4 disease symptoms were recorded, namely root gall, root lesion, yellowing leaf and stunting. In which, the symptoms of yellowing trees are encountered on Cat wing trees. Stunted trees were recorded on Duong Quy trees. Danshen and Cross-frame trees caught both symptoms of yellow leaves and stunted plants. On crops, many common symptoms caused by plant parasitic nematodes have been reported, including leaf yellowing, leaf curling, wilting, slow death, stunting and root rot, and on the roots there are nodules (Coyne et al., 2018; Jones et al., 2013; Luc et al., 2005). In China, Taiwan also recorded symptoms of Danshen leaf yellowing, wilting, and stunting caused by the nematode Meloidogyne (Wen et al., 2022; Tsai et al., 2020). Although some symptoms caused by plant parasitic nematodes have been recorded on medicinal plants in Lao Cai. However, the aboveground symptoms of crop and damage caused by nematodes are often nonspecific and are easily confused with other pathogens (Coyne et al., 2018). Therefore, to accurately assess the damage caused by nematodes, it is necessary to base on the symptoms of plants below ground (roots, tubers). Observing the obtained root samples, the symptoms of root knots and swelling were quite high, on 50% Cat Canh tree, 20% Artichoke, 35% Duong Quy, 100% Danshen and Xuyen frame. On the other hand, with rough and swollen root samples, when separated directly under a stereo microscope, the nematodes Meloidogyne spp. (Figure 3.3). Necrotic root symptoms were found on Tuc Tuyen, Party ginseng and Trans-frame plants with a rate of 15-55%. The necrotic root samples obtained the nematode Pratylenchus spp. in roots.
Nematodes like Pratylenchus and Meloidogyne are groups that have a complete life cycle within plant root tissue. After penetrating into the roots, the nematodes will move between the cortical cells, causing the cells to split vertically and reside in the meristem region of the root cortex, starting the nutritional process. Nutrient sites are usually formed in the parenchyma, libe or dermis, and some species penetrate posteriorly to the endoderm, and even deeper into the parenchyma tissues. Therefore, typical symptoms of plants infected with nematodes like Pratylenchus are necrotic roots and lumpy, swollen roots when infected with Meloidogyne spp. (Castillo & Vovlas, 2007; Bernard, 1992). Wen et al., 2022 and Pan et al., 2022 recorded symptoms of Danshen root swelling, lumpiness when infected with Meloidogyne spp. On Duong Quy tree also recorded symptoms of many swollen roots when infected with Meloidogyne spp. (Yao et al., 2010).
On the other hand, the plants Tuc Dang, Artichoke, Duong Quy, Xuyen Khuong, Dan ginseng, Party ginseng use tubers (roots) as medicinal herbs. Therefore, nematodes like Pratylenchus and Meloidogyne cause root necrosis, swelling, and roughness, directly affecting the growth, development, yield, yield and quality of Tuc Tuyen, Artichoke, Duong Quy, Xuyen Frame, Dan Ginseng, Party Ginseng.
Table 2. Disease symptoms on medicinal plants and their relationship to groups of 2 main harmful nematodes

Figure 3.1: Xuyên khung and root galls caused by Meloidogyne

Figure 3.2: Đan sâm and root galls caused by Meloidogyne

Figure 3.3: Meloidogyne in root of Đan sâm 

(Light microscope)