Common Stalk Borer

Amy Timmerman, Extension Educator Author

09/12/2023 Added

2 Plays

Description

Scouting for common stalk borer larvae in corn should start in the next 1-2 weeks. Stalk borers are an occasional pest of corn in Nebraska. Stalk borer damage in corn commonly is confined to plants in the first few rows near field margins, fence rows, grass terraces and waterways.

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[00:00:00.224]I am Amy Timmerman with Nebraska Extension and this week's Extension update.
[00:00:04.435]Scouting for common stalk borer larvae in corn should start in the next 1to 2 weeks.
[00:00:09.385]Stalk borers are an occasional pest of corn in Nebraska.
[00:00:13.105]Stalk borer damage in corn commonly is confined to plants in the first few rows
[00:00:16.875]near field margins, fence rows, grass terraces and waterways.
[00:00:20.935]In addition to attacking corn, stalk borers attack over 100
[00:00:24.094]other species of plants, including ornamentals,
[00:00:27.574]garden vegetables, broadleaf weeds, and grasses.
[00:00:30.094]They may feed on soybeans as well, but they are not an economically
[00:00:33.566]important pest of soybeans.
[00:00:35.796]Female stalk borer moths lay their eggs primarily on
[00:00:39.196]grasses such as smooth brome or ragweed in late summer and early fall.
[00:00:43.196]Small grains such as rye or wheat
[00:00:44.911]planted as a cover crop may also be a potential egg laying site.
[00:00:49.146]Egg-laying sites usually are in fence rows, terraces, and waterways,
[00:00:52.976]but can be found throughout a field if preferred hosts are available.
[00:00:56.976]Eggs overwinter and hatch in late April or early May.
[00:01:00.286]Larvae bore into the stalks of grasses or other hosts
[00:01:03.636]such as ragweed and begin feeding.
[00:01:05.646]As they become larger or if the plants are mowed,
[00:01:08.216]terminated mechanically or burned down with herbicides,
[00:01:11.176]the stalk borers migrate into adjacent corn plants to complete their development.
[00:01:15.176]In some cases, if an appropriate weed host
[00:01:18.126]is not available when eggs hatch, stalk borers may begin feeding directly on corn.
[00:01:23.335]Corn between the two- and eight-leaf stages can be attacked by the
[00:01:26.705]migrating stalk borer larvae.
[00:01:29.005]Larvae develop through seven to 10 instars, or stages, in about 10 weeks.
[00:01:33.447]Pupation occurs in the soil and moths emerge in August, September and early October.
[00:01:38.797]There is only a single generation per year.
[00:01:41.621]Common stalk borer larvae are distinctive in appearance.
[00:01:44.916]Young larvae are brownish-purple and have three prominent longitudinal
[00:01:48.646]white stripes at the front and rear ends of the body.
[00:01:51.773]The stripes are interrupted at mid-body by a solid dark purple to black area
[00:01:56.563]on the third thoracic segment and first three abdominal segments.
[00:02:00.423]Fully grown larvae do not have the characteristic markings
[00:02:04.013]and are uniformly dirty gray in color.
[00:02:06.303]Full grown larvae can be 1 1/2 to 2 inches long.
[00:02:09.843]Stalk borer larvae injure corn plants typically in late May-June.
[00:02:15.360]They feed on leaves in the whorl and then tunnel into the stalk,
[00:02:18.510]or they burrow into the base of the plant
[00:02:20.575]and tunnel up through the center of the stalk.
[00:02:22.720]Leaf feeding alone does not cause economic damage.
[00:02:26.049]Stalk borers hatch and migration to new hosts
[00:02:28.939]can be predicted using degree days.
[00:02:31.088]Based on research at Iowa State University,
[00:02:34.073]stalk borer egg hatch begins at about
[00:02:36.045]575 degree days and ends at 750 degree days.
[00:02:40.856]We begin scouting corn when 1,300-1,400 DD have accumulated.
[00:02:49.156]This corresponds with the beginning of larvae moving out of grassy hosts.
[00:02:53.405]The determine of the needs of treatment
[00:02:57.380]when we are at 1,400-1,700 degree days have accumulated.
[00:03:01.356]As of today, June 8th we are currently at 1,252 degree days which indicates
[00:03:07.510]that stalk borer larvae will begin moving into corn the next 1 to 2 weeks
[00:03:12.903]and that scouting should begin.
[00:03:15.050]Making management decisions on that corn is not until we hit
[00:03:19.210]1,400-1,700 degree days of accumulated degree days.
[00:03:24.610]You can receive updated degree data daily.
[00:03:27.025]It's available at Iowa State University mesonet.
[00:03:30.686]Just google that and you will be able to find the information.
[00:03:34.356]Refer to Economic Threshold Tables
[00:03:36.221]and Management Options are available at cropwatch.com or
[00:03:39.618]reach out to your local extension office for more information.
[00:03:42.776]This has been Amy Timmerman with Nebraska Extension.

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Common Stalk Borer

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