Susceptibility of raspberry cultivars to the raspberry cane midge [Resseliella theobaldi Barnes]

Abstract

During the 2004 growing season, five raspberry cultivars were evaluated in terms
\nof their susceptibility to the raspberry cane midge (Resseliella theobaldi Barnes). The
\ntrial was carried out at Berkenye, Nógrád County, Hungary. The cultivars evaluated
\nwere ‘Rubaca’ from Germany, ‘Fertődi Zamatos’ from Hungary, ‘Tulameen’ from
\nCanada, and ‘Autumn Bliss’ and ‘Golden Bliss’ from the United Kingdom. Every
\nother week, twenty-five split primocanes of each cultivar were randomly collected for
\nlaboratory examination. Data recorded for each cultivar included the mean number of
\nlarvae, the mean split length, and the mean extent of bark peeling per primocane.
\nPearson’s linear correlation coefficients were calculated for the correlations between
\nthe annual mean number of larvae per primocane on the one hand, and the annual
\ncumulative mean split length per primocane and annual mean extent of bark peeling
\nper primocane on the other hand. There was a weak correlation between annual mean
\nnumber of larvae and annual cumulative mean split length, and a stronger correlation
\nbetween annual mean number of larvae and annual mean extent of bark peeling.
\nAnnual mean number of larvae per primocane and annual mean extent of bark peeling
\nper primocane were both highest in ‘Rubaca’, which means that the number of larvae
\nper cane largely depends on the extent of stem peeling, although longitudinal splitting
\nmay also play a role. Therefore, cultivars with hardly any bark peeling and few and
\nsmall longitudinal splits can be presumed to be less susceptible to infestation by the
\nraspberry cane midge. Using these criteria, the least susceptible of the five cultivars
\nevaluated would be ‘Tulameen’ and ‘Fertődi Zamatos’. Further research is needed to
\nconfirm this conclusion and to gather data on other factors which affect cultivar
\nchoice for new plantations, including winter hardiness, and susceptibility to cane
\ndiseases.