Northwest berry Foundation

Management Detail

Armyworms/Climbing cutworms

in Raspberries

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Latin name: Many species

Description:

Reasons for Concern:
1) Potential harvest contaminant (especially in machine harvested fields) that can go undetected until late summer.
2) Infestations are usually spotty within a field.
3) Feeding can cause significant defoliation and reduce yields, but doesn’t generally cause economic damage.

Identification/Symptoms:
Early season cutworms are a rare problem. Larvae may be present as buds swell and open and feed at night on primary buds and new growth. Cutworms and armyworms are the caterpillars of several species of night-flying moths. Plump, smooth and often, greasy-looking with greenish, brownish, grayish, or striped bodies up to 1 ¾”long, cutworms curl up tightly when disturbed. About the same size, armyworms are plump, sparsely-haired, and generally green to brown with dark longitudinal stripes running down the sides and back. Armyworms lay white or greenish eggs masses that darken as they near hatching.

Life cycle:
Adult cutworm and armyworm moths appear between April and July. Females lay about 500 eggs on lower grass leaves over a 2- to 3-week period. A 2nd or 3rd generation of cutworms may emerge in summer and early fall. Mid-fall, cutworm larvae stop feeding and seek concealed areas for winter. Armyworms feed for 3 to 4 weeks, and are full grown at 1½ to 2”long. Armyworm larvae have 6 growth stages, or instars. The final instar lasts about 10 days, during which armyworms consume large amounts of plant material. Although damage is similar, cutworms are usually solitary feeders. High populations and food scarcity cause armyworms to move as a group, feeding indiscriminately on plants. Variegated cutworms are also known to march like armyworms when populations are high. Some species overwinter as a naked pupa in the soil, while some continue to develop through winter.
[Photo by Shelia Fitzpatrick]

Links:

Scouting:

  • Armyworms and cutworms can be a significant component of insect harvest contaminants. Before harvest, sample field with a beating tray and look for feeding damage on foliage to determine size of population.
  • Cutworms are not typically evenly distributed across a field; they are usually found in "hot spots".
  • Ride harvesters to identify cutworms on the belt.
  • Train workers on harvesting machines to remove them. Keep a container for the workers to put insect contaminants noting the locations in the field that they were found. This can be used monitor their numbers.
  • A preharvest insecticide application may be necessary if populations of harvest contaminant species are significant.

 
Cultural Controls:

    Conserve natural predators such as predatory ground beetles (carabids).

 

For information about chemical controls, check with our Pesticide Guide.

images


Bertha armyworm - photo by J. Troubridge, AAFC


Armyworm - photo from Iowa State University


Zebra caterpiller - photo by J. Troubridge, AAFC


Zebra caterpiller eggs - photo by K. Gray


Looper - photo by W. McDiarmid


Cutworm damage - photo by A. Antonelli

 

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Northwest Berry Foundation

Northwest Berry Foundation

© 2016

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