Weevil

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Weevil

  • bean weevil
  • large pine weevil
  • maize weevil
  • pine weevil

  • Terms modified by Weevil

  • weevil larva
  • weevil population
  • weevil species

  • Selected Abstracts


    Effect of time of year on the development of immature stages of the Large Pine Weevil (Hylobius abietis L.) in stumps of Sitka spruce (Picea sitchensis Carr.) and influence of felling date on their growth, density and distribution

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2004
    R. Moore
    Abstract:, The time of year and time of felling of a commercial stand of Sitka spruce (Picea sitchensis Carr.) were both shown to influence the spatial distribution and development of the large pine weevil, Hylobius abietis (L). Stump and root systems were excavated over a 5-month period in 1997, between 18 and 27 months after felling, and all immature H. abietis removed. On a site with a 6-month spread of felling dates in 1995, mean larval weights in 1997 were higher in stumps from earlier fellings, but H. abietis numbers were higher in stumps from later fellings. This appeared to be due to the continued presence of older, heavier larvae, laid as eggs in 1995, in stumps from earlier fellings, combined with a greater concentration of oviposition having occurred in 1996 in the fresher stumps of later fellings. Pupae were first found in excavated stumps on 12 June 1997 and adults on 29 July 1997. Emergence of the ,new generation' of adult weevils commenced on 7 August 1997. On average, 25% of H. abietis adults emerged in autumn 1997, 41% in 1998 and 34% in 1999. First emergence (1997) was proportionally higher in the areas felled earlier in 1995 than those felled later that year. However, the opposite was found for third emergence (1999) where emergence was greater for stumps created later in 1995. Larger stumps contained greater densities of H. abietis. Total ,potential' emergence was estimated to be between 46400 and 170825 H. abietis/ha. However, emergence traps indicated that only 40,80% managed to complete their development and emerge successfully. It is suggested that within-season felling date may be one of the most important factors affecting larval development, distribution and abundance; as well as subsequent damage levels associated with adult feeding. Consequently, knowledge of felling date could be crucial to developing methods of integrated forest management for this major forest pest. [source]


    Why are seed cones of Swiss stone pine (Pinus cembra) not attacked by the specialized pine cone weevil, Pissodes validirostris?

    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2001
    A case of host selection vs. host suitability
    Abstract The pine cone weevil, Pissodes validirostris Gyll. (Coleoptera: Curculionidae), attacks seed cones of most Eurasian pine species, except these of Swiss stone pine (Pinus cembra L.). Behavioural responses of adult weevils to cone volatile emissions of Swiss stone pine and to those of a common host, mountain pine (Pinus uncinata Ram.), were compared in an olfactometer. Weevils were significantly attracted by the volatile blend emitted by mountain pine, but Swiss stone pine volatiles elicited an inverse response, with most weevils moving in the opposite direction to the odour source. However, the majority of second instar weevil larvae that were extracted from mountain pine cones and transferred into Swiss stone pine cones were capable of developing to the adult stage. This suggests that Swiss stone pine cones do not contain strong feeding deterrents that could prevent larval development. The possible factors involved in the absence of colonization of Swiss stone pine cones by cone weevils are discussed. [source]


    Importance of long-term research in classical biological control: an analytical review of a release against the cabbage seedpod weevil in North America

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2006
    D. R. Gillespie
    Abstract:, Cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Col., Curculionidae), is an invasive alien pest that is spreading in North America. To aid with planning for introductions of European parasitoids in North America, we examined the status of the only classical biological control release against this pest in North America, which in 1949 introduced Mesopolobus morys, Stenomalina gracilis and Trichomalus perfectus (Hym., Pteromalidae). Weevils and parasitoids were reared in 2005 from mass collections of seedpods of Brassica napus, Brassica rapa and Raphanus raphanistrum (Brassicaceae) from 18 sites in the Fraser Valley, near Vancouver, British Columbia, Canada. Of the three European parasitoid species that were originally released, only S. gracilis was found. The predominant hymenopterous parasitoid species were Trichomalus lucidus, S. gracilis, Mesopolobus moryoides (Pteromalidae), Necremnus tidius (Eulophidae) and Eupelmus vesicularis (Eupelmidae). These constituted over 97% of the parasitoids reared, although overall parasitism was low. Only M. moryoides is clearly North American in distribution; other than S. gracilis, the remaining species were either accidentally introduced or are Holarctic in distribution. Based on these results, re-releases of M. morys and T. perfectus in North America should be considered as part of a classical biological control programme. However, redistribution of S. gracilis is not recommended at present because of potential conflicts with biological control programmes against weeds. Ongoing re-examination of classical biological control programmes can further our understanding of failure of release programmes, particularly when re-examination can be made in the light of improved taxonomy and systematics of the target and agent species. [source]


    Protected raspberry production accelerates onset of oviposition by vine weevils (Otiorhynchus sulcatus)

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010
    Scott N. Johnson
    1Soft fruit production is increasingly reliant on crops that are grown under the protection of plastic tunnels, which may also affect insect communities as a result of localized climate change and changes to host plant physiology and chemistry. In particular, insect development rates may differ from field populations, making it more difficult to target control measures. 2The present study investigated how protected environments affected adult vine weevil (Otiorhynchus sulcatus) feeding and reproduction on red raspberry (Rubus idaeus). We focused on the period between adult emergence and the onset of oviposition (i.e. the pre-reproductive period), which represents the optimal period for control. 3Tunnels were up to 4 °C warmer than field plantations in 2008, with plants growing significantly faster (50% increase in height and 16% increase in leaf area) than field grown plants. The carbon/nitrogen ratio in leaves was higher in tunnels (12.07) than the field (10.89) as a result of a significant decrease in nitrogen concentrations (3.40 and 3.90 mg g,1, respectively). 4Over 4 weeks, weevils consumed significantly more foliage in tunnels (370.89 mg) than weevils in the field (166.68 mg), suggesting compensatory feeding to counteract lower leaf nitrogen concentrations. Weevils in tunnels achieved sexual maturity 8 days earlier than those in the field and produced 20-fold more eggs by the time they were 5 weeks old. 5Applying a degree-day model showed good agreement between predicted and observed pre-reproductive periods for weevils in tunnels (36 and 30 days, respectively) and in field plots (41 and 38 days, respectively). [source]


    Tracking larval insect movement within soil using high resolution X-ray microtomography

    ECOLOGICAL ENTOMOLOGY, Issue 1 2004
    Scott N. Johnson
    Abstract., 1. In contrast to above-ground insects, comparatively little is known about the behaviour of subterranean insects, due largely to the difficulty of studying them in situ. 2. The movement of newly hatched (neonate) clover root weevil (Sitona lepidus L. Coleoptera: Curculinidae) larvae was studied non-invasively using recently developed high resolution X-ray microtomography. 3. The movement and final position of S. lepidus larvae in the soil was reliably established using X-ray microtomography, when compared with larval positions that were determined by destructively sectioning the soil column. 4. Newly hatched S. lepidus larvae were seen to attack the root rhizobial nodules of their host plant, white clover (Trifolium repens L.). Sitona lepidus larvae travelled between 9 and 27 mm in 9 h at a mean speed of 1.8 mm h,1. 5. Sitona lepidus larvae did not move through the soil in a linear manner, but changed trajectory in both the lateral and vertical planes. [source]


    Tillage affects the activity-density, absolute density, and feeding damage of the pea leaf weevil in spring pea

    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2010
    Timothy D. Hatten
    Abstract Conversion from conventional-tillage (CT) to no-tillage (NT) agriculture can affect pests and beneficial organisms in various ways. NT has been shown to reduce the relative abundance and feeding damage of pea leaf weevil (PLW), Sitona lineatus L. (Coleoptera: Curculionidae) in spring pea, especially during the early-season colonization period in the Palouse region of northwest Idaho. Pitfall traps were used to quantify tillage effects on activity-density of PLW in field experiments conducted during 2001 and 2002. As capture rate of pitfall traps for PLW might be influenced by effects of tillage treatment, two mark-recapture studies were employed to compare trapping rates in NT and CT spring pea during 2003. Also in 2003, direct sampling was used to estimate PLW densities during the colonization period, and to assess PLW feeding damage on pea. PLW activity-density was significantly lower in NT relative to CT during the early colonization period (May) of 2001 and 2002, and during the late colonization period (June) of 2002. Activity-density was not different between treatments during the early emergence (July) or late emergence (August) periods in either year of the study. Trap capture rates did not differ between tillage systems in the mark-recapture studies, suggesting that pitfall trapping provided unbiased estimates of PLW relative abundances. PLW absolute densities and feeding damage were significantly lower in NT than in CT. These results indicate that NT provides a pest suppression benefit in spring pea. [source]


    Glutathione S -transferase detoxification as a potential pyrethroid resistance mechanism in the maize weevil, Sitophilus zeamais

    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2003
    Daniel B. Fragoso
    Abstract Insecticide resistance patterns among 16 Brazilian populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were recognized by surveying resistance to three organophosphates (chlorpyrifos-methyl, malathion, and pirimiphos-methyl) and three pyrethroids (cypermethrin, deltamethrin, and permethrin). Two population clusters were obtained: one with three populations (Bragança Paulista, Cristalina, and Nova Andradina) showing low frequency of cypermethrin resistance (13,36%) and negligible frequency of deltamethrin resistance (2,9%); and another with six populations (Campos dos Goytacazes, Ivinhema, Patos de Minas, Penápolis, Uberlândia, and Venda Nova) showing low to negligible levels of pyrethroid resistance (0,23%). The remaining seven populations, including a susceptible, and a DDT- and pyrethroid-resistant reference populations (Sete Lagoas and Jacarezinho, respectively), were significantly different from each other and from the two recognized clusters. In contrast with pyrethroid resistance, organophosphate resistance was negligible except for chlorpyrifos-methyl in two populations (Fátima do Sul and Penápolis). There was no correlation between geographic distance and the Mahalanobis distance estimated from the resistance pattern ordination of the populations by canonical variate analysis, suggesting local selection and/or broad dispersal of resistant populations by grain trade. The results of biochemical in vitro studies measuring the activity of detoxification enzymes (esterases and glutathion S -transferases) in conjunction with canonical correlation analysis suggest a major involvement of enhanced conjugation by glutathione S -transferases (> 2-fold increase) in pyrethroid resistance and, in the case of cypermethrin resistance, enhanced phosphotriesterase activity. [source]


    Why are seed cones of Swiss stone pine (Pinus cembra) not attacked by the specialized pine cone weevil, Pissodes validirostris?

    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2001
    A case of host selection vs. host suitability
    Abstract The pine cone weevil, Pissodes validirostris Gyll. (Coleoptera: Curculionidae), attacks seed cones of most Eurasian pine species, except these of Swiss stone pine (Pinus cembra L.). Behavioural responses of adult weevils to cone volatile emissions of Swiss stone pine and to those of a common host, mountain pine (Pinus uncinata Ram.), were compared in an olfactometer. Weevils were significantly attracted by the volatile blend emitted by mountain pine, but Swiss stone pine volatiles elicited an inverse response, with most weevils moving in the opposite direction to the odour source. However, the majority of second instar weevil larvae that were extracted from mountain pine cones and transferred into Swiss stone pine cones were capable of developing to the adult stage. This suggests that Swiss stone pine cones do not contain strong feeding deterrents that could prevent larval development. The possible factors involved in the absence of colonization of Swiss stone pine cones by cone weevils are discussed. [source]


    Fumigant toxicity of Korean medicinal plant essential oils and components from Asiasarum sieboldi root against Sitophilus oryzae L.

    FLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2008
    Junheon Kim
    Abstract Medicinal plant essential oils and components from Asiasarum sieboldi were tested for their insecticidal activities against the rice weevil Sitophilus oryzae, using a fumigation bioassay. Responses varied with plant material and concentration. The LC50 value of A. sieboldi essential oil against rice weevil was 2.37 µg/ml air. Analysis by gas chromatography,mass spectrometry led to the identification of 20 compounds from A. sieboldi essential oil. Among identified compounds, five main compounds were tested for their insecticidal activity against rice weevil and compared to the toxicity of dichlorvos. Responses varied with compound and dose. Eucarvone was the most toxic, followed by safrole, with LC50 values of 3.32 and 11.27 µg/ml, respectively. LC50 values of other compounds were >25 µg/ml. The LC50 value of dichlorvos was 0.0081 µg/ml. Copyright © 2008 John Wiley & Sons, Ltd. [source]


    The specialist seed predator Bruchidius dorsalis (Coleoptera: Bruchidae) plays a crucial role in the seed germination of its host plant, Gleditsia japonica (Leguminosae)

    FUNCTIONAL ECOLOGY, Issue 2 2002
    K. Takakura
    Summary 1,This paper describes the germination mechanism of hard seeds of a species of honey locust, Gleditsia japonica, which can germinate only when externally damaged, in relation to four germinating factors: feeding damage by two specialist seed predators, a bean weevil (Bruchidius dorsalis) and a cydid bug (Adrisa magna); feeding damage by a generalist seed predator, a wild mouse (Apodemus speciosus); and physical damage. 2,In laboratory experiments, both the bean weevil and physical damage facilitated germination, while damage by the cydid bug and wild mouse did not. 3,In contrast to laboratory findings, field censuses of G. japonica seed survival revealed that more than 99% were damaged either by B. dorsalis or A. magna. Therefore, less than 0·5% of the seeds remained intact, preventing formation of a seed bank. 4,In addition, all germinating seeds found in the field contained B. dorsalis larvae. 5,These results strongly suggest that damage by B. dorsalis is a prerequisite for G. japonica germination, in contrast to the conventional view that physical disturbance, possibly flooding, is the primary germinating factor for hard seeds. [source]


    Thresholds of economic damage by clover seed weevil (Apion fulvipes Geoff.) and lesser clover leaf weevil (Hypera nigrirostris Fab.) on white clover (Trifolium repens L.) seed crops

    GRASS & FORAGE SCIENCE, Issue 4 2008
    L. M. Hansen
    Abstract Severe reductions in the seed yield of white clover can occur because of feeding by the white clover seed weevil Apion fulvipes and the lesser clover leaf weevil Hypera nigrirostris which together can reduce the seed yield by more than 0·50. From 2002 to 2006 five field experiments were carried out to investigate the relationship between the density of these two weevil species and seed yield of white clover. Damage caused by the weevils was calculated as the difference in the number of weevils and the difference in seed yield between the average of insecticide-treated and untreated plots. Loss of seed yield was expressed as a proportion of the seed yield in insecticide-treated plots, which allowed for a comparison between years as yields in insecticide-treated plots varied. A multiple regression approach was chosen in which proportional loss in seed yield was the response variable and the weevils A. fulvipes and H. nigrirostris were the independent variables. Data obtained from the experiments were used to construct the following threshold model of economic damage: [source]


    Resistance of stored bean varieties to Acanthoscelides obtectus (Coleoptera: Bruchidae)

    INSECT SCIENCE, Issue 4 2008
    Edson L.L. Baldin
    Abstract During bean seed storage, yield can be lost due to infestations of Acanthoscelides obtectus Say, the bean weevil. The use of resistant varieties has shown promising results in fighting these insects, reducing infestation levels and eliminating chemical residues from the beans. The expression of resistance to A. obtectus in bean varieties is frequently attributed to the presence of phytohemagglutinins, protease inhibitors and alpha-amylase, and especially to variants of the protein arcelin, which reduce the larval viability of these insects. To evaluate the effect of bean seed storage time on the resistance expression of bean varieties to A. obtectus, tests with seeds of three ages (freshly-harvested, 4-month-old, and 8-month-old) were conducted in the laboratory, using four commercial varieties: Carioca Pitoco, Ipa 6, Porrillo 70, ônix; four improved varieties containing arcelin protein: Arc.1, Arc.2, Arc. 3, Arc.4; and three wild varieties also containing arcelin protein: Arc.1S, Arc.3S, and Arc. 5S. The Arc.5S, Arc.1S, and Arc.2 varieties expressed high antibiosis levels against the weevil; Arc.1 and Arcs expressed the same mechanism, but at lower levels. The occurrence of oviposition non-preference was also observed in Arc.5S and Arc.1S. The Arc.3 and Arc. 4 varieties expressed low feeding non-preference levels against A. obtectus. The expression of resistance in arcelin-bearing, wild or improved varieties was affected during the storage of seeds, and was high under some parameters but low in others. The results showed that addition of chemical resistance factors such as protein arcelin via genetic breeding may be beneficial in improving the performance of bean crops. [source]


    Biology and host specificity of Aulacobaris fallax (Coleoptera: Curculionidae), a potential biological control agent for dyer's woad, Isatis tinctoria (Brassicaceae) in North America

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2009
    E. Gerber
    Abstract Dyer's woad, Isatis tinctoria, a plant of Eurasian origin is a problematic weed in western North America against which a classical biological weed control programme was initiated in 2004. Three European insect species were selected as candidate agents to control this invasive species, including the root-mining weevil Aulacobaris fallax. To determine its suitability as an agent, the biology and host specificity of A. fallax were studied in outdoor plots and in the field between 2004 and 2006 in its native European range. Aulacobaris fallax is a univoltine species that lays its eggs from March to August into leaf stalks and roots of dyer's woad. Larvae mine and pupate in the roots and adults emerge from August to October. Up to 62% of the dyer's woad plants at the field sites investigated were attacked by this weevil. In no-choice host-specificity tests, A. fallax attacked 16 out of 39 species and varieties within the Family Brassicaceae. Twelve of these are native to North America. In subsequent multiple-choice tests, seven species, all native to North America, suffered a similar level of attack as dyer's woad, while none of the European species were attacked. Our results demonstrate the importance of including test plant species that have not co-evolved with the respective candidate agent. In sum, we conclude that the risk of non-target effects is too high for A. fallax to be considered as a biological control agent for dyer's woad in the United States. [source]


    Evaluation of methods to control Phytonemus pallidus and Anthonomus rubi in organic strawberry production

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2007
    R. Berglund
    Abstract:, Use of the predatory mite Neoseiulus cucumeris (Oudemans) (Acari, Phytoseiidae) and a fleece cover in combination with pyrethrum application showed potential for control of two important pests in organic production of strawberry (Fragaria × ananassa Duch.), although there were some unexpected interactions between pyrethrum and the release of N. cucumeris that need to be investigated further. Two cultivars, Honeoye and Cavendish, were treated with pyrethrum with or without fleece to control strawberry blossom weevils [Anthonomus rubi Herbst. (Col., Curculionidae)] and N. cucumeris was released to control strawberry mites [Phytonemus pallidus (Banks) (Acari, Tarsonemidae)]. Number of strawberry mites, number of flower buds damaged by the weevil, incidence of grey mould and powdery mildew, and fruit yield were measured in two consecutive fruiting seasons. In Honeoye, the fleece in combination with pyrethrum decreased the proportion of damaged buds by 11,23% and increased yield by 49,91 g per plant. When pyrethrum was used alone it did not influence the number of damaged buds or yield. This indicates that the combined treatment was more effective because of the fleece. In Cavendish, the fleece and pyrethrum treatments were not found to be effective. Almost no P. pallidus was found in Honeoye and the results were not analysable. In plots with Cavendish where N. cucumeris had been released, there were approximately 50% fewer P. pallidus from the end of August onwards in 2003. However, this response did not significantly influence the succeeding year's yield. The number of fruits infected with fungi was very low and no effects were observed for any of the treatments. [source]


    Importance of long-term research in classical biological control: an analytical review of a release against the cabbage seedpod weevil in North America

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2006
    D. R. Gillespie
    Abstract:, Cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Col., Curculionidae), is an invasive alien pest that is spreading in North America. To aid with planning for introductions of European parasitoids in North America, we examined the status of the only classical biological control release against this pest in North America, which in 1949 introduced Mesopolobus morys, Stenomalina gracilis and Trichomalus perfectus (Hym., Pteromalidae). Weevils and parasitoids were reared in 2005 from mass collections of seedpods of Brassica napus, Brassica rapa and Raphanus raphanistrum (Brassicaceae) from 18 sites in the Fraser Valley, near Vancouver, British Columbia, Canada. Of the three European parasitoid species that were originally released, only S. gracilis was found. The predominant hymenopterous parasitoid species were Trichomalus lucidus, S. gracilis, Mesopolobus moryoides (Pteromalidae), Necremnus tidius (Eulophidae) and Eupelmus vesicularis (Eupelmidae). These constituted over 97% of the parasitoids reared, although overall parasitism was low. Only M. moryoides is clearly North American in distribution; other than S. gracilis, the remaining species were either accidentally introduced or are Holarctic in distribution. Based on these results, re-releases of M. morys and T. perfectus in North America should be considered as part of a classical biological control programme. However, redistribution of S. gracilis is not recommended at present because of potential conflicts with biological control programmes against weeds. Ongoing re-examination of classical biological control programmes can further our understanding of failure of release programmes, particularly when re-examination can be made in the light of improved taxonomy and systematics of the target and agent species. [source]


    Estimating dispersal rate of the silky cane weevil (Coleoptera: Curculionidae),

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2005
    H. Puche
    Abstract:, The objective of this study was to estimate the silky cane weevil rate of dispersal under near-natural conditions inside a screened enclosure where an array of buckets was baited with cut sugarcane stalks. One hundred weevils were released and weevils inside the buckets were counted hourly for 8 h, and then 24 and 48 h after release. A passive diffusion model was used to estimate the weevil's dispersal and disappearance rates, within and between rows of buckets with sugarcane. The weevils concentrated around the release point and slowly moved towards the boundaries of the experimental plot over time with an overall average dispersal rate of 2.8 ± 3.58 cm2/h. Dispersal and disappearance rates within and between rows were not significantly different among the time intervals considered (1,8, 8,24 and 24,48 h after release) except for the 1,8 time interval on the array representing the release point when the dispersal rate, D, was significantly higher than those at other time intervals. Continuum of the substratum to disperse from one side of the array to another via a wooden bridge may explain the higher dispersal rate through this array. The number of buckets exposed to the sun during the morning hours was significantly higher on those rows exposed to the sun (south side of the screen enclosure) than on the shaded side. Longer times of bucket exposure to the sun may explain the predominant distribution of weevils in that area suggesting that the weevil population is constantly expanding and retracting according to micro environmental conditions. [source]


    Coexistence of two mitochondrial DNA haplotypes in Japanese populations of Hypera postica (Col., Curculionidae)

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2005
    R. Kuwata
    Abstract:, In Japan, the alfalfa weevil, Hypera postica, was first recorded in 1982 from Fukuoka and Okinawa Prefectures and has been spreading to many other prefectures. The weevil seriously infests the Chinese milk vetch, Astragalus sinicus, one of the most important honey resources for honeybees in Japan. Direct sequencing of partial mitochondrial DNA and PCR-RFLP data for alfalfa weevil individuals indicated the coexistence of two haplotypes at various localities in Japan. Molecular phylogenetic analysis for H. postica haplotypes and strains indicated that the two Japanese haplotypes had not derived from a single genetic origin. Based on the results, special comments are made on biological control measures using introduced parasitic waSPS. [source]


    Susceptibility of various developmental stages of the maize weevil, Sitophilus zeamais Motschulsky (Col., Curculionidae) to methyl iodide in brown rice

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2005
    S. I. Faruki
    Abstract:, The efficacy of methyl iodide (MI) as a fumigant against all developmental stages of the maize weevil, Sitophilus zeamais Motsch. was investigated. Tests were conducted with concentrations of 1.5, 1.8, 2.1, 2.4, 2.7 and 3.0 mg/l, for a 6-h exposure period. Values of LC50, LC95 and LC99 of MI for immatures and adult stages were determined. The present laboratory tests showed that MI was toxic to various life stages of S. zeamais at relatively short exposure periods. At the LC50 and LC95 levels, the most susceptible stage was the egg stage followed by larvae, pupae and adults (1-day mortality). The egg was found to be most susceptible to MI, requiring 0.81 and 2.16 mg/l for 50 and 99% mortality, respectively, while the adult was most tolerant, requiring 2.30 and 3.02 mg/l for 50 and 99% mortality, respectively, based on 1-day mortality count. Pupae were less susceptible to MI than egg and larvae, requiring 1.47 and 3.19 mg/l for 50 and 99% mortality, respectively. Based on the present toxicity tests, MI has the potential for use as a fumigant to control all developmental stages of the maize weevil, S. zeamais. [source]


    Influence of different sugars on the longevity of Bathyplectes curculionis (Hym., Ichneumonidae)

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2004
    H. Spafford Jacob
    Abstract:, Floral nectars, homopteran honeydews and honey are known to increase parasitoid longevity. However, these foods are composed of several sugars which may differentially affect longevity. We tested the effects of individual sugars and mixtures on the longevity of Bathyplectes curculionis Thomson (Hym., Ichenumonidae), a natural enemy of the alfalfa weevil. There was a significant difference in the longevity of female wasps on the various diets. Glucose or fructose alone appeared to have the most benefits while trehalose and melezitose were not as useful for increasing wasp longevity. Suitability of these sugars for provisioning food for parasitoids in the field is discussed. [source]


    Effect of time of year on the development of immature stages of the Large Pine Weevil (Hylobius abietis L.) in stumps of Sitka spruce (Picea sitchensis Carr.) and influence of felling date on their growth, density and distribution

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2004
    R. Moore
    Abstract:, The time of year and time of felling of a commercial stand of Sitka spruce (Picea sitchensis Carr.) were both shown to influence the spatial distribution and development of the large pine weevil, Hylobius abietis (L). Stump and root systems were excavated over a 5-month period in 1997, between 18 and 27 months after felling, and all immature H. abietis removed. On a site with a 6-month spread of felling dates in 1995, mean larval weights in 1997 were higher in stumps from earlier fellings, but H. abietis numbers were higher in stumps from later fellings. This appeared to be due to the continued presence of older, heavier larvae, laid as eggs in 1995, in stumps from earlier fellings, combined with a greater concentration of oviposition having occurred in 1996 in the fresher stumps of later fellings. Pupae were first found in excavated stumps on 12 June 1997 and adults on 29 July 1997. Emergence of the ,new generation' of adult weevils commenced on 7 August 1997. On average, 25% of H. abietis adults emerged in autumn 1997, 41% in 1998 and 34% in 1999. First emergence (1997) was proportionally higher in the areas felled earlier in 1995 than those felled later that year. However, the opposite was found for third emergence (1999) where emergence was greater for stumps created later in 1995. Larger stumps contained greater densities of H. abietis. Total ,potential' emergence was estimated to be between 46400 and 170825 H. abietis/ha. However, emergence traps indicated that only 40,80% managed to complete their development and emerge successfully. It is suggested that within-season felling date may be one of the most important factors affecting larval development, distribution and abundance; as well as subsequent damage levels associated with adult feeding. Consequently, knowledge of felling date could be crucial to developing methods of integrated forest management for this major forest pest. [source]


    Sexing adults of the strawberry blossom weevil, Anthonomus rubi (Col., Curculionidae)

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2002
    P. J. Innocenzi
    Of several previously reported methods for sexing the strawberry blossom weevil, the presence of thorns on the intermediary coxae of males is the most convenient and unambiguous. Uniform pitting on the dorsal elytra of females provides the possible selective pressure for male thorn development. [source]


    The effect of wheat ,-amylase inhibitors incorporated into wheat-based artificial diets on development of Sitophilus granarius L., Tribolium confusum Duv., and Ephestia kuehniella Zell

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2002
    J. R. Warchalewski
    Artificial grain kernels made from ground wheat grain, commercial wheat starch and wheat proteinaceous ,-amylase inhibitors were used as diets for adults of the granary weevil (Sitophilus granarius L). For the confused flour beetle (Tribolium confusum Duv.) and the Mediterranean flour moth (Ephesitia kuehniella Zell.), a friable mixture of the diets was used. The results of feeding trials showed that the survival of S. granarius adults was not correlated with the soluble proteins extracted from wheat and amylolytic activity located in this protein fraction. On the other hand, the weight of dust (the index of feeding intensity) produced during feeding depended on the presence of ,-amylase and trypsin inhibitors in wheat-based diets. Ephesitia kuehniella larvae did not develop at all on a diet consisting of 50% wheat starch and 50% crude ,-amylase inhibitors from wheat. The same diet lengthened the development time of T. confusum larvae by 15.1 days. These results attest to the existence of a specific native enzymatic apparatus in the alimentary canals of these three grain pests. However, the highly active insect ,-amylase inhibitors appear to have a limited influence on the developmental parameters studied although some reduction of insects populations might be expected. [source]


    Ecological play in the coevolutionary theatre: genetic and environmental determinants of attack by a specialist weevil on milkweed

    JOURNAL OF ECOLOGY, Issue 6 2003
    Anurag A. Agrawal
    Summary 1We studied the genetic and environmental determinants of attack by the specialist stem-attacking weevil, Rhyssomatus lineaticollis on Asclepias syriaca. 2In natural populations, the extent of stem damage and oviposition were positively correlated with stem width, but not stem height. We hypothesized that both genotypic and environmental factors influencing stem morphology would affect attack by weevils. 3In a common garden study with 21 full-sib families of milkweed, both phenotypic and genetic correlations indicated that weevils impose more damage and lay more eggs on thicker stemmed plants. 4Of three other putative resistance traits, only latex production showed a negative genetic correlation with weevil attack. 5When neighbouring grasses were clipped to reduce light competition, focal milkweed plants received up to 2.6 times the photosynthetically active radiation and 1.6 times the red to far red ratio of light compared with plants with intact grass neighbours. Focal milkweed plants were therefore released from the classic neighbour avoidance response and had 20% shorter internode lengths, were 30% shorter, and had 90% thicker stems compared with controls. 6Clipping of grass neighbours resulted in nearly 2.7 times the damage and oviposition by stem weevils, thus supporting the hypothesis of an environmental or trait-mediated indirect influence on resistance. 7Although attack of plants by weevils strongly increases the probability of stem mortality, thicker stems experience lower mortality, thus counteracting the selective impact of weevil-induced plant mortality. 8The determinants of attack on milkweeds include both genetic variation for stem thickness and an indirect environmental influence of plant neighbours. If milkweeds and weevils are coevolving, the interaction is diffuse because the ecological neighbourhood is likely to modify the patterns of reciprocal natural selection. [source]


    Protected raspberry production accelerates onset of oviposition by vine weevils (Otiorhynchus sulcatus)

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010
    Scott N. Johnson
    1Soft fruit production is increasingly reliant on crops that are grown under the protection of plastic tunnels, which may also affect insect communities as a result of localized climate change and changes to host plant physiology and chemistry. In particular, insect development rates may differ from field populations, making it more difficult to target control measures. 2The present study investigated how protected environments affected adult vine weevil (Otiorhynchus sulcatus) feeding and reproduction on red raspberry (Rubus idaeus). We focused on the period between adult emergence and the onset of oviposition (i.e. the pre-reproductive period), which represents the optimal period for control. 3Tunnels were up to 4 °C warmer than field plantations in 2008, with plants growing significantly faster (50% increase in height and 16% increase in leaf area) than field grown plants. The carbon/nitrogen ratio in leaves was higher in tunnels (12.07) than the field (10.89) as a result of a significant decrease in nitrogen concentrations (3.40 and 3.90 mg g,1, respectively). 4Over 4 weeks, weevils consumed significantly more foliage in tunnels (370.89 mg) than weevils in the field (166.68 mg), suggesting compensatory feeding to counteract lower leaf nitrogen concentrations. Weevils in tunnels achieved sexual maturity 8 days earlier than those in the field and produced 20-fold more eggs by the time they were 5 weeks old. 5Applying a degree-day model showed good agreement between predicted and observed pre-reproductive periods for weevils in tunnels (36 and 30 days, respectively) and in field plots (41 and 38 days, respectively). [source]


    Temptations of weevil: feeding and ovipositional behaviour of Hylobius warreni Wood on host and nonhost bark in laboratory bioassays

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2009
    Gareth R. Hopkins
    Abstract 1Warren root collar weevil Hylobius warreni Wood (Coleoptera: Curculionidae) is a long-lived, flightless insect native to coniferous forests across northern North America. Girdling by larval feeding causes significant mortality on young trees. The insect poses considerable challenges to reforestation. 2Adult weevils feed on all life stages of a variety of coniferous hosts prior to oviposition. Their relative feeding preferences, however, have not been quantified. Moreover, it is not known whether host bark influences oviposition behaviour. 3Feeding preferences of adult weevils were tested in both choice and no-choice laboratory bioassays using small branches from three conifers (lodgepole pine Pinus contorta var. latifolia, interior hybrid spruce Picea glauca×engelmannii, and Douglas-fir Pseudotsuga menziesii) and one deciduous tree (trembling aspen Populus tremuloides). Measurements included the surface area of bark consumed, rate of consumption, the number of days of feeding, and, in the no-choice assay, the number of eggs oviposited. 4Bark consumption was greatest on pine and Douglas-fir, followed by spruce. Little to no feeding occurred on aspen. Consumption did not vary between male versus female insects for any of the feeding metrics quantified. 5The presence of aspen branches did not inhibit feeding on any of the other species in the choice bioassays. 6The number of eggs laid by female insects did not differ significantly among tree species in the no-choice assay. Eggs were laid indiscriminately in the presence of all four host types. 7Results and opportunities for future research are discussed in the context of formulating new integrated pest management strategies for this insect, which is increasingly important in the period of reforestation subsequent to the mountain pine beetle epidemic in western Canada. [source]


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

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2006
    Kristina Wallertz
    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. [source]


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

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2006
    Riitta Toivonen
    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. [source]


    Insect growth-reducing and antifeedant activity in Eastern North America hardwood species and bioassay-guided isolation of active principles from Prunus serotina

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2000
    S. Omar
    Abstract 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. [source]


    Spatial economics of biological control: investing in new releases of insects for earlier limitation of Paterson's curse in Australia

    AGRICULTURAL ECONOMICS, Issue 3 2002
    T.L. Nordblom
    Abstract Paterson's curse and related weeds (Echium spp.) were introduced as garden flowers before 1850 and have spread to over 30 million ha in southern Australia. Four hundred successful releases of crown weevil (M. lawatus) populations specifically targeting Echium spp. were made in the 1993,2000 period. Based on the timing, location and performance of these past releases of beneficial insects, spatially and temporally specific trajectories of biocontrol have been simulated. Insect populations established by the past releases are expected to cover expanding areas at densities sufficient to limit host Echium infestations only over the next 25-50 years. The present analysis tackles the questions of where and how many additional releases are economically justified to speed up this process. We identify 31 districts in which diminishing niches for further insect releases are projected over time, according to the locations of damaging weed infestations and the timing, location and numbers of past insect releases. Benefits of biocontrol are expressed in terms of the value of recovered pasture productivity, keyed to estimates of loss and to historical district livestock inventories converted to dry sheep equivalent (DSE) feed availability levels to which prices are applied. Expected marginal contributions of increments of new releases were simulated for each of the 31 districts, subject to the spacehime limitations of each niche. Our explicit accounting for the spatial and temporal dimensions has made possible the economically optimd targeting of new biocontrol releases. For example, at $12/DSE and a marginal cost of $2000 per release, with a discount rate of l0%, we find there is a case for a program of over 400 new releases targeted to 17 districts, with as few as five releases to each of several and as many as 70 releases in one district. [source]


    Raymondionymus eximius sp. n., a remarkable new species of endogeic weevil (Coleoptera, Curculionoidea, Raymondionymidae)

    MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 1 2006
    Massimo Meregalli
    Abstract Raymondionymus eximius sp. n. from Central Italy (Mount Viglio, on the Simbruini Mountains) is described. The new species differs from all the other species of the genus for its pronotum with a deep Y-shaped depression, the more globose elytra and the acutely pointed aedeagus. Short remarks on its taxonomic position within the genus are given. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]