Corn aphids and other pests and diseases enter the peak damage period - see the control methods here

Recently, the National Agricultural Technology Center held a corn pest consultation meeting, at which forecast technicians and experts analyzed and predicted: from late July to late August this year will be the peak damage period for aphids and other pests and diseases. So corn growers must take a look at the control methods introduced below. Don't let pests and diseases cause your corn yield to drop and lead to losses!

I. Overview of early-stage corn pest and disease occurrence

In the early stage, corn pests and diseases were mainly the first generation of Asian corn borer, the second generation of armyworm, the second generation of cotton bollworm, the two-spotted cutworm, underground pests, thrips and banded leaf and sheath blight, generally occurring at light levels, close to previous years, with an occurrence area of 265 million mu-times, among which corn pest occurrence was 240 million mu-times and corn disease occurrence was 24.8 million mu-times.

II. Occurrence trends of corn pests and diseases in the middle and late stages

It is expected that corn pests and diseases in the middle and late stages nationwide

will occur over 869 million mu-times

Pests 592 million mu-times, diseases 277 million mu-times

It is expected that corn pests and diseases in the middle and late stages this year will generally occur at relatively heavy levels, with severity greater than last year, and late July to late August will be the peak damage period for various pests and diseases. In the middle and late stages, corn pests and diseases are mainly boring, leaf-feeding, and sap-sucking pests and leaf diseases. Asian corn borer, cotton bollworm, aphids, northern corn leaf blight, southern corn leaf blight and brown spot occur relatively commonly and cause heavier damage; spider mites, twin-spotted leaf beetle, curvularia leaf spot, head smut, common smut, banded leaf and sheath blight, stalk rot and gray leaf spot occur in some areas.

For the boring pest Asian corn borer, the first generation occurs at relatively heavy to outbreak levels in Heilongjiang and northeastern Inner Mongolia; the second generation occurs at relatively heavy levels in Liaoning and central and western Jilin, western Xinjiang and eastern Inner Mongolia, and at light to moderate levels in other areas; the third generation occurs at relatively heavy levels in Henan and Anhui, and at light to moderate levels in other areas. The third and fourth generations of cotton bollworm occur at relatively heavy levels in the Huang-Huai-Hai and northwest regions; damage by peach fruit borer and giant borer has intensified in some areas.

For the leaf-feeding pest third-generation armyworm, occurrence is generally light in the northeast, north China, Huang-Huai, southwest and northwest, moderate in parts of Liaoning, Jilin, Heilongjiang, Inner Mongolia, Shandong, Shaanxi, Shanxi, Henan and Yunnan, and among them areas with high moth numbers and suitable climate may see high-density fields; the twin-spotted leaf beetle occurs at relatively heavy levels in parts of the northeast and western northwest, and at moderate levels in most other areas.

For the sap-sucking pest aphid, occurrence is at moderate levels in most of the northeast, north China, northwest and Huang-Huai, and at relatively heavy levels in drier areas of the northeast, north China and northwest; spider mites occur at moderate levels in most of the northwest and at relatively heavy levels in Ningxia, Gansu and central and western Inner Mongolia.

For diseases, northern corn leaf blight occurs at relatively heavy levels in eastern northeast China and at moderate levels in central and western northeast China and northern north China; southern corn leaf blight occurs at moderate levels in most of the Huang-Huai and southwest and at light levels in other areas; southern rust may occur at relatively heavy levels in southern Huang-Huai and other areas; curvularia leaf spot and brown spot occur at light levels in most of the Huang-Huai-Hai; gray leaf spot occurs at moderate levels in mountainous areas of the southwest and eastern northeast China; banded leaf and sheath blight occurs at relatively heavy levels in most of the southwest; stalk rot has a high risk of relatively heavy occurrence in the Huang-Huai-Hai. In addition, diseases such as common smut and ear rot will also cause certain damage in some areas. (For detailed data on the early-stage occurrence and middle- and late-stage forecast areas and regions of corn pests and diseases, please refer to the data table at the end of the article, which is clearer~)

Practical problems

Corn varieties and planting systems favor the occurrence of multiple pests and diseases

China has few pest- and disease-resistant corn varieties, and the contiguous planting method of corn in the north favors large-scale occurrence and damage by pests and diseases. Some fields with extensive management favor concentrated armyworm occurrence. At the same time, in the late growth stage, corn plants are tall and the field is closed, making corn pest and disease prevention and control difficult, which aggravates pest and disease damage.

Future forecast

Future meteorological conditions are favorable for corn pest and disease occurrence in most areas

According to forecasts by the National Climate Center, in August, precipitation will be above normal in eastern northeast China, southern southwest China, northern Xinjiang and Jiangnan, favoring the occurrence of moisture-loving pests and diseases such as Asian corn borer, armyworm, northern corn leaf blight, southern corn leaf blight, brown spot and curvularia leaf spot in these areas. Precipitation in central Inner Mongolia, most of north China and northern Huang-Huai will be 20% to 50% below normal, favoring the occurrence of drought-loving pests such as cotton bollworm, aphids, spider mites and twin-spotted leaf beetle in these areas. It is expected that in August 1 to 2 tropical cyclones will make landfall or significantly affect China, which will favor the spread and epidemic of southern rust in southern Huang-Huai.

III. Methods for controlling key pests and diseases

For Asian corn borer, use straw crushing and returning to the field to reduce the pest source base; in spring corn areas, 15 days before pupation of the overwintering generation in spring, use Beauveria bassiana to seal stacks and control overwintering larvae; during the adult emergence period of the overwintering generation, use insecticidal lamps combined with sex pheromones for trapping and killing; at the early egg-laying stage of adults, release Trichogramma to destroy eggs. At the late whorl stage, spray Bacillus thuringiensis (Bt) preparations, or rationally mix and spray agents such as chlorantraniliprole and thiamethoxam with emamectin benzoate to improve control efficacy and simultaneously control aphids, red spiders and other pests.

For corn stalk rot, treat seeds with fludioxonil·metalaxyl-M suspension seed coating agent or seed coating agents such as difenoconazole and tebuconazole, while also controlling head smut and root rot. After corn harvest, promptly remove diseased corn residues from diseased fields.

For corn leaf spot diseases, select disease-resistant varieties and plant at reasonable density. Apply topdressing at the right time to improve plant disease resistance. For chemical control, advocate early application at the appropriate time; at the late whorl stage of corn (for brown spot, at the 8-10 leaf stage), spray agents such as difenoconazole, diniconazole, pyraclostrobin and validamycin A, and spray again after 7-10 days depending on disease occurrence. Mixing with brassinolide and similar substances can improve control efficacy and reduce the dosage.

For corn banded leaf and sheath blight, select resistant or tolerant varieties. In the early stage of disease, the diseased leaf sheaths at the base of the stem can be removed, and combining this with spraying biological pesticides such as validamycin A, or agents such as dimethachlon, diniconazole and mancozeb, gives better control efficacy; spray again after 7-10 days depending on disease occurrence.

For corn aphids, spray agents such as thiamethoxam, imidacloprid, acetamiprid and pymetrozine when spot occurrences appear and at the early peak occurrence stage.

For corn spider mites, promptly clear weeds at field edges and field corners to eliminate early habitats for spider mites. When spot occurrences appear, choose pyridaben, hexythiazox, propargite, abamectin and others for spraying or rational mixed spraying, focusing on spraying the backs of middle and lower leaves of corn plants around the field edges, and also spray the weeds at field edges and corners; adding urea water, spreaders and similar substances can help restore leaves and improve control efficacy.

For cotton bollworm, release Trichogramma chilonis at the early egg-laying stage to destroy eggs, or spray Bacillus thuringiensis (Bt) preparations, emamectin benzoate and others at the peak hatching stage.

For the two-spotted cutworm, deep plow winter fallow fields, and before sowing destroy or clear stubble and remove coverings on corn sowing furrows. For chemical control, chlorantraniliprole, beta-cypermethrin and emamectin benzoate can be selected, and methods such as spraying, poison bait trapping and killing, and applying poisoned soil can be used.

According to the occurrence of leaf spot diseases and pests such as Asian corn borer, cotton bollworm and aphids in the middle and late stages, mix and spray insecticides and fungicides, and promote the use of high-clearance crop sprayers and aerial spraying control technology to enhance middle- and late-stage prevention and control operational capacity.