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A field full of dandelions during sunset.

Parasitic Weed

Participants of Weed Day 2026 labeling types of weeds in a field.

Weed Day 2026

  • by Sam Romano

It's finally June, so it's time for another Weed Day!

Earn up to 5.0 hours of "Other" CEUs through the California Department of Pesticide Regulation by attending Weed Day 2026.

Weed Day is a showcase of the latest weed science research at the University of California. This year, we'll have demonstrations of a variety of weed control technologies during the morning field tour. After a buffet lunch and open discussion period, we'll have presentations in the afternoon for research projects that are either off-season or too far from campus for viewing.

Field Chemigation for Branched Broomrape Management in California Processing Tomato

  • by Rohith Vulchi and Brad Hanson

Branched broomrape (Phelipanche ramosa) poses a significant challenge to processing tomato production in California. Unlike many other weeds growers manage, broomrape spends nearly 70% of its entire life cycle underground attached directly to tomato roots, before ever becoming visible. By the time shoots emerge above the soil surface, the plant has already been established belowground for weeks. Once it emerges, it can flower and produce seed within a couple of weeks.

The Broomrape GDD Calculator for Scheduling Chemigation and Rogueing Operations in California-grown Processing Tomatoes

  • by Rohith Vulchi and Brad Hanson

Branched broomrape is a parasitic weed that continues to challenge processing tomato production in California. Nearly 70% of its lifecycle is completed underground; once it emerges, it can flower and set seed within just a few weeks. Current best management practice recommendations for broomrape management in conventional processing tomatoes includes a herbicide treatment regime to control early-stage broomrape at the time of root attachment and removal of emerged plants before they set seed.

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