How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Larvae are usually dull green and have wavy, light-colored stripes running lengthwise down the back and broader stripes on each side. Eggs are laid in a mass covered with hairlike scales.

DAMAGE

Primarily a foliage feeder, the beet armyworm will also attack fruit, creating single or closely grouped circular or irregular holes. In many cases, feeding is superficial and little loss would result if not for decay organisms that enter wounds and rot fruit. The caterpillars occasionally develop inside the fruit.

MANAGEMENT

While populations of this pest tend to build up in alfalfa and weedy areas around the field, beet armyworm only needs to be controlled if it is feeding on the crop. Keep crop residue and weeds in field and surrounding areas to a minimum to lessen the attraction of the field.

Biological Control
The parasitic wasp, Hyposoter exiguae, is important in controlling populations of this pest. Beet armyworm larvae can be easily checked for the presence of this wasp by pulling the larva apart and looking for the parasite larva.

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

Monitoring and Treatment Decisions
Beet armyworm may be present in and around the field feeding on bindweed and little mallow (malva). Monitor foliage for small larvae and treat before fruit damage occurs. Treat only if armyworm feeding is observed on fruit.

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: Time spray to target eggs and small larvae. Do not apply more than 4 applications/acre/season or spray at less than 7 day intervals. Use allowed under a supplemental label.
B.	SPINOSAD
	(Entrust)#	1.25–2.5 oz	1–cucumbers 3–other cucurbits
	(Success)	4–8 fl oz	1–cucumbers 3–other cucurbits
	MODE OF ACTION: A microbial (Group 5)1 insecticide.
	COMMENTS: Time spray to target eggs at hatch or small larvae. Do not apply more than 9 oz Entrust or 29 fl oz of Success/acre/season.
C.	BACILLUS THURINGIENSIS ssp. AIZAWAI#
	MODE OF ACTION: A microbial (Group 11.B1)1 insecticide.
	(various products)	Label rates	0
	COMMENTS: Use to control small armyworms only (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 another material.
D.	METHOMYL*
	(Lannate) 90SP	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 only.
*	Permit required from county agricultural commissioner for purchase or use.
+	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/.
#	Acceptable for use on organically grown produce.

PUBLICATION

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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