Pest Management Guidelines
Special Weed Problems
(Reviewed 6/09, updated 6/09)
BERMUDAGRASS. Bermudagrass is a vigorous spring- and summer-growing perennial that grows from seed but can also be spread during cultivation and incorporation procedures from its extensive system of rhizomes and stolons. It is very competitive with asparagus for moisture, nutrients, and light. Its presence in cutting beds interferes with spear harvest. If bermudagrass develops in the head or tail ends of a field or in localized areas, spot treat it with glyphosate and/or fluazifop-p-butyl (Fusilade) immediately to prevent the spreading of vegetative propagules.
FIELD BINDWEED. Field bindweed is a vigorous perennial weed that either grows from seed, which can survive for up to 30 years in the soil, or from stolons, rhizomes, or extensive roots. Due to the longevity of the seed, it is critical to destroy plants before they can produce seed. The plants may be spread vegetatively through stem or root sections during cultivation or incorporation operations. If field bindweed appears in or around the field, spot treat it with high label rates of trifluralin to prevent it from spreading.
JOHNSONGRASS. Johnsongrass is a perennial weed that spreads from seed or from an extensive system of underground rhizomes. It grows vigorously in spring and summer when it overtops the fern and competes for light, moisture, and nutrients. It interferes with harvest by providing a physical barrier to cutting. If johnsongrass develops in or around the field, spot treat it with glyphosate or sethoxydim to prevent the spread of its rhizomes.
NUTSEDGE. Yellow and purple nutsedge are perennial weeds that commonly reproduce from underground tubers that survive for 2 to 5 years in the soil. The tubers are easily spread by cultivation equipment and power incorporators. Each tuber contains several buds that are capable of producing plants. One or two buds germinate to form a new plant; however, if destroyed by cultivation or an herbicide, then a new bud is activated. Control is best accomplished by continuous cultivation during a summer fallow period before planting an asparagus field. On sandy soils in the San Joaquin Valley, purple nutsedge populations can be significantly reduced but not eradicated by dry fallowing for 5 to 6 weeks. If nutsedge develops on the edges of established fields, spot treat it with glyphosate to prevent new infestations from becoming established in the field.
SWAMP SMARTWEED. Swamp smartweed, also known as swamp knotweed, is a deep-rooted perennial weed that is particularly a problem in poorly drained fields. It produces a substantial amount of seed, and once established is very difficult to control due to its deep fleshy taproot. It can regenerate from this root even though the top of the plant is severed by cultivation. The thick taproot also poses a problem at asparagus harvest, interfering with the cutting of the asparagus spears. If swamp smartweed is a problem, clear cut the spears and treat with dicamba to burn back this weed.
UC IPM Pest Management Guidelines: Asparagus
Acknowledgment for contributions to Weeds: