The worst thing that can happen in a garden is when you lose your favorite plant. One of the reasons that plants can perish is a disease. Hostas, like other plants, can be affected by different fungus, bacteria, or viruses.
Today we will talk about hosta diseases and how to fight them. I have collected the maximum information on this topic, and I want to present it to you in a convenient form. Also, there will be pictures of all the main diseases, and you can compare them with your cases.
First, I will briefly describe each disease in the form of a table with symptoms and methods of treatment. Next, we will talk about each of these cases in detail.
|Anthracnose (Colletotrichum)||Red-brown spots on leaves||Prophylactic spraying with fungicides|
|Petiole rot (Sclerotium rolfsii)||Yellowed leaves, broken petioles at the base||Removal of the damaged part of the plant, treatment with fungicide|
|Fusarium root and crown rot (FRCR Fusarium hostae)||The center of the crown and the rhizome are light brown||Removal of the damaged part of the plant, treatment with fungicide|
|Bacterial Soft Rot (Pectobacterium)||The petioles and center of the crown become soft and watery, with a bad smell||Remove the damaged part of the plant and treat it with a fungicide|
|Hosta Virus X (HVX)||Green spots on leaves, twisting leaves, slowing growth||Remove infected plants|
|Nematodes (Aphelenchoides spp.)||Dry stripes on the leaf||Remove infected leaves|
In summer, when the weather is warm, and there are it rains a lot, these are ideal conditions for the disease to develop. Anthracnose is caused by spores of various fungi and can cause severe damage to hostas. It is a prevalent disease, although it rarely causes the death of a plant.
The disease looks like brown spots on hosta leaves. The middle of the spot is dry. Over time, it expands and can connect with other spots, which can cause the leaf to die off.
If you want to defeat this disease, you must first remove the infected leaves and destroy them. Do not leave cut leaves to rot in your yard!
At the initial stage, if the plant is not tremendously affected by the disease, use Phyton spray. Apply to the whole bush and everything around. After a while hosta will recover.
At a later stage, you will need to use systemic fungicides whose instructions say that they can fight the disease. It is best to use products that contain chlorothalonil.
Preventive spraying with systemic fungicides is the most effective.
2. Petiole rot (Southern Blight)
Petiole rot is one of the most dangerous hosta enemies. It can destroy the plant fairly quickly, so prevention and early detection are the keys to success.
Spores of this fungus can stay in the ground for a very long time and not manifest themselves. When favorable conditions come, the disease multiplies rapidly and attacks the base of the petioles. This happens when the temperature exceeds 80 ° F, and the humidity is high.
The outward signs of this disease will be the yellowing of the leaves. Petioles break at ground level and fall. In the early stages, the petioles turn reddish. Also, in the places of rot near the rhizome can be seen yellow balls of small size.
Spores of this fungus love humid conditions, so mulch under hostas is the perfect environment for them. From this, we can conclude that mulching close to the rhizome is dangerous. There should be a gap of at least 1-2 inches between the petioles and the mulch.
At an early stage of detection, all parts of this fungus and the affected part of the plant must be carefully cleaned. Also, remove the top layer of soil around the hosta and replace it with fungus-free soil. Spray the plant, rhizome, and soil around by fungicide that is designed to fight this type of fungus (for example, Fungo or products that contain tebuconazole).
The best control strategy is the regular spraying of all plants in the garden with different types of systemic fungicides.
If you notice this disease too late and the plant is severely damaged, then there are no more options than to dig a hosta and move it with the soil away from your yard. Then carefully disinfect all tools and the place where the hosta grew.
3. Fusarium root and crown rot (FRCR)
This is another very dangerous and common disease. It is almost impossible to cure a plant. Spores of this fungus are found mainly in the ground. If they are exposed to an open wound, infection is guaranteed.
This disease is extremely dangerous because it can infiltrate into the crown and affect the entire plant. This distinguishes it from other illnesses that affect only part of the plant.
Initially, it is difficult to see the signs of the FRCR. In the spring, the leaves of hostas appear later, and it has a slower growth rate than a healthy plant. Also, the number of leaves and their size is smaller.
In the later stages of infection, the leaves turn yellow and gradually fade. The center of the crown has a light brown color.
If you dig a plant, you will notice that the number of roots is less and there is brown rot in the center of the rhizome.
Most often, the hosta becomes infected with this disease during reproduction by division. If the rhizome was divided with dirty tools or the wounds were not sprayed with fungicide, then the plant could become infected.
Before buying, check the roots for FRCR. Also, use a clean splitting tool and treat the wounds after dividing.
If the disease is detected at an early stage, then you can cut off the affected part of the plant, dip it in an aqueous solution of a fungicide containing thiophanate-methyl. Then you need to dry the plant a bit and dust the wound with crushed wood ash. Put hosta in a pot, use clean peat-based soil. After a while, there is a chance that the plant will recover.
If the entire plant is affected by this disease, it should be dug up and destroyed or removed from the yard.
4. Bacterial Soft Rot
Bacterial Soft Rot can destroy the plant. As you can see from the picture, the center of the crown is rotten, and the plant will not recover after that.
Like most diseases, the pathogens of Bacterial Soft Rot are in the ground and waiting for the right moment to develop. Most often, the infection occurs if in winter hostas are damaged by heavy frosts, and in the spring, the wounds have not yet healed. Through these damages, bacteria penetrate the plant and infect it.
Often the infection occurs during the dividing of the rhizome. If you separate hostas and do not follow all the requirements of sterility, then there is a high risk of infection.
The bacteria of this disease can infect a plant and not show up for some time. When favorable conditions come, the disease begins to develop and destroy the plant. Favorable conditions are high humidity and warm air temperature (above 80 ° F).
Symptoms of the disease are yellowing of the leaves, and the petioles become soft and lie down on the ground. The center of the crown becomes watery and soft.
The peculiarity of this disease is the specific dead fish smell.
If the plant was hit very badly, then it will not be possible to save it. However, if you find the disease initially, there is a chance that the plant will survive.
First, dig hosta out of the ground. Clean it and wash it with water. With a sterile knife, remove all damaged parts of the plant. Put it in the shade for a few hours. Next, place the plant in an aqueous fungicide solution (Phyton 35), let the plant be saturated with the solution.
Transplant hosta to a new location or pot. Use only clean soil.
5. Hosta Virus X (HVX)
Viruses are a very dangerous disease for hostas. It is impossible to cure an infected HVX plant. This virus was first discovered in 1996, and its origin is unknown.
The virus cannot exist outside the plant or insect. The infection is transmitted from an infected plant to a healthy one. The first way how the plant can be infected is when the pests damaged the diseased plant and then switched to healthy.
The second way is when you prune the stems of infected and healthy plants with one tool.
Another way of infection is sowing the seeds of an infected plant and, as a consequence, the transmission of the disease to seedlings.
The virus is also dangerous because it is not noticeable in the first year when the plant becomes infected. Therefore, you can multiply an infected plant and get new ones also infected.
The sign of this disease is green spots on the leaf. They can be both dark and light green.
In addition to stains, a sign of infection is a deformation of the leaf. Some infected plants may have yellow and twisted leaves. Also, the size and growth rate are decreasing.
Fighting this virus is useless. If the hosta is infected, it is not possible to cure it. Therefore, the first thing to do is to protect yourself from buying diseased plants. If you see similar symptoms on the plant you want to buy, don’t do it.
If the infection has occurred and an infected hosta is growing in your backyard, there are two options that you can do.
The first is that if only one or two leaves are infected, you need to transplant the hosta away from other hostas. Cut off the damaged leaves with a knife. When the job is done, the knife must be disinfected.
Usually, HVX does not kill the plant but only weakens it, so the hosta can live a long time if the infection is low. If you remove and burn the affected leaves, there is a chance that the plant will overcome the disease.
If the virus has severely damaged the plant, there is nothing to do but dig up the hosta, remove it from the yard, and burn it. By destroying the infested plant you will be doing all hosta lovers a favor because you will stop the spread of this scourge.
Leaf nematodes are small worms that move through the water. Most often, infection occurs during the rains. If the nematodes are near the hosta bush and it is raining heavily. Raindrops can throw these worms at the plant. Then they penetrate through the pores or affected parts of the plant.
Once inside, the nematodes hit the cells and start to multiply.
As you can see in the picture, dry stripes appear on the leaves, almost the entire length of the leaf. If the plant is heavily infested, the strips may be several, and the leaf may rot. The results appear several months after infection.
At the first sign of infection, immediately remove the affected leaves with the stems. Do not leave the leaves in the yard, but burn them immediately. The fact is that these pests can stay alive for a long time in rotting leaves. Also, after trimming, disinfect the entire tool.
Another thing that can be done to control foliar nematodes is to cut the stalks and leaves of hostas in late summer when it is still alive without waiting for it to turn yellow. Then these leaves must be destroyed. This method greatly reduces the population of nematodes.
Root nematodes penetrate the plant through the tips of the roots and lay eggs there. After hatching, the larva leaves the plant and migrates to the next.
As a result of the activity of these nematodes on the root, galls are formed, and the roots begin to grow in a bizarre form. Also, the leaves can dry at the edges, because the roots begin to absorb moisture poorly.
Unfortunately, there are no effective methods to deal with nematodes. You must remove diseased plants from your yard along with the ground.
Phytophthora foliar blight
Phytophthora foliar blight is a fairly common fungal disease. It can affect a large number of various plants, including hostas. The disease develops at high humidity and temperatures above 70 ° F. This disease can kill the plant fairly quickly.
Symptoms are rotting of the crown, faded, and brown leaves. Stems collapse near the rhizome and fall off.
Methods of control include sterility when working with plants and chemical control (spraying with fungicides).
Impatiens necrotic spot virus (INSV)
Impatiens necrotic spot virus is another infection that can infect your plants. It is distributed by various types of thrips.
Symptoms do not appear immediately. White patterns on a green leaf are the most typical sign. Necrosis of the leaf is also possible.
Control methods include disinfection tools and spraying plants with insecticides.
Tomato ringspot virus (ToRSV)
The Tomato ringspot virus causes the yellowing of chlorosis-like leaves. It distributed when propagating hostas by division. Also, this virus is transmitted by nematodes.
There are no effective control methods. The only thing you can do is remove the infected plants to avoid the spread of the virus.