Persistent problems: Tough weeds, part 2

Editor’s Note: Read Part 1 now.

Broadleaf plantain (Photo: Syngenta)

Technical experts from Syngenta, FMC, Prime Source and Nufarm explain how to identify and control broadleaf plantain, spurge and doveweed.

Broadleaf plantain

A perennial that grows in a rosette pattern and features a wide, shiny elliptical leaf with veins running parallel with the margins, broadleaf plantain can be found throughout much of the U.S. It often has short stems that form a U, like a celery stalk. The plantains can be seen during the entire growing season and can survive drought conditions when grasses start to go dormant. It germinates in the spring.

It’s best controlled by common herbicides that contain 2,4-D or MCPA. Spring-applied herbicides often can desiccate above-ground foliage but do little to the below-ground structures, while fall-applied herbicides do a better job moving to the roots for a more effective kill.

Doveweed (Photo: Syngenta)

Doveweed

Doveweed is a summer annual that may resemble St. Augustinegrass and is most problematic in warmer climates. It produces stolons, which enable it to spread laterally, and clusters of small blue or purple flowers. The leaves are long and narrow, and on the stem, leaves appear in an alternate arrangement.

Doveweed germinates in late spring in southern states and becomes more conspicuous as it gets established by midsummer.

It thrives in poor-draining soil, so a healthy and dense turf canopy is the best cultural control. The key for postemergent control of doveweed is to make applications early before the plants have produced any stolons. It’s often necessary to make sequential applications about 14 days apart for complete control. Herbicides containing 2,4-D and dicamba can work well when applied sequentially and early. Spot sprays with ALS herbicides, those containing thiencarbazone and iodosulfuron, can be used to clean up misses later in the summer.

Prostrate spurge (Photo: Syngenta)

Spurge

Spurge is a summer annual that germinates after crabgrass. It’s a mat-forming weed that can root at the nodes. It’s often confused with common purslane but is much less succulent and exudes a milky white sap when the stems are broken. It has red stems and green leaves often with purple or maroon spots in the middle of each leaf. Flowers on mature plants form on the axils of upper leaves. Spurge can be found around sidewalks and driveways initially. It’ll tolerate low mowing, compacted sites and low fertility, so it’s pretty well adapted to lawns.

Because it’s a late summer annual, preemergent applications have likely dissipated by that point. A combination product that includes dicamba or triclopyr are effective against spurge. The leaves are small, so lawn care operators must make sure they have adequate coverage.

Sources: Dean Mosdell, Ph.D., technical services manager at Syngenta; Ken Hutto, Ph.D., product development manager for herbicides and fungicides for FMC; Bret Corbett, director of technical services for Prime Source; Aaron Hathaway, technical services manager for Nufarm.