Azaleas are shrubs with beautiful flowers and attractive leaves. They look great until they are attackedazalea pests or diseasesAs a result of pathogens attackazalea leaves turn yellow, turn brown, dry and fall offSee how to identify individual diseases and azalea pests based on the symptoms observed, as well as how to help damaged plants. We recommend the bestspraying for azalea diseases !
Diseases of azaleas: (1) phytophthorosis, (2) powdery mildew, (3) leaf spot
Azalea fungal diseases
1. Phytophthora(Phytophthora cinnamomi, P. nicotianae var. Nicotianae)
Phytophthorosis is one of themost dangerous fungal diseases of azaleasIt is caused by Phytophthora fungi, which infect the hair roots responsible for water uptake. The fungus spreads through water and contaminated soil and enters the plant through wounds and lesions on the roots and in the root collar. The development of phytophthora is favored by high substrate humidity, water lying in the substrate, as well as warm (temperatures above 20 ° C) and humid weather.
Phytophthorosis on azaleas is manifested by wilt of the tops of the shoots and fading of the leaves. Over timethe leaves of the azaleas turn brown, dry and curl in a characteristic boat shape along the main nerveThe diseased leaves do not fall off, but remain on the shoots. The symptoms of the disease gradually spread downwards. With time, all shoots and bushes die.After removing the plant from the ground, you can notice a distinct rusty red discoloration on the root neck and a strong reduction of the root system.
Phytophthora is very difficult to combat, therefore prophylaxis is an important element of azalea care. The disease development can be limited by using an appropriate acidic rhododendron medium and composted pine bark mulch. The fungi that cause this disease are resistant to most plant protection preparations.
To combat phytophthora on azaleasbiological agents are used, for example Biosept Active (5-10 ml / 10 l of water) or Polyversum WP (5 g / 10 l of water). However, it should be remembered that they are effective only in the early stages of the disease. Heavily infested bushes should be dug up and burned, and the soil in the place where they grew must be decontaminated, because the disease can survive there for even several years.
2. Azalea powdery mildew(Microsphaera penicillata)
The seconddangerous disease of azaleas is powdery mildewDisease development is favored by moist and warm air, too high plant density and nitrogen over-fertilization. The spores of the fungus spread with wind and splashing water during rainfall. The firstsymptoms of powdery mildew on azaleasappear in mid-summer.
At first, small, irregular, white spots appear on the leaves of the azalea, covered with a powdery coating The tissue in the places where the tarnish occurs turns a red-brown color. With time, the spots spread to the entire leaf blade and the tops of the shoots.Infected leaves begin to curl down and fall offThen shoots gradually turn black and die. The development of diseased bushes is visibly slowed down.
The spores of the powdery mildew fungus hibernate on fallen leaves and in stem tissues and shrub buds. Therefore,in autumn you should rake and remove all leaves from under the shrubsand remove and destroy infected plant shoots.After the first symptoms of the disease are noticed on the azalea, the bushes should be sprayed with a protective preparation. The above-mentioned preparations used to combat phytophthora (Biosept Active, Polyversum WP) are effective protection.In conditions favorable to the development of powdery mildew, natural preparations of nettle, horsetail or yarrow can be used prophylactically.
3. Azalea leaf spot(e.g. Septoria azalae, Cercospora Handelii, Phyllostica cunninghamii, Pestalotia spp)
Another commonazalea disease is leaf spotThis disease can be caused by various species of parasitic fungi. It develops on bushes growing in too high a density, preventing proper air circulation. The appearance of the disease is additionally favored by soaking the leaves during watering and longer periods of rainy weather.
The first symptoms of blotch are observed in the second half of summer.Single spots appear on young azalea leaves, scattered over the entire surface of the leaf blade They can be brown, red or brown, most often with a border. They clearly stand out from he althy tissue. In severe infestation, the spots merge with each other and occupy a significant part of the leaf surface.Sick azalea leaves slowly turn yellow, dry and fall off the shrubsOn the lower side of the leaves, where the spots appear, a raid appears. mycelium and fungus spores.
Leafspot is not a very serious disease of azaleas and is relatively easy to combat. It is very important to remove and destroy all diseased leaves.To cure sick azaleas, spraywith ecological agents (e.g. Biosep Active) or, as a last resort, with chemical agents (e.g. Topsin M 500 SC at a dose of 15 ml in 10 l of water).
Holes in the leaves of azaleas bitten by swellings
Fig. depositphotos.com
Azalea pests
1. Strawberry opuchlak(Otiorhynchus sulcatus)
The most commonpest on azalea shrubs is the strawberry mothIt is a small beetle that appears on azaleas in May-June. During the day, adult beetles hide under plant debris or underground. They come out of their hiding places at night and feed,gnawing on the edges of azalea leaves small semicircular holesand destroying the buds. Much more damage is done by the larvae of the oozing larvae, which damage the roots and the root collar. Damagedazalea bushes wilt and die , despite adequate substrate moisture.
In order to fight the larvae of the weeds , apply soil-based biological agents, e.g. P-DRAKOL (dissolve 10g of the preparation in 2-5 liters of water, which is enough for an area of 100m² of cultivation).
An effectiveway to fight adult swollen is trappingThe role of such traps can be old boards or empty, unnecessary dishes that are placed under azaleas.Beetles seeking shelter for the night will use such hiding places. In the morning, it is enough to carry a board or a vessel and choose sleeping beetles from it. Prophylactically or when you noticesymptoms of feeding on azaleasyou can use natural preparations of tansy. Infected azaleas are watered and sprayed with such preparations.
In the case oflarge numbers of swollen swellings on azaleaschemical protection may be necessary. For spraying azaleas, you can use Mospilan 20 SP (4 g of the agent is dissolved in 10 liters of water). It should be remembered that the Edema feeds at night, so the treatment should be carried out late in the evening. Spraying must be repeated after 7 days.
2. Azalea aphid(Illionoia azaleae)
Azalea bushes are also often attacked by azalea aphids. These insectsappear on azalea bushes in early June, feeding in colonies on the lower side of the leaveson the tips of the shoots.During feeding, the insects also excrete honey dew, which covers the leaves and becomes a nutrient medium for the fungi. As a result of aphid feedingazalea leaves are deformed and flower buds are damaged
Fighting the azalea aphidshould start when you notice the first specimens on the bushes. For this purpose, protective spray preparations (ready-to-use) are used, such as Karate Spray, Biochron spray for aphids, Agricover Spray or Emulpar Spray. The last 3 are natural preparations, harmless to the environment. If we want to spray a larger number of bushes, it is worth reaching for a concentrate that can be dissolved in water. If it is to be ecological, let's choose Emulpar 940 EC, and if we want to have high spraying efficiency and are not afraid to use chemicals, it is worth reaching for e.g. Karate Gold or Mospilan 20 SP.
MSc Eng. Agnieszka Lach
