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Corn: Potato Stem Borer
Excerpt from Agronomy Guide for Field Crops (Chapter 3) Order OMAFRA Publication 811: Agronomy Guide for Field CropsTable of Contents
DescriptionLarvae are light purple to pink, aproximately 4 cm (1 1/2 in.) in length when mature (see Plate 22 on Page 277). Adults are brown moths that are active during August and September. PLATE 22. Potato stem borer larva emerging from base of corn stalk. Damage is usually concentrated in border rows. | Top of Page | Life HistoryThis pest of corn is more sever in the eastern counties, but infestations occur throughout the province. There is one generation per year. This pest overwinters as eggs in grasses. Eggs are laid in two or three parallel rows under the leaf sheath. These hatch in late April, and the small larvae initially bore into the stalks of grass plants. By late May, the larvae outgrow the grass stalks and move to nearby thicker stalk crop such as corn. These larvae continue to feed until late June, pupate and emerge as adults in late July.DamageLarvae are the only damaging stage. Damage is usually nost severe at field edges or near grassy, weedy areas. Larvae feed on plants in late May or early June. On young plants, the larva will burrow into the base of the plant, below the soil line. Plants may be cut at the base, similar to cutworm injury. At the three- or more leaf stage, they feed inside the whorl at the base of the corn plant, causing the upper one or two leaves to wilt, while the lower part of the plant remains healthy. Fields at higher risks include grassy or weed-infested fields of previous year, fields following sod and conservation-till fields. Scouting TechniqueUsually found within the stem or in soil near the base of the plant. Look for potato stem borers along fencerows or in grassy areas. Action ThresholdNo action threshold are available at this time. | Top of Page | Management StrategiesThere is no effective or economic chemical control for these insects since the borer remains inside the plant and is protected. Good weed control this year (especially of grassy weeds) will reduce the risk of damage next year. Fall plowing or burndown can reduce the number of eggs to overwinter. There are parasitic wasps that generally keep this pest below economically damaging levels. Updates on Corn: Potato Stem BorerRelated links...| Top of Page | For more information:Toll Free: 1-877-424-1300 Local: (519) 826-4047 E-mail: ag.info.omafra@ontario.ca |
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