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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #318903
Title: Evaluation of cycloate followed by two-leaf stage phenmedipham application in fresh market spinach

Author
item LATI, RAN - University Of California
item Mou, Beiquan
item RACHUY, JOHN - University Of California
item FENNIMORE, STEVEN - University Of California

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2015
Publication Date: 6/6/2016
Citation: Lati, R.N., Mou, B., Rachuy, J.S., Fennimore, S.A. 2016. Evaluation of cycloate followed by two-leaf stage phenmedipham application in fresh market spinach. Weed Technology. doi: 10.1614/WT-D-15-00102.1.

Interpretive Summary: Few herbicides are available for spinach and there is a need for additional herbicides tools for growers. Fresh market spinach has one primary herbicide, cycloate, which does not control all weeds. Previous studies demonstrated that cycloate applied pre-emergence followed by another herbicide phenmedipham at the four-leaf stage is a safe and effective weed control method for spinach. However, this treatment is not useful for the main growing season due to short crop cycle. This study evaluates the potential to use cycloate followed by phenmedipham on spinach at two-leaf stage. Greenhouse and field studies were conducted in 2014 using three spinach varieties with low (Nordic and Sardinia) and high (Regal) tolerance to phenmedipham. Greenhouse studies revealed that phenmedipham at a rate of 90 g active ingredient per hectare was safe to Regal when applied at the two-leaf stage. Sardinia was more susceptible to phenmedipham injury under high light than low light conditions. In the field, the impact of time of day on phenmedipham safety was evaluated; morning with high light intensity vs. evening with low light intensity. Injury estimations taken 3 days after treatment (DAT) were lower for evening than for morning applications. Nonetheless, injury 11 DAT and spinach yield evaluations found that differences between morning and evening applications had subsided. Cycloate followed by two-leaf phenmedipham at 90 and 180 g per hectare were safe to spinach and improved weed control compared to cycloate alone. Cycloate followed by 180 g per hectare phenmedipham at the two-leaf stage reduced weed biomass by 88% compared to cycloate alone. Results here show that phenmedipham applied at the two-leaf stage is safe to fresh market spinach and it has the potential to be used during most of the fresh spinach growing season. Results from this study can contribute to successful integration of more herbicides into currently used weed-management systems for spinach, which in turn can allow more efficient production of this crop.

Technical Abstract: Fresh market spinach has one primary herbicide, cycloate, which does not control all weeds. Previous studies demonstrated that cycloate PRE followed by (fb) phenmedipham at the four-leaf spinach stage is a safe and effective treatment. However, this treatment is not useful for the main growing season. This study evaluates the potential to use cycloate PRE fb phenmedipham on two-leaf spinach. Greenhouse and field studies were conducted in 2014 using three spinach varieties with low (Nordic and Sardinia) and high (Regal) tolerance to phenmedipham. Greenhouse studies revealed that phenmedipham at 90 g ai ha-1 was safe to Regal when applied at the two-leaf stage. Sardinia was more susceptible to phenmedipham injury under high light than low light conditions. In the field, the impact of time of day on phenmedipham safety was evaluated; morning with high light intensity vs. evening with low light intensity. Injury estimations taken 3 days after treatment (DAT) were lower for evening than for morning applications. Nonetheless, injury 11 DAT and spinach yield evaluations found that differences between morning and evening applications had subsided. Subsequently, cycloate (1,700 g ha-1) PRE fb phenmedipham (90 and 180 g ha-1) applied in the evening at the two-leaf stage was evaluated. A reference treatment was cycloate PRE fb phenmedipham (270 g ha-1) at the four-leaf stage. Cycloate fb two-leaf phenmedipham at 90 and 180 g ha-1 were safe to spinach and improved weed control compared to cycloate alone. Cycloate fb 180 g ha-1 phenmedipham at the two-leaf stage reduced weed biomass by 88% compared to cycloate alone. This level of weed control was similar to the reference treatment. Results here show that phenmedipham applied at the two-leaf stage is safe to fresh market spinach and it has the potential to be used during most of the fresh spinach growing season.