Annual sowthistle

Pest: Annual sowthistle (Sonchus oleraceus)

Pest Type: Annual Broadleaf Weed

Major Identifying Features: Alternate leaves, coarse, erect, can grow 4 feet tall, smooth stem, thick, milky sap, hairless leaves, daisy-like urn shaped flower heads, yellow flowers, fluffy seed heads (not ball shaped)

Life Cycle: Winter or summer annual, flowering in spring and summer, reproduces by seed

Pest Rating: Moderate

Management Rating: Difficult

Host/Season/Outbreak Information: Abundant in California, grows in winter and summer up to 4900 feet, can be found in Central Valley and coastal areas

Damage Information: Can harbour pests that are economically important to vegetable and fruit crops (lettuce aphid, lettuce root aphid, nematodes), common seed crop contaminant, compete for water and nutrients

Management Options: Prevention by hoeing, cutting before flowering, crop rotation, mechanical by hand pulling and grazing, biological control with rust fungus, chemical control with herbicides (species has developed resistance to ALS-inhibitors)

Sources:

http://www.cabi.org/isc/datasheet/50584

http://www.ipm.ucdavis.edu

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