Although California and Florida are the major strawberry producers, growers in several other States have been planting small acreages for local consumption for years. Methyl bromide has been the fumigant of choice for these small growers.

With only a few more seasons left before the 2001 ban on methyl bromide, Louisiana strawberry growers are looking for alternatives to keep their production in step with local demand.

"We're trying chemical alternatives as well as organic soil amendments," says Roy J. Constantin. He is Director of the Hammond Research Station, which is part of the Louisiana State University's Agricultural Center, Louisiana Agricultural Experiment Station. "And although we only have 1 year's data analyzed, we're encouraged with the results from both of these research projects. Compared with methyl bromide, yields from both projects were not significantly different."

At the Hammond location, Constantin and colleague J. P. Quebedeau fumigated test plots with Vapam, Basamid, and methyl bromide, and had a control plot without fumigation. They applied the fumigants to the fine sandy loam soil on September 30, 1994, using 100 gallons of Vapam, 350 pounds of Basamid, or 250 pounds of methyl bromide per acre, and immediately covered all the plots with 1.25 mil black polyethylene mulch.

"We transplanted Chandler strawberry plants on October 24 and followed cultural practices recommended by the Louisiana Cooperative Extension Service for frost protection, irrigation, insect and disease control throughout the growing and harvesting stages," Constantin explains.

"At spring harvest, we found no significant differences in yield of marketable strawberries between plots treated with Vapam and Basamid and those treated with methyl bromide. Low yields occurred in all test plots because of anthracnose, a fungal disease that attacks strawberries."

In pounds of berries per acre, marketable yields were 4,734 for the control plot; 4,913, Vapam; 5,357, Basamid; and 5,516, methyl bromide.

The fine sandy loam soil of southern Louisiana contains only about 0.05 percent organic matter. Constantin and Louisiana State University colleagues added five organic mixtures to the soil in strawberry field plots in October 1995. James Magee, based at ARS' Small Fruit Research Laboratory in Poplarville, MS, is doing chemical and quality analyses of the fruit.

"Initially, we applied 10 tons per acre of either hardwood bark, cottonwood bark, crab meal, sewage sludge, or cotton gin waste," Constantin says. "We used a cultivator shank to open the beds and incorporated the organic matter with a rototiller."

Soil samples showed only two plots with a few nematodes, with the remaining plots completely free of infestation.

As with the chemical test plots, black plastic mulch was laid before strawberry plants were transplanted in November, and conventional cultural practices were followed until harvest, which lasted from late March until the middle of May 1996. Late harvest was due to an extremely harsh winter in 1995-96 for early season strawberries in southeastern Louisiana. Berries were produced over a 4- to 5-week period instead of the normal 8 or 9 weeks.

"We had temperatures that dipped down to 13 degrees F in February and down to 22 degrees F in March, which is unusual for southern Louisiana," Constantin says. "So, production was reduced and delayed substantially. But there were no significant differences in yield of marketable or cull fruit due to use of the soil amendments."

According to Constantin, the experiment was done in part to see if the added organic matter would decrease diseases. None of the amendments decreased disease incidence. And without methyl bromide, weeds were a problem. Weeds around plants were hand-pulled, but the herbicide Gramoxone was used for weed control in the middle of the beds.

There were yield differences among the amendments. Plants grown in soil treated with crab meal produced the highest percentage of marketable fruit, and plants grown with cottonwood bark, the least. Plots treated with sewage sludge produced almost 3,000 pounds more per acre than plots treated with cottonwood bark. The assumption is that the bark needs time to decompose before the soil can benefit from its organic matter. This is the first year of a proposed 5-year project.

Total yield of strawberries from plots treated with sewage sludge was 9,533 pounds; crab meal, 8,929; control, 8,196; cotton gin waste, 7,718; hardwood bark, 7,340; and cottonwood bark, 6,536. These yields were much higher than those from the fumigant study; however, Constantin says the two experiments were conducted on separate feilds on the research station and were planted at different dates, so they can't be compared with each other. Also, anthracnose infestation was very light in the test plots treated with organic amendments but had been a major problem in the fumigant study.

"We're going to repeat these experiments this fall and hope that yields will increase, especially in cottonwood-bark-treated plots, since more time will allow further breakdown of organic compounds in the bark," Constantin reports.

"We feel that these research projects show that our southeastern Louisiana growers who plant a few acres of strawberries for local consumption or for sale to Baton Rouge and New Orleans markets will be able to survive without methyl bromide, although some chemical will be necessary to control weeds."