What is the reason for navel orange falling fruit? Causes and preventive measures of abnormal fruit drop of navel orange before harvest

20 1 1 year is the peak year of navel orange production in southern Jiangxi, and the total output of navel oranges in the whole city is 1.3 million mu, reaching 1.45 million tons. Because there is more rain in the mountainous area of southern Jiangxi after autumn, especially from late June 10 to late October 10/0, the three rains accumulated for five days, and the rainfall reached103 mm. In the later period, the fruits expanded rapidly, the trees were overloaded, and the crowns turned over, resulting in air tightness between trees. After investigation, analysis and summary, the factors leading to abnormal fruit drop of navel orange before harvest and the preventive measures are as follows:

1. Fruit drop caused by pests

① Fruit-sucking moth. At the end of June, 5438+ 10, when the fruit was maturing, the fruit around the middle and upper part of the crown turned fast, and the fruit with strong aroma and good quality fell off about 7 days after being damaged by the fruit sucking moth, and finally rotted on the ground.

② Underground pests. This tree is full of fruits and its crown is turned over. As the fruit grows and matures, the branches droop and the fruit mops the floor close to the soil surface. Underground pests, such as cutworms, crickets, grubs, snails and slugs, compete to harm fruits, causing the fruits near the soil surface to fall off seriously after being injured.

③ Rat damage. The crown of the tree turned over, and as a result, the branches drooped and the fruits dragged the ground close to the soil surface. Mice and mountain rat ate ripe fruit, which caused the fruit to fall off.

2. Fruit drop caused by diseases can be divided into non-communicable diseases and infectious diseases.

① Non-communicable diseases. There are mainly sunburn and fruit cracking. 20 1 1 year, with more flowers and fruits, less shoots in spring, summer and autumn, thin leaf curtain and strong sunshine in August and September. After the fruits around the crown are sunburned, they are easily infected by other germs and fall off. After 5438+ 10 in June, there was too much rain, the growth of peel and pulp was uncoordinated, and the fruit cracked seriously. Cracked fruit is easy to attract flies, mosquitoes, bees and other pests, infected with fungal diseases, but it will fall off before picking.

② Infectious diseases. It is rainy in the mature period of navel orange, which leads to the crown turning over and the branches drooping, and the navel orange orchard with mopping fruit is prone to infectious diseases. There are many fruits, and the orchard has poor permeability, especially the tree tray, which is surrounded by upturned and drooping branches, and becomes a place where germs and pests breed. 20 1 1 There is a lot of rain and high temperature in early winter, and fungal diseases, flies, mosquitoes and bees multiply rapidly, causing serious harm, such as anthracnose and damping-off disease. Sitting in the navel orange garden in Shanwo, sitting in a closed navel orange garden facing south, which has not been pruned for many years, is seriously ill and has many fruits before harvest.

3. Precautionary measures to prevent abnormal fruit drop before harvest, in addition to choosing a good garden, reasonable close planting, high drying, increasing the application of organic fertilizer, and enhancing the tree vigor, other preventive work should be done well around September when the yield is high.

(1) Light traps and kills concentrated pests. From the end of August, 1 black light or multi-frequency vibration insecticidal lamp and solar insecticidal lamp will be installed in every 20 ~ 30 mu of orchard to trap and kill fruit-sucking moths and scarab adults and reduce pre-harvest fruit drop caused by pests.

② Balanced water supply to reduce fruit cracking. After autumn, the rain is scarce and unevenly distributed. In the dry season of summer and autumn, we should make full use of irrigation facilities such as drip irrigation and irrigation in orchards, and mobilize water sources for balanced water supply, so as to meet the physiological demand of fruit expansion for water, prevent fruit cracking and reduce fruit drop caused by fruit cracking.

(3) spray (coat) lime water (slurry) to prevent sunburn. After beginning of autumn, the canopy with less rain, strong sunshine, thin leaves and more fruits outside is easy to get sunburned. From the end of August to the middle of September, 1% ~ 2% limewater can be sprayed on the tree crown, or lime milk (15%) or white paper strips can be applied to the western part of the fruit to reduce the sunburn and the harm of sunburn.

(4) "Support, pull and hang" branches to alleviate crown overturning. At the beginning of September, prepare poles and pull ropes, erect a wooden pole with a root length of about 4m and a stem diameter of 8-1 0cm in the center of the tree crown, hang drooping and mopping branches with a strong plastic rope, hang one end of the pull rope on the central wooden pole, estimate the weight gain when the fruit matures, and try to raise the mopping branches as much as possible to prevent them from gaining weight with the fruit ripening. Keep the branches of navel orange orchard from crossing and closing, so as to facilitate ventilation.

⑤ Appropriate thinning of fruits, changing tips with fruits. Before and after beginning of autumn, thinning the big fruit, diseased fruit, deformed fruit and small fruit on the tree can not only change the branches, thicken the leaf curtain layer, reduce the sun burning, but also reduce the load on the tree and prevent the crown from turning over, the branches from drooping and the fruit from mopping the floor.

⑥ Spraying drugs to prevent infectious diseases. The weather in Koharu is in late autumn and early winter all year round, and the temperature is high. If it rains continuously during this period, it is easy to induce anthracnose, stem rot and gray mold. Prochloraz 1500 times solution or difenoconazole 1000% water dispersible granule 1000 times solution can be sprayed on the tree crown when the rain stops and the weather clears, and then sprayed 1 time after 10, and sprayed continuously for 2-3 times.

⑦ Pick up the fallen fruit of the tree tray and spray disinfectant on the tree tray to reduce the source of the disease.

⑧ Raise chickens in orchards, control insects with chickens, and reduce the fruit drop of pests.

Pet-name ruby as soon as possible to eradicate weeds in orchards and tree trays, clean up the breeding grounds of pests and diseases.

(The author's contact address: Fruit and Tea Bureau, Yudu County, Jiangxi Province, zip code: 342300)