Otiorhynchus Sulcatus Research Articles

Complex patterns from simple decisions: the emergence of behaviours in Otiorhynchus sulcatus F.

Abstract 1 Filming the movement of individual adult Otiorhynchus sulcatus in a stimulus‐free arena allows the frequency distribution of turning angles to be obtained. Turns are predominantly anti‐clockwise and the distribution is dominated by three preferred angles (approximately 50, 130 and 190°).2 The implications of these results are explored through deterministic and stochastic random walk models of fixed step‐length. Use of each of these turning angles results in different trajectories, potentially representing different search patterns.3 The introduction of stochastic variation in the turning angles alters the trajectories and, for the 50° turning angle, results in an approximation to published descriptions of spiral and circular search patterns for other insects.4 This single parameter random walk model is compared with previously published models and it is postulated that, for O. sulcatus, the selection of a turning angle is sufficient to provide a rich repertoire of spatial trajectories.

A technique for continuous mass rearing of the black vine weevil, Otiorhynchus sulcatus

The black vine weevil, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae) is a univoltine, polyphagous insect that is a nocuous pest of field and container grown ornamentals as well as small fruit crops world-wide (Moorhouse et al., 1992). In the USA, the environmental horticulture industry (floriculture and nursery crops) is the third largest value crop behind corn and soybeans (USDA fact sheets 2001, http://www.nass.usda.gov). Otiorhynchus sulcatus is thought to have a northern European origin and was first recorded in North America in 1835 (Smith, 1932). Oviposition occurs at night with eggs being either dropped on the soil surface or inserted into crevices on plants (Smith, 1932). Early instars begin by feeding on small roots while the later instars feed on larger roots, especially on the phloem and cambium tissues near the soil surface (La Lone & Clarke, 1981). Adults are nocturnal and mainly cause aesthetic damage to plants by notching the leaves. Adults are parthenogenic, so a single individual left unchecked can result in the infestation of an entire nursery. Because of the biology of O. sulcatus , the collection of larvae and adults from the field is very tedious and often requires countless hours of digging through field soil, container-grown plants or searching for adults after dark. Indeed, many chemical and biological control companies developing products for O. sulcatus larval control still rely on searching through infested plant material in order to gather the needed larvae for efficacy studies. Although an artificial diet initially developed by Shorey & Hale (1965) as modified by Shanks & Finnigan (1973) and Shanks (1980) (hereafter referred to as the ‘standard diet’) sustains larvae and is commercially available, there has been no documented technique for continuous mass rearing of O. sulcatus . Studies of weevil biology as well as the development of control strategies require a large, uniform, and predictable supply of insects of all life stages throughout the year. When considering field or potted plants for use in control efficacy or host plant resistant studies, other researchers have often found it useful to store insect eggs for several weeks for subsequent use; many thousands to millions of eggs were needed. The stockpiling of eggs for future use has been necessary with other reared species of Coleoptera (Branson, 1978; Fisher & Edwards, 2002). The egg hatch and viability of the strawberry root weevil, Otiorhynchus ovatus L. were not significantly reduced when it was stored for up to 4 weeks at 4 ° C (Fisher & Edwards, 2002). We have developed a technique for continuous mass rearing of O. sulcatus in the laboratory using a meridic diet. Since small changes in diet composition can often lead to dramatic changes in larval survival and growth, experiments were also performed to determine if O. sulcatus larval survival and development were increased on the improved diet described here, compared to the standard diet. Additionally, we determined if O. sulcatus eggs could be stored for up to 4 weeks at 4 ° C without significant reductions in larval survival and development.

Natural Occurrence of Entomopathogens in Pacific Northwest Nursery Soils and Their Virulence to the Black Vine Weevil,Otiorhynchus sulcatus(F.) (Coleoptera: Curculionidae)

Abstract The black vine weevil Otiorhynchus sulcatus (F.) is the primary insect pest of field and container-grown woody ornamentals in the Pacific Northwest (PNW). These studies were conducted to determine the natural occurrence of soil-borne entomopathogens in PNW nursery soils and determine their virulence to black vine weevil. Soil samples were collected July–September of 2002 from field-grown woody ornamental nursery stock in Oregon, Washington, and Idaho. Sample collection in each state took place in the major nursery production areas. A total of 280 samples was collected (Oregon, 170; Washington, 50; Idaho, 60). Entomopathogens were isolated using insect baiting (nematodes and fungi) as well as semiselective media (fungi). Bacillus thuringiensis Berliner was isolated through sodium acetate selection. Soil-borne entomopathogenic fungi occur widely throughout the major nursery production areas in the PNW. The entomopathogenic fungi Metarhizium anisopliae (Metchnikoff) Sorokin, Beauveria bassiana (Bals...

Behavioural responses of the vine weevil, Otiorhynchus sulcatus, to semiochemicals from conspecifics, Otiorhynchus salicicola, and host plants

AbstractThe vine weevil Otiorhynchus sulcatus is a parthenogenetic reproducing species which forages for suitable host plants at night, but is found congregated in dark places during the day. Frass of this weevil species is suspected to contain attractive compounds that are host‐plant related. Using a still‐air olfactometer, we tested adult vine weevils at night for their behavioural response to odours from conspecifics, feeding on a mixture of spindle tree (Euonymus fortunei) and yew (Taxus baccata), and to a sexually reproducing related species (Otiorhynchus salicicola), feeding on a mixture of ivy (Hedera helix) and cherry laurel (Prunus laurocerasus). Their attraction to conspecifics and O. salicicola appeared to be related to frass production. Freshly collected frass from O. sulcatus and from O. salicicola males and females was attractive. Prunus laurocerasus and H. helix have not been observed to be hosts of the vine weevil in the field. However, our tests showed that the vine weevil was attracted to mechanically damaged leaves of both plant species, whereas undamaged leaves were not attractive. Only undamaged young unfolding leaves of H. helix were also attractive. The attraction to odours from mechanically damaged host and non‐host plants suggested the involvement of compounds that are commonly found in many plant species. The involvement of plant compounds and/or aggregation pheromones in attraction to frass of the vine weevil and frass of the related weevil species O. salicicola is discussed.

Superior efficacy observed in entomopathogenic nematodes applied in infected-host cadavers compared with application in aqueous suspension

Two greenhouse experiments were conducted to compare the efficacy of entomopathogenic nematodes applied in aqueous suspensions with application in infected cadavers. One experiment targeted the diaprepes root weevil Diaprepes abbreviatus with Heterorhabditis indica and the other targeted the black vine weevil Otiorhynchus sulcatus with H. bacteriophora. Entomopathogenic nematode application in infected cadavers were more effective than nematode application in aqueous suspensions in all cases. The increased efficacy observed in the cadaver applications may have been due to the additional physiological stress in the aqueous application (during temporary storage in water or upon application). Superior efficacy in the cadaver application might also have been due to compounds in the infected host cadaver that can enhance nematode infectivity.

COMPARING ESTIMATION PROCEDURES FOR DOSE-RESPONSE FUNCTIONS

The dose-response design is often used in agricultural research when it is necessary to measure a biological response at various levels of an experimental factor. This type of problem is common in chemical and pesticide research, however, it can also occur in other disciplines such as plant, animal, soil, and environmental sciences. While the analysis of dose-response data usually involves fitting a regression curve, the primary objective often centers on the estimation of dose related percentiles such as the LD50 or LC50. These measures are useful for comparing the relative efficacy of various treatments, however, the estimation of the specified percentiles is not always straightforward. Traditional methodology has relied on inverted solutions or asymptotic theory for statistical inference. More recently, computer intensive methods have been used to model dose-response relationships and can be more appropriate than traditional methods in some situations. This paper examines both the traditional and modem approaches to estimating doseresponse functions as they apply to binomial data. The techniques will be demonstrated using mortality data collected on black vine weevil eggs exposed to an organic pesticide treatment.

Evaluation of Entomopathogenic Nematodes to Manage Root Weevil Larvae in Washington State Cranberry, Strawberry, and Red Raspberry

The ability of entomopathogenic nematodes to reduce abundance of subterranean root weevils was evaluated in three small fruit crops of Washington State. In cranberry, the entomopathogenic nematodes Steinernema carpocapsae (Weiser) and S. glaseri Steiner applied at 30 IJ (infective juveniles) per square centimeter reduced abundance of black vine weevil, Otiorhynchus sulcatus (F.), by 96 or 100% respectively compared with the untreated control. According to a waxmoth [Galleria mellonella (L.)] bait bioassay, S. carpocapsae persisted at higher levels than S. glaseri (0.48 versus 0.04% infested waxmoth per applied infective juvenile at 30 d after treatment) and for a longer interval (at least 60 d after treatment), but neither species dispersed beyond the treatment plots. At one of two strawberry sites, S. carpocapsae and Heterorhabditis marelatus Liu OH10 significantly reduced the abundance of black vine weevil (all stages) and pupal strawberry root weevil, O. ovatus (L.), compared with the untreated control. The same treatments were applied at the other site, but only pupal black vine weevils were significantly affected. Neither S. carpocapsae nor H. bacteriophora Poinar significantly reduced the abundance of black vine weevil in two trials conducted in red raspberry. Entomopathogenic nematodes were recovered from larval waxmoth Galleria mellonella baits placed on soil from the red raspberry sites 6 wk after treatment. Efficacy of entomopathogenic nematodes in all trials was likely most limited by cool soil temperatures that are typical to Pacific Northwest small fruit crops during spring when root weevils are in late larval and pupal stages, but soil structure and crop characteristics, particularly dense strawberry foliage and large crowns, were also important.

Olfactory responses of the vine weevil, Otiorhynchus sulcatus, to tree odours

Abstract A Y‐tube olfactometer and a still‐air olfactometer were developed to determine the attractiveness of several host plants for the vine weevil (Otiorhynchus sulcatus (F.); Coleoptera: Curculionidae). Odours of weevil‐damaged yew (Taxus baccata) and spindle trees (Euonymus fortunei) are attractive to the vine weevil, but Rhododendron and strawberry (Fragaria × ananassa) are not. Undamaged Euonymus is attractive to the weevils in springtime but not in late summer. When clean air or undamaged Euonymus is the alternative, weevils strongly prefer weevil‐damaged Euonymus foliage, and this preference is retained throughout the year. Hence, plant damage plays a role in attraction of the vine weevil. In contrast to the permanent attractiveness of weevil‐damaged Euonymus, mechanically damaged plants gradually lose the attractiveness that they have early in the growing season. This suggests that emission of volatiles, produced by the plants in response to weevil damage, is important for attraction of the weevils because the weevils may use these plant odours to find suitable food plants throughout the season. Apart from weevil‐damage‐related plant volatiles, green leaf volatiles must also play a significant role, as indicated by the fact that weevils prefer: early season, undamaged Euonymus over clean air; early season, mechanically damaged Euonymus over undamaged Euonymus; and, throughout the season, had no preference when mechanically damaged Euonymus is tested against weevil‐damaged Euonymus. Thus, monitoring traps may be developed by the use of green leaf volatiles and/or herbivore‐induced volatiles, as attractants.

Acoustic Detection of Black Vine Weevil, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae) Larval Infestations in Nursery Containers

Abstract Acoustic detection systems have been developed to locate and target hidden infestations of root weevil larvae in container-grown nursery crops. Tests were conducted in laboratory and field environments with natural and artificial infestations of Otiorhynchus sulcatus (Fabricius) in containers with different nursery plants to determine whether the larvae were large enough for acoustic detection during late fall when scouting for infestation often occurs at commercial nurseries in Oregon. The rootballs of tested plants were examined to verify the presence or absence of larvae. All of the containers rated at high likelihood of infestation contained O. sulcatus larvae (29% of those tested). No larvae were found in any containers rated at low likelihood of infestation (20%). Sporadic sounds were detected but failed to exhibit periodicity suggestive of infestation in 51% of the containers (rated at medium likelihood). Fifty seven percent of these medium-rated containers were infested. Experience with the use of the acoustic system in field environments suggested improvements in user-friendliness and robustness that could improve its utility for early detection and targeting applications in commercial nurseries.

Olfactory antennal responses of the vine weevil Otiorhynchus sulcatus to plant volatiles

AbstractElectroantennograms (EAGs) were recorded from the vine weevil, Otiorhynchus sulcatus F. (Coleoptera: Curculionidae) to a broad range of volatile plant compounds. The response profile is restricted to a small number of volatiles that evoke substantial EAGs. Large EAG responses were particularly found among green leaf volatiles (GLV) such as (E)‐2‐hexenol‐1, (Z)‐3‐hexenol‐1, hexanol‐1, hexanal, and heptanal. Other plant volatiles eliciting responses in the weevils' antenna are 2,5‐dimethylpyrazine, hexylamine, benzylalcohol, 1,2‐dimethoxybenzene, o‐cresol, myrtenol, 3‐methylcyclohexanol, γ‐hexalactone, and γ‐heptalactone. EAG responses to terpenes were generally weak. Many of the monoterpenes are characteristic for the odour of conifers, a group of plants which tend to be avoided by adult vine weevils. The EAG response to several GLV and benzene derivatives in three geographically distinct populations of the vine weevil differed, suggesting between‐population variation in receptor sensitivities for several compounds under test. The GLV‐composition of the odour profile of potential food plants may be an important criterion for a polyphagous insect like the vine weevil to be used in host‐plant selection, since compounds in this odour group dominate so strongly the EAG response profile. In multiple food‐choice situations the weevils are known to prefer certain plant species and we hypothesize that they combine GLV information with that of more specific plant volatiles, thereby promoting attraction or avoidance.

The effect of the Cowpea trypspin inhibitor in strawberry on damage by vine weevil under field conditions

SummaryTransgenic strawberry lines constitutively expressing the Cowpea trypsin inhibitor (CpTi) were examined under field conditions to determine if this gene offered protection against the feeding of vine weevil (Otiorhynchus sulcatus F.). Data are presented on plant performance over three seasons (years). Field results for two years confirmed previous glasshouse findings and demonstrate protection in terms of attack by vine weevil larvae on all the transgenic lines. Over three years, two ‘Melody’ lines and three ‘Symphony’ lines continued to demonstrate significantly improved plant growth compared with control lines. The genotype into which CpTi was inserted had a significant effect on performance. The CpTi has a significant effect on vine weevil in terms of a reduction in the number of pupae. The numbers of Carabid and other non-target arthropods were assessed over the duration of the trial, and were found not to be significantly affected by the CpTi transgenic lines.

Behavioural response of Heterorhabditis megidis towards plant roots and insect larvae

The behavioural response of infective juveniles (IJs) of Heterorhabditis megidis (strain NLH-E87.3) to cues from roots of strawberry (Fragaria x ananassa Duch.), thuja (Thuja occidentalis L.) and to larvae of the black vine weevil, Otiorhynchus sulcatus, was studied. Choice assays were conducted in an Y-tube olfactometer filled with moist sand. Infective juveniles were activated by the presence of intact roots of both strawberry and thuja plants. Some nematodes aggregated in the compartments with roots but most moved away from the roots to the opposite side. Given a choice, IJs showed a preference for strawberry roots above O. sulcatus larvae. No difference in preference was observed between thuja roots and O. sulcatus larvae. The combination of strawberry roots with vine weevil larvae was preferred above roots alone. In the assays with thuja roots and larvae versus thuja roots alone, however, IJs were stimulated to move but showed preference for the opposite compartment away from the arms with roots and larvae. Nematodes responded differently to mechanically damaged roots as opposed to roots damaged by vine weevil larvae. In assays with damaged thuja roots, IJs were most attracted by the roots damaged by larvae, whereas in the strawberry assays IJs showed a clear preference for the mechanically damaged roots. When challenged with a choice between strawberry and thuja roots, IJs moved preferentially to strawberry than to thuja roots. A preference for the combination of strawberry roots plus larvae over the thuja roots plus larvae was also observed.

Use of a cold-active entomopathogenic nematode Steinernema kraussei to control overwintering larvae of the black vine weevil Otiorhynchus sulcatus (Coleoptera: Curculionidae) in outdoor strawberry plants

AbstractThe susceptibility of overwintering black vine weevil larvae Otiorhynchus sulcatus to a cold-active entomopathogenic nematode, Steinernema kraussei (isolate L137) and a commercial proprietary biopesticide, Steinernema carpocapsae (Exhibit) was assessed on outdoor potted strawberry plants. Nematodes were applied at a range of doses in early winter at a field site located in Warwickshire, England. Three months later, infestation and mortality of vine weevils were assessed. There was a clear dose response observed for S. kraussei applications. Up to 81% of vine weevil control was recorded by this nematode at the highest dose of 60 000 nematodes per pot, whereas treatments with S. carpocapsae caused no significant mortality at the dose rates used. Dissection of vine weevil larvae showed infective juveniles had developed to adults within the host. Recovery of nematodes at the end of the experiment indicated that S. kraussei (L137) was able to survive winter field conditions including prolonged exposure to low temperatures (averaging 2.7°C during the experiment) in contrast to S. carpocapsae which showed poor survival. Of the two extraction methods used, the Baermann funnel technique was found to be more efficient than Galleria mellonella baiting, with up to 44% of the original highest dose of S. kraussei nematodes being recovered by Baermann funnel compared to 8% with G. mellonella at 18°C. These results suggest S. kraussei (L137) has potential as a commercial biocontrol agent against O. sulcatus at low temperatures.

Protecting Container-Grown Crops from Black Vine Weevil Larvae with Bifenthrin

Abstract Preplant incorporation of Talstar 0.2G (bifenthrin) can prevent root weevil and white grub infestations in container-grown nursery crops. Under some conditions, control failed in greenhouse experiments with black vine weevils. A low-density potting medium with 10 ppm of bifenthrin allowed 14–66% as many black vine weevil larvae to develop on Astilbe, Heuchera, Sedum, Taxus, and Thuja root systems as in an untreated medium. The greatest larval survival was in Sedum, which supported rapid development of larvae as internal feeders. A preplanting dip of roots into an 800 ppm bifenthrin suspension was itself very effective (91–99% control of larvae), and provided additive benefit with preplant potting mix incorporation of Talstar 0.2G. In a comparison of bulk-density based dosing and volume-based dosing of potting media, the best regression model used solely the volume-based dosage for estimating the resulting average larval population, while the weight-based dosage gave a simple relationship for estimating the maximum larval survival. Preventing black vine weevil development requires incorporation of 32 ppm of the granular bifenthrin product into potting media.

Evaluation of Biological and Chemical Control Methods for Black Vine Weevil, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), in Container Grown Perennials

Abstract Three trials involving the nematode Heterorhabditis bacteriophora (Poiner) provided convincing evidence that this entomopathogenic nematode can provide highly effective control of black vine weevil larvae under conventional methods of container plant production. In all trials, the application of nematodes significantly reduced populations of weevil larvae relative to levels found in the untreated containers. The first and second trials, using Bergenia and Heuchera, confirmed that H. bacteriophora applied at two rates caused substantial mortality to black vine weevil larvae. The third trial revealed that H. bacteriophora applied to Epimedium provided levels of control comparable to those of imidacloprid and acephate. In all trials, populations of weevil larvae were reduced by 90–100% following the application of H. bacteriophora.

Effects of Density, Age and Host Cues on the Dispersal of Heterorhabditis megidis

Agar plate assays were used to assess the effect of density, incubation time and age of nematodes and the presence of insect hosts on the dispersal of infective juveniles (IJs) of Heterorhabditis megidis (strain NLH-E87.3). IJs dispersed faster and further at high densities than at low densities. Dispersal was also influenced by the age of the IJs. Individuals stored for a period of 1.5 and 4.5 weeks showed to be more active than those stored for 2.5 and 3.5 weeks. The presence of a host insect enhanced the dispersion of nematodes. The increasing in the incubation period showed that IJs responded positively to host cues from Galleria mellonella but poorly to cues from Otiorhynchus sulcatus larvae.

Improved Control of Otiorhynchus sulcatus at 9°C by Cold-stored Heterorhabditis megidis UK211

The effect of storage temperature (9 and 20°C) on North West European Heterorhabditis megidis isolate UK211 for control of Otiorhynchus sulcatus larvae at 9°C is assessed. O. sulcatus mortality increased from -5.3% (corrected mortality) using freshly produced nematodes, to 27.1% using nematodes that had been cold-stored for 12 weeks. The number of nematodes invading the insect larvae increased almost 27-fold. Nematode storage at 9°C for 11 to 12 weeks weeks resulted in significantly higher O. sulcatus mortality (41%) than storage at 20°C for 2 to 3 weeks (12%). Thus, cold storage does enhance nematode infectivity for O. sulcatus larvae.

Plants protect their roots by alerting the enemies of grubs

Plant roots in the soil are under attack from many soil organisms. Although many ecologists are aware of the presence and importance of natural enemies in the soil that protect the plants from herbivores, the existence and nature of tritrophic interactions are poorly understood. So far, attention has focused on how plants protect their above‐ground parts against herbivorous arthropods, either directly or indirectly (i.e. by getting help from the herbivore’s enemies). This article is the first in showing that indirect plant defences also operate underground. We show that the roots of a coniferous plant (Thuja occidentalis) release chemicals upon attack by weevil larvae (Otiorhynchus sulcatus) and that these chemicals thereby attract parasitic nematodes (Heterorhabditis megidis).

Species‐specific responses of a root‐ and shoot‐feeding insect to arbuscular mycorrhizal colonization of its host plant

Summary The responses of root‐feeding black vine weevil (Otiorhynchus sulcatus) larvae and leaf‐feeding adults to colonization of strawberry (Fragaria x ananassa) plants by one or two species of arbuscular mycorrhizal fungi are reported here. Glomus mosseae and Glomus fasciculatum were isolated from a commercial field and used to colonize strawberry plants, singly and in combination. Vine weevil larvae were reared on roots of colonized and uncolonized plants. When the larvae were mature, leaves from all plants, with and without larvae, were fed to adult weevils. Colonization by either fungus reduced larval survival and biomass. However, colonization by both fungi had no effect on the larvae. These effects were manifested in changes in plant performance; weevil feeding decreased plant foliar and root biomass as well as runner production, but only when mycorrhizas were absent or inoculated together. Mycorrhizas also mitigated the effects of larval feeding on adult weevils. The response of root‐feeding insects to arbuscular mycorrhizal colonization depends on which fungi are present in the root system. Furthermore, arbuscular mycorrhizal fungi might play a critical role in mitigating interactions between phytophagous insects.

Orientation of Heterorhabditis megidis to insect hosts and plant roots in a Y‐tube sand olfactometer

AbstractThe host‐searching behaviour of Heterorhabditis megidis strain NLH‐E 87.3 in the presence of insect hosts and plant roots, offered individually and in combination, was studied using a newly developed Y‐tube olfactometer filled with sand. Within a period of 24 hours infective juveniles (IJs) were significantly attracted to living G. mellonella larvae and caused 100% larval mortality. Otiorhynchus sulcatus larvae, however, did not elicit host‐oriented movement of IJs and no larval mortality was observed. Roots of strawberry plants induced a negative response in IJs. The combination of strawberry roots and O. sulcatus larvae, however, strongly attracted IJs leading to 37% host mortality. It was shown that this type of Y‐tube choice arena is a useful tool in studying the searching behaviour of entomopathogenic nematodes in a semi‐natural habitat.