Technical countermeasures for prevention and control of citrus bacterial wilt in orange area of Xinkou town

Citrus bacterial wilt is more harmful, once the disease occurs, it can make citrus plants die quickly. The following takes the orange area of Xinkou Town as an actual case to talk about the occurrence and prevention and control technology of citrus bacterial wilt.

1 present situation of development of citrus industry in orange area of Xinkou town

Xinkou Town is located in the southwest suburb of Sanming City, with geographical coordinates of 117.54037 degrees east longitude and 26.16164 degrees north latitude. The climate is characterized by diversity, the landforms are mainly hills and mountains, the cultivated land area of the whole town is 1400 hm, the woodland area is 1560 hm, and the content of soil organic matter is high, which is very suitable for fruit production, among which citrus production is the most famous.

As an important citrus producing area, Xinkou Town ranks first in Fujian Province in terms of citrus planting area and production, with a citrus planting area of 2000 hm. The main citrus varieties include precocious Wenzhou mandarin, Newhall navel orange and so on. Xinkou Town is a famous citrus production area in Sanming City. By 2017, the annual output of citrus in Xinkou town has exceeded 5.0 × 10kg, and the output of citrus alone accounts for 62.28% of the total output of fruit trees in Sanming. The citrus producing areas in Xinkou town are mainly concentrated in the Shaxi basin. With the help of the good climatic and environmental conditions in the Shaxi basin, the citrus producing areas in Xinkou town show concentrated characteristics. In recent years, Xinkou Town has also made the industrialization adjustment of orange area based on the modern fruit industry construction project in Fujian Province, and has successively established demonstration zones for precocious Wenzhou honey orange, red meat navel orange, Newhall navel orange and other new varieties. At present, the total demonstration area has exceeded 400 hm, which has effectively promoted the adjustment of citrus variety structure in the citrus area of the whole city.

Of course, citrus cultivation in Xinkou Town is also faced with problems, because after May and June every year, citrus plants will have a large area of diseases, including scab, anthracnose, bacterial wilt and so on, especially bacterial wilt, which leads to a large-scale reduction of production in the local orange area. it must first point out its etiology and diseases and control them.

2 Analysis of related problems of citrus bacterial wilt in orange area of Xinkou town

Once the outbreak of citrus plant bacterial wilt, it may cause at least 1 to 3 plants in the whole orchard to be affected by the disease, and the spread rate is very fast. At present, its pathogen is still in doubt, but it should be related to the lack of plant grafting compatibility or external pathogen infection.

2.1 types of bacterial wilt

At present, there are mainly two types of citrus plant bacterial wilt in orange area of Xinkou town: acute sudden type and chronic type. The first is the acute type, which has been recorded from the 1960s to the present. This type of disease has a rapid rhythm and a short course of disease. The course of disease of citrus plants is generally only about 7-12 days from the onset of symptoms to plant death. This type of bacterial wilt is seldom found in orange district of Xinkou town. Compared with the chronic type, the chronic type of citrus bacterial wilt is common in the mountainous areas of Jiangxi and Guangdong, including the orange area of Xinkou Town, which has a long course of 2 to 3 years. Because of the long course of the disease, the symptoms will be divided into early, middle and late stages.

Based on the analysis of the incidence type of chronic bacterial wilt, first of all, its early disease is relatively special. The initially infected citrus plants will sprout and produce a large trunk branch in spring, and a few plants will grow a large backbone branch in the whole plant. This kind of "extra-nodal branches" will seriously affect the growth and development of plants, resulting in "diapause". Compared with the healthy plants, the spring shoot development of the newly felt plants will be relatively slow, and the number of flowers will be significantly reduced. The most obvious manifestation is that the bud development is quite abnormal, which is only the size of soybean grains. Even if the bud blooms, it is only 1 and 3 the size of the normal flower. In addition, the phenomenon of diapause is more obvious in the flowering stage, which is about 21-25 days in the evening than that of normal plants. As a result, it can be judged that the plant has been infected with bacterial wilt, and its fruit type will be only 1 pear 4 of the normal fruit, and the fruit can not mature normally, the quality is relatively poor, and has no commercial value. From the perspective of the law of disease, the initial sensation stage of the early diseased tree will last for 1 year or more, and then it will enter the middle course of disease.

In the middle stage of bacterial wilt, citrus plants will appear more typical diapause phenomenon, plant branches and leaves will appear vertical curls, if the diseased plants will appear on a sunny day in May every year. If it is a mild leaf roll disease plant, it can last for about a year and then enter the late stage of the disease. If it is a seriously leaf roll disease plant, it will soon enter the late stage of the disease.

In the late stage of bacterial wilt, the diseased plant has completely experienced two stages of diapause and leaf curling. in the late stage, the leaves of the diseased plant will show a serious state of water loss and wither rapidly, and the large backbone branches in the initial stage will first dry up to death. The root system of late citrus plants was much less than that of healthy plants, and even some diseased plants showed root necrosis directly.

2.2 Technical measures for prevention and control of citrus bacterial wilt in orange area of Xinkou Town

Citrus bacterial wilt in Xinkou town mostly occurred at the turn of spring and summer (May / June), and some occurred at the turn of autumn and winter (October / November), mainly chronic type. In fact, chronic bacterial wilt began to show symptoms as early as spring (March), such as obvious diapause of citrus plants. For this reason, the agricultural technical station of Xinkou Town also studied the incidence law of bacterial wilt in orange area, and summed up the basic principle of "prevention first, prevention first".

2.2.1 Technical countermeasures for early prevention

The key to the prevention of bacterial wilt of citrus plants lies in the early stage. Taking the orange area of Xinkou Town as an example, its citrus planting should take four preventive measures:

First of all, it is necessary to lower the groundwater level in the orange area in spring as far as possible to avoid the rapid rise of the groundwater level after the arrival of the Meiyu season from May to June, resulting in the groundwater level being uncontrollable during the heavy rain, that is, waterlogging should be prevented in advance to ensure plant safety.

Secondly, close planting should be reasonable and attention should be paid to shaping and pruning to avoid stagnation in the orange area.

Thirdly, it is necessary to strengthen the management of the soil and increase the application of organic matter fertilizer to a certain extent to ensure the depth and looseness of the planting soil and the good air permeability of the soil.

Finally, a certain amount of phosphorus and potassium fertilizer should be properly applied to ensure that the ratio of nitrogen, phosphorus and potassium should be reasonably controlled at 3:2:5, so as to ensure the healthy growth of citrus plants and increase certain disease resistance and stress resistance for the plants themselves.

In the aspect of early prevention, we should also do a good job in inspecting and strengthening the spring bud germination period. for example, once the citrus plants in the orange area enter the germination stage, it is necessary to observe and record each plant every 5-6 days, mainly to observe and record the germination progress of the plants. to see if there is a problem of early diapause. If found, it is necessary to enter the plant treatment period as soon as possible to avoid the spread of pathogens. As mentioned above, the judgment of bacterial wilt of citrus plants should be based on the large backbone branches. if large backbone branches are found, the whole plant must be explicitly renewed, and the first and second grade trunk branches can be retained according to the situation. After the explicit renewal of the whole plant, the diseased plant should be transferred to the stage of intensive management and protection, and emphasis should be placed on the prevention and control of resin disease while treating bacterial wilt, so as to ensure the normal growth and normal flowering and fruiting of citrus plants before 2 years.

2.2.2 Drug control techniques for bacterial wilt

The following two control measures were taken for the control of bacterial wilt of citrus plants in Xinkou town.

First of all, the way of re-cutting the crown and peeling off the soil layer to dry the roots is used to avoid the invasion of pathogens. At the same time, each plant was infused with Bordeaux solution 1.5~2.5kg with the proportion of 1: 1 and 100 Bordeaux solution, and cultivated with guest soil after administration, and re-cutting without drug was carried out to ensure the rapid recovery of the tree potential. In addition, the method of no drug and no re-cutting could be used for control treatment, and targeted analysis and treatment was carried out according to the specific disease condition of the diseased plant.

Secondly, the diseased plant of bacterial wilt should be observed on the spot in the orange area, and the whole plant should be re-cut as soon as the top leaves of the citrus plant had just appeared dry rolls, and at the same time, the rolled leaf branches of the bacterial wilt plant were also cut off three parts, and 1% concentration of copper sulfate solution was sprayed to disinfect the diseased plant. In addition, in order to strengthen the management of fertilizer and water, appropriate organic fertilizer and nitrogen, phosphorus and potassium fertilizer should be applied in the spring to ensure that the diseased citrus plants can recover and be put into production again in the following year after pruning.

According to the above methods, the citrus plants of bacterial wilt were diagnosed and treated periodically in Xinkou town, and some prevention and control results were achieved. In the future, the research on bacterial wilt of citrus plants in orange area should be further studied to achieve scientific management to ensure good and stable citrus production benefits.