Otiorhynchus sulcatus
(vine weevil)

O. sulcatus was first detected in Hawaii, USA, at Kokee State Park on the island of Kauai, in March and April 1976 (Anon., 1976).

O. sulcatus was first found in Japan in 1981 in Sunto Gun, Shizuoka Prefecture (Masaki et al., 1984).

Records of O. sulcatus in Colombia (Seymour et al., 1985; EPPO, 2009) published in previous versions of the Compendium are based on an interception record which is considered invalid. O. sulcatus has not been recorded in Colombia by Barrigna-Tuñón (2013) or the Museum of Entomology, University of Valle, Colombia, and has not been reported in Colombia by the Institute of Natural Sciences, National University of Colombia. 

Scherf (1964) listed Fragaria vesca, Saxifraga sp., Taxus baccata, Rudbeckia laciniata, Cyclamen persicum and Vitis vinifera as food plants of O. sulcatus.

The reproductive success of O. sulcatus fed different foliar diets was compared to evaluate the suitability of known and potential hosts for adults. Foliar diets, arranged in order of decreasing fecundity, were Taxus cuspidata, T. canadensis, Kalmia latifolia and Cornus florida. Fecundity and length of preoviposition period were negatively correlated, indicating that the latter could be used to forecast potential fecundity (Maier, 1981).

In Japan, of 108 candidate plant species in 49 families, the adults of O. sulcatus fed on the leaves of 101 species, in 46 families. In tests with 68 candidate species in 29 families, the larvae fed on the roots of 55 species in 24 families. Of these, 90 species in 45 families are new food-plant records for the adults and 46 species in 21 families are new food-plant records for the larvae. The results indicated that the preferred food-plants of both adults and larvae are in the family Rosaceae (Masaki et al., 1984).

Food preferences of O. sulcatus adults were studied in the laboratory at LD 16:8 with corresponding temperatures of 23 and 17°C and 80% RH, using five plant species (Fragaria grandiflora, Chenopodium album, Senecio vulgaris, Rhododendron ponticum and Fuchsia spp.). R. ponticum was the least preferred plant, while strawberry was the most preferred (Gembauffe et al., 1990).

According to Morris (1997), O. sulcatus is mainly ground-living, though it is occasionally found on herbaceous vegetation, less frequently on trees.

It is parthenogenetic over most of its range, although bisexual races are known from Italy (Morris, 1997).

In Denmark, the females first appear in June, but do not become numerous until July. They feed on the leaves of strawberry and begin to oviposit after 4-6 days, laying several hundred eggs each over a period. The larvae hatch in 1-3 weeks according to temperature and feed on small roots in the soil, so that they are hard to detect at first. They overwinter and cause the major part of the damage in April-May of the next year, when the whole root system of strawberry plants may be destroyed. They pupate between late May and the end of June. At this time, old adults from the previous year are still present and laying eggs, but they are less prolific than adults of the new generation. Development is very dependent on temperature, and plastic covers or other mulches can speed it up by a month or more, and in heated greenhouse conditions oviposition may continue throughout the year (Esberg, 1977).

In the Lago Maggiore district of Italy, O. sulcatus has one generation a year, but development times varied greatly with temperature and were different in field and greenhouse crops. In the field, eggs were present from mid-April to early June, larvae from late May to early October, pupae from late September to the end of November, and adults (which overwintered) from the beginning of November to mid-April. The main larval damage occurred in the summer in the field, and in the winter in the greenhouse (Lozzia, 1983).

The biology of O. sulcatus in a commercial vineyard in coastal California, USA, was studied in 1984-86. Adult emergence began in the first week of April and continued until early July, with peaks in mid- to late May, but the pattern differed from year to year. Oviposition began in mid-May and continued for 6-8 weeks (Phillips, 1989).

The biology of O. sulcatus was studied in the laboratory at 20-22°C and LD 16:8 on strawberry leaves. Eggs were transferred to Impatiens plants at 20°C and LD 14:10. The time from pupation to adult emergence was 14.10 days at 20°C and newly emerged adults remained in the pupal cells for 2-5 days following emergence. The pre-oviposition period lasted 5-23 weeks, with the majority (94%) of adults beginning oviposition 5-8 weeks after emergence. The 32 adults which survived the first weeks after emergence had a mean longevity of 46.5 weeks. Mean fecundity was 830 eggs/adult, with a viability of 80.8%. Two distinct egg-laying cycles were observed: the first extended from late spring to October and the second from late November until the following summer. A third cycle extending into the spring of the final year was also indicated (Moorhouse et al., 1992).

In Idaho, USA, although some adults survived winter conditions, O. sulcatus overwintered primarily as developing larvae associated with hop root systems 5-50 cm deep in the soil. Pupation began in mid-April with soil temperatures of 15-17°C and concluded in mid- to late April. Adult emergence began in early May and was complete by late May to early June in 1986-88. The preoviposition period averaged 26 days in the field. The mean number of eggs laid per adult female was 290 (with a range of 22-1230). Eggs hatched in 12-22 days at 21°C (Baird et al., 1992).

In Japan, the development of O. sulcatus was investigated at constant temperatures of 12, 15, 18, 21 and 26°C. The development threshold temperatures for eggs, larvae plus prepupae, pupae, and the preoviposition period were 6.32, 2.45, 6.09 and 8.44°C, respectively. The thermal constants for eggs, larvae plus prepupae, pupae and the preoviposition period were 186.43, 2061.93, 182.85 and 571.10 day-degrees C, respectively. The rate of development from the first to the fifth larval instar was greater at higher temperatures, but development of the sixth and seventh instars was slower at higher temperatures. The developmental zero of the first to fifth instars was -0.66, -0.40, 1.66, 2.83 and 2.40°C, respectively. Almost all larvae pupated at temperatures between 12 and 21°C, but at 24 and 26°C, only one larva pupated. Larvae moulted 4-5 times at 15°C, 5-6 times at 18 and 21°C, 6-8 times at 24°C, and 6-9 times at 26°C (Masaki and Ohto, 1995). In Belgium, the time of appearance of O. sulcatus varied from year to year and was largely dependent on weather conditions (temperature) and type of culture (open field, container culture or greenhouse) (Casteels et al., 1995).

The six larval instars of O. sulcatus completed development from eggs inoculated onto container-grown rhododendrons in 84 days when grown indoors at 18-22°C or 211 days outdoors in Oregon, USA. Larval mortality was greatest during instars I-III. During instars IV-VI, mortality increased with increasing insect density. Underground stem tissue was fed on exclusively by instars IV-VI, and the amount of tissue removed increased with larval density (la Lone and Clarke, 1981).

Schwenke (1974) reported the tachinid Pandelleia otiorhynchi from O. sulcatus.

In western France, three species of the nematode order Rhabditida, one species of bacterium (Bacillus cereus) and five species of Deuteromycete (Metarhizium flavoviride, M. anisopliae, Paecilomyces fumosoroseus, Beauveria bassiana and B. brongniartii) were isolated from O. sulcatus. M. anisopliae caused the highest rate of mortality (28%) by natural infection (Marchal, 1977).

In the Netherlands, comparative studies of O. sulcatus and its predators in abandoned strawberry fields and in fields treated with insecticides indicated that carabid adults and larvae (notably those of Bembidion ustulatum which fed on eggs) were active predators, but were unable to exert effective control in treated fields (Evenhuis, 1982).

B. bassiana was isolated from the adults of O. sulcatus in Japan (Saito and Ikeda, 1983).

Look at the foliage of plants for signs of adult damage. The adults eat irregularly-shaped notches from the leaf margin. Feeding takes place at night, but the small black weevils may be seen during the daytime in the leaf litter or some other dark place. Dig up wilting plants or tip plants out of pots, to find small, creamy-white, curved, legless larvae with pale-brown heads, feeding at the roots, or burrowing into the corm if this is present.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control

In Washington, USA, it was thought that mowing off strawberry fields after harvest would reduce populations of O. sulcatus. In 1975 and 1976, about 60% of adults died after the foliage was mowed off and removed; there was 0-12% mortality in unmowed plots (Garth and Shanks, 1978).

In the Dordogne, France, suggestions for prevention of O. sulcatus attacks include the use of healthy plants, careful soil preparation and crop rotation (Felici, 1981).

Steinernema carpocapsae was applied to beds of Euonymus fortunei in an urban park in Philadelphia, USA, to evaluate its potential for controlling O. sulcatus. Although no significant difference was attributed to nematode treatments, weevil damage in non-irrigated beds was lower than in irrigated beds. Irrigation management may be helpful for controlling this pest (Owen et al., 1991).

Biological Control

The parasitic nematode Heterorhabditis bacteriophora and the fungal pathogens Metarhizium anisopliae and Beauveria bassiana were used in a trial for the control of larvae of O. sulcatus in nursery Rhododendron stock in New Zealand in 1988. Larvae of the pest were added to planter bags containing Rhododendron plants and the control organisms were added 2 weeks later. After 5 weeks, H. bacteriophora, M. anisopliae and B. bassiana had achieved 93, 32 and 39% control, respectively (Barratt et al., 1989a).

Three of five isolates of Heterorhabditis sp. and M. anisopliae controlled larvae of O. sulcatus on Thuja occidentalis in containers in the field in the Netherlands during September-October 1991. In open ground, two of three isolates of Heterorhabditis sp. tested were effective as was M. anisopliae. The efficacy of Heterorhabditis sp. was determined by soil temperature and antagonism in soil (van Tol, 1993).

The virulence of 10 isolates of M. anisopliae against larvae of O. sulcatus was examined in greenhouses on potted Begonia. The most virulent isolate, 275-86, reduced numbers of larvae by 86% compared with control (untreated) larvae (pots treated with 0.05% Triton X-100 only), and two other isolates reduced the larval population by 80%. Three isolates of M. anisopliae were examined further for their persistence in peat compost. All three strains reduced larval numbers on Begonia compared with the controls. The highest levels of control were recorded with strain 100-82 (67-80%), which was significantly more virulent than strain 35-79. Fungal drenches were most effective when they were applied 8 weeks before the application of eggs of O. sulcatus; however, significant levels of control were also recorded with fungal spores which were applied 16 weeks before the eggs. The results demonstrated that M. anisopliae has considerable potential as a biological control agent of O. sulcatus in greenhouses (Moorhouse et al., 1993).

Mortality of O. sulcatus larvae at 10, 15, 20 and 25°C following treatment with 100 million conidia/ml suspensions of six M. anisopliae isolates was temperature-dependent. In all cases, the LT50s (time taken to kill 50% of the test population) were inversely related to temperature, but the nature of this response varied between isolates. Strain 101-82 was the most virulent isolate at 25°C, with an LT50 of 3.7 days, but it was the least virulent isolate at 15°C and it failed to kill any O. sulcatus larvae at 10°C. In contrast, strain 159-83 had the lowest virulence at both 20 and 25°C, whereas it was the most virulent isolate at 10°C with an LT50 of 20 days. The mortality rates followed a similar pattern and were positively related to temperature in all cases with the exception of strain 159-83 at 25°C (Moorhouse et al., 1994).

Three species of nematodes were tested in the field and greenhouse as potential biological control agents against O. sulcatus in British Columbia, Canada. Heterorhabditis heliothidis at doses of from 5000 to 20000 infective stages per 50 ml water reduced the numbers of O. sulcatus on potted strawberry plants in the greenhouse by 83-97%. An outdoor application of H. heliothidis at 500 and 5000 nematodes/litre of soil gave significantly better control of larvae of O. sulcatus on potted lodgepole pine trees (Pinus contorta) than did a diazinon drench (Rutherford et al., 1987).

On strawberries in Massachusetts, USA, the nematodes Steinernema carpocapsae, S. glaseri and Heterorhabditis bacteriophora caused 82-91% mortality, when tested for control of O. sulcatus (Driesche and Hauschild, 1987).

A commercial formulation of the entomophilic nematode H. bacteriophora was tested for the control of O. sulcatus in nursery cyclamen stock in New Zealand during 1990. More than 1400 plants were treated with 80 nematodes/cm² using syringes. The number of infested pots was reduced from 27 to 3.8% following treatment and the number of weevils was reduced by 73% (Garnham and McNab, 1990).

The ability of Steinernema feltiae, S. rara and Steinernema sp. strain Tlein, Steinernema sp. strain Pac and Steinernema sp. strain Cuban to control larvae of O. sulcatus was studied in the laboratory and in the field in the Czech Republic. Of the five strains tested in the laboratory, S. feltiae strain Hyl gave the best results, providing 100% elimination of larvae on azaleas [Rhododendron sp.]. Three releases of this nematode (300,000 infectives/plant) were performed in three beds of Rhododendron during 1989-90, resulting in 72-88% protection of plants in beds and 52-77% protection in adjacent plots. Only 30% of plants survived in untreated plots (Mracek et al., 1993).

H. bacteriophora has an active foraging strategy and occurs deep in the soil profile. It was effective against larvae of O. sulcatus, which occurs near roots. Soil temperature influenced the results. At 22°C, the nematode killed O. sulcatus within 1 week. At 16°C, H. bacteriophora was not effective against larvae of O. sulcatus 2 weeks after treatment (Kaya et al., 1993).

Experiments were carried out in containerized woody ornamentals (Taxus baccata and Rhododendron spp.) and in open field stands of strawberries in Germany to test entomopathogenic nematodes (Heterorhabditis sp.) as biological control agents against larvae of O. sulcatus. The following results were obtained: larvae, pupae and young adults were parasitized by Heterorhabditis. At soil temperatures above 12°C decreases in host densities of 81-100% were found, as well in containerized ornamentals as in field production of strawberries. Dosage levels could be reduced to 10,000 nematodes per 2 litre-container or 600,000 nematodes per m² without significant loss of efficiency. It is recommended that Heterorhabditis should be applied as soon as they are delivered, as cool storage for several weeks drastically reduced their efficiency (Backhaus, 1994).

A large number of isolates of entomophilic nematodes were evaluated for their efficacy against O. sulcatus in strawberries at 9, 12 and 20°C. No marked differences were found between Heterorhabditis spp. and Steinernema spp. at 20°C, but the isolates responded differently to low temperatures. Three isolates (HFsel, HUk 211 and S. kraussei Mr) gave almost 50% control at 9°C and, in addition to K122 and HB1'87, these isolates also performed well at 12°C (Westerman and Zeeland, 1994).

In laboratory studies, the effect of a range of temperatures (5-30°C) on the infectivity of Heterorhabditis sp. and Steinernema carpocapsae against O. sulcatus was tested. An increase in temperature resulted in an increase in infectivity of both nematodes. A 100% mortality of O. sulcatus was obtained when Heterorhabditis sp. was kept at 20°C for 12 days. A maximum mortality of 65% was obtained with S. carpocapsae at 20 and 25°C (Miduturi et al., 1994).

In contrast to the traditional production method for heterorhabditid nematodes, lower production costs and prices, and higher quality standards are expected by a new, innovative technology for producing nematodes, developed by the Institute for Phytopathology of the University of Kiel, Germany (von Reibnitz and Backhaus, 1994).

The temperature profile relating to the efficacy of the UK isolate of S. carpocapsae against O. sulcatus on strawberry was clearly delineated between 15 and 33°C. The nematode can be delivered through a drip irrigation system without loss of viability, and the distribution of the nematodes through two T-tapes along and across the raised beds was very satisfactory. Nematodes can be applied either during the late summer or early autumn or in the late spring when temperatures are high enough to give satisfactory control (Kakouli et al., 1994).

Temperature profiles were obtained for two isolates of S. carpocapsae (ALL and UK) and two isolates of Heterorhabditis (Nemasys-H and Fightagrub) against late-instar larvae of O. sulcatus. Efficacy was clearly delineated for each isolate as: S. carpocapsae 14-33°C; Nemasys-H 14-28°C; and Fightagrub 14-33°C (Schirocki and Hague, 1994a).

The efficacy of two isolates of S. carpocapsae (All Biosys 25 and UK Biosys 252) and two isolates of Heterorhabditis (UK isolate Nemasys H and UK isolate Fightagrub) was investigated against O. sulcatus at a range of temperatures, on a temperature gradient plate. The temperature profiles for both Steinernema isolates were similar (15-32°C), but the Heterorhabditis isolates were dissimilar: Nemasys H was more effective at 13-28°C, while Fightagrub infected O. sulcatus larvae up to 35°C (Schirocki and Hague, 1994b).

In greenhouse trials there was 70-95% and 35-50% control of O. sulcatus with 1000 infective juveniles/250 ml pot of Heterorhabditis sp. (HF85) and S. carpocapsae (S25), respectively, in 10-20 days. The doses of S. carpocapsae had a significant effect, whereas contact days were significant for HF85, a cold active strain, gave 99% control of O. sulcatus while S. carpocapsae gave only 56% control. In field experiments, 10,000 infective juveniles/plant of S. carpocapsae and Heterorhabditis sp. gave 10-20 and 10-40% control of O. sulcatus, respectively (Miduturi et al., 1994).

A study in Switzerland, showed that late instar (L 4-6) O. sulcatus can encapsulate and melanize invasive juveniles (IJ's) of Steinernema feltiae and S. kraussei that enter their digestive tracts. Dissection of O. sulcatus larvae, exposed at 9°C to nematode isolates found in the Swiss Alps, revealed up to 9 melanized IJ's in the mid-gut region. Encapsulation of IJ's occurred exclusively in insect larvae so that they died from the nematode treatment. The observed immune response in O. sulcatus larvae is therefore unimportant for the infectivity of S. kraussei and S. feltiae at 9°C (Steiner, 1996a).

The efficacy of Heterorhabditis marelatus, was compared with that of H. bacteriophora against O. sulcatus in strawberry in Oregon, USA. In the laboratory, H. marelatus was significantly more virulent than H. bacteriophora on O. sulcatus 7 days after nematode application at 14°C. In field experiments in Oregon, H. marelatus applied at concentrations of 52 and 136 infective juveniles (IJs)/cm² reduced numbers of root weevil larvae and pupae by 75.3 and 77.4%, respectively, 20 days after nematode application. H. bacteriophora applied at concentrations of 128 and 379 IJs/cm² reduced numbers of root weevils by 50.0 and 74.0%, respectively. Both nematode species were detected up to 30 days after application by baiting with Galleria mellonella larvae in soil samples collected from the field (Berry et al., 1997).

Host-Plant Resistance

Of 8 varieties of raspberry assessed for 5 characters, Glen Clova was the most resistant to O. sulcatus (Anon., 1975).

When O. sulcatus adults were fed on 8 strawberry genotypes, the lowest number of fertile eggs were produced after feeding on Totem. Among 8 red raspberry cultivars, the longest pre-oviposition periods were after feeding on Leo and Glen Prosen. Loganberry and the Rubus idaeus ss. strigosus selection Kilburne gave similar preoviposition periods to these cultivars. Since both Leo and Glen Prosen are R. occidentalis derivatives, it is suggested that this species might be of value in breeding for resistance to O. sulcatus (Cram and Daubeny, 1982).

Several clones of the wild beach strawberry (Fragaria chiloensis) were compared with clones of commercial strawberries (F. x ananassa)(both species are octoploid), for resistance to feeding by adults of O. sulcatus. Weevils fed less and had lower fecundity on F. chiloensis leaves than on F. x ananassa leaves. The F. chiloensis clones CL-5 and GCL-8 also increased the pre-oviposition period of newly emerged adults. Egg production correlated closely with the amount of feeding on a clone (Shanks et al., 1984).

The influence of leaf pubescence on the resistance of 25 clones of beach strawberry to O. sulcatus was investigated in no-choice tests under greenhouse conditions. Adults of the weevil fed significantly more on some clones than on others. Fecundity was correlated with feeding. The density of simple hairs on the abaxial leaf surface varied significantly between clones, and hair density was negatively correlated with feeding by the beetle. The results suggest that leaf pubescence plays a role in the resistance of certain beach strawberry clones to feeding by O. sulcatus adults (Doss and Shanks, 1988).

Doss et al. (1991) were the first to show that selection for black vine weevil resistance among Fragaria chiloensis x F. ananassa crosses is possible.

Larvae of O. sulcatus were reared at three densities (0, 2 or 8) on plants of Taraxacum officinale with and without infection by the mycorrhizal fungus, Glomus mosseae. On plants without the fungus, 84% of larvae developed to the last instar, however, only 43% reached the last instar on infected plants. The differential survival of larvae was evident in their effects on plant biomass. Significant interactions were found between larval density and infection, indicating that the mycorrhizal presence mitigated the effects of herbivory at low densities of larvae. Infection by G. mosseae thus conferred some degree of resistance in roots to this insect (Gange et al., 1994).

The cowpea trypsin inhibitor gene from cowpea (Vigna unguiculata), which confers resistance to insect pests, has been inserted into strawberry cultivars by Agrobacterium-mediated gene transfer. Greenhouse trials in which transformants were challenged by larvae of O. sulcatus established that this heterologous gene may have value in the soft fruit industry and it is envisaged that plants containing this gene will be resistant to chewing insects (Graham et al., 1996).

Chemical Control

Potted rhododendron plants in a nursery in New Zealand were treated with 1, 2 or 3 spray applications of carbaryl. Treatments were timed to be just after adult O. sulcatus emergence in early summer, with 2 weeks between repeat applications. Adult O. sulcatus survival was significantly reduced by double and triple applications of carbaryl, but larval establishment was not affected (Barratt et al., 1989b).

In pot plants in the UK, Cotoneaster bullatus and Thuja plicata were treated with controlled release chlorpyrifos granules and slow release fonofos and artificially infested with O. sulcatus 4-6, 18 and 30 months after treatment. In additional trials, the effect of peat/grit and peat/bark/grit soils on infestations on C. bullatus, T. plicata and Euonymus alatus and control by chlorpyrifos and fonofos were investigated. Chlorpyrifos in the controlled release formulation gave control of the pest for up to 3 seasons. Slow-release fonofos gave reliable control for 1 year. Granules were the easiest formulation to apply. In untreated pots, survival of O. sulcatus was greater in soil with bark than in soil without bark (Buxton et al., 1992).

In Friuli, Italy, the best time to apply insecticides such as acephate against the adults was in the 4- to 6-week period between the appearance of adults and the beginning of oviposition (Fregonese and Zandigiacomo, 1992).

The effectiveness of 19 pesticides in the chemical control of O. sulcatus on ornamental crops was evaluated in Poland during 1986-89. Under laboratory conditions the most effective chemical was diazinon mixed with potting medium. The effectiveness of pesticides was reduced in acid soil. The results of investigations on preventive applications of pesticides as a soil treatment showed that all test compounds gave very good control of the pest. In experiments on containerized stock of Taxus, the best results were obtained with diazinon and chlorpyrifos (Bogatko and Labanowski, 1993).

The contact toxicity of the plant-derived isothiocyanates, methyl, propyl, allyl, phenyl, benzyl and 2-phenylethyl isothiocyanates to eggs of O. sulcatus was tested. All isothiocyanates tested were toxic to weevil eggs; however, isothiocyanates containing an aromatic moiety (phenyl, benzyl and 2-phenylethyl) were considerably more toxic than aliphatic (methyl, propyl and allyl) isothiocyanates. Average mortality in acetone-treated controls was < 6%. These results suggest that soil amendments of Brassica spp. tissues producing aromatic isothiocyanates may have greater insecticidal potential than those producing aliphatic isothiocyanates (Borek et al., 1995).

Compost incorporation treatment for control of larvae of O. sulcatus on container-grown hardy ornamental nursery stock was investigated in a series of 87 tests of insecticides were carried out at four ADAS experimental centres in the UK (Leeds, Reading, Wolverhampton and Wye) from 1986 to 1989. Insecticidally treated plants and untreated controls were artificially infested with eggs at varying intervals before and after treatment, and the survival of the pest was assessed. Of the candidate materials tested, a slow-release granular formulation of chlorpyrifos incorporated into compost gave good control for up to 34 weeks after treatment (the longest period evaluated) and a microencapsulated slow release formulation of fonofos gave good control for up to 2 years (the longest period evaluated). Surface applications of these two organophosphates, though sometimes effective, were unreliable as either preventive or remedial treatments, even for short-term control (Cross et al., 1995).

Three field experiments, conducted at Efford, UK, in 1992, 1994 and 1995, showed that the incorporation of controlled-release chlorpyrifos granules into the compost of the propagation modules of strawberry plants gave significant control of larvae of O. sulcatus. Better control (approximately 90%) was achieved when field planting was in early August so that the root system was small at the time of egg infestation, than following planting in mid-May (approximately 50%) where a much larger root system had grown. Control was as good where the treated modules had a compost volume of 80 ml, as where the volume was 230 ml. Better control occurred when eggs used for artificial infestation were placed close to the crown of the plant than when placed 15 cm away. In a replicated field experiment at Hinton Admiral, Hampshire, UK, in 1994, pre-planting spot, band or whole-bed soil treatment of raised-bed, polythene-mulched plants (planted as bare-root runners) with the chlorpyrifos granules did not reduce the numbers of larvae significantly. In a further field experiment at East Malling, UK, in 1994, treatments of a 15 cm diameter by 15 cm deep cylinder of soil round each plant did not significantly affect larval numbers. A pre-planting spot treatment with imidacloprid granules or a curative drench was not efficacious, though good control was achieved with a standard curative drench of chlorpyrifos. The survival of eggs and young larvae of O. sulcatus was low < 9%), circumstantial evidence pointing to soil type and condition as being important determining factors. Lighter soils with a structure allowing easy movement of larvae appeared to be more favourable for the survival of the pest. When adults were caged round strawberry plants with the surrounding surface soil replaced by sand in the field, most eggs (> 70%) occurred in the top 0-1 cm of sand, 50% being found on or close to the surface (0-0.2 cm depth) in one experiment. Eggs were aggregated weakly round a single non-mulched plant, but there was little evidence of such aggregation round plants grown in polythene-mulched, raised beds. Survival to the semi-mature larval stage from eggs placed on, or 2 cm below the soil surface 15 cm from the crown of the plant was as great as for eggs placed on, or 2 cm below the surface, adjacent to the crown. Larvae migrated towards the crown of the plant during their development (Cross and Burgess, 1997).

Integrated Pest Management

In laboratory and pot experiments, treatments of Heterorhabditis spp. or etrimfos controlled O. sulcatus on azaleas [Rhododendron]. Applied alone, the chemical insecticides gave better control than the nematode.

Only by combining a fresh approach to maintaining growing areas free of adult weevils (using exclusion), by monitoring adult populations (to detect failure in exclusion), and more effective use of insecticides, can O. sulcatus be eliminated from rhododendron nurseries (Cowles, 1995).

Phytosanitary Measures

The need to pay careful attention to the health of material entering the nursery and of nearby shrubby vegetation to prevent a build up of O. sulcatus pest population was stressed by Fregonese and Zandigiacomo (1992).

In line with the law on forests, the production, sale and transportation of non-ornamental trees have been subjected to phytosanitary control in Quebec, Canada, since 1987. To achieve the objectives stipulated by the Law, three types of inspections are to be conducted in tree nurseries (certification, prevention and autumn inspection) to identify insect pests and pathogens. The inspections for 1993 involving 262 million plants produced in 45 nurseries revealed the presence of O. sulcatus and other Otiorhynchus spp. (Lachance, 1993).