The main reasons for decolouration of leaves of winter grain crops are given in article.
REASONS of DECOLOURATION of LEAVES of WINTER WHEAT
In recent years in crops of winter wheat in many areas of Ukraine symptoms of the following character are shown: antotsianovy coloring of a leaf, pozhelteniye and dying off of the top leaves, in certain cases and flag leaf. It is necessary to note that on early and optimum terms of sowing more intensive dying off of a flag leaf is noted. Similar symptoms aren’t characteristic for defeat by mushroom and bacterial diseases.
The symptoms noted above can be caused by several reasons. Change of coloring of a leaf is observed at a shortcoming or an imbalance of nutrients. So, at a lack of manganese on a leaf at first there are small light yellow spots, but veins remain green. Over time hlorotichesky sites become yellow or pale-yellow. More often it is observed on alkaline and neutral soils.
At phosphoric starvation leaves gain dark green color, its tops become dim with a brown shade, then die off. On winter wheat and a rye the first signs appear in the autumn. Tops of the bottom leaves get lilac or red-violet coloring, other leaf – dark green with a blue shade. Delay of growth of a stalk and a root is thus observed, leaves are formed small and narrow, a bad kushcheniye.
Pozhelteniye of edges of a sheet plate of young leaves occurs from top to down, a mosaic spottiness, on some grades red or antotsianovy coloring are symptoms of manifestation of infection with a virus of a yellow karlikovost of barley (VZhKYa). Carriers of a virus are larvae, and also an imago of several species of plant louses (big cereal, ordinary cereal, cheremukhovy cereal and others). Infection of crops of VZhKYa begins in the autumn. Consequences of this process are shown in the spring in an exit of plants in a tube and kolosheniye when any ways it is essential to improve a situation it is already impossible.
Crops of early and optimum terms of sowing are most of all damaged by plant louses. Infection of crops of winter wheat proceeds also in the spring, more early and optimum terms of sowing. In this regard distribution of an illness is noted by favorable weather conditions, especially in the autumn when settling crops by wreckers. Settling of crops of winter wheat plant louses closely intertwines in the autumn with VZhKYa distribution. It is necessary to note that cereal weeds play a role of rezervator of an infection. Plants of winter crops which border on statsiya of wild cereal vegetation, can be surprised to 100 %.
Besides, antotsianovy coloring of a leaf can be observed at sharp change of weather conditions, especially at weak plants.
Thus, the pozhelteniye, other decolouration of a leaf and its drying most likely are caused by such reasons:
– a cold snap and frosts of the current year, a lack of heat (the sum of effective temperatures is lower than norm), further sharp temperature drop;
– ratio violation between quantity in the soil of basic elements of a food;
– wheat top dressing by only nitric fertilizers that promoted intensive increase of a biomass and decrease in firmness of plants to stressful conditions;
– infection of plants with virus diseases, including VZhKYa.
The researches which have been carried out by institute of protection of plants of UAAN, it is established that at defeat of plants to 70 % (antotsianovy coloring) yield losses can make to 40 %.
In Permyakov, the chief of the State station of protection of plants, Century. Garden, leading agriculturist of laboratory of forecasts and diagnostics.