Pear grate

Pear grate
Typical infestation pattern with pear grate
Systematics
Subdivision : Pucciniomycotina Class : Pucciniomycetes Order : Rust mushrooms (Pucciniales) Family : Pucciniaceae Genre : Gratings ( Gymnosporangium ) Type : Pear grate
Scientific name
Gymnosporangium fuscum
( Dicks. ) G. Winter

The pear grate ( Gymnosporangium fuscum syn. Gymnosporangium sabinae ) is a host-changing, phytopathogenic fungus that belongs to the order of the rust fungi (Uredinales) .

Life cycle

The pear grate permanently attacks various types of juniper and causes knotty thickening of the branches. The spore beds are visible as orange, rubber to gelatinous growths in spring. They swell and shrink depending on humidity and precipitation.

Spore bearing of the pear grate on the juniper

The basidiospores formed here are transferred to the leaves of pear trees every spring by the wind . The leaves are infected from the top of the leaves and are visible in the initial stages as orange-red spots that increase in size over time. Here the fungus forms summer spores, which in turn only infect the leaves of the pear trees. The striking color and the secreted “nectar” may help attract flies and wasps, which contribute to the spread of the spores. In this way and when the weather is favorable, the fungus can spread explosively within a short time. In late summer the fungus grows through the leaf and forms brownish, irregular oval growths up to 1.5 cm long on the underside of the leaf. The winter spores are formed in these Aecidiosporenlager . As the spores ripen, the growths tear open like a grid and release the dark brown winter spores, which can now infect juniper again.

In some years the infestation reaches almost all leaves of a tree. Fungal infestation can seriously damage young pear trees, while older plants are usually just another stress factor.

Preventive fight

As a host-changing fungus, the pear grate has to be combated in two places:

1. Treatment of the winter spore storage on juniper (mostly Chinese juniper ( Juniperus chinensis ) and Sead tree ( Juniperus sabina )):
   • Remove affected trees and bushes
   • Remove affected areas on trees and shrubs
   • Replace with robust (Juniperus hetzii) or better resistant species (e.g. Juniperus communis)
2. Treatment of the summer host pear (more rarely: quince):
   • Treatment of the pear with fungicides , for example myclobutanil (best in the spore flight phase, check infested juniper)

The spurs have a flight radius of 500 meters and can also be transported over longer distances in strong winds. Removing one of the two hosts, i.e. juniper or pear, is and will remain the most important measure. The use of plant strengtheners can minimize the extent of the infestation. Pear trees prone to infestation can be treated prophylactically as soon as the first flower buds become visible by spraying with triazole at two-week intervals. Experience has shown that treatment directly on the pear is usually only moderately effective. The leaves of infested pear trees can be composted without hesitation.

confusion

Orange (or orange-gray) thickenings of the leaves are also caused by the pox mite .

Pear grid on Juniperus pfitzeriana

Thickenings on the bark, orange to brown spore beds that become slimy over time, time of infestation: early May

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Picture gallery

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  Upper side of the leaf in July

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  Underside of leaf in July

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  Upper side of the leaf in October

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  Underside of leaf in October

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  Underside of leaf in October

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  Pear grate

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  Pear grid on Nashi pear

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  Aecidiosporenlager on the underside of the leaf

Web links

Commons : Pear Grate ( Gymnosporangium sabinae )  - Album with pictures, videos and audio files

• Information from the Bavarian State Agency for Agriculture
• Gardener's blog - pear grate
• Images of the spore beds on juniper

Individual evidence

1. ↑ Helmut Bichler: Fungal spores in flight from host to host. Der Tintling 99, issue 2/2016, pp. 70–71
2. ↑ ^{a b} Thomas Lohrer: Biology and control of the pear grid. (PDF; 303 kB) Bavarian State Institute for Forests and Forestry, accessed on May 1, 2013 . 
3. ↑ Jessica Theiss: Fighting pear rust: Prevention is the key. Burda Intermedia Publishing GmbH, accessed on August 9, 2014 . 
4. ↑ Iris Barthel: How dangerous is the pear grate? Naturschutzbund Deutschland (NABU) eV, accessed on August 9, 2014 .