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Channel Field Check Up
KAYLISSA HALTER
EFFINGHAM, ILL.
When inspecting corn midseason for insect damage, it is important to look for plant symptoms and the insects present.
Corn rootworm
In 2014, corn rootworm hatch was confirmed during the first week of June by researchers at Purdue University1. After hatching, newly emerged larvae begin feeding on root hairs. As they grow, they tunnel into roots and can chew them down to the base of the plant causing damage to plant vascular and structural systems. Although larvae are the most destructive lifecycle of the corn rootworm, adults also can damage the corn crop. Beetle feeding results in long, narrow strips on corn leaves that turn light gray, and leaves with heavy feeding may split or fray. After R1 begins, beetles also can feed on emerging corn silks, which may affect corn pollination if cutting is severe. Scouting for larval feeding typically begins from July to August and consists of evaluating the nodal root system.
European corn borer
European corn borers (ECB) can injure the plant in many ways. Newly hatched larvae usually feed deep within the whorl, removing shallow layers of leaf tissue creating thin ‘windows’ in leaf tissue. As they grow, larvae can chew through leaves completely; emerging leaves may exhibit ‘shot hole’ patterns where feeding occurred. The ECB larvae also can tunnel into leaf midribs, leaf collars, and later, into ear shanks. This boring may damage vascular tissues, disrupting the flow of water, sugars and nutrients.
Armyworms
True armyworms (TAW) remove tissue from the edges of leaves often eating everything but the midrib. Feeding begins on lower leaves and progresses upward, affecting whorl leaves last. The larvae are easily found on plants, and many may feed upon the same plant. Fall armyworm (FAW) larvae feed deep inside the whorl, leaving behind large, ragged-edged holes in whorl leaves. Holes may be 1 or 2 inches across and often mirror each other on opposite leaves that have emerged from the whorl. Severe feeding may resemble hail damage.
Common stalk borer
Common stalk borer damage to corn appears as large, ragged holes in leaves caused by feeding inside the whorl. When holes are several inches long, the leaves can break or be cut from the plant. Affected plants may grow abnormally, being twisted or bent over, and may not produce an ear. Common stalk borer larvae exhibit distinct longitudinal white stripes interrupted by a purple midsection and an orange head with a black stripe.
If specified damage or insects are present, contact your Channel Agronomist or Seedsman for details on threshold and control measures that may apply.
http://www.channel.com/agronomics/Pages/Mid-Season-Insect-Identification-in-Corn.aspx
1Krupke, C. and L. Bledsoe. 2014. Rootworm hatch underway. Pest and Crop. Purdue University. http://extension.entm.purdue.edu. ∆
KAYLISSA HALTER: Agronomist, Channel Seed
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