Physical and mechanical methods for disease control

As a physical method, trunk/white coating against frost cracks is used in fruit growing to prevent entry points for diseases.

Mechanical methods available in principle are desinfection, pruning, foliage management and protection systems. The prerequisite is that the planting material is disease-free and the working tools for grafting, pruning or planting are disinfected and clean.

Desinfection can prevent or minimize further spread of infection in soil as well as seed and plants. Seeds can be desinfected with a hot water treatment. In horticulture and arable farming, the risk from soil-borne fungi (e.g.: Verticillium sp.) is particularly high. In addition to a long crop rotation, steaming and scorching are used. In addition, for example, in onions to control downy mildew, the flaming device is set higher to burn the fungal spores directly on the plant by heat development.

In addition to increasing the yield, fungal diseases are minimized by targeted pruning and foliage management. Pruning is done only in dry weather. Pruning activities in rainy weather should be avoided because of optimal conditions for pathogens to penetrate the fresh wounds!

In viticulture, foliage management involves defoliation of the grape zone already during flowering. Foliage removal is carried out by means of leaf suckers and/or leaf shooters, which suck or shoot the leaves out of the grape zone (thus there is no danger for blossoms or young grapes!). Pay attention to the weather! Low humidity!). This, in addition to acclimatization of the vine to UV radiation, enables faster drying of the remaining leaves through good aeration. Infection with fungal diseases such as Plasmopara viticola and Erysiphe necator is thus minimized (Plasmopara needs a water film for infection; Erysiphe necator needs moist and warm conditions for infection). Prunung of the shoot tips should be done as late as possible, otherwise a lot of new stingy shoots will form and the risk of the grape zone becoming overgrown is increased. Early summiting also gives too early an impulse for fruit to be formed. The result is dense berry growth (desirable: loose berry) and fruit bursting. As soon as berries stick together and especially when it rains shortly before harvest, there is a danger of Botrytis.In orchards, targeted summer pruning reduces the foliage mass and promotes aeration. In arable farming, flailing and harrowing are used to remove diseased plant parts or to strengthen the resistance of certain plant parts. For example, the foliage of potatoes is killed by harrowing about three weeks before harvesting to prevent the pathogen that causes late blight (Phytophthora infestans) from spreading from the infected potato foliage to the tubers. In addition, in potatoes, harrowing thickens the skin of the tubers, making them more resistant to pathogens. In cereals, harrowing removes diseased, old leaves.

Protection systems

Protective netting, in addition to animal damage, keeps vineyards and orchards safe from weather events such as hail and heavy rain. Injuries from hail would provide pathogens (e.g. Botrytis, Pseudomonas) with optimal infection sites. Mitigated rainfall reduces the risk of splashing (e.g. Botrytis).

In horticulture, shading compensates for temperature fluctuations and suppresses powdery mildew.Soil cover in the form of foil or straw prevents the transfer of pathogens from soil to crop. In strawberry cultivation, the classic straw covering at the beginning of flowering prevents the fruit from becoming dirty and prevents fungal attack by Botrytis cinerea graymold.

Hygienic measures

Hygiene measures aim to prevent the introduction of a disease into the crop or to minimize and - in the best case - eradicate it. This can be achieved by targeted pruning, which removes old and diseased plant parts, as well as by crop residue hygiene or by preventing the spread of diseases and vectors.

To prevent the introduction of a disease, healthy and certified planting and sowing material is of utmost importance. Especially with strawberries, young plant quality is extremely important and the introduction of diseases such as Phytophtora cactori  should be avoided at all costs. But it is also important to keep disease-introducing vectors, such as insects, away from the crop. In viticulture, the spread of grapevine cicada and phylloxera by humans from vineyard to vineyard (infectious from L5) must be avoided in order to prevent secondary infections by bacteria, fungi and viruses.

Preventing the spread of disease: If parts of a crop or the entire crop are affected by a disease, pruning of diseased plant parts, grubbing and disposal or burning of individual plants or the entire crop and/or appropriate crop residue and fallen leaf management will help. Special attention should be paid to notifiable quarantine diseases.

In viticulture, for example, plants affected by flavescence doree (golden yellowing) must be grubbed up to prevent transmission by grapevine cicada to other plants. Grapevines showing the disease complex Esca must also be either grubbed or tried to be cured by special grapevine surgery techniques under development. In orchards, complete harvesting is important. Pruning must always be done into the healthy wood. Injuries must be avoided, as they are entry points for diseases. Diseased material is removed after pruning and from the plant and burned if necessary. Plants affected by quarantine diseases such as fire blight must be grubbed. Fruit mummies must also be removed and burned to prevent sources of infection for the following year. In addition, foliage removal should be encouraged by tilling, incorporating, spraying with vinasse, and sweeping foliage out of tramlines to suppress virus diseases. While fungal spores, for example, can survive in the substrate for up to 15 years, viruses can only survive in the plant material or host. In arable crops, individual plants must be removed if they are infested with soil-borne fungi such as Phytophthora or Verticillium. In corn, incorporating stubble into the soil reduces the risk of Fusarium stem and tuber rot in the future years crop. In Rhizoctonia-infested areas, corn should be avoided in the sugarbeet rotation or corn crop residue should be well chopped and incorporated, as the fungus uses organic matter to survive in the soil. The promotion of good old straw rot should generally be stimulated by multiple flat tillage passes.

In addition, special attention should be paid to keeping equipment clean. If there is a risk of disease spread, it is necessary to clean the equipment or the tractor at the washing station (kärchern, hot water treatment). In horticulture, for example, tomato and bell pepper crops must be uprooted and burned if the notifiable bacterial wilt Clavibacter occurs. In general, crop residues must be removed or worked deep into the soil.