Principal Investigator: D.O. Chellemi, University of Florida, North Florida Research and Education Center, Quincy, FL 32351, now with the ARS-U.S. Horticultural Research Laboratory, Orlando, FL 32803.

Cooperators: S.M. Olson, R. McSorley, J.R. Rich, K.D. Shuler, L.E. Datnoff, and K.L. Pernezny

Florida fresh-market tomato producers account for 17 percent of all methyl bromide use in the United States. In an effort to develop an integrated pest management program (IPM) for soilborne pests of fresh-market tomato, we investigated the potential contribution of soil solarization in laboratory, greenhouse and field experiments. The experimens were validated in large-scale demonstration plots on six commodities at nine different commercial farms.

Due to differences in fertilizer applications, inadequate coverage of paint during termination of the solarization period, or failure to collect complete yield data, a direct yield comparison between soil solarization and methyl bromide treated plots was made on three of seven farms with fresh market tomato. On one farm, solarization out-yielded methyl bromide-treated plots by 122 boxes per acre. On the other two farms, methyl bromide out-yielded soil solarization plots, but by less than 100 boxes per acre. In the location where pepper was evaluated, grower packout data indicated that methyl bromide out-yielded soil solarization plots by 78 boxes per acre.

Weed suppression in soil solarization plots was comparable to plots treated with methyl bromide in all locations except when purslane (Portulaca oleracea L) and Texas panicum (Panicum texanum Buckl.) were present. In these cases, soil solarization failed to provide adequate control. At low levels of disease, soil solarization provided better control of southern blight (Sclerotium rolfsii) than methyl bromide (Maxwell/Suber). Root gall ratings of root systems indicated that soil solarization did not provide adequate control of root-knot nematodes (Meloidogyne spp.). Combining solarization with reduced rates of Telone C-17 provided reductions in root galling similar to those achieved with methyl bromide. In general, it appeared that the longer the solarization period, the more effective the suppression of soilborne pests. Soil moisture at or near field capacity was also essential for effective suppression of soilborne pests.

Two technical problems which became evident during the large-scale applications were: (1) If drip irrigation tubing is used, it must be covered with soil to keep the tube from melting. (2) While painting the plastic white to terminate the solarization period, growers must make certain that coverage is uniform and complete to prevent any additional solar radiation from penetrating the plastic and heating the soil to levels detrimental to the health of transplants.

In a followup survey of participants evaluating the performance of soil solarization, growers indicated that soil solarization has a future role in their production system. When asked what extent of their total acreage could utilize soil solarization, the response varied from undecided to 50 percent.

In conclusion, soil solarization appears to be a viable alternative to preplant fumigation with methyl bromide for fall-cropped fresh market vegetables in Florida. However, soil solarization has specific application requirements and limitations which will restrict its widespread application. Fields must be prepared and plastic applied seven or eight weeks before planting. Soil moisture requirements are more stringent than those required for fumigation with methyl bromide. Soil solarization alone does not provide effective control of plant parasitic nematodes and when used in a nematode-infested field, should be combined with an effective nematicide. Suppression of weeds to the point of eliminating their effect on yield is adequate in most situations, but it should be pointed out that weed growth beneath the plastic mulch is not eliminated.

Finally, we highly recommend that soil solarization be used within the context of an IPM program for soilborne pests which includes the coordinated use of multiple pest management tactics based on scouting reports of prior pest levels.

Adoption of this approach will require additional management of information and decisionmaking by the grower.