- Details
-
By "disease", we often talk about any abnormal symptom on a plant. In reality, one must make the distinction between the different categories of problem. This will allow you to act correctly, without needing to be a specialist!
Disease or pest, it is not the same!
True diseases are caused by either mushrooms, bacteria or viruses. It is especially those of the first two categories, which are worrying. Viruses rarely cause great damage in gardens. The rust disease, the powdery mildew disease, the tomato disease (mildew), Botrytis on strawberries, black spots on Maple leaves, etc. are diseases caused by fungi. To cure the plant, we use a product called a "fungicide", which can be natural and ecological, of course. The diseases caused by fungi seem to be encouraged by climate changes.
Branches drying out on conifers, splitting of the bark on cherry trees, and withering of Lilac trees are caused by bacteria. Luckily, these diseases are rare. Against the diseases caused by bacteria, the only efficient weapon is antibiotics, and their use is strictly forbidden in the garden.
These two types of problems are to be distinguished from damage caused by pest, meaning an animal that causes damage to a plant by stinging or eating it. Often, it is insects, birds or molluscs (snails and slugs). A product manufactured to fight against fungi will then be inefficient, as the slug is not a fungus! Pests often leave traces: droppings, mucus, dead skins, all those rather unappetizing signs that a pathogenic mushroom would not leave behind him!
Distinguish the differences
Discerning the difference between damage caused by a disease or pest is often easy. Disease spreads out progressively.
For example, powdery mildew on Asters leaves, in autumn, covers the flowering stems, little by little. A pest provokes damage in waves, each time it eats. Caterpillars, for example, hide during the day and come out at night. From one day to the next, a plant can be ruined entirely, as pests are voracious! The type of damage is also different: when there is a pest, the difference between the healthy part and the attacked part being highly visible.
Diseases leave borders more or less noticeable between the healthy parts of the plant and the diseased ones. This is why it is so important to observe accurately ones plants: if some damage is noticed, look at the margins and how it is advancing. If its limits are not clearly visible and it is spreading little by little, it is almost certainly a disease. If the damage is localised, and new damage is noticed each time you look at the plant, then, it is almost certainly the presence of a pest. - Photos (1)
Disease or pest?
There are no traces of biting and the limit between the diseased parts and the healthy ones is not clearly visible: It is a disease (Botrytis).
Author: Jean-Michel Groult
Copyright
Copyright