Management of summer citrus orchards

In terms of the phenological period of citrus growth and development, summer is in the period from the young fruit stage (the second physiological fruit drop period) to the summer shoot emergence period, and the citrus fruit enters the expansion period, which requires a large amount of fertilizer and water, which is also the peak of citrus diseases and insect pests. Therefore, it is very important to strengthen the summer management of citrus orchards. Whether the management measures are in place or not has a great impact on the current year's yield and fruit quality. Specific management should do a good job in the following aspects:

First, apply enough fertilizer to promote trees and protect fruit. During the expansion period of citrus fruit, the root system has strong fertilizer absorption, and sufficient fertilizer is applied in time to make the young fruit get enough nutrition, which can reduce fruit drop, increase fruit setting rate and ensure high yield. According to the practice of fruit growers, late-acting fertilizer is applied deeply, and each fruiting tree is applied according to tree age and fruiting amount, livestock and poultry manure 20ml 25kg, cake fertilizer 1Mel 15kg, calcium superphosphate or bone meal 0.5ml 1kg. The fruiting trees should be fertilized twice with 0.2% urea and 0.2% potassium dihydrogen phosphate, and the symptoms of element deficiency in the new leaves should be sprayed. In the case of high temperature and drought, spraying hormone can also promote root cell division, improve absorptive capacity, and have a certain effect on preventing fruit drop. Note: fertilization should be based on trees, and for varieties that are easy to draw June shoots, the topdressing should be avoided to prevent fruit drop; no or less application should be applied to primary fruit trees or fruit trees with few flowers and fruits, so as not to cause summer shoots and new shoots to compete for nutrients and drop fruit. In mid-July (about 15 days before autumn shoots), sufficient fertilizer for strengthening fruit and promoting shoot should be applied. The amount of fertilizer should account for 40% of the total amount of fertilizer applied throughout the year. The fertilizer should be mainly organic fertilizer (80% organic fertilizer). Each plant should apply 25ml 50 kg of rotten manure water, and add 0.5 kilogram cake fertilizer, 150 grams urea, 150 grams potash fertilizer, or 250 grams compound fertilizer.

Second, strengthen water management, resist drought and cool down. Moisture plays a decisive role in the size and yield of citrus fruit. There are three peaks of citrus fruit expansion from June to October, the first in June, the second from early July to early August, and the third from late September to early October. Generally speaking, although the fruit growth is the largest at the first peak, it is during the rainy season, so it is difficult to have a water deficit. The second peak fruit expansion rate is second only to the first, when the summer and autumn summer drought season, the most vulnerable to water stress, and there are a large number of irreversible small fruits, so this stage is the critical period to determine the yield and large fruit rate. it is necessary to do everything possible to meet the water requirements of the fruit, expired irrigation, small fruit is difficult to re-expand. Therefore, in the management of water from May to July, we should pay attention to drainage in the early stage to prevent stagnant water in the orchard and produce "stuffy roots"; in the middle and later stages, we should pay attention to irrigation to prevent small fruits and affect the quality and yield. The soil moisture content should be kept at about 20%.

Mountain orchards should repair and strengthen the drainage and irrigation system to prevent soil erosion caused by torrential rain. At the same time, we should do a good job in resisting drought and cooling to prevent fruit falling at high temperature. When the growth of citrus is more than 35 ℃, the photosynthesis is weakened and the physiological function is blocked. Therefore, when the high temperature comes, when it is found that the citrus leaves begin to curl, it is necessary to draw water into the orchard in time to adjust the temperature and humidification with water. Conditional sprinkler irrigation is available to increase air temperature and soil moisture. And loosen the soil by ploughing, cut off the soil capillaries and improve the ability of water and fertilizer conservation, so as to improve the orchard microclimate, reduce fruit drop and promote strong fruit. At this time, in the hot summer of high temperature and drought, it is necessary to cut grass to cover the orchard ground to reduce direct sunlight and water evaporation, reduce the surface soil moisture, protect the root group, enhance the root activity and reduce the fruit drop rate.

Third, erase the summer shoot and promote the autumn shoot. As a result, the trees should wipe off the summer shoots and keep them all the way up to the autumn shoots, so as to reduce the consumption of a lot of nutrients and ensure that the autumn shoots are strong. For old trees and trees with a large amount of fruit, autumn shoots should be put earlier, while for young trees, low-yield trees and empty trees, they can be a little later. It is generally required to shoot from late July to mid-August. Sweet oranges are suitable for shoot in August.

Fourth, do a good job in the prevention and control of diseases and insect pests and promote high yield and high quality. The main diseases easy to occur at this stage are scab, canker, anthrax, and the main pests are scale insects, longicorn beetles, red spiders, rust wall lice, leaf miner and so on. Local aphids, wood lice, whitefly harm. In July and August, citrus fruits are inflated and are easily harmed by fruit-sucking armyworm, often causing a large number of fruit drops; serious rust wall lice will cause fallen leaves, and the fruit will turn purple-brown; red spiders will cause citrus tree growth atrophy, fallen leaves withered branches, making leaves white and gray; leaf miner harms new shoots, and larvae feed under the epidermis of young leaves, which will seriously curl the leaves and affect their growth.

Canker disease: the combination of tip control and anti-leaf moth, to achieve "zero retention, early retention, strong pressure, concentrated spraying to control leaf moth". Leaf miner can use 10000 times of 5% avermectin EC, or 3000-4000 times of pyrethroid pesticides. Spray again every 5-7 days. When the tip is about 12 leaves, take off the top, spray 3% gram gram kang wettable powder 1000 times or 600 × 1000 unit / ml agricultural streptomycin plus 1% alcohol as auxiliary agent, if mixed with 80% Dasheng Mmur45 wettable powder, it can not only improve the efficacy, but also treat fungal diseases. Young trees can also use 77% Donin 400-600 times solution to prevent canker.

Longicorn beetles: according to the habit that adults usually perch at the end of branches at noon in sunny days and lay eggs at the base of tree trunks around dusk, longicorn beetles are artificially killed. Chemical control can be done by spraying tree trunks with 5% Regent suspension 1000Mel 1500 times in mid-May, with an interval of 15 days. In addition, regular inspection of citrus orchards, timely scrape off eggs and larvae, hook larvae or drugs to block wormholes.

Red spider: often check the insect situation, found that there are more than 20% of the leaves, an average of more than 2 red spiders per leaf should be sprayed in time. The medicine can be treated with 50% Tolk wettable powder (propargyl tin) 2000 times 2500 times 5% nisorone EC 3000 times plus sulfur glue suspension 400 times or 20% paracetamol wettable powder 4000 times or 15% up to 3000 times 4 000 times of acarone EC or 1500 times of 25% triazol tin wettable powder.

Rust wall lice: pay attention to check the insect situation. 20% of the leaves and fruits found to have rust wall lice should be sprayed immediately. Pesticides can be used with 1.8% avermectin EC 2000ml 3000 times or 80% Dasheng Mel 45 wettable powder 600x or 65% Antaisen zinc wettable powder 1000 times or 2.5% dichloromethyl EC 30005000x or 73% propargite EC 2000 times or stone sulfur mixture 0.3 Baume. The spray should be rotated to avoid drug resistance. The mites were treated with 1500-fold solution or Dasheng Mmur45.

Leaf miner: in addition to wiping buds and controlling shoots and cutting off insect sources, spraying should be done when the shoots grow 2~3cm, and then spray continuously for 2 times every 5-7 days. Pesticides can be controlled by pyrethroids (such as pyrethroid, methotrexate, paracetamol, dipai) plus "312" or avermectins (such as Kun de, ketotin, avermectin).

Fifth, interplanting green manure and using land to raise land. From the point of view of fertilization in citrus producing areas in our city, there are serious shortage of organic fertilizer, excessive nitrogen and phosphorus and lack of potassium. Excessive nitrogen not only affects the improvement of quality, but also reduces the availability of copper, zinc, manganese and molybdenum, and reduces the occurrence of absorbing roots. Large kinds of green manure should be advocated, land should be used to cultivate land and soil fertility should be improved. If the intercropping of green manure per mu of citrus orchard can produce 4000 jin of fresh grass, it can increase pure nitrogen by 15-25 jin per mu, equivalent to 32-54 jin of urea and 88-147jin of ammonium bicarbonate, reduce soil erosion, stabilize soil temperature and humidity, and improve the ecological environment of the orchard. Therefore, we should encourage the orchard to interplant legume green manure, such as Pinto peanut, orchard leaf cassia, feather leaf cassia, thistle, black mung bean, Indian cowpea and other green manure, and cut green in time to cover or press green, in order to improve the soil.

Sixth, do a good job in pruning and thinning fruit in summer to improve the quality of fruit. The key point of pruning in summer is to improve crown distribution, improve permeability, adjust the contradiction between results and shoots, and take pruning measures of wiping buds and controlling shoots, pulling, brace, hanging and thinning. Fruit thinning can adjust the tree load, effectively overcome the annual fruit, and increase the weight of single fruit. The fruit thinning time was carried out at the end of the second physiological fruit drop, and the thinning was done again at the beginning of August. In the method, the fruits of diseases, insects, deformed fruits, overgrown branches and slender branches should be thinned first. Standard: through fruit thinning according to different varieties, it is required to achieve the corresponding leaf-fruit ratio, such as generally warm 25:1, early warm, sweet orange 45:1, mandarin 60-70:1 is better. If the ratio of leaf to fruit is large, it will also cause coarse skin and large fruit, which will reduce the quality.