A Detailed Guide to Common Lily Diseases and Their Control Methods

1. Bulb and scale rot and stem diseases caused by Fusarium

Symptoms: In plants with bulb and scale rot, growth is very slow and the leaves are pale green. Underground, brown spots appear at the top of the scales, on the sides, or where the scales join the basal plate, and these spots gradually begin to rot. If the basal plate stem is infected, the entire bulb will rot. The stem and leaf diseases caused by Fusarium are diseases that infect the above-ground parts. The identifying sign is that the basal leaves turn yellow before reaching maturity, and the yellowed leaves turn brown and drop off. On the underground part of the stem, orange to dark brown spots appear, which then enlarge and finally extend into the interior of the stem. The stem then rots, and finally the plant dies before reaching maturity.

Control: Thoroughly disinfect the infected soil.

2. Rhizoctonia diseases

Symptoms: If the infection is mild, it only harms the leaves in the soil and the green leaves at the lower part of young shoots, with sunken light brown spots appearing on the leaves. Generally speaking, although the growth of the plant is somewhat affected, it can still continue to grow. In severely infected plants, the growth of the upper part is hindered, and the white leaves of the underground part as well as the leaves at the very base of the above-ground part will rot or wilt and drop off, leaving only brown scars on the stem.

Control: Disinfect soil that is suspected of being infected with a soil disinfectant, and after disinfection ensure that the soil is no longer infected; if the previous crop has already shown infection, general soil disinfectants cannot be used, so before planting treat the soil in advance with a fungicide for controlling Rhizoctonia (fully incorporating it into the soil to a depth of 10cm).

3. Phytophthora diseases

Symptoms: Foot rot of the plant (Phytophthora) will hinder growth or cause it to suddenly wilt. Soft rot develops at the infected area at the base of the stem, becoming dark green to dark brown, and spreads upward, the leaves turn yellow, and discoloration begins at the base of the stem. Similar soft rot infections also often occur on the above-ground stem, causing the stem to damp off or bend.

Control: Disinfect infected soil with a general soil disinfectant; during cultivation, fungicides that control Pythium can also effectively control foot rot; ensure that the soil has good drainage conditions; prevent the crop from remaining in a wet state for a long time after watering; in summer the soil temperature should be as low as possible.

4. Pythium diseases

Symptoms: This type of fungus attacks both individual plants and plants within an area. The plants are stunted, the lower leaves turn yellow, the upper leaves become narrower, the leaf color is paler, and they often wilt. In plants affected by root rot, the flower buds shrivel. When the plant is pulled up, transparent, light brown rotting spots can be seen on the bulb and root crown; or they become completely soft and rotten.

Control: Disinfect infected or suspected infected soil with a general soil disinfectant; keep the soil temperature low in the early stage of cultivation, and throughout the cultivation period adopt correct cultivation procedures: cultivation in boxes filled with potting soil and peat can keep Pythium under control.

After the crop has emerged, or in cases where Pythium infection may already have occurred, fungicides for controlling Pythium that are easy to spray onto the crop can be used, preferably in the evening. Spraying water for a few minutes (about three minutes) before applying the fungicide will significantly enhance the effect of the fungicide, and can also rinse the crop clean.

Preventing disease is more important than treating it, and every healthy plant is essential. People get sick through the mouth, while plants get sick through the roots, so maintaining a good root system of the plant is crucial, and this requires soil free of pathogens and with good air permeability.