Specific replant disease facts for kids

Specific replant disease is a problem that happens when certain plants, like apples, pears, plums, cherries, and roses, are planted in soil where a similar type of plant used to grow. It's also sometimes called 'Sick Soil Syndrome'. When this happens, the new plants don't grow well in their first year. Their roots might be weak or turn black, and the plants might not settle into the ground properly.

What is Replant Disease?

Replant disease makes new trees and plants struggle to grow. Imagine planting a young apple tree where an old apple tree used to be. Even if the old tree was healthy, the soil might not be ready for a new one of the same kind. This can cause the new tree to grow very slowly or even die.

Why Does Soil Get 'Sick'?

Scientists aren't completely sure what causes replant disease. One main idea is that tiny living things, called pathogens, stay in the soil after the old tree is gone. These pathogens can be different types of fungi, bacteria, tiny worms called nematodes, or even viruses. They might have lived on the old tree, especially in its roots.

When a new, young tree is planted, its roots are still developing. If these roots grow into soil full of these tiny pathogens, it can be too much for the young tree to handle. The pathogens quickly attack the new roots, making it hard for the tree to grow new shoots above ground. This is especially true for trees on "dwarfing rootstock," which naturally have less strong root systems.

How Long Does the Problem Last?

Generally, replant disease can stay in the soil for about 15 years. However, this can change depending on the local conditions. The pathogens can survive in old wood and other plant bits left in the soil. How long they last also depends on whether the old orchard had small dwarf trees or larger standard trees. Standard trees have bigger, stronger roots, which take longer to break down and can keep pathogens around longer.

How to Help Plants Grow Strong

It's a good idea in gardening not to plant the same type of plant in the same spot right away. This rule applies to long-living trees just as much as it does to annual vegetables that only live for one year.

Smart Planting: Crop Rotation

For fruit trees, there's a helpful rule called the 'Pomes and Stones' rule.

• Pome fruits are like apples, pears, and quinces. They have a core with seeds.
• Stone fruits are like plums, cherries, peaches, and apricots. They have a hard pit or stone in the middle.

The rule is: Don't plant a pome fruit where another pome fruit used to be. And don't plant a stone fruit where another stone fruit used to be. But you can usually plant a stone fruit where a pome fruit was, and vice versa.

Sometimes, it's not possible to plant a new orchard in a different spot. If you have to replant in the same area, you can dig a large hole. Then, remove all the old soil and replace it with "clean" soil from a place where similar plants haven't grown before.

Using New Soil and Strong Plants

Using trees that have very strong root systems can also help them fight off replant disease. Also, plants that have been grown in large containers and already have a big ball of roots might have a better chance.

If you plant new trees a few years before the old ones are completely gone, it can give the new trees a head start. If the old orchard was removed while the trees were still healthy, it's less likely that replant disease will be a problem. This is because the levels of pathogens in the soil probably weren't very high. The problem is usually worse when trees have died in the ground, as pathogens likely helped cause their death and are therefore at higher levels in the soil.

Special Soil Treatments

Another way to control replant disease is by treating the soil with special chemicals called fumigants. This method has been used for apple and cherry trees. In the 1990s, a chemical called Methyl Bromide was often used. However, it was phased out in the 2000s. Now, newer options like Chloropicrin are used, and some studies show it works well for apple trees in Europe.

See also

In Spanish: Fatiga del suelo para niños