Progress 10/01/04 to 09/30/05
Outputs
For more than three decades, vegetable crop growers in Florida and the Caribbean have relied on soil fumigation with methyl bromide (MBr) to control a broad spectrum of soilborne diseases, nematodes, and weeds. However, MBr is being phased out because it is an ozone-depleting agent. Potential alternatives to MBr are currently under study. One limitation of these alternatives is that application methods need to be improved to control soilborne pests. Therefore, it was proposed to pursue the following objectives. Objective 1: Establish the tomato yield-wetting pattern relationship. Results: It was determined that the covered surface area across planting beds increased from 82 to 94% when the soil water content per weight changed from 7 to 20%. Objective 2: Assess the effect of irrigation system flushing on fumigant placement. Results: The results confirmed that two drip irrigation lines and between 50 and 100 m3 of flushing water after the applciaiton of
1,3-dichloropropene + chlorpicrin (1,3-D + Pic) provided the best soil wetting pattern. However, either nutsedge control or tomato yield did not improve with these flushing volumes after 1,3-D + Pic application. Objective 3: Determine the effect of bed widths on wetting patterns and yield, and determine the extent of fumigant movement in the soil gaseous phase. Results: Because the complexity and size of this study, it was split in two trials, one for each factor involved (bed widths and mulch types). Preliminary data for the bed width trial showed that nutsedge control on bed shoulders can be improved with narrower beds (24 inches) as compared to the standard 28 inch-wide beds. Advances of the results for the mulch and fumigant retention trials indicated that Klerk virtually impermeable film (VIF), IPM Bromostop VIF, and Pliant metalized film had 120, 41, and 76% more 1,3-D + Pic retention than the standard high density polyethylene film (HDPE) used by most growers. This higher
retention transplated in 7, 2.5, and 4 times less nutsedge density than HDPE, respectively. Objective 4: Evaluate the effect of supplementary herbicides through drip lines. Results: In Puerto Rico, applying metolachlor either in preemergence or through drip lines resulted in excellent season-long broadleaf weed control and tomato yield. However, in Florida, the application of metolachlor and pebulate either in preemergence or through drip did not differ from the grower standard (MBr) in nutsedge control and tomato yield. Objective 5: Validate developed techniques for fumigant drip application under grower conditions. Results: Large-scale validations are being conducted in a grower field in Florida and two field tours with 20 and 25 researchers, industry representatives and extensionists have been accomplished.
Impacts
Herbicides are seldom used in mulched crops due to the use of methyl bromide. Adoption of fumigant alternatives will likely change that. Along with the alternatives will come increased need for weed control in the plant hole. This will be especially acute for double-cropped commodities. The ability to inject a herbicide into the bed via drip tubing will be a tremendous aid to growers and will reduce weeding costs and crop losses. Better understanding of the movement of drip applied fumigants, as well as herbicides, will speed their adoption and the transition away from methyl bromide.
Publications
- Santos, BM, JP Gilreath, and TN Motis. 2003. Length of irrigation and soil humidity as basis for delivering fumigants through drip lines in Florida spodosols. Proc. Fla. State Hort. Soc. 116:85-87.
- Gilreath, JP, BM Santos, TN Motis, and M von Hulten. 2004. Effect of mulch types on 1,3-dichloropropene + chloropicrin retention and nutsedge (Cyperus spp.) control. Proc. Fla. State Hort. Soc. 117:7-11.
- Santos, BM and JP Gilreath. 2005. Differential purple nutsedge (Cyperus rotundus) penetration through mulch films. HortScience 40:889.
- Santos, BM, JP Gilreath, M de L Lugo, and LE Rivera. 2005. Efficacy of drip-delivered herbicides for weed control in tomato in Puerto Rico. HortScience 40:889.
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Progress 09/15/03 to 09/14/05
Outputs
Investigator resigned. No termination report available.
Impacts
Investigator resigned. No Impact Report to be submitted.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/30/04
Outputs
Field trials were conducted with water soluble dye as an indicator of the location of the wetting front and water body following delivery of products through drip irrigation tubing. Results indicated that in order to deliver a fumigant to greater than 50% of the bed volume, for a 32 inch-wide, 8 inch-tall bed, required delivery in 1 acre inch of water. Additionally, product had to be delivered throughout the irrigation cycle in order to achieve uniformity. Delivery via a single drip tube was not as effective as applications using 2 tubes in a bed, but multiple tubes is a more expensive option and is not as acceptable or adaptable for all crops or growers. Trials with metam, 1,3-D and dye indicated that metam did not move beyond the wetting front, but 1,3-D moved at least 4 inches after delivery, thereby enhancing efficacy toward the bed shoulders. Post delivery flushing tended to move fumigant downward rather than laterally. A trial conducted with herbicides applied
through drip lines indicated that some herbicides could be delivered in this fashion, but the lateral distribution was limited to the zone of the plant hole and not as far as the bed shoulders. Lateral movement was more of a function of the herbicide evaluated than of the water volume used during application. Additional work is planned on this topic, with grower trials to demonstrate the results of the project.
Impacts
Herbicides are seldom used in mulched crops due to the use of methyl bromide. Adoption of fumigant alternatives will likely change that. Along with the alternatives will come increased need for weed control in the plant hole. This will be especially acute for double-cropped commodities. The ability to inject a herbicide into the bed via drip tubing will be a tremendous aid to growers and will reduce weeding costs and crop losses. Better understanding of the movement of drip applied fumigants, as well as herbicides, will speed their adoption and the transition away from methyl bromide
Publications
- Desaeger, J., Eger, J., Csinos A., Gilreath, J.P., Olson, S.M., Webster, T.M. 2004. Movement and biological activity of drip-applied 1,3-dichloropropene and chloropicrin in raised beds in the southeastern US. Pest Management Science (in press).
- Gilreath, J.P., B.M. Santos, P.R. Gilreath, J.P. Jones, and J.W. Noling. 2004. Efficacy of 1,3-dichloropropene + chloropicrin application methods in combination with pebulate and napropamide in tomato grower fields. Crop Prot. 23:(in press).
- Gilreath, J.P., J.W. Noling, and B.M. Santos. 2004. Methyl bromide alternatives for bell pepper (Capsicum annuum) and cucumber (Cucumis sativus) rotations. Crop Prot. 23:347-351.
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