The biology of <i>Cixius wagneri</i>, the planthopper vector of ‘Candidatus <i>Phlomobacter fragariae</i>’ in strawberry production tunnels and its consequence for the epidemiology of strawberry marginal chlorosis

Autor/innen

  • P. Salar
  • J.-L. Danet
  • J.-J. Pommier
  • X. Foissac

Abstract

Abstract
«Candidatus Phlomobacter fragariae» is the prevalent agent of strawberry marginal chlorosis (SMC) and is transmitted by the planthopper Cixius wagneri. Because the insect vector biology was unknown, a field experiment was set up to determine if it was able to reproduce on strawberry plants, to determine the number of insect generations per year and the ability of nymphs to transmit SMC. During spring 2004, 80 C. wagneri adults were delivered into 4 small insectproof tunnels containing 30 healthy plants. Fifteen percent of the delivered insect population were carrying the pathogen. In October 2004, only 3 young L1 instar nymphs were found in the first tunnel, demonstrating there were no new insect generations during the summer. In April 2005, 330 C. wagneri of early L1 to late L5 nymph instars were collected at the roots of the plants,clearly indicating that a single insect generation had overwintered as larvae andemerged at the following spring. All instars were shown to carry ‘Ca. P. fragariae’ (70 to 75 % of the larvae) and were able to transmit SMC as assessed by transmission assays. An insecticide treatment was applied in March 2005 in a third tunnel and a fourth tunnel was kept as a control. More than 120 C. wagneri adults were collected in the control tunnel 4 in June 2005 confirming that an insect generation arose in the tunnel, whereas no insects could be found in the treated tunnel 3. All plants were kept for two years, surveyed for symptom expression and tested for ‘Ca. P. fragariae’ infection by 16S-PCR. Results indicated a reduced mortality and SMC incidence in tunnel 3, and a higher mortality and SMC incidence in tunnel 2 than in tunnel 1, attesting that C. wagneri larvae had spread SMC and that an early insecticide treatment could control the disease.

Keywords: Phloem-restricted bacteria, planthopper, insect vector, Fragaria x ananassa

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Veröffentlicht

2010-09-17