Rust is an infectious disease of plants, caused by pathogenic microscopic fungi, which occurs by the appearance of reddish-brown spots on leaves, stems, or inflorescences, stopping normal leaf development.

BEAN RUST – UROMYCES APPENDICULATUS

It is a common disease in bean and broad bean crops.

Symptom. The disease occurs mainly on leaves and less frequently on stems and pods. In spring, the leaves show whitish, then yellowish-brown spots, where on the upper side there are small dots representing the pycnidia of the fungus, and on the lower side there are yellowish aecidia, often arranged in circles. This stage occurs less frequently in nature or may go unnoticed. In general, attacked plants show urediniospores and teliospores. In June, small, pinkish-brown powdery pustules appear on the above-ground organs of the plants, representing the urediniospores of the fungus. In August, blackish powdery pustules appear, formed by the teliospores of the fungus.

Leaves that are heavily and early attacked twist, dry out, and fall prematurely with implications for crop yield.

The fungus overwinters in the soil or on the ground as teliospores or even on the debris of attacked plants.

Prophylaxis. It is recommended to remove and destroy the bean bushes remaining after harvesting, cultivate resistant varieties, apply a crop rotation in which the beans return to the same area of land after 3-4 years.

During the vegetation, specific fungicide treatments are applied.

CARNATION RUST – UROMYCES CARYOPHYLLINUS

The disease has been observed in most countries where carnations are grown in greenhouses. 

Symptom. The attack occurs on all above-ground organs of plants, more frequently on leaves and stems. Small, round, 1 mm diameter, or oval, yellow-brown spots appear on leaves.

Small circular or ovoid, dark-brown pustules appear on the attacked tissues, showing the urediniospores of the fungus, which are arranged in concentric circles, both on the upper and lower part of the leaves. Later, on the leaves in the same areas, the fungus telia appear in the form of brownish-black pustules, which frequently converge.

Heavily attacked leaves turn yellow and dry out, leading to poor plant growth. If flower stalks are attacked all around, sap circulation is interrupted and plants dry out above the areas of attack.

The fungus overwinters in the soil or on the ground as teleutospores or even on the debris of attacked plants.

Prophylaxis. It is recommended to control the crops, plants showing symptoms of the disease should be removed and destroyed by burning, only seedlings from healthy plants should be used for propagation.

During the growing season treatments with specific fungicides are recommended.

BROWN RUST OF WHEAT – PUCCINIA RECONDITA

It is a disease widespread all over the world and is also known as leaf rust.

Symptom. Both sides of the leaf blade (more commonly the upper one) are attacked, especially the stems and never the spikelets. The disease appears in April, with the greatest intensity in May and June. Isolated, brown, elliptical or oval, powdery, irregularly spreading pustules of uredospores appear on the attacked organs.

Towards the end of the wheat’s growing season, usually, when the leaves begin to turn yellow, small, blackish, shiny, epidermis-covered pustules appear, scattered irregularly on the stem and containing teliospores.

During the growing season, brown rust is spread by uredospores, which depending on environmental conditions can produce 5 to 15 secondary infections.

Prophylaxis. Cultivation of resistant varieties is recommended, harvesting at the optimum time to avoid shaking the caryopses.

Chemical control is achieved by carrying out treatments with specific fungicides.

YELLOW RUST OF WHEAT – PUCCINIA STRIIFORMIS

It is a very damaging disease, especially in cold and wet temperate regions.

Symptom. The disease is also known as glumes’ rust. Both sides of the leaf are attacked, especially the upper side, the stems, aristae, glumes, and caryopses. In the sprouting and flowering period, rectangular, lemon-yellow uredospores appear on the leaves, starting with the basal ones, arranged in a parallel line between the veins, which alternate with unattached green areas containing the uredospores of the fungus.

On the stems, the disease occurs mainly in the upper part, forming stripes similar to those on the leaves.

Stripes with isolated pustules form on the ears, on the ears’ rachis, on the ears’ stalks, and on the aristae. Towards the end of the growing season, black, shiny telia form on the attacked organs, arranged like the uredospores and containing teleutospores. The attack results in premature drying of the leaves and pronounced dieback of the caryopses.

The spread of the fungus during the growing season is via uredospores, which germinate and produce secondary infections at low temperatures (10-12º C) and high humidity (over 80%).

Prophylaxis. Cultivation of resistant varieties is recommended, harvesting at the optimum time to avoid shaking the caryopses.

Chemical control is achieved by carrying out treatments with specific fungicides.

BLACK RUST OF WHEAT – PUCCINIA GRAMINIS

The disease is also known as “straw rust” or “linear rust”. It is widespread in all regions where wheat is grown and is considered the most damaging disease of wheat.

Symptom. All above-ground organs are attacked, the disease is observed in the field when the wheat is approaching maturity. Elongated, linear pustules form on the attacked organs, which merge and reach up to 1-2 mm in length. At first, the pustules are brown, consisting of uredospores, and later become black, containing teleutospores forming longitudinal stripes mainly on the stem, leaves, and ears.

The fungus overwinters as teleutospores in cultivated cereal crops and volunteer grasses.

Prophylaxis. Cultivation of resistant varieties is recommended, harvesting at the optimum time to avoid shaking the caryopses.

Chemical control is achieved by carrying out treatments with specific fungicides.

SUNFLOWER RUST – PUCCINIA HELIANTHI

The disease occurs in all sunflower growing areas, causing greater damage in years with cool, rainy summers.

Symptom. The disease appears in early spring, either on the cotyledons or on the leaves at the base of plants. Yellowish-orange, circular spots 5-10 mm in diameter appear. The pycnidia and aecials of the fungus form around these spots. Later, in June-July, especially on the underside of the leaves, numerous small, isolated, or confluent, brownish-brown, dusty pustules appear, consisting of the fungal uredospores.

Towards autumn, among the uredospore pustules, other pustules appear, of a brownish-black color, formed by teleutospores. Heavily attacked leaves wither and dry out prematurely.

The fungus spreading during the growing season is via uredospores, which produce numerous secondary infections. Transmission of the disease from one season to the next is via teleutospores, the form in which the fungus overwinters in plant debris in the soil.

Prophylaxis. It is recommended to collect and destroy plant debris left in the field after harvesting, deep plowing, cultivation of rust-resistant varieties.

Chemical control is achieved by carrying out treatments with specific fungicides.

PLUM LEAF RUST – TRANZSCHELIA PRUNI-SPINOSAE

The disease is widespread in all plum-growing areas and less frequently reported on apricot, peach, and almond.

Symptom. The attack of the pathogen occurs at the end of July when small yellow spots appear on the upper part of the plum leaves. On the underside of the leaves, to the right of the yellow spots, brown uredospores and black telia form. The uredospores and telia are irregularly arranged and have a powdery appearance. A strong attack leads to premature defoliation, low yields, and low quality, and reduced frost resistance of the trees.

Transmission of the disease from one year to the next is via teleutospores or resistance mycelium, the form under which the fungus overwinters.

Prophylaxis. It is recommended to gather and burn affected leaves to reduce the source of infection.

Chemical control is achieved by applying treatments during the growing season with specific fungicides.

ROSE RUST – PHRAGMIDIUM DISCIFLORUM

The disease is commonly found in cultivated rose varieties as well as wild species of the genus Rosa.

Symptom. The attack occurs on all above-ground plant organs (leaves, young branches, flower stalks, and buds). The attack starts in spring when yellow spots appear on the upper side of the leaves, where orange, circular clusters form on the lower side, representing the aecia of the fungus in which aeciospores form. Starting in the second half of May, discoloration spots appear on the aeciospores-infected leaves, at first isolated, then confluent. Small, light yellow pustules, representing uredospores, form on the underside of the limb next to the spots.

Numerous uredospores form and produce repeated infections during the growing season. Later (June) blackish powdery pustules appear, which represent telia.

The fungus can also overwinter in the form of resistance mycelia in the attacked branches on which aecia with aeciospores capable of producing new infections form in the spring.

Prophylaxis. It is recommended to prune and collect heavily attacked branches, to collect and burn fallen leaves in order to reduce the source of infection, to cultivate resistant varieties.

Chemical control is carried out with specific fungicides.