Corn: Armyworm (TRUE - Pseudaletia unipuncta, FALL - Spodoptera frugiperda)

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

Table of Contents

1. Description
   • Integrated Pest Management Options
     • carbaryl – Sevin XLR Plus
     • cyhalothrin-lambda – Matador 120 E
2. Related links...

Description

True armyworms, full grown, are 4-cm (1 1/2-in.) dull-green to brown larvae that can be easily confused with other caterpillars, including variegated cutworm and fall armyworm. Two distinguishing features that true armyworm possess are white-bordered stripes running laterally along the body and dark diagonal bands at the top of each abdominal proleg. The head is yellow-brown with a network of dark brown lines creating a pattern. The adult sand-coloured moth has distinctive white spots on the centre of each forewing.

Image 1. True armyworm larvae have black bands at the top of each proleg and the lighter brown head.

Full-grown fall armyworms are 4 cm (1 1/2 in.) long, varying in colour from light tan or green to near-black. Three white, thin stripes run down the back with one thicker, yellow band with red spots running along the side, just above the legs of the larvae. Scattered along the body are black spots called tubercles that have spines coming from them.

Image 2. Fall armyworm larva damage on corn ear. Larvae leave entry holes on the exterior of ear. Note head is black wih a white, inverted "Y" on the front.

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Integrated Pest Management Options

Five to six larvae in an area 30 x 30 cm warrant chemical control. Treat if larvae <2.0 cm long and threshold has been exceeded. if larvae have white eggs attached to them, they are parasitized and may not need treatment. If larvae are 2.0 cm or larger, chemical control will not work well and is not recommended.

Comments
For larvae in whorls and foliage, treat entire plant. Repeat as necessary. For silks and ears, apply in 2-4-day intervals. 1 day to harvest. Follow label precautions regarding honeybees.

Comments
Ground or aerial application. Spray no later than 1st apperance of feeding. Spray no later than 14 days before silage harvest. No more than 3 applications per season, 2 may be by air.

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Related links...

• Agronomy Guide for Field Crops - Publication 811
  • Corn: True Armyworm
  • Corn: Fall Armyworm
• Insect
• Corn

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