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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #317094
Title: Weed management in transplanted lettuce with Pendimethalin and S-metolachlor

Author
item LATI, RAN - University Of California
item Mou, Beiquan
item RACHUY, JOHN - University Of California
item SMITH, RICHARD - University Of California - Cooperative Extension Service
item DARA, SURENDRA - University Of California - Cooperative Extension Service
item DAUGOVISH, OLEG - University Of California - Cooperative Extension Service
item FENNIMORE, STEVEN - University Of California

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2015
Publication Date: 11/25/2015
Citation: Lati, R.N., Mou, B., Rachuy, J.S., Smith, R.F., Dara, S.K., Daugovish, O., Fennimore, S.A. 2015. Weed management in transplanted lettuce with Pendimethalin and S-metolachlor. Weed Science. 29:827-834.

Interpretive Summary: There are few available herbicides for lettuce that do not provide adequate weed control, and hand weeding is required for commercially acceptable weed control. There is a need for additional herbicides tools for growers. Here we report field evaluations of pendimethalin and S-metolachlor herbicides for weed control in transplanted lettuce. Both pendimethalin pre-emergence (PRE) and post-emergence (POST) applications were safe to transplanted lettuce and provided similar weed control. Pendimethalin PRE at rates of 1.1 kg per hectare and higher provided better weed control than the industry standard, pronamide. Pendimethalin applied at 1.1 kg per hectare PRE or POST improved weed control by 57% and 42%, respectively compared to pronamide. S-metolachlor at rates up to 2.8 kg per hectare caused little or no crop injury or yield reduction in transplanted lettuce, and S-metolachlor at rates of 1.4 kg per hectare and higher improved weed control compared to pronamide. S-metolachlor PRE at 0.7 kg per hectare was less effective on weed control than pendimethalin, but maintained a similar weed control level as pronamide. Pendimethalin and S-metolachlor are not yet labeled for transplanted lettuce, and we recommend that labeling should be pursued at rates of 1.1 and 0.7 kg per hectare, respectively. Pendimethalin and S-metolachlor have potential for use in transplanted lettuce production and provide adequate alternatives for pronamide. Results from this study can contribute to successful integration of more herbicides into currently used weed-management systems for lettuce, which in turn can allow more efficient production of this crop.

Technical Abstract: Few herbicides are available for use in lettuce and hand weeding is required for commercially acceptable weed control. More effective herbicides are needed. Here we report field evaluations of pendimethalin and S-metolachlor for weed control in transplanted lettuce. Pendimethalin was evaluated PRE at rates between 0.6 to 6.7 kg ai ha-1, and POST at 1.1 and 2.2 kg ha-1. Both pendimethalin PRE and POST applications were safe to transplanted lettuce and provided similar weed control. Pendimethalin at rates of 1.1 kg ha-1 and higher provided better weed control than the industry standard, pronamide, at 1.3 kg ha-1. S-metolachlor PRE was evaluated at rates between 0.6 to 5.6 kg ha-1. S-metolachlor at rates up to 2.8 kg ha-1 caused little or no crop injury or yield reduction in transplanted lettuce, and S-metolachlor at rates of 1.4 kg ha-1 and higher improved weed control compared to pronamide. Pendimethalin and S-metolachlor are not yet labeled for transplanted lettuce, and we recommend that labeling should be pursued at rates of 1.1 and 0.7 kg ha-1, respectively. Pendimethalin at 1.1 kg ha-1 applied PRE or POST improved weed control by 57% and 42%, respectively compared to pronamide. S-metolachlor PRE at 0.7 kg ha-1 was less effective on weeds than pendimethalin, but maintained a similar weed control level as pronamide. Pendimethalin and S-metolachlor have potential for use in transplanted lettuce production and provide adequate alternatives for pronamide.