What should be noted before and after bagging apples?
Bagging fruit can make the fruit surface fine and smooth, with bright and beautiful color, prevent pests and diseases, reduce pollution from pesticides and dust, produce pollution-free high-quality premium fruit, and effectively enhance the commercial value of the fruit. However, some fruit growers' bagging techniques are not standardized, measures are not fully implemented, and problems have emerged such as poor quality of bagged apples and a low rate of premium fruit, even causing the undesirable outcome of high input and low returns. Practice has shown that bagging apples to produce premium fruit should also pay attention to the following technical points:
1. Bagging requires five selections
Strict selection must be carried out for the trees and fruit to be bagged. First, select excellent varieties with high economic value. Second, select orchards with better management. Third, select plants that are robust in growth, well structured, with an open angle (90-120), and good ventilation and light penetration. Fourth, select trees with proper flower and fruit thinning and a reasonable load (keep fruit spacing at 20-25 cm, leaving about 10,000 fruit per mu). Fifth, select well-developed fruit with a proper shape, and bag obliquely growing and pendulous fruit. These are the basic conditions for ensuring premium fruit.
2. Bagging time should be appropriate
Bagging time should not be too early or too late. Too early will affect the development of young fruit and cause fruit drop; too late makes it difficult for the fruit surface to lose its green color, the peel becomes rough, and the appearance quality is poor. The suitable time for bagging is 35-40 days after petal fall (early to mid-June), and bagging should be completed within a short period. During the day, it is best from 9 a.m. to 6 p.m.; do not bag when the morning dew has not dried and on cloudy or rainy days.
3. Pesticides used before bagging should be carefully selected
From petal fall to before bagging is a period of vigorous division of fruit flesh cells, and the fruit surface is young and tender and extremely sensitive to pesticides. Improper use of pesticides or foliar fertilizer during this period will cause the fruit's lenticels to crack and form larger suberized lenticels, making the fruit surface rough and even producing rust spots. In order to ensure that the surface of bagged fruit is clean, smooth, and brightly colored, and to improve the rate of premium fruit, three points should be achieved when using pesticides to control pests and diseases or spraying foliar fertilizer during the young fruit stage: First, the number of sprayings should not be too many and the concentration should not be too high, so as to minimize the irritating effect of pesticides on the fruit surface. Second, avoid using insecticides and fungicides that easily cause fruit russeting (such as pesticides containing copper ions and organophosphorus compounds). Third, when spraying foliar fertilizer, try not to use chemical fertilizers such as monopotassium phosphate and urea; nutrient liquid fertilizers may be applied (such as organic humic acid fertilizer or amino acid compound micro-fertilizer, etc.).
4. Calcium supplementation before bagging should be strengthened
Apple is a fruit tree with a relatively high calcium requirement, and calcium-deficient fruit is prone to bitter pit, blister spot, speckle disease, fruit cracking, and other disorders. The critical period for apple's calcium demand is 30-40 days after flowering. In addition, after bagging, the transpiration of the fruit is very small, and the calcium transferred into the fruit by the pulling force of the transpiration stream is reduced. Therefore, from 1 week after petal fall to before bagging, foliar calcium supplementation should be sprayed 2-3 times, generally applying amino acid calcium, humic acid calcium, calcium chloride, etc., to avoid physiological fruit disorders caused by calcium deficiency.
5. The quality of fruit bags should be guaranteed
The quality of fruit bags is an important factor determining the success of bagging fruit. There are many types of fruit bags currently used, including double-layer paper bags, single-layer paper bags, plastic microfilm bags, etc. However, qualified double-layer three-color paper bags have the best effect, such as Taiwan Jiatian, Shandong Kaixiang, Aimin, Hebei Shunda, Shaanxi Dadi, Jinggong, etc. Products that have no manufacturer, no trademark, no inspection certificate, are roughly made, have poor paper quality, have not been treated for antibacterial protection, have poor water resistance, poor air permeability, and insufficiently uniform wax coating on the inner bag, and other substandard products, must not be used. Plastic microfilm bags are low in price and can reduce the investment in bagging, but their effect in improving fruit surface quality is inferior to that of double-layer paper bags, and they are prone to sunburn. Especially in dryland orchards lacking irrigation conditions, when encountering high temperature and drought weather, the sunburn phenomenon becomes even more serious, and attention should be paid to this.
6. Bagging operations should be standardized
Spray a fungicide and insecticide once 1-2 days before bagging, and bag after the liquid dries. When bagging, first open the fruit bag with your hands so that the bag becomes puffed up. Align the longitudinal opening of the fruit bag with the fruit stalk, seat the opening on the fruit stalk, then fold the bag mouth horizontally left and right, and then bend the pre-embedded binding wire at the bag mouth into a V shape to clamp and secure the bag mouth. During operation, do not bag leaves and secondary shoots into the bag; the binding wire should clamp the folded layers of the paper bag and must not be twisted onto the fruit stalk, so as to avoid damaging the fruit stalk and causing fruit drop; the paper bag should be puffed up, with the young fruit suspended inside the bag, to prevent the fruit surface from pressing against the inner wall of the paper bag and causing sunburn on the apple fruit.
7. Regular inspections should be carried out after bagging
After bagging is completed and after windy and rainy weather, a general inspection should be carried out. Check whether the bag mouth is tightly tied, whether the puffed paper bag has deformed, and whether there is any phenomenon of young fruit pressing against the bag wall. Every 10-15 days, open bags for spot checks to check whether there are pests inside the bags (pests and eggs bagged in during bagging, or pests drilling into the bags when the bag mouth is not tightly tied) and whether diseases occur, whether sunburn appears, etc. If problems are found, necessary measures can be taken according to the degree of damage.