Non chemical methods of weed control in strawberry annual plasticulture system

View the project final report

Commodities

• Fruits: berries (strawberries)

Practices

• Crop Production: application rate management, organic fertilizers
• Pest Management: allelopathy, biofumigation, cultivation, mulches - general, mulching - plastic
• Production Systems: integrated crop and livestock systems, organic agriculture
• Soil Management: toxic status mitigation
• Sustainable Communities: local and regional food systems, urban/rural integration

In strawberry (Fragaria X ananassa) annual plasticulture production system, weeds and other pests can be a major problem. Early season weed competition is detrimental to strawberry production if not controlled. Preemergence herbicide choice is limited in strawberry production; alternative fumigants currently being used after the methyl bromide (MB) phase out do not provide complete control of pests, have regulatory constraints, and require maintenance of buffer zones. Many growers choose to no longer fumigate their land. With challenges in using herbicides and fumigants, it is necessary to look at alternative strategies to facilitate well establishment of strawberry plants. A field study was done in 2015-16 growing season at Hampton Roads Agricultural Research and Extension Center with the objective to evaluate the effect of soil solarization (SS) integrated with corn gluten meal (CGM), mustard seed meal (MSM), and paper pellet mulch (PPM) on crop health, weed control, and crop yield. The study was set up as a randomized complete block design with four replications or plots. Treatments were untreated control, CGM at 1710 kg/ha, MSM at 1121 kg/ha, and PPM 3662 kg/ha with and without SS. SS was done for a 3 week preplant period. Treatment products were broadcast on the respective strawberry plots and rototilled up to 15 cm depth. Plots were covered either with a 1.25 mil. black polyethylene tarp in case of non SS treatments, or with 1 mil. clear polyethylene tarp in SS treatments. When the same study was done in 2014-15 growing season, the SS + CGM plots were damaged by raccoons soon after treatment application, and that particular treatment evaluation was discontinued, and not included in the 2015-16 growing season. Each plot was 3.1 m of bed length by 0.8 wide at bed top, of which 0.9 m length of the bed was replaced with clear tarp in case of non-solarization plots, and that “window area” was used for weed data collection. For the SS plots, no tarp replacement was needed, and 0.9 m length of bed top was marked to collect weed data in 0.9 m long by 0.8 m wide area. Strawberry 'Chandler' were transplanted on 30 September, 2015. Plant stand count and health rating for each plot was done on a monthly basis. Weed density data was collected periodically through the season from October to April. Yield data was collected by picking berries twice a week during bearing season, and sorting them into marketable and non-marketable fruits. Weed density count was lower in plots treated with SS, SS+MSM, and SS+PPM as compared to the untreated control, but there were no significant differences in marketable or total yields among the different treatments.

Introduction

The purpose of this project was to evaluate pelleted products with soil solarization (SS) for weed control in strawberry annual plasticulture production system. Weeds once emerged, can establish very fast. With the absence of MB, control of soil borne diseases and other pests is a problem. Though alternative fumigants are available, they are not as effective as MB. Use of fumigants comes with mandatory requirements such as maintaining buffer zones, writing a fumigant management plan, and dose restrictions. With lack of interest from chemical companies to register herbicides for many specialty crops, weed control remains a challenge in annual strawberry production. Currently registered herbicides such as oxyfluorfen and flumioxazin, have a 30 day –pre-plant application period, while others such as flumioxazin and napropamide have potential to cause phytotoxicity to strawberry plants (Southeast Regional Strawberry IPM Guide, 2015). Due to shortage of labor, weeds are often unattended at grower sites, and sometimes weeds are hand pulled as they come out of planting holes. In SS process, a clear tarp allows radiation to pass and trap heat; and can be used to increase soil temperature to the extent that it is lethal to pathogens, insects and weeds. SS is also more effective when used with other soil amendments (Ajwa et al., 2003). Paper mulch helps by preventing weed emergence. Paper mulch also helps to control nutsedge, which is not controlled by solarization. One of the advantages of using paper pellet mulch (PPM) is that it does not have weed seeds, does not blow away like shredded newspaper; the pellets expand upon absorbing water and releases water back to soil, keeping root zone moist. The paper pellets used in the study releases a starter fertilizer that promotes root development. The justification of using mustard seed pellets was that the allellopathic property of some plants in Brassicaceae inhibit growth, emergence and germination of weeds (Rice et al., 2007). Corn gluten meal is a minimum risk pesticide and also provides 10% nitrogen by weight and is a natural fertilizer. It controls weeds by preventing normal root development under dry conditions. In Virginia, a high percentage of strawberry is grown for fresh consumption and in summer, consumers with their families and friends pick strawberries at pick-your-own farms where they are in close contact with plants. Increased awareness among consumers about the use of pesticides in farms make them more at ease when minimum risk herbicides or non- chemical approaches are being adopted.

As listed in the proposal: 1. Evaluate pelleted products of mustard seed meal, paper, corn gluten meal integrated with soil solarization for weed control in annual strawberry plasticulture system. 2. Evaluate the effect of using pelleted products on crop yield of strawberries. 3. Evaluate the nutritional status of plants as a result of using pelleted products. 4. Evaluate crop growth through taking canopy growth data, and estimate growth of roots using a software. 5. Evaluate fruit quality of fruits as fruit firmness, sweetness and size. 6. Evaluate disease of plants in field. 7. Perform a cost analysis of using the pelleted products with soil solarization in a practical scenario at a grower’s farm.