NAME OF THE ORGANISM: Resseliella theobaldi (THOMTE)

Evaluation continues

EPPO Standard PM 4-10 Certification scheme for Rubus recommends inspection for Resseliella theobaldi as appropriate to the Rubus sp. or hybrid concerned. However, in the responses to the questionnaire, ES and SI supported deregulation in the EU; considering that plants for planting was not the main pathway. Evaluation continues on this criteria.
The Fruit SEWG commented that the pest was monophagous and recommended that it is only considered for listing on Rubus idaeus, not on all Rubus species. See section pathway.

Candidate

Resseliella theobaldi (raspberry cane midge) is narrowly monophagous on Rubus idaeus (Ellis, 2001-2024). Nijveldt (1963) investigated a range of Rubus spp. to determine the host range of R. theobaldi. Although the midge oviposited on all the tested Rubus spp., the midge could develop into an adult midge only on Rubus caesius, R. idaeus, R. caesius x R. idaeus and R. nessensis. However, to enable the midge to oviposit on these Rubus plants, an artificial cut was made in the stems. Stem of other Rubus spp. hardly ever develop natural splits, only Rubus idaeus, therefore these Rubus spp. are not considered to be important in the population development (Nijveldt, 1963).
This is confirmed by McNicol et al. (1983) who showed that R. parviflorus, R. odoratus and F2 plants from the cross R. crataegifolius x R. idaeus are resistant to Resseliella theobaldi when exposed to the pest in an insectary or in the field and, in Rubus idaeus, the amount and extent of natural splits on the canes characteristic of different varieties seem to be the trait that determines their susceptibility to attack by this pest (Pitcher, 1952; Vetek et al., 2006).
However, according to Gratwick (1992), Resseliella theobaldi occasionally attacks loganberry (Rubus x loganobaccus). Pitcher (1952) also reported that larvae develop on this second host.
The midges overwinter as larvae in soil cocoons in the upper 1-4 cm of the soil. They pupate in spring and emerge as adults from April until June (with considerable geographic variability), depending on the soil temperature and local climate (APS, 2017). Depending on geographic region the midge has 3 or more generations per year. Adults of the second generation emerge in late June to August, usually at a time berry cultivars have developed extensive splits in the bark. Numerous eggs are laid in these splits at the base of the canes. The larvae feed on the newly exposed cane cork (periderm). Once fully grown, they drop to the soil and spin cocoons. In northern areas, these larvae go into diapause, but in warmer regions in central and southern Europe, they may produce a fourth or fifth generation. Adult midges are weak flyers and will only travel short distances. Spread between distant plantations is most likely by the transport of cocoons attached to the roots of new planting material (Gordon & Birch, 2017). Raspberry cane midge larvae can quickly overrun newly established plantations if introduced together with infested planting material or soil (Vetek et al., 2006b). In several countries the insect has been introduced mainly with infested planting materials and somewhere with infested soil (Mohamedova, 2017).
[In the responses to the questionnaire, SI commented that the pest was 'widespread'.]
Considering that the pest was narrowly monophagous, and that adults were flying only short distances, the Fruit SEWG concluded that plants for planting should be considered as significant pathway (with some uncertainty).

Yes

Resseliella theobaldi is one of the most important pests of cultivated red raspberry Rubus idaeus throughout Europe, especially on cultivars fruiting on two-year-old canes (Vetek et al., 2006a; Labanowska and Cross, 2008; Mohamedova, 2017). The direct damage by the midge larval feeding is superficial, but the feeding sites become infected by a range of fungi, resulting in a disease called midge blight. Midge blight is restricted to red raspberry cultivars (Gordon & Birch, 2017).

The infection leads to two types of damage.
- First-generation feeding sites develop deeply penetrating lesions, which give rise to conspicuous cankers. Cankered canes may survive and fruit the following year, but they are physically weakened an may be broken by the passage of machinery, fruit pickers or winds during later in the season.
- The damage arising from the second- and third-generation midges is more serious, because larger numbers of larvae are involved and the fungi that colonize the larval feeding sites penetrate and damage the cork layer, which cannot be repaired at this state of maturity. The production of these splits in relation to the emergens of successive generations of adult midges is the predominant factor in this disease. Cane losses of 50-90% have been recorded in areas where the onset of splitting coincides precisely with the midge emergence (Gordon & Williamson, 2017; Gordon & Birch, 2017).

Yield losses frequently exceed 50%, often making the crop unprofitable to harvest (Gordon et al., 2002).

Major

No

Candidate

Evidence of its economic impact is available in the literature.

Candidate

Effective control relies on predicting the accurate date of emergence of the female adult midges and targeting of the insecticide spraying to the base of the primocanes in spring in order to suppress the first generation (Labanowska and Cross, 2008; Tanaskovic and Milenkovic, 2011). Pheromone traps are very useful in monitoring the flight of this insect (Labanowska and Cross, 2008).

Dalman and Malkki (1986) found that the removal of young canes (15-20 cm) reduced the number of larvae and the number of fungal lesions.

Candidate