Branched broomrape management is of increasing concern to California processing tomato growers. Field research was conducted in 2023 and 2024 to evaluate various application timings of chemigated rimsulfuron alone, preplant incorporated (PPI) sulfosulfuron paired with chemigated rimsulfuron, as well as foliar maleic hydrazide alone and paired with PPI sulfosulfuron and chemigated rimsulfuron. In 2023, all treatments with 70 g ai ha-1 rimsulfuron, alone or paired with PPI sulfosulfuron, reduced broomrape emergence 77 to 92% compared to the nontreated control. In 2024, broomrape pressure was higher, and all rimsulfuron treatments reduced broomrape emergence 68 to 86% compared to the control. In both years, five applications of foliar maleic hydrazide reduced broomrape emergence through at least midseason. The 2024 experiment included a combination treatment of PPI sulfosulfuron, chemigated rimsulfuron, and foliar maleic hydrazide, which resulted in fewer than four broomrape clusters per plot. In a 2024 grower-scale demonstration trial, two application regimes totaling 70 g ai ha-1 of chemigated rimsulfuron reduced broomrape emergence 83 to 89% compared to the control. Overall, chemigated rimsulfuron applied at various timings and rates totaling 70 g ai ha-1 reduced broomrape emergence by two-thirds or more compared to the nontreated plots. No crop injury was observed in trials with rimsulfuron, sulfosulfuron, or maleic hydrazide treatments in small plot trials or with rimsulfuron in the grower-scale demonstration trial. Under a recently approved 24(c) Special Local Need label, California growers can use three applications of rimsulfuron applied via chemigation to suppress broomrape in known infested fields or to reduce the risk of broomrape establishment in fields of concern for this quarantine pest. Promising results from sulfosulfuron and maleic hydrazide suggest that registering additional herbicides could help develop even more robust branched broomrape management programs.

Drip-applied herbicides provide farmers with a more timely and cost-effective approach for applying PRE herbicides; however, herbicide movement is often limited. Field studies were conducted evaluating drip-application methods for applying PRE herbicides under polyethylene-mulched beds on yellow nutsedge punctures and the corresponding responses of a tomato crop (height and yield). The experiment was a factorial treatment arrangement of three drip application methods and three PRE-applied herbicides [halosulfuron (54 g ai ha−1), S-metolachlor (1.4 kg ha−1), and fomesafen (280 g ha−1)]. Herbicides were applied either immediately following saturation of the planting beds (method A), over an extended period while saturating the beds (method B), or prior to bed saturation (method C). Additional treatments included a commercial standard (S-metolachlor sprayed to the bed surface prior to mulch application) and a nontreated control (polyethylene mulch only). Drip-applied fomesafen, halosulfuron, and S-metolachlor provided similar control of yellow nutsedge, produced comparable yields, and failed to elicit any negative growth responses when compared to our commercial standard. With the exception of nutsedge punctures counted 56 DAT, application method did not influenced measurable outcomes. At 56 DAT nutsedge punctures were significantly lower in treatments applied by method B compared to those applied with method A.