Sifting is a common fungus on cherry, plum, almond and other fruit trees of the genus “Prunus”. It causes unique holes in the leaves, similar to the effects of shotgun pellets. This is where its other name comes from; it is also known as perdigonada. I’ll tell you how to control it next.
So I found, this morning, several of the cherry trees in the garden. It must be said that it is not insects that are responsible, nor slugs or snails, although it may seem so.
It is a fungus; incredible but true. Screening is called, also known as shot (Stigmina carpophila), which basically affects fruit trees of the genus “Prunus” (cherry, almond and plum trees, among others).
This fungus can damage the fruit, causing it to fall or deform. Also the flowers and buds are often affected. However, what makes it unmistakable is its manifestation in the leaves. At the beginning there are small reddish-brown and circular spots, distributed all over the surface, which soon dry up.
The final result will be the characteristic holes, which you can see in the image (perforations similar to a shotgun pellet). Note that, in some of them, the necrotic tissue has not yet come off; it can be seen hanging and about to fall out.
If, in addition to the leaf blade, it would attack the leaf petiole, it would also achieve defoliation.
If you follow me regularly, you will know this: well nourished trees are less susceptible to attack by pests and diseases. Make sure that they do not lack the necessary minerals, as well as adequate watering (especially during the first few years).
Previous attacks by fungi, insects or other parasites can also weaken them and encourage subsequent infections.
Screening usually works in the spring and autumn, as it requires moisture for propagation. However, it is resistant to the cold and remains active during the winter. If the conditions are right, it can damage dormant buds.
Therefore, fallen leaves and pruning remains should be removed properly. It would also be a good idea to apply a fungicide preventively, in case of recurrent infections.
Treatment of screening
To combat this fungus in the garden, you can apply a copper-based fungicide: Copper oxychloride 50%, cuprous oxide 50%, tribasic copper sulphate 19% or copper oxychloride 70%. Difenoconazole and Dodine are also allowed in domestic outdoor gardening. There are others like Captan or Mancozeb but, as far as I know, here in Spain they are reserved for professional agricultural use.
If you want to harvest the cherries, almonds, plums… you have to know that the data sheets of these products do not recommend their use from the flowering to the harvesting of the fruit. You can treat without problems in autumn, but to prevent spring affections you should spray the branches better during the winter.
There are other limits: a maximum of three applications is recommended, with at least two weeks’ rest between each one.
Below is the indicated dosage. I leave everything well chewed…