Potential distribution and biosecurity risks from three economically important plant - parasitic nematodes

The plant-parasitic nematodes (PPNs), Heterodera zeae, Hirschmanniella oryzae and Meloidogyne graminicola, are economically important pests of major grain crops. Each of these species is still absent from the majority of countries, so there is great concern about their spread. However, the areas particularly at risk of invasion and the potential global distributions of these nematode pests are yet to be identified. This paper identifies these areas, together with the main factors that could facilitate establishment in new areas using CLIMEX models. Parameterised using published studies of species phenology and global species distributions, the models correctly identified the areas invaded recently by M. graminicola and H. zeae. The vast majority of the areas of the world under wheat, rice and maize were identified as suitable for the nematodes. The nematodes are not yet established in many of these areas, suggesting that biosecurity measures may be particularly warranted to prevent the spread of these species to the new suitable areas identified. Intensive cropping systems under irrigation were identified as being at much greater risk than rain-fed cropping systems. The potential detrimental effects from introduction and local spread of PPNs in irrigation water could undermine suggested potential gains from using irrigation to increase world food production and meet increasing demand. These results mean that biosecurity measures for PPNs are justified