Prevention and control of diseases and insect pests in poinsettia

1. Botrytis cinerea

Symptoms: after inflorescence was infected by bacteria, it showed grayish brown spots at first, then withered and rotted rapidly. The pathogen then spreads along the flower stalk and begins to harm the flower branches, causing the twigs to die and turn yellowish brown, often producing grayish brown mildew above.

Prevention and control methods: maintain the appropriate temperature of poinsettia, pay attention to ventilation, there should be sunshine. Poinsettias of family potted plants can be moved to the balcony. The disease can be sprayed with 20% Shibaoling 600 × 1000 times, or 75% chlorothalonil 800 × 1000 times.

two。 Poinsettia blight

Symptoms: the disease often occurs at the base of the stem near the ground. after infection, irregular brown spots are produced at first, then gradually expand radially, and finally around the stem base, the cortex turns black and rotten, the leaves lose water and wilt, and the whole orange dies.

Prevention and control methods: the cutting bed of seedlings should be sterilized with aseptic soil or soil disinfection. Soil disinfection was carried out a few weeks before cutting. Spray it on the bed with 30 ml formaldehyde per square meter, plus 20-4000 ml water, cover it with plastic film for 5-6 days, remove the mulch, rake the soil and release toxic gas for about 2 weeks, and then cut. Spray control at seedling stage. You can choose 50% Likujing wettable powder 800 × 1000 times, or 64% alum 500 times, or 65% dimethazone 600 times 800 times.

Well, there are so many ways to cultivate poinsettia and prevent diseases and insect pests. You can also try to plant poinsettia in the balcony. I hope this knowledge can be helpful to you.

What are the common diseases and insect pests of poinsettia? the prevention and control methods of poinsettia diseases and insect pests

Poinsettia has a beautiful shape, high-end and elegant temperament, which is very suitable for traditional Chinese festivals and seems to be tailor-made for China. As poinsettia blossoms at the time of New Year's Day and Spring Festival, there is a beautiful implication of celebrating the whole world and wishing new life together. However, in the process of family breeding, there will always be some unsatisfactory places to affect the ornamental effect of poinsettia. So what are the common diseases and insect pests of poinsettia? The following is to introduce the prevention and control methods of diseases and insect pests of poinsettia.

What are the common diseases and insect pests of poinsettia

Common diseases and insect pests of poinsettia include Botrytis cinerea, root rot, leaf spot and whitefly. These diseases not only affect the overall household ornamental effect of poinsettia, but also even take the life of poinsettia when it is serious, so we should pay special attention to the diseases and insect pests of poinsettia.

Control methods of diseases and insect pests in poinsettia

Grey mold disease

Botrytis cinerea mainly occurs in winter, when poinsettia blossoms. Once it is rainy and wet, it can harm inflorescences, bracts, leaves and branches of poinsettia. Generally speaking, water-immersed disease spots begin to appear from the tidbits. After that, the disease spot was covered with a robe of pathogens, and the pathogens continued to spread to the bracts. The bracts produced water-immersed discolored spots at the initial stage, and then gradually expanded into irregular shapes, and the pathogens extended to the branches, producing yellowish brown to brown spots on the branches. in the later stage, the disease spots were obviously sunken dark brown, and in severe cases, the disease spots were dry. The pathogen is Botrytis, which can live on dead plant tissue or other organic matter and has a wide range of parasites. It can survive at a temperature of 0-38 ℃, and it exists as long as there is moisture. If the greenhouse is too wet, cold and lack of light, after 1-2 days, the pathogens will produce a large number of robes free in the air and begin to infect plant tissue.

Prevention and control methods: make use of the closed facilities to create an ecological environment with high temperature and low humidity to control the occurrence and development of Botrytis cinerea. Most of the indoor humidity of the facility is higher than 90% at night. after pulling in the morning, the vents should be opened immediately to ventilate and drain moisture, reduce the indoor humidity, and control the development of the disease with a lower temperature. When the indoor temperature rises and accelerates after 9 o'clock, close the vents and quickly raise the indoor temperature to about 32 ℃.

Root rot disease

Root rot and stem rot can be infected into adult plants, or in the seedling bed stage, resulting in serious losses. Generally, the occurrence is more serious in the high temperature season, and it is also very easy to occur when the cultivated soil water content is high. The phenomenon of wilting appeared in the early stage of the plant, but if the base of the stem was examined, the phenomenon of light brown constriction could be seen, but there was no corruption or hydrolysis in the infected plant, and then the disease spot gradually spread upward, and the wilting phenomenon became more and more serious, and the disease spot was slightly sunken in yellow brown. In the later stage, the tissue of the disease spot disintegrated, causing the plant to wither to death due to serious lack of water, and sometimes the whole plant was yellowed in water, resulting in decay and death. The white hyphae can be seen near the ground and can be extended to the cultivated soil in severe cases. When the root is sick, it often causes root rot, which affects the normal growth of the plant at the initial stage and leads to death in serious cases. The main pathogens are Phytophthora, Rhizoctonia solani, Pythium and so on. When salt accumulates on the surface of the medium, Pythium appears when poinsettia grows up, and it may invade when cutting, and deteriorate when the environment is suitable for reproduction, resulting in root rot and death; high temperature and excessive irrigation (stress conditions) can cause damage to Phytophthora.

Prevention and control methods:

1. Implement crop rotation. The mildly diseased fields were rotated every other year, and the seriously diseased fields were rotated at intervals of 3-5 years.

2. Deep ploughing and soil improvement, increasing application of organic fertilizer, rational drainage and irrigation to enhance disease resistance.

3. Strict seed selection and elimination of unqualified seeds. Mix seeds with 50% carbendazim wettable powder at 0.5% of seed weight.

4. Spray the stem base of peanuts with 1000 times of carbendazim wettable powder, 25-30 kg per mu each time.

Leaf spot disease

Leaf spot disease mainly occurs in spring and summer, and the disease spot mostly occurs from the old leaves. In the early stage, purplish red to brown spots were produced on the leaves, and the disease spots were nearly round to irregular, and then the disease spots gradually expanded, and most of the disease spots could heal each other to form a large disease spot, and in the later stage, the center of the disease spot gradually changed to grayish brown. In severe cases, the lesion tissue is gangrenous, causing the leaves to twist and dry up.

Prevention and control methods:

Timely removal of diseased tissue, centralized burning; crop rotation (soil can be changed in the greenhouse); not suitable for plant spraying; spraying from the early stage of the disease to prevent the spread of the disease.

Whitefly

The main pests of poinsettia are whitefly, leaf mite, thrips and so on. The adults and larvae of whitefly prefer a dense shady environment and cluster on the upper leaf back of poinsettia to suck juice with prickle mouthparts, which makes the leaves fade or appear chlorotic spots, affecting photosynthesis and leading to poor plant growth. Honeydew excreted by worms often causes mildew. Adults have a yellowing tendency. The Eclosion time begins at 6 o'clock in the morning, with the highest Eclosion from 7 am to 8 am and the lowest at night. The first instar mobile larvae of whitefly are the most vulnerable, followed by rigid Eclosion adults, which are sensitive to pesticides and suitable for spraying control. Whitefly usually occurs at high temperature and low humidity, and the peak period is from late September to late November. The most suitable prevention and treatment period is late September, and the spraying time is 6-10:00 in the morning.

The key to the control of diseases and insect pests in poinsettia

It is understood that the main diseases of poinsettia in Guangdong are Botrytis cinerea, root rot, white silk disease and so on, and the insect pests are mainly whitefly. In order to do a good job in the prevention and control of the above diseases and insect pests, the key is to rely on cultivation techniques for prevention, such as substrate disinfection, strengthening greenhouse health management, temperature and humidity control, spraying control and other ways to resist the occurrence of diseases and insect pests.

First of all, we should start from the matrix. Shunde Beijiao Farmers' Entrepreneurship Park suggests that when planting poinsettia, it is best to choose only clean substrates such as peat soil and perlite to reduce the occurrence of diseases and insect pests. However, it is understood that many farmers often use peat soil and other substrates such as garden soil and pond mud when planting poinsettia, which is not only not conducive to plant growth, but also serious diseases and insect pests.

Botrytis cinerea, root rot and white silk disease generally occur in the rainy season or after continuous rainy days, and develop rapidly. Lack of light in overcast and rainy days, water accumulation in leaves and roots for a long time after dripping water will cause high humidity and small environment, which can easily induce pathogen infection and lead to the epidemic of the disease. Therefore, in case of overcast and rainy weather, we should pay attention to timely ventilation and moisture discharge after rain, and timely spray to prevent the occurrence of diseases, and some broad-spectrum fungicides such as chlorothalonil, carbendazim, etc., can be used according to the recommendation of technicians in Beijiao Peasant Entrepreneurship Park in Shunde. Jinlei 68% water dispersible granule can be used, spray once every 10 days, spray 2 times for 3 times, and the drug concentration can be referred to the instruction manual.

According to the technical staff of Beijiao Farmers' Entrepreneurship Park in Shunde, whitefly is the main pest of poinsettia, the breeding speed is extremely fast, once it occurs, it is difficult to control, so prevention work must be done in the production process. In addition to doing a good job of soil disinfection, poinsettia had better hit an insecticide such as imidacloprid and paracetamol to prevent it. In addition, as the key to control whitefly is to avoid the occurrence of a large number of populations, greenhouse doors and windows and outdoor maintenance should be equipped with insect nets to avoid the entry of external pests. Some methods can be adopted to monitor the occurrence trend of whitefly population, such as using yellow plastic board, painting Vaseline, placing slightly higher than one poinsettia, shaking the plant gently, and the adult whitefly will be attracted by bright yellow to achieve the purpose of trapping and killing. It can also play a monitoring role. If it is found that a large number of whitefly eggs and lower leaves with nymphs should be removed in time, and spray immediately, you can choose quick culling, Lesbon, whitefly treatment, etc., spraying time is recommended at 6: 10 in the morning, spraying 3 times in a row for 5 times.