Reducing Weeds in Black or White Plastic in Eastern Strawberry Production

Reducing Weeds in Black or White Plastic in Eastern Strawberry Production - 2002 Report

Richard C. Funt
Department of Horticulture and Crop Science
Ohio State University

Introduction

Weeds are the number one pest of the Ohio strawberry industry. Growers who us the matted row system can spend in excess of two thousand dollars per acre for fumigation, hand weed control and/or chemical herbicides over two to three years to reduce the many different species of weeds (Funt et al., 1997). On Ohio farms the matted row system is used and the soil is not fumigated as a standard practice. However the combination of matted row culture and un-fumigated soil presents the greatest problem in weed control (Himelrick, 1991).

New systems of strawberry culture are being tested. One system is the use of plastic which can reduce weeds. It may also be beneficial in early ripening of fruit and rapid establishment of strawberry plants in a late summer planting. Himelrick, in Virginia, found mulch surface temperatures of clear, black and white plastic were 17E, 19E, and 15EC higher than for bare soil, respectively (Himelrick, 1981). He also found that black plastic increased total fruit weight. New systems need to be compared to current matted row systems for costs/benefits to the grower and to the environment. For example, plastic needs to be removed from the field and disposed of in an appropriate manner. In this study, an irrigated raised bed was tested without plastic (control) and with black and white plastic installed in an August plug planting (2001) and harvested the following two years (2002-2003).

Objectives

The objective of this experiment was to determine the amount of weed control between no plastic and plastic covered raised beds, yield, and a comparison of costs among the treatments.

Methods

Strawberry plug plants, Allstar cultivar, were planted in a staggered two row system, 12 inches apart in the row and between rows on August 8, 2001. The control was a raised bed with trickle irrigation. The treatments had black plastic (embossed - 1.0 mil., 5 ft. width) or white plastic (1.3 mil., 5 ft. width). The raised bed with trickle tubes, and plastic covering was constructed with a bedder after the field was plowed and rototilled (twice). A water wheel planter was used to create a hole in the plastic to apply a small amount of water. All plants were planted by hand. No herbicides were applied to the plastic treatments. Grass was planted between rows to reduce weeds and erosion. Straw was applied as a winter cover and removed on May 3, 2002.

Select 2 EC was applied for spring grass control where grass seed had entered the plastic near the plant. In the control, hand weeding was completed once in May, July and October, 2002. Herbicides 2,4-D, Dacthal, and Devrinol plus Sinbar were used after harvest in July, August and October, respectively. A cost comparison (partial budget) between the control and plastic treatments was developed to reflect the labor and products used in this study for determining a cost/benefit analysis.

Berries were harvested and total yield, percent ripe/harvest date and weight per berry (berry size) were determined. There were three treatments and three replications in a completely randomized block design. A statistical analysis appropriate for this field study was used (SAS, 1990). All berries received a herbicide spray of Gramoxone at renovation to narrow the row width (burn runners), and manage weed control for harvest in 2003.

Results

There were very few weeds in the plastic treatments. These consisted, if any, of grasses and bind weed. In the control, several grass species and broadleaf weeds as bind weed, Canadian thistle, and plantain were recorded before harvest, at renovation, and in late summer. Hand weeding was sufficient for maintaining a weed free planting (80 to 90% of area having no weeds). Chemical weed control was only temporary or unable to control weeds.

There were no significant yield differences among treatments at any harvest or for all harvests (Table 1). Treatments achieved about 40% of a normal expected harvest. Plastic did not statistically increase the number of berries to ripen early (June 13) when compared to the control (Table 2). There were no differences between black or white plastic for yield, percent ripe or berry size. Plastic appeared to reduce berry size in the June 21st harvest as compared to the control (Table 3).

The cost to control weeds among the treatments is shown in Table 4. Specific costs per item are shown in Table 5. These costs are based on early 2002 prices for each item as used by the grower-cooperator. Black and white plastic costs were 54% and 71%, respectively, of the no plastic system. Hand labor, as estimated per acre to that used in this study, was 68% of the total cost in the no plastic treatment.

Discussion

Plasticulture has been tested by Ohio growers to reduce weed control costs, to increase yields over matted row systems, and to have earlier ripening of berries. In this study, weed control was considered to be good to excellent with plastic and poor in the no plastic control. There were no differences among treatments for yield or for earlier ripening. However, Himelrick in 1991 reports yields for black plastic.

Yields for this cultivar at this location were disappointing for a double row system. An early October drop in temperature, deer damage, and a low bed could have been the reason for this. It is believed that the planting date was ideal and plant size was good. Weeds did not appear to influence yields in the control. There may be an influence on yield by weeds in the 2003 results.

The white plastic was disappointing and started to break up after 4 to 6 months and is not recommended based on performance and cost. The real influence of white plastic could not be demonstrated in this test.

If growers have similar costs as estimated in this report, then plastic has one distinct advantage for weed control. However, removal and disposal are to be considered in the total expense of the system and this could increase the cost.

Conclusions

Black or white plastic yields were not different from the no plastic control. Few weeds developed in the plastic treatments. Estimated costs for black or white plastic were 54% and 71%, respectively, of the no plastic system. Hand weeding labor was the highest cost for the no plastic system.

Differences in weed control may occur in the second harvest year of 2003 among treatments. The second harvest year may provide different yield response than the first year.

We gratefully acknowledge the financial support of the Ohio IPM program headed by Dr. Joe Kovach.
Where trade names are used, no discrimination toward similar products is intended or implied.

References

Funt, R.C., M.A. Ellis and C. Welty. 1997. Midwest Small Fruit Pest Management Handbook. Ohio State University Extension Bul. 861. p 1-171.

Himelrick, D.G. 1981. Effect of polyethylene mulch color on soil temperatures and strawberry plant response. Advances in Strawberry Production. Vol. 1. p 15-16.

Himelrick, D.G. and W.A. Dozier, Jr. 1991. Soil fumigation and soil solarization in strawberry production. Advances in Strawberry Production. Vol. 10, p. 12-29.

SAS Institute, Inc. 1990. SAS/STAT user's guide. 4th ed. Vol. 2. SAS Inst. Cary, NC.

For further information contact Richard Funt Dept. of Hort & Crop Science, The Ohio State University or the Ohio IPM Office.

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