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Insects Affecting Production of Native Legume Seed in the Great Basin
Bob Hammon
Tri River Cooperative Extension
Grand Junction CO
Jim CaneUSDA/ARS Bee Biology
& Systematics LabLogan UT
Insect Pests of Native Plants?
Economic considerations
“Natural controls”
Hedysarum borealeNorthern Sweetvetch
70%+ seed loss to seed weevils at Meeker CO 1990
Dalea ornata Western prairie clover
Seed weevils widespread!!
Lupinus argenteusSilvery Lupine
Significant weevil damage to seed in field collections
Astragalus filipesBasalt 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
BruchidaeAcanthoscelides
aureolus L X
daleae
fraterculus X X
oregonensis X
pullus X
BrentidaeApion
amaurum X
proclive L
oedorhychum L
CurculionidaeTychius
lineellus L
semisquamosus X
tectus X L X
Bruchidae – Seed WeevilsAcanthoscelides
o Head hypognathous (pointed downward)o Antennae arise from base of eyeo Tip of abdomen not covered by elytra
Acanthoscelides oregonensis
Most seed weevils we are dealingwith are < 2.5 mmIn length
2mm
Brentidae Curculionidae
Hollyhock weevilApion longirostre
Agave weevilScyphophrus acupunctatus
Weevil Larvae
• Found within seed pod– Root feeders
• May be within normal-looking 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 SeedDon’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
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