Detailed Explanation of Key Technical Management Points for Summer Corn After Disaster

Summer corn is an important autumn crop in our province. This waterlogging disaster has caused great harm to summer corn in our province. Experts from the provincial corn industry system have put forward post-disaster management recommendations based on the actual situation, for farmers' reference:

1. Technical Recommendations for Corn Management After Disaster (Professor Cui Yanhong, Hebei Agricultural University)

1. Drain standing water from the fields. For plots with obvious standing water in the fields, every possible means should be used to drain the standing water to reduce the time corn plants are soaked.

2. Intertill to dissipate soil moisture. For plots where standing water has already been drained or plots that have only suffered waterlogging damage, intertilling and hoeing can be carried out promptly when the field is accessible.

3. Apply quick-acting fertilizer as a supplement. Given that summer corn in our county is about to enter the large trumpet stage, it is recommended to combine the topdressing at the large trumpet stage with post-disaster fertilizer management. For plots that have not yet been topdressed with ear fertilizer, 20-25 kg of urea can be applied per mu; for plots that have already been topdressed with ear fertilizer, an additional 5-10 kg of urea can be applied per mu. When topdressing, it is essential to apply in furrows deeply, or apply in combination with intertilling, avoiding broadcast application. If conditions permit, when the sky clears after rain, promptly carry out foliar topdressing with 0.5% urea + 0.2% potassium dihydrogen phosphate. When spraying, it is essential to ensure that the urea and potassium dihydrogen phosphate are completely dissolved and mixed evenly, to avoid leaf scorching caused by excessively high local concentrations, which would aggravate the degree of damage; generally, it can be sprayed twice consecutively, with an interval of about 7 days.

4. For plots where lodging has occurred, corresponding field management measures can be taken according to the specific circumstances of the lodging.

① Summer corn is currently at the small trumpet stage. After lodging occurs, generally no special management measures are needed; after the rain, it will gradually recover upright growth on its own.

② For summer-sown plots that have been knocked down by floodwater, some leaves of the plants are often buried by silt, making it difficult for the plants to recover upright growth on their own; for such plots, after the disaster, the mud on the leaves should be removed as soon as possible, or the leaf portions buried by silt should be cut off with a sickle, to help the plants recover upright growth as quickly as possible.

③ For summer-sown corn in which some mud and sand have entered the whorl after lodging, this often makes it difficult for subsequent leaves to emerge; for such plots, after the disaster, a sickle can be used to cut off the portion of the whorl leaves that have mud and sand in them, to help subsequent leaves emerge. However, the fewer leaves cut off, the better, and try not to damage the plant's apical growing point.

2. Technical Recommendations for the Prevention and Control of Diseases, Insects, and Weeds in Summer Corn After Waterlogging Disaster (Professor Zhang Jinlin, Hebei Agricultural University)

1. Raise awareness of weed control: At present, most summer corn has entered the canopy closure stage. A 10% glufosinate-ammonium aqueous solution at 200-300 mL/mu can be used for directed inter-row spraying between corn rows to control weeds. However, when using glufosinate-ammonium for directed inter-row weed control in corn, keep the nozzle as low as possible to reduce the amount of herbicide sprayed onto the corn, in order to prevent phytotoxicity.

2. Control of leaf spot diseases, mainly corn brown spot: Based on the characteristic of excessive rainfall this year, various leaf spot diseases, mainly brown spot, will occur more severely. At present, the control of corn brown spot still mainly relies on the application of fungicides. Recommended agents: (1) 10% difenoconazole water-dispersible granules or 12.5% diniconazole wettable powder or 25% propiconazole suspension concentrate at 2000-2500 times dilution; (2) 10% azoxystrobin suspension concentrate at 1000-1500 times dilution; (3) It is not recommended to use tebuconazole or dithiocarbamate protective fungicides; agents such as carbendazim and thiophanate-methyl have only average effectiveness and are also not recommended.

3. Strengthen the control of pests such as the brown-footed false potato beetle: Adults of the brown-footed false potato beetle feed on the middle and upper leaves or leaf whorls of corn, forming net-like holes. When the insect population is high, they can eat all the leaves, leaving only veins, causing yield losses. Control recommendations: (1) Remove weeds promptly to effectively reduce the damage by the brown-footed false potato beetle; (2) Apply chemical control promptly against adults. Recommended agents: thiamethoxam or pymetrozine or acetamiprid + cyhalothrin.