Plant diseases& TreatmentsUnder different conditions, different diseases can spread among plants in the garden. A distinction is made between fungal, bacterial and viral diseases. The earlier diseases can be detected and diagnosed, the more effectively they can be treated. We show you which ones are particularly common, how to recognize them and with which simple, biological tricks you can get rid of them again.
For the selection of health-promoting measures, the correct diagnosis based on the symptoms of pests is crucial. It can be easy to confuse plant diseases or sometimes the symptoms have abiotic causes such as z.B. Lack of nutrients, drought, waterlogging or soil compaction.
Abiotic damage is indicated, for example, when all parts of the plant are evenly affected and the damage pattern looks very regular. If only individual plant parts are affected, it is probably a pathogen, you can be sure if spore lawns of fungi or the like are visible.
Powdery mildew Is a fungal disease that is particularly common in home gardens. It mainly affects cucumbers, carrots, lettuce and ornamental plants such as roses.
In the case of a disease, the outer parts of the plant are covered by a fungus. This white, cotton-wool-like coating occurs mainly on the upper side of the leaves and can be easily wiped off. If the plant is not treated, the leaves may dry out and brown discoloration may appear.
Basically powdery mildew is favored by dry conditions. This also means that it could be treated with water. However, higher humidity favors many other types of fungi. Therefore, it is better to do without it and follow other tips.
Since powdery mildew does not tolerate fluctuations in the acid balance, it can be controlled with slightly acidic or alkaline substances, such as baking powder, fatty acids or whey.
In addition, beneficial insects such as yellow ladybugs or a special beneficial fungus called Ampelomyces quisqualis help keep downy mildew in check because they graze the spore turf.
Differences powdery mildew and downy mildew
The disease should not be confused with downy mildew. As the name suggests, this is a visually similar disease, but it is caused by completely different pathogens and must be treated differently. Downy mildew loves moisture, causes bright spots bordered by the leaf veins, and only in the final stage forms the white down on the leaves.
While powdery mildew lies on the leaf surface and anchors only individual spores inside the plant, downy mildew nests completely in the leaf tie. The white fungal coating from downy mildew is usually on the underside of the leaf and is also not easily wiped away.
When Downy mildew on a plant usually develops first bright yellow spots on the leaves. An important tip for identifying downy mildew: in normal view, the spots are lighter than the healthy tie, but in backlight they appear darker. In the case of downy mildew, too, a white tie, which emerges from small crevices in the plant. However, this only happens on the underside of leaf and only when the plant is already very badly infested.
Powdery mildew (Photo: Maja Dumat / flickr.com – CC BY 2.0 )
Since downy mildew prefers moisture, it helps to keep the plant's leaves dry, d.h. better to water in the morning and only under the plant and not on it. diseased parts of the plant should be removed.
Another common fungal disease is gray mold, which mainly affects weakened plants.. The gray mold has no preference for certain plants, but pounces on all plant ties that are weak or already dead.
Parts of the plant affected by gray mold should be removed muddy and get a grayish fur. Leaves, blossoms, stems and fruit can all be affected. Whereas blossoms are particularly often covered with the fungal rust, because here the plant's own defense mechanism is weakest.
Since gray mold usually only affects weakened plants, preventive care should be taken to ensure the right location, a good supply of nutrients and a Sufficient strengthening attention should be paid. But be careful: too much fertilizer can attack the immune system of the plant. Provide a good base for the gray mold. The fungus also loves moisture, which is why its spread is so rapid by keeping the plants dry can be prevented.
Rust fungi are characterized, as the name suggests, by rust-colored, variegated spots on the leaves. This particularly noticeable fungal disease does not kill the cells, so infected plants are weakened but do not die. However, secondary diseases can occur.
Many different plants can be affected, with the various rust fungi concentrating on certain plant groups. For example, there is the rose rust, pear rust or even a grain rust. Grasses, pears or vegetables are particularly often attacked. Some species also change their host in the course of the seasons. Pear rust overwinters, for example, on juniper plants. then flies to the pear trees in the spring. Leaves. These mostly round spots are formed by the fungal spores. Located on both upper and lower leaf surfaces. These mostly round spots are formed by the fungal spores. Are found on both the top and bottom of leaves.
Pear lattice rust
Since rust fungi often fly only at a certain time, it is possible to treat them by Strengthening of the affected plants the highest risk during these periods of time. It can also help preventively do not place plants next to each other on which the rust fungus nests for each other plant. Here one should inform oneself exactly whether the spores move from host to host. Using the example of pear lattice rust, pears should not be planted next to juniper plants. If an infestation does occur, it is at least not fatal for the plant.
Who has fruit trees in the garden, knows certainly also scab. In addition to apples, it also attacks pears, cherries and peaches. The apple scab overwinters on the tree. Nests on young shoots in spring. The weather is decisive for the time of the disease outbreak. Conditions must be moist and warm (above 16°C), then apple scab spreads.
This happens in two steps. In the initial infestation, the fungus nests in the leaf and spreads there. After a few days, the fungal spores are formed first, which are distributed by rain and wind. Here's how the disease spreads rapidly. Infects surrounding parts of the tree.
Apple scab shows through humpy, black spots on the leaves. With time the whole leaf discolored brown, Withers and falls off. Depending on the time of infestation, the scab also shows its traces on the fruit. Early damage is caused by cracked, corked apples. The scarred areas on the fruit are completely harmless to humans, but the storability of the apples is limited.
There is tolerant varieties, which are less susceptible to apple scab. Locations protected from wind and damp should be avoided. If a tree is already infested, at the latest in autumn the Attacked leaves should be removed. A professional pruning can also help to promote the drying of the plant. As a home remedy can also Baking soda, willow bark and slaked lime help.
Related to downy mildew, late blight is also a troublesome fungal disease in domestic gardens. Mostly nightshade plants are attacked, i.e. tomatoes, potatoes and petunias.
At the beginning of the disease process brown, irregular spots on the leaves. These can spread to the stalks. Later you see the classic white-gray mold, which covers the underside of the leaves like a carpet. Due to the close relationship can also the herb-. brown rot to be treated like downy mildew. That means: keep dry. So don't water the leaves from above and remove plant parts that are hanging on the damp ground. If the reaction is quick, it can also help to quickly take away the first, infested leaves. When pruning leaves and shoots, hygiene must be observed so that the disease is not transferred to healthy plants with a knife or scissors.
Leaf spot diseases
Leaf spot diseases can be classified less by pathogen than by visual appearance. These are different fungal diseases, all of which cause a specific symptom: Spots on the leaves.
As mentioned earlier, leaf spot disease is manifested by Spots on the leaves. Mostly around or pull concentric circles around the infection site. Due to the great variety of pathogens, even irregular spots The fungal infections are similar to downy mildew in that they are limited by the leaf veins. However, these are in the Backlight brighter than the healthy tie (for comparison: in downy mildew, the spots are darker against the light).
Prevent is the key to leaf spot diseases. Since weakened plants are preferentially attacked, care should be taken to have vital plants. So choose the right location, do not let the plants grow too densely so that they dry out quickly, make sure that the soil is good and revitalized, check the PH value and do not over-fertilize.
Bacteria penetrate the plants through cracks and wounds, which is why the risk of infection is generally lower in healthy and undamaged plants. If the greenery in the garden is well strengthened, there are also plants' own defense mechanisms that can stop an infection even after it has occurred. However, if a plant is already weakened, bacteria have an easy time of it. They multiply rapidly and produce plant toxins that can ultimately lead to death.
In principle, however, bacterial diseases do not occur as frequently as, for example, fungal diseases.
The plant toxins of the bacterial diseases often act by blocking the conduits for nutrient transport. This causes the tie to die. This leads to Leaf spot, root rot or wilting. It can be v.a. with groves also to Growths that look similar to a tumor (for comparison. A very common disease is also the Wet rot. Recognizable by dripping, stinking mud, the slime of bacteria. Bacteria are transported via such liquids to infect the next plants, which are therefore highly infectious.
Due to the high diversity of bacterial diseases, there are also many different clinical pictures.
As bacteria enter through injuries and openings in the surface, these should be largely avoided. If cuts or the like must be added, disinfection of the tool with alcohol or vinegar is indispensable. Acutely there are for bacterial diseases no means of control. Only preventive measures can be taken, for example by immune strengthening.
Unlike most fungal and bacterial diseases, viruses show up externally as conspicuous patterns on the surface which can sometimes even be quite pretty. Plant breeding also uses this effect to produce so-called varieties, which are sold as ornamental plants. These plants are then actually sick. Weaker than healthy individuals.
Basically viruses want to spread in the first place. However, they cannot do this themselves, but do so via infested plant parts or they use insects as carriers. Since they need hosts to spread, their primary goal is not to kill them, but only to weaken them. Nevertheless, there are some factors that can contribute to the fact that viral diseases plants also kill.
Viruses often move through the tie of the plant, recognizable by yellow leaves and subsequent dying of the whole plant. A typical picture of a virus disease in several plants in a small area is a spreading in spots the symptoms. Nest-like so plants are infested around a hearth.
Affected plants should be removed, to prevent spreading. Viral diseases can subside on their own, there are also no remedy for plants at all. One can only Replace affected soil, dispose of plant parts and seeds, and disinfect pots, poles, and tools, respectively preventive, pay attention to the plant health. Longer crop rotations with breaks for the virus-susceptible plants also help.
Fungal diseases in lawns
Lawn diseases are usually caused by improper care. There are various types of fungi that can attack the lawn.
With the Rusty aphid z.B. enters red mycelium from the tips of grasses from. In order to prevent the disease, it is important to water correctly – in this case rarely but extensively.
snow mold usually develops after a long period of snow cover in the spring. The disease is characterized by slimy dieback of the grasses and a typical, moldy coating from. In case of an infestation the affected areas should be dried. Then removed with a rake.
Dollar spots are round, dead spots in the size of a coin on the lawn. The infested areas must be scraped out and replanted. Aerating the soil can also provide relief.
Remaining in contact?
Probably the best known pests in the garden are the aphids. There are different genera, each attacking different plants. There are also so-called host-changing species that settle on certain plants at certain times of the year. In larger groups they suck on the infested plant to obtain mainly protein. They secrete sugary plant sap (honeydew) in the process.
By shedding the sticky plant sap, they create on and around the infested area many small, sticky spots. Also skinned sheaths the aphids can stick in the sap. In the proximity of such places one finds mostly also the animals. They usually sit on the leaf veins. Suck with their proboscises the sap.
However, there are also root aphids, which belong to the aphids but – as the name suggests – attach themselves to the roots of the plants.
Aphids can mechanically, with biocides or by Beneficial insects are combated. Mechanically it is enough to attack the plants with a strong jet to be showered off, simply strip the aphids or remove the affected areas.
As a biocide is rapeseed oil or potash soap effectively. Simply spray the affected plant with it.
Because of their low position on the insect food chain, there are a number of beneficial insects that feed on aphids: Ladybugs eat many hundreds of aphids, both as larvae and as adult beetles. Also Ground beetles, spiders or birds like to eat aphids. Many other beneficial insects do this only as larvae, for example lacewing, hoverfly and gall midge larvae. Still others are parasites, such as Parasitic wasps, which also kill the aphids. Beneficial insects, however, appear slightly delayed to the aphids, so a little patience is needed. However, after about two weeks, a beneficial effect should be visible.
Butterflies are the epitome of biodiversity in the garden. Especially due to their often magnificent wings are very popular. But for butterflies to enliven the garden, they must first go through their natural progression. This also includes the stage of the caterpillar.
Caterpillars have to eat a lot to be able to turn into a butterfly later on. In gardens, they can sometimes attack cultivated plants that have been planted with great effort. They usually cause feeding patterns such as boreholes or leaf miners on flowers, leaves, fruits or roots.
If Feeding images If slugs are discovered on plants, the culprit is usually not far away. Once you have found it, you still have to identify it. There is a risk of confusion with the caterpillars of the leaf wasps. The legless body segments (ring-like sections) are an accurate distinguishing feature. Butterfly caterpillars have at least two (or more) body segments without legs, whereas leaf wasp caterpillars always have only a single leg-free segment on their body.
Butterfly caterpillars are a favorite food of many Beneficial care. For example, by attracting birds such as tits, a natural enemy can be brought into play. Caterpillar flies, parasitic wasps, ants and spiders can also contain a caterpillar infestation.
Mechanical are also Nets a good option. Vegetables, in particular, can be well covered with close-meshed nets (e.g.B. old fly screen).
Thyme keeps caterpillars away in a completely natural way.
The caterpillar of the Cabbage white butterfly affects mainly, as the name suggests, cabbage. In the case of cabbage plants in the garden, one should therefore look out for eggs at an early stage and remove them.
Eggs of the cabbage white butterfly
The larvae of the Codling moth infest mainly apple fruits. In the first generation, they cause unripe apples to die; only the second generation of the pest is found as larvae in ripe fruit. They are then recognized as pink worms in the core, surrounded by red feces. Beneficial insects such as chickens, nematodes or special granulosis viruses are suitable for controlling the disease. Also pheromone traps can help to divert the moths of codling moth to their flight times.
A particularly dreaded caterpillar in the garden is the Box elder moth. It is green-black, about 5cm long and causes enormous damage to boxwood plants. Remedy is provided mainly by natural enemies such as birds. A nesting box in the immediate vicinity would be ideal as a preventive measure. In acute infestations, the plant can be treated with a high-prere cleaner or special nematodes can be used.
Caterpillars of the boxwood borer
Slugs and snails (Spanish snails and genetically modified slugs)
Snails are important members of our sensitive ecosystem. Among slugs, however, there are two species that have fallen out of favor with gardeners: The path slugs and the field slugs.
slugs can be recognized by a Breathing hole on the back plate near the head, while field slugs have this more at the rear end of the dorsal shield. With the field slugs there are however also useful representatives, why a blanket fight is not recommended. There are even predatory snails like the tiger snail, which also eats other snails and carrion. Housing snails are usually not a problem anyway. Should not be fought under any circumstances.
Slug with breathing hole
Since there are not only annoying but also useful slugs, slug pellets should be avoided in the fight against them. The occurrence of slugs cannot be completely prevented either, control is more about learning how to deal with them and protecting your own plants.
Preventive it helps, watering only in the morning, so that snails do not find too humid conditions at night.
Since snails like to nest their eggs in soil crevices, try to be careful when tilling the soil. If nests with 2-3mm large, white Snail eggs are found, it helps to stop them immediately remove. The nests are often made in damp and dark places under wood, under flower pots or other protective things.
Mechanically, snails also helpfences, copper bands or coarse, dry materials, which make it difficult for the snails to access the plants. Snails captured alive or dead. Can then be disposed of or moved. However, these lure traps should only be used within a segregated area (z.B. inside a snail fence) because otherwise more snails might be attracted.
Beneficial insects include Running ducks or chickens against slugs to. More info on snails can be found here: Fighting snails
Soil pests (grubs, mole crickets)
Not only on the plants themselves, but also in the soil, there are countless insects that can harm the garden. Of course, our sensitive ecosystem is dependent on all these creatures and each has its role in the overall system. Some of these feed on the roots of our vegetable or ornamental plants.
Mostly larvae of larger beetles like rhinoceros beetle or cockchafer. However, there are also useful larvae that cavort in the compost and feed there on dead plant material. So find z.B. If there are rosebug grubs in the compost, this is a good sign.
Grubs are the larvae of all leaf horn beetles, including May and June beetles, garden chafer beetles and rose chafer beetles. It is recognized by its white, fleshy body with rather long legs and the typical curved sickle shape. Depending on the type of larva, white grubs can infest various plants as well as the lawn. As soon as they are found among living plants, it can be amed that they are root-eating larvae, if they are found in compost, they feed on dead plant parts. The larvae of mole crickets are basically beneficial insects. Feed on other soil pests. However, it still happens that the larvae do not find enough to eat and therefore go for living roots. The adult animal can be recognized by the conspicuous large neck shield, their digging scoops and the yellow-brown coloration. Although special surgical techniques can be used against the infestation of these larvae Nematodes used, the mole crickets are, however, highly endangered. Therefore, only in absolute emergencies should anything at all be done about them.
Adult mole cricket
If you grow fruit in your garden, sooner or later you will have to deal with pests in the fruit. These are usually the larvae of a wide variety of insects. They feed on apple, cherry and co. and develop into mostly harmless flies or beetles.
Cherry fruit fly
A famous example is the cherry fruit fly. It lays a single egg in each of the unripe, yellow cherry fruits. The maggot, which hatches from the egg, then eats through the cherry until it drops fully ripe, allowing the insect to pupate in the soil. In the fruit one recognizes the maggot as small, white worm. This is absolutely harmless to humans, but still not very popular. Since egg-laying is attracted by the yellow color of unripe cherries, a Yellow boards to intercept the flies very successfully. Additional Attractants can increase the effect even more. Also beneficial like Chickens and running ducks can help against cherry fruit flies, because they pick up the maggots from the ground.
Cherry vinegar fly
An imported fruit pest is the cherry vinegar fly. Also specialized on cherry trees, it has only recently been found in Europe. Visually similar to fruit flies, Red eyes and round, amber-colored bodies, pounce on healthy fruit. They cut the fruit with a saw at the hind end and lay their eggs inside. Mostly affected are berries, cherries or grapes. Since the pest has only been known in Austria for a short time, only a few control methods are known. It is known that the cherry vinegar fly has no Heat tolerates, but remains active even at low temperatures.