Pin Nematode Slow Decline of Anthurium andraeanum, a New Disease Caused by the Pin Nematode Paratylenchus shenzhenensis

High population densities of the plant-parasitic nematode Paratylenchus shenzhenensis have been observed in association with stunted anthurium in Shenzhen, Guangdong Province, China. P. shenzhenensis is now recognized as a new pathogen that causes severe damage to anthurium. Commercial fields of anthurium infected by P. shenzhenensis present a patchy distribution of plants that are usually stunted and in decline and have yellowing leaves. Roots that are heavily infected by this nematode present brown, dark-brown, or black rot, and the entire root mass is often destroyed. In this study, a method of culturing P. shenzhenensis on carrot disks was established, and the effects of temperature and time on the reproduction rate (Rr = final number of nematodes/initial number of nematodes) of this nematode were assessed. The optimum temperature for culturing P. shenzhenensis on carrot disks is 25°C and, after inoculation with 20 females and 10 males at 25°C for 10 weeks, Rr reached 3,834. At the optimum temperature, a suitable extension culture time or an increase in initial inoculum density will improve the reproductive efficiency of P. shenzhenensis. Koch’s postulates were fulfilled by inoculating P. shenzhenensis on the roots of anthurium and demonstrating the pathogenicity of the nematode. Histological analyses showed that P. shenzhenensis feed endoparasitically on the roots of anthurium; whole nematode bodies were observed in the outermost epidermal cells and root hairs, and the cell walls and middle lamellae were partially dissolved because of nematode migration and feeding.