Corn: Corn Rootworm (Diabrotica virgifera and Diabrotica barberi)

Excerpt from Chapter 2, Field Crop Protection Guide, Order this publication

Table of Contents

1. Description
2. Integrated Pest Management Options
   • Soil-Applied at Planting Only
     • tefluthrin – Force 3 G
     • chlorpyrifos – Lorsban 15 G, Pyrifos 15 G
     • phorate – Thimet 15 G
   • Seed Treatment
     • clothianidin – Poncho 1250
   • Transgenic
     • Herculex RW, Herculex Xtra, YieldGard RW, YieldGard Plus
3. Related links...

Description

There are two species of corn rootworm in Ontario. Western corn rootworm (WCR) adults are yellow to green with three, wavy black stripes on their wings. Northern corn rootworm (NCR) adults are uniformly green to yellowish. Larvae are white with a brown head and a distinct dark tail plate; they are approximately 1 cm in length.

Image 1. Western corn rootworm adults are yellow to green with three wavy black stripes on their back.

Image 2. Northern corn rootworm adults are usually green to yellow and have no stripes.

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Integrated Pest Management Options

Avoid planting corn on corn. Crop rotation is the best strategy for control. Risk factors include heavier soil (clay), high beetle populations in corn of previous season, being the latest field planted in the previous season.

If there is less than 1 beetle per corn plant on average throughout the month of August, then no insecticide is necessary in the following corn crop.

Soil-Applied at Planting Only

In-furrow application is safer to the applicator and non-target animals than T-band application.

Comments
May be applied in a T-band or in-furrow. For banded applications, place directly over the furrow in a 15-cm band ahead of the pres wheel. For in-furrow application, place all material directly in the open seed furrow, behind the planter disc openers.

Comments
Must be applied in a 10–15-cm band over the row behind the planter shoe, in front of the press wheel. Do not place in direct contact with seed.

Comments
Lock and load. Must be applied in a 10–15-cm band over the row behind the planter shoe, in front of the press wheel. Do not place in direct contact with seed.

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Seed Treatment

Seed treatments are best suited for those fields at high risk, especially corn after corn.

Comments
For use in commercial seed treaters only. Seed-applied insecticides can affect seed drop and final plant stands. Use talc or graphite according to planter recommendations to ensure accuracy.

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Transgenic
To manage potential rootworm resistance, plant a minimum of 20% of total corn acreage to non-Bt corn hybrids and position the refuge within or directly adjacent to the YieldGard Rootworm Bt corn field. Refuge can be treated for rootworm larvae with soil-applied insecticides if thresholds perscribe it. Insecticide use for adult control is not permitted. For more information regarding Bt corn and/or refuge options, see A Growers Handbook; Controlling Corn Insect Pests With Bt Corn Technology found on the Canadian Corn Pest Coalition website.

Herculex RW, Herculex Xtra, YieldGard RW, YieldGard Plus

See table 1 - 10, Transgenic Crops Expressing Insecticidal or Fungicidal Traits for Bt corn options.

Comments
Keep careful and accurate records as to where Bt and non-Bt hybrids are planted.

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Related links...

• Agronomy Guide for Field Crops - Publication 811
  • Corn: Corn Rootworm
• Transgenic Crops Expressing Insecticidal or Fungicidal Traits
• Insect
• Corn
• Canadian Corn Pest Coalition

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