Attractant for the sugar-beet weevil Conorrhynchus (Cleonus) mendicus (Col.: Curculionidae)

Abstract:  Traps baited with a 1 : 1 : 1 mixture of Grandlure I [ cis -1-methyl-2-(1-methylenethenyl)-cyclobutaneethanol], Grandlure II [( Z )-2-ochtoden-1-ol; ( Z )-2-(3,3-dimethylcyclohexylidene)ethanol] and Grandlure III–IV [( Z )- and ( E )-2-ochtodenal; ( Z )- and ( E )-(3,3-dimethyl)cyclohexylidene)acetaldehyde] caught significantly more Conorrhynchus (Cleonus) mendicus Germar (Col.: Curculionidae) weevils than traps without bait. Later tests revealed that only Grandlure III–IV was responsible for attractivity. Both sexes were attracted according to a random sample of captures. C. mendicus appeared to be very similar in its responses to the synthetic aggregation attractant as the closely related Bothynoderes (Cleonus) punctiventris (Germar), in which species, the attraction to Grandluree III–IV has recently been published. Doses from 500 to 5000  μ g of Grandlure III–IV on rubber dispensers performed satisfactorily in monitoring trials and can be recommended for use in practical trapping applications for C. mendicus .     

Grandisol as an attractant for the sugar beet pest Bothynoderes affinis and data on other Lixinae species

As a result of field tests in Bulgaria and Hungary, cis‐2‐isopropenyl‐l‐methylcyclobutane ethanol (racemic grandisol) is reported for the first time as an attractant for Bothynoderes affinis (Schrank) (Coleoptera: Curculionidae, Lixinae), a member of the pest weevil complex of sugar beet. Dose–response experiments in the field using Csalomon TAL (modified pitfall) traps (Plant Protection Institute, CAR HAS, Budapest, Hungary) showed that catches of B. affinis adults increased with increasing attractant dose. In a subsequent experiment studying the effect of trap color (white, blue, yellow, fluorescent yellow, and transparent) all traps with the lure caught more than non‐baited control traps, and the highest number of adults was recorded in transparent and yellow baited traps. Trap color had a significant effect on the number of B. affinis females captured. Transparent TAL traps baited with 1–10 mg grandisol applied on rubber dispensers are recommended for the detection and monitoring of B. affinis. In addition to the target species, 17 other Lixinae species were captured during the field experiments, demonstrating for the first time the possible role of grandisol in the chemical communication systems of some of these species. A second locality of Lixus punctiventris Boheman (Lixinae, Lixini) in Bulgaria is reported. TAL traps baited with grandisol might be a useful tool for surveying Lixinae diversity in different biotopes.     

Restricted host range of the weevil Aubeonymus mariaefranciscae, a new sugar-beet pest

The extent of feeding, fecundity and fertility of a new sugar beet pest, Aubeonymus mariaefranciscae Roudier (Coleoptera: Curculionidae), on a range of plants from different families was determined. We have found that the adult weevils were only able to feed and oviposit on two closely related cultivated plants, beet and sugar beet, both subspecies of Beta vulgaris L., suggesting a restricted host range for this curculionid. None of 16 secondary metabolites (widely distributed among plants, and representative of different chemical groups), nor any of 19 non-host extracts from 13 different families, deterred the adults of this curculionid from feeding on sugar beet. We found a phagostimulatory effect when beet and sugar beet homogenates from various plant tissues were supplied to adult weevils on weeds that they do not feed on. Conversely, no effect was observed when sucrose was provided. These findings suggest that host selection by A. mariaefranciscae adults is due to the presence of an undetermined phagostimulant compound(s) in beet and sugar beet, instead of the recognition of deterrent substances among the non-host plants.     

Field trapping of Metamasius hemipterus with synthetic aggregation pheromone

The five synthetic pheromone components of the West Indian sugarcane borer (WISB), Metamasius hemipterus (L.) (Coleoptera, Curculionidae) were tested in the field. The combination of sugarcane (SC) and the major pheromone compound, 4-methyl-5-nonanol (1) was attractive. However, the addition of 2-methyl-4-heptanol (2) or 2-methyl-4-octanol (3) was required to reach high catch levels while 5-nonanol (4) or 3-hydroxy-4-methyl-5-nonanone (5) did not enhance WISB attraction. The redundancy phenomenon, here reported for the first time in rhynchophorinous species, was observed between compounds 2 and 3. SC +1 +3 was more attractive than living male baits, however, the sex-ratio of the catches was equivalent between both treatments. The sex-ratio of catches was affected by the qualitative composition of the pheromone formulation. Compound 3 had a sexual role, attracting more females while 5 seemed to play an aggregation role, luring both sexes in the same proportion.     

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

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.     

Different bioassays for investigating orientation responses of the banana weevil, Cosmopolites sordidus, show additive effects of host plant volatiles and a synthetic male-produced aggregation pheromone

Abstract Three different bioassay methods to investigate the orientation behaviour of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), to host plant volatiles and a synthetic pheromone (cosmolure+) were compared. A locomotion compensator was used to separately record walking tracks in response to three odour sources. The data show that C. sordidus uses odour‐conditioned anemotaxis in its orientation to the odour sources tested. Of the two olfactometers tested, a dual port olfactometer using a continuous airflow showed stronger discrimination by C. sordidus to the different odours compared with a double pitfall olfactometer. The results of all three bioassays indicate that C. sordidus responds in an additive way to the combination of fermentation plant volatiles and the synthetic pheromone.     

Regulation of vitellogenin synthesis and uptake in the boll weevil, Anthonomus grandis

Abstract. Hormonal factors influencing reproductive development were examined in adult boll weevils, Anthonomus grandis (Boheman) (Coleoptera: Curculionidae). Long-day, high-temperature rearing conditions promote reproduction whereas short-day, low-temperature conditions do not. Implants of corpora allata (CA), brains, or brains plus retrocerebral complexes taken from long-day donors, or hormone analogue treatments were used to examine onset of vitellogenin synthesis and uptake in decapitated bodies of adult weevils reared in short-day, low-temperature conditions. Weevils decapitated within 2 days after eclosion and reared in short-day, low-temperature conditions never initiated vitellogenin production or ovarian development. Females and males decapitated on day 2 showed haemolymph vitellogenin within 5 days following treatment with Juvenile Hormone (JH) analogue or implantation of CA, but not after implantation of brain alone or implantation of muscle (sham). Uptake of vitellogenin into the oocytes did not occur unless both JH analogue and brain were given as replacement therapy. These experiments indicated that JH is necessary and sufficient to stimulate vitellogenin synthesis in this species but that a brain factor must be present for vitellogenin uptake.     

Aggregation pheromone of the agave weevil, Scyphophorus acupunctatus

The agave weevil, Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae), is the most important insect pest of wild and cultivated agaves in the world. Combined gas chromatography‐electroantennography (GC‐EAD) analysis of male volatile extracts showed that four peaks elicited antennal responses from males and females. The peaks were identified by GC‐mass spectrometry (GC‐MS) as 2‐methyl‐4‐heptanol (1), 2‐methyl‐4‐octanol (2), 2‐methyl‐4‐heptanone (3), and 2‐methyl‐4‐octanone (4). Electroantennogram (EAG) recordings of both sexes to 0.01‐, 0.1‐, 1‐, and 10‐µg stimulus load of synthetic compounds showed that the dose of the tested compounds and weevil sex significantly influenced the antennal response of S. acupunctatus. However, there was no sexual dimorphism in the antennal responses to the four synthetic compounds evaluated because the EAG profiles revealed no interaction between doses by sex. Antennae of S. acupunctatus were most sensitive to compounds 2 and 4, reaching the threshold at a 0.01‐µg stimulus load. Weevil antennae were less sensitive to compounds 1 and 3, and the threshold response to these compounds was 0.1 µg. Behavioural evaluation of the synthetic compounds showed them to be attractive to both males and females in a Y‐tube olfactometer. Field experiments confirmed the laboratory results, showing that all components, singly or in blends, were attractive to the weevils. In general, traps baited with the quaternary blend of compounds 1–4 captured significantly more weevils than traps baited with males. However, compounds 3 and 4 were sufficient to obtain captures equivalent to those by the quaternary blend. The potential use of the aggregation pheromone in the development of a mass‐trapping programme as a viable pest management alternative for S. acupunctatus is discussed.     

Semiochemical attractants for the beech leaf‐mining weevil,Orchestes fagi

The beech leaf‐mining weevil, Orchestes fagi L. (Curculionidae: Curculioninae: Rhamphini), a pest of European beech, Fagus sylvatica L. (Fagaceae), was recently discovered infesting American beech, Fagus grandifolia Ehrh., in Nova Scotia, Canada. Adult O. fagi feed on both young and mature leaves of beech as well as on other species (e.g., raspberry, Rubus spp.), but oviposition and larval feeding are restricted to beech. Females oviposit in young developing beech leaves at the time of bud burst. We characterized volatiles emitted from buds, leaves, and sapwood of American beech and examined their potential as attractants alone or when combined with other weevil pheromones for O. fagi. We predicted that adults would be attracted to volatiles emitted from beech leaves, especially those emitted from bursting beech buds. Gas chromatography/mass spectrometry (GC/MS) analyses of volatiles collected from buds at pre‐ and post‐budburst identified two diterpene hydrocarbons, 9‐geranyl‐p‐cymene ( 1 ) and 9‐geranyl‐α‐terpinene ( 2a ), that were emitted in large amounts at the time of bud burst. Compound 1 significantly increased mean catch of males and total O. fagi (but not females) on sticky traps compared with unbaited controls. Y‐tube bioassays confirmed attraction of male O. fagi to bursting beech buds and compound 1 . Attraction of male O. fagi to 1 , emitted in large quantities from American beech, is likely adaptive because both oviposition and mating of O. fagi coincide with budburst. Our data suggest that traps baited with 1 may be useful for monitoring the spread of O. fagi in North America.     

Insect diets as mixtures: optimization for a polyphagous weevil

Development or improvement of artificial insect diets can be tedious, convoluted and often under-appreciated. Using n-dimensional mixture designs, we identified a set of response-optimized meridic diets that contain fewer ingredients than the current commercial diet for Diaprepes abbreviatus, a polyphagous weevil pest of the Caribbean and southern U.S. A diet blend optimized to produce maximum adult weight was predicted to produce adult D. abbreviatus that weigh 28% more compared with adults reared on the standard commercial diet. Diet blends that produced greater individual adult weights resulted in lower survival compared with those blends that yielded adults of more modest proportions. In contrast, a simplified high cottonseed meal blend produced smaller adults more similar to field-collected individuals, and produced the greatest number of adults and the greatest biomass at relatively low cost compared with diets that yielded adult weevils of greater weight. We think that many insect-rearing programs would benefit from application of mixture design methods to situations where diet optimization is desired for researcher-selected criteria. This approach is broadly applicable to any problem that can be conceptualized as a mixture problem.     

Carvone and less volatile analogues as repellent and deterrent antifeedants against the pine weevil, Hylobius abietis

Abstract:  The monoterpenoid carvone ( 1 ) has been shown to have strong antifeedant effects on Hylobius spp. However, because of the high volatility of carvone, long-time protection of conifer seedlings in the field using this compound has not been possible. We demonstrate, in several bioassay steps, that less-volatile, heavier analogues retain their pre-ingestive feeding inhibition activity in the large pine weevil, Hylobius abietis (L.) for a longer time. The first step in the evaluation of the biological activity of 12 carvone analogues was a micro-assay, a choice test lasting 4 h. Compounds active at 100 nmol/cm² were further dose–response tested to give the effective dose needed to inhibit feeding by 50% (ED50). Of the 14 compounds tested, including both carvone enantiomers, seven heavier analogues were active at low doses (had low ED50 values). As expected from their lower vapour pressure compared with carvone, the heavier analogues proved more resistant to evaporation before testing. Thus, whereas the effect of 8-hydroxy- p -menth-en-6-one 4 declined after 2 days, some of the compounds with high molar masses, such as the alkylhydroxymenthenones 6 and 8 , retained a stable activity for 4 days. The retained activity at 4 days was strongly correlated to molecular mass and boiling point. When tested on natural material (host Pinus sylvestris L. twig sections for 48 h), the heavier analogues showed a rather low activity. Probably, the activity of the more volatile compound carvone ( 1 ) is due to a repellent effect (olfactory mode) rather than the deterrent effects (gustatory mode) of the heavier compounds. In agreement with the relatively low activity on twigs in the laboratory, the hydroxymenthenone 4 was not active in the field when tested for 2 months as a 1 : 9 mixture with a polar wax.     

Isolation and fluorescence studies on a lipophorin from the weevil diaprepes abbreviatus

Lipophorin was isolated from larvae of a root weevil, Diaprepes abbreviatus (Coleoptera: Curculionidae), using density gradient ultracentrifugation. D. abbreviatus lipophorin contained two apoproteins, apolipophorin-I (M_r = 226,000) and apolipophorin-II (M_r = 72,100) and had a density of 1.08. Relative to other larval lipophorins, D. abbreviatus lipophorin contained little cysteine (determined as cysteic acid) and methionine. Fluorescence spectroscopy of intrinsic tyrosine and tryptophan residues excited at 290 nm revealed a single broad emission peak at 330 nm. Upon denaturing and delipidating lipophorin in guanidine HCl, this peak resolved into two peaks with maxima at 305 and 350 nm. Excitation spectra suggested that the two peaks were due to tyrosine and tryptophan, respectively. Fluorescence quenching agents, iodide and acrylamide, were used to determine accessibility of tyrosine and tryptophan residues to the aqueous environment. Iodide, a polar quenching agent, did not quench fluorescent emission from native lipophorin; quenching by iodide increased to moderate levels when lipophorin was denatured in guanidine HCl. Acrylamide quenched the fluorescence of native lipophorin moderately and very efficiently quenched fluorescence of denatured lipophorin. No difference was observed between fluorescence quenching of denatured vs. denatured and delipidated lipophorin by either iodide or acrylamide.     

Spring behavioral patterns of the apple blossom weevil

Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.     

Development of a semiochemical-based trapping method for the New Guinea sugarcane weevil, Rhabdoscelus obscurus in Guam

Abstract:  Aggregation pheromone of the Australian population of New Guinea sugarcane weevil, Rhabdoscelus obscurus (Boisduval), in conjunction with other semiochemicals, was used to develop an efficient trapping method for the weevil population in Guam. In a field experiment at Yigo, plastic bucket traps baited with the lure of the Australian R. obscurus population in combination with ethyl acetate and cut sugarcane captured significantly more weevils than traps baited with pheromone + ethyl acetate, pheromone + sugarcane or individual lure components alone. Traps baited with various semiochemical-based lures and treated with insecticide captured significantly greater numbers of weevils than those not treated with insecticide. Traps baited with cut sugarcane caught significantly more weevils than those without sugarcane. Semiochemical-based trapping in weevil management has potential either in mass trapping or as part of an integrated pest management (IPM) programme. Based on the present findings, a future line of work for the control of this weevil is proposed.     

Distribution, timing of attack, and oviposition of the banana weevil, Cosmopolites sordidus, on banana crop residues in Uganda

Crop sanitation (removal and chopping of residue corms and pseudostems following plant harvest) has been recommended as a ‘best bet’ means of reducing banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), populations. However, it has been unclear when such practices should be carried out and what types of residues should be destroyed. Therefore, trials were conducted in Uganda to determine C. sordidus distribution, timing of attack, and oviposition on crop residues and growing plants. Assessments were performed in on‐station trials on different aged standing and prostrate residues by destructive sampling. Similar data were collected from farmers’ fields maintained at low, moderate, and high levels of sanitation. In the on‐station trial, oviposition occurred on up to 120‐day‐old residues, although most occurred within 30 days of harvest. In a second on‐station experiment, oviposition on standing residues was not significantly affected by residue age. By contrast, oviposition on prostrate residues was two times higher on 4‐week‐old than on 2‐week‐old residues, while the number of larvae on 8‐week‐old residues was three times higher than on 2‐week‐old residues. The number of adults was twice as high on 16‐week‐old residues as that on 2‐week‐old residues for both prostrate and standing residues. Farmers’ fields maintained at high sanitation had 50% fewer eggs per residue than farms with low sanitation levels. In general, the number of immatures per residue was 50% higher on banana corms than on pseudostems. Numbers of larvae per residue were three times more abundant at low than at high sanitation levels. Residues in fields with high sanitation supported 50% fewer adults than residues in low sanitation fields. The results suggest that removal and splitting of corms after harvest is effective and practical in destroying immature growth stages of the pest and that such practices should be carried out soon after harvest.     

Isolation and characterization of microsatellite loci in the Galápagos Opuntia weevil Gerstaeckeria galapagoensis (Coleoptera,Curculionidae)

Five microsatellite loci were isolated from the Galápagos weevil Gerstaeckeria galapagoensis. Polymorphism ranged from two to seven alleles, and observed and expected heterozygosities ranged from 0.286 to 0.917 and 0.254 to 0.683, respectively.     

Biochemical characterization of a strictly specific beta-galactosidase from the digestive juice of the palm weevil Rhynchophorus palmarum larvae

A beta‐galactosidase from the digestive juice of the palm weevil Rhynchophorus palmarum L. larvae was purified by chromatography on ion exchange, gel filtration, and hydrophobic interaction columns. The preparation was shown to be homogeneous on polyacrylamide gel. Beta‐galactosidase was a monomeric protein with a molecular weight of 62 kDa based on its mobility in sodium dodecyl sulfate–polyacrylamide gel electrophoresis and 60 kDa based on gel filtration. Maximal enzyme activity occurred at 55°C and pH 5.0. The purified beta‐galactosidase was stable at 37°C and its pH stability was in the range of 4.6–6.0. Beta‐galactosidase was highly specific for the beta‐d ‐galactosyl residue and beta‐(1‐4) linkage. The catalytic efficiency (V_max/K_m) values for p‐nitrophenyl‐beta‐d ‐galactopyranoside, beta‐d ‐galactosyl(1‐4)‐d ‐glucose (lactose), beta‐d ‐galactosyl(1‐4)‐d ‐galactose and beta‐d ‐galactosyl(1‐4)‐beta‐d ‐galactosyl(1‐4)‐d ‐glucose were, respectively, 72.95, 10.97, 20.74 and 12.73. 5,5‐Dithio‐bis(2‐nitrobenzoate) and sodium dodecyl sulfate inhibited completely the beta‐galactosidase activity. The enzyme was capable of catalyzing transgalactosylation reactions. The yield of galactosylation of 2‐phenylethanol (43%), catalyzed by the beta‐galactosidase in the presence of lactose as galactosyl donor, is higher than those reported previously with conventional sources of beta‐galactosidases. In addition, the optimum pH is different for the hydrolysis (pH 5.0) and transgalactosylation reactions (pH 6.0).     

Cold hardiness and overwintering survival of the cabbage seedpod weevil,Ceutorhynchus obstrictus

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is a serious pest of brassicaceous crops in temperate regions and a chronic member of the pest complex that attacks canola in Canada. We conducted several laboratory and field experiments to quantify winter survival and its role in the population dynamics of this insect. We estimated the supercooling point of the weevil at ?7 °C and its survival over 8 weeks decreased significantly at ?5 °C relative to 5 °C, but extending the overwintering period at 5 °C to 18.5 weeks had no effect on mortality. Cumulative sub‐freezing degrees estimated from air temperature, and especially from soil temperature, were highly correlated with weevil survival. Our linear regression model predicted poor survival of the weevils in typical winters in northern Alberta. Our results indicate that if milder winters prevail, as predicted by global warming, there is potential for the weevils to establish and become a serious pest in northern canola‐growing regions of Canada.     

Partial characterization of the proteolytic enzymes in the gut of the banana weevil, Cosmopolites sordidus, and effects of soybean Kunitz trypsin inhibitor on larval performance

The proteolytic enzymes in the gut of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), have been characterized. Both larvae and adults rely on a complex proteolytic system based on at least cathepsin D‐, cathepsin B‐, trypsin‐, chymotrypsin‐, leucine aminopeptidase‐, carboxypeptidase A‐, and carboxypeptidase B‐like activities. All endoproteolytic activities were higher in the anterior section of the gut, whereas the exopeptidases were evenly distributed in the anterior and middle sections, and almost no activity was detected in the posterior section. Gelatin‐containing gels confirmed the spatial organization of the proteolytic digestive process. According to this proteolytic profile, the STI (soybean Kunitz trypsin inhibitor) was tested in vivo to establish its potential as a resistance factor against C. sordidus. Newly hatched larvae fed on diets containing 0.2% (w/w) STI experience lower survival rates and display significant reductions in larval growth. Biochemical analysis carried out on guts of larvae reared on STI‐treated diet showed a reduction of trypsin‐like activity compared to that from larvae fed on control diet. This decrease was compensated with an induction of cathepsin B, whereas cathepsin D, chymotrypsin, and leucine aminopeptidase were not affected. These results are discussed as a basis for selecting appropriate inhibitors to obtain transgenic banana and plantain plants with enhanced resistance to this pest.