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Species Page

strawberry root weevil

Otiorhynchus ovatus

Distribution

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Host plants / species affected

Main hosts

show all species affected
Fragaria (strawberry)
Fragaria ananassa (strawberry)
Rubus idaeus (raspberry)
Thuja occidentalis (Eastern white cedar)
Tsuga (hemlocks)
Vaccinium (blueberries)

List of symptoms / signs

Growing point - external feeding
Leaves - abnormal colours
Leaves - abnormal forms
Leaves - external feeding
Roots - external feeding
Roots - internal feeding
Roots - reduced root system
Whole plant - dwarfing
Whole plant - external feeding
Whole plant - plant dead; dieback

Symptoms

On strawberry in Bulgaria, the larvae of O. ovatus feed on the roots, mining the roots and causing the plants to wilt and the fruits to mummify and in heavy infestations killing the plants (Burov, 1964).

Infested strawberry plants are stunted, the leaves closely bunched together and very deeply coloured, or dying, the fine roots and the crown having been eaten off close to the ground, by small, fat, curved larvae with pale-brown heads (Metcalf and Metcalf, 1993).

The larvae of O. ovatus feed on the roots of spruce seedlings, causing the needles to turn yellow or rust-coloured and the seedlings to die (Srot, 1979).

Prevention and control

Cultural Control

Deep ploughing and rolling infested plants before the first adults appear are recommended for control, and trap pits and trenches to prevent migration to fresh plantings (Mutz, 1951).

In principal, strawberries should not be grown in succession (Stenseth, 1979).

Destroying old beds promptly after the last picking and rotating new beds to fields that have been in cultivation, but have not had strawberries on or near them for at least 1 year, are of value. This insect may be kept out of the strawberry fields by constructing a barrier of tarred boards around the new fields (Metcalf and Metcalf, 1993).

Biological Control

The nematodes Steinernema carpocapsae, S. glaseri and Heterorhabditis bacteriophora have been tested for control of O. ovatus in strawberries in Massachusetts, USA, and have been shown to cause 82-91% mortality (van Driesche and Hauschild, 1987).

Three species of nematodes were tested in the field and greenhouse as potential biological control agents against O. ovatus. Under greenhouse conditions, Heterorhabditis sp. NC447 was the most effective nematode of the three tested against O. ovatus on potted Douglas fir (Pseudotsuga menziesii) seedlings, and Steinernema feltiae the least effective, at all dosages tested. A field trial with Heterorhabditis heliothidis against O. ovatus in a forest nursery did not provide a significant degree of weevil control. This lack of control was attributed to the low average outdoor temperature (11°C) at the time of treatment and the higher than average rainfall (Rutherford et al., 1987).

In Finland, augmented populations of the nematode, Steinernema sp. were able to persist for at least 2 years in the strawberry fields. In the absence of curculionids, nematode populations did not persist as well as in areas with heavy pest populations (Vainio and Hokkanen, 1993).

The efficacy of Heterorhabditis marelatus, a newly described species of entomopathogenic nematode, was compared with that of H. bacteriophora against the root weevil, O. ovatus in strawberry. In the laboratory, H. marelatus was significantly more virulent than H. bacteriophora on O. ovatus 7 days after nematode application at 14°C. In field experiments in Oregon, USA, 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 and 74%, 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).

In eastern Poland, the fungus Paecilomyces fumosoroseus is the most promising pathogen for the biological control of larvae and pupae of O. ovatus (Mietkiewski et al., 1993).

O. ovatus larval populations in Massachusetts, USA, cranberry bogs showed 32-38% mortality following spray application of Steinernema carpocapsae (A11 strain) or Heterorhabditis bacteriophora (NC-1-strain). A bioassay of larval and pupal O. ovatus with S. carpocapsae resulted in 62% mortality and with H. bacteriophora in 51% mortality. A following trial with increased spray pressure reduced the O. ovatus population from 26.7 to 0.6 live larvae/sample (with S. carpocapsae) and from 16.2 to 1.8 live larvae/sample (with H. bacteriophora, HP88 strain) after 240 h. In this trial, bioassay of O. ovatus resulted in 74.0% mortality with S. carpocapsae and 68.85% mortality with H. bacteriophora (Simser and Roberts, 1994).

Host-Plant Resistance

Several clones of the wild 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. ovatus. 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 preoviposition period of newly emerged adults. Egg production correlated closely with the amount of feeding on a clone (Shanks et al., 1984).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


This information is part of a full datasheet available in the Crop Protection Compendium (CPC);www.cabi.org/cpc. For information on how to access the CPC, click here.

Impact

O. ovatus is not normally injurious to strawberries in Germany, but caused serious damage in large plantings at Strehla in Saxony, in 1946 and again in 1949, when crop losses amounted to 75-100% and 20% of the beds were completely destroyed. The injury to strawberries was almost entirely confined to 3-year-old plants. The larvae fed on the roots and were particularly injurious between the middle and end of May, just before they pupated, when up to 15-20 per plant were found (Mutz, 1951).

Adults of O. ovatus were observed attacking strawberry in 1939 for the first time in Norway. Attack was severe in southern districts in 1947 and subsequent years. Conifers grown in nurseries, especially spruce, were also injured. Injury was most severe on second- and third-year strawberry plants (Fjeldallen, 1953).

Species of Otiorhynchus, including O. ovatus, have seriously damaged strawberry in Bulgaria prior to 1964. The larvae feed on the roots, mining the roots and causing the plants to wilt and the fruits to mummify and in heavy infestations killing the plants (Burov, 1964).

O. ovatus is one of the two most ubiquitous and damaging species in the genus. Larvae destroy roots; adults may cause unacceptable defoliation during 4 weeks of maturation feeding and a 3 month oviposition period. It is an occasional pest of conifers in nursery production in many parts of the world (Glover, 1989).

Considerable damage was caused by O. ovatus larvae to the root system of trees in nurseries in Bas-Saint-Laurent, Quebec, Canada during 1990 (Anon., 1991).