Field Bindweed Management in Drip Irrigated Processing Tomatoes

Subsurface drip irrigation in processing tomatoes (Solanum lycopersicum) has been rapidly adopted in California over the past decade, and is now used on approximately 90% of the production area. The economic necessity of maintaining the beds and replanting with only minimal tillage for multiple seasons has created a system where field bindweed (Convulvulus arvensis) has become more prevalent. Beginning in 2011, field studies were conducted at University of California Davis campus to evaluate the efficacy of registered herbicide combinations in controlling established field bindweed in processing tomatoes; parallel studies were conducted at the UC West Side Research and Extension Center using drip irrigation. The treatment design was a randomized block split-plot with four replications. Main plots consisted of pre-emergent and pre-plant incorporated (PPI) applications of pendimethalin, trifluralin, sulfentrazone, and rimsulfuron at label rates. Split-plot treatments were post-emergent applications of rimsulfuron or carfentrazone, applied after transplanting to emerged bindweed. Concurrently, additional herbicide treatment combinations included sequential post applications of rimsulfuron, carfentrazone, or carfentrazone + glyphosate; trifluralin applied PPI and again at lay-by, sulfentrazone + S-metalochlor PPI, trifluralin + S-metalochlor + rimsulfuron combination, as well as untreated and hand weeded controls. Overall, trifluralin was the most effective pre-emergence treatment for suppressing established field bindweed, however, this effect was not significantly different than the other treatments or the untreated control by the end of the season. Post-emergent applications of rimsulfuron and carfentrazone significantly improved bindweed control about 21% in most instances. The combination of trifluralin PPI and either rimsulfuron or carfentrazone applied post emergence, or applying trifluralin both pre and at layby, have been the best treatments for controlling field bindweed in these trials, with bindweed control of 50-80% compared to the untreated control. No significant differences were noted for tomato crop growth or yield; however, concerns remain about this herbicide program for its potential crop phytotoxicity and plant-back restrictions.