What are the methods for controlling pests and diseases of poinsettia?

1. Poinsettia gray mold

Symptoms: After the inflorescence is infected by the pathogen, it initially shows grayish-brown spots, then rapidly wilts and rots. The pathogen then spreads along the flower stalk and begins to damage the flowering branches, causing the young twigs to die, turning yellowish-brown, and often producing grayish-brown mold-like growth on them.

Control methods: Maintain a suitable temperature for poinsettia, ensure good ventilation, and provide sunlight. Household potted poinsettias can be moved to a ventilated spot on the balcony. When disease occurs, spray with 20% Shibaoling 600-1000 times dilution, or 75% chlorothalonil 800-1000 times dilution.

2. Poinsettia damping-off

Symptoms: The disease often occurs at the stem base near the ground. After infection by the pathogen, irregular brown spots first appear, then gradually expand radially, and finally encircle the stem base, causing the cortex to turn black and rot, the leaves to lose water and wilt, and the entire plant to wither and die.

Control methods: The cutting bed for raising seedlings should use sterile soil or undergo soil disinfection. Soil disinfection should be carried out several weeks before cutting. Apply 30 ml of formaldehyde per sq m, add 2000-4000 ml of water, spray onto the bed, cover with plastic film for 5-6 days, remove the cover, rake the soil to release toxic gases for about 2 weeks, then proceed with cutting. Spray chemicals for control during the seedling stage. Options include 50% litujing wettable powder 800-1000 times dilution, or 64% shadufan 500 times dilution, or 65% dikesong 600-800 times dilution.

Well, that's all about poinsettia cultivation and pest and disease control methods. You can also try growing poinsettia in pots on your balcony. I hope this knowledge is helpful to everyone.

What are the common pests and diseases of poinsettia, and the control methods for poinsettia pests and diseases

Poinsettia has an elegant plant shape and a high-end, refined temperament, making it very suitable for traditional Chinese festivals, as if tailor-made for China. Since poinsettia blooms during New Year's Day and the Spring Festival, it carries the beautiful meaning of universal celebration and welcoming new life. However, during home cultivation, there are always some unsatisfactory aspects that affect the ornamental effect of poinsettia. So what are the common pests and diseases of poinsettia? Below, I will introduce the control methods for poinsettia pests and diseases.

What are the common pests and diseases of poinsettia

Common pests and diseases of poinsettia include gray mold, root rot, leaf spot, and whitefly. These diseases not only affect the overall home ornamental effect of poinsettia but can even threaten its life in severe cases, so everyone should pay extra attention to poinsettia pests and diseases.

Control methods for poinsettia pests and diseases

Gray mold

Gray mold mainly occurs in winter, which is exactly the blooming season of poinsettia. Once there is continuous rain, humidity, and no sunlight, it can harm poinsettia inflorescences, bracts, leaves, and branches. Generally, water-soaked lesions first appear on the flower clusters. Afterward, the lesions are covered with a layer of pathogen conidia, and the pathogen continues to spread to the bracts. In the early stage on bracts, water-soaked faded spots appear, then gradually expand into irregular shapes. The pathogen then spreads to the branches, producing yellowish-brown to brown lesions on the branches. In the later stage, the lesions clearly sink downward and turn dark brown, and in severe cases the lesion areas become dry and withered. The pathogen is Botrytis, which can survive on dead plant tissues or other organic matter and has a wide host range. It can survive at temperatures of 0-38°C, and as long as there is moisture, it persists. If the greenhouse is too humid, cold, and dim, after 1-2 d the pathogen produces a large number of conidia that float in the air and begin infecting plant tissues.

Control methods: Taking advantage of the closed nature of the facility, create a high-temperature, low-humidity ecological environment to control the occurrence and development of gray mold. At night, indoor humidity in the facility is often above 90%. After pulling up the straw mats in the early morning, immediately open the ventilation openings to ventilate and remove moisture, reduce indoor humidity, and control disease development with a relatively low temperature. After 9 o'clock, when the indoor temperature rises faster, close the ventilation openings to rapidly raise the indoor temperature to about 32°C.

Root rot

Root rot and stem rot can infect mature plants and can also infect during the seedling bed stage, causing serious losses. It generally occurs more severely in high-temperature seasons, and is also very likely to occur when the cultivation soil has high water content. In the early stage, the plant shows wilting. At this time, if the stem base is examined, a light brown constriction can be seen, but the infected plant shows no rot or hydrolysis. Later, the lesions gradually spread upward, and the wilting gradually becomes more severe. The stem lesions are slightly sunken and yellowish-brown. In the later stage, the tissue at the lesion disintegrates, causing the plant to wither and die due to severe water shortage. Sometimes the entire plant turns yellow in a water-soaked manner and eventually rots and dies. White mycelium can be seen near the ground, and in severe cases it can spread to the cultivation soil. When the roots are affected, root rot often results, initially affecting normal plant growth and in severe cases leading to death. The main pathogens are Phytophthora, Rhizoctonia solani, Pythium, etc. When salts accumulate on the medium surface; Pythium appears when poinsettia is a mature plant, and it may have already invaded during cutting. When the environment is suitable for reproduction, it worsens, causing root rot and death; high temperature and excessive irrigation (adverse conditions) can cause Phytophthora damage.

Control methods:

1. Implement crop rotation. Rotate every other year in lightly diseased fields, and rotate every 3-5 years in heavily diseased fields.

2. Deep plowing to improve soil, increase application of organic fertilizer, rational drainage and irrigation, and enhance disease resistance.

3. Strictly select seeds and eliminate unqualified seeds. Dress seeds with 50% carbendazim wettable powder at 0.5% of seed weight.

4. When disease occurs, spray 50% carbendazim wettable powder 1000 times dilution on the stem base of peanuts, using 25-30 kg of spray solution per mu each time.

Leaf spot

Leaf spot mainly occurs more severely in spring and summer, and the lesions mostly begin on old leaves. In the early stage, small purplish-red to brown spots appear on the leaves. The lesions are nearly circular to irregular, and later gradually expand. Many lesions can merge with each other to form one large lesion, and in the later stage the center of the lesion gradually turns grayish-brown. In severe cases, the lesion tissue becomes gangrenous, causing the leaves to twist and dry up.

Control methods:

Remove diseased tissue promptly and burn it in a centralized manner; crop rotation (soil can be changed in greenhouses); do not spray water over the plants; begin spraying chemicals from the early stage of disease to prevent the disease from expanding and spreading.

Whitefly

The main insect pests of poinsettia include whitefly, spider mites, thrips, etc. Adult and larval whiteflies prefer dense, shaded environments and gather on the upper leaf undersides of poinsettia, using piercing-sucking mouthparts to feed on sap, causing leaves to fade or develop chlorotic spots, affecting photosynthesis and leading to poor plant growth. The honeydew excreted by the insects often causes sooty mold. Adults are attracted to yellow. Emergence begins at 6 a.m., with the greatest emergence from 7-8 a.m. and the lowest in the evening. Whiteflies are most vulnerable as newly mobile young larvae, followed by newly emerged adults, and are sensitive to pesticides, making this a suitable time for chemical control. Whiteflies generally outbreak in large numbers under high temperature and low humidity, with the peak period from late September to late November. The optimal control period is late September, and the spraying time is 6-10 a.m.

Key points for poinsettia pest and disease control

It is understood that the main diseases of poinsettia in Guangdong include gray mold, root rot, southern blight, etc., and the main insect pest is whitefly. To do a good job in controlling the above pests and diseases, the key is to rely on cultivation techniques for prevention, such as substrate disinfection, strengthening greenhouse sanitation management, controlling temperature and humidity, and spraying chemicals for control, so as to resist the occurrence of pests and diseases.

First of all, start with the substrate. Shunde Beijiao Farmers Entrepreneurship Park recommends that when planting poinsettia, it is best to choose only clean substrates such as peat soil and perlite to reduce the occurrence of pests and diseases. However, it is understood that many growers currently often mix peat soil with other substrates such as garden soil and pond mud when planting poinsettia. Doing so is not only unfavorable to plant growth, but also leads to severe pest and disease occurrence.

Poinsettia gray mold, root rot, and southern blight generally occur during the rainy season or after continuous rainy days, and develop rapidly. Insufficient light on rainy days and long-term water accumulation on leaves and plant roots after watering create a high-humidity micro-environment, which easily induces pathogen infection and leads to disease epidemics. Therefore, in case of rainy weather, attention should be paid to timely ventilation and moisture removal after rain, and timely spraying to prevent disease occurrence. Some broad-spectrum fungicides such as chlorothalonil and carbendazim can be used. In addition, according to the recommendation of technicians at Shunde Beijiao Farmers Entrepreneurship Park, Jinlei 68% water-dispersible granules can be used, sprayed about once every 10 days, 2-3 times total, with the concentration referring to the instructions.

According to technicians at Shunde Beijiao Farmers Entrepreneurship Park, whitefly is the main insect pest of poinsettia, reproduces extremely quickly, and once it occurs, control is difficult. Therefore, prevention must be done well during production. In addition to soil disinfection, after poinsettia is first potted, it is best to apply an insecticide once, such as imidacloprid or buprofezin, for prevention. In addition, because the key to controlling whitefly is to avoid the occurrence of large populations, insect-proof nets should be installed on greenhouse doors and windows and for outdoor maintenance to prevent the entry of external pests. Some methods can be used to monitor the occurrence trend of whitefly populations, such as using yellow plastic boards coated with petroleum jelly, placed slightly higher than the poinsettia, and gently shaking the plants manually. Adult whiteflies will be attracted by the bright yellow color, achieving the purpose of trapping and killing while also serving a monitoring function. If found, promptly remove the lower leaves with large numbers of whitefly eggs and nymphs, and immediately spray for control. Options include supusha, lesiben, and fenqiuzhi. The recommended spraying time is 6-10 a.m., continuously spraying 3-5 times.