Symptom Identification and Control Methods of Cucumber Anthracnose

Cucumber is a vegetable that many people like to eat; it tastes delicious and is very refreshing to eat, so it is grown in quite a lot of places. So in the actual growing process, what symptoms does cucumber show when it gets anthracnose? What are the control methods?

1. What symptoms does cucumber show when it gets anthracnose?

Cucumber can be infected at both the seedling stage and the mature plant stage. The disease mainly infects leaves, fruits and stems. The symptoms are easily confused with phytophthora blight and scab, so attention must be paid to distinguishing them when diagnosing.

The seeds can be infected as soon as they emerge. The edges of the cotyledons show light brown semicircular spots, or round lesions appear in the middle of the cotyledons. When the seedlings are slightly larger and the true leaves are infected, yellow-brown round lesions appear on the lower leaves; the lesions merge into patches and the leaves dry up. Sometimes the base of the stem is damaged; the affected part constricts and discolors, and the seedlings damping off.

One type of lesion is a large light brown spot, which is the typical symptom of anthracnose. When leaves are damaged, water-soaked light yellow small spots appear at first, sparsely distributed, and the boundary between the diseased and healthy parts of the lesion is not obvious.

Afterward the lesions gradually expand, forming light yellow to light brown lesions 0.3-0.5 cm in diameter, round or nearly round. In many cases these densely distributed small lesions stop expanding and instead gradually merge into patches.

Under the relatively high humidity of a greenhouse, the sparsely distributed small round spots on the leaf surface gradually expand, forming light brown round spots close to 1 cm in diameter; the lesion color is uniform and the outer edge of the lesion is slightly darker. This is the most common and most typical leaf symptom of anthracnose.

2. What are the control methods for cucumber anthracnose?

1. Choose disease-resistant varieties

Such as Jinyan No. 4, Zaoqing No. 2, Zhongnong 1101, and Xiafeng No. 1. In addition, Zhongnong No. 5 and Xiaqing No. 2 are relatively tolerant to the disease. Use disease-free seeds, make sure to save seeds from disease-free cucumbers, and for seeds used in production soak them in warm water at 50-51°C for 20 minutes, or soak them in a 100-fold glacial acetic acid solution for 30 minutes, then rinse them clean with clear water before sprouting.

2. Cultivation measures

Carry out crop rotation with non-cucurbit crops for more than 3 years, disinfect the seedbed, cultivate disease-free strong seedlings, use high-ridge plastic film cultivation, and increase the application of phosphorus and potassium fertilizers to improve the disease resistance of the plants. Carry out field farming operations after the dew has dried to reduce the artificial spread of the pathogen; remove diseased leaves and old leaves promptly in the early stage of the disease, clean up the field after harvest, and take the diseased residues out of the greenhouse for proper disposal. Strengthen the temperature and humidity management of the greenhouse, ventilate and dehumidify timely and appropriately, and reduce dew formation on the leaf surface.

3. Seed treatment

Before sowing, the seeds should be carefully cleaned and can be disinfected by soaking them in constant-temperature water at 55°C for 15 min, or soaking them in a 500-fold solution of 50% mass fraction carbendazim wettable powder for 60 min, or soaking them in a 500-fold solution of 50% mass fraction mancozeb for 10 h, then rinsing with clear water before sowing.

4. Chemical control

In the early stage of the disease, first remove the diseased leaves, then spray. Commonly used chemicals include a 1500-fold solution of 15% triadimefon, a 500-fold solution of 50% carbendazim, a 500-fold solution of 65% zineb, a 400-fold solution of 70% mancozeb, an 800-1000-fold solution of 70% thiophanate-methyl, a 600-fold solution of 75% chlorothalonil, and a 500-600-fold solution of 80% anthracnose fumei, etc. Spray once every 5-7 days, for 4-5 consecutive sprays, and alternate the pesticides to avoid the pathogen developing resistance.