Watermelon harvesting in greenhouse should start from the end of May. The first batch of melons should be harvested at the end of June. Identification method of raw and cooked melons: Generally, a mature watermelon has grown up, and its skin is beautiful, shiny and oily. The fetal hair on the skin has receded, leaving only a circle of villi on the pedicel, and the navel is deeply concave, which can float on the water when put into the water, while the raw melon sinks into the water; Hold the watermelon in your hand, put it next to your ear and squeeze it gently. Melons make a "Z-" sound, which is ripe melons, mostly sand pulp melons; Percussion: Hold the watermelon in one hand, pat it gently with the other hand, or play it with the index finger and middle finger. Ripe watermelons will make a dull sound when knocked, and immature watermelons will make a crisp sound when knocked. The general rule is that cooked melons are "muffled" and raw melons are "crunchy". Under special circumstances, some melon skins are too thick, which sounds stuffy but not necessarily ripe. Other melons have hard skins and are brittle when knocked, but they are all mature melons. In the above situation, we need "comprehensive appraisal and flexible application".
For skilled people, the fastest identification method is to look at melon hair. This method is usually used for large-scale production and harvest of watermelon.
Precautions in the harvest period, which is also the thinnest time of melon skin, many varieties are prone to crack during this period. For some special varieties, the fruit cracking rate can reach more than 30%, which is a great loss for melon farmers. High temperature and drought caused a large number of fruit cracks in some watermelons during the expansion period. Fruit cracking during fruit expansion is mostly caused by drastic changes in soil moisture. After continuous drought, sudden flood irrigation or continuous rainstorm, a large number of nutrients are input into the fruit, which makes the pulp grow much faster than the peel and form cracked fruit; In addition, common varieties of thin-skinned watermelons, such as Huang Xiaoyu, Hong Xiaoyu, 84-24, etc. , are easy to crack, and the skin thickness is only about 0.5 cm. When the fruit is about to mature, a large number of fruits will crack when it encounters a slight vibration of fruit cracking, continuous rainfall, continuous drought and sudden flooding.
Preventive measures: Appropriate furrow irrigation can determine the degree of water shortage according to the wilting and recovery of leaves, and combine with the local meteorological forecast to ensure that furrow irrigation is carried out for 3-4 days without heavy rain in the near future, and the water content should be uniform. It is best to use drip irrigation.
When melon fruit cracking is serious, in order to prevent fruit cracking caused by sudden rainstorm after continuous drought, a large amount of nutrients can be properly controlled to flow into the fruit. The specific method is to select two small bamboo sticks with the width of 1/3 and the diameter of the stem and vine, and insert them vertically into the melon and vine; Insert the pin vertically into the fruit handle instead of the bamboo stick; The purpose of reducing fruit cracking can be achieved by gently twisting vines or fruit handles with your hands.
Fusarium wilt is one of the main diseases of watermelon in the middle and late stage. Fusarium wilt can occur in the whole growth period of watermelon, but it is the most serious in the fruit-bearing period of stretching vine. Especially in continuous cropping fields, almost 100% of the diseases occurred. The adult plant is diseased, the lower leaves are yellow, the epidermis at the base of the stem is rough, the root neck is often longitudinally cracked, and when it is wet, the diseased part is waterlogged, and white or pink molds often grow, and the vascular bundles are brown. Its prevention and control methods are comprehensive prevention and control: first, rotation, with an interval of more than 5 years; Second, grafting, using blue melon with high resistance to Fusarium wilt as rootstock; Third, when Fusarium wilt is found, the diseased plants are pulled out in time and burned; Fourthly, irrigate the roots with 500 times solution of 50% carbendazim wettable powder or 350 times solution of 30% DT bactericide, or irrigate around the roots with 500- 1000 times solution of benzoate, 70% thiophanate-methyl and dixone, with 200-250 ml per plant and 7- 10 day interval.
Anthracnose: Anthracnose is the most serious disease of watermelon in the middle and late stage. Brown round or semi-circular lesions appear on the edge of leaves. There are black spots or pink sticky substances, the stems are dark brown, and they collapse and die. The diseased spots on stems, vines and petioles are round or spindle-shaped, yellow to brown, slightly sunken, which can lead to plant death in severe cases. The damaged part of the fruit is waterlogged in the early stage, light green, round or oval after the lesion is enlarged, brown and concave, and produces pink mucus when wet. The prevention and control methods are: spraying 800 times of 50% thiophanate-methyl wettable powder and 800 times of 75% chlorothalonil wettable powder or 800 times of 50% carbendazim wettable powder in protected areas and open fields at the early stage of the disease. In addition, 36% thiophanate-methyl was suspended 500 times, 80% thiram anthrax wettable powder 800 times, 62.25% fresh or 80% Sheng Da wettable powder 700 times, 10% water dispersible granule 1500 times, 2% antifungal agent (agricultural antibiotic 65438+).
Fusarium wilt: Fusarium wilt mainly harms the stems, leaves and fruits of watermelon. The diseased spots on the leaves are round, waterlogged and dark green; Soft rot occurs when the air humidity is high, and it is blue and easy to break when it is dry. The stems and petioles are diseased, and the diseased spots are spindle-shaped, shriveled, dark green and waterlogged, and the stems and leaves above the affected areas are wilting and drooping. The fruit produces dark green waterlogging pits, and there are sparse white molds on the affected parts, which have a foul smell. The control methods are as follows: 600 times solution of 75% chlorothalonil wettable powder or 800 times solution of 25% Ruimycin wettable powder, or 500 times solution of 50% Dijunling wettable powder, 500 times solution of 64% antivirus alum and 500 times solution of 60% DTM wettable powder, every 5-7 days 1 time, for 3 times in a row. Pay attention to the difference between anthrax and anthrax. These two diseases use different drugs.