What pesticide should be used for Panax notoginseng blight, viral disease, and black spot? What are the disease symptoms?
Panax notoginseng, also known as Tianqi, uses its root as medicine and has the effects of dispersing blood stasis and promoting blood circulation, reducing swelling and relieving pain, and stopping bleeding. In the production of Chinese medicinal materials, its status is second only to ginseng. So what pesticide should be used for Panax notoginseng blight, viral disease, and black spot? What are the disease symptoms?
Blight
Panax notoginseng blight is also called “leaf rot”, commonly known as “clear water disease” and “overlapping leaf rot”. It is currently a common disease in Panax notoginseng cultivation. Wind and rain and human farming operations are the main ways the disease spreads.
Panax notoginseng blight has the characteristics of strong suddenness and a short disease course, often causing varying degrees of yield loss to growers. Panax notoginseng blight often occurs in rainy seasons. If the shade shed in the Panax notoginseng garden is too dense and humidity is too high, the disease is likely to occur; after dry, rainless weather turns cool, the disease is mild. It is first seen from March to April and ends from late October to early November. The peak incidence is concentrated in April to May and August to October, and sometimes extends to early November. During the more rainy period from June to August, the disease incidence is relatively low, mainly because the rainfall during this period is mostly cloudy and rainy weather with lower temperatures.
Main conditions for disease occurrence:
1. Panax notoginseng blight occurs in rainy seasons. If the shade shed in the Panax notoginseng garden is too dense and humidity is too high, damage is likely to occur; after dry, rainless weather turns cool, the disease is mild.
2. It is likely to become epidemic during the rainy season or when humidity in the shed is too high. At this time, attention should be paid to opening the garden gate for ventilation.
3. Remove diseased plant residues and branches to reduce the initial infection source of pathogens.
Symptoms
The symptoms of damage to the stems of Panax notoginseng plants vary depending on the age of the plants:
One-year-old Panax notoginseng: after the base of the pseudostem is infected, it becomes water-soaked and constricted, ultimately causing the seedlings to bend and fall from the base.
Two-year-old and three-year-old Panax notoginseng: when the stem is damaged, the affected part dehydrates and constricts; damage to the base can cause some plants to lodging. If the pathogen continues to expand and cause damage, it leads to root rot. On the top of the stem and the flower axis, the affected part becomes water-soaked, constricted, twisted, and broken, which growers call “twisted chicken leg”; when the inflorescence is damaged, dry flowers form. If the air humidity in the garden is high, a thin layer of white mold can be seen on the diseased parts.
When the base of the stem or the bud is damaged, the diseased tissue is water-soaked, the boundary between diseased and healthy tissue is not obvious, and sometimes an extremely thin gray-white mold layer can be seen. When the stem base loses water and constricts, the aboveground plant becomes green-wilted and drooping, and eventually lodges. When the root is damaged, the affected part initially appears dehydrated, then rots, showing wet rot.
So how should we prevent and control it?
Agricultural control: ① implement crop rotation ② deep plowing and sun-drying the soil ③ rational fertilization ④ ventilation and moisture removal ⑤ uniform light transmission in the shade shed ⑥ strengthen Panax notoginseng garden management.
Chemical control:
Formula 1: Shuangfu + Dasheng + Yongguan + Bankening + Dingduan + Procymidone;
Formula 2: Jirun + Jinkefan + Luker + Huirui + Shidian + Captan;
Formula 3: Zhangshang Mingzuan + Dameilu + Yongguan + Procymidone + Zhuolv;
Formula 4: Dejin + Shuangong Fuma + Huifu + Yinling + Xirui + Baonongjin;
Formula 5: Xitai (Xiupu) + Shuangqing + Yingli + Huirui + Yingxiangli.
Viral disease
Panax notoginseng viral disease is also one of the main diseases in current Panax notoginseng production. The current incidence rate is 5% to 15%, and in severe Panax notoginseng gardens the incidence rate reaches more than 70%.
Symptom manifestations:
(1) Crinkling
Seeds carrying the virus emerge later. After emergence, the plants are short, and the leaves are crinkled; in severe cases they crinkle into a ball.
After some infected plants grow for a period, they may slowly unfold, but compared with healthy plants, the leaves are generally narrow and small, and a small number of leaves become deformed due to growth imbalance.
(2) Cluster branching
Small petioles grow directly at the top of the Panax notoginseng stem, with no obvious differentiation of compound leaf petioles, forming a cluster-branch appearance.
(3) Mosaic
There are two types of symptoms:
In the early stage, the veins are yellow-white, and the mesophyll between the veins is light yellow; in the later stage, the veins become yellow-brown and necrotic, and the mesophyll between the veins is yellow. Panax notoginseng leaves form a mosaic pattern of alternating yellow and green, and in severe cases the crinkled leaves cannot unfold.
Panax notoginseng leaf mesophyll shows uneven chlorotic patches, with no obvious boundary between diseased and healthy tissue, but the veins remain green. Mildly affected plants can survive for a long time and seed setting is not affected, but the seeds collected emerge the following year and clearly show mosaic symptoms; severely affected plants cannot carry out normal photosynthesis and grow noticeably weaker than other plants.
Disease pattern:
Panax notoginseng plants with viral disease are more likely to show symptoms during the leaf expansion period (March to May), but plants with the chlorosis-type viral disease are more likely to show symptoms in the middle and late stages of the Panax notoginseng growth period. Generally, in years when winter and spring are relatively dry, viral disease occurs more severely.
Transmission routes and conditions for disease occurrence:
The virus of this disease is mainly carried by Panax notoginseng seeds or seedlings, and is mainly transmitted by aphids.
Control methods:
(1) Agricultural control: ① When selecting land, try not to use plots whose previous crop was flue-cured tobacco as Panax notoginseng land, because this is one of the root causes of Panax notoginseng viral disease.
② Choose disease-free seeds and seedlings, especially taking care not to keep the fruits of plants already infected with the virus for seed.
③ Strengthen field management, promptly control the occurrence of insect pests, remove weeds and diseased residues from the Panax notoginseng garden, and bury them deeply in a centralized manner.
(2) Chemical control:
① Fulidu + Zhibeijian + Wanjia Weiliang + Hao Xintai + Meibang Jindianzi
② Ningnanmycin + Baozhibitai + Nengbaiwang + Zhuomete + Dianjiang
Black spot
Panax notoginseng black spot is a common and seriously harmful major disease. The general incidence rate is 20—35%, and in severe cases it reaches more than 90%.
Symptoms
Panax notoginseng black spot can infect all parts of the plant. When leaves are infected, nearly round or irregular water-soaked lesions are mostly produced at the leaf tip, leaf margin, and middle of the leaf. Under dry conditions, the lesions tend to perforate or rupture; under humid conditions, the lesions expand quickly, reaching 1/3—1/2 of the whole leaf, and the leaf then falls off, which is what we often refer to as leaf drop.
When stems, petioles, and flower axes are damaged, elliptical yellow-brown lesions initially appear, then the lesions expand upward and downward and become sunken. When the stem is severely affected, the plant bends, droops, and lodges, and the upper part of the diseased plant shrivels and withers.
Pathogen
The pathogen of Panax notoginseng black spot belongs to Deuteromycotina, Hyphomycetes, Moniliales, Alternaria, a genus of fungi (higher fungi).
Disease pattern
Panax notoginseng black spot overwinters as conidia, mycelium, etc. in diseased plant residues, seeds, seedlings, pine needles, and soil. When the temperature rises the following year and conditions are suitable, the pathogen begins to infect and damage Panax notoginseng.
High temperature and high humidity conditions help the occurrence and spread of Panax notoginseng black spot. In addition, the stronger the light transmittance, the more severe the disease; excessive fertilization, and excessive or heavy application of nitrogen fertilizer, cause Panax notoginseng to grow excessively, with poor disease resistance, which helps the occurrence and epidemic of black spot.
Control measures
(1) Choose Panax notoginseng land. It is best to choose land with high terrain and good soil permeability that has not been planted with Panax notoginseng.
(2) Do a good job in field management. Build a shade shed with suitable light, fertilize reasonably, and pay attention to Panax notoginseng garden cleanliness.
(3) Seed selection and seed treatment. It is best to choose the first and second batches of disease-free, large, plump red seeds from three-year-old Panax notoginseng for seedling raising. And disinfect the seeds.
(4) Choose seedlings and disinfect them. After removing damaged, diseased, weak, and small residual seedlings and weak seedlings unsuitable for planting, disinfect them with chemicals.
(5) Panax notoginseng garden cleanliness. After Panax notoginseng is harvested, thoroughly remove diseased plant residues, and destroy garden weeds in a centralized manner. Carry out garden cleaning according to the disease situation of Panax notoginseng that year. After Panax notoginseng is harvested and before emergence, fungicides should be sprayed heavily 2—3 times to control overwintering pathogens and reduce the source of primary infection in the second year.
(6) Chemical control. After Panax notoginseng emerges, if central diseased plants are found, insert bamboo sticks as markers, remove the diseased and residual plants, and then carry out key chemical control in a timely manner. Generally spray once every 7—10 days.
Recommended: 1. Jinjiguan + Puyijia, spray
2. Xiuze + Xiuku, spray treatment