Correlation of bois noir disease with nettle and vector abundance in northern Italy vineyards

Abstract

The phytoplasmas associated with bois noir (BN) tuf-type a are transmitted to grapevines by means of Hyalesthes obsoletus Signoret using Urtica dioica L. as the inoculum source. In the period 2003–2008, a research was carried out in six vineyards of northern Italy where a large amount of nettles in the ditches surrounding vineyards was detected. The aim was to establish the nettle control effects on the presence of H. obsoletus and new symptomatic grapevines. PCR and RFLP analyses showed the presence of the BN tuf-type a phytoplasmas in symptomatic grapevines of all vineyards and in the vector. Weed control strategies along ditches were always associated with decreases in nettle coverage and H. obsoletus numbers. A reduction in the percentage of new symptomatic grapevines occurred in all vineyards except for one vineyard where the least reduction in nettle and H. obsoletus was observed. The decrease in H. obsoletus population was significantly correlated with a decrease in nettles along ditches, and the reduction in H. obsoletus population was correlated with a decrease in incidence of new symptomatic grapevines compared with the incidence before the application of weed control measures. Nettle weeding can reduce the incidence of BN tuf-type a, but weed control costs and impacts need to be considered

In-vineyard population structure of ‘Candidatus Phytoplasma solani’ using multilocus sequence typing analysis

“…The same situation was recorded in a few other studies, although with minor significance (Berger et al, 2009;Mori et al, 2012), maybe because of the low numbers of samples analysed from the same vineyard in most of the other investigations.…”

Relationships between Hyalesthes obsoletus, Its Herbaceous Hosts and Bois Noir Epidemiology in Northern Italian Vineyards

“…Many studies have highlighted a relationship between the abundance of H. obsoletus and its herbaceous host plants and the incidence of BN in vineyards [ 17 , 28 , 29 , 53 , 56 , 57 , 58 , 59 ], but only a few have attempted to relate a measured density of the vector with the increase of newly symptomatic grapevines [ 17 , 58 ]. In the case of annual herbaceous plants, stolbur phytoplasma incidence is directly associated with H. obsoletus density in the same year [ 60 ], whereas in the case of tree plants the symptoms usually occur in the following years’ inoculation [ 61 , 62 ].…”

Identification and ecology of alternative insect vectors of ‘Candidatus Phytoplasma solani’ to grapevine

“…P. solani’ (CaPsol) is Hyalesthes obsoletus 6,7 . Management of its host plants in the vineyards and surrounding areas is therefore considered crucial for BN control 23,24 . The existence of additional vectors has been theorized from the observations that BN incidence is not always correlated to high densities or presence of H. obsoletus populations 12,14,25 .…”