How to Manage Pests
UC Pest Management Guidelines
Armyworm: Mythimna (= Pseudaletia) unipuncta
yellowstriped armyworm: Spodoptera praefica
In this Guideline:
The armyworm is pale green when young; as they mature they become
greenish brown to black with a yellowish stripe along each side. Young larvae
move like loopers, arching their body into a loop as they crawl. Western
yellowstriped armyworms are
black with yellow or orange stripes along the side. Mature larvae of both
species may reach 2 inches in length.
Larvae of both species cause damage by eating leaves. Entire leaves
may be consumed or damage may consist of notches chewed out of the leaves giving them a tattered look. Damage may occur when larvae
hatch from eggs laid in the cereal crop or from larvae migrating into the cereal crop from an
Armyworms are attacked by a parasitic wasp, Hyposoter sp. Parasitized worms can be identified by
pulling the larvae apart and looking for the green parasite larvae that pop
out. Hyposoter is usually
not active in early spring when cereals may be attacked by armyworms but
growers should check for its presence. Virus diseases of armyworms may also be
important natural control agents. Diseased caterpillars first appear yellowish
and limp, and after death hang from plants as shapeless, dark tubes from which
the disintegrated body contents ooze.
Organically Acceptable Methods
Biological and cultural controls and sprays of Bacillus thuringiensis.
are moving into the cereal crop from an adjacent crop, some control may be
obtained by plowing a deep, wide ditch between the two fields and keeping it
filled with water until the migration stops.
fields periodically for the presence of armyworms. Larvae hatching from eggs
laid in the field may be found throughout the field. Those migrating in from an
adjacent crop will most likely be found at the edge of the field.
threshold levels have been established for armyworms. Fields should be treated
if armyworm numbers are sufficient to cause defoliation. Small caterpillars,
less than 0.5 inch long, are easier to kill than larvae over 0.5 inch in
|The following materials are listed
in order of usefulness in an IPM program, taking into account efficacy, information
relating to natural enemies and honey
well as the environmental impact. Not all registered pesticides are listed. Always read label of product being used.
||MODE OF ACTION GROUP NUMBER1: 1A
||COMMENTS: May be used on barley, rye,
oats, and wheat. Do not graze within 10 days. Do not apply more than 1.8 lb
a.i./acre/crop. Highly toxic to honey bees if bees are present at treatment time or within a day after.
||MODE OF ACTION GROUP NUMBER1: 1B
||COMMENTS: May be used on barley, oats, and
wheat. This product is highly toxic to foraging bees, young hive bees, and
brood. Do not apply to any field when bees are present or in the surrounding vicinity. Do not graze within 15 days.
||BACILLUS THURINGIENSIS ssp. KURSTAKI#
||MODE OF ACTION GROUP NUMBER1: 11.B2
||COMMENTS: Effective only on larvae less
than 0.5 inches long. This material can be applied at any time with reasonable safety to bees.
UC IPM Pest Management Guidelines: Small Grains
UC ANR Publication 3466
Insects and Mites
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
L. D. Godfrey, Entomology, UC Davis
Acknowledgment for contributions to Insects and Mites:
D. Gonzalez, Entomology, UC Riverside
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