Mid-January is the perfect time to take a close look at the fruit trees and shrubs while visiting the plot. Right now, in a leafless state, we can seecharacteristic signs of infection of cultivated plantsby the perpetrators of fungal and bacterial diseases. This will make it much easier for us to establish an appropriate program of prophylactic and preventive treatments, so that our plants remain in good condition while producing a high yield.
Fallen fruit and leaves left in the garden, infected
by diseases, are a source of secondary infection during spring
Most of the culprits ofplant diseases winter wellin our climatic conditions and from early spring it is a source of primary infections, which can lead to a significant reduction in yields if no treatments are applied to limitations of their occurrence in the garden.
Where do fungal microorganisms overwintercausing the most dangerous diseases of fruit plants?
Under the surface of the earth, most of the species of fungi responsible for water conduction disturbances in the plant, causing a complex of symptoms commonly known as withering, as well as fungi and bacteria causing root rot, wait for the period of cold winter. Since it is very difficult to apply a proper crop rotation in this type of perennial crops, you can only preventively plant young fruit trees and shrubs after immersing their roots for a few minutes in a solution of copper preparations.
On leafless shoots of trees and shrubs, you can now see lesions in which mycelium or colonies of pathogenic bacteria overwinter. Also on the surface of such changed shoots one can see clusters of spore forms, which will be the source of the first infections as soon as nature begins to come to life. Clearshoot necrosis indicates the presence of one or more bark diseases , such as gangrene, bacterial cancer of fruit trees, moniliosis, and even fire blight.
Brownstreaks along the entire length of the raspberry shootis a sign of the perpetrator causing the raspberry shoot dieback. Poor growth of fruit trees and the appearance of small, light-colored, tile-shaped fruiting bodies on the shoots are symptoms of a fungus causing silver leaves in fruit trees.
Another wintering site for the perpetrators of fruit plant diseases is dead, driedfruit overgrown with the pathogen's mycelium Such structures are characteristic wintering grounds for the perpetrators of brown rot in pome and stone fruit trees, hazel moniliosis and gray mold. If we see such mummified fruits on trees in the orchard, they must be harvested and destroyed, preferably burned.
Where do the perpetrators of vegetable diseases spend winter?
A vast group of fungal pathogens, pathogenic bacteria and plant viruses wait out the winter period on orin bulbs or seedsinfected during the last growing season, intended for replanting in spring. Such a method is characteristic of many dangerous causes of tomato diseases (tomato mosaic caused by viruses, bacterial cancer or tomato mottling caused by very viable bacteria that retain the ability to infect for more than 15 years) and beans (bean ring bacteriosis and ordinary mosaic caused by viruses ). Onions intended for spring planting in the field may overwinter the mycelium of the perpetrator of downy mildew - a fungal disease that is difficult to combat and causes great havoc in the crops of this vegetable.
Another place where pathogenic microorganisms find favorable wintering conditions are the remains of infected plants left in the field. In this way, many species of bacteria wait for the winter, including responsible for the occurrence of black and wet brassic rot during the growing season. This method of wintering is also popular with fungal pathogens, to which we owe the presence of diseases such as gray mold, carrot alternaria, beetroot tassel, pea downy mildew or tomato alternariosis in the season.
Many disease culprits can also survive in other organisms, waiting for the appearance of vegetables - the owners of the plot or the cultivated field. Weeds and perennial plants play a significant role here. For example, celandine may overwinter the virus responsible for the cucumber mosaic. In turn, cruciferous weeds are a very dangerous culprit of cabbage syphilis, and wild nightshades are viruses that cause various types of spots and mosaics of tomatoes, peppers and eggplants. The culprits of vegetable plant diseases can also hibernate in… insect organisms! The group of insects - hosts include aphids, thrips and leafhoppers carrying many plant viruses that are dangerous for vegetable crops. It is worth adding here that in nature there is a certain group of viruses which, after being taken with the juice of an infected plant by aphids, settle in the bodies of their hosts and multiply there. The insect's organism becomes the same source of infection as soon as the aphid sticks its proboscis into the tissues of a he althy plant to feed itself.
How long are spore forms a threat?
Spore forms, formed just before the onset of unfavorable environmental conditions (i.e. before the onset of winter) mayremain dormant for up to 10 yearsbefore losing their ability to infect the host plant. Of course, different perpetrators have different lifetimes. For example, for cottage cheese rot it is 3 years, and for cabbage syphilis it is even 8 to 9 years.Plant viruses transmitted by sap-sucking insects are similar - some are only able to infect other plants for a few hours after being absorbed by the insect, others reproduce in it throughout its life. It is worth noting here that properly carried out crops after harvesting, proper crop rotation of vegetables, appropriate selection of resistant varieties, regulated soil pH and destruction of all infected parts of plants significantly reduce the occurrence of diseases in subsequent growing seasons.
Emil Gwizdała
