If an apple tree (Malus domestica) has rotting apples, this can spread to the entire fruit stand and neighboring fruit trees. Now find out what to do about it.

In a nutshell

  • multiple triggers for rotten apples on the tree possible
  • Fruit rot mostly caused by fungi
  • quick action required

Identify rotting apples

Apples go through various changes during their ripening development and can show different defects. These range from squishy to differences in size and color. Not every discoloration or softer consistency immediately suggests rot. This can be recognized by very typical features:

  • brown patches that increase in size over time
  • mostly fruit skin injury visible
  • first soft, later mushy flesh under brown areas
  • musty smell
  • Brown discolorations in the later course mainly covered with grey-yellow fungal spores
  • some dry up on the tree; others fall off
  • in the final stage black leathery skin (so-called fruit mummies)

Monilia rot

In most cases, rotting apples are due to the monilia rot. This is a fungal infection that can spread rapidly and also spread to nearby plants/fruit trees. Monilia fructigena is the name of the fungal pathogen. This prefers moist environments and affects numerous apple tree varieties. If the fungus is not controlled, it can lead to a problem that lasts for years and, as a result, to ever smaller crop yields. In the worst case, it destroys the entire fruit stock.

What to do?

When the first rotting apples form on the Malus domestica, you need to act quickly. Depending on the trigger, several measures are required, whereby the immediate measure should be carried out in any case.

immediate action

  • Immediately remove all rotten and decayed apples on the tree and on the ground
  • Cut off branches with fungal spores generously
  • fertilize with plant strengthener for more resistance

Tip: Dispose of infested fruit and plant parts in a locked place, such as in the organic bin. If you leave it or dispose of it in the compost, fungal spores will spread further in the garden.

trigger and counteract

There are several possible triggers for rotting apples and monilia rot.

1. Pests

The trigger for apple rot is often a pest infestation. This provides the necessary entry points on the fruit so that fungal pathogens can get inside. In order to let rot-free apples ripen healthily, it is necessary to identify and control the pests accordingly. The following two types of parasites are most common:

  • Apple spider moth (Yponomeuta malinellus): greyish, light beige moth with typical butterfly wings; transparent or yellow larvae with black dots; Control by collecting or spraying soft soap solution
  • Codling moth (Cydia pomonella): brown moth, one centimeter long; yellow-whitish larvae on apples; collect or spray the apple tree with wormwood manure
Apple spider moth (Yponomeuta malinellus)

2. Dense foliage

Because monilia rot attracts moist areas to an apple tree, dense foliage can create optimal conditions for it. After rain and/or high humidity, it prevents rapid drying because little or no air can get through the branches. Therefore, a clearing cut should always be made with rotting apples. If fruit rot is present, the spread can be curbed at least in terms of speed by clearing it out.

3. Dense fruit growth:

The same as described under “dense foliage” also applies to fruit growth that is too dense. If the apples are too close together so that they cannot dry completely through air circulation, the fungus feels comfortable. Therefore, thinning the fruit crop is always recommended to avoid spreading and as a preventative measure. How to proceed:

  • Break out smaller apples from a bunch
  • remove damaged fruit
  • Cut off fruit that is less than three centimeters from the fruit next to it

Prevent re-spreading

So that rotting apples are not an issue in the following year, appropriate preventive measures must be taken:

  • collect all fruit mummies in autumn/late autumn (otherwise ensure renewed spread in spring)
  • Dispose of fallen fruit
  • remove fallen leaves with mold spores
  • Check neighboring trees for possible fungal infestation
fruit mummies

Tip: If you use garden tools, you should definitely ensure that they are disinfected afterwards. Without these, the tool should not be used for work on other plants, as pathogens are in them and can be transmitted.

frequently asked Questions

Can powdery mildew also be responsible for rotting apples?

Yes. On the other hand, you can take the same measures as described in the guide. Contrary to this information, hosing down with soapy water also helps. Spraying is difficult on a tall, wide apple tree. For smaller specimens, soapy water is an effective measure against apple powdery mildew and the “Podosphaera leucotricha” fungus. Especially the buds are to be sprayed. That's where the mushrooms overwinter.

What role does location play in relation to apple rot?

Basically, the location determines healthy growth and susceptibility to diseases and pests. What the optimal location looks like depends on the respective apple variety. Humidity, cool and waterlogged locations make most varieties susceptible to apple rot. Pay attention to the recommendations for the ideal location here.

Are there apple trees that are particularly susceptible to the monilia rot?

Yes. Especially among the old apple varieties are those that are susceptible to typical apple tree diseases. Meadow apple is an example of a disease-resistant variety that is also resilient to pests.

Category:

Garden plants