Exotic and non-exotic nematode plant pests: a potential threat to the Italian agriculture and environment.
Italian crops are damaged by many plant parasitic nematodes widely distributed in the country. Other species established in very limited areas have the potential to become major economic pests if their movement is not prevented. These species include the root-knot nematodes Meloidogyne ulmi on elm in Tuscany, M. artiellia on winter cereals, crucifers and legumes in Apulia and Basilicata, the cyst forming nematodes Globodera t. tabacum on eggplant and tobacco in Campania, Heterodera betae on sugar beet in Piedmont, H. daverti on carnation in Campania, H. glycines on soybean in Lombardy, H. latipons on winter cereals in Veneto, H. hordecalis on graminaceous crops and H. mediterranea on Pistacia lentiscus both in Apulia, H. trifolii on carnation in Liguria and Tuscany, and Aphelenchoides besseyi on rice in Piedmont, Lombardy, Veneto and Emilia Romagna. Some of these species are indigenous such as M. artiellia and H. mediterranea. Others are exotic such as A. besseyi and H. glycines. The geographical location of the Italian peninsula makes Italian agriculture and environments vulnerable to the accidental introduction of exotic nematode plant pests from many European and African countries which have been trading partners with Italy for centuries. Exotic nematode pests that may be introduced from European countries include: Meloidogyne chitwoodi and M. fallax, two serious pests of potato, M. naasi, a pest of cereals, M. lusitanica and M. baetica, two pests of olive trees, and Bursaphelenchus xylophilus, a very damaging nematode of pine trees, recently detected and established in Portugal. Pratylenchus goodeyi, a typical nematode of banana, which is widespread in East Central Africa and Asia, has been detected in Crete, Canary and Madeira islands, and also on grape in Australia. This lesion nematode may be also introduced into Italy with uncertified propagative ornamentals and other plants. Rotylenchulus reniformis, another polyphagous species reported from Spain, is widespread in Africa, the Americas and Asia. The intensification of global trade of agricultural products has increased also the risks of introducing exotic nematode plant pests from the Middle and Far East, Africa and the Americas. The most economically important of these nematodes are the giant race of Ditylenchus dipsaci pest of broad bean, and Heterodera ciceri, a pest of legumes, occurring in the Middle East; Ditylenchus angustus, Heterodera oryzae, Hirschmanniella oryzae and Meloidogyne graminicola damaging pests of rice in the Far East, Heterodera zeae to corn, and the root knot nematodes, Meloidogyne citri, M. fujianensis, M. indica, and other related species that infect citrus in China. Meloidogyne ethiopica and M. mayaguensis are emerging damaging pests to many annual and perennial crops in Africa and the Americas. The introduction of these pests may occur with the trade of uncertified ornamentals. The same pathway of introduction may be open for Nacobbus aberrans, a pest of potato and other annual crops, and Radopholus similis (citrus biotype), a pest of citrus, in the Americas. There are potential risks of introducing ectoparasitic nematode species, including vectors of plant viruses of the Xiphinema americanum Cobb group. However, these risks are lower for ectoparasitic species than for endo and semiendoparasitic nematodes.