How to prevent and control Rieger begonia diseases? A full analysis of practical tips

Because Rieger begonia is a greenhouse flower, it is susceptible to pests and diseases and is relatively difficult to grow. Today we will share with you tips for preventing and controlling Rieger begonia diseases.

Tips for preventing and controlling Rieger begonia diseases

I. Mosaic disease

1. Symptoms

Rieger begonia shows yellow mottling on the leaves, with relatively large, round brown necrotic spots, and the veins on the petioles turn brown and necrotic. The pathogen is Impatiens necrotic spot virus, also known as Tomato spotted wilt virus 1, TSWV-1. In nature, the transmission vector is thrips.

2. Control methods

① Clear weeds along paths and field edges that may serve as sources of infection.

② Control thrips to prevent virus transmission.

II. Gray mold

1. Symptoms

Gray mold usually appears on the lower leaves of cuttings that are in contact with the potting medium. Water-soaked spots rapidly expand and infect most of the leaf or even the entire cutting. As time passes, the infected area becomes necrotic and turns brown-black to black. When night temperatures are relatively low, day temperatures are relatively high, and humidity is also high, the pathogen easily forms spores on the leaves and produces gray-green conidial masses.

2. Control methods

When the greenhouse is closed in winter, controlling gray mold is especially important. Manage the microclimate well and keep the air circulating; keep leaf surfaces dry at night and reduce humidity; fungicides such as Yili and Huimei Suke can be sprayed.

III. Bacterial leaf spot

1. Symptoms

This disease often occurs on begonias, and some growers do not even realize it is a disease. Rieger begonia is particularly sensitive to this pathogen, usually showing leaf margin necrosis and wrinkling. In the early stage of the disease, transparent small spots appear on the underside of the leaves, and then the number of lesions increases rapidly and the small spots expand into water-soaked spots.

2. Control

There is no specific cure for this disease. The best way to control it is first to select cuttings that do not carry this disease. For infected plants, if the infection is relatively mild, only the infected parts need to be removed; if the condition is severe, the entire diseased plant must be removed to reduce the development and spread of this disease. In addition, using fertilizer at a concentration slightly higher than recommended will also help reduce the disease.

IV. Fungal leaf spot

1. Symptoms

Spots usually appear on leaf margins, leaf tips, and broken veins. The necrotic areas are dark brown and initially appear water-soaked. Inspecting the base of the leaf surface generally reveals irregularly shaped, black clumps and a ring of white mycelium.

2. Control

Apply fungicides; reduce damage; fertilize at the recommended concentration to reduce the harm of this pathogen.

V. Fusarium

It is only discovered when the fungus covers a relatively large part of the plant. This disease originates from the medium, invades the roots, and reaches the top of the plant through the vascular bundles. Once the fungus enters the vascular bundles, the plant begins to show symptoms: the growing point and leaves darken, and large patches of brown wet rot appear on the stems, later becoming dry rot. After a few days, white fungal mycelium appears on the outside of the stems. Fusarium is highly related to Fusarium oxysporum, because these fungi both behave as vascular parasites. Once the disease occurs, it cannot be controlled, and producers can only try to ensure sanitation as much as possible during work.

VI. Downy mildew

This type of fungus is easy to spot. White fungal mycelium can be seen on the top of the leaves. These fungi spread by themselves into circular shapes and can be wiped off. In severe infections, fungal mycelium appears on the underside of the leaves, and these spots later turn brown with black spots on top. It usually occurs first on older leaves and infects when environmental humidity is relatively low, especially at greenhouse vents. The control method is: when air flow is too fast and conditions are relatively dry, use a sulfur evaporator at night, so that a thin layer of sulfur covers the plant surface, thereby inhibiting fungal growth.

VII. Rhizoctonia solani

If infected cuttings are not treated promptly, the infected spots will rapidly spread across the entire cutting bed. Rhizoctonia solani infects plants or cuttings where the medium meets the air, and film-covered cuttings are most susceptible. The control method is to use clean medium and clean water and to promptly handle infected plants.