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43. Spot-treat Insect Infestations When Possible

Stalk borers

Stalk borers, wireworms, grasshoppers, and twospotted spider mites are pests that may be managed by spot treatment. This way, you avoid treating an entire field with insecticide.

Stalk borers often lay eggs during the summer in fencerows, grass conservation lanes, or grassy terraces. When corn is planted next to these areas during the following spring, there is a risk that stalk borer larvae will move from the grassy areas and infest the crop.

larvae By using sprays along field edges, larvae may be killed as they move from weeds to young corn plants. If you miss this chance, and if the stalk borer larvae do infest the small corn plants, it is usually too late to do anything except consider replanting the infested area of the field.
wireworms Wireworms tend to cluster in bottomlands, low spots, or other unique areas in fields. The greatest potential for wireworm infestation is in fields in which small grain or grasses have been grown for two or three years.
Wireworm Bait Sation To determine if you should spot-treat or treat the entire field, set bait stations two to three weeks before planting corn. If you find one or more wireworms in each trap, you may have to treat the entire field. But if some traps are empty and others have several wireworms, you may be able to limit your treatment to the areas where you found the infested traps.
grasshopper The primary grasshopper species in most of the Midwest lays eggs in the late summer and fall in noncrop areas, such as roadsides, fencerows, and field edges. After the eggs hatch in spring, grasshopper nymphs feed in noncrop areas for roughly 40 to 60 days.
grasshopper This is the time when grasshoppers can be managed easily by spot-treating the noncrop areas. If populations reach 15 to 20 per square yard, consider spraying the noncrop areas.
Treating for spider mites Spider mites usually overwinter in grassy areas in field margins. When their numbers build up during hot, dry weather, they may move from these border areas into the field edges. Spot-treating border rows and other infested areas before the spider mites move farther into a field often is the best way to handle them. However, treating the entire field may eventually be necessary in periods of prolonged drought.

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