What if the coconut leaves are dry and yellow?

Take a closer look at the following three.

1。 Coconut bud rot

Symptoms: It mainly harms the most tender leaves and buds in the center of coconut crown. The affected part withered and rotted, and the crown died when it was seriously ill. In the early stage of plant infection, the most tender and unexpanded leaves in the center of the crown first withered, showing light grayish brown, and then drooped and folded from the base. Pathogens spread from the base of young leaves to the tender tissues of buds, causing them to die and rot. At this time, the plant no longer grows tall, and the bacteria continue to harm, which can lead to the death of the whole plant. The tissue at the base of the unexpanded tender leaves in the center is mushy and rotten, and there are common water stains at the base of the unfolded tender leaves, and white mold can grow on the diseased spots.

Pathogenic characteristics: Pathogens like water and cold weather. Sporangium can germinate only in rainy days or when the relative humidity is above 90% and the leaves are sprayed with water in a poorly ventilated room. The optimum growth temperature is 19-25℃. At the end of the rainy season, especially after the typhoon, this disease is the most harmful. The dry season is not frequent. Coconut diseases in inland areas are more serious than those in coastal areas.

Prevention and control methods: 1, eradication of diseased plants: cut the diseased plants from the ground level, pile them up or bury them deeply. When stacking, the affected part should be placed at the bottom to prevent the spread of germs. For plants with only 1-2 branches, the diseased branches can be cut off, the wound can be disinfected with colloidal sulfur or 10% Bordeaux solution, cooled for a few days and sealed with wax. 2. Chemical protection:? 1? After cutting down diseased trees or branches, spray 1% bordeaux solution on surrounding plants or branches for protection. ? 2? Because the initial symptoms of the disease are not obvious, a little negligence may lead to great disaster, and it is difficult for drug treatment to take effect quickly, so prevention is more important than treatment. Spraying 65% zineb 500 times solution and 70% Dixon 700- 1000 times solution 1 times solution outdoors every week for protection. ? 3? Spray medicine in the room after National Day every year. 3. Strengthen tending management: balance fertilization, and water should not be too wet. If it is necessary to manually wipe leaves indoors, it should be changed to 10 and then sprayed with leaf brightener to reduce mouth opening. It is found that the scale insects at the base of petiole are harmful and should be sprayed in time to kill them. Prune diseased leaves in time in winter and burn them centrally.

2。 Botrytis cinerea

Symptoms: Oval spots or waterlogged irregular spots appear on the leaves, resulting in sudden death and dryness of the seedlings. When the condition is serious, the leaves are dark brown and gray-white pine needle mold can be seen.

Disease characteristics: After low temperature in winter, the seedling temperature rises rapidly to nearly 20℃, and when the humidity of seedbed or greenhouse is saturated, the disease occurs and spreads rapidly.

Control method: 1, strengthen the quarantine of introduced seedlings and put an end to the introduction of diseased seedlings. 2. Disinfect the seedbed before sowing. Imported seeds and seedlings can be treated with chemicals before planting, and can be soaked in carbendazim 500-800 times solution 10- 15 minutes. 3. Strengthen cultivation management, keep palm gardens and nurseries clean, cut off diseased leaves in time, and keep ventilation and light transmission. 4. Spray protection in time at the initial stage of the disease, which can be mixed with carbendazim 1000 times solution and 50% zineb 1000 times solution. In spring and summer, spraying 500 times of sterilized alum water or 300 times of fosfomycin of 0.4% washing powder has a good effect.

3。 King coconut leaf spot

Symptoms: It mainly harms King Coconut, Stone Coconut, chinese forest frog, Phoenix, Hailuo and Liriomyza sativae. The disease of seedlings is more serious. At the beginning of the disease, yellow-green spots appeared on the leaves, which gradually expanded into circular or oval spots with a diameter of 2- 10 mm, the center was gray, the edge was orange-yellow or reddish-brown, and sparse black spots were scattered on the back.

Pathogenic characteristics: the pathogen overwinters in the diseased leaves, and the disease is more serious in rainy season in summer and autumn.

Control method: firstly, cut off diseased leaves, appropriately increase the application amount of phosphorus and potassium fertilizer, and spray the leaves with 1% lime, 500 times of 65% zineb wettable powder, 800- 1000 times of crown fungus copper or 300-500 times of 50% captan every 7 days.

1.5 king coconut dry rot

Symptoms: it mainly harms king coconut, and this disease also harms old sunflower and coconut trees. Pathogens mainly invade from the base of the trunk, but they can also invade from the middle or top. Water stains appeared in the early stage of stem infection, which gradually expanded into oval and long patches. The lesion is yellowish brown to dark brown. After the bacteria enter the xylem, they quickly stretch out their hands and cut the trunk. Many punctate brown spots can be seen on the slice. When dissecting the trunk vertically, the xylem appears striped black-brown stripes, but the outer cortex is often asymptomatic, and the infected trunk shrinks and becomes thinner and darker. In severe cases, the stem base tissue is mushy and rotten, with a bad smell. If the pathogen infects from the top, the buds will die and rot, and the plants will no longer grow. Under humid conditions, white mold grows on diseased tissues.

Disease characteristics: Most diseases occur in 4- 10a trees. The relative humidity of the air is high, and the illness is the most serious after the rainy season, especially after the typhoon. The weather with heavy dew or fog is conducive to the spread of diseases. Therefore, the high temperature and rainy season from February to June is the peak of the disease. In the dry and hot season after June, the damage of the disease is obviously weakened. The management level is high, the soil drainage is good, the incidence of adequate fertilizer and water is light, and the incidence of stagnant water or drought and poor fertilizer and water management is serious. Bacteria can be spread by wind, rain and insects. The main source of infection of street trees mainly comes from plant pathogens in nursery.

Control method: 1, strengthening management, eliminating stagnant water, watering in time in case of drought, applying more organic fertilizer and miscellaneous fertilizer, improving plant disease resistance, can effectively reduce the occurrence of diseases. 2. Strict quarantine and elimination of diseased plants. After the onset, cut off the seriously ill plants and destroy them. 3. Spray 1% bordeaux solution or 56% cuprous oxide 300-400 times solution for protection before onset. After onset, 40% fosfomycin 200-300 times solution or 58% metalaxyl 600-800 times solution can be sprayed alternately. The seriously ill plants can be injected with ethyl aluminum phosphate solution, or soaked in wool cloth and wrapped at the base of the stem, which is beneficial for the diseased trees to absorb and kill xylem bacteria. Seriously ill plants can dig out the rotten tissue at the base of the stem, disinfect the surface with 3% sodium fluoride solution, and then apply Bordeaux pulp to protect the wound (Bordeaux pulp is prepared as follows: copper sulfate 1 part, 3 parts of quicklime, 0.4 parts of animal fat and appropriate amount of water). Finally, apply waterproof agent. The waterproof agent is made of 80% turpentine, 5% animal oil, 10% denatured alcohol and 5% ochre powder. If there is a big hole, it should be filled with 1: 2 cement and yellow sand.