Diseases and prevention methods of canna

Diseases of Canna: Black Spot

symptom

Black spot is one of the common diseases of canna. It is generally more serious from June to August during cultivation. Dead spots will appear on the surface of the leaves, and there will be black mist at the spots on the back of the leaves. The disease first occurs on the leaf edge or leaf end, and then spreads to the center of the leaf.

Prevention and treatment methods

Before planting the bulbs, soak them in 800 times diluted 50% thiophanate-methyl wettable powder for 5-10 minutes to prevent disease.

At the early stage of the disease, cut off the diseased leaves and burn them, and spray 75% thiophanate-methyl wettable powder once every 7-10 days for 2-3 times to inhibit the development of the disease.

Diseases of Canna: Mosaic Disease

symptom

In the early stages of mosaic disease, mosaic or yellow-green spots will appear on the leaves of canna, the petals will gradually become smaller, the color will gradually become chaotic, and broken color stripes will appear.

The disease gradually becomes more serious in the later stages, the leaves become deformed, curled inward, and patches of necrosis occur.

Prevention and treatment methods

Since canna reproduces by root division, viruses can be easily passed on from year to year, so when reproducing, it is advisable to choose virus-free mother plants as the breeding body. If diseased plants are found, they should be removed and destroyed immediately to reduce the source of infection.

Mosaic disease is spread by aphids, so pesticides need to be used to control aphids when the disease occurs. Generally, 2000 times diluted 40% omethoate, or 1000 times diluted 50% malathion, 20% diazinon, and 70% propiachlor are sprayed.

Diseases of Canna: Bud Rot

symptom

It usually occurs when canna leaves out and before it blooms. The bacteria of bud rot will invade through the stomata of young leaves and flower buds. After the canna leaves out, many dot-like spots will appear on the leaves, and they will gradually expand and finally connect into large striped spots.

The spots are grayish white at first and then turn black. The diseased flower buds will die before blooming, and the spots will gradually move downward in the later stage. Causes death of young stems.

When old leaves are affected, the lesions expand slowly, are irregular in shape, yellow in color, and have water-soaked edges.

Prevention and treatment methods

Choose healthy rhizomes as propagation materials. For rhizomes suspected of being infected, soak them in 500-1000 times diluted streptomycin for 30 minutes before planting. This can not only prevent diseases but also promote the growth of buds and branches.

It is advisable to plant it in an area with sufficient sunlight, fertile and moist soil, and good drainage, and avoid over-dense planting.

In the early stage of disease, spray Bordeaux mixture (1:1:200) or 500 times diluted 77% chlorpyrifos wettable powder, 400 times diluted 14% copper chelate aqueous solution, etc.

Remove seriously diseased plants at any time and burn them.