Pistachio tree tuberculosis: causes, symptoms, and prevention

Pistachio tree tubercle is one of the most dangerous bacterial diseases on pistachio trees. How does the farmer deal with it and what is the prevention and control program followed? All of this and more will be explained in this article presented by your website, WORLD OF PLANTS.

What is pistachio tree tuberculosis?

Pistachio crown gall is one of the most important diseases of pistachio trees that leads to a decrease in the life of the tree and the farmer’s yield. Also, this disease affects the pistachio orchard in general and attracts other pests such as insects, spiders, fungi, and harmful bacteria. What are they? Indications or signs of pistachio tree tuberculosis that appear on infected trees, and what are the ways to combat pistachio tree tuberculosis?

Pistachio tree tuberculosis is one of the bacterial diseases caused by Agrobacterium bacteria in pistachio trees in Syria. This disease leads to a general weakness in agricultural production, as well as a weakness in the tree, thus affecting the pistachio’s fruit yield and the tree’s yield to a large extent. The economic threshold estimated losses at about 50-70% of pistachio trees when the injury is critical, and as the injury worsens, the damage may actually reach 80% of the total pistachio crop, and this affects its value as a fruitful plant and the fruits are sold in the market ready to become nuts.

This bacterial disease is transmitted through the soil, especially in the presence of nematodes, and also through seedlings if the farmer obtains pistachio seedlings from an unreliable nursery (or by grafting). It is transmitted by insects and wind, and in general it is a serious disease of the first degree. One of the clear manifestations of tuberculosis in pistachio trees is the leaden-brown tuberous clusters that are seen on the immediate trunk, as well as old and new branches, twigs, leaves, and perennial growth in particular.

These masses may take the form of groups of brown tumors, cancerous cells or ramifications, and large tubers; These tubercles can also look like sores or randomly scattered orange bumps, and the shapes, dimensions, sizes, and even colors of these enlarged lumps vary. The clusters may be flat, elliptical, conical, or in the form of zigzags, cylinders, circles, or eroded areas. They may also be small, large, or of different sizes, and this changes according to the severity of the disease and its progression on a single pistachio tree.

Causes of tuberculosis disease in pistachio trees

There are a number of agricultural, mechanical and chemical factors that encourage the infection of pistachio tree tuberculosis, and the 10 most important factors are:

1. Lack of attention to pruning pistachios (especially removing old, dry and withered branches).
2. Transfer of bacteria from unsterilized soil to pistachio trees.
3. It can be transmitted by nematodes spread in the soil around pistachio trees.
4. The farmer buys unhealthy pistachio seedlings from unreliable nurseries (do not buy well-cared-for pistachio seedlings).
5. Lack of attention to balanced mineral fertilization with nitrogen, phosphorus and potash for pistachio trees encourages the disease.
6. Also, relying on nitrogen fertilizer alone to fertilize pistachios, or increasing nitrogen fertilization, encourages the disease.
7. The presence of weeds infested with pests in the pistachio orchard is a factor that encourages pests and disease.
8. Incorrect pruning of pistachio trees also causes wounds on the tree and exposes it to weakness and disease.
9. Also, using unsterilized pruning shears when pruning a pistachio tree encourages the transfer of bacteria from it to the tree.
10. In addition to the above, bacteria can be transmitted to the pistachio tree through wind, soil, or rain, as a result of mechanical factors.

The danger of tuberculosis in pistachio trees stems from the fact that it weakens the pistachio tree and thus leads to the attraction of new pests to fruit trees and orchards. The attracted pests may be bacterial, such as tuberculosis or ulceration, and they may also be insectic, such as the pistachio thrips and oleander, or the purple scale insect, and the pistachio scale insect. In addition, they may be fungal, such as the wilt fungus, and all of this will affect the value of the pistachio as a fruiting plant and sold in the market. Fresh, delicious and prepared to become nuts.

As the infestation worsens, and the pests spread and interact with each other within the pistachio orchards, the farmer will be forced to apply integrated agricultural pest management to protect the orchard from this disease and other pests. In order to combat tuberculosis of pistachio trees, a set of preventive and curative measures are followed.

Preventive control of pistachio tree tuberculosis

Preventive control is carried out by sterilizing the soil of pistachio trees and getting rid of nematodes, as well as purchasing healthy mother seedlings from a reliable pistachio tree nursery. The farmer also takes care to get rid of weeds and pest spots in the pistachio orchard to a depth of 13 cm, which is repeated three times.

In addition to the above, the farmer must carry out a balanced fertilization process based on nitrogen, phosphorus and potash for the pistachio tree, but without exceeding the necessary limit. The farmer also takes care as much as possible to combat bacteria and fungi that contribute to transmitting the disease to the root and aerial systems of pistachio trees. It should be noted that the farmer must sterilize the pruning shears before pruning, and begin pruning healthy pistachio trees first, and not cause wounds to the tree during this. This is a major factor in transmitting the disease, and pruning operations are performed by removing all tangled and crowded branches.

Therapeutic control of pistachio tree tuberculosis

In fact, there is no completely guaranteed treatment for tuberculosis that affects pistachio trees. Despite this, pesticides and integrated control are used, in order to eliminate the fungi and insects that spread pistachio tuberculosis, as well as nematodes and others. It is recommended to use a systemic fungicide based on benzimidazole and strobilin derivatives. The pesticide Mancozeb also gives good effectiveness. It is also recommended to use the pesticide carbendazim by spraying perennial parts, especially pistachios.

In addition, phosphorus insecticides can be used to eliminate insects that carry bacteria, such as parathion-methyl, by spraying the leaves and branches of pistachio trees.

These measures are responsible for eliminating the wilt fungus, bark insects (the pistachio bark beetle), and borers (capnoids), and thus preventing or treating this disease. Despite all of the above, it is difficult to treat this disease.

Episode of pesticide use against pistachio tree tuberculosis

To avoid the formation of resistant strains of bacteria in infected pistachio orchards and areas where pistachios are grown, a special pesticide program is followed. In the first season of infection, the pesticide Dimeton-s-methyl is used by spraying on the branches, branches and trunks of pistachio trees infected with bacteria, especially old, corroded ones.

In the season following the infection of grapes, the pesticide Parathion methyl is used by spraying on pistachio trees infected with the bacteria, targeting branches, trunks, and twigs, both old and young. While in the third season, the pesticide Dimethoate is sprayed on pistachio trees on young and old branches and branches, and the same ring is changed after 9 years and new pesticides are used provided that they have the same properties and (the composition differs somewhat) and that they are organic phosphorous so as not to harm pollinating bees or enemies. And natural predators.

It is recommended to conduct integrated control of tuberculosis in pistachio trees when the pests interfere with each other along with tuberculosis in the pistachio orchard. Control is carried out through the use of traps hung on trees to catch gnat moths such as the moth (the pistachio fruit worm), the leaf miner, the borer, and the pistachio stem borer (Capnodus). ; Just as the soil is sterilized with Promed methyl bromide gas, sterilization can also be done with solar energy, where a polyethylene plastic cover is stretched over the soil of the pistachio tree around the crown site throughout the summer to raise the soil temperature, thus eliminating pests.

It is also possible to sterilize with sodium metam, or by scattering endosulfan granules around the trunks or the crown of the pistachio tree, or mixing it with the soil and stirring it well.

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