Geographical distribution of the weevil subfamily Ceutorhynchinae (Coleoptera, Curculionidae)

A brief general characteristic and review of distribution of the subfamily Ceutorhynchinae over zoogeographical realms are given, with an emphasis on the distribution within the Holarctic and Palaearctic. The potential of exploiting landscapes of all natural zones of the Holarctic by a low-rank taxon is exemplified by the Holarctic Ceutorhynchus cochleariae (Gyll.) species-group comprising ca. 20 species evenly distributed between the Palaearctic and Nearctic. Although neighboring with the powerful centers of tropical biota, the Holarctic fauna of the subfamily Ceutorhynchinae is formed mostly of endemic and subendemic genera which are especially abundant in the Palaearctic. This region possesses the most diversified generic and species composition of the fauna consisting of predominantly endemic and subendemic genera (in the Mediterranean and Saharo-Gobian regions, also of the highly diversified tribe Oxyonychini) up to its southern border. The existence of characteristic transitional faunas in the zones of contact of the Holarctic fauna with the faunas of the tropical regions in East Asia and Mexico is shown. These transitional faunas include a considerable number of endemic taxa of the genus and species groups. A conspicuous feature of the Palaearctic ceutorhynchine fauna is the rather numerous complex of the upland and high-latitude species.     

Strain distribution of alfalfa weevil (Coleoptera: Curculionidae) in an intergrade zone

Strain distribution for the alfalfa weevil, Hypera postica (Gyllenhal), was determined for the five major alfalfa-growing regions of New Mexico. Mitochondrial DNA from field-collected weevils at each location was digested and sequenced to differentiate among strains. Eastern, Egyptian, and western strains were recovered, along with a population not matching any known strain. The majority of sites examined had populations of two strains intermingled within a field. This is the first confirmation of the presence of all three strains within the same geographic region. Possible implications for alfalfa weevil management are discussed.     

Impact of azadirachtin on vine weevil (Coleoptera: Curculionidae) reproduction

Abstract 1 The dose–response of azadirachtin on vine weevil, Otiorhynchus sulcatus (Fabricius), reproduction is investigated by confining adults to feed on treated Taxus × media leaves, and by counting and evaluating development in the resulting eggs. 2 A dosage‐dependent reduction in oviposition is discovered for foliar surface residues of azadirachtin, with an EC₅₀ of 25–50 parts per million (p.p.m) and 99.2% inhibition of viable egg production with 100 p.p.m. 3 Switching weevils from treated to untreated foliage allows reproductive capability to be restored for weevils that cease egg laying after azadirachtin exposure of 50 p.p.m. Weevils that had already started laying eggs in untreated groups soon cease oviposition once switched to azadirachtin‐treated foliage. 4 A transovarial effect results in a decrease in the percentage of viable eggs as the azadirachtin concentration increases. 5 The amount of feeding on foliage does not appreciably decrease at these hormonally effective concentrations, and adult weevil mortality is only slightly greater in the azadirachtin‐treated groups. Therefore, the overall effect of azadirachtin on weevil populations in the field is difficult to assess, except by collecting weevils to determine whether they are able to lay viable eggs.     

Temperature-dependent development and reproduction of the boll weevil (Coleoptera: Curculionidae)

Abstract Effects of temperature on development, survival, and fecundity of boll weevil, Anthonomus grandis grandis Boheman, were assessed at 10, 11, 12, 15,20,25,30,35,45, and 46 °C; 65% relative humidity; and a photoperiod of 13:11 (L: D) h. The mortality of boll weevil immature stages was 100% at 12°C and decreased to 36.4% as the temperature increased to 25°C. When the temperature increased from 30 °C to 45 °C, the mortality of weevils also increased from 50.1% to 100%. From 15°C to 35°C, the bollweevilpreimaginal development rate was linearly related to temperature. The average development time of total boll weevil immature lifestages decreased 3.6-fold and the preovipositional period decreased 3.3-fold when the temperature was increased from 15°C to 30°C. The lower threshold for development was estimated at 10.9, 6.6, 7.0, and 9.0 °C for eggs, larval, pupal, and total immature stages, respectively, with total thermal time requirement to complete immature stages of 281.8 DD (degree day) (15°C) and 247.8 DD (35 °C). At 1LC and 46°C, weevil females did not oviposit. Longevity of adult females decreased 4.6-fold with increasing temperatures from 15°C to 35°C. Fecundity increased with increasing temperatures up to 30°C and significantly decreased thereafter. These findings will be useful in creating a temperature-based degree-day model for predicting the occurrence of key life stages in the field. An accurate predictor of a pest's development can be very important in determining sampling protocols, timing insecticide applications, or implementing an integrated pest management control strategy targeting susceptible life stages.     

Hexane extracts from Tephrosia vogelii Hook. f. protect stored maize against the weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Powdered dried leaves of Tephrosia vogelii (Hook) (Leguminosae: Papilionoideae) were extracted using hexane, acetone, and ethanol. The extracts were tested for their ability to protect stored maize from damage by Sitophilus zeamais Motschulsky, the major maize weevil in Africa. The acetone and ethanol extracts were ineffective, but the hexane extract had a relatively high efficacy, producing within 7 days a slow reduction in adult survival, reduced numbers of eggs laid and reduced numbers of F₁ progeny, resulting in seed damage averaging 8.8% compared with 98.6% in the untreated control after one generation. This hexane extract provided control of S. zeamais at a higher level compared with neem (the botanical control) but at a lower level compared with pirimiphos‐methyl (the synthetic control). These findings are discussed in the context of T. vogelii containing rotenoids.     

Fine-tuning the composition of the cranberry weevil (Coleoptera: Curculionidae) aggregation pheromone

The cranberry weevil Anthonomus musculus Say is a key pest of highbush blueberries (Vaccinium corymbosum L.) and cranberries (Vaccinium macrocarpon Aiton) in the northeastern United States. Previous studies have reported A. musculus adult attraction to traps baited with the aggregation pheromone of the pepper weevil Anthonomus eugenii Cano, likely because these two weevils share similar pheromone blends that differ only in two components. The A. musculus aggregation pheromone contains (Z)-2-(3,3-dimethylcyclohexylidene) ethanol (Z grandlure II), (Z)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure III), (E)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure IV) and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol); whereas A. eugenii produces a pheromone blend that includes (E)-2-(3,3-dimethylcyclohexylidene) ethanol (E grandlure II) and (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid) in addition to the four A. musculus pheromone components. Here, we hypothesized that differences in pheromone composition between these two species influence A. musculus adult attraction to its aggregation pheromone. To test this, we studied the response of A. musculus to its pheromone blend with and without E grandlure II and geranic acid, a commercial A. eugenii pheromone lure and a no-lure control in highbush blueberry and cranberry fields in New Jersey and Massachusetts, respectively. Regardless of crop type, A. musculus adults were more attracted to their four-component pheromone blend and the blend plus geranic acid than the commercial A. eugenii pheromone and the no-lure controls. The A. musculus pheromone blend plus E grandlure II and the A. eugenii pheromone blend also captured more A. musculus adults than the no-lure control but not compared to the commercial A. eugenii pheromone. Further analysis showed that A. musculus adults are significantly (~27%) less attracted to their pheromone blend if it contains E grandlure II, although the addition of geranic acid did not affect their response. These findings may help guide future efforts towards the development of behaviour-based tools to monitor and manage A. musculus.     

Strategies of emergence in the chestnut weevil Curculio elephas (Coleoptera: Curculionidae)

In the chestnut weevil Curculio elephas, adult emergences spread over 3 or 4 years due to prolonged larval diapause in some individuals. Weevils with an extended diapause emerge, on the average, 1–10 days before those with simple diapause, but whatever the age of insects, emergences occur always from mid-August to early October. When the summer is dry, some adults cannot emerge because of the hardness of the soil. Emergence sucess of adults is smaller in females than in males. The result is that the sex ratio is female-biased before emergence and male-biased after. Summer drought cannot be predicted by the chestnut weevil, and when the soil is dry 27–78% of females cannot emerge and do not reproduce. The year after a summer drought, many reproducing females may emerge from larvae with prolonged diapause. These results suggest an evolutionary influence on the variability in diapause duration. Computer simulations and observations do not support the hypothesis that the main cause of variation in diapause length is the existence of several distinct genotypes within populations. On the contrary, our data strengthen the hypothesis for coin-flipping plasticity discussed in a previous paper.     

Life history of the Onopordum capitulum weevil Larinus latus (Coleoptera: Curculionidae)

The population structure and stage-specific survival of the capitulum weevil, Larinus latus, a potential control agent for weedy Onopordum thistles in Australia, was studied in its native range in Greece. Although fecundity of this univoltine insect was low (35.4 eggs/female), survival was relatively high, with 45% of eggs reaching adulthood when protected from predators and parasitoids, and 23% surviving when exposed to these natural enemies. Other mortality factors of importance for immature stages were a failure to establish, due largely to oviposition by females on inappropriate sites on the thistle capitula, and inter- and intraspecific competition for larval resources. Once emerged, adult losses due to overwintering mortality and net migration were estimated at a further 48%. Despite these losses there was a net doubling of the population at the study site between Onopordum flowering seasons. The data suggest that movement of adults occurs both within and between patches and that variability in population size relative to the resource base is low. Overall, L. latus may be considered a K-strategist which forms relatively stable populations over a fragmented habitat and which maintains its population integrity through a certain degree of annual redistribution. The implications of these data for the potential effectiveness of L. latus as a biological control agent of weedy Onopordum spp. are discussed.     

云南木蠹象的生物学研究

云南木蠹象Pissodes yunnanensis Langor et Zhang是我国西南地区近年来发现的森林蛀干害虫。该虫在云南西北部的丽江地区一年发生一代。成虫于6月下旬开始产卵, 产卵部位为当年生或头年生枝梢。7月上旬幼虫开始孵化,幼虫有4个龄期。11月中旬后,幼虫开始在受害枝内越冬,次年2月中下旬恢复活动。3月下旬至5月上旬为蛹期,4月中旬开始羽化。该虫主要危害云南松幼树,常造成受害树长势下降和树干畸形,连续危害2～3年可导致树木干枯死亡。     

Larval morphology of the weevil genus Ceutorhynchus (Coleoptera, Curculionidae) from Middle Asia

Larvae of three species of the weevil genus Ceutorhynchus (C. subtilirostris Schultze., C. viator Faust, and C. setosellus Voss) are described from Middle Asia for the first time. The larvae differ in the shape of frons, structure of the labrum, and chaetotaxy of the epicranium, frons, and lacinia. A key to the species described is given.     

A review of the biology and control of the vine weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae)

At the turn of the century, damage by Otiorhynchus sulcatus was sporadic and limited to small areas. Increasing horticultural intensification and the adoption of husbandry techniques favourable to the weevil, such as the use of polythene mulches, increased its pest status. The development of the early inorganic pesticides reduced the number of serious outbreaks of this pest and weevil control was further improved by the development of the persistent organochlorine insecticides in the 1940's. The banning of a number of the more persistent insecticides over recent years has now left the horticultural industry in a very vulnerable position. O. sulcatus is now a pest on a range of horticultural crops throughout the temperate regions of the world. Infestations are most common in Europe (where it originated) and the USA, and nearly 150 plants species have been identified as potential hosts to O. sulcatus. Damage is most frequently caused by the root feeding larval stage. Populations as low as one larva plant can kill sensitive species such as Cyclamen. Severe damage by the leaf feeding adults is less common, although low levels of damage or contamination by adults may be unacceptable in certain situations. There is one generation a year. Oviposition by the flightless parthenogenetic females occurs over the summer months with oviposition rates of c. 500 and 1200 eggs adult^-1for outdoor and laboratory populations, respectively. O. sulcatus mainly overwinters as larvae, although significant numbers of adults may survive in areas where winter temperatures are not too severe. A number of natural enemies, such as hedgehogs, frogs and predatory beetles, help to maintain O. sulcatus populations at a low level in natural environments, but they are less successful in intensive horticultural systems where persistent chemicals have been heavily relied on to maintain the population below the economic threshold level. Increasing environmental concern is now forcing growers to consider new pest control strategies. Controlled release formulations of non-persistent products, such as fonofos and chlorpyrifos, have shown potential as control agents for O. sulcatus larvae. Biological control agents, such as insect parasitic nematodes, have been developed commercially and new microbial control agents are in the process of development. Most of the new control products are directed towards control of O. sulcatus larvae. Adult vine weevils are nocturnal and a much more difficult target for the new control agents. It is likely that an integrated approach to pest control will be required to maintain O. sulcatus populations below their economic threshold level.     

Molecular cloning of a cysteine proteinase cDNA from the cotton boll weevil Anthonomus grandis (Coleoptera: Curculionidae)

The cotton boll weevil (Anthonomus grandis) causes severe cotton crop losses in North and South America. This report describes the presence of cysteine proteinase activity in the cotton boll weevil. Cysteine proteinase inhibitors from different sources were assayed against total A. grandis proteinases but, unexpectedly, no inhibitor tested was particularly effective. In order to screen for active inhibitors against the boll weevil, a cysteine proteinase cDNA (Agcys1) was isolated from A. grandis larvae using degenerate primers and rapid amplification of cDNA ends (RACE) techniques. Sequence analysis showed significant homologies with other insect cysteine proteinases. Northern blot analysis indicated that the mRNA encoding the proteinase was transcribed mainly in the gut of larvae. No mRNA was detected in neonatal larvae, pupae, or in the gut of the adult insect, suggesting that Agcys1 is an important cysteine proteinase for larvae digestion. The isolated gene will facilitate the search for highly active inhibitors towards boll weevil larvae that may provide a new opportunity to control this important insect pest.     

小果油茶上油茶象的产卵策略

【目的】油茶象Curculio chinensis Chevrolat是我国特有木本油料树种——油茶Camellia spp.的专性蛀果害虫,常导致其大量落果。本文旨在揭示该虫发生危害与寄主果实大小的关系,并探讨其产卵行为策略。【方法】于油茶象产卵高峰期在小果油茶Camellia meiocarpa林随机采摘960个果实,清查油茶象刺孔数和窝卵数,并对果重、果长和果径进行了测量,用单因素方差分析比较产卵果、取食果和非受害果大小差异性,用线性回归分析果实特征对油茶象取食及产卵活动的影响。同时对油茶象雌虫进行了果实大小选择性试验,用配对样本t检验分析选择果与非选择果的大小差异性。【结果】在果重、果长、果径和果实体积方面,产卵果取食果非受害果(P0.01),刺孔数、窝卵数和寄生率与果实大小呈极显著线性正相关(P0.01),说明油茶象雌虫优先选择大果实取食和产卵。当两供试果实差异显著时,油茶象雌虫对大果实表现出明显的偏好选择性,危害12 h后,重受害果长度和直径都显著大于轻受害果(P0.01)。油茶象雌虫每次只产1粒卵,卵单产是油茶象本身的属性,与果实特征无关。【结论】油茶象优先选择大果实取食,支持最优觅食理论。油茶象优先选择大果实产卵。窝卵数越小,油茶象种内竞争越弱,幼体正常发育并成功脱果的概率越高,适合度增加。卵单产是油茶象应对寄主果实食物资源限制作用的一种"风险分散"行为适应策略。     

Combining vegetable oil and sub-lethal concentrations of Imidacloprid with Beauveria bassiana and Metarhizium anisopliae against adult guava weevil Conotrachelus psidii (Coleoptera: Curculionidae)

Of the insect pests that attack guava fruits, the guava weevil, Conotrachelus psidii Marshall, 1922 (Coleoptera: Curculionidae), is one of the most important in Brazil. In search of alternatives to chemical pesticides, this study was performed to select fungal isolates of Beauveria bassiana and Metarhizium anisopliae as potential candidates for the control of adult C. psidii. Tests were carried out using three products applied with the entomopathogenic fungi: Tween 80, sunflower oil and Imidacloprid (IMI). A sub-lethal concentration of IMI was determined (100 ppm). The results demonstrated that LPP 19 and LPP 114 were the most effective isolates when used in combination with all of the products. The least virulent isolate, ESALQ 818, when applied in Tween 80 caused only 26.6% mortality, however, this isolate showed significantly improved efficiency when applied together with either sunflower oil or IMI, causing 57.3 and 88.6% mortality, respectively. The efficiency of all the isolates tested here improved when applied together with IMI, with LT₅₀ values of 5.3–10.3 days when compared to LT₅₀ values in Tween alone of 9.5–17 days. The isolate that produced the highest number of conidia on the cadavers of adult C. psidii was LPP138, independent of the product used; however, conidial production was slightly reduced when fungi were applied together with IMI. These results are promising for developing new formulations of the isolates to be tested in the field.     

Molecular and morphometric assessment of the taxonomic status of Ectemnorhinus weevil species (Coleoptera: Curculionidae, Entiminae) from the sub-Antarctic Prince Edward Islands

There are long‐standing controversies on the taxonomic status of Ectemnorhinus weevil species occurring on the sub‐Antarctic Prince Edward Islands. Since the two islands that constitute the Prince Edward Islands archipelago (PEIA), Marion Island (MI) and Prince Edward Island (PEI), differ in terms of alien invasive species such as the introduced house mouse Mus musculus and conservation management strategies, it is important to consider inter‐island dynamics when investigating inter‐specific relationships. Using a combined molecular phylogenetic and morphometric approach, we attempted to resolve the taxonomic status of the PEIA Ectemnorhinus weevil species. A COI gene phylogeny was inferred following the genetic characterization of 52 Ectemnorhinus weevils from both islands, and morphometric assessment using a set of 15 linear, external measurements was used to differentiate between the two currently recognized species, Ectemnorhinus similis and Ectemnorhinus marioni. Analyses revealed the presence of two genetically and morphometrically distinct species on PEI, whilst evidence for a single species, comprising diverse genetically discrete populations was found on MI. Based on these results, the species unique to PEI has been designated Ectemnorhinus kuscheli n. sp. whilst we confirm the synonymy between E. similis and E. marioni, the two species originally described from MI. E. kuscheli appears to be restricted to PEI, whereas E. similis occurs on both MI and PEI.     

Abundance and survival of a seed-infesting weevil, Pseudanthonomus hamamelidis (Coleoptera: Curculionidae), on its variable-fruiting host plant, witch-hazel (Hamamelis virginiana)

Abstract. 1. The relative importance of seed abundance and of mortality factors in the population biology of Pseudanthonomus hamamelidis , a hostspecific predispersal seed predator on Hamamelis virginiana , is evaluated by analysis of weevil life tables and abundance estimates in three years with markedly different magnitudes of fruit production.
2. Fruit production of marked Hamamelis individuals averaged 336 m^-2 in 1978, increased three- to four-fold in 1979, and declined again in 1980. More individuals fruited in 1979 than in the other two years.
3. The early larval stage of P.hamamelidis incurred the greatest mortality, with 42–58% dying from often undeterminable causes. Losses in the egg stage ranged from 22% to 31%. Three parasitoid species each accounted for minor mortality. Generation survival was similar in all three years, ranging from 21% to 28%.
4. The percentage of Hamamelis fruit crops infested by P.hamamelidis was high in 1978, averaging 76%, but was much lower in 1979, the year of abundant fruit. In 1980, when fruit were less abundant again, infestation was nearly complete. Egg densities on fruits were lower in 1979 than in the other two years.
5. The fluctuating fruit crops of Hamamelis are responsible for limitation of P.hamamelidis numbers during poor fruiting years. The occasional highly productive fruiting year results in satiation of weevil populations and concomitant seed escape by Hamamelis . Mortality factors appear less important in influencing weevil population dynamics.     

The spatio-temporal distribution dynamics of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Coleoptera: Curculionidae), and its larval parasitoids in canola in western Canada

Distribution patterns of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), and its larval parasitoids were investigated in commercial fields of spring canola (Brassica rapa L. and Brassica napus L.) in southern Alberta, Canada, from 2002 to 2004 in relation to developmental stages of its host plants. Adult weevils invaded fields along one or more fronts when crops were in bud to early flower. Significant clustering of adults along field edges in early stages of invasion was followed by more homogeneous distributions as canola reached the mid to late flowering and pod enlargement stages. Larval weevil distributions, as indicated by exit holes in siliques at the end of the season, were often aligned spatially with adult distributions, but they did not coincide in all regions of the fields. The primary ectoparasitoid species attacking weevil larvae comprised Necremnus tidius (Walker) (Hymenoptera: Eulophidae), and Trichomalus lucidus (Walker), Chlorocytus sp., and Pteromalus sp. (Hymenoptera: Pteromalidae). Parasitism rates increased from 0.1 to 5.0% over the three years of study. Parasitoid distributions were often, but not consistently, spatially associated with high densities of C. obstrictus larvae. Lack of close spatial alignment of parasitoids and their hosts probably reflects low parasitoid numbers in comparison with an abundant resource of weevil larvae, and a lack of co-evolutionary history between host and parasitoids. Some parasitoids invaded fields early in host plant development, at the same time that weevils invaded. Unfortunately the synchronous invasions of host and parasitoids indicate that insecticidal applications to reduce adult weevil infestations may be detrimental to these beneficial species.     

Susceptibility of strawberry cultivars to the vine weevil Otiorhynchus sulcatus (Coleoptera: Curculionidae)

Abstract 1 The feeding preference of vine weevil, Otiorhynchus sulcatus (Fabricius), adults for foliage from 21 commercial cultivars of strawberries is investigated using binary choice tests with leaf disks, using ‘Honeoye’ as a standard against which all other cultivars are compared. ‘Delmarvel’, ‘Idea’, ‘Lester’, ‘Primetime’ and ‘Seneca’ are not preferred. 2 Variation in leaf nitrogen content is correlated with feeding preference, but does not explain all the variation, because outliers exist for both preferred and nonpreferred cultivars. 3 Removal of leaf hairs with adhesive tape permits their role in deterrence to be evaluated. Eight of the 21 cultivars have deterrent leaf hairs. Paradoxically, some highly preferred cultivars (e.g. ‘Latestar’ and ‘Tristar’) have deterrent leaf hairs, and four of the five nonpreferred cultivars lack significantly deterrent leaf hairs. 4 The 21 tested cultivars do not differ in their suitability for vine weevil larval development. 5 Differences in cultivar susceptibility to vine weevil in the field may involve interactions between the palatability and nutritional value of foliage, which influence fecundity and egg placement, and the tolerance of strawberry plants to larval feeding, determined by root biomass. The nonpreference traits found in the foliage of commercial cultivars of strawberry are present by chance. Accordingly, further selective breeding to enhance strawberry varietal tolerance to vine weevils may be possible.     

Root disturbance of common ash, Fraxinus excelsior (Oleaceae), leads to reduced foliar toughness and increased feeding by a folivorous weevil, Stereonychus fraxini (Coleoptera, Curculionidae)

Abstract.

• 1 Bioassays were carried out to examine differences in the feeding of a folivorous weevil, Stereonychus fraxini De Geer, on leaves from ash saplings with undamaged roots, and those with damaged roots. Beetles ate significantly more of the leaves of root-damaged saplings in a choice experiment.
• 2 A separate study of the effect of root damage on leaf toughness was carried out on a second group of ash saplings. Saplings with damaged roots had less tough leaves than control saplings. Decreased leaf toughness in hypothesized as a mechanism to explain the preference of weevils for leaves from damaged trees.
• 3 Both chemical and physical changes may occur in the tissues of ash trees in response to environmental stress such as drought and root damage.
• 4 Root damage caused by agricultural disturbance is hypothesized as a mechanism making mature ash trees in hedgerow ecosystems more susceptible to insect herbivores.