How to get rid of powdery mildew on roses
Rose powdery mildew, I believe that those who plant roses will not be unfamiliar with it. The leaves, petioles, tender buds, and flower buds are often covered with a layer of white powdery mildew, as shown in the following picture.
Powdery mildew can cause flower buds to contract, shrink, and die, resulting in malformed sepals, petals, and pedicels, losing their economic and ornamental value. Outdoor roses have a higher incidence of disease in May, June, September, and October, and can occur year-round under greenhouse cultivation. The pathogen of powdery mildew can directly invade the interior of cells through wounds or epidermis, so the thickness and softness of leaves are closely related to the prevention and treatment of powdery mildew.
The main causes of powdery mildew include the following:
(1) Excessive application of nitrogen fertilizer can elongate cells, make their walls thinner and more brittle, weaken their ability to resist stress, and have poor resistance to pathogens. As a biological defense line, the cell wall loses its ability to resist disease and is easily invaded and infected by pathogens.
(2) Poor ventilation or insufficient light can easily lead to disease, and leaves may not grow vigorously under such conditions, resulting in weak photosynthetic capacity, insufficient nutrition, loose cell arrangement, and susceptibility to bacterial infection.
(3) When the humidity inside the greenhouse is high, the bacteria multiply quickly, and the conditions are suitable, the spores of the bacteria can complete their asexual cycle after 72 hours.
(4) The tender leaves of plants during their tender stage contain β – alanine, which is beneficial for the germination and disease of powdery mildew spores.
Convenient and effective treatment methods for rose powdery mildew
(1) Not long after buying this flower, after blooming a batch of flowers, the newly grown buds had powdery mildew and the leaves also had it.
(2) Take out 75% alcohol and put it into a spray can.
(3) Spray heavily on areas with powdery mildew.
(4) After about 10 minutes, spray vigorously with clean water to rinse off the alcohol.
(5) Let it dry in a well ventilated place.
(6) After drying, most of the white powder has been eliminated. If there is still any, the above operation can be repeated every few days for convenience and effectiveness.
(7) The way flowers bloom.
Expansion materials:
Roses are colorful and are an ornamental flower that is loved by many people. During the growth process of roses, they are more susceptible to diseases and pests, including powdery mildew, downy mildew, and dead branches. They are also prone to aphids and red spiders. After discovering the occurrence of diseases and pests in roses, it is important to spray pesticides in a timely manner to prevent and control them, otherwise it will seriously affect plant growth. Below, we will explain in detail how to prevent and control them.
Powdery mildew
Powdery mildew is the main disease of roses. After the appearance of powdery mildew, there will be protrusions on the leaves, and the protrusions will be white in color. In severe cases, the entire back of the leaves will appear moldy. It mostly occurs during the period from late autumn to early spring, and the large temperature difference between day and night and high temperature can easily produce pathogens, which can also affect the breeding and growth of flower buds. It is necessary to spray 25% potassium permanganate solution in a timely manner, or spray 800 times the amount of chlorothalonil, cut off diseased leaves and branches, and dispose of them in a centralized manner. Regularly spray water on the leaves.
Downy mildew
After being infected with downy mildew, the growth of leaves, flower branches, buds, and new branches of roses will be affected. The leaves will turn purple or brownish black, and there will be spots that will eventually wither and fall off. It mostly occurs in the spring and autumn seasons, with warm and humid climates and high air humidity. Poor ventilation will become more and more severe, and 72% Kelu can be sprayed for prevention and control until the disease disappears. When treating downy mildew, irrigate some thin nitrogen fertilizer water in moderation to promote the rapid recovery and growth of leaves and plants by absorbing nutrients.
Dry branch disease
Dry branch disease is a common disease in roses, which can cause the leaves and branches to wither or even die. After discovering the diseased branches and leaves, use scissors to cut them off and incinerate them, then spray with a diluted 600-800 fold carbendazim wettable powder for control until the plant resumes growth.
Aphids
Aphids can appear all year round, causing the leaves to turn pale and curl up. If aphids are found, they can be promptly sprayed with 800-1000 times the concentration of omethoate solution for prevention and control. Spray every 2-3 days until all aphids are killed. The best spraying location for spraying drugs is on the back of the leaves and the growth point. It is also possible to use dichlorvos for prevention and control, but do not use it during flower bud cultivation.
Red spider
Red spider mites can absorb chlorophyll from rose leaves, affecting normal photosynthesis and causing slow plant development. This is often caused by high temperature and humidity in the growing environment. It is more common in summer and can be controlled by spraying 1000-1500 times the concentration of sharp mites or 600 times the concentration of dead mite solution.
Original article author：Fragrant Road Full，If reprinted, please indicate the source.：https://www.theroadfull.com/article/3738.html
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