A risk assessment of Bemisia tabaci and its quarantine status in Sweden

Sammanfattning: Bemisia tabaci, the cotton whitefly, is a polyphagous pest of numerous important crops grown in subtropical and tropical areas and in greenhouses. It is considered the most important member of the whitefly family (Aleyrodidae), from an economic point of view, due to its polyphagy and ability to transmit viruses. Sweden is termed a protected zone against B. tabaci. A protected zone is an area within the European Union where a harmful organism has not been established yet as in other parts of Europe. In this protected zone the harmful organism is actively controlled by officials. Produced commodities that are imported or traded within EU to a protected zone are obligated to be free from the quarantine pest. Also commodities traded within a protected zone for continued production have to be free from the quarantine pest. A pest risk assessment is made with the aim to evaluate the threats an establishment of B. tabaci would pose to the Swedish greenhouse production and the sustainability of the protected zone is discussed. This is a literature study with qualitative interviews, with eight interviewees which are all important actors concerning this issue. I chose to conduct qualitative interviews, as the aim and the addressed problem are complex and can not be answered in a quantitatively manner. The result showed that the main feared threats that an establishment of B. tabaci pose are eradication problems as it is readily developing insecticidal resistance and the spread of feared vectored viruses into vegetable greenhouses. On the question if the protected zone should be maintained the opinions from the interviewees were diverse. The administrative officer at the Plant Protection Service thought the protected zone to be of advantage for the growers as it is an extra guarantee of importing healthier material. The expert on greenhouse from the Plant Protection Centre at the Swedish Board of Agricultural pest also identified the benefit with importing healthier material, but judged the risk of virus spreading into vegetable greenhouses as small. The expert in plant virology stated that the risk of virus spread into vegetable greenhouses would be higher with viruses with both ornamental and vegetable hosts. The advisor in production of ornamental plants thought that the protected zone is not to any practical meaning for the ornamental growers, as B. tabaci is not a serious problem for them. The grower of ornamental plants said that the decision of the protected zone was taken in loyalty towards the vegetable growers and thought that the protected zone will be phased out in a couple of years. The cutting producer thought the protected zone was unnecessary and due to an overestimation of the risks. The tomato grower and advisor on production of greenhouse vegetables believed it to be important to prevent establishment of new serious pests.