Plant diseases 5: Introduced diseasesGlobalization also has consequences for fruit growing. And quite unpleasant ones at that. Due to international trade and passenger traffic, not only pests foreign to the region, such as the cherry vinegar fly, have been introduced in recent decades, but also new plant diseases. These are usually particularly problematic because the local plants are at the mercy of the pathogens when suddenly confronted with them.
One such disease is "Marssonina leaf drop disease", for example. We would like to present it to you today.
Black spots – leaves gone
In Marssonina leaf drop disease, a fungus (Diplocarpon mali) causes black spots on the leaves or even on the fruit of apple trees. As the name suggests, it causes trees to lose their leaves prematurely. As a result, the tree lacks energy to form buds and fruit the following year.
The disease is manifested by dark, small spots on the top of the leaves, or small blisters filled with an oily liquid. There are also dark to olive green spots on the fruits.
Especially conducive to the spread of the disease are long periods of rain in July and August. So this year there are optimal conditions for it. And promptly there are already first signs in some places, among others in the opfelGarte.
Comparison: the row of trees on the left is not (yet) infested, on the right the columnar trees have already lost quite a bit of foliage.
This can be seen even better up close.
Since 2010 in Switzerland
This insidious disease was first detected in 2010 in an organic plant in eastern Switzerland. It was first described in Japan in 1907, then in Romania in 1960, in Brazil in 1986 and in Italy in 2001.
The increasing movement of goods and people distributes harmful organisms all over the world: "The FCA (Federal Customs Administration), together with the Federal Plant Protection Service (FPSD), which is jointly operated by the FOAG and the FOEN, seizes ever larger quantities of fruits, vegetables and flowers at the airports of Geneva and Zurich. Since the 1. From 1 January 2020, the import of plants and live plant parts from outside the EU will be prohibited unless an appropriate phytosanitary certificate is available," states the DETEC website.
And further: "The reason for the new import regulations is that plant diseases and pests are frequently introduced with plants", because "almost every year, a new pest or disease presents new challenges for agriculture."
So as a fruit grower you are always confronted with new challenges. Especially if you actually want to work with as little crop protection as possible, as we intend to do with the reorientation to regenerative agriculture.
What to do about it?
Actually, it would be important to ensure that the fallen leaves can be quickly decomposed in the fall and not remain lying around. Because damp, infected leaves form an ideal breeding ground for further spread of the fungus.
Petra Hager, a fruit farmer in Seegraben, has Marssonina on her radar, but has not yet had too dramatic experiences with the disease: "Healthy and robust trees actually survive an infestation well. Immediately threatening is Marssonina especially for very young, still tender trees."With conventional crop protection, where chemical agents can be used to combat scab, Marssonina is usually dealt with at the same time.
Somewhat more demanding is the control with biocides. If the marssonina infestation were to become a problem over a large area, Petra would chop up the foliage under the trees with a hoe and leave it for our intact soil life "to digest".
On the website of Bioaktuell it is additionally suggested to prevent a Marssonina epidemic with treatments with a clay preparation. However, this must be done at least 3 weeks before harvesting. "With a clay + sulfur treatment, an effect against scab, powdery mildew, Pseudomonas and Gloesporium storage diseases is achieved at the same time.", it says there further.
This year, some parts of the apple orchard are infested with Marssonina. Petra watches with Argusaugen over it, but is not yet quite as nervous as I😉.
Dangerousness on a scale of 1 to 10: 4
PLANT PROTECTION TOPIC
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