What are the control methods for bitter melon white spot disease

Bitter melon, also known as balsam pear, is a plant of the Cucurbitaceae family. It is an annual climbing herb, edible, and of high value. The stems, branches, petioles and pedicels are covered with soft hairs, with axillary tendrils. The leaves reach 3 to 12 cm in diameter, with 5 to 7 palmate deep lobes, and the lobes are elliptical with serrated outer edges. It flowers at the turn of spring and summer, monoecious, yellow. The fruit is oblong-elliptical, with many irregular warty protrusions on the surface. The seeds are hidden inside the fleshy fruit, wrapped in a red aril when mature. Bitter melon is a vegetable that people love. Its place of origin is unclear, but it is generally believed to be native to tropical regions. It is widely cultivated in South Asia, Southeast Asia, China, and the Caribbean islands.

Requirements of bitter melon for the growing environment

Temperature: Temperature control. Bitter melon likes warmth, is relatively tolerant of heat, and not tolerant of cold. Seed germination is suitable at 30-35°C. When the temperature is below 20°C, germination is slow, and below 13°C germination is difficult. At around 25°C, seedlings with 4-5 true leaves can be grown in about 15 days, while at around 15°C it takes 20-30 days. At 10-15°C, bitter melon plants grow slowly, and below 10°C growth is poor. When the temperature is below 5°C, the plants are significantly damaged. However, with slightly lower temperatures and short-day conditions, the node position at which the first female flower appears is earlier. The flowering and fruiting period is suitable above 20°C, with around 25°C being optimal. Within the range of 15-30°C, the higher the temperature, the more favorable it is for the growth and development of bitter melon——fruiting early, with high yield and good quality. Above 30°C and below 15°C are both unfavorable for the growth and fruiting of bitter melon.

Light: Bitter melon is a short-day plant and likes sunlight but is not tolerant of shade. However, after long-term cultivation and selection, its requirements for photoperiod are no longer very strict; but if light is insufficient at the seedling stage, its ability to resist low temperatures will be reduced. In northern Hainan, when winter-spring bitter melon encounters low-temperature and rainy weather, the seedlings grow weak, have poor stress resistance, and are often prone to cold damage, which is exactly this principle. The flowering and fruiting period requires relatively strong light. Sufficient light is conducive to photosynthesis and improves the fruit-setting rate; otherwise, it easily leads to flower and fruit drop.

Water: Suitable soil. Bitter melon likes moisture but is not tolerant of waterlogging. During the growing period, it needs 85% relative air humidity and soil relative humidity. In dry weather with insufficient water, plant growth is hindered and fruit quality declines. However, it should not be waterlogged either. Waterlogging easily causes root rot and yellowing and wilting of leaves, which in mild cases affects fruiting, and in severe cases causes the plants to become diseased and die.

Nutrients: Bitter melon has a relatively wide adaptability to soil, and can grow in soils ranging from sandy loam to light clay. Generally, it grows well and yields high on fertile, loose loam with strong water and fertilizer retention. Bitter melon has relatively high fertilizer requirements. If organic fertilizer is sufficient, the plants grow robustly, with luxuriant stems and leaves, more flowers and fruits, and the melons are also plump and of good quality. Especially in the late growth stage, if fertilizer and water are insufficient, the plants become weak, with fewer flowers and fruits, smaller fruits, stronger bitterness, and reduced quality. Bitter melon needs relatively more nitrogen fertilizer, but nitrogen fertilizer should not be applied one-sidedly; otherwise, stress resistance decreases, making the plants susceptible to infection by pathogens and damage from cold. In fertile, loose medium loam, applying additional phosphorus and potassium fertilizer can make the plants grow robustly, and the melon production can remain strong for a long time.

How to control bitter melon white spot disease?

What is bitter melon white spot disease? What symptoms does it have?

Bitter melon white spot disease is a fungal disease caused by a fungus called bitter melon Cercospora. It mainly damages the leaves. In the early stage, small round spots that fade from green to yellow appear, gradually expanding into nearly round or irregular grayish-brown to brown lesions about 1-4 mm in diameter, with relatively obvious edges. The center of the lesion is grayish-white, polygonal or irregular, with sparse light black mold-like growth on it, which is easy to see when humid. It often easily causes the lesions to perforate.

The disease overwinters as mycelium or conidia on diseased residues, which become the source of infection the following year. It spreads to bitter melon leaves through airflow or rainwater and infects them, causing disease. The conidia produced on the lesions continue to spread and cause infection. In melon fields with high temperature and rainy seasons, lack of organic fertilizer, excessive one-sided application of chemical fertilizer, and compacted soil, the disease is more severe. Control methods for bitter melon white spot disease:

First, do a good job of field sanitation, remove and destroy diseased and residual plants, and reduce the accumulation of disease sources in the field;

Second, apply sufficient organic fertilizer, improve the soil, enhance fertility, ensure that bitter melon has deep roots and strong plants, and improve disease resistance;

Third, topdress in time when bitter melon sets its first round of fruit, to ensure that vegetative growth and reproductive growth obtain sufficient nutrients at the same time. Apply foliar fertilizers such as Lufenwei, Baishili or Lufengsu to supplement necessary trace elements, and properly thin side buds to ensure that new shoots and leaves are thick and green;

Fourth, spray fungicides regularly to prevent disease. You can choose Aijuntuo or Anmeituo (70% wettable powder) 800-1000 times solution, Xin'erpu or Fashengling (65% wettable powder) 400-500 times, Baikening or chlorothalonil (40% suspension concentrate) 600-700 times. Generally spray once every 7-10 days, for 2-3 consecutive times.