Key Technical Points for Simple Canopy Film Covering of Early-Maturing Satsuma Mandarin Varieties

Key Technical Points for Simple Canopy Film Covering of Early-Maturing Satsuma Mandarin

Yiling District, Yichang City, Hubei Province is the hometown of early-maturing mandarins in China, with an existing citrus cultivation area of 23,300 hm2 and an annual output of over 700,000 t. Because frost frequently occurs in mid-to-late November every year in the local area, 85% of citrus is concentrated on the market in October and November, creating great sales pressure, and in bumper years prices are often so low that they hurt farmers. In order to avoid frost damage and extend the market supply cycle of early-maturing Satsuma mandarins, in 2010 the Yichang Wide-Skin Mandarin Comprehensive Experimental Station of the National Modern Citrus Industry Technology System carried out research on simple canopy film covering technology for early-maturing Satsuma mandarins in Cangwubang Village, Xiaoxita Subdistrict, Yiling District. Seven years of practice have proved that this technology can effectively reduce abnormal fruit drop and rot of fresh early-maturing Satsuma mandarins, improve the external and internal quality of the fruit, extend the fresh fruit supply period by 30-45 days, and increase the selling price by 0.40-0.60 yuan/kg. Generally, after covering with film for about one and a half months, the net income per 667 sq m can increase by more than 1,000 yuan.

1 Technical Points

Preparations before film covering. Choose polyethylene agricultural film with relatively high light transmittance, generally requiring a thickness of 0.06-0.08 mm and a width of 4-8 m, and prepare cloth strips, nylon ropes or woven straps, wooden stakes, etc.; thin out or cut back the branches protruding at the top and periphery of the canopy so as not to puncture the film, cut off dead branches and diseased and insect-damaged branches on the trees, and together with ground weeds, dead branches, fallen leaves and fallen fruit, bury them deeply or burn them in a centralized manner; within one week before film covering, choose a sunny day and use abamectin 1,500-fold solution + Dacotech M-45 600-800-fold solution + 2,4-D 30 mg/kg, or Luying 200-fold solution + prochloraz 500-1,000-fold solution + 2,4-D 30 mg/kg, etc., to spray the canopy evenly.

Time and method of film covering. The main purpose of film covering is to prevent the fruit from freezing and losing economic value. If the film is covered too early, when the temperature has not yet dropped below 20°C, it is easy to burn the leaves and fruit; if covered too late, the fruit has already been frozen and rotted. The suitable film covering time in Yiling District is before November 5. When covering a single tree, tie the film around with cloth strips, nylon ropes or woven straps and pull it tight, then fix it with wooden stakes; when covering a whole row, tie the two ends of the film on both sides with ropes and pull them tight and fix them with wooden stakes, and pull a rope along the direction perpendicular to the film between two trees to fix it, so as to prevent wind from lifting the film. In both film covering methods, a gap of 20-40 cm should be kept between the edge of the film and the ground.

Management after film covering. Strengthen daily inspection, with special attention to the film covering condition after strong wind, rainfall and snowfall. Strong wind easily lifts or punctures the film; after strong wind, if there is lifting, blowing open, or tearing, repair or fix it in time; rainfall and snowfall easily press down or collapse the covering film; after rain and snow, promptly shake off the water or snow on the film, and repair damaged parts in time. Prevent high temperature. On hot sunny days, pay attention to uncovering the film in time for ventilation to avoid sunscald. Remove the film in time. After all the fruit has been harvested, remove the film from the canopy in time to facilitate tree recovery and reduce the impact on next year's production [Jishan Huayao].

2 Precautions

Orchard selection. Choose hills or sloping land with a relatively high level of management, strong tree vigor, and relatively light disease and insect damage, and with a yield of 3,000-5,000 kg per 667 sq m for implementation; it is not suitable to choose sloping land at wind gaps or flatland mandarin orchards.

Fruit thinning. Large fruit of early-maturing Satsuma mandarins is prone to puffiness when harvest is delayed. Fruit with a transverse diameter greater than 65 mm can be harvested and sold, and at the same time non-commercial fruit such as diseased and insect-damaged fruit, sunscald fruit, and deformed fruit should be thinned out, so that the tree load remains at about 2/3 of the original.

Spraying to protect fruit. After film covering, the temperature and humidity inside the canopy rise, which easily aggravates the occurrence of red mites and some diseases, and may even cause abnormal fruit drop. Therefore, before film covering, it is essential to spray once with a pollution-free agent combining control of red mites, diseases, and fruit retention; 2,4-D must be sprayed to wet the fruit stalk.

Harvest fruit in time. After the canopy is covered with film, although delayed harvest can improve fruit quality, the harvest period is not better the later it is. If harvested too late, the peel is prone to puffiness, affecting fruit quality, which is unfavorable for post-harvest transportation and storage, and also unfavorable for tree recovery [1]. In combination with the sales characteristics of early-maturing Satsuma mandarins, the film covering period in Yiling District is 40-60 days, and it is advisable to finish sales early before the end of December, and no later than early January of the following year.