What if the rose is infected with powdery mildew?

Schematic diagram of rose powdery mildew

Rose powdery mildew is a common and difficult-to-treat fungal disease, which has a high incidence in spring and autumn. once rose is infected with the disease in gardens and parks, it will lose not only ornamental value but also a loss of wealth. However, finding the root cause is the key to the treatment of rose powdery mildew, so what should be done when the rose is infected with powdery mildew?

1. Pathogen and incidence regularity

The pathogen is Rosa monomycetes. The mycelium develops on the surface of the host and absorbs nutrients by extending the haustorium into the plant epidermis. The conidia are short, erect, apical with conidia, colorless, ovoid or barrel-shaped, 5-10 series, overwintering mainly as hyphae in the dormant buds of susceptible plants, and covered with white powder as soon as the buds unfold in the next spring. These conidia are transmitted to the young tissue by the wind, germinate under suitable environmental conditions, and harm through the cuticle and epidermal cell wall into the epidermal cells. The pathogen is fungi, which has no odor after onset, and white powder is its obvious symptom.

Powdery mildew is generally easy to occur in warm, dry or humid environment, but rainfall is not conducive to the occurrence of the disease. The disease is easy to occur when too much nitrogen fertilizer is applied and the soil is lack of calcium or potassium fertilizer, the plant is too dense, the ventilation and light transmission is poor, and the disease is serious. Drastic changes in temperature and over-dry soil in flowerpots will reduce the swelling and pressure of host cells, which will weaken the disease resistance of plants and be conducive to the occurrence of diseases.

Second, symptoms

Leaves, petioles, buds and tender parts can be damaged. In the early stage, chlorotic macula appeared on the leaves, which gradually expanded, and then there was a layer of white powder, and in severe cases, the whole leaf was covered with a layer of powdery powder. After the young leaves are infected, the leaves curl, wrinkle, thicken, and sometimes purplish red. When the petiole and tender tip were infected, the injured part expanded slightly and bent to the opposite side. When the bud is infected, the surface is covered with powdery mildew layer, the flower posture is abnormal, and the flowering is abnormal or unable to blossom.

III. Ways of transmission

Powdery mildew of rose overwintered with mycelium on diseased buds, diseased leaves or diseased branches. In some areas, it could survive the winter with closed cysts, and the following year, ascospores or molecular spores were used for the first infection. It spreads with the wind and invades directly from the epidermis or stomata. The disease occurs quickly in the warm and humid season. The resistance of rose varieties to powdery mildew was different. Generally, light-growing, trailing and multi-flowering varieties were more resistant to powdery mildew, but the disease resistance was often lost due to the production of new physiological races.

Chinese rose

IV. Prevention and control methods

l. Pruning and destroying all dead susceptible branches in early spring can reduce the source of infestation. Early diseased leaves should be removed as soon as possible.

two。 When growing in greenhouse, ventilation should be increased so that the humidity is not too high. Excessive nitrogen fertilizer should be avoided when applying fertilizer, and phosphorus and potassium fertilizer should be applied appropriately.

3. When using chemical control, the spraying should be comprehensive and thoughtful, protect the young parts, and increase the spraying times during the peak growth period and rainy season of the new shoots. At the beginning of the disease, you can choose 1500 times of the wettable powder, or 2000 times of the EC, or 2000 times of the suspension, or 50% methyl topiramate and 75 chlorothalonil wettable powder every 7 days. Spray 2 times in a row for 3 times.

V. matters needing attention

1. If it rains within 4 hours after application, it needs to be sprayed again.

two。 If there is a slight precipitation is normal, does not affect the efficacy, just shake well when using.

VI. Essentials of plant protection

1. Keep the field ventilated and transparent, reduce the field humidity, deeply turn the ground to kill stubble, promote the diseased body to decompose the disease period, and remove the diseased plant residue, diseased fruit, diseased leaf, diseased branch and so on in time.

two。 No partial application of nitrogen fertilizer, increased application of phosphorus and potassium fertilizer, cultivate strong seedlings, in order to improve the disease resistance of the plant itself.

Whether human beings, animals and plants, as long as they suffer from fungal diseases, it is generally difficult to cut off their roots, so we must not ignore the powdery mildew of rose flowers, bearing in mind the principle that prevention is greater than cure.

Prevention and control of rose powdery mildew is a common disease in rose. The harm is quite serious in some areas. Symptomatic leaves, petioles, buds and tender parts can be damaged. In the early stage, chlorotic macula appeared on the leaves, which gradually expanded, and then there was a layer of white powder, and in severe cases, the whole leaf was covered with a layer of powdery powder. After the young leaves are infected, the leaves curl, wrinkle, thicken, and sometimes purplish red. When the petiole and tender tip were infected, the injured part expanded slightly and bent to the opposite side. When the bud is infected, the surface is covered with powdery mildew layer, the flower posture is abnormal, and the flowering is abnormal or unable to blossom. The pathogenic bacteria are Sphaerotheca pannosa (Wallr.) Lev. The closed capsule is spherical to pear-shaped with a diameter of 85 μ m and 120 μ m. Accessory hyphae, few and short, dark brown, septate. It contains 1 ascus, which is oval to spherical in width and 88~115X69~75 micron in size. There are 8 ascospores with a size of 20 "27X 12" 15 microns and a wide oval shape. The asexual generation is Oidium leucoconium with conidia in series. The pathogen of powdery mildew of rose overwintered by mycelium on diseased buds, diseased leaves or diseased branches. In some areas, it could survive the winter with closed cysts, and the ascospores or molecular spores were used as the first infection in the following year. It spreads with the wind and invades directly from the epidermis or stomata. The disease occurs quickly in the warm and humid season. The resistance of rose varieties to powdery mildew was different. Generally, light-growing, trailing and multi-flowering varieties were more resistant to powdery mildew, but the disease resistance was often lost due to the production of new physiological races. The disease is more serious when there is too much nitrogen fertilizer and insufficient potassium fertilizer in the soil. Prevention and control methods 1, pruning and destroying all dead susceptible branches in early spring can reduce the source of infestation. Early diseased leaves should be removed as soon as possible. 2. When cultivated in greenhouse, ventilation should be increased so that the humidity is not too high. Excessive nitrogen fertilizer should be avoided when applying fertilizer, and phosphorus and potassium fertilizer should be applied appropriately. 3. When using chemical control, spraying should be comprehensive and thoughtful, protect the young parts, and increase the spraying times during the peak growth period and rainy season of new shoots. At the beginning of the disease, you can choose 1500 times of the wettable powder, or 2000 times of the EC, or 2000 times of the suspension, or 50% methyl topiramate wettable powder and 75 {chlorothalonil wettable powder, etc., spray once every 7 days. Spray 2 times in a row for 3 times. What are the common diseases and insect pests control of rose?

Rose is a kind of ornamental plant that many people like, but during breeding, it often finds some diseases and insect pests, which will not only reduce the ornamental value of rose, but also make rose die directly when it is serious. so how should these diseases and insect pests be prevented? How should they be treated after they occur? The following editor will specifically talk about this issue for you.

1. Rose powdery mildew

Powdery mildew is one of the most common diseases of Chinese rose. After it occurs, the leaves will fall off, the buds will be deformed or can not open, and it will directly affect the growth of rose. The best way to prevent this disease is to reduce the source of infection. Pruning the diseased sheep and leaves in time, and destroying them, and after leapfrogging into the dormant period, it should be sprayed with Sibomei, so that the overwintering hyphae in the sprouts can be eliminated. It can effectively reduce the occurrence of rose powdery mildew.

2. Black spot of rose

Black spot is also one of the high incidence diseases of rose, after the occurrence of this disease, mainly in the leaves and petioles of rose and oats and other parts, in the initial stage, the leaf front of rose will appear brown spots, with the aggravation of the disease, will slowly spread into round or irregular disease spots, the color of disease spots are mostly dark purple. In order to prevent and cure the occurrence of this disease, we can thoroughly remove the dead branches and leaves in autumn, cut off the diseased branches in time to destroy them, and spray pentaclofenac sodium solution during its dormant period, which can effectively eliminate the overwintering bacteria on the rose.

3. Grey mildew of rose

Botrytis cinerea is also a high incidence disease. After its occurrence, disease spots will appear in the flowers, buds and young stems of rose, and a large number of gray mold layers can be produced in the affected area in a warm and humid environment. In order to prevent Botrytis cinerea of rose, withered leaves should not be used to protect roots in autumn. when cultivated in greenhouse, attention should be paid to ventilation to avoid excessive humidity and to remove infected diseased flowers and sprouts. After the occurrence of rose mildew, 75% chlorothalonil wettable powder can be sprayed for 2 to 3 times in a row, so that menstruation can be significantly controlled.