Stolbur phytoplasma has been causing major economic damage to potatoes, a number of vegetable crops (celery, Chinese cabbage) and grapevines for several years. Infected potato plants produce fewer and smaller tubers with a rubbery consistency, which sprout in threads and have less favourable processing and storage properties. Infected celery plants become discoloured and the plants collapse. On diseased vines, the leaves curl downwards and become discoloured, the shoots or bunches wither or dry out.
Stolbur phytoplasma is transmitted to all crops via a complicated cycle that includes weed species as intermediate hosts and cicadas as vectors. Two weed species, field bindweed and stinging nettle, currently play a role as intermediate hosts in Austria. As a vector insect, the bindweed cicada (Hyalesthes obsoletus) is the main vector in all crops.
These cicadas develop one generation per year, the animals become infectious as larvae on the weeds, only live above ground as adult cicadas and transmit the disease to the crops during the flight period from around the beginning of June to the beginning of August.
Control is difficult as the relevant weeds are generally difficult to control. Moreover, the problem areas are often not in the crop but mostly outside, on roadsides, in fallow land, on embankments, etc. where control is not possible. Over the entire flight period, there is a constant influx into the crops, because in many cases the adult cicadas do not remain on their weed hosts outside the crops, but fly to the neighbouring crops in the event of disturbances (e.g. wind, drought).
To date, there are no satisfactory control strategies in either wine, vegetable or potato cultivation.
In the three-year sector project, the vector insects and their larvae are monitored over the course of the year. Together with soil and climate data, a warning service could be set up and the existing forecasting model could be evaluated and adapted for eastern Austria. Research is also being conducted into whether the transmitting cicadas are amenable to biological control (e.g. insect-pathogenic fungi) in the larval stage.
The extent to which induced resistance (i.e. stimulation of plant defences by chemical substances or microorganisms) increases the tolerance of the crops is also being investigated. Another approach is the possible control of cicada infestation by means of sacrificial strips, i.e. by surrounding crops with high growing non-hosts for the cicadas, e.g. (winter) cereals.
Different greening management (sowing, rolling, mulching, high or low greening, etc.) are evaluated with regard to suppression of field bindweed and reduction of cicadas. The field trials are accompanied by comprehensive molecular biological research and food technology studies.
Project manager at the W&O RTD: Dr. Monika Riedle-Bauer
More information:
Strategien zur Eindämmung von Stolbur-übertragenden Zikaden (ecoplus.at)
Stolbur Phytoplasma, HBLA und Bundesamt für Wein- und Obstbau Klosterneuburg (weinobst.at)asma.html