Prevention and control of gum disease of growing lemon

Lemon is rich in amino acids, vitamins, a variety of trace elements and other essential nutrients, is an excellent human health fruit. Lemon has a wide range of practical value, increasing demand and broad market prospects; at present, lemon is a tight fruit in the international market and has great potential for commercialization.

Gummy disease is a kind of disease easily infected by lemon, which not only affects the growth and development of plants, reduces fruit yield, but also reduces lemon fruit quality, seriously affects lemon production and the enthusiasm of fruit growers. In recent years, the disease is common in various producing areas, and the rate of diseased plants in individual orchards is as high as 90%, which has attracted great attention.

1 field symptoms

Gummy disease is a common and frequently-occurring disease in lemon production, with different names due to different locations and periods of occurrence. It occurs on tree trunks and is called gummy disease or resin disease. In the field, it is called sand skin disease for leaves and green fruits, and pedicle rot when it harms mature fruits during storage. According to the recurrent infection and self-healing phenomenon of disease spot in the field, the symptoms can be divided into two types: no or no obvious wound disease spot, and no obvious wound disease spot can be divided into glue decay type and glue non-decay type. The cortical rot of glue rot type is the main type of disease in the field, which lasts for a long time and has a large amount of glue. The part of glue flow is mostly in the trunk or main branch bifurcation, and the cortex of the diseased part is waterlogged, oozing translucent yellowish brown glue with foul odor; the bark of the diseased part is loose and shedding, the xylem is exposed, and there are bulging scars around it, and the dense black spots on the surface or under the epidermis of the lesion are conidium. The undecayed part of the glue is reddish brown, the cortex is dry, slightly sunken, and does not peel off. There is an orange-yellow or yellowish-brown belt at the junction between the disease and health, and the glue flow is not obvious.

2 occurrence characteristics

According to the investigation, lemon gummy disease is common in orchards, mainly distributed in the trunk, main branches and their bifurcations, as well as the sunny west and south branches and windward parts prone to freezing injury. The disease is common in the orchards with higher N fertilizer, and the more the results, the more serious the occurrence of gum disease. Gum disease can occur all year round, mostly after the beginning of fruiting, and it is suitable for the disease in spring and autumn, especially in April-May and August-September when it is hot and humid. The occurrence of gum disease is more common and serious in older fruit trees than in young fruit trees and plants with higher N content in leaves and lower ratio of Khand B to K than those with higher K content. The leaves of susceptible fruit trees yellowed and fell off, the tree potential declined, the light ones did not bear fruit, the heavy ones withered, the orchards appeared fallen leaves, withered branches, thin fruit, and the yield and quality decreased seriously.

3 prevention and control countermeasures

Gummy disease seriously affects the yield and quality of lemon. People have done a lot of research on the pathogen, pathogenesis and control measures of the disease, but the control effect is not ideal. At present, there is no very effective control method in production. Therefore, according to the occurrence characteristics of glue disease, it is necessary to take corresponding preventive measures: the first is to carry out seedling quarantine and disinfection, the second is to cultivate disease-free seedlings, the third is to select and plant disease-resistant varieties, and the fourth is to change branches to enhance tree potential. Fifth, pruning and clearing the garden to strengthen management, sixth, anti-freezing and pest control to reduce trauma; of course, it is also very important to explore appropriate treatment measures.

3.1 Clean and hygienic to do a good job in garden cleaning in winter, thoroughly cut off diseased and dead branches, dig up diseased and dead trees and burn them, and close the garden with stone sulfur mixture or pentachlorophenol sodium to kill the source of overwintering bacteria; before the disease occurs in spring, remove and burn the withered branches and leaves of diseases and pests as soon as possible, reduce the source of disease and improve the effect of disease prevention; spray Baume 3 degree lime sulfur mixture to control the spread of bacteria.

3.2 Agricultural control should do a good job in orchard ditching and drainage, improve ecological conditions, improve the level of fertilization, and cultivate the soil and prevent freezing of fruit trees before the temperature drops in winter. The newly-built orchards should choose the terrain with good drainage and convenient irrigation, and choose rootstocks with strong resistance. Strengthening the management of field, fertilizer, water and cultivation in the orchard, increasing the content of K and B, and properly controlling the amount of N are beneficial to the control of gum disease and the improvement of fruit quality.

3.3 physical control, pest prevention and disease prevention, cold prevention and infection prevention are the key links in the management of lemon orchards: first, the trunk is whitened. Scrape off the withered skin of the fruit tree before winter, remove the mildew layer, and brush the trunk and main branches with a layer of white, which can not only kill pathogens and many kinds of overwintering pests, but also enhance the tree's reflection ability, stabilize the temperature difference between day and night, and avoid "sunburn and night freezing".

Secondly, it should be checked frequently and scraped at any time. Once the gummy disease is found, scrape off the diseased part with a sharp knife after alcohol disinfection to the healthy place; then smear the diseased part with 50% carbendazim or topiramate, or 1 ∶ 3 lye, once a week, twice in a row, to promote wound healing.

It is reported that wrapping plastic film can cure gum disease. Warm and moist the glue part of the trunk of the branch, cut off the outer skin of the affected part with a knife until the phloem is good, then wrap it tightly with plastic film, unwrap it again in the peak growth period in the next summer, and in the autumn of the third year, all the big and small branches are cured without recurrence. In addition, the cure rate of flame burning method can reach 100%. Point the blowtorch at the affected area and burn it directly from the outer edge to the center for about 30 to 40 seconds, so that the edge of the decayed part does not show purple-brown glue.

In addition, budding or cutting off the branches at the 10~20cm above the glue and protecting them with medicine, and doing a good job of catching and killing adults of longicorn beetles in summer can prevent and reduce the harm of gum disease.

3.4 Chemical control of diseased orchards and tree trunks requires drug control, and the time of drug use is mainly controlled in the epidemic period of gum disease, and the main control methods are crown spraying protection, trunk whitening and insect control, scraping and spraying in the diseased part, orchard spraying and so on.

In addition, for seriously diseased orchards, before spring shoot germination, 2 / 3 of falling flowers and young fruit stage, combined with the prevention and control of other diseases, 50% carbendazim 800 times solution was sprayed to control leaf and fruit infection diseases. For middle and late maturity varieties, 50% carbendazim 800 times solution plus 1% borax was sprayed once in mid-August. For the existing flowing gum fruit, 1.2% borax was sprayed once and 20mg's 2meme 4murd Djue returned to normal after 5 days. After the fruit was harvested, 50% topiramate or carbendazim 200,500 times solution plus 100~200mg 's 2mem4murD was applied to the fruit pedicle, which was effective in controlling pedicle rot.