What to do when a potted poinsettia gets pests? Remove diseased leaves promptly to prevent and control pests and diseases

Because the poinsettia's colors are bright and appealing, many flower growers choose to keep it indoors. But indoors is certainly no match for the wild, and because conditions are poorer, the poinsettia can be troubled by pests. So what do you do when a poinsettia gets pests? Soil, light, water and more can all cause the poinsettia to fall ill. Below is a carefully compiled guide to poinsettia pest and disease control; if you love flowers, you simply must come and take a look~

I. What to do when a poinsettia gets pests: find the cause

In our guide to growing poinsettias, we explain that when potted indoors, the poinsettia has requirements for soil, light, water and more, and once something is done improperly, pests or disease will appear on the leaves. As for what to do when a poinsettia gets pests, it is actually very simple: we just need to find out which pest it is, then deal with it accordingly. Below are the symptoms and solutions for several pests, as follows:

1. Whitefly

Whitefly, one of the main pests of the poinsettia, lives in groups on the underside of poinsettia leaves, using its piercing-sucking mouthparts to feed on sap, causing the leaf surface to fade or develop spots, affecting the plant's photosynthesis and leading to poor growth. Not only that, the secretions of whitefly eggs can also cause sooty mold.

Solution: The peak period for whitefly outbreaks is from late September to late November. So to deal with it, it is best to apply insecticide in the morning from 6 to 10 o'clock in late September. In addition, when there are few insects, you can directly remove the leaves, then spray a fungicide.

2. Red leaf mite / red spider mite

Red leaf mite, that is, the red spider mite, is the demon of all potted flowers, which naturally includes the poinsettia. Red spider mites like to perch on the underside of old poinsettia leaves, and affected leaves have yellow spots. In severe cases the leaves are damaged, the plant withers, and it becomes a bare "commander with no troops."

Solution: To deal with red spider mites, prevention should still be the priority. During care, frequently check the underside of leaves, discover eggs early, remove the leaves, and move the plant to a sunny spot. When there are many pests, you can spray a pesticide for control.

3. Red thrips

The parts damaged by thrips include buds, leaves, flowers and so on, with tender leaves and new shoots suffering the most severe damage, causing poor plant development. White markings on both sides of the leaf midrib can be used to identify the damage characteristic of thrips. Leaves damaged develop white or brown markings, and in severe cases the leaves become twisted and deformed. Flowers damaged become deformed.

Solution: This pest seriously harms the health of the poinsettia. Whenever this pest is found, it should be caught and killed promptly, or a pesticide should be sprayed, once every 3-5 days, until it is completely eliminated.

II. Poinsettia pest and disease control / disease symptoms and solutions

Besides being attacked by pests, diseases also constantly threaten the health of the poinsettia. It is understood that the main diseases of the poinsettia are three: leaf spot, root rot and gray mold, among which leaf spot is very serious, and we should remedy it promptly. The specific symptoms and solutions are as follows:

1. Leaf spot

Leaf spot, a very serious disease, often attacks the poinsettia. This disease occurs more severely mainly in spring and summer, and the lesions mostly begin on old leaves. In the early stage, irregular lesions appear on the leaves, then rapidly expand and spread, causing the leaves to twist and dry up.

Solution: When lesions are found on leaves, remove them promptly and throw them away. Usually clean up dead leaves often and keep the soil surface clean. When the disease is severe, spray a pesticide; you can choose a 1000-fold solution of chlorothalonil, spraying once every 5-7 days, and it will improve within 3-5 days.

2. Root rot

Root rot usually occurs in the hot season, but soil, watering and other factors can also bring on this disease. Infected plants show light brown spots on the roots, but in the early stage symptoms are very hard to spot on the above-ground parts. As the disease worsens, the lesions spread upward, the plant gradually withers, and in the later stage, because the roots cannot absorb water, the plant dies from lack of water.

Solution: Strengthen care in normal times, change the soil promptly, loosen the soil often, and ensure the roots have enough oxygen to breathe. In addition, during care you can drench the roots with a disinfectant once a month to inhibit fungal growth. When roots rot, take the plant out of the pot, cut off the rotted parts, and replant it.

3. Gray mold

Gray mold often occurs in winter, that is, the season when the poinsettia blooms. Once there is continuous rainy, humid, sunless weather, gray mold gets out of control. Brown spots appear on leaves, branches and inflorescences, and as the disease worsens it spreads through the whole plant.

Solution: In winter, strengthen care and management, raise the indoor temperature, increase light transmission, and lower humidity. Once an infected plant is found, immediately move it to a ventilated spot and place it in the sun, which can achieve effective control. In addition, when the disease is severe, you can spray Bordeaux mixture for treatment.

Flowers originally grow in nature; forcibly moving them into the home to grow means that no matter how careful you are, problems will always arise. Still, to improve the indoor environment, doing so is understandable. But to reduce your own trouble, everyone needs to master the knowledge above, so that when you run into problems, you can solve them easily. That is all for our introduction to poinsettia pest and disease control; we hope it can help everyone.

Poinsettia pest and disease control

During greenhouse cultivation, poinsettias are easily infected by gray mold, root rot, stem rot, leaf spot and other pests and diseases. There has been much targeted research at home and abroad.

Gray mold mainly occurs in winter, which is exactly the poinsettia's flowering season. Once there is continuous drizzle, humidity and no sunlight, it often gets out of control, and it can harm the poinsettia's inflorescences, bracts, leaves and branches. Generally, water-soaked lesions first appear on the inflorescences. After that, the lesion area is covered with a layer of the pathogen's conidia, and the pathogen continues to spread to the bracts. In the early stage, water-soaked faded spots appear on the bracts, which then gradually expand into irregular shapes. The pathogen then spreads to the branches, producing yellow-brown to brown lesions on the branches. In the later stage the lesions are clearly sunken and dark brown, and in severe cases the lesion area becomes dry and withered, completely losing ornamental value. The pathogen is Botrytis. The pathogen is found almost throughout the entire greenhouse; it can survive on dead plant tissue or other organic matter, and it has a wide host range. It can survive at temperatures from 0-38°C; as long as there is moisture, it exists. If the greenhouse is too humid, cold and dim, after 1-2 days the pathogen produces large numbers of spores that float in the air and begin to infect plant tissue.

Root rot and stem rot can infect adult plants and can also infect during the seedling bed stage, causing serious losses. They generally occur more severely in the hot season, and are also very likely to occur when the cultivation soil has a high water content. In the early stage the plant shows wilting; if you then examine its stem base, you can see a light brown constriction, but infected plants show no rotting or hydrolysis. Later the lesions gradually spread upward, and the wilting gradually worsens. The lesions on the stem are slightly sunken and yellow-brown. In the later stage the tissue at the lesion breaks down, causing the plant to wither and die from severe water shortage. Sometimes the whole plant turns yellow in a water-soaked manner and finally rots and dies. Near the ground, white mycelium can be seen, and in severe cases it can spread to the cultivation soil. When the roots are affected, it often causes root rot; in the early stage it affects the plant's normal growth, and in severe cases it leads to death. The main pathogens are Phytophthora, Rhizoctonia and Pythium, etc. When rooted cuttings are potted, they are most susceptible to Rhizoctonia, especially when the stem is injured or when fertilizer! salts accumulate on the medium surface; Pythium appears when the poinsettia is an adult plant, and it may have already invaded at the cutting stage. When the environment is suitable for cultivation, it worsens, causing root rot and death; high temperatures and excessive irrigation (adverse conditions) can cause Phytophthora damage.

Leaf spot occurs more severely mainly in spring and summer, and the lesions mostly begin on old leaves. In the early stage, small purple-red to brown spots appear on the leaves, and the lesions are nearly round to irregular. Later the lesions gradually expand, and most lesions can merge with each other to form one large lesion. In the later stage the center of the lesion gradually turns gray-brown. In severe cases the lesion tissue becomes gangrenous, causing the leaves to twist and dry up. The pathogen is Cercospora.puleherrimaeTherp., spread by rain and wind, invading through leaf edges or wounds.

The main pests of the poinsettia are whitefly, spider mite, thrips and so on

The adults and larvae of whitefly prefer dense, shaded environments. They cluster on the upper leaf undersides of the poinsettia and use their piercing-sucking mouthparts to feed on sap, causing the 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. The adults are attracted to yellow. Emergence begins at 6 a.m., with the greatest emergence from 7 to 8 a.m. and the least at night. Whitefly is most vulnerable in the early mobile larval stage, followed by newly emerged adults, which are sensitive to pesticides, making this a suitable time for spraying. Whitefly generally breaks out in large numbers under high temperature and low humidity, with the peak period from late September to late November. Its optimal control period is late September, and the spraying time is from 6 to 10 a.m.

Spider mite, also called red spider mite, is a common pest in greenhouses. It occurs for more than 20 generations throughout the year, and occurs severely under higher temperatures and dry, rain-scarce conditions. March to June and September to November are the peak periods. Mites or nymphs all like to perch on the underside of old leaves. Affected leaves have yellow spots, and checking the leaf underside reveals insects, eggs, webs and secretions and other debris. When they break out in large numbers they form webs and cause damage, causing the plant to stop growing, the leaves to dry up and fall off, and the plant to die.

Thrips are only about 1-2 mm long, and their damage can be found on the leaves or flowers of almost all greenhouse-cultivated plants. But generally their damage to the poinsettia is not very serious. Adults and nymphs are pale yellow or orange-yellow and harm plants with their rasping-sucking mouthparts. The damaged parts include buds, leaves, flowers and so on, with tender leaves and new shoots suffering the most severe damage, causing poor plant development. White markings on both sides of the leaf midrib can be used to identify the damage characteristic of thrips. Leaves damaged develop white or brown markings, and in severe cases the leaves become twisted and deformed. Flowers damaged become deformed. Yellow sticky traps are effective against adult thrips, but blue and white sticky traps work even better.

The key to controlling whitefly is to avoid the buildup of large populations. Whitefly adults are attracted to bright yellow, so yellow sticky insect traps are very useful for monitoring. There are many products for controlling whitefly in various places, such as "Pujiling" and "Gaoxiao Dagongchen," all of which can be tried. Note here that before using a new product on a large scale, you must first conduct a phytotoxicity test, and only after confirming that the dose used will not cause phytotoxicity to the plants should you use it on a large scale.

Key points for poinsettia pest and disease control

It is understood that the main diseases of poinsettia in the Guangdong region are gray mold, root rot, southern blight and so on, and the main pest is whitefly. To do a good job of 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 pesticides, to resist the occurrence of pests and diseases.

First, start with the substrate. The Shunde Beijiao Farmers' Entrepreneurship Park suggests that when planting poinsettias, it is best to choose only clean substrates such as peat soil and perlite to reduce the occurrence of pests and diseases. But it is understood that at present many growers often mix peat soil with other substrates such as garden soil and pond mud when planting poinsettias. Doing so is not only unfavorable to plant growth, but also leads to severe outbreaks of pests and diseases.

Poinsettia gray mold, root rot and southern blight generally occur during the rainy season or after continuous rainy days, and develop rapidly. On rainy days there is insufficient light, and after watering, water accumulates on the leaves and at the plant roots for a long time, creating a high-humidity micro-environment that easily induces pathogen infection and leads to disease outbreaks. Therefore, in rainy weather, attention should be paid to timely ventilation and dehumidification after the rain, and timely spraying to prevent disease occurrence. You can use some broad-spectrum fungicides such as chlorothalonil and carbendazim, etc. In addition, according to the recommendation of technicians at the Shunde Beijiao Farmers' Entrepreneurship Park, you can use Jinlei 68% water-dispersible granules, spraying about once every 10 days, 2-3 sprays in total, with the concentration referring to the instructions.

According to technicians at the Shunde Beijiao Farmers' Entrepreneurship Park, whitefly is the main pest of poinsettia. It reproduces extremely quickly, and once it occurs, control is difficult, so prevention work must be done well during production. Besides doing a good job of soil disinfection, it is best to apply an insecticide once right after the poinsettia is potted, such as imidacloprid or Pujiling, for prevention. In addition, because the key to controlling whitefly is to avoid the buildup of large populations, insect-proof nets should be installed on greenhouse doors and windows and for outdoor cultivation to prevent external pests from entering. Some methods can be used to monitor the trend of whitefly population outbreaks, such as using a yellow plastic board coated with Vaseline, placed slightly higher than the poinsettia. Gently shake the plant by hand; whitefly adults will be attracted to the bright yellow, achieving the purpose of trapping and killing, and also serving a monitoring role. If found, promptly remove the lower leaves that have large numbers of whitefly eggs and carry nymphs, and immediately spray for control. You can choose Supusha, Lesiben, Fenghuzhi and so on. The recommended spraying time is from 6 to 10 a.m., spraying 3-5 times in a row.