) batrachopa and the litchi moth Cryptophlebia peltastica are Afrotropical species causing extensive damage to cultivated macadamias and litchis in the northernmost provinces in South Africa. Cryptophlebia peltastica also occurs as natural populations throughout the country. 2 To analyse the population genetic structure of the two species, amplified fragment length polymorphism analysis was conducted. Patterns of genetic diversity in C. peltastica populations in the Mpumalanga province, where the species is controlled, were compared with those in the Western Cape, where populations occur under natural conditions. 3 Gene diversity was high within T. batrachopa populations (H = 0.2219) with significant genetic differentiation among populations (Gst = 0.358). Cluster analysis showed that geographical populations were closely related and extensive divergence was found over local scales. 4 Similar to that of T. batrachopa, genetic diversity and population differentiation was high within both C. peltastica Mpumalanga and Western Cape populations (H = 0.1906 and 0.1687 and Gst = 0.4124 and 0.3799, respectively). 5 It is suggested that the population genetic structure of both species is influenced by their limited ability to disperse. In addition, chemical control of C. peltastica in the Mpumalanga province has not succeeded in reducing the population size, but the C. peltastica population subdivision in the Western Cape may be influenced by the limited distribution of host plants in this region.

Monitoring the European pine sawfly with pheromone traps in maturing Scots pine stands

Abstract: 1 During 1989-93, field studies were conducted in Finland to develop a method based on pheromone traps to monitor and forecast population levels of the European pine sawfly (Neodiprion sertifer Geoffr.) and tree defoliation. 2 Three traps per site were baited with 100 mu g of the N. sertifer sex pheromone, the acetate ester of (2S,3S,7S)-3,7-dimethyl-2-pentadecanol (diprionol), in maturing pine stands in southern and central Finland. In addition, three different dosages (1, 10 and 100 mu g) of the pheromone were tested in 1991-92. 3 The highest number of males was observed in traps baited with the highest dose. On average, there was a 10-fold increase in trap catch between lure doses. 4 Density of overwintering eggs was used to evaluate the effectiveness of pheromone traps in predicting sawfly populations. The proportion of healthy overwintering eggs was determined each year. A model based on the number of current shoots on sample trees, diameter at breast height and tree height was formulated to estimate eggs per hectare. 5 Linear regression analysis produced high coefficients of determination between number of males in traps and density of total eggs in the subsequent generation, when populations were at peak densities. The relationships were not significant for low population densities. The results indicate a risk of model-ate defoliation when the seasonal trap catch is 800-1000 males per trap or higher. (Less)

Responses of ovipositing moths to host plant deprivation: life history aspects and implications for intercropping

Abstract: 1. When considering intercropping as a strategy to reduce pest oviposition, knowledge about the insect’s oviposition behaviour is very important. Physiological effects on the insect because of difficulties in finding a suitable oviposition site may also be important. 2. In the present study, the effects that delays in access to host plants have on lifetime fecundity on diamondback moth and leek moth were examined. The ability to postpone egg laying, fecundity and lifetime oviposition are discussed in relation to intercrop/cover crop as a strategy to reduce oviposition on crop plants. 3. When faced with host plant deprivation, the diamondback moth is relatively more dependent upon host plant stimuli for the onset of egg production. By contrast, leek moth is able to postpone egg production for a longer time. There even appeared to be a tendency for leek moth females to extend their lifetime when faced with host plant deprivation. 4. We conclude that leek moths have the ability to postpone production of eggs and lay them later in life when finally encountering host plants after a period of host plant deprivation. Therefore, the use of intercropping as a strategy to reduce oviposition is questionable. For such an insect, use of a trap crop might be a better option because the female will lay her eggs in the trap crop and not get the opportunity to lay them later in life when finally encountering crop plants.

Species status and population structure of the Australian Eucalyptus pest Paropsis atomaria Olivier (Coleoptera: Chrysomelidae)

Abstract: 1 Paropsis atomaria Olivier represents an emergent pest of Eucalyptus plantations in Queensland and New South Wales, Australia. Most prior studies on the biology and control of P. atomaria have centred on populations from Canberra in the Australian Capital Territory, but the biological relationship between beetles from Canberra and those from up to 1500 km further north are unknown. 2 DNA markers were used to determine whether P. atomaria from Canberra are the same biological species as those from Eucalyptus forestry plantations in northern New South Wales and Queensland, where the beetle has become an important pest. Using the mitochondrial gene, cytochrome c oxidase I (COI), individuals collected from across the distribution of P. atomaria were investigated for haplotype diversity and levels of mitochondrial divergence. 3 Within P. atomaria, genetic distance averaged 0.5% across 23 unique haplotypes for 93 individuals, with an average of 14% difference between P. atomaria and the outgroup species, Paropsis obsoleta. Significant genetic structure was observed relative to geographical distribution, but not with respect to host plant species of origin. Greatest divergence was between the southern-most sample site (Canberra) and northern sites in New South Wales and Queensland, indicating reduced gene flow between these regions. 4 Individuals from across eastern Australia belong to the same genetic species with population substructuring evident. Consequently, there is no evidence to suggest cryptic species complexes exist within the currently defined taxon. Continued implementation of control strategies for P. atomaria across its distribution is appropriate.

An assessment of re‐randomization methods in bark beetle (Scolytidae) trapping bioassays

Abstract: 1 Numerous studies have explored the role of semiochemicals in the behaviour of bark beetles (Scolytidae). 2 Multiple-funnel traps are often used to elucidate these behavioural responses. Sufficient sample sizes are obtained by using large numbers of traps to which treatments are randomly assigned once, or by frequent collection of trap catches and subsequent re-randomization of treatments. 3 Recently, there has been some debate about the potential for trap contamination to occur when semiochemical treatments (baits), and not trap-treatment units (traps and baits), are re-randomized among existing traps. Due to the volatility of many semiochemicals, small levels of contamination could potentially confound results. 4 A literature survey was conducted to determine the frequency of re-randomizing semiochemical treatments (baits) vs. trap-treatment units (traps and baits) in scolytid trapping bioassays. An experiment was then conducted to determine whether differences in the response of Dendroctonus brevicomis LeConte to attractant-baited traps exist between the two methods. 5 The majority of papers examined reported use of a large number of fixed replicates (traps) rather than re-randomization of treatments at frequent intervals. Seventy-five percent of papers for which re-randomization methods could be determined reported relocation of semiochemical treatments (baits) only. 6 No significant differences in trap catch were observed among multiple-funnel traps aged with D. brevcomis baits (Phero Tech Inc., Canada) for 0, 30 and 90 days, suggesting that contamination did not influence the results. 7 It is concluded that re-randomizing baits is a viable cost-effective option to re-randomizing trap and bait units.

Sequential patterns of colonization of coarse woody debris by Ips pini (Say) (Coleoptera: Scolytidae) following a major ice storm in Ontario

Abstract: 1 It is widely known that many bark and wood-boring beetle species use nonresistant coarse woody debris (CWD) created by disturbances; however, the ability of these secondary species to cause mortality in healthy trees following a build-up of their populations remains unclear. We characterized the pattern of colonization by Ips pini (Say) following a major ice storm that created large amounts of CWD varying in resistance to colonization (i.e. ranging from snapped tops with no resistance to heavily damaged trees with intact root systems). A major question was how the beetles responded to the different types of storm-damaged material and whether healthy undamaged trees were colonized and killed following increases in beetle populations. 2 Six red pine, Pinus resinosa Ait., plantations in eastern Ontario were monitored from 1998 to 2001 inclusive: three with high storm damage (approximately 120 m3/ha CWD) and three with minimal damage (approximately 20 m3/ha CWD). Transects (200 × 2 m) were sampled yearly in each plantation to assess the type and amount of damaged pine brood material colonized by the pine engraver beetle, I. pini. 3 Beetles preferentially infested the most nonresistant material available each year (i.e. all snapped tops in year 1, all standing snags, up-rooted trees and many bent trees by year 2, but still less than 50% of trees blown over but with intact root systems by year 3). By years 3 and 4, the majority (approximately 75%) of severely damaged trees (with > 50% crown loss) died prior to beetle colonization. 4 The size of the beetle population tracked the abundance of available woody material from year-to-year within a plantation; populations were very large in the first 2 years, and declined significantly in the last 2 years. 5 Healthy standing red pines were apparently resistant to colonization by the beetles, despite the significant build-up in their populations. Hence, the results of the present study suggest that native bark beetle populations will not cause further tree mortality following such a disturbance in this region.