What are the control methods for stem rot in carnations?

Stem rot is a devastating disease of carnations. The main affected parts are the lower branches and leaves. The lesions are round, oval and irregular in shape, red-brown, turning dark brown in severe cases and grayish white to gray in the later stages. The diseased leaves do not fall off after drying out. When a lesion on a branch encircles the stem, the upper shoots and flower buds all die.

The pathogen of stem rot overwinters on stems and leaves, and the disease begins in June of the following year. The disease is most severe in midsummer and during the rainy season. If planting is too dense, it spreads very quickly. The incidence of the disease in carnations grown in the north is very low. In southern regions where the disease is severe, disease-resistant narrow-leaf varieties should be introduced from the north every year. When cultivating, the spacing between plants and rows should be increased, and ropes should be strung between the rows. The flower stems should be tied one by one to the ropes and hung up to prevent them from trailing on the ground.

Before the disease occurs and in the early stages, Bordeaux mixture at double strength can be sprayed, once every 7 days, for a total of 2 to 3 sprays. After the disease occurs, 50% zineb 1000x solution should be sprayed immediately. This can prevent the disease from expanding and spreading, but it cannot eradicate it.

How to control carnation diseases

Common diseases of carnations include leaf spot, rust, gray mold, bud rot and root rot. Today the editor will share with you the control methods for carnation diseases.

Zineb can be used to control calyx rot, and 5 oxycarboxin to control rust. To control other diseases, use zineb, carbendazim or captan for soil treatment before planting. When red spider mites or aphids cause damage, generally use 40% dimethoate emulsion 1000x solution to kill them.

Carnation leaf spot

Carnations are extremely susceptible to leaf spot, which affects their growth and development and reduces the yield and quality of cut flowers. The leaf spot pathogen of carnations overwinters on diseased plant residues as mycelium and conidia, and can survive in the soil for about one year. The lesions are elongated and gray-brown. In severe cases, the lesions girdle the stem, causing the upper branches and leaves to die. When it infects flowers, it often causes damage on flower stalks and bracts. When there are many lesions on the bracts, the flowers cannot open or become deformed.

Control measures:

1. Select healthy, disease-free cuttings and remove diseased plant residues. Keep the plant surface as dry as possible. Carry out crop rotation for more than two years in a place with good ventilation, light and drainage. Keep the greenhouse well ventilated, and ventilate before dusk.

2. Leaf spot can occur year-round, so a preventive fungicide must be sprayed once a week, such as mancozeb, zineb, iprodione, chlorothalonil, etc. In particular, spray promptly after harvesting cut flowers. Any of 75% chlorothalonil, 50% captan 500x solution or 1% Bordeaux mixture can be used.

Virus: cannot be treated. Please use seed-sown seedlings or virus-free treated seedlings.

Carnation gray mold

Carnations are quite seriously damaged by gray mold. After gray mold-like material covers the flower buds, petals, stems and leaves, brown water-soaked lesions appear, causing petals to rot, flower buds to drop, and stems and leaves to die. Infected flower buds cannot open, and diseased flowers lose their bright color. The disease is severe when the temperature is high and humidity is high, spreading rapidly and causing rampant damage. It must be controlled to protect the stems, leaves, flower buds and petals, so as to promote flowering, extend the flowering period and increase ornamental value.

Specific control methods: Spray the leaves once a month with 1000x potassium permanganate aqueous solution, or 1000x sodium bicarbonate (baking soda) aqueous solution, or 25-30x clarified liquid leached from dry, clean plant ash, evenly wetting all leaves, flower buds and petals, until water droplets begin to drip down. This can effectively control the occurrence and damage of carnation gray mold and protect the stems, leaves, flower buds and petals. If there is a lot of rain, high temperature and high humidity, and gray mold-like material appears on the stems, leaves, flower buds and petals, then continuously spray the leaves 2-3 times with a mixture of 1000x procymidone, 1500x Shennongsu chelated compound fertilizer and 300x monopotassium phosphate, or a mixed solution of 1000x procymidone, 1000x Zhuangfengyou and 500x high-efficiency biological phosphorus-potassium fertilizer for control, spraying once every 7-10 days, to kill the pathogen and quickly restore normal growth to the affected parts, strengthen the stems, leaves, flower buds and petals, and promote flowering.

The above are the control methods for carnation diseases.

Control methods for carnation leaf spot

Carnation leaf spot, also called branch rot and stem rot. It is the most serious worldwide disease harming carnations, and also harms Dianthus barbatus (sweet William), Dianthus chinensis, Dianthus plumarius and Saponaria officinalis (soapwort). Shanghai, Hangzhou, Guangzhou, Kunming and southern Jiangsu, areas where carnations are propagated, are also affected by this disease.

(1) Symptoms The pathogen infects leaves, stems and flower buds. The disease usually starts from the lower leaves. The lesions are round, oval and irregular, 4-5 mm in diameter, red-brown and sunken, gradually turning grayish white. In severe cases, black mold (conidia) is produced on the diseased parts, and the leaves turn yellow and droop, but do not fall off. When lesions grow on the stem and girdle it, branch dieback occurs. When flower buds are infected, round spots appear on the bracts along with black mold, and lesions appear on the stems, causing the flower buds to die.

(2) Pathogen It is a fungus of the genus Alternaria, subphylum Deuteromycotina. The conidia have transverse and longitudinal septa. The optimum growth temperature is 26°C.

(3) Occurrence pattern The pathogen overwinters in diseased plant residues as mycelium and conidia. The disease begins in June of the following year, and is most severe from August to September. Spores are spread by wind, rain and irrigation water. They invade the plant through wounds, stomata or directly. In moldy rainy seasons and years with a lot of rain, the disease tends to become epidemic. Dense planting also makes the disease more likely. Cultivation in greenhouses can lead to disease year-round, and aging leaves are also susceptible. According to observations at the Shanghai Botanical Garden, Beijing narrow-leaf varieties are more disease-tolerant than local broad-leaf varieties. Varieties with soft grass bodies, wide leaves and large flowers are susceptible.

(4) Control methods

1. Select disease-tolerant and disease-resistant varieties.

2. Strengthen management, pay attention to disbudding and pruning, remove diseased leaves, and after picking flowers spray or apply to the remaining stubble 1% Bordeaux mixture, or 50% captan 500x solution, or mancozeb 500x solution, or 75% chlorothalonil 500x solution. Choose any one. Spray or apply once every 1-2 weeks. Maintain light penetration.

3. Avoid spraying water on the plants.

4. Spray 1:1:100 Bordeaux mixture 4-5 times, with obvious effect. Spraying 50% amobam 1000x solution also has a certain effect.

5. Rotate with rice, with good results.

6. Apply more phosphorus and potassium fertilizers to enhance disease resistance.