Symptoms and Control Methods of Carnation Wilt

[Symptoms]

The external symptoms of this disease are very similar to those of Fusarium wilt. The leaves of affected plants turn grayish-green, then yellow, and dieback of the shoot tips occurs. The stems split, causing the plants to wilt and die. When the central column (stele) is examined, yellow to light brown stripes can be seen. While the aboveground parts are affected, the roots also disintegrate accordingly. The onset of the disease can be divided into two types: the acute type develops very rapidly, and is especially pronounced when young plants in hotbeds are affected; when the damage is mild, the leaves appear twisted.

[Pathogen]

Pseudomonas caryophylli (Burkholder) Starr et Burkholder, belonging to the bacterial family Pseudomonadaceae. Gram stain reaction negative, widely distributed in soil. The bacterial cells are rod-shaped, approximately 0.8 x 2.0 (micrometers), motile by polar flagella.

Most strains produce a yellow-green, non-fluorescent, diffusible pigment, which is more pronounced in iron-deficient media. Some strains have lipolytic activity. Strictly aerobic (except in nitrate media). The optimum growth temperature is 30-33 degrees C, and some can even grow at 46 degrees C.

[Control Methods]

When diseased plants are found, pull them out and burn them at any time; do not use them for compost.

Establish disease-free seed production bases. Do not plant in soil contaminated with the pathogen. Soak cuttings in a 1000-fold dilution of potassium permanganate or a 1000-fold dilution of streptomycin before rooting them.

In the early stages of the disease, spray with 77% copper hydroxide wettable powder at 400-500-fold dilution, or 14% copper ammonia complex aqueous solution at 300-fold dilution, 50% copper bis(dodecylbenzenesulfonate) wettable powder at 500-fold dilution, 1:1:200 Bordeaux mixture, etc., at intervals of about 10 days, for 1 or 2 applications.