What are the symptoms of tristeza disease in navel orange seedlings?

Tristeza disease is a disease that citrus fruit trees are highly susceptible to. It occurs commonly all over the world and causes disasters in many regions, so what are the symptoms of tristeza disease in navel orange seedlings?

1. What is tristeza disease?

Tristeza disease is a disease caused by citrus tristeza virus. The citrus tristeza virus particles are filamentous, with a length and width of 2000 nanometers × (10-12) nanometers. Long-distance spread of citrus tristeza disease occurs through the transport of virus-carrying seedlings and grafting material, while short-distance spread in the field occurs through aphids moving between diseased plants, symptomless carrier plants and healthy plants, among which the brown citrus aphid has the strongest ability to transmit the disease.

After a plant becomes diseased, sunken spots and sunken grooves appear in the xylem of the branches and trunk. When damage is severe, the branches and trunk appear longitudinally uneven, the fruit becomes smaller, and tree vigor weakens.

2. Symptoms of tristeza disease in navel orange seedlings

1. The canopy is noticeably stunted, the number of spring shoots is small and weak, the leaves have poor gloss, and the flower quantity is large;

2. Flower drop and fruit drop are severe, fruit set is low and fruit development is stunted, the fruit is small, the navel area is relatively flat, and the fruit shape is irregular.

If it is a 1-year-old or older mature twig, it is brittle and breaks easily, making a “snap” sound when broken, and the broken end is relatively neat; the bark is relatively easy to peel off, and obvious sunken spots or sunken grooves can be seen in the xylem.

3. How is tristeza disease prevented and controlled?

1. Use disease-tolerant rootstocks such as trifoliate orange, sour mandarin, red tangerine, sweet orange and Citrumelo;

2. In diseased areas, seedlings should first be inoculated with mild strains, which can protect them from infection by severe strains

3. Implement quarantine to prevent the introduction of new severe strains from abroad;

4. Timely control vector insects and aphids;

5. As far as possible, collect scions from disease-free mother plants that have been regularly indexed on indicator plants; scions or seedlings that may carry the disease must be treated with 50°C moist hot air for 7-22 hours.