Alternaria late blight of pistachios is a disease that greatly affects the quality and productivity of the crop. In this article on your site, WORLD OF PLANTS, we will learn about the symptoms of the disease, its causes, and effective methods of prevention and treatment.
A brief definition of Alternaria late blight of pistachios
Symptoms of Alternaria late blight in pistachios appear in the form of widespread, fine, dark brown spots on the leaves with black centres. This is followed by leaf wilting and premature defoliation, then brown circular necrotic spots appear on the fruits surrounded by a red halo. As these spots grow, Mold begins to grow on it.
There are three types of this disease that affect pistachios. This disease appeared in 2008 in America, and it leads to a decrease in yield. It also prefers high humidity, so the dry climate contributes to reducing it. Below are some points that explain the causes, symptoms, and methods. Treatment of disease:
- Pathogens: This disease is caused by a black lesion called Alternaria.
- Symptoms of the diseaseBlack spots appear with a red edge, then the spores infect in humid weather, and may lead to leaf fall in an advanced period of the disease.
- Methods of TreatmentIt is recommended to spray appropriate insecticides, irrigate the tree well, and remove weeds around it.
Symptoms of Alternaria late blight in pistachios
Symptoms generally appear in summer and are characterized by the presence of angular or circular spots ranging from 3 to 7 mm in diameter on the leaves. In some severe cases or in particularly susceptible varieties, the spots become spots up to 3 cm in diameter. Black spots are also present on petioles and veins. The main source of the leaf blades, and severe infection can lead to the leaves withering and falling.
On immature fruits, fine brown or black spots appear, while on mature fruits, the spots are somewhat larger in diameter (from 1 to 5 mm) and surrounded by a red halo. Mold begins to grow on the fruit, leading to its decay. However, in cases of severe infection The disease greatly reduces the quality of the product.
Organic control of Alternaria late blight in pistachios
Spray the Bordeaux mixture on trees and cuttings after pruning the affected parts. Alternatively, you can apply a mixture of garlic or plantain on the leaves and fruits. You can also use solutions based on the bacteria Bacillus subtilis, which is a predator of fungi.
Chemical control of Alternaria late blight of pistachios
Always consider integrated pest management with preventive measures and biological treatments if available. Treatment against this disease should begin in early summer, before the fruits ripen. Products based on the active ingredients methyl thiophonate, manip, and copper products work well.
At least two treatments are needed to reduce the incidence. The effectiveness of treatment depends on the timing of spraying, proportionality to the age of the tree, and application of the recommended dose.
Cause of Alternaria late blight in pistachios
The symptoms are caused by a group of three fungi of the genus Alternaria, among others the genus Alternaria, which hibernate in the soil or in plant debris, and when conditions are favorable they produce spores that are transported by wind and rain to susceptible trees.
High temperatures associated with high humidity, including dew formation, alternating wet and sunny periods, and nutrient deficiencies are major factors in the development of the disease on pistachios. The symptoms of this disease can be confused with those of flower bud blight caused by Pietrosphaeria dunidia.
To differentiate between them, rub the affected leaves when wet conditions prevail: if your fingers become black, it is late blight caused by Alternaria.
Preventive measures for Alternaria late blight in pistachios
- Use varieties that are less susceptible to disease and use healthy seeds from certified sources.
- Avoid tight planting to promote ventilation within the canopy.
- Inspect the orchard regularly to detect the first signs of the disease.
- And control weeds on the orchard land.
- Cut and burn the affected parts as soon as the first symptoms appear.
- Also prune trees during dormant times to obtain well-ventilated canopies.
- Avoid irrigation by spraying, especially during the ripening of fruits.
- Remove crop residues after harvest and burn them.
- Above all, do not compost these plant parts because they will carry the disease to another season.
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References
Pistachio tree diseases: Discover them - planting.mawdoo3
Alternaria late blight - plantix
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