Insects Affecting Production of Native
Legume Seed in the Great Basin
Bob Hammon
Tri River Cooperative Extension
Grand Junction CO
Jim Cane
USDA/ARS Bee Biology
& Systematics Lab
Logan UT
Insect Pests of Native Plants?
Economic considerations
“Natural controls”
Hedysarum boreale
Northern Sweetvetch
70%+ seed loss to
seed weevils at
Meeker CO 1990
Dalea ornata
Western prairie clover
Seed weevils widespread!!
Lupinus argenteus
Silvery Lupine
Significant weevil
damage to seed in
field collections
Astragalus filipes
Basalt Milkvetch
5 species of
weevils damaging
seed in 2003/04
Several root
boring weevils
reported from
Astragalus
2003 Astragalus collection sites
Weevils
• Curculionidae - True weevils
– Tychius (ASFI, HEBO, LUAR)
• Brentidae – Straight-snouted weevils
– Taxonomic confusion!!
• Curculionidae, Apionidae, Brentidae
– Apion (DAOR, LUAR)
• Bruchidae - Seed weevils
– Acanthoscelides (ASFI, HEBO, DAOR)
D. ornata A. filipes
H. boreale L. argenteus
Bruchidae
Acanthoscelides
aureolus
L
X
daleae
fraterculus
oregonensis
X
X
X
pullus
X
Brentidae
Apion
amaurum
X
proclive
L
oedorhychum
L
Curculionidae
Tychius
lineellus
L
semisquamosus
X
tectus
X
L
X
Bruchidae – Seed Weevils
Acanthoscelides
o Head hypognathous (pointed downward)
o Antennae arise from base of eye
o Tip of abdomen not covered by elytra
Acanthoscelides oregonensis
Most seed weevils
we are dealing
with are < 2.5 mm
In length
2mm
Brentidae
Hollyhock weevil
Apion longirostre
Curculionidae
Agave weevil
Scyphophrus acupunctatus
Weevil Larvae
• Found within seed pod
– Root feeders
• May be within normallooking seed
• Well developed head
capsule
• Legs reduced or absent
Tychius Life History
•
•
•
•
•
Feed on Fabaceae: Papilionoideae
Seed predators
Adults feed on flowers/ pollen
Oviposit in immature ovaries/pods
Larvae feed on several seeds within pod
– External feeders
• Pupation in soil
– Pupation in pods aberrant??
• Overwintering as adult in soil
Clark, W.E. 1977. The curculionid genus Tychius Germar: Natural history and coevolution
with leguminous host plants. Southwestern Entomologist 2: 106-124
Acanthoscelides Life History
•
•
•
•
Many species, host plants
Large diversity of life history
Oviposition on pods, some spp on seed
External or internal feeding on seeds, may
eat 1 seed completely before moving on
• Multiple generations for some species
• Silken cocoon against side of pod, some
spp within a seed
Handling Collected Seed
Don’t bring them home alive
•
•
•
•
•
•
Inspect seed for damage
Adult weevils on plant material
Larvae within seed
Inspect healthy-looking seed
Keep samples for ID
– Larvae for rearing to adult
Fumigate with No Pest Strip
– Cut into 1” strips
– 48h in sealed container
Management – Field Collection Sites
• Anticipate problems
• Monitor the site
– Sweep net
– Nocturnal samples
• Pre-bloom soil drench
– Bayer Advanced Tree & Shrub Insect
Control Concentrate
• Imidacloprid
– Cheap, readily available, easy to apply
Management – Field Plantings
• Monitoring with sweep net
– NOCTURNAL!!!!!
• Preventative controls
– Target adults pre-oviposition
• Systemic insecticide
– Prebloom imidacloprid
• Contact insecticide
– Residual pyrethroid
• Pollinator concerns
– Non-lethal effects
Seed Predator Challenges
• Research needs
• Many species
– Life history diversity
– Taxonomy challenges
– Geographic differences
• Widespread distribution
– Many legume plantings will be affected
• Yearly changes
– We don’t know what next years challenge is
Seed Production Pesticide Labels
• No labels for “Forbs grown for Seed”
• Field grown ornamentals
http://www.coopext.colostate.edu/TRA/SeedProduction.html
NativePlantIPM@colostate.edu listserv
Bob Hammon
Tri River Cooperative Extension
P.O. Box 20,000-5028
Grand Junction CO 81502-5028
(970) 244-1834
robert.hammon@colostate.edu