8 common appearance problems of bagged Emerald pear and their solutions
Emerald is an excellent new pear variety bred by the Zhengzhou Fruit Research Institute, developed by crossing New Century and Zaosu. Since 2000, after 6 years of bagged cultivation through top-grafting to change the canopy in our city, we have found that this variety has a regular fruit shape, a smooth and glossy fruit surface, creamy white flesh, a crisp and tender texture with abundant juice, and few stone cells, making it an early-maturing pear variety of excellent quality. However, in production we have found that bagged pears often show abnormal phenomena such as black wrinkling, fruit russeting, tiger-skin markings, floral green coloration on the fruit surface, black spots, cracking, and deformities that affect the external quality of the fruit. For this reason we conducted an investigation and analysis and proposed solutions.
1. Problems that occur
Black fissuring of the fruit surface: small longitudinal cracks occur on the fruit surface, and the cracks turn black, making the fruit surface rough and appear black-fissured. The cause is that the fruit surface is pressed tightly against the paper bag, and pesticide solution or rainwater often soaks there; after exposure to sunlight on clear days, the temperature and humidity change suddenly, stimulating the fruit surface and causing protective reactions or even damage to the epidermal cells.
Large fruit dots and rough fruit surface: enlarged fruit dots and a rough, lusterless appearance occur over the entire fruit surface or part of it. Bagging too late and pesticide damage during the young fruit stage before bagging are the main causes of large fruit dots and a rough fruit surface.
Floral green coloration on the fruit surface: patchy, strip-like, or vaguely edged light green traces on the fruit surface. The main causes are poor-quality fruit bags, small specifications, and loose tying of the bag opening during bagging, leaving places where light can pass through.
Fruit russeting generally occurs more often on the lower part of the fruit. Causes: (1) too many pesticide sprays before bagging and too many mixed varieties, causing stimulation of the fruit; (2) bagging when there is dew on the fruit surface or before the pesticide solution has dried after spraying, causing water to remain in the calyx depression for a long time; (3) an orchard that is too dense, with fruit in the middle and lower parts of the tree and in the inner canopy affected by a high-temperature, high-humidity microclimate, forming water russeting.
Tiger-skin markings: irregular brown or light brown spots appearing on the fruit surface. Caused by friction from branches and leaves and artificial mechanical damage to young fruit before bagging.
Black spots on the fruit surface: black or dark brown, sunken or raised black dots or black spots appearing on the fruit surface. Mainly caused by pesticide damage and damage from diseases and pests. Diseases and pests include pear scab, black spot disease, black rot, pear psylla, and yellow mealybug.
Fruit cracking mainly occurs during the fruit expansion period, generally beginning in mid-to-late June and continuing until fruit ripening. The main causes of fruit cracking are drought, heavy rain, or watering during the fruit expansion period, as well as excessively vigorous trees with few fruits and imbalanced nutrition.
Deformed fruit: deformed fruit includes crooked fruit, ridged pear, and lumpy pear. Poor pollination and fertilization, boron deficiency, and damage from diseases and pests are the main causes of deformed fruit. Diseases and pests include pear scab, stink bugs, and Kondo mealybug.
2. Solutions
Strengthen integrated management and enhance tree resistance. (1) Apply heavy organic fertilizer and additional compound fertilizer, prevent excessive use of chemical fertilizers, and increase the content of effective nutrients in the tree; supplement trace elements rationally, and when applying base fertilizer in autumn, also apply trace elements such as borax and superphosphate; apply foliar fertilizer at the right time, and for orchards where lumpy pear is caused by boron deficiency, spray 0.3%-0.4% borax aqueous solution 2-3 times during the flowering period. In addition, before bagging, spray high-quality calcium fertilizer 2-3 times together with pesticide spraying, such as amino acid calcium, Ruien calcium, and Cuikang calcium treasure, to reduce fruit cracking and physiological diseases caused by calcium deficiency. (2) Irrigate timely in the dry season and drain promptly in the rainy season so that the soil maintains a certain water content and sudden changes in soil moisture are avoided. (3) Cover the orchard with grass or grow grass under the trees to change the microclimate environment. (4) Prune rationally to improve ventilation and light conditions in the tree canopy. Advocate trellis cultivation so that fruit is evenly distributed under the trellis and damage to the fruit surface from branch friction and leaf brushing is reduced. (5) When establishing the orchard, rationally configure pollinizer trees; during the flowering period, use mixed pollen from varieties such as Yali, Yuanhuang, and Huangguan for artificial pollination; strictly thin flowers and fruit, taking care to retain one of the 2nd, 3rd, and 4th positions in the flower cluster, and keep the fruit load at 12,000-13,000 fruits per 667 sq m.
Use pesticides rationally before bagging. Before bagging, 1-2 sprays of high-efficiency, high-quality insecticides and fungicides must be applied. When using pesticides, note: (1) Choose agents that are safe for the fruit surface, such as thiophanate-methyl, carbendazim, polyoxin, and imidacloprid. Take care to choose powders and aqueous formulations and avoid emulsifiable concentrate pesticides. Do not use more than 3 types of pesticides in one spray, the concentration must not be too high, and do not use high-hardness well water or polluted river water for mixing. (2) Pay attention to spraying time. Spray between 7:00-10:00 a.m. or after 4:00 p.m. (3) Improve spraying quality. The nozzle should not be too close to the fruit or stay too long; the droplets should be small and the pesticide solution should be stirred continuously; the spray volume should be just enough to cover the pear fruit densely with fine droplets.
Select high-quality fruit bags and standardize bagging techniques
For Emerald, it is best to choose double-layer bags with a floral outer layer (wood pulp paper) and a black inner layer, or 3-layer bags with a floral outer layer, a black middle layer, and a cotton paper inner layer. The inner black paper should be above 45 g, and the cotton paper should be soft to prevent scratching the young tender epidermis. Bagging generally starts from fruit set and is completed before mid-May; earlier is better than later. For bagging time, choose 8:00-11:00 a.m. and 2:00-6:00 p.m., do not bag under conditions of high temperature and dryness or excessively high humidity, and strictly prohibit bagging when there is dew on the fruit surface or the pesticide solution has not dried. When bagging, the bag should be puffed up, the pear fruit should be in the center of the bag and not attached to the bag, and the bag opening should be tied tightly and securely. During bagging, be careful and cautious to prevent artificial scratching or puncturing of the fruit surface.
Do a good job in disease and pest control. (1) Based on agricultural control, reduce overwintering disease and pest sources through measures such as clearing the orchard in winter and spring, pruning diseased and pest-infested branches, deep digging of the tree, applying freezing water, whitewashing tree trunks, and scraping off rough bark, scaly bark, and diseased spots. During the growing season, control re-infection sources by pruning diseased shoots, diseased leaves, and diseased fruit. (2) Advocate biological control; protect or artificially release predatory natural enemies in the orchard, such as green lacewings, ladybugs, and flower bugs, to achieve pest control by insects. (3) Chemical control should seize the key periods on the basis of good forecasting and reporting. The control schedule is as follows: spray 3-5 degrees Baumé lime sulfur at the flower bud swelling stage. When 70% of petals have fallen, spray 1.8% abamectin 5000x + pyrethroid 2000x + 70% thiophanate-methyl 1000x + 80% fosetyl-aluminum 800x to control pear psylla, black spot disease, pear scab, and black rot. Before bagging in early to mid-May, spray 10% imidacloprid 3000x + pyrethroid 2000x + 80% carbendazim 1000x to control yellow mealybug, green plant bug, and black spot disease. After rain in May, spray methidathion 2000x + 10% polyoxin 1000x to control green plant bug, yellow mealybug, Kondo mealybug, and black rot. Before wheat harvest in early June, spray 1.8% abamectin 5000x + 80% mancozeb 1000x + 48% chlorpyrifos 2000x + adjuvant 1000x. During the fruit expansion period in mid-to-late June, spray 10% imidacloprid 3000x + mancozeb 1200x + adjuvant 1000x. During the rapid fruit expansion period in early to mid-July, spray 48% chlorpyrifos 1500x + 15% pyridaben 3000x + 80% mancozeb 1000x + adjuvant 1000x. During the fruit harvest period, spray pyrethroid 2000x + 20% triadimefon 2000x to control yellow mealybug and Kondo mealybug. When spraying, take care to spray finely, evenly, and thoroughly, so as neither to miss spraying nor to spray repeatedly, thereby improving control effectiveness and preventing pesticide damage.