Pear rust can quickly make a pear tree look pretty sick because it causes conspicuous spots on the leaves. Here you will learn how to recognize pear rust and when and how it is necessary to combat it.
Table of Contents
Pear rust – the pathogen
Pear rust is a fungal disease. The fungus is called Gymnosporangium sabinae and does what all fungi do: it settles on soil or a host plant and reproduces through its spores and by spreading via its mycelium.
Most fungi support plants and soil life, some live on plants and, if necessary, even destroy them.
The “case of doubt” is an old plant, a sick plant or a weakened plant in a disturbed environment, so the parasites also have a corrective function. In an ecologically healthy, natural environment, the host plant and fungus often coexist peacefully for a long time without harming each other.
Pear rust is one of these parasitic fungi, but there are around 10,000 other fungal parasites that live in plants. In view of these ratios, an infestation with pear rust is certainly not a reason to panic.
Recognize pear grating
If spores of the rust fungus have settled on your pear tree, it will show the first visible symptoms of infestation around the time of flowering. The fungus can be recognized by the small yellow or orange spots on the upper side of the leaves. These then increase in size over the summer, and in the fall an infested pear tree often looks more orange or red than green.
In autumn, the second stage of the infestation can also be seen on the underside of the leaves. This is where the fungus builds spore deposits, growths that look a bit like warts (but warts are caused by viruses, not fungi). These spore deposits are surrounded by a skin that gradually tears open to form a latticework. The pear lattice grate got its name from this latticework.
Other diseases that cause spotting on the leaves are pear pox mites, hawthorn rust and fire blight, you would need to differentiate here.
Damage from the pear grating
As I said, there are more than 10,000 parasitic fungi, and if the pear rust on your pear tree causes a few spots on the leaves, that’s no reason to rush to the nearest chemical plant to upgrade. Rather, you should keep a close eye on the pear rust and take possible measures in a considered manner.
Under certain circumstances, pear grating can cause damage particularly quickly:
- You have just planted young pear trees, young plants can quickly and seriously damage many things, including the pear grate
- Old pear trees show a very massive infestation with pear rust, which weakens growth.
- A weakening of the growth can be expected if more than 40% or (at first glance) around half of the leaves are affected.
- A fairly severe infestation is when you see more than three spots on each of these leaves.
- It is also an indicator of a fairly severe infestation if the pear tree sheds its leaves prematurely.
- If such a heavy infestation is not contained for several years, the trees will eventually become weakened by the fungus.
- Then there is a risk of yield losses, at some point entire branches could even die off.
The other way round, however, this means that you can observe a small infestation of pear rust quite calmly, very often the pear rust does not damage the tree so badly that you have to take any control measures. A sign of a weak infection is z. B. that the pear does not shed its leaves prematurely, as long as this does not happen, you can safely devote yourself to studying this article.
Pear grating – when to act
You only need to read this article a little faster if pear rust has been occurring continuously and very severely for several years, with several spots per leaf and premature leaf fall. You should now think about what measures you plan to take to combat pear rust by next spring. Putting together the right measures is not always easy.
In this selection of measures, do not let the horror reports on the Internet unsettle you. When pear rust appears like a terrifying epidemic in a certain area, there is always a reason for it. You just have to find out why, and this article will show you how. In no case do you have to rush. The pear rust is a host-changing fungus. The result, however, is that the pear tree gets rid of the pear grating every autumn when the leaves are dropped.
Therefore, it is not primarily about treating the pear tree, but rather combining a whole series of measures that keep the pear rust in check. As you will also learn below, sensible measures against pear rust are almost never limited to a single property, which is why the plant protection offices of many communities offer advice on pear rust. Of course, they will also help you to decide when you should do something.
How is pear rust transmitted?
Although it would be understandable if you only commented on this heading that you didn’t care at all and you just wanted to get rid of the pear grating, you should be interested in the transfer of the pear grating. Pear rust is not a disease that only affects pear trees, but other plants are also involved. This fact also affects the prevention and control of pear rust.
The pear rust is one of the rust fungi that can only survive if there is a change of host. So the pear is not enough for him, juniper is also involved. The pear grating also needs it to continue to exist in a certain area. With a juniper in comfortable proximity, the pear trellis starts an efficient circle of life. It spends the winter in the juniper and forms spores there. He sends them to the young leaves of the pear tree in spring. There it forms spores again in autumn, which then switch back to the juniper, and so on. Under favorable conditions, the mushroom gets a little more powerful with each turn.
The pears get rid of the fungus again when the leaves drop; here (in the case of weak to medium infestation) it only sits on the leaves. The affected junipers remain permanently infected, but the pear rust does not like every juniper species. For example, the fungus in our native heather juniper Juniperus communis doesn’t stand a chance. The North American creeping juniper (Juniperus horizontalis) and the scaly juniper (Juniperus squamata) from Central and East Asia have not yet been attacked by Gymnosporangium sabinae.
The rust fungus, on the other hand, likes to settle in an imported juniper species that has been planted in German gardens, cemeteries and public parks for a long time: the sallow tree, Juniperus sabina. Other juniper species, which are not native to us and therefore do not always have much to counter our pests, are attacked by pear rust. These are the Chinese juniper Juniperus chinensis, the Pfitzer juniper and the Virginian juniper Juniperus virginiana. The susceptibility to pear rust varies in these junipers depending on the cultivar.
As a result of the containment of pear rust, these ornamental junipers are not planted quite as often, but since they are easy to care for and inexpensive, they still appear in gardens and public green spaces. Before fighting the pear rust on a pear, there is a search for the affected juniper (at least if the measures on the pear are supposed to make any sense):
Damage to the juniper
However, it may take you a while to find the diseased junipers that reinfect your pear tree every year. The fungus spores are spread several hundred meters by the wind, so you have to search quite a large area around your garden for infested junipers. Of course, we don’t want to seriously suggest that to you, such extensive “juniper considerations” are more a matter of community measures of an entire settlement or community if a pear rust infestation threatens to get out of hand. A normal pear rust infestation is more about investigating your own garden and the gardens around you.
You can tell whether a juniper is infected from around mid-April. The branches of the juniper then thicken, wart-like structures appear on the affected areas, which first carry brown and later yellow spore beds. The spore deposits have a jelly-like sheen when they are wet and grow to a size of one to two centimetres. When fresh and moist, the spore stores on the juniper look a bit like a kind of gathering of small, brown worms, or as if a bad-tempered do-it-yourselfer is disposing of the remains of a light brown silicone sealant from his cartridge syringe in the juniper.
In the case of juniper, the spores are located on the twigs. In the case of a severe infestation, entire sections can be covered by them, which then turn almost completely orange. The affected branches can even die off. Depending on the other condition of the juniper, however, it takes quite a long time before the pear grating really does damage to the juniper, and the first branches of the juniper plants usually only die after many years.
Combat pear rust on juniper
If juniper is the permanent host of pear rust and the pears are reinfected every year, the first control measure would logically be to treat the juniper. In fact, if you have juniper in your own garden, this is also where you should start to tackle pear rust. Not with the fungicide available for pear rust since 2010, that doesn’t work on juniper and is therefore not approved for use on juniper.
Only “brute force” helps here. If you discover the infestation very quickly, this can perhaps be limited to generously cutting away the infested juniper twigs. In any case, you must then cut back into the healthy wood, and quite deeply. Fungi form invisible mycelium. If the thorough pruning of the juniper was unsuccessful or the infestation is too severe anyway to be able to achieve something by cutting away individual branches, you will eventually have to decide on a juniper growing very close to the pear: pear or juniper. One of the two has to go. This is the only option if you want to finally get rid of the pear grate.
Experience has shown that if the infested juniper that is to be dealt with is not in your garden, it will be more than difficult. It’s still worth a try: every neighbor who replaces his rust-prone, heavily infested juniper with a native juniper in an area badly hit by pear rust significantly reduces the risk of infestation for the surrounding pear trees. There’s also a lot more to do with the native juniper, the only species with edible berries. The berries can be used as a spice or to make delicious juniper schnapps. Berries, needles, shoot tips, wood and roots are considered remedies in over 40 different applications.
Susceptible and less susceptible pear varieties
If you want to plant a new pear tree in an area where pear rust occasionally occurs, choosing a variety can do a little to combat pear rust. There are a number of pear varieties that are said to be quite susceptible to pear rust, e.g. e.g.:
- “Alexander Lukas”
- “Good Gray”
- “Club Dean”
- „Williams Christ“
You should perhaps not necessarily choose these pear varieties.
The following varieties are considered less susceptible to pear rust:
- “Colorful July”
- “Double Phillips”
- “Countess of Paris”
- “Good Louise”
But the fact remains: In principle, all types of pears can be attacked, even the currently popular Japanese Nashi pears, which are actually considered to be resistant to fungal diseases and pest infestation. So if there is a very high incidence of pear rust in your area, you should think twice about planting a pear.
Prevention and natural control
You can only prevent the infestation of the pear with pear rust if you identify the diseased junipers in the area, which is difficult if not impossible if these junipers are not in your garden or in your neighbor’s.
If you do not know where the pear rust “flies in” from, you can only try to strengthen your pears against the fungal attack. This includes maintaining or creating a healthy garden soil with a rich soil life and using natural organic fertilizers that do not adversely affect the soil around the pear tree. In the vicinity of a pear tree affected by pear rust, it is recommended to fertilize only a little nitrogen, as it is said to make the pear trees more susceptible to the fungal attack. The heavily consuming vegetables should therefore be given a place in the garden that is very far away from the pear tree.
This also includes the use of a plant strengthener for the pear tree. You can produce such a plant strengthener yourself, horsetail extract and algae extract should give the pear tree z. B. help. But there are also commercially available plant strengtheners.
However, this also means that you do not further weaken your pear tree by cutting it before it sprout. Prune affected pear trees in summer when they have more vigor and better ability to close their wounds.
Mechanical control of pear rust
If the pressure of infestation has been somewhat reduced by constant reinfection by pruning or removing a few junipers, you can actively free your pear tree from pear rust. You then check your pear tree regularly for infestation with the pear grating and remove all infested leaves immediately.
are a number of things you can do to prevent pear rust, but always on the condition that the damaging juniper grows less. Therefore, the only approved plant protection product that has been available against pear rust for several years will not be discussed here. If the junipers are gone you can get the pear tree healthy without fungicide, if they are still there it will get sick again anyway. Under these conditions, it would be more than unwise to apply a pesticide every year that is supposed to induce resistance when used several times. In addition, it never breaks down in water and according to a study by PAN (International Pesticide Action Network) it is a highly dangerous pesticide overall.