The first reason onion krutogolovy. These pests overwinter in the soil or in the bow, which for some reason is not removed. Adult beetles are eating the onion through and through, it begins to wither, and around the formed holes or white spots. Pest larva gnaws a longitudinal track within the feathers, reminiscent of the white stripes. Then the tips of the feathers begin to turn yellow, the feathers curl and wither. That the onions are not yellowing, you need to constantly and carefully loosen the garden bed, adding mustard powder, ground black or red pepper, wood ash. The remains of the bow should be eliminated. Do not forget about crop rotation – onion ridge annually to move to another place, preferably away from the previous one. Yellowed feathers should be cut, leaving 4 inches.
The second reason why yellow onion – onion fly. Onions infected with the larvae of this pest, early yellow and wither. From the onion fly suffers not only the pen but also the bulbs. They begin to rot, easily pulled out from the soil. That the onions are not yellowing because of the onion fly, it is necessary to deeply dig the garden, seeding as early as possible, in time to remove infected plants. For Luke, a good neighbor will be carrots. These crops help each other with their smell to deter pests. Folk remedies of struggle against yellowing onion pen, cigarette or tobacco dust, ash. They sprinkled the onion bed. In addition, every three weeks you can sprinkle the onions with salt water (200 grams of salt per bucket of water). Irrigation is carried out carefully, strictly under the bulb. The first time you can use salt water, when the feather has grown to 5 centimeters. After harvest, the bed should be thoroughly cleaned from the remnants of the bow.
The third reason – shortage of nitrogen. After prolonged rainfall with the rain water nitrogen compounds go deep into the soil and become inaccessible to the onion roots. That the onions are not yellowing, in this case, the required nitrogen fertilizers (ammonium sulphate, nitrate) or dung infusion.
That the onions are not yellowing, you need to arrange proper watering. From a large number of moisture onion begins to rot, so watering the garden with a bow should be rare, but abundant.
Onions, like all vegetables, unfortunately susceptible to disease. This bacterial rot, rust, and rot the stems. These fungal diseases are accompanied by yellowing and subsequent death of plants. That the onions are not yellowing as a result of disease, should use only perfectly healthy planting material before planting is recommended to warm for 10 hours at 40 °C. the Soil pre-treated with drug "Hom" (40 grams per bucket of water).
In late July, the onion Matures and naturally yellow onion feather. At this time pour is not necessary. The harvest should iterate, and dry to ensure proper storage.