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