Contents
Diseases of irises can be caused by viruses and fungal pathogens. To properly recognize the problem and cure the plant, you need to study the symptoms.
Signs and causes of iris disease
Iris is a beautiful flower that enters its decorative period in early summer. Healthy perennials delight the eye with colorful buds and vibrant green foliage. But sometimes the iris is affected by fungi and harmful insects. In such cases, the following symptoms appear:
- yellowing of leaves and stem;
- decay of the aboveground and underground parts of the plant;
- faded and weak flowering;
- brown and dark spots on leaves and petals.
The symptoms of iris diseases are very similar to each other.
There are quite a few diseases and pests of perennials. But they develop most often for the same reasons, namely:
- due to the presence of fungal spores or insect larvae already on the planting material;
- due to improper care, for example, against the background of severe drying or waterlogging of the soil;
- due to proximity to infected plants.
Common iris diseases and their control
Most often, perennials on the site wither from numerous fungi. Also, iris can be affected by viral diseases, the latter are of particular danger.
Rust
Iris often suffers from rust, which appears under the influence of the fungus Puccinia iridis. With the development of the disease, the leaves of the perennial are covered with yellow-brown and brown spots-pustules. Rust causes the green parts of the iris to dry out and die, sometimes the stems are involved in the process.
Rust disease affects iris at temperatures above 12 ° C
For the treatment of the disease, spraying with colloidal sulfur and Bordeaux mixture is used. Rust prevention consists in observing crop rotation and destroying plant debris in which fungal spores hibernate.
Mosaic
The Iris mosaic vims virus manifests itself in the form of a mesh pattern on the leaves, sometimes the green parts of the perennial are covered with yellow stripes. Under the influence of the disease, the iris slows down growth, begins to produce too short peduncles, faded or unnaturally colorful buds.
With mosaic disease, iris leaves are covered with yellow strokes.
The mosaic virus is dangerous because it cannot be treated, the perennial is simply destroyed. It is necessary to fight the disease prophylactically – buy material only in trusted stores, disinfect bulbs, seeds and rhizomes of iris before planting.
Wet rot (bacteriosis)
Wet root rot is caused by the bacteria Pseudomonas iridis or Erwinia aroidea. Bacteriosis leads to the fact that the underground part of the iris rots, and the rhizome is destroyed from the inside, turning into a soft white mass. Perennial leaves turn brown during the development of the disease, dry from the tips and easily fall out of the outlet.
In case of bacteriosis, the affected iris must be dug out of the ground and cut off the rotten part of the rhizome with a sterile knife. Then you can try to plant a perennial in a new place, if the underground part has not had time to completely collapse, it is still able to recover.
The disease develops most often with waterlogging and with a lack of calcium and phosphorus. Therefore, for prevention, it is important to feed the iris in a timely manner, do not flood it and regularly loosen the soil.
With bacteriosis, the iris begins to emit an unpleasant odor
Dry rot (fusarium)
The fungus Fusarium oxysporum also causes roots to rot. The disease affects the supply vessels, disrupts the vital processes of the perennial, as a result of which the iris turns yellow and dries. On the lower part of the rhizome, rotten areas and a gray-white coating first appear, and then the underground part dries up entirely.
With dry rot, the iris rhizome simply crumbles
The disease develops most often against the background of excess nitrogen in the soil, spores wake up at a temperature of 12 ° C in spring. At the first sign of fusarium, you can shed the earth with a solution of copper sulfate. If this does not help, then the diseased iris is eliminated.
Gray mold
The disease appears due to the fungus Botrytis cinerea and usually develops during the flowering period in rainy weather. Against the background of the disease, the stems and buds of the iris turn pale, then turn brown and become covered with a light grayish bloom.
Gray rot disease affects leaves and develops with high humidity.
In the early stages of the disease, Topsin-M, Kuproskat and Oksikhom are treated with drugs; copper solutions help well against gray rot. In order to prevent it, you need to monitor the soil moisture under the iris and observe moderation when fertilizing with nitrogen.
Botrytis
Botrytis disease develops under the influence of fungi Botrytis convoluta and Sclerotium rolfsii. It usually occurs in conditions of high humidity, affects perennials in early spring. The roots are covered with dry rot, sometimes mold can be seen on the bases of the leaves. Iris growth slows down, and by the summer the green parts simply die off.
Botrytis disease affects the lower parts of the iris leaves
The fight against the disease is carried out by spraying with Bordeaux mixture and Topaz – in early spring and then twice more until the end of flowering. If the measures did not help, then the irises are dug up and destroyed, and the soil is shed with formalin.
heterosporiosis
The disease heterosporiosis appears due to the fungi Heterosporium iridis and Mycosphaerella macrospora. In the middle of summer, grayish-brown spots with a yellow border appear on the leaves of the iris. The perennial begins to dry out and may die completely, especially if the fungus struck it at the height of the growing season.
The fight against heterosporiosis consists in the fact that all diseased leaves are removed, and the plant is sprayed with solutions of zinc and copper 3-4 times per season. To avoid illness, it is recommended to clean the flower bed of debris in time and not overfeed the iris with phosphorus and potassium.
Heterosporiasis affects iris first on old leaves
Ascochyta (leaf spot)
The disease develops under the influence of fungi from the genus Ascochyta, brown patches appear on the leaves of the iris – first at the edges, and then closer to the center of the plates. The greenery of the perennial dries up and falls off, and if you dig it out of the ground, then dark spots can also be seen on the rhizome.
At the first symptoms of the disease, Bordeaux liquid has a good effect – spraying is carried out three times at intervals of 2 weeks.
With ascochitosis, iris leaves begin to darken from the edges
Ascochitosis most often develops on iris in conditions of high humidity and swampy soil.
Alternaria
A fungus from the genus Alternaria infects iris from mid-spring to late summer. Against the background of the disease, the edges of the leaf plates begin to dry out, then all the green parts are covered with black bloom, turn profusely yellow and crumble.
Black spots on the iris are characteristic of Alternariosis
For the prevention of alternariosis, Bordeaux mixture is used, spraying is carried out before and after flowering. If the iris is already affected by the disease, then it is better to dig it up and burn it, since the spores quickly pass to other plants.
Iris pests and control measures
In addition to viruses and fungi, pests are a great danger to perennials. Some of them are easy to spot on the leaves, others affect the root system and can quickly kill the iris.
Onion Mite
A small round insect with a yellowish body does not exceed 1 mm in size and feeds on iris bulbs. It is active in early spring, and in summer it begins to multiply and can produce new colonies every 20 days.
The iris onion mite goes unnoticed for a long time, so it is better to deal with it prophylactically.
When infected with a tick, the scales of the iris bulbs dry out and wrinkle, the perennial stops growing. A weakened plant is often affected by secondary fungal diseases. Pest control is carried out with Actellik and Skor systemic insecticides, but it is better to soak the material in Antimite solution or sprinkle it with plenty of chalk before planting.
TRIPS
A small insect a little over 1,5 mm long settles on iris leaves, more precisely, in rosettes at their very base. Thrips feed on perennial juices, as a result of which it turns brown, dries and deforms. Infected iris does not always die, but blooms poorly or does not produce buds at all.
To get rid of the insect, you need to spray the plant with a solution of Karbofos twice with an interval of a week. From folk remedies, tobacco infusion helps well.
In hot dry weather, thrips give up to 9 new generations per season.
Onion nematode
The pest is a small white worm up to 1,5 mm long and breeds in iris bulbs in moist soil. Under the influence of the nematode, the perennial begins to grow poorly, its stems swell, and the underground part cracks and becomes loose. A distinct unpleasant odor begins to emanate from it.
It is very difficult to cure the onion nematode on iris – the pest manages to destroy the tuber
It is difficult to fight the nematode, it is extremely hardy and usually does not respond to treatment. Therefore, the affected irises are destroyed and focused on prevention – they disinfect the bulbs before planting, monitor the soil moisture and loosen the flower bed from time to time.
bean aphid
The insect looks like a small black-green or brown beetle that lives on the green parts of the iris. The pest has been active since mid-spring, under its influence the shoots of the perennial are deformed, and the leaf plates turn pale and curl. If you do not fight aphids, then in the fall they will lay their eggs at the roots, and in the spring the iris will attack a new generation of insects.
You can get rid of aphids with the help of Spark, Karate and Commander preparations, spraying is carried out 3-4 times per season. For prevention, attention should be paid to weeding and loosening, as well as feeding iris with potassium and phosphorus.
In hot weather, the bean aphid can produce up to 10 generations per summer.
iris fly
A black-and-gray fly with golden spots on its body feeds on iris buds in late spring, and then lays eggs, from which voracious larvae emerge. The pest causes severe damage to flowering and plant health. The fight against the fly is carried out with Aktara and Aktellik preparations three times per season.
The iris fly and its larvae can completely destroy the iris during the summer
From the iris fly, folk remedies help – tobacco dust, soapy water, ash.
wireworm
Black or striped beetles lay their larvae in an iris bed. Hatched pests feed on rhizomes and gnaw long passages in them; against the background of mechanical damage, fungal infections often develop. The affected perennial blooms worse and grows more slowly, and dies with a serious infection.
Wire beetle gnaws out rhizomes of iris
The fight against wireworm is carried out with insecticides Decis and Aktara, as well as a decoction of red hot pepper.
Bronze beetle
Large greenish beetles with a metallic sheen are active from the end of May until autumn. In the garden, they can even be useful because they participate in pollination. However, beetles feed on, including the roots and buds of plants, so they are dangerous for the iris. You can notice their presence by eating flowers.
The generally useful bronze is harmful to iris because it feeds on their leaves and flowers.
They get rid of the bronze beetle with the help of Kinmiks, you need to spray a flower bed with irises several times over the summer. The preventive effect brings a solution of wood ash.
Medvedki
A large garden pest is an insect up to 5 cm long with movable jaws and strong front claws. Medvedka lives in the soil and digs deep passages in it, damaging the rhizomes and bulbs of the iris.
Medvedka is difficult to destroy with insecticides, usually it is only driven to the surface of the earth and harvested by hand
It is not easy to fight a pest, therefore, even at the stage of planting, insecticides fall asleep in the holes for perennials. If the beetle nevertheless appeared on the site, then you can shed the soil with infusion of chicken manure or generously treat the iris with Karbofos.
Scoops
At the beginning of spring, dangerous caterpillars of the iris or winter cutworms often appear in flowerbeds with irises. Pests eat perennial stems at the very base, as a result of which flower stalks weaken, die off or break under gusts of wind. Also, caterpillars can eat rhizomes and bulbs, this will harm the iris in itself and provoke the development of fungal diseases.
Scoop caterpillars gnaw iris stems, because of which they simply break
You can get rid of the scoop by spraying with Karbofos. It is best to carry them out prophylactically, at the very beginning of spring and again a week later.
Preventive measures
Not all iris diseases are treatable, so it is easier to prevent their development. When caring for a flower bed, you must:
- control the level of humidity – flowers can not be poured;
- moderately apply fertilizers, with an excess of nitrogen, phosphorus or calcium, the neutrality of the soil is disturbed, fungi begin to multiply more actively in it;
- regularly loosen the soil and eliminate weeds;
- remove faded shoots in time;
- carry out preventive treatment of iris in the spring from diseases and pests;
- disinfect planting material at the stage of preparation – soaking in potassium permanganate or fungicidal agents significantly increases the endurance of plants.
Autumn treatment of iris from diseases should be carried out after pruning
In autumn, a flower bed with irises must be carefully dug up so that fungal spores and pests cannot survive the winter in the top layer of soil. Plant debris from the site is completely removed and burned, before the onset of cold weather, another treatment with fungicides is carried out.
Conclusion
Diseases of irises appear most often when the rules of care are violated. As part of the treatment, it is important not only to process perennials, but also to eliminate risk factors – to adjust the frequency of irrigation and soil composition.
