What are the symptoms and characteristics of jujube rust? How to prevent and control it well?

During the growth of jujube trees, they are very susceptible to jujube rust, which mainly threatens the leaves of jujube trees, causing early defoliation and other situations, leading to reduced sweetness of jujubes, fruit drop, and other occurrences, resulting in reduced yields for growers. Jujube rust only occurs on the leaves. Initially, pale green small spots are scattered on the underside of the leaves, then gradually bulge and become dark yellowish-brown, which are the uredinia of the pathogen. So what are the symptoms and characteristics of jujube rust? How to prevent and control it well?

I. What are the symptoms and characteristics of jujube rust?

1. Symptoms of jujube rust

Jujube rust only occurs on the leaves. Initially, pale green small spots are scattered on the underside of the leaves, then gradually bulge and become dark yellowish-brown, which are the uredinia of the pathogen. The uredinia are irregular in shape, about 0.5 mm in diameter, mostly occurring on both sides of the midrib, at the leaf tip and base. Later, the epidermis ruptures, releasing yellow powdery matter, which are the urediniospores. On the upper surface of the leaf, corresponding to the uredinia, green small spots appear with irregular edges. The leaf surface becomes leaf-like in appearance, gradually loses its luster, and finally dries up and falls off early. Defoliation starts from the lower part of the canopy and gradually spreads upward. Telia generally occur more after the leaves have fallen, are black, smaller than the uredinia, 0.2-0.5 mm in diameter, dark brown, slightly raised, but do not break through the epidermis.

2. Characteristics of jujube rust

The severity of jujube rust each year is closely related to the amount of rainfall in July and August. When the total rainfall in July in jujube-growing areas reaches 200-300 mm, the disease occurs early and severely. If it is less than 130 mm, the disease occurs late and mildly. After a major outbreak of jujube rust throughout the county last year, the possibility of a major outbreak of jujube rust this year is very high.

In jujube groves located in ditch bottoms, irrigated land, low-lying areas, or wind-trapped sites, rust is more severe, with serious defoliation and fruit drop. From disease onset to defoliation takes about 30 days, and causing defoliation of the entire tree takes about 2 months.

II. How to prevent and control jujube rust well?

1. During winter orchard sanitation, collect diseased fallen leaves and burn them to reduce the source of pathogens for the coming year.

2. For jujube orchards in low-lying areas, do a good job of drainage to prevent water accumulation in the orchard from causing death of fruit tree roots.

3. Apply heavy base fertilizer to jujube trees, mainly organic fertilizer, combined with phosphorus and potassium fertilizers, and avoid excessive application of nitrogen fertilizer, to improve the disease resistance of jujube trees.

4. For vigorously growing jujube orchards, carry out proper pruning to facilitate ventilation and light penetration, strengthen tree vigor, and improve the tree's disease resistance. Pruning should focus on thinning branches. New jujube heads sprouting from jujube spurs and new jujube heads sprouting inside the canopy should be promptly thinned out if not needed, to reduce nutrient consumption and improve ventilation and light conditions.

5. Timely control of rust mites.

6. In July and early August, spray jujube trees with pesticides for control. Bordeaux mixture at 200 times dilution, or 70% thiophanate-methyl wettable powder at 800 times dilution can be used.