Macropsis mendax as a vector of elm yellows phytoplasma of Ulmus species

Abstract

A 3-year study was carried out in north-east Italy, the site of recent elm yellows epidemics, to identify vectors for the elm yellows phytoplasma. Using PCR analysis, Ulmus minor and Ulmus pumila , each with and without symptoms, were positive for the elm yellows phytoplasma. Macropsis mendax , a univoltine and monophagous leafhopper, was shown to be the vector of the elm yellows-associated disease agent. PCR analyses demonstrated that the insect was infected both in natural conditions and in the screenhouse after acquisition-feeding on infected elm plants. Groups of M. mendax , collected from naturally infected elm trees, transmitted elm yellows phytoplasma to elm test plants. In nature, Alnus glutinosa trees affected by alder yellows were found in the surroundings of yellows-affected elm trees; the associated disease agent of alder yellows was transmitted under controlled conditions from alder to elm test plants by grafting.

Scientific Opinion on the pest categorisation of Elm phloem necrosis mycoplasm

“…It is also useful to stress that there are reports of phytoplasmas other than Ca Phytoplasma ulmi on elm trees (Carraro et al, 2004;Gao et al, 2011). These might cause some confusion in a preliminary diagnostic step.…”

“…This is why it was hypothesised that the disease originated from Europe (Boudon-Padieu et al, 2004). The disease is present in at least four countries in the PRA area, but reports usually mention a limited distribution (Pisi et al, 1981;Carraro et al, 2004). There is a lack of extensive surveys that would allow us to assess precisely the distribution and impact of the pest in Europe.…”

“…The leafhopper Macropsis glandacea (=mendax) has been identified as a vector in Italy (Carraro et al, 2004); other species (Allygidius furcatus, Cixius sp., Iassus scutellaris) have been trapped in the field in France and found to be PCR positive to an EY-group phytoplasma, although not proven to transmit it (Boudon-Padieu et al, 2004).…”

“…American or white elm Susceptible-phloem necrosis, foliar epinasty, yellowing, leaf fall and mortality Braun and Sinclair, 1979;Sinclair, 1972;Sinclair, 2000 Ulmus chenmoui Field elm Witches' brooms, stunting Boudon-Padieu et al, 2004;Braun and Sinclair, 1979;Carraro et al, 2004;Conti et al, 1987;Mittempergher, 2000;Piese and Juretić, 1999;Pisi et al, 1981;…”

“…Three other species, Cixius sp., Iassus scutellaris and Allygidius furcatus, were found infected in the field in France with an EY-group phytoplasma (Boudon-Padieu et al, 2004), although these species have not so far be proven to transmit the disease. The leafhopper Macropsis mendax was identified as a vector in Italy (Carraro et al, 2004).…”