Weeds are so frustrating. They keep popping up in the field or garden without heeding your desire to grow the perfect vegetable and to earn money. Sweet Corn Weeds
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It’s fair to say that weeds compete for light, nutrients and space for crops, such as sweet corn, which is the topic of this month’s column. Chemical control and harvesting are also affected by too many weeds present. As growers know, the quality can be damaged severely, and yield can be reduced to cause a profit loss. Ignoring weeds in fields is never a good idea, whether you’re a commercial grower or weekend gardener.
As Extension agents and specialists often tell growers, an efficient, integrated weed management program is key to successfully controlling weeds in sweet corn. Without proper control, consumers won’t buy the corn, and the grower won’t earn any money to pay bills or feed his family. Weeds can also be home to insects and built-up diseases, according to University of Georgia Extension weed agronomists Stanley Culpepper and Lynn Sosnoskie in the Commercial Sweet Corn Production in Georgia guide. They say serious weed problems in sweet corn can include summer annuals such as Texas millet and other grasses, yellow and purple nutsedge, morning glory and pigweed. So they recommend a comprehensive weed program that looks at cultural control practices, mechanical control practices and use of herbicides. One practice without the other may lead to poor or reduced weed control.
Effective cultural practices can help grow a sizeable plant canopy to shade out certain weeds to keep them from growing. Such cultural practices can involve planting seeds that have no weeds present, preparing seedbeds properly, applying the right amounts of fertilizer and water, following row spacing and managing insects and diseases on time, according to Culpepper and Sosnoskie. Regular rotation out of fields with heavy weed presence can help, too. They recommend cleaning equipment when moving from heavy- to low-infested fields. This helps in blocking new weed species from entering fields and reducing spread of disease.
Growers are wise to plow, disk, cultivate, mow, hoe or hand-pull to eliminate weeds. Those practices are part of mechanical control. Culpepper and Sosnoskie advise planting in a clean seedbed.
Herbicides are often used to control emerging weeds. Before planting in a clean seedbed, Culpepper and Sosnoskie recommend tilling the soil well or using burndown herbicides to control those emerging weeds. They warn that when tilling and using herbicides it may reduce the effectiveness of herbicides so growers may need to apply more later.
Choosing herbicides is important in a weed management program. Before planting, identify the weeds present in the fields to select the proper herbicide, Culpepper and Sosnoskie advise. Growers also should learn the best way to apply each herbicide they use, either as a soil- or foliage-applied product. For example, they say a paraquat such as Gramoxone is foliage applied. Whereas an s-metolachlor such as Dual is soil applied.
Growers can apply foliage-applied herbicides to plant leaves, stems and shoots, Culpepper and Sosnoskie recommend, and they must cover the plant well. As for soil-applied herbicides, growers can apply to the soil surface or incorporate into the soil. Good moisture and rainfall, and proper application timing, are needed for adequate control. Before applying, read the label for proper rates and any crop-rotation restrictions. Both can result in crop injury, if not followed correctly.
Growers should look for commonly occurring weeds. Stephen Barts, a Crop and Soil Science Extension agent in Pittsylvania County, Virginia, said most broadleaf weeds at preemergence are easy to manage because you can control them with an s-metolachlor such as Dual or an atrazine product such as Aatrex. He recommends Dual for annual grasses and nutsedge. An atrazine product is good for broadleaf weeds. Also, an alachlor product such as Lasso and Micro-Tech are good control for most annual grasses, pigweed and nightshade. A mesotrione product such as Callisto is good for common lambsquarter.
For over-the-top postemergence control, he recommends atrazine or 2,4-D. “About 8 inches tall is about the maximum for a broadcast spray,” Barts said. Then, “you need a drop nozzle to get passed the foliage.”
He said a Poast-herbicide protected and Roundup ready sweet corn also are available to sweet corn growers.
Before applying any herbicide, please contact your local Extension agent or specialist to see if certain products are still available and read the label carefully.