What to Do When a Peace Lily Tree Develops Disease? Symptom Analysis and Treatment Methods

Disease Analysis of the Peace Lily Tree

I. Anthracnose

1. Symptoms

It mainly affects leaves at the seedling stage and on mature plants. When leaves are infected, it mostly occurs on the leaf surface, leaf tip, and leaf margin, appearing brown and irregular in shape, and later often expands or merges into large grayish-brown spots with brown, wavy edges; many small black granules form on the lesions, which are its acervuli. The conidia spread by wind and rain, and when humidity is high the spores germinate and invade the leaves or seedlings to cause damage; the disease is prone to occur during continuous rain, insufficient sunlight, heavy clay soil, or when moisture stagnates in greenhouses, and it is most prevalent from February to April.

2. Control Methods

If a small number of diseased leaves are found, remove and destroy them promptly; during the growing season, apply more phosphorus and potassium fertilizer to improve plant resistance; in the early stage of the disease, use 25% carbendazim wettable powder at 500 times dilution, or 60% carbendazim wettable powder at 700 times dilution, or 75% thiophanate-methyl wettable powder at 600 times dilution, sprayed alternately, once every 10-15 days, for 3-4 consecutive times.

II. Brown Spot Disease

1. Symptoms

It occurs on new leaves of the plant between April and May, beginning with oval yellow-brown lesions on the leaf surface, which then continuously expand, and more small black granules appear within the lesions on the upper side of the leaf, while the underside of the lesions is purple, so that the entire leaf yellows and wilts, causing the plant to drop a large number of leaves.

2. Control Methods

1% Bordeaux mixture can be used for prevention; if a small number of diseased leaves appear, remove and burn them promptly; in the early stage of the disease, use 50% carbendazim wettable powder at 500 times dilution, or 50% benomyl wettable powder at 1000 times dilution, or 50% Shajunwang aqueous solution at 1000 times dilution, sprayed alternately once every 10 days, for 3-4 consecutive times.

III. Brown Root Rot

1. Symptoms

The leaves of diseased trees gradually turn yellow and droop, and in severe cases turn brown and dry up, the stems lose water and shrink, and the root system turns brown and rots; the diseased plants die within a short period. Diseased roots, diseased soil, and leftover diseased plant debris are the primary infection sources of this disease, transmitted by wind and rain or by contact, and it generally occurs in individual plants.

2. Control Methods

Severely diseased plants and plants that have died from the disease should be pulled out with their roots and burned, and disinfected with 50% carbendazim wettable powder at 600 times dilution; in the early stage of the disease, spray 50% thiophanate-methyl sulfur suspension at 800 times dilution, or 50% Genfuling wettable powder at 800 times dilution, for control.

IV. Leaf Blight

1. Symptoms

Initially small dark brown spots appear, which later expand into oval or irregular lesions, grayish-white, with wavy, dark brown edges. In severe cases, the leaves dry up and fall off, and many small black dots form on the lesions, which are the pycnidia of the pathogen.

2. Pathogen

Phomopsis cinnamomi S.M.Lin et P.K.Chi, belonging to the Deuteromycetes fungi. The pycnidia are borne on the leaf surface, dot-like, scattered, later breaking through the epidermis and exposed, dark brown, triangular to flattened spherical, unilocular, with papillate ostioles, 150-300 x 100-150 (μm). The conidiophores are slender, branched, colorless; the conidiogenous cells are phialidic, proliferating internally; alpha conidia are oval or cylindrical, with 2 oil droplets, colorless and unicellular, 5-7 x 1.2-2.9 (μm); beta conidia are filiform, colorless, unicellular, curved, 16-22 x 0.7-1.0 (μm).

3. Transmission Routes and Disease Conditions

The pathogen survives in diseased parts as mycelium and pycnidia, and when conditions are suitable the following year it invades the leaves and causes disease.

4. Control Methods

(1) Remove diseased plant debris promptly to reduce the primary infection source.

(2) At the initial onset, spray 40% chlorothalonil suspension at 500 times dilution or 50% chlorothalonil-sulfur suspension (Shuntianxing No. 2) at 500-600 times dilution (Beijing Shunyi Pesticide Factory), 50% thiophanate-methyl sulfur suspension at 800 times dilution, 27% copper hydroxide suspension or 12% copper octanoate emulsifiable concentrate at 600 times dilution, or 20% Longkejun suspension at 500 times dilution.