Challenges and care for wheat crops in May

In May, the grain crops begin to approach the end of their development, finish the spindle and move to the tillering phase. During this period, among the most common problems are secondary weeds, diseases and pests.

It is important to maintain the optimal health of the crop in this phase, because the full development of the flag leaf is responsible for 70% of the yield. Therefore, in addition to treatment against diseases and pests, it is advisable to add a foliar fertilizer containing amino acids and nutrients.

Bulagro agronomists recommend several proven combinations that have been repeatedly tested and have shown excellent results under all conditions:

• Megafol (15 ml/ha) with Master 20.20.20 or Master 15.5.30+2% Mg (25 g/ha) - biostimulator, anti-stress product and nutrient carrier, in combination with highly soluble crystalline fertilizers, with a high concentration of microelements in chelated form;
• Megafol (15 ml/ha) with EDTA Mix (5 g/ha) - biostimulator, anti-stress product and nutrient carrier, in combination with seven microelements in chelated form;
• Megafol (15 ml/ha) with EDTA Zinc (5 g/ha) - biostimulator, anti-stress product and nutrient carrier, in combination with 15% pure chelated zinc;
• Codafol Maximus at a dose of 20-25 ml/ha - NPK fertilizer enriched with macro and microelements, amino acids and natural stimulants.

These combinations will ensure full flowering, overcoming microelement deficiencies and optimal seed setting.

For effective absorption and use of the products introduced in the earing phase, it is very important to add an adhesive to the working solution. The product Orpheus is a super-wetting agent that helps the uniform spreading of the drop on the plants, the penetration of plant protection products not only into the surface parts of the leaves, but also into the bosom of the spike, in order to guarantee the preservation of the yield. Orpheus accelerates the absorption rate of plant protection products. The application of this adhesive also reduces the formation of mycotoxins in the grain and preserves the quality of the production. The recommended application dose is 5-10 ml/ha.

Secondary weeding is a problem that no one wants to find in their fields, because it creates competition for nutrients, moisture and light with the main crop. To combat secondary cereal and broadleaf weeds, we recommend using Refine Extra at a dose of 6-7 g/ha.

When touring the field, symptoms and presence of common and oat aphids, harmful wheat bugs, wheat leech, wheat thrips and wheat stem wasps can be detected.

Aphids

In spring, with warming weather, the larvae hatch and suck the sap from the upper and lower parts of the leaves and stems of the plants. In a mass attack, they form large colonies that completely cover the leaves, and sometimes the vagina. The damaged leaves fade, turn yellow and die. In the flowering phase and the beginning of milky maturity, a massive migration of aphids to the ears begins. As a result of the damage caused, the number of grains in the ears decreases and they remain shriveled, germination decreases, and yields decrease. Losses are greatest when the mass appearance coincides with flowering and grain formation in cereals. During one growing season, aphids develop 8-10 generations. Their multiplication is positively influenced by the increased nitrogen content in plants. In addition to direct damage, aphids are a vector of a number of viral diseases of cereal crops (wheat stripe mosaic, agropyr mosaic, bromus mosaic). The fight against enemies is carried out in autumn and spring in the phenophase from "emergence" to "twining" - at a density (PIV) of 3 aphids per plant. The fight against the enemies can be carried out with any of the following insecticides: Citrin Max at a dose of 5 ml/hectare, Sherpa at a dose of 25 ml/hectare and Mospilan 20SP at a dose of 15 g/hectare.

Harmful wheat bug

The wheat bug is one of the most dangerous enemies of cereal plants. It is most often found in wheat, less often in barley, oats and rye. The bug overwinters as an adult and migrates to the crops when the temperature rises above 11-12oC. Its harmful activity begins with damage to the stems and progresses to seepage of the flag leaf, from where they extract sap from the ear. Above the puncture site, the ear turns white, no spikelets form and the damage is known as ‘‘white ear’’. The fight against the enemy begins with the timely destruction of weed vegetation and surrounding potential wintering sites, but it can also be carried out with chemical methods. Our agronomists recommend the use of insecticides at a PIR of over 2 pcs / sq.m in a dry and warm spring in sparse crops; 4 pcs / sq.m. at normal density and 1 pc / sq.m. in seed production areas. The insecticides we recommend for the control of the woodlice are: Mavrik 2F at a dose of 2,5 ml/ha, Mospilan 20SP at a dose of 1,25 ml/ha and Sumi Alfa (Sumicidin) at a dose of 2,5 ml/ha.

Wheat Leech

In recent years, a widespread spread of wheat leeches has been observed in the country. When temperatures rise above 7oC, adults emerge to the surface, and their mass appearance coincides with the end of the wheat plant's tillering period. The pests gnaw narrow and long strips parallel to the central vein of the leaves. In severe damage, the leaves turn white and dry. The pest lays its eggs on the upper surface of the leaves singly or in a chain. The fight against the common wheat leech is carried out through early sowing, fertilizing the crops, crop rotation and deep plowing after harvesting. Chemical protection is necessary when the IED exceeds 30 pcs./sq.m. in sparse crops and dry spring and 50 pcs./sq.m. in dense crops and cool spring. The insecticides that our agronomists recommend for fighting the leech are: Sumi Alpha 5EK (Sumicidin) at a dose of 25ml/ha, Mavrik 2F at a dose of 25ml/ha and Proteus 110 OD at a dose of 50ml/ha

Wheat thrips

Wheat thrips multiply massively in warm years with little rainfall. Adults cause damage in the phenophases of spindle - earing - flowering of wheat. The part of the ear at the point of sucking (most often the top) turns white, remains underdeveloped and the ears do not form grains or the ones that do form are weak and damaged. The main damage is caused by the larvae, which suck sap from the chaff, the flower parts, and later from different places on the grains in milky and waxy maturity, most often clustering around the "furrow" of the seed. Damaged grains have a hollow appearance, lower weight and poorer seed quality. The fight against the enemy begins when the average density is above the threshold of harmfulness: for adults - 10 thrips per stem, for larvae - 20 pieces / 1 class (in dry spring) or 30 pieces / 1 class (in wet spring). The larvae of wheat thrips hatch en masse in early June and there are no officially registered preparations for the control of thrips on cereal crops.

Wheat stem wasp

The wheat stem wasp develops one generation in two years and overwinters as a cocoon in post-harvest residues. The wasps begin flying at the end of April in the spindle phase, and their mass flight coincides with the flowering of cereal crops. They lay eggs in the stems, and the larvae are the main cause of the damage. By gnawing at the base of the stem, they reach the base of the plant and in strong wind and/or rain, the plants break en masse and lie on the ground, which leads to yield losses. There are no registered insecticides in Bulgaria for the control of the wheat stem wasp. The fight against the enemy is carried out mainly with agrotechnical measures, one of which is deep plowing (22 to 35 cm), followed by spring cultivation and harrowing to a depth of 18 cm. Normal crop density, cultivation of resistant varieties, crop rotation and earlier harvest are also recommended. The threshold of economic harm of the wasp is 3 pcs./sq.m.

In regions with rainfall and moisture, active development of the diseases powdery mildew, brown rust and septoria is also observed. These diseases can be easily controlled with some of the following products: Mirador Forte at a dose of 12,5 ml/ha, Ricali at a dose of 10 ml/ha, Tesoro at a dose of 10 ml/ha, Mystic 25 EV at a dose of 10 ml/ha and Amistar Prime Package.

In regions with cool and humid weather, dense crops, frequent repetition of cereal crops in one field and abundant and one-sided nitrogen fertilization, it is important to monitor the development of powdery mildew (Erysiphe graminis). Signs of the disease can be found on the leaves, leaf sheaths and stems of plants, in the form of a white powdery coating. Chlorosis is often observed between individual infected spots on the leaves, and early infections and severe attack lead to yellowing of the tissues and leaf scorch. In some relatively resistant barley varieties, the disease can manifest itself in the form of brown necrosis on the leaves. The disease is especially harmful when it affects the flag leaf and the ear. In such a development, the grain remains smaller, poorly nourished and has deteriorated qualities. If symptoms are present in 10-15% of the grain areas, it is necessary to take chemical measures to combat the disease.

Brown rust is widespread, the development of the disease is especially intense in wet autumn, mild winter and rainy weather in the period from the appearance of the ligule on the uppermost leaf to flowering. It attacks all green parts of the plants, with its symptoms more often appearing on the upper part of the leaves, on the sheaths and stems. The spots that appear are elliptical or slightly elongated, filled with unevenly scattered rusty-brown clusters of uredosori. In severe attack by the disease, the leaf petiole twists and dries prematurely, and the grains remain small and wrinkled.

Septoria is now also widespread in our country and is a highly damaging disease of wheat and cereal crops, and can reduce yields by up to 50%. The symptoms of the disease are expressed by small chlorotic stripes on the leaves, located between the veins. Gradually, the spots grow and acquire a pale gray to brown color, and the tissues in them burn. Soon after their growth, numerous, dark brown to black, round formations (pycnidia) appear in the spots on both sides of the leaf, which are a characteristic symptom. The spots on the developed leaves are most often elongated, with an irregular to elliptical shape, limited by the leaf veins and dotted with numerous pycnidia. Heavily attacked leaves burn. Disease control is carried out using a variety of methods, including: use of resistant varieties, adherence to a 3-4 year crop rotation, deep plowing of plant residues, sowing at optimal times and following recommendations for sowing rate, balanced fertilization (because high nitrogen rates make plants more susceptible to disease) and timely control of early spring weeds.