In Europe, the stem and bulb nematode Ditylenchus dipsaci has been listed as a quarantine pest by EPPO: without any control, it may cause complete failure of alfalfa crops. Movement of nematodes associated with seeds is considered to be the highest-risk pathway for the spread of this pest. Since the 2010 official withdrawal of methyl bromide in Europe, and in the absence of any alternative chemical, fumigation of contaminated seed batches is no longer possible, which makes the production of nematode-free alfalfa seeds difficult to achieve and leads to unmarketable seed batches. Thermotherapy is being considered as a realistic alternative strategy, but its efficiency still remains to be validated. The combination of the currently available methods (i.e. use of resistant cultivars, seed production according to a certification scheme, mechanical sieving, seed batch inspection) could significantly reduce the likelihood of seed contamination. However, it does not guarantee a total eradication of the nematode. Although it is already widely distributed all over Europe, reclassification of D. dipsaci as a regulated non-quarantine pest to reduce the possibility of further introductions and the rate of spread of this pest appears to be a risky strategy because of the lack of up-to-date documented data to evaluate damage thresholds and determine acceptable tolerance levels.
The invasive pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the most serious threats to pine forests across the world. Detected in Europe in 1999, it has largely spread despite containment measures. Following the European Union regulations, the requested eradication measure is to fell, remove and dispose of all susceptible plants within a clear‐cut zone (CCZ) of a radius of 500 m around any infected tree. This measure is controversial since its effectiveness is questioned. An individual‐based model, describing the dispersal of the nematode vector and the nematode transmission, was used to estimate the relationship between the radius and the effectiveness of the CCZ at eradicating the PWN. Clear‐cutting of a 500‐m radius is poorly effective in non‐fragmented pine forests since it reduces the number of PWN transmissions by only 0.6%–11.5%. To significantly reduce the number of transmissions, the radius should be between 14 and 38 km, which is not technically nor ethically feasible. Policy implications. Our results, based on model simulations at a fine spatial scale, prove that clear‐cutting susceptible trees 500 m around any infested tree—as requested by EU regulation to eradicate the PWN—is not effective in large and continuous pine forests. Instead, strengthened surveillance and sanitation felling could be explored.
Among plant‐parasitic nematodes (PPNs), the species Meloidogyne chitwoodi constitutes an important agricultural issue and is listed as a quarantine species in the EU. This study investigated whether PPN communities can affect the establishment and expansion of M. chitwoodi during a simulated introduction. An original experimental design was developed on potato in the glasshouse involving four PPN communities derived from a single natural one that was initially grown on different host plants. Meloidogyne chitwoodi was inoculated at two different densities (50 or 1000 second‐stage juveniles (J2) per pot). After 4 months, M. chitwoodi was more abundant in the community showing a low overall abundance of PPNs, decreased in the other PPN communities and failed to establish in five pots out of 80. Results showed that establishment – even starting from a very low inoculum – can occur in all communities even if indigenous PPNs in the community affect the expansion through interspecific competition. The reverse interaction was also observed as PPN taxa were generally less abundant in the 1000 M. chitwoodi J2 inoculation treatments. The proportion of M. chitwoodi males produced was higher in the community showing low overall PPN abundance, suggesting a strong sensitivity of M. chitwoodi to intraspecific competition. The presented results suggest that a low abundance of indigenous PPNs presents a higher risk of expansion of M. chitwoodi even if the introduced inoculum is low.
Official analyses undertaken in the framework of an official survey, or import controls need reliable results. This can be achieved by using validated methods. For morphological tests, this validation process is rarely illustrated despite guidance provided in EPPO PM 7/98 (1) Specific requirements for laboratories preparing accreditation for a plant pest diagnostic activity. This paper presents validation for the morphological identification of Bursaphelenchus xylophilus, with the evaluation results of published identification keys and of internally designed identification keys at B. xylophilus group and species levels. For published identification keys some criteria were shown not to be reliable for routine use: excretory pore position and number of caudal papillae. The key designed in the laboratory for xylophilus group identification was shown to be sensitive and specific when one male and one female were observed. The key designed for B. xylophilus species identification is sensitive, specific and reproducible if only one female of B. xylophilus is observed. The tools designed were validated as simple and reliable for routine analysis. The advantages and limitations of the validation process for morphological tools are discussed for process improvement.
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