How to prevent and control carnation leaf spot? A detailed guide to practical methods

Carnation leaf spot, also known as branch rot and stem rot, is a worldwide disease that harms carnations most severely, and also harms Dianthus barbatus (sweet William), Dianthus chinensis, Dianthus plumarius, Saponaria officinalis and others. In Shanghai, Hangzhou, Guangzhou, Kunming and southern Jiangsu Province, 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 spots are round, oval or irregular, 4-5 mm in diameter, reddish-brown and sunken, gradually turning grayish-white. In severe cases, black mold (conidia) appears on the diseased parts, and the leaves wither, turn yellow and droop, but do not fall off. When the spots grow on the stem and girdle it, branch blight occurs. When flower buds are infected, round spots form on the buds along with black mold, and spots form on the pedicels, causing the flower buds to wither and die.

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

(3) Occurrence pattern The pathogen overwinters in diseased plant debris as mycelium and conidia. The disease begins in June of the following year, is most severe in August to September, and the spores are spread by wind, rain and irrigation water. They invade the plant through wounds, stomata or directly. In the plum rain season and in years with much rain, the disease tends to become epidemic. Dense planting also makes the disease more likely, and planting in greenhouses can lead to disease year-round; aging leaves are also susceptible. According to observations at the Shanghai Botanical Garden, the Beijing fine-leaf variety is more disease-tolerant than local broad-leaf varieties. Varieties with soft foliage, 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 cutting flowers spray or apply 1% Bordeaux mixture, or 50% captan 500 times dilution, or mancozeb 500 times dilution, or 75% chlorothalonil 500 times dilution to the remaining stubble; any one of these may be chosen, sprayed or applied once every 1-2 weeks. Maintain light penetration.

3. Avoid spraying water onto the plants.

4. Spraying 1:1:100 Bordeaux mixture 4-5 times has an obvious effect, and spraying 50% amobam 1000 times dilution also has a certain effect.

5. Rotation with rice gives good results.

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

Symptoms of carnation leaf spot, control methods for carnation leaf spot

The carnation is the mother's flower of our country. During the carnation's growth cycle, carnations are prone to leaf spot. Below, the editor of China Agro-chemical Investment Network shares with everyone the symptoms of carnation leaf spot and the control methods for carnation leaf spot.

The carnation is an excellent cut flower variety. Dwarf varieties can also be used for potted ornamental display. The flowers can also be used to extract essence. It is widely cultivated for ornamental purposes in our country. Below, the editor introduces the control techniques for carnation leaf spot.

Symptoms of carnation leaf spot

It mostly occurs on leaves and stems, and sometimes also on buds and flowers. On leaves, the disease mostly starts from the lower part, first producing small light green water-soaked round spots, which gradually turn purple. As the spots expand, the center of the spot dies. The edges are brown, and the spots are round, oval or irregular, about 4-5 mm in diameter, with the dead central part grayish-white to gray; afterward black mold appears on the spots. When the plant is severely affected, the leaves wither and droop but do not fall off. On the branches, after the spots encircle the stem or a branch, the upper branches, leaves and flower buds shrink and die.

Occurrence pattern of carnation leaf spot:

This disease can occur from early April to early winter, and under greenhouse cultivation it can occur throughout the year, with the disease being most severe in the hot summer rainy season. If planting is too dense, it spreads very quickly. However, in the north this disease occurs relatively less.

Control methods for carnation leaf spot

1. When planting, select disease-free branches from healthy plants to prevent initial infection by the pathogen; disease-resistant fine-leaf varieties can also be introduced for planting.

2. After disbudding and cutting flowers, you may choose 800-**** times dilution of Bijunsha, 2000-3000 times dilution of Penkejun, or 75% chlorothalonil 500 times dilution for spraying, all with very good results. If the disease occurs during the growing period, promptly remove diseased leaves or pull out diseased plants, and spray the above-mentioned agents to prevent the disease from spreading.

Control methods for carnation leaf spot