Why Does Corn Go Bald? Causes and Control Methods

Corn bald tip refers to the phenomenon where the top of the corn ear fails to set kernels and the kernels are not plump, commonly known as bald tip or bald ear. It is one of the main reasons affecting stable corn yields, and in severe cases can cause a 20%-30% reduction in yield, so effective measures should be taken in production to reduce and prevent the occurrence of bald tip. So how is the corn bald tip phenomenon caused? And how can it be prevented and controlled?

1. Causes of Bald Tip

The differentiation of female florets, silking and kernel formation in corn begin from the middle and lower part of the ear, then proceed simultaneously upward or downward from there, and finally end at the top. When environmental conditions are unsuitable, the florets or fertilized embryos at the top often abort due to insufficient nutrient supply. Apart from the genetic characteristics of corn varieties, the causes of corn bald tip are mainly as follows:

1. Nutrient deficiency

Phosphorus deficiency in the soil affects cell division. Especially during the silking elongation stage, phosphorus deficiency causes slow silk elongation and affects pollination. If the kernels at the top of the ear are shriveled and small, showing an abnormal white color, it indicates deficiency of phosphorus and potassium, especially potassium deficiency.

2. Spikelet degeneration

The spikelets at the top of the ear are degenerated and malformed, sometimes showing hermaphroditic flowers or male flower development while female flowers do not develop. This affects normal pollination of corn and makes it difficult to set kernels.

3. Late silk development

The silks at the top of the ear develop late and silking is delayed, which often causes a mismatch with the male flower shedding period for pollination, making it impossible to set kernels.

4. Dryness and water deficiency

The most suitable temperature for corn flowering is 22-26°C, and the most suitable relative humidity is 65%-90%; when the temperature is above 30°C and the relative humidity is less than 60%, flowering decreases significantly; when the temperature is above 38°C, the tassel does not flower. When corn encounters drought during the flowering and pollination period, the interval between male and female flowering is prolonged, causing the silks to miss the peak pollen shedding period of the tassel when they emerge, resulting in poor pollination and affecting kernel set. It can also cause the top florets to degenerate into sterile flowers during differentiation due to drought or insufficient fertilizer and other reasons.

5. Excessive dense planting

Excessive planting density causes poor ventilation and light transmission conditions in the later growth stage of corn, affecting the normal growth of corn.

6. Soil micronutrient deficiency

When the soil is deficient in boron, it has adverse effects on the formation of corn tassel pollen and its activity during pollination. When zinc is deficient, white spots appear on the leaves of old seedlings and rapidly expand, forming localized white areas and necrotic spots, with shortened internodes, which also easily causes abnormal growth and development of the ear, leading to bald tip.

7. Occurrence of pests and diseases

The occurrence of various corn leaf spot diseases, corn seedling blight, sheath blight, and stalk base rot can all affect the normal growth and development of corn, causing poor corn growth. In particular, corn aphids begin to occur in large numbers when corn tassels, preventing corn from flowering and pollinating normally, causing bald tip and missing kernels.

2. Control Measures

1. Carefully select good seeds

Choose coated seeds suitable for local planting that are high-yielding, plump, and highly viable, and before sowing treat them by sun-drying and seed dressing methods.

2. Rational fertilization

Fertilization should combine nitrogen, phosphorus, and potassium, along with appropriate application of micronutrient fertilizers. For plots with low fertility, heavy topdressing should be applied, but attention should be paid to applying more early and less later to prevent excessive vegetative growth and late maturity. Watering should be controlled at the seedling stage to promote young ear differentiation and shorten the interval between tasseling and silking, increasing pollination opportunities. In fertilization, do the following: apply heavy base fertilizer. Apply farmyard manure and phosphorus-potassium fertilizer thoroughly in one application as much as possible. For medium-fertility fields, apply 750-1000 kg of high-quality farmyard manure, 6 kg of urea, 50-60 kg of superphosphate, and 1.5-2 kg of zinc sulfate per mu; for fields with poorer or better fertility, apply slightly more or less on this basis. Skillfully apply ear fertilizer. 10 days before corn tasseling, that is, the commonly called large trumpet stage, generally apply 25-30 kg of ammonium bicarbonate per mu as topdressing; when the female ear begins to silk, apply 3 kg of urea per mu as topdressing. Spray zinc fertilizer. At the corn jointing stage, use a 2% zinc sulfate solution for uniform foliar spraying.

3. Water at the tasseling and flowering stage

Corn is sensitive to water 15 days before tasseling. When drought occurs and the soil moisture content is below 80% of the field maximum water-holding capacity, irrigation should be carried out immediately. This is beneficial for corn pollination and grain filling. Fourth, artificial supplementary pollination. During the peak flowering period of corn, seize the time to carry out pollination in the morning after the dew has dried and when the male flowers begin to shed pollen in large amounts. The rope-pulling method or plant-shaking method can be used, once every 2-3 days, for 2-3 consecutive times, which can prevent the occurrence of bald tip.

4. Rational close planting

Enhance resistance. According to variety, soil, cultivation method, and climate factors, with the goal of establishing a high-photosynthetic-efficiency population structure, plant rationally and closely, ensuring both sufficient ear-bearing density and good ventilation and light transmission conditions. Planting density is generally about 4000 plants per mu; fields with better fertility should appropriately increase the number of plants, and fields with poorer fertility should appropriately reduce the number of plants. At the same time, it is best to use wide-narrow row planting to avoid weak seedlings caused by uneven fertilizer, water, and light.

5. Moderate detasseling

Artificial pollination. According to field growth conditions and the tasseling situation of the whole field, moderately detassel every other row or every other plant, reducing water and nutrient consumption, improving ventilation and light transmission conditions in the upper part of corn, and increasing photosynthetic efficiency. This can both reduce the formation of bald tip and reduce the damage of corn borers.

6. Drought resistance and drainage

Enhance resistance. Timely resist drought and drain waterlogging, eliminate the impact of adverse factors on corn growth, improve the field microclimate, enhance plant stress resistance, accelerate the synthesis and accumulation rate of photosynthetic products, and reduce bald tip.

7. Prevent and control pests and diseases

To control corn seedling blight, sheath blight, and stalk base rot, seed dressing can be done with 30% Miaojundi wettable powder at 0.3% of seed weight, or with 12% triadimefon EC or 12.5% diniconazole EC at 0.02% of seed weight; after diseased plants are found in the field, spray with 30% Miaojundi wettable powder 800-fold solution, 50% thiophanate-methyl wettable powder 800-fold solution, or 80% Lüheng No. 2 700-800-fold solution mixed with Tianda 2116 diluted 1000-fold, all of which have good control effects on corn seedling blight, sheath blight, and stalk base rot.

For the control of various leaf spot diseases, in the middle and late growth stages of corn, after corn leaf spot diseases occur, spray with 50% thiophanate-methyl wettable powder 800-fold solution or 50% carbendazim wettable powder 800-fold solution.

For the control of corn borers, at the late heart leaf stage of corn, 3 kg of 3% carbofuran granules can be used; or after corn aphids occur, spray with 40% omethoate EC 1000-fold solution, 50% monocrotophos EC 800-fold solution, or 10% imidacloprid wettable powder 3000-fold solution.