How to Manage Pests

UC Pest Management Guidelines

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 exiguae by 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	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, pesticide registrations, information related to natural enemies and honey bees, and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
A.	CHLORANTRANILIPROLE
	(Coragen)	3.5–5 fl oz	4	1
	MODE OF ACTION GROUP NUMBER1: 28
B.	METHOXYFENOZIDE
	(Intrepid) 2F	4–10 fl oz	4	3
	MODE OF ACTION GROUP NUMBER1: 18A
	COMMENTS: Use allowed under a supplemental label.
C.	BACILLUS THURINGIENSIS ssp. AIZAWAI#
	(various products)	Label rates	4	0
	MODE OF ACTION GROUP NUMBER1: 11.B1
	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.
D.	INDOXACARB
	(Avaunt)	3.5 oz	12	3
	MODE OF ACTION GROUP NUMBER1: 22
E.	METHOMYL*
	(Lannate) 90	0.5–1.0 lb	48	see comments
	(Lannate) LV	1.5–3 pt	48	see comments
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: For use on cucumbers, melons, and summer squash. PHI is 1 day when 0.5 lb or less for 90SP or 1.5 pt or less for LV formulations is used; when more than 0.5 lb (90SP) or 1.5 pt (LV) is used, PHI is 3 days.
F.	SPINOSAD
	(Entrust)#	1.25–2.5 oz	4	1–cucumbers 3–other cucurbits
	MODE OF ACTION GROUP NUMBER1: 5
	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.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1	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 to help prevent the development of resistance. 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 Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
#	Acceptable for use on organically grown produce.
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

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

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