Why are Phu Quy orange trees getting sicker and sicker?

Because the largest orange growing area in the province is in some communes of Quy Hop district with an area of ​​2,787 hectares, accounting for 55% of the total orange growing area in the province, it is suffering from yellow leaf disease, causing many fruits and leaves to fall off.

Many Quy Hop oranges fell off due to disease. Photo: Document

A typical example is the household of Mr. Le Quang Hoa in Minh Dinh hamlet, Minh Hop commune, which has an orange garden of over 4 hectares, and the oranges were planted 4-5 years ago for the first harvest, with the hope of getting rich from orange trees on the largest area in Minh Hop commune. However, nearly 1/3 of the orange trees in his garden were infected with yellow leaf disease, with few, small fruits that almost all fell off. Seeing that it was difficult to save, Mr. Hoa used a saw to cut off the diseased orange branches.

Mr. Hoa dug up the trees that were severely infected and replanted them. But in the 2018 orange crop, Mr. Hoa’s orange garden not only did not have less green vein yellowing disease, but the number of infected trees was even higher than in 2017.

Currently, in the Quy Hop and Nghia Dan orange areas, orange growers are very worried because the orange trees have yellow leaves and young fruit that is not yet ready for harvest but both leaves and fruit have fallen all over the ground.

So, what disease does the orange tree have? Why is this disease growing more and more strongly, causing great impact on producers?

If we carefully observe each diseased orange tree, we will see the following symptoms:On diseased leaves, the leaf blade is narrow, the leaves are smaller, the distance between the leaves is shorter, the leaves are yellow, the main vein in the middle of the leaf and the secondary veins are green, so it is called greening disease, common on orange and tangerine trees (scientific name is greening disease).. Orange and tangerine trees with severe greening disease, when dug up, will see rotten roots, most of the fibrous roots are gradually lost, only the main roots remain; even the main roots are rotten. The above symptoms appear on every branch and every tree in the orange garden.

People in Minh Hop commune (Quy Hop) pick up oranges that have fallen from diseased orange trees. Photo: Archive.

The cause of citrus greening disease is the Asian strain of Candidatus Liberibacter Asiaticus (LAS). This bacteria attacks the vascular system of the plant and the disease is spread by the citrus psyllid transmitting the bacteria from the diseased plant to the uninfected plant, from here it is transmitted through the grafted eye when we propagate.

This disease so farThere is no effective treatment or preventionIn recent years, the disease of orange green veins has developed strongly, especially in 2017 and 2018; the disease has developed at a very fast rate in most orange gardens in Quy Hop, Nghia Dan, Tan Ky areas...The reason is the movement of competing to grow oranges and most of them are grown with seedlings grafted with buds taken from diseased trees without knowing in advance..

Most typically, in Quy Hop district, there are up to 9 private establishments specializing in producing orange varieties by grafting orange branches onto the rootstock of a tree to sell freely at a cheap price of 10,000 - 12,000 VND/seedling. When asking a household selling the varieties, they all confirmed that the varieties are good, but in reality, no agency has tested them.

To overcome and limit the disease of yellow leaf veins in orange trees, the following measures need to be taken well:

Plant healthy, disease-free trees. Absolutely do not use orange gardens with diseased trees for propagation, including by grafting and grafting; Cut down and destroy diseased orange trees to prevent the disease from spreading to other trees; For orange gardens with severe disease, boldly remove them to both improve the soil and clean the fields and continue to plant short-term crops for 1-3 years, preferably legumes, then replant oranges; Plant windbreaks around the orange garden with mango, hibiscus or intercropping with guava to limit the transmission of disease by leafhoppers.

A disease-free orange garden is the dream of many orange growers. Photo: Thai Hien

In addition, you should create a canopy and prune branches to make the orange garden airy, limit the crossing of branches between trees. Fertilize sufficiently, balance nitrogen, phosphorus, and potassium. Avoid fertilizing too much nitrogen, which can easily cause orange trees to produce many new shoots, creating an opportunity for leafhoppers to gather to lay eggs, destroy and spread disease widely.

Growers regularly visit orange gardens and, when they detect leafhoppers, immediately spray pesticides to prevent them: Trebon 0.15 - 0.02%, Sherpa 0.1 - 0.2%, Sherzol 0.1 - 0.2%, Bassa, Confidor... spraying 500 - 600 liters of mixed pesticide for 1 hectare (1 sao 25-30 liters of pesticide).

In terms of state management, the provincial Department of Agriculture and districts, cities and towns must regularly inspect orange breeding facilities to ensure that they meet the standards for breeding and producing disease-free orange varieties. If they do not meet these standards, they must be immediately suspended and administratively handled according to the provisions of the Law on Plant Varieties.

In the long term, the province and the agricultural sector need to assign a number of units in the agricultural sector that have sufficient technical facilities and qualified human resources to multiply and produce good orange varieties and disease-free oranges to meet production requirements.