Greenhouse Evaluation of Napropamide and Pendimethalin for Suppression of Strawberry Daughter Plant Rooting and Runner Management Implications

In plasticulture strawberry systems where growers intend to maintain plantings into a second harvest season, stolons (runners) are undesirable because they produce daughter plants that divert resources from the mother plant and complicate field maintenance. Manual runner removal is labor-intensive, and removal becomes more challenging once daughter plants have rooted in the row middles. Napropamide and pendimethalin were evaluated in greenhouse studies to assess their potential to suppress daughter-plant rooting and facilitate runner removal. Greenhouse studies used a threepot experimental unit consisting of one strawberry mother plant with two runners, each bearing one unrooted daughter plant, and two side pots simulating row middles. Three simulated herbicide application treatments were evaluated, including broadcast (foliar + side pot spray), in-row (foliar spray only), and row-middle (side pot spray only) applications, and were compared against a nontreated control. On mother plants, napropamide caused transient foliar injury but did not affect runner production or biomass. On daughter plants, napropamide caused transient injury and suppressed new growth at 4 wk after treatment (WAT), reducing daughter-plant biomass by 59–68%. Napropamide also eliminated the pull force required for removal relative to the nontreated control and reduced above- and belowground biomass up to 49% and by >95%, respectively, demonstrating effective suppression of runner establishment by reducing daughter plant rooting. However, suppression was transient; by 8 WAT, only the broadcast treatment consistently maintained rooting inhibition, likely due to herbicide degradation over time. Pendimethalin caused no effects on mother plants or daughter plants under any application method and failed to inhibit daughter plant rooting entirely. These results suggest that napropamide applied to the row middles, the only label-compliant method evaluated, can effectively suppress daughter plant rooting for at least one month, providing growers with a supplementary benefit of eased runner removal during summer weed management.