Specific replant disease
Encyclopedia
Specific Replant Disease is also known as ‘Sick Soil Syndrome’. This malady manifests itself when susceptible plants such as apples, pear
s, plum
s, cherries
and rose
s are placed into soil
previously occupied by a related species. The exact causes are not known, but in the first year the new plants will grow poorly. Root systems are weak and may become blackened, and plants may fail to establish properly.
One theory is that replant disease is due to a whole menagerie of tree
pathogen
s - fungi
, bacteria
, nematode
s, virus
es and other organisms. These parasitise the living tissues of the mature tree, hastening senility and death, and survive in the soil and decaying roots after the tree has died. Putting a young traumatised tree with an immature root system into this 'broth' of pathogens can be too much for an infant tree to cope with. Any new root growth is rapidly and heavily colonised, so that shoot growth is virtually zero. This is especially true if it is on a dwarfing rootstock
, which by its nature will be relatively inefficient. As a rule, replant disease persists for around fifteen years in the soil, although this varies with local conditions. Pathogens survive in dead wood and organic matter until exposed to predation by their home rotting away, and will also depend on whether the original orchard
was planted with dwarf or standard trees
. Standards have more vigorous - therefore larger - roots, and are thus likely to take longer to degrade.
It is good organic rotation
practice not to follow ‘like with like’ and this rule applies to long lived trees as much as annual
vegetable
s. In the case of temperate fruit trees, the 'Pomes and Stones' rule for rotation should be observed- don’t follow a ‘pome’ fruit (with an apple-type core—apples, pears, medlar, quince
) with a tree from the same group. A ‘stone’ fruit (i.e., with a plum-type stone, such as plum, cherry, peach
, apricot
, almond
) should be all right, and vice-versa. However, rotation is not always easy in a well planned old orchard when the site it occupies may well be the best available, and starting another orchard elsewhere may not be practical. In this case, and replanting is
unavoidable, a large hole should be dug out, and the soil removed and replaced with ‘clean’ soil from a site where susceptible plants have not been grown.
Using trees on vigorous rootstocks which will have a better chance of competing with the pathogens, or plants grown in large containers with a large root ball may also have a better chance of resisting replant disease. The extra time to cropping may be offset if new trees are planted a few years in advance of old trees finally falling over, furthermore, if the old orchard was grubbed - i.e. trees were healthy when removed, it is unlikely that replant disease would be a problem as pathogen levels may never have been high. The malady is worse where trees have died in situ—pathogens are likely to have contributed to the death and therefore be at a higher level in the soil.
Pear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....
s, plum
Plum
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...
s, cherries
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....
and rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...
s are placed into soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
previously occupied by a related species. The exact causes are not known, but in the first year the new plants will grow poorly. Root systems are weak and may become blackened, and plants may fail to establish properly.
One theory is that replant disease is due to a whole menagerie of tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s - fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
, bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s, virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es and other organisms. These parasitise the living tissues of the mature tree, hastening senility and death, and survive in the soil and decaying roots after the tree has died. Putting a young traumatised tree with an immature root system into this 'broth' of pathogens can be too much for an infant tree to cope with. Any new root growth is rapidly and heavily colonised, so that shoot growth is virtually zero. This is especially true if it is on a dwarfing rootstock
Fruit tree propagation
Fruit tree propagation is usually carried out through asexual reproduction by grafting or budding the desired variety onto a suitable rootstock.Perennial plants can be propagated either by sexual or vegetative means...
, which by its nature will be relatively inefficient. As a rule, replant disease persists for around fifteen years in the soil, although this varies with local conditions. Pathogens survive in dead wood and organic matter until exposed to predation by their home rotting away, and will also depend on whether the original orchard
Orchard
An orchard is an intentional planting of trees or shrubs that is maintained for food production. Orchards comprise fruit or nut-producing trees which are grown for commercial production. Orchards are also sometimes a feature of large gardens, where they serve an aesthetic as well as a productive...
was planted with dwarf or standard trees
Fruit tree forms
The Forms, or shapes, of most fruit trees can be manipulated by pruning and training in order to increase yield. Tree shaping can improve their suitability for different situations and conditions. Pruning a tree to a pyramid shape means that trees can be planted closer together...
. Standards have more vigorous - therefore larger - roots, and are thus likely to take longer to degrade.
It is good organic rotation
Crop rotation
Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons.Crop rotation confers various benefits to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals...
practice not to follow ‘like with like’ and this rule applies to long lived trees as much as annual
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
s. In the case of temperate fruit trees, the 'Pomes and Stones' rule for rotation should be observed- don’t follow a ‘pome’ fruit (with an apple-type core—apples, pears, medlar, quince
Quince
The quince , or Cydonia oblonga, is the sole member of the genus Cydonia and native to warm-temperate southwest Asia in the Caucasus region...
) with a tree from the same group. A ‘stone’ fruit (i.e., with a plum-type stone, such as plum, cherry, peach
Peach
The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...
, apricot
Apricot
The apricot, Prunus armeniaca, is a species of Prunus, classified with the plum in the subgenus Prunus. The native range is somewhat uncertain due to its extensive prehistoric cultivation.- Description :...
, almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...
) should be all right, and vice-versa. However, rotation is not always easy in a well planned old orchard when the site it occupies may well be the best available, and starting another orchard elsewhere may not be practical. In this case, and replanting is
unavoidable, a large hole should be dug out, and the soil removed and replaced with ‘clean’ soil from a site where susceptible plants have not been grown.
Using trees on vigorous rootstocks which will have a better chance of competing with the pathogens, or plants grown in large containers with a large root ball may also have a better chance of resisting replant disease. The extra time to cropping may be offset if new trees are planted a few years in advance of old trees finally falling over, furthermore, if the old orchard was grubbed - i.e. trees were healthy when removed, it is unlikely that replant disease would be a problem as pathogen levels may never have been high. The malady is worse where trees have died in situ—pathogens are likely to have contributed to the death and therefore be at a higher level in the soil.