Key Points on Disease Control, Medication, and Field Management for Corn at the Seedling Stage

Corn is an annual monoecious plant with cross-pollination, tall in stature with strong stalks, and is an important food crop and feed crop.So what diseases occur at the corn seedling stage and what medicine should be sprayed? What are the key points of field management?

What diseases occur at the corn seedling stage and what medicine should be sprayed?

1. Yellow-leaf seedlings

Damage symptoms: At first the seedling leaves are light green, then gradually turn yellow, and in severe cases the whole leaf withers and dies.

Control methods

① Seed treatment before sowing. Remove shriveled, moldy, damaged and small grains, and use seed coating or soak the seeds in fertilizer water.

② Thin the seedlings at the right time. At the 4-leaf stage of corn, remove small seedlings, weak seedlings, diseased seedlings and field weeds.

③ After thinning the corn seedlings, apply nitrogen fertilizer at the right time.

④ If there are dry clods of soil on the corn plot before and after emergence, use a small wire rake to gently remove the dry clods on the soil surface and break them up.

2. Albino seedlings

Damage symptoms: There are white stripes on the leaves, and in severe cases the leaves of the whole plant turn white. The cause is zinc deficiency in the soil.

Control methods

① Mix 10-15kg of fine soil evenly with 1kg of zinc sulfate, and scatter it beside the seeds when sowing corn.

② For seedlings already showing zinc deficiency, use 0.2-0.3kg of zinc sulfate per 667m2 plus 100kg of water for spraying, spraying once every 7d; only 2-3 times are needed to restore the seedlings to normal.

3. Stiff-leaf seedlings

Damage symptoms

Mainly occurs before the 3-leaf stage of the seedlings. The seedlings are small in plant form with light green leaves and many black roots. After transplanting, except for the new leaves which remain green, the outer leaves turn yellow and stiff, with poor stress resistance, and dead leaves and dead seedlings easily occur.

Control methods

① At the seedling stage, mainly use decomposed organic fertilizer, do not use or use little urea as base fertilizer, phosphate fertilizer must be applied after composting, keep the soil at an appropriate temperature, and transplant strong seedlings.

② For stiff seedlings that have already appeared, promptly strengthen watering and foliar spraying of corn, using foliar fertilizers such as Gaomeishi and Sunflower.

4. Red-leaf seedlings

Damage symptoms: The seedlings grow slowly, the leaves are small, root growth does not decline, and the leaf color gradually turns red.

Control methods

① Sow at the right time.

② Use plastic film mulching.

③ Transplant corn on sunny days.

④ Use a hoe to loosen the soil in low-lying and heavy clay land.

What are the key points of field management for corn at the seedling stage?

The period from sowing and emergence to jointing is the seedling stage of corn. The corn seedling stage lasts about 20—30 days. At the corn seedling stage, the main growth is roots, increased leaves, and differentiation of stems and leaves. It is the period that determines the number of leaves and nodes. The main goal of seedling stage management is to promote roots and strong seedlings, strive for full, uniform and strong seedlings, and lay the foundation for high yield. At present, spring corn planting in our county has been completed, and the corn is at the emergence to just-emerged stage. The management measures for corn just after emergence are as follows.

1. Check seedlings and replant missing seedlings

After corn emerges, check for missing seedlings and replant them immediately. Before the 3-leaf stage of corn, if 3 or more plants (hills) are found to be continuously missing, replant in time. The method of transplanting seedlings with soil can be used to reduce differences in seedling vigor between plants. Transplanting should be done on rainy days or on sunny afternoons, and water promptly after planting to shorten the recovery period and ensure survival. If fewer than 3 plants (hills) are missing, keep double plants on one or both sides of the missing spot. Re-sowing is generally not advocated for missing corn seedlings.

2. Thinning and final thinning

Timely thinning and final thinning are key to reducing the proportion of weak plants, improving population uniformity, and ensuring suitable density. Corn grows quickly, so thinning and final thinning should be done early and at the right time. Generally, thin when 1-2 true leaves have unfolded, and final thin when 2-3 true leaves have unfolded. The principle of thinning is to remove weak seedlings and keep strong ones, and remove diseased seedlings and keep healthy ones. Thinning and final thinning should be done on sunny afternoons, because at this time diseased seedlings, insect-bitten seedlings and poorly developed seedlings wilt easily, making it easier to identify and eliminate them. For smut-infected seedlings that are short with dense leaves, thick at the bottom and thin at the top, and twisted plants, they should be thoroughly removed. In dryland and low-production plots, thin and final thin early. When keeping double plants, the spacing between the two seedlings should be 5-10cm. For intercropped corn, there are many insect pests, many damaged seedlings, and serious weed damage, making it difficult to preserve seedlings, so thin at the right time and final thin later. Generally, thin when 2 true leaves have unfolded, and final thin when 3-4 true leaves have unfolded.

3. Cultivation and stubble clearing

Cultivation is an important measure in corn seedling stage management. The principle of cultivation is: shallow cultivation near the seedlings and deep cultivation between rows. Direct-seeded film-mulched corn at the seedling stage coincides with the dry season, so shallow cultivation is needed to avoid damaging the root system from too-deep cultivation. After wheat harvest for intercropped corn, deep cultivation should be carried out immediately to clear stubble, loosen the soil, and promote root development.

4. Topdressing to promote seedlings

Topdressing at the seedling stage has the effects of promoting roots, strengthening seedlings, promoting leaves, and strengthening stalks. It is generally carried out from after final thinning to the jointing stage. The specific topdressing time should be determined according to seedling conditions, soil fertility and other conditions. For third-class seedlings, transplanted seedlings, plots without base fertilizer or seed fertilizer, low-lying moist plots, and intercropped corn, topdressing to promote seedlings should be applied early and heavily, generally before and after final thinning. For strong seedlings, plots with high soil fertility and sufficient base fertilizer and seed fertilizer, topdressing to promote seedlings may not be applied or may be applied less. In addition to chemical fertilizers, decomposed organic fertilizer can be applied. For the amount of topdressing at the seedling stage, in principle phosphate fertilizer and potassium fertilizer are all applied as base fertilizer, and the amount of nitrogen fertilizer topdressing should be determined according to the soil and seedling conditions. Generally, high-yield fields apply 20-30% of the total nitrogen amount, medium-yield fields apply 50-60%, and low-yield fields apply more than 60%. Topdressing method: generally apply in furrows or holes. The depth should be more than 5cm and more than 10cm away from the seedlings, so as not to burn the seedlings.