Low permeability tarp to improve fumigation efficiency for strawberry production in California, USA

Authors: Gao, Suduan; HUSEIN, AJWA - University Of California; FENNIMORE, STEVE - University Of California; QIN, RUIJUN - University Of California

Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/18/2012
Publication Date: 8/1/2014
Citation: Gao, S., Husein, A., Fennimore, S., Qin, R. 2014. Low permeability tarp to improve fumigation efficiency for strawberry production in California, USA. Acta Horticulture Proceedings. 1049:707-714.

Interpretive Summary: California produces 88% of the strawberries in the USA with a value of approximate $2.1 billion. While the unique climate in the coastal areas of CA is favorable for high yield and high quality berry production, soil fumigation has also been essential for control of soil-borne pests. The phase-out of methyl bromide has led to a shift towards alternative fumigants such as 1,3-dichloropropene and chloropicrin. The emissions from these toxic and volatile organic compounds are highly regulated. This paper reports the developments from field research to control fumigant emissions and improve fumigant efficiency using low permeability tarps such as the generic virtually impermeable film (VIF) or totally impermeable film (TIF). Film permeability and durability during field application are critical factors affecting the tarp performances. VIF and TIF have been shown to effectively reduce emissions. Our field research data show that TIF tarp can improve soil pest control and further using reduced fumigant rates under the TIF is possible because it has been shown to improve distribution uniformity of fumigants in soil and increased concentration-time (CT) index values compared to the standard polyethylene tarp using the same application rate. With more stringent regulations being developed, the use of lower fumigant rates with TIF tarp has multiple benefits including reduced fumigant release into the environment, reduced exposure risks for workers and bystanders, reduced buffer zones, and created a greater likelihood of maintaining the availability of soil fumigants to strawberry growers in CA.

Technical Abstract: California faces great challenges in sustainable strawberry production because the industry relies heavily on soil fumigants to control soil-borne pests, and more stringent regulations are being developed on fumigant use. Four field trials were used to investigate the potential of using low permeability tarp (e.g., virtually impermeable film or VIF, and totally impermeable film or TIF) to improve pest control efficiency and fumigant persistence and distribution in soil. Results from earlier field trials on VIF, which has a different structure than TIF, did not conclusively demonstrate improved weed control and strawberry yield than a standard tarp. The recent field trials using TIF indicate clearly that at the same application rate, TIF significantly increased fumigant concentrations under the tarp and in the soil thus resulting in much higher concentration-time exposure index values than for a standard tarp. The TIF further improved the uniformity of fumigant distribution in soil. All the data suggest that with TIF, reduced rates can be used to achieve good efficacy. Furthermore, the increase in the application rate of fumigants slowed down the degradation rate more significantly on chloropicrin compared to 1,3-dichloropropene. Thus, using a reduced rate under TIF is also necessary because of the increased fumigant persistency in soil in order to prevent a surge of emissions during tarp-cutting to protect workers and bystanders, and to avoid extended tarp cover duration that may affect planting time. This research has contributed to providing a long term solution for sustainable strawberry production through the use of low permeability tarp in soil fumigation that can result in less chemical input, higher fumigant efficiency, and more environmentally sound practices.