Rhubarb is susceptible to a number of diseases and pest attacks. Diseases affect the leaves and petioles of the plant, and insects can completely destroy the crop. In order to prevent the death of the culture, it is necessary to determine the symptoms of the lesion in time and apply appropriate treatment methods.
Diseases Affecting Rhubarb
Diseases that affect rhubarb never occur on their own. Their development is facilitated by certain factors, including:
- increased soil moisture;
- arid and hot weather;
- sudden changes in temperature;
- excess nitrogen in the soil;
- planting too often in the same place.
To cope with the disease, you need to not only correctly identify its symptoms and choose a treatment, but also eliminate the cause of its occurrence.
Ramulariosis
The main symptoms are:
- the appearance of round spots on the leaves of the plant;
- the color of the spots is brown with a reddish tinge, at the edges they are surrounded by a dark border;
- spots tend to increase and merge, which leads to drying out of the leaves;
- petioles become stiff, as if wooden;
- on the inside of the sheet you can see a gray coating.
The causative agent of ramulariosis is a frost-resistant fungus. He hibernates in the soil, using the dead leaves of the plant to maintain his life.
To combat ramulariosis, it is necessary to spray the plant with copper sulfate or Bordeaux mixture. You can use Kaptan or Polycarbacin. They contain copper, which the fungus is afraid of.
It is recommended to start treatment if the disease has just begun to affect rhubarb. If she has captured more than 1/3 of the sheet, then it makes sense to remove and burn it. This will prevent the spread of infection.
Since cool weather and a high level of humidity contribute to the increase in the number of fungal spores, it is advisable to limit the watering of the plant. This will reduce the risk of infection multiplying.
Ascochitosis
Symptoms of the disease:
- blackening of the rhizome of the plant and its weakness;
- drop of rhubarb;
- the appearance on the leaves of yellow spots resembling burns;
- as the disease progresses, the spots increase in size, become dark;
- the leaves begin to crumble and fall.
The causative agent of the infection is the fungus. It is difficult to deal with the disease, as it reacts poorly to the effects of fungicides. The most effective means is the Bordeaux mixture with a concentration of 1%. She is sprayed with leaves of the plant at an early stage of development of ascochitosis. You can also use a mixture of urea and copper sulfate. The stems are sprinkled with powder based on chalk and copper. If the disease progresses, then rhubarb will not be able to save.
To prevent the appearance of a fungus, rhubarb is watered in the evening and only with warm water. It is necessary to remove leaves with the first signs of damage in time.
Rhubarb can only be planted in healthy soil. If there were cases of ascochitosis on the site, it is necessary to pre-treat the soil with siderates and fungicides, including Vincit, Tiram, Saprol. The area on which sick rhubarb grew can be planted with rye.
All plants infected with the fungus must be removed along with the rhizome. They are burned as far as possible from planting. The infection is highly resistant and can for a long time remain viable even in dry stems and leaves.
Powdery mildew
Symptoms of the disease:
- the appearance on the leaves of a white rough coating;
- slowing down the growth of the plant, as the infection progresses, it completely stops;
- the leaves become dark, after which their death occurs;
- flowering does not occur; in winter, rhubarb perishes.
Powdery mildew makes itself felt in early summer. Its distribution is facilitated by cool and humid weather, excessive watering and dense planting. Disputes spread easily. They can enter the plant through the air, through irrigation water, and even through the hands of a person.
The best drugs to combat powdery mildew are Alirin-B, Gamair, Planriz. You can prepare the treatment solution yourself by mixing 5 l of water, 25 g of soda and 5 g of liquid soap. It is applied to the stems, leaves and on the topsoil once every 3 weeks. To combat the disease in the early stages of its development, a weak solution of potassium permanganate is used.
To prevent the appearance of powdery mildew and preserve existing plants, it is necessary to put in order the agricultural technology of growing rhubarb. Water it only after the topsoil has completely dried out. Thinning landing, trying to remove infected stems. Be sure to reduce the amount of nitrogen fertilizer.
Rust
Symptoms of the disease:
- the appearance on the leaves of small convex growths that have a dark yellow color resembling rust;
- growths contribute to the evaporation of moisture and lead to drying and falling of leaves;
- as infection progresses, the bulges are opened, parasites spill out of them, which enter the soil and infect healthy plants.
The sooner treatment is started, the more effective it will be. If the infection has affected only a few leaves, it is easier to remove and burn them. When it has multiplied, it is necessary to resort to the help of specialized drugs:
- Topaz;
- Fitosporin;
- Baktofit;
- Bordeaux mixture 1%;
- Abiga Peak.
Spray rhubarb in 2 sets, with an interval of a week. Processing is carried out on a warm sunny day.
To prevent the spread of rust, it is necessary to properly care for the site. After harvesting, you need to remove the remains of plants from the ground. In autumn, the soil must be dug up. To increase the rust resistance of rhubarb seeds, they are etched before planting in a potassium permanganate solution.
Pests Affecting Rhubarb
Pest can attack rhubarb. Many insects want to be saturated with the lush green of the plant.
Rhubarb Weevil
The bugs have a body length of about 6 mm. They can be seen with the naked eye. The body of the insect is covered with gray scales. A distinctive feature of the weevil is the presence of a long proboscis.
The insect has excellent stamina. Bugs are able to survive in any places where rhubarb grows. Their presence can be suspected by the presence of dark yellow eggs, which are located in the petiole. In early spring, insects feed on buckwheat and sorrel leaves, after which they transform into pupae. Pests hatched from them are transferred to rhubarb.
The leaves of the plant damage both beetles and larvae. They gnaw through through holes. Larvae eat around the surface layer of leaves, and adult insects leave only veins behind them.
It is difficult to deal with bugs, since it will not work to treat the plant with chemicals. Otherwise, they can not be eaten. Application of specialized products is possible only on seed beds. Most often, Phosphamide 40% is used.
A preventive measure is competent planting. So that the insect does not move from buckwheat and sorrel, they are never planted next to rhubarb.
Potato scoop caterpillars
For rhubarb, the danger is represented by the larvae of the potato scoop. One insect can lay up to 75 eggs, and up to 500 clutches per season. In the spring of them will appear a whole horde of caterpillars. They attack not only rhubarb, but also other cultivated plants: onions, tomatoes, corn, garlic.
Caterpillars begin to eat with the onset of the evening. They destroy rhubarb stalks and foliage, after their invasion, only veins can remain from the plant. Clutches can be found in the stalk area.
Lepidocide and Bitoxibacillin are used to control caterpillars. Apply drugs 1 time in 7 days. Damaged petioles and stems are cut out and burned.
Chemical treated rhubarb is unsuitable for food. To resort to the help of toxic substances is necessary only in extreme cases.
To keep the crop, the larvae must be collected manually. You can use the infusion on the leaves of burdock. It is kept for 3 days, after which rhubarb is sprayed.
In order not to have to apply chemicals to plants, it is necessary to take measures to prevent the appearance of scoops. This requires regular weed control, because it is near them that butterflies lay their eggs. They feed on flowering weed grass.
Rhubarb bug
The bug has a bright abdomen and a diamond-shaped body. On the head of the insect are long antennae. The pest eats the juice of the plant, leaving characteristic brown spots on the leaves.
You can cope with an insect with the help of Phosphamide, Fufanon, Actellik. However, it is impossible to eat plants after applying pesticides on them. Therefore, it is best to resort to more gentle processing methods, among which:
- Spraying with a solution of mustard. For 500 ml of water, 100 g of powder is needed. When it is completely dissolved, add about 9 liters of water and apply to rhubarb leaves from 2 sides.
- Processing concentrated broth of onion peel.
- Spraying with a decoction of cloves. Its smell repels many insects well.
Experienced gardeners recommend breaking off stalks of rhubarb. Their smell will not attract bugs and other insects.
To prevent the occurrence of bugs, it is necessary to collect fallen leaves and other plant debris and burn them just before the frost. The soil must be dug up.
To collect a healthy and rich harvest of rhubarb, it is necessary to prevent the propagation of pests and fungi on the site. If they still attacked the plant, they should not be delayed with treatment. The sooner it is started, the higher the chances of seeing healthy and juicy grass on your desk.