Anthonomus rubi on Strawberry Fruit: Its Biology, Ecology, Damage, and Control from an IPM Perspective

The strawberry blossom weevil (SBW), Anthonomus rubi, is a well-documented pest of strawberry. Recently, in strawberry fields of Trento Province (north-east Italy), new noteworthy damage on fruit linked to SBW adults was observed, combined with a prolonged adult activity until the autumn. In this new scenario, we re-investigated SBW biology, ecology, monitoring tools, and potential control methods to develop Integrated Pest Management (IPM) strategies. Several trials were conducted on strawberry in the laboratory, field and semi-natural habitats. The feeding activity of adult SBW results in small deep holes on berries at different stages, causing yield losses of up to 60%. We observed a prolonged survival of newly emerged adults (>240 days) along with their ability to sever flower buds without laying eggs inside them in the same year (one generation per year). SBW adults were present in the strawberry field year-round, with movement between crop and no crop habitats, underlying a potential role of other host/feeding plants to support its populations. Yellow sticky traps combined with synthetic attractants proved promising for both adult monitoring and mass trapping. Regarding control, adhesive tapes and mass trapping using green bucket pheromone traps gave unsatisfactory results, while the high temperatures provided by the black fabric, the periodic removal of severed buds or adults and Chlorpyrifos-methyl application constrained population build-up. The findings are important for the development of an IPM strategy.

The Eurasian strawberry blossom weevil, Anthonomus rubi (Herbst, 1795), is established in North America

We report the strawberry blossom weevil, Anthonomus rubi (Herbst, 1795) (Coleoptera: Curculionidae), a species native to Europe, Asia, and North Africa, as established in British Columbia, Canada. This is the first report of A. rubi in North America. We provide a diagnosis of the species and compare it with other species of the genus Anthonomus Germar in Canada. This species is a pest of plants in Rosaceae Jussieu, including economically important berries such as strawberries (Fragaria Linnaeus) and raspberries (Rubus idaeus Linnaeus), and of native berries of importance to Indigenous peoples in Canada. Female weevils oviposit eggs inside developing flower buds and sever flower stalks, facilitating larval development inside damaged buds and thus reducing fruit yields. Surveys to confirm the presence of A. rubi conducted in 2020 found the weevil to be well established in cultivated and wild hosts throughout the Greater Vancouver area and Fraser Valley, British Columbia. At least one species of parasitoid wasp in the genus Pteromalus Swederus (Hymenoptera: Pteromalidae) has been found in association with A. rubi in the province. Future investigations are required to understand the biology of A. rubi in its new range, assess its impact on berries, and develop management strategies.

Composition of Strawberry Floral Volatiles and their Effects on Behavior of Strawberry Blossom Weevil, Anthonomus rubi

The strawberry blossom weevil (SBW), Anthonomus rubi, is a major pest in strawberry fields throughout Europe. Traps baited with aggregation pheromone are used for pest monitoring. However, a more effective lure is needed. For a number of pests, it has been shown that the attractiveness of a pheromone can be enhanced by host plant volatiles. The goal of this study was to explore floral volatile blends of different strawberry species (Fragaria x ananassa and Fragaria vesca) to identify compounds that might be used to improve the attractiveness of existing lures for SBW. Floral emissions of F. x a. varieties Sonata, Beltran, Korona, and of F. vesca, were collected by both solid-phase microextraction (SPME) and dynamic headspace sampling on Tenax. Analysis by gas chromatography/mass spectrometry showed the floral volatiles of F. x ananassa. and F. vesca were dominated by aromatic compounds and terpenoids, with 4-methoxybenzaldehyde (p-anisaldehyde) and α-muurolene the major compounds produced by the two species, respectively. Multi-dimensional scaling analyses separated the blends of the two species and explained differences between F. vesca genotypes and, to some degree, variation between F. x ananassa varieties In two-choice behavioral tests, SBW preferred odors of flowering strawberry plants to those of non-flowering plants, but weevils did not discriminate between odors from F. x ananassa and F. vesca flowering plants. Adding blends of six synthetic flower volatiles to non-flowering plants of both species increased the preference of SBW for these over the plants alone. When added individually to non-flowering plants, none of the components increased the preference of SBW, indicating a synergistic effect. However, SBW responded to 1,4-dimethoxybenzene, a major component of volatiles from F. viridis, previously found to synergize the attractiveness of the SBW aggregation pheromone in field studies.

Reproduction of entomopathogenic nematodes of the genera Steinernema Travassos, 1927 (Rhabditida: Steienernematidae) within strawberry blossom weevil larvae Anthonomus rubi Herbst, 1795 (Coleoptera: Curculionidae)

Studies have been conducted on the contamination in the laboratory of larvae of raspberry-straw weevil (Anthonomus rubi Herbst, 1795) with two isolates of entomopathogenic nematodes (ETNs) of the genus Steinernema Travassos, 1927, vchecked the possibility of their reproduction under these conditions, and features of quantitative performance indicators. On the basis of the obtained data, it was established that, regardless of the type of isolate of the EPN, all experimental A. rubi larvae died on the 3rd day after infection, and the yield of larvae nematodes from the dead insects began on day 10—12 and lasted 42—44 days. During this period, on average, from one of the affected specimens of raspberry-straw weevil, from 26965 to 29168 larvae of the EPN was allocated. The total number of larvae of EPN obtained in the infection of 14 larvae of weevil of raspberry-strawberry was 392929 individuals. The migration of newly-formed individuals of the EPN was uneven, the bulk of the larvae (61—66.2%) is released during the second decade of the month, the rest — 24.5%—31.2% in the third decade. In the first and last decades the larvae are significantly less (3.5—5.8%).

Newly introduced strawberry genotypes for Nordic Baltic conditions

Eight recently introduced strawberry genotypes ‘Chambly’, ‘Clery’, ‘Darselect’, ‘Delia’, ‘Harmonie’, ‘Matis’, ‘Sallybright’, ‘Salsa’ and ‘Senga Sengana’ (standard cultivar) were evaluated at the Polli Horticultural Research Centre of the Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences. Phenology, winter hardiness, strawberry blossom weevil (Anthonomus rubi) injury, yield, fruit weight, soluble solids, sugar, acid and ascorbic acid content of the fruit were determined. Genotypes more suited to the Estonian climate conditions are the winter hardy, late-yielding cultivars ‘Salsa’ and ‘Harmonie’. ‘Salsa’ has a good, high quality yield with large attractive fruit. The fruit of ‘Harmonie’ contains much ascorbic acid, but the sugar-acid ratio is less balanced. Early genotypes ‘Chambly’, ‘Clery’, ‘Darselect’, ‘Delia’, ‘Sallybright’ and the late genotype ’Matis’ have a lower yield than the standard cultivar ‘Senga Sengana’.

New strawberry genotypes tested for organic production on a Verticillium-infested site

Nineteen new strawberry breeding clones, bred at the Institute for Breeding Research on Fruit Crops in Dresden-Pillnitz, Germany, were evaluated for their suitability for organic production at a Verticillium-infested site in Vienna, Austria. Soil cover, plant vitality, resistance to leaf spot diseases as well as flower damages by the strawberry blossom weevil (Anthonomus rubi) and by spring frost were recorded. In two consecutive years, marketable yield and fruits infested by Botrytis cinerea were assessed. Three breeding clones, P-7189, P-8043 and P-8071, were considered as suitable for organic strawberry production. P-7189 and P-8043 showed high tolerance to Verticillium wilt. The breeding clones P-8155 and P-8166 performed well under organic management but had very soft fruits that were not acceptable for commercial fruit production. The rest of the breeding clones were low-yielding, however, some of them could be of interest for home gardens due to their good flavour and high plant vitality.