Pest risk assessment of Radopholus similis for the EU territory

The Panel on Plant Health performed a pest risk assessment on Radopholus similis, the burrowing nematode for the EU. The quantitative assessment focused on entry, establishment, spread and impact on tropical and subtropical ornamental host plants, the main pathways for entry of R. similis into the EU. Infested consignments are expected to enter the risk assessment area on ornamentals under all scenarios. For citrus, which is a closed pathway for entry, outdoor establishment was assessed. Establishment may only take place after successful transfer from ornamental plants to citrus production systems. This event is called ‘shift’ in this assessment, to indicate that this is an unusual transfer. It has been estimated that establishment of this nematode in the open field in the EU citrus production areas under current temperatures is possible in most parts of the citrus production area in the EU. Temperature conditions will prevent the nematode from establishing only in the northernmost citrus areas and at higher altitudes in the south. Host plants for planting originating from infested places of production (greenhouses) within the risk assessment area are considered the main pathway for spread within the risk assessment area. Under current climatic conditions, the population of R. similis is not expected to reach damaging population levels in the open field. In case of increased temperatures due to global warming, the nematode population may reach damaging levels in very few places outdoors. Currently, main impact is considered for ornamental greenhouse production in the risk assessment area. Impact will be either caused by direct plant growth reductions or loss due to phytosanitary measures applied on regulated plants. Despite the fact that R. similis is globally considered as one of the most destructive plant parasitic nematodes, the impact in the risk assessment area is considered low.

Tomato (Solanum lycopersicum) and root-knot nematodes (Meloidogyne spp.) – a century-old battle

The encounter betweenMeloidogynespecies and tomato is many centuries old.Meloidogynespecies are known to cause high levels of economic loss worldwide in a multitude of agricultural crops, including tomato. This review was initiated to provide an overview of the damage potential ofMeloidogynespp. on cultivars of tomato (Solanum lycopersicum), and to compile the different studies done on the management ofMeloidogynespp. on tomato with particular emphasis on theMiresistance gene. Numerous studies have been conducted to assess the damage potential of root-knot nematode on various tomato cultivars; its yield loss potential ranges from 25 to 100%. A range of management options from using synthetic nematicides to soilless cultures have been tried and are available for managingMeloidogynespp. Resistant commercial cultivars and rootstocks carrying theMigene have been used successfully to manageMeloidogyne incognita,M. javanicaandM. arenaria. However, virulent populations have been detected. Relying on a single root-knot nematode management strategy is an outdated concept and different management options should be used in an integrated management context by considering the whole system of disease management. In future management ofMeloidogynespecies, care must be taken in directly extrapolating the tolerance limit determined elsewhere, since it is affected by many factors such as the type of initial inoculum and physiological races ofMeloidogynespp., environmental conditions, types of cultivars and experimental approaches used.

Life cycle and mating behavior of Zygotylenchus guevarai (Nematoda: Pratylenchidae) on excised Petroselinum crispum roots

The life cycle and mating behavior of Zygotylenchus guevarai were observed in vitro on excised roots of Petroselinum crispum in gnotobiotic culture. Eggs hatched into juveniles whose appearance and structure were similar to those of the adults. Juveniles grew in size and each juvenile stage was terminated by a molt. Z. guevarai had four juvenile stages with the first molt occurred outside the egg shortly after hatching. After the final molt the juveniles differentiated into adult males and females. Mating was required for reproduction. After mating, fertilized females began to lay eggs. The life cycle from second stage juvenile to second stage juvenile was completed in 43 days.