How to Remove Kiwifruit Fruit Rust? A Detailed Guide to Practical Methods
1. Site selection: Choose a light hilly area that is sheltered from the wind and faces the sun, with abundant water sources, convenient drainage and irrigation, deep soil layers, and rich humus. Prepare the land with large planting holes 1 m square, applying 50 kg of farmyard manure and 2 kg of decomposed cake fertilizer per hole. 2. Planting technique: Use one-year-old grafted strong seedlings, with a plant-to-row spacing of 3 m...
In a broad sense, fruit rust refers to a physiological disorder in which the fruit surface develops rust-like contaminants during growth due to friction and irritation from chemical pollution, as well as a rust-colored contaminant formed on the fruit surface when rain washes rust, diseased remnants from old or diseased leaves, and dust from the tree onto the fruit; in a narrow sense, fruit rust refers only to a physiological disorder in which the fruit surface develops rust-like contaminants during growth due to friction and irritation from chemical pollution. Although fruit rust does not affect the eating quality of the fruit, it seriously affects the appearance quality of the fruit, thereby reducing its commercial value. With the continuous improvement of people's living standards, the issue of fruit rust, which consumers previously did not pay attention to, has attracted increasing attention. Attention has gradually shifted from fruit rust on smooth-skinned fruits such as apples, pears, and citrus to the appearance quality of fuzzy fruits such as kiwifruit and peaches. At present, the main methods for preventing and controlling fruit rust are bagging, rational pruning, increased fertilizer application, replacing the iron wires on the trellis, and washing the fruit. 1. Bagging. Bagging means putting a relatively sealed bag over the fruit in the early stage of fruit growth to isolate the fruit from the external environment. Bagging has the following effects: A. Promoting fruit coloration: Bagging peach fruit can promote coloration, but because there are many peach varieties with inconsistent ripening periods, the ease of fruit coloration varies greatly among varieties. Therefore, to promote coloration, different types of fruit bags are selected for different varieties. For varieties that color easily, white or yellow single-layer bags can be used; for varieties that are difficult to color, composite single-layer bags that are white outside and black inside should be used, or double-layer bags with an outer layer of white-outside black-inside composite paper and an inner layer of white semi-transparent material. B. Keeping the fruit surface clean: The physical protection of bagging can prevent dust, pesticides, and pest secretions from directly contaminating the fruit and causing fruit rust, ensuring a clean fruit surface. C. Controlling pests and diseases: It has a preventive and control effect on fruit-boring pests and diseases. In China, the main bagging-related pest of peaches is the mulberry whitefly; in areas where mulberry whitefly is found, insect-proof bags should be used. D. Preventing fruit cracking: For varieties prone to cracking, bagging has a preventive effect on fruit cracking. Fruit bagging is one of the most effective measures to prevent fruit rust. If high-quality fruit bags are selected and correct bagging techniques are adopted, the rate of rust-free fruit can reach more than 90%, significantly increasing the commercial value of the fruit.
2. Rational pruning and increased fertilizer application. Rational pruning and increased fertilizer application mainly play a preventive role in removing fruit rust, chiefly preventing fruit rust caused by physiological disorders. This type of fruit rust is formed when the epidermal cell layer and its covering rupture, exposing suberized cells. The purpose of rational pruning is to control the load, and together with strict fruit thinning, reduce the nutrient consumption of the tree and promote fruit growth; open up the light path around the fruit, and at the same time clear away diseased and old leaves around the fruit, so that the fruit has a suitable growing environment during development and can heal promptly after minor wounds, avoiding the later formation of fruit rust and other physiological disorders. The purpose of increasing fertilizer application is also to strengthen tree nutrition, rejuvenate tree vigor, promote vigorous fruit growth, and enhance its ability to resist adverse environments and wounds.
3. Selecting rust-resistant varieties and rational pesticide spraying. Selecting rust-resistant varieties is the basic step in preventing fruit rust. Timely application of pesticides is the key step in preventing fruit rust; applying pesticides during the sensitive period of fruit growth will cause large numbers of rust spots to form on the fruit. During the young fruit stage, copper-containing fungicides such as Bordeaux mixture or organophosphorus insecticides must not be sprayed: generally, pesticides are applied before the wheat harvest. Fungicides such as thiophanate-methyl, mancozeb, iprodione, and polyoxin can be selected for disease prevention, and pyrethroid or carbamate pesticides can be used for pest control, but rust-inducing pesticides such as omethoate and isocarbophos must not be used. If low-temperature and rainy weather or foggy and windy weather occurs, spraying 200-fold high-lipid film on the fruit can not only prevent other diseases but also reduce the occurrence of fruit rust. When spraying, a sprayer with an appropriate nozzle aperture and pressure should be selected so that the droplets are fine and the spray is uniform, and care should be taken that the nozzle is not too close to the fruit, so as to avoid mechanical damage to the fruit.
4. Replacing the iron wires on the trellis. For trellised fruit trees such as kiwifruit and grapes, fruit rust is to a large extent a contaminant formed when rain washes dust, diseased remnants, and iron wire oxides from the trellis onto the fruit surface. This is especially true in Shaanxi, where about one month before kiwifruit harvest is the season with the most rain, causing large amounts of contaminants to form during fruit growth, and among these contaminants, iron rust is the most common. Therefore, combined with winter pruning, replacing rusted iron wires with galvanized wires will reduce the occurrence of fruit rust.
5. Fruit washing. Fruit washing is a very important method for removing fruit rust. Generally, non-toxic, non-polluting salts, acids, and organic solvents are used to soak the fruit, washing away dust, fruit rust, and fruit scars on the fruit surface to achieve a smooth, clean fruit surface, remove contamination, and increase commercial value. At present, domestic fruit washing mainly has two purposes: A. Improving the smoothness of the fruit surface and reducing surface contamination. By washing the fruit, surface contamination caused during fruit growth by early minor wounds, diseased remnants, dust, and the like is washed away, thereby improving surface smoothness to meet market demand, increase the market competitiveness of the fruit, and improve economic benefits; B. Cleaning pesticide residues on the fruit skin. At present, for smooth, fuzz-free fruits such as apples, pears, and citrus, solvents with relatively low solubility or low-concentration, highly soluble agents are mainly used for cleaning; for fuzzy fruits such as kiwifruit and peaches, the above solutions or original concentrations have relatively poor cleaning effects. Experimental research by Northwest A&F University has shown that soaking rusted kiwifruit in a 2% oxalic acid solution for 15 min gives the best effect in cleaning fruit rust, and this cleaning agent is non-toxic and non-irritating to the human body and non-polluting to the environment, with broad application prospects.