Transmission of German grapevine yellows (Vergilbungskrankheit) by the planthopper Hyalesthes obsoletus (Auchenorrhyncha: Cixiidae)

Research Not

Molecular characterisation of grapevine yellows associated phytoplasmas of the stolbur-group based on RFLP-analysis of non-ribosomal DNA

Grapevines, alternative host plants, and vectors from different viticultural areas of Germany were surveyed for the presence of stolbur-group phytoplasmas that are associated with grapevine yellows. Isolates from these field samples and periwinkle isolates of stolbur were characterised by RFLP-analysis of non-ribosomal DNA fragments using a combination of 6 polymorphic primer-enzyme combinations. Three of the 5 different restriction profiles that could be distinguished were found in grapevine and other field samples of plants and insects. A previously unknown isolate was detected in grapevine, vectors and the newly identified herbaceous host Calystegia sepium. The further analysis of the phylogenetic relationship between the 5 RFLP groups revealed a close relationship between two of the isolates associated with grapevine yellows which were also found in the two Convolvulaceae Convolvulus arvensis and Calystegia sepium. The third isolate which was detected in grapevine and stinging nettle Urtica dioica is more closely related to a periwinkle isolate obtained from Lavandula officinalis than to the other two grapevine yellows isolates. Based on the data of the field survey a specific association of the three isolates to different alternative host plants is discussed.

Control of Hyalesthes obsoletus nymphs based on chemical weeding and insecticides applied on Urtica dioica

Bois noir is a grapevine yellows disease associated with Candidatus Phytoplasma solani and transmitted to grapevines by means of the planthopper Hyalesthes obsoletus Signoret (Homoptera, Cixiidae). The overwintering nymphs of the vector acquire the phytoplasma feeding on roots of herbaceous plants, including Urtica dioica L. (stinging nettle). In German and Italian vineyards the possibility to control the H. obsoletus nymphs feeding on stinging nettle roots using chemical weeding and insecticides was investigated. In particular, the effect of herbicides, applied in autumn and in different spring timings, and neonicotinoid insecticides on vector adult emergence was evaluated. Trials conducted to control nettle with glyphosate or a mixture of glyphosate+flazasulfuron significantly reduced the density of emerging adult vectors. The efficacy of herbicides was highest when they were applied in autumn or in early spring with the nymphs not older than the fourth instar. Herbicides applied too close to the beginning of the emergence of adults reduced numbers only during the late part of the planthopper flight-period. Although neonicotinoid insecticides applied in early spring gave efficacy comparable to herbicides, their use is not advisable for the negative side effects on non-target arthropods (e.g. honeybees). Overall, the combination of cultural practices and accurately timed applications of selective herbicides might help to refine the current Integrated Pest Management recommendations for controlling nettle, H. obsoletus and consequently bois noir.

Transmission of grapevine yellows by Oncopsis alni (Schrank) (Auchenorrhyncha: Macropsinae)

Research Not

Efficacy of Metarhizium anisopliae against Hyalesthes obsoletus (Auchenorryhncha: Cixiidae)

Research Note

Preliminary results on population dynamics and host plants of

This work dealt with Hyalesthes obsoletus, which is the only known vector of Bois noir disease in grapevine. Investigation centered on its flight activity and occurrence on bindweed and stinging nettle and, to a lesser extent, hedge bindweed and dead-nettle in North-Eastern Italy. The survey underlined the importance of bindweed in the insect lifecycle in Northern Italy, where only data from stinging nettle had previously been recorded. H. obsoletus nymphs were found for the first time on the roots of dead-nettle, which proved to be a new host plant. The first observation in Italy of nymphs on hedge bindweed roots was also recorded

A rapid and inexpensive RNA-extraction method for high-throughput virus detection in grapevine

The extraction of RNA from grapevine tissue is a crucial step for virus diagnostics via multiplex reverse transcription-polymerase chain reaction (mRT-PCR). Conventional methods are either time-consuming or expensive when convenient extraction kits are used. Here we present an easy, but reliable extraction method that fulfills the requirements of epidemiological research (high sample throughput with maximum accuracy). A further advantage of the protocol beside the low costs is the absence of harmful chemicals like phenol or chloroform and the possibility to manage 'high-throughput' extractions and analyses

Diversity of grapevine yellows in Germany

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Comparison of rapid detection assays for grapevine leafroll disease associated closteroviruses

Three rapid detection assays (ELISA, dsRNA analysis and ISEM) were compared for their sensitivity, specificity, and simplicity in the detection of grapevine leafroll associated closteroviruses (GLRaV). Each was found to have advantages and disadvantages for routine testing. ELISA is sensitive and easy to use, but different antisera are needed to detect different GLRaV types. Because mixing or blending of antisera can produce good results in a single ELISA test, each antiserum does not need to be used separately unless it is important to determine the type of GLRaV present. DsRNA analysis can detect all the types of GLRaV tested but has a relatively low sensitivity and is labor intensive, which makes it unsuitable for testing large numbers of samples. Furthermore, dsRNA does not give unequivocal diagnosis of GLRaV infections. ISEM is sensitive and rapid. However, like ELISA, this technique requires an antiserum to each GLRaV type tested and an electron microscopy. Our recommendation is that ELISA should be used with multiple antisera for large scale testing programs. Samples for which ELISA results are inconclusive should be retested with ISEM and/or dsRNA. When the disease status of an individual sample must be determined conclusively, a few grams of tissue should be processed to concentrate the virus and then subjected to ELISA and examination by electron microscopy with negative staining. A dsRNA analysis should be carried out as well