Plant Nematode Diseases Emerge as the Second Largest Phytopathological Threat in China
With global climate change, the evolution of China's cropping systems, and the rapid expansion of high-value agriculture, the incidence of plant nematode diseases has significantly intensified. These diseases have now ascended to rank as the second most severe phytopathological problem in China. Specifically, the root-knot nematodes (Meloidogyne spp.) and cyst nematodes (Heterodera spp.) are the two nematode pathogens causing the most damage to agricultural crops in the country.
Currently, plant nematode diseases pose a severe threat to the production of China's staple and economic crops, including wheat, corn, rice, sweet potato, potato, soybean, vegetables, peanuts, and traditional Chinese medicinal herbs. The cereal cyst nematode (Heterodera avenae) affects an area exceeding 4×106 hm2 in China's winter wheat regions, resulting in a yield reduction of 15%-20% in the north-central part of Henan province. The soybean cyst nematode (Heterodera glycines) consistently impacts an area around 1.33×106 hm2 every year, leading to a general decrease in soybean yield by 5%-10%. In the most severely affected areas, the losses can go beyond 30%, with some regions even facing a total loss of crop. The financial toll from soybean cyst nematode diseases surpasses 600 million RMB. With China's vegetable cultivation spanning over 1.1×108 hm2, the root-knot nematodes are responsible for a typical yield loss of more than 30%. The annual economic loss due to root-knot nematode infestations in vegetables exceeds 3 billion RMB. The maize nematode stunt disease (Trichotylenchus changlingensis) has led to stunted corn growth in an area of approximately 1.33×106 hm2 in Northeast China. Rice root-knot nematodes (Meloidogyne spp.) and rice cyst nematodes (Heterodera elachista) are creating significant challenges in the southern rice-growing areas of China. The potato rot nematode (Ditylenchus destructor) has affected an area exceeding 2×106 hm2 for crops such as potato and sweet potato.
On a general note, plant nematode diseases result in yield losses ranging from 10%-20% in field crops. In areas where the infestation is particularly severe, these losses can escalate to between 30%-50%. In certain regions, the economic losses can even surpass 80%.
Market Demand for Nematocides in China
Based on statistics from 2017, the financial loss attributable to nematode infestations in China approximates to $3.5 billion annually. Alongside the burgeoning trend of plant nematode diseases, the market for nematocides in China has witnessed rapid growth. In 2013, the total market value of nematocides stood at about 458 million RMB. By 2016, this figure nearly doubled, reaching 800 million RMB, and soared further to 1 billion RMB in 2017, with the upward trend continuing over the recent years. Concurrently, China has enforced bans or restrictions on several highly toxic nematocides, such as aldicarb, methyl bromide, and carbofuran. The market vacuum created by the phasing out of these toxic substances is poised to be filled by safer alternatives.
Fig. 1 Chinese registered nematicide products (2023.09.22)
Registered Nematicide Products in China
As of September 22, 2023, a total of 417 nematocide products are being registered in China. Among these, the most registered active ingredients are abamectin, fosthiazate, and abamectin-aminomethyl, with their single agent and mixed agent registrations accounting for over 70% of the total. Other chemical pesticides with a notable number of registrations include carbofuran, metam, and dazomet, representing about 8% of the total registrations. The majority of registered products containing abamectin and/or fosthiazate cater to high-value crops such as cucumbers, tomatoes, tobacco, Chinese yam, ginger, and Chinese medicinal herbs (notably Astragalus). Due to the severe infestations of pine wood nematode (Bursaphelenchus xylophilus) in China, 58 products containing abamectin or abamectin-aminomethyl are being registered for its control. The other two active ingredients registered for pine wood nematode control are ivermectin and marine.
Fig.2 Registered nematicide products on nematodes species (2023.09.22)
In the domain of biopesticides (encompassing microbial pesticides, botanical pesticides, and biochemical pesticides), a variety of active ingredients are involved. These include paecilomyces lilacinus, verticillium chlamydosporium ZK7, bacillus methylotrophicus LW-6, bacillus firmus, bacillus cereus, bacillus nematocida B16, rhodovulum sulfidophilum HNI-1, bacillus thuringiensis, matrine, azadirachtin, and oligosaccharins, primarily used for crops like cucumber, tomato, tobacco, ginger, soybean, kiwi, citrus, pine, and turf.
The highly toxic pesticides, carbofuran and aldicarb, are previously registered for the control of nematodes in peanuts and soybeans, with over twenty products registered so far. However, China is formulating banning measures against carbofuran and aldicarb, and it's envisaged that their market share will likely be replaced by abamectin, abamectin-aminomethyl, and bio-nematicides.
Fumigant nematicides, despite their high usage costs, have 16 registered products. Active ingredients under this category include dazomet (registered for tomatoes, strawberries, ginger, sanqi, tobacco, and flowers), metam (for ginger and cucumbers), AITC (for tomatoes), sulfuryl fluoride (for ginger, tobacco, strawberries, and cucumbers), and chloropicrin (registered for soil fumigation). As for methyl bromide, its use in agriculture has been prohibited since 2019.
Fig.3 Registered nematicide products on crops (2023.09.22)
Opportunities and Challenges in China's Nematocide Market
The increasing incidence of plant nematode diseases in China continues to drive the growth of the nematocide market. With the market's pressing demand for green, efficient, and safe nematocides, China's nematocide market is laden with both opportunities and challenges.
In the case of fumigant nematicides, the cost of utilization for farmers is significant. However, amidst severe nematode infestations, traditional non-fumigant nematicides often falter in providing the anticipated protection due to resistance issues. Under such circumstances, farmers, especially those cultivating high-value economic crops like Chinese medicinal herbs (e.g., Sanqi), and vegetables (e.g., tomato, ginger, strawberry), tend to opt for fumigant nematicides for thorough soil disinfection.
Generally, non-fumigant nematicides are the mainstay in China's defense against plant nematode diseases, and their field application is notably more straightforward than that of fumigant nematicides. However, due to years of fosthiazate and abamectin usage, many nematodes have developed serious resistance, necessitating the introduction and adoption of new nematocides. Furthermore, as highly toxic nematocides are gradually being phased out, there is a pressing need to intensify research on nematocidal seed treatments to identify superior alternative products.
For new non-fumigant nematicides, fluensulfone, introduced to China by Syngenta from Adama, has shown promising results with positive market feedback. Of particular interest are the Succinate Dehydrogenase Inhibitor (SHDI) class of nematicides. Among them, Bayer's fluopyram has been available in the Chinese market for several years and has garnered wide recognition for its superior efficacy. Additionally, Syngenta's new SDHI nematicide, cyclobutrifluram, is also anticipated to be registered and marketed in China soon.
Bio-nematicides, such as paecilomyces lilacinus and verticillium chlamydosporium ZK7, have gradually made their way into the market. Although bio-nematicides might not match the efficacy of chemical nematicides, the burgeoning growth of organic farming in China underscores a promising future for biological pesticides. In terms of China pesticide registration, applicants can apply for the "green channel" to expedite the approval process for their bio-nematicides.
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