Phytosanitary status of organisms harmful to plants and plant products (STATREGO)

The aim of this project is to determine the correct phytosanitary status of 13 well-defined pest insects, one harmful plant fungus, one nematode and one plant virus, and that specifically for the Belgian territory. Taken as a whole, we suspect that they can pose a threat to (parts of) fruit and vegetable growing and tree nurseries. The problem is that so far no extensive survey has been set up in Belgium for these diseases and pests and that there is no data about their status with us. In addition, no systematic scientific literature research has yet been carried out that provides additional information on biology, host plants, geographical distribution and the introduction and establishment potential. This project changes that.

For each of the target organisms we choose relevant agricultural and horticultural companies and risk sites, which we monitor intensively during three growing seasons to map out their presence (the status of the disease or pest) on an objective basis. Specifically, the insects are Popillia japonica, Thrips setosus, Aromia bungii, Polygraphus proximus and 7 non-European Tephritidae (in fruit and vegetable cultivation). We monitor them using different types of traps and sampling of suspect plant material. In addition, we set up a survey around the nematode Meloidogyne mali, initially specifically in elm plantings, but with special attention to plantings with trees from the former Dutch breeding program against Dutch elm disease. When presence is established, we also plan sampling of other possible host plants in the area. For the fungus Diplocarpon mali we first develop an optimized survey technique, including a specific quantitative PCR (qPCR). We plan the survey itself in apple cultivation, based on symptoms and ascospore detection. We also investigate the effectiveness of the fungicides registered in apple cultivation against D. mali. And we look at the susceptibility of the main apple varieties for this fungus. The tomato leaf curl New Delhi virus survey focuses mainly on Cucurbitaceae (courgette, cucumber, melon) and Solanaceae (tomato, pepper) in greenhouses. We link this survey to outbreaks of the tobacco whitefly Bemisia tabaci (the vector of the virus).

During this project, two target organisms in Belgium were locally identified: Thrips setosus and Meloidogyne mali.T. setosus was identified at the end of 2018 on one farm in Destelbergen with hydrangea in a greenhouse. One year later, this thrips species was also identified outside the greenhouse, more specifically on zucchini in a vegetable garden. For the time being, the occurrence of T. setosus in Belgium seems to be limited to this grower and the immediate surroundings. At the time of this first detection of this thrips species in Belgium, it had already been removed from the EPPO Alert list. M. mali was found in Grimminge ( Geraardsbergen, Belgium) at the location where elms from the former Dutch breeding program against elm disease were planted. On several trees severe lump formation was observed on the roots. These elms were probably already planted at the end of the 1970s. Of these elms, only cutting material was used and the trees are still at the original planting site. As M. mali was not found in Belgium, the spread is probably limited to one location.

With regard to Diplocarpon mali, all techniques were developed for the survey and the survey itself was carried out on a very extensive number of leaf samples. A number of air samples were also analyzed for the presence of ascospores. The pathogen was not detected, so the current status is considered as "absent: no pest records". The role of ascospores in the cycle of D. mali is probably limited in our region. The inoculation tests on host susceptibility did not give clear lesions.

For the other target insects, the existing monitoring method was further refined in the course of this project. For P. japonica and P. proximus, the method (trap type and lure) is now fully developed. For A. bungii, a selective monitoring method was only obtained in the course of the last monitoring year, but could no longer be tested. For non-EU Tephritidae, specific attractants are missing for many target species, which requires non-selective monitoring. Air and seaports, as well as auctions and composting facilities, are important sites at risk and were initially overlooked. As far as possible, monitoring was carried out for each target organism throughout Belgium and in each province.