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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Adults of (left top to bottom) variegated cutworm, beet armyworm, cabbage lopper, (right top to bottom) tomato fruitworm (=corn earworm, cotton bollworm), tobacco budworm, western yellow striped armyworm.

Cucurbits

Yellowstriped Armyworm

Scientific Name: Spodoptera ornithogalli

(Reviewed 11/05, updated 11/05)

In this Guideline:

DESCRIPTION OF THE PEST

Larvae of the yellowstriped armyworm are almost black, with two prominent and many fine, bright yellow stripes on the side.

DAMAGE

Yellowstriped armyworm eats both foliage and fruit. It does not enter the fruit, but feeds on the surface, causing irregular holes. Infestations are most severe from July to mid-September.

MANAGEMENT

This insect is not a serious pest every year but is very destructive on occasion. Infestations originate from moths or caterpillars that migrate from alfalfa fields when the alfalfa is cut. Cleaning up crop residue and weeds in field and surrounding areas may lessen attraction of the field to the pest.

Biological Control
Many natural enemies attack armyworms. Among the most common parasites are the wasps, Hyposoter exiguae and Chelonus insularis, and the tachinid fly, Lespesia archippivora. Yellowstriped armyworm can easily be checked for the presence of Hyposoter exiguaeby pulling the larva apart and looking for the parasite larvae. Viral diseases also kill significant numbers.

Organically Acceptable Methods
Sanitation in the field and surrounding areas along with cultural control and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable to use in an organically certified crop.

Monitoring and Treatment Decisions
If young instars (or stages) of the yellowstriped armyworm are found on foliage during routine field inspections, consider treating with a low impact product such as Bacillus thuringiensis, methoxyfenozide (Intrepid), or spinosad (Entrust). For older stages of this armyworm, use methomyl.

Common name Amount/Acre P.H.I.+
(trade name)   (days)
When choosing a pesticide, consider information relating to water quality and impact on natural enemies and honey bees.
       
A. METHOXYFENOZIDE    
  (Intrepid) 2F
4–10 fl oz
3
  MODE OF ACTION: An insect growth regulator (Group 18)1 insecticide.
  COMMENTS: Use allowed under a supplemental label.
       
B. BACILLUS THURINGIENSIS ssp. AIZAWAI#
  (various products)
Label rates
0
  MODE OF ACTION: A microbial (Group 11.B1)1 insecticide.
  COMMENTS: Bacillus thuringiensis may be used to control small armyworms (first and second instar) when populations are light and full coverage sprays are applied. Repeat treatment as necessary. If mature larvae or heavy populations are present, use one of the other materials listed.
       
C. METHOMYL*    
  (Lannate) 90
0.5–1.0 lb
1 (less than 0.5 lb)
     
3 (0.5 lb or higher)
  (Lannate) LV
1.5–3 pt
1 (less than 1.5 pt)
     
3 (1.5 pt or higher)
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: For use on cucumbers, melons, and summer squash.
       
D. SPINOSAD    
  (Entrust)#
1.25–2.5 oz
1–cucumbers
3–other cucurbits
  MODE OF ACTION: A microbial (Group 5)1 insecticide.
  COMMENTS: Not as effective on yellowstriped armyworms as other insecticides listed. Apply to small armyworms (first and second instars). Time spray to target eggs at hatch or small larvae. Do not apply more than 9 oz Entrust/acre/season.
       
+ Preharvest interval. Do not apply within this many days of harvest.
1 Modes of action are important in preventing the development of resistance to pesticides. Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode of action is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445
Insects and Mites
R. L. Coviello, UC Cooperative Extension, Fresno Co.
E. T. Natwick, UC Cooperative Extension, Imperial Co.
L. D. Godfrey, Entomology, UC Davis
C. B. Fouche, UC Cooperative Extension, San Joaquin Co.
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
J. J. Stapleton, UC IPM Program, Kearney Agricultultural Center, Parlier
Acknowledgment for contributions to the insect and mite section:
J. B. LeBoeuf, AgriData Sensing, Inc., Fresno
M. Murray, UC Cooperative Extension, Colusa/Glenn counties

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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