Canna mosaic virus disease is a common disease

Canna

Mosaic virus disease is one of the most common diseases of canna. The incidence rate of canna grown in East China and South China is higher than that in northern regions. So what should be done once canna is infected with this disease? The specific solutions are as follows.

I. Symptoms

In the early stage of the disease, the leaves of affected canna show small chlorotic spots or mosaic patterns; in severe cases, the leaves become deformed, curled, yellowed, and even withered, and the plants become stunted; the symptoms are especially severe in varieties such as common canna, Canna generalis, and Canna glauca; red-flowered canna is relatively disease-resistant, with variegation forming on the petals. Canna planted in Beijing shows yellow-green or alternating light and dark green stripes, and the plants are stunted.

II. Pathogen

The pathogen causing canna mosaic virus disease is cucumber mosaic virus (CMV). The virus particles are icosahedral, with a diameter of 28-30 nm; the thermal inactivation point of the sap is about 70°C; the dilution endpoint is 10-4; the longevity in vitro at below 20°C is 3-6 days. In addition, relevant departments in China have also isolated Canna dwarf viroid from mosaic virus diseased plants, initially identified as the pathogen of yellowing-type symptoms.

III. Transmission routes

Virus-carrying mother plants on canna are an important source of the virus, and division propagation is an important route of spread. Field transmission occurs through aphids. An aphid can acquire the virus after feeding on a diseased plant for 1 minute, and can transmit the virus after feeding on a healthy plant for 1 minute. The effective time of the virus in the insect body does not exceed 4 hours. Contact between diseased and healthy plants and field operations can also transmit the virus.

IV. Disease occurrence pattern

Cucumber mosaic virus overwinters in diseased tubers and is spread over long distances by diseased tubers. Canna mosaic virus disease occurs extremely commonly. Because vegetative division propagation is used, the virus is passed down from generation to generation, worsening year by year. The main routes of transmission of cucumber mosaic virus and canna mosaic virus are aphids and sap contact transmission, especially cotton aphids and corn aphids, which transmit the virus in a non-persistent manner. It is easily inoculated by sap; for example, using the rubbing inoculation method, it can produce viral disease symptoms on plants such as Nicotiana glutinosa, Nicotiana tabacum, cucumber, Chenopodium quinoa, Datura stramonium, Chenopodium amaranticolor, Gomphrena globosa, cowpea, and broad bean. There are certain differences in disease resistance among different canna varieties. Common canna, Canna generalis, and Canna glauca are severely affected, while red-flowered canna has strong disease resistance.

V. Control methods

1. Eliminate toxic tubers and do not use virus-carrying rhizomes as propagation material. When digging up tubers in autumn, discard those whose aboveground parts show mosaic symptoms. Because canna is propagated by division, the virus is easily passed on year after year, so when propagating, it is advisable to select virus-free mother plants as propagation material. Immediately pull out and destroy diseased plants to reduce sources of infection.

2. This disease is transmitted by aphids. Use insecticides to control aphids and reduce transmission vectors. Spray with 40% omethoate 2000-fold solution, or 50% malathion, 20% diazinon, and 70% pirimicarb each at 1000-fold solution. Use pesticides such as carbaryl and malathion to control virus-transmitting aphids; CMV has many virus source plants, which should be removed in time.

Common diseases of canna

Canna mosaic virus disease


Canna mosaic virus disease is a common disease of canna and occurs commonly in areas where canna is planted in China.

Symptoms: Mosaic patterns or yellow-green mottling appear on the leaves of infected plants, the petals become smaller and form variegated colors, and when the disease is more severe, the leaves become deformed, curl inward, and the spots become necrotic.

Pathogen and disease occurrence pattern: Canna mosaic virus disease is caused by cucumber mosaic virus (CMV). The main routes of transmission are aphids and sap contact transmission. There are certain differences in disease resistance among different canna varieties. Common canna, Canna generalis, and Canna glauca are severely affected, while red-flowered canna has strong disease resistance.

Control methods: 1. Because canna is propagated by division, the virus is easily passed on year after year, so when propagating, it is advisable to select virus-free mother plants as propagation material. Immediately pull out and destroy diseased plants to reduce sources of infection. 2. This disease is transmitted by aphids. Use insecticides to control aphids and reduce transmission vectors. Spray with 40% omethoate 2000-fold solution, or 50% malathion, 20% diazinon, and 70% pirimicarb each at 1000-fold solution.

Canna bud rot



Symptoms: Before canna unfolds its leaves and flowers, bud rot bacteria invade through the stomata of young leaves and flower buds and cause damage. When the leaves unfold, many small spot lesions appear on the leaves and gradually expand, connecting with each other along the leaf veins to form large spots; sometimes the lesions form stripes. The lesions first appear grayish white and quickly turn black. Infected flower buds turn black and die before flowering. The lesions can extend downward along the petiole, causing young stems and buds to die. When old leaves are affected, the lesions expand slowly, are irregular in shape, yellow, and have water-soaked edges.

Pathogen: Xanthomonas sp., belonging to the family Pseudomonadaceae. The bacterial cells are single, rod-shaped, with a single polar flagellum, Gram-negative, and obligately aerobic. This bacterium overwinters on canna rhizomes, and young plants in greenhouses are affected earlier.


Control methods: 1. Select healthy rhizomes as propagation material. For rhizomes suspected of carrying bacteria, soak them in 500-1000-fold streptomycin solution for 30 minutes before planting, which can both prevent disease and promote the growth of buds and branches. 2. It is advisable to plant in a sunny, fertile, moist, and well-drained location, and avoid planting too densely. 3. In the early stage of plant disease, spray Bordeaux mixture (1:1:200) or 77% Kocide wettable powder 500-fold solution, 14% copper ammonia complex aqueous solution 400-fold solution, etc. 4. Remove severely diseased plants and diseased residues at any time and burn them.

Common diseases of canna and solutions

Canna has bright and eye-catching flower colors and a long flowering period, making it one of the excellent flower varieties for beautifying the environment. Some diseases also occur during canna care. Let us learn about them below:

Canna diseases:

Canna diseases: 1. Black spot

Black spot is one of the common diseases of canna. Under conventional cultivation, the disease is severe from June to August, with large dead spots. There is a black mist-like substance on the lesions on the back of the leaves. The disease first occurs from the leaf margin or leaf tip and then develops toward the center of the leaf.

Solutions:Before planting bulbs, soak them in 50% thiophanate-methyl wettable powder 800-fold solution for 5-10 minutes to prevent the disease. In the early stage of the disease, cut off diseased leaves and burn them, and spray 75% chlorothalonil wettable powder once every 7-10 days for 2-3 consecutive times, which can inhibit the development of the disease.

Canna diseases: 2. Mosaic virus disease

Mosaic virus disease is a common disease of canna. When it occurs, mosaic patterns or yellow-green mottling appear on the leaves of the plants, the petals become smaller and form variegated colors, and when the disease is more severe, the leaves become deformed, curl inward, and the spots become necrotic.

Solutions:Spray with 40% omethoate 2000-fold solution, or 50% malathion, 20% diazinon, and 70% pirimicarb each at 1000-fold solution. 

Canna diseases: 3. Bud rot

Before canna unfolds its leaves and flowers, bud rot bacteria invade through the stomata of young leaves and flower buds and cause damage. When the leaves unfold, many small spot lesions appear on the leaves and gradually expand, connecting with each other along the leaf veins to form large spots; sometimes the lesions form stripes. The lesions first appear grayish white and quickly turn black. Infected flower buds turn black and die before flowering. The lesions can extend downward along the petiole, causing young stems and buds to die. When old leaves are affected, the lesions expand slowly, are irregular in shape, yellow, and have water-soaked edges.

Solutions:Before planting, soak in 500-1000-fold streptomycin solution for 30 minutes to control the bacteria. In the early stage of the disease, spray Bordeaux mixture (1:1:200) or 77% Kocide wettable powder 500-fold solution, 14% copper ammonia complex aqueous solution 400-fold solution, etc. In severe cases, remove severely diseased plants and diseased residues and burn them.

Canna diseases: 4. Leaf roller insect pests

Canna is highly adaptable, but from May to August every year, attention should be paid to leaf roller insect pests to avoid damage to its tender leaves and inflorescences.

Solutions:Spray with 50% dichlorvos 800-fold solution or 50% fenitrothion emulsifiable concentrate 1000-fold solution for control.

Canna flowers are large and their colors are bright and eye-catching. Growing them in home courtyards and other places will bring unexpected beautification effects. When growing canna, attention should be paid to the occurrence and treatment of common canna diseases. The editor has summarized the solutions to common canna diseases for everyone, hoping to be helpful to everyone.