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Development of efficient control strategies against psyllid species vectoring european fruit tree phytoplasma

Efficient control strategies against phytoplasma vectoring psyllids will be established by the help of molecular markers to study their life cycle, by determining the transmission parameters and by developing disturbation strategies.

In the past years, phytoplasma diseases caused important economic losses in the apple production in Southwest GERMANY, Northern ITALY and SWITZERLAND as well as in apricot production in FRANCE, ITALY, CZECH REPUBLIC and in SWITZERLAND. Fruits of infected apple trees cannot be commercialised because of small size and inferior taste. Infected stone fruits like apricot, peach or Japanese plum die within a few years after infection, depending on the age of the tree. Two distinct phloem-restricted, non-cultivated Mollicutes are associated with these diseases: apple proliferation (AP) phytoplasma in apple and European stone fruit yellows (ESFY) phytoplasma in stone fruits. Recent results demonstrated that one or more psyllid species transmit these phytoplasmas: Cacopsylla picta and Cacopsylla melanoneura transmit AP phytoplasmas, Cacopsylla pruni transmit ESFY phytoplasmas. It cannot be excluded that other psyllid species also play a role in the transmission of these phytoplasmas. The above psyllid species hibernate as adults on unknown plants and multiply on apple and Prunus from early spring to early summer. Overwintering adults as well as springtime generation are infectious under experimental conditions. Although key parameters in the natural phytoplasma transmission by these vectors are still unknown, insecticide treatments have been started in apple trees in ITALY and in apricot trees in FRANCE. However, the success of these treatments was rather limited under these conditions. Up to now, no phytoplasma-resistant cultivars exist for apple, apricot, peach and Japanese plum, respectively. As no curative treatments can be employed to save infected trees, the only means to fight against these diseases is to prevent the spread of the phytoplasmas to healthy trees by their insect vectors. The objective of the present project proposal is therefore to gain more information about the phytoplasma spread by the psyllids and to develop innovative control strategies based on psyllid disturbation in order to avoid unwanted insecticide treatments. Furthermore, the research on these psyllids is hampered by the morphological similarity of the Cacopsylla species. Only specialised entomologists can differentiate these species. Therefore, the project also aims to develop an electronic key for easy determination of these psyllids by plant protection services, skilled growers or researchers. Molecular taxonomic markers for the vectoring species will be developed in order to enable a mass screening of psyllids by PCR (Polymerase Chain Reaction), to detect the phytoplasmas and to identify the vector species in one step. Thus, the project proposal consists of the following work packages (WP): WP1) Elucidation of the complete life cycle of the above psyllid species Plant hosts of the psyllids, which might be alternative host plants for the phytoplasmas as well, will be searched in summer during the migration phase and in winter during hibernation. WP2) Molecular markers will be developed to identify the vector species by specific PCR primers and to differentiate vector populations with putative different transmission efficiencies. WP3) Establishment of an electronic key for the determination of psyllid species. WP4) Identification of alternative host plants for the phytoplasmas (s.WP1) WP5) Determination of the transmission parameters of the above psyllids The transmission efficiencies of overwintering adults and springtime generation will be tested, the minimum acquisition as well as transmission period will be determined as well as the latency period in adults and larvae. WP6) Development of prognostic systems, for the apparition of infectious psyllids, under varying climatic conditions. WP7) Development of innovative control strategies, against the vectoring psyllids. The concept of 'attrack and kill' will be tested with chromatographic traps. Based on the results of the above workpackages an overall concept for the control of phytoplasma vectoring psyllid species in apple and stone fruit orchards will be defined which is, first, based on a risk assessment (when is it necessary to control) and, second, based on efficient control strategies (where and at what time point is it necessary to control). Innovative control methods will help to protect the environment and should, if possible, also be applicable to organic farming. Keywords: phytoplasma diseases, psyllid vectors, control strategies.
Acronym: 
PSYLLID VECTORS
Project ID: 
3 233
Start date: 
01-01-2005
Project Duration: 
47months
Project costs: 
800 000.00€
Technological Area: 
Genome Research
Market Area: 
Viticulture and Fruit Tree Cultivation

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