Tomato Production Guide for Florida: Weed Control ( Publisher's URL )

Material Information

Tomato Production Guide for Florida: Weed Control
Physical Description:
Fact sheet
Stall, W.M.
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:


Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
General Note:
"August 1997."
General Note:
"SP 214"

Record Information

Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
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All rights reserved by the submitter.
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1.This document is a chapter of SP 214, last printed in 1990 as Circular 98 C. SP 214, Tomato Production Guide for Florida, last printed in 1990 as Circular 98 C, is a publication of the Commercial Vegetable Guide Series, Florida Cooperative Extension Service, Institute of Food and A gricultural Sciences, University of Florida. Publication date: August 1997. For more information about how to order the complete print document, SP 2 14, call UF/IFAS Distribution at (352) 392-1764. Please visit the FAIRS Website at The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide resea rch, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Servi ce office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean. 2.W.M. Stall, professor, Horticultural Sciences Department, Cooperative Extension Service, Institute of Food and Agricultural S ciences (IFAS), University of Florida, Gainesville FL 32611. The Tomato Production Guide for Florida is edited by G.J. Hochmuth, professor, Horticultural Sciences Department, IFAS. SP-214Tomato Production Guide for Florida: Weed Control1W.M. Stall2Although weed control has always been an important component of tomato production, its importance has increased with the introduction of the sweet potato whitefly and development of the associated irregular ripening problem. Increased incidence of several viral disorders of tomatoes also reinforces the need for good weed control. Common weeds, such as the difficult-to-control nightshade, and volunteer tomatoes (considered a weed in this context) are hosts to many tomato pests, including sweet potato whitefly, bacterial spot, and viruses. Control of these pests is often tied, at least in part, to control of weed hosts. Most growers concentrate on weed control in row middles; however, peripheral areas of the farm may be neglected. Weed hosts and pests may flourish in these areas and serve as reservoirs for re-infestation of tomatoes by various pests. Thus, it is important for growers to think in terms of weed management on all of the farm, not just the actual crop area. Total farm weed management is more complex than row middle weed control because several different sites, and possible herbicide label restrictions are involved. Often weed species in row middles differ from those on the rest of the farm, and this might dictate different approaches. Sites other than row middles include roadways, fallow fields, equipment parking areas, well and pump areas, fence rows and associated perimeter areas, and ditches. Disking is probably the least expensive weed control procedure for fallow fields. Where weed growth is mostly grasses, clean cultivation is not as important as in fields infested with nightshade and other disease and insect hosts. In the latter situation, weed growth should be kept to a minimum throughout the year. If cover crops are planted, they should be plants which do not serve as hosts for tomato diseases and insects. Some perimeter areas are easily disked, but berms and field ditches are not and some form of chemical weed control may have to be used on these areas. We are not advocating bare ground on the farm as this can lead to other serious problems, such as soil erosion and sand blasting of plants; however, where undesirable plants exist, some control should be practiced, if practical, and replacement of undesirable species with less troublesome ones, such as bahiagrass, might be worthwhile. Certainly fence rows and areas around buildings and pumps should be kept weed-free, if for no other reason than safety. Herbicides can be applied in these situations, provided care is exercised to keep it from drifting onto the tomato crop.


Tomato Production Guide for Florida: Weed Control Page 2 February 1998Field ditches as well as canals are a special consideration because many herbicides are not labeled for use on aquatic sites. Use of rye as a windbreak has become a common practice in the spring; however, in some cases, adverse effects have resulted. If undesirable insects such as thrips build up on the rye, contact herbicide can be applied to kill it and eliminate it as a host, yet the remaining stubble could continue serving as a windbreak. The greatest row middle weed control problem confronting the tomato industry today is control of nightshade. Nightshade has developed varying levels of resistance to some post-emergent herbicides in different areas of the state. Best control with postemergence (directed) contact herbicides are obtained when the nightshade is four to six inches tall, rapidly growing and not stressed. Two applications in about 50 gallons per acre using a good surfactant is usually necessary. With post-directed contact herbicides, several studies have shown that gallonage above 60 gallons per acre will actually dilute the herbicides and therefore reduce efficacy. Good leaf coverage can be obtained with volumes of 50 gallons or less per acre. A good surfactant can do more to improve the wetting capability of a spray than can increasing the water volume. Many adjuvants are available commercially. Some adjuvants contain more active ingredient than others and herbicide labels may specify a minimum active ingredient rate for the adjuvant in the spray mix. Before selecting an adjuvant, refer to the herbicide label to determine the adjuvant specifications. Additionally important is good field sanitation with regard to crop residue. Rapid and thorough destruction of tomato vines at the end of the season has always been promoted; however, this practice takes on new importance with the sweet potato whitefly. Good canopy penetration of pesticidal sprays is difficult with conventional hydraulic sprayers once the tomato plant develops a vigorous bush due to foliar interception of spray droplets. The sweet potato whitefly population on commercial farms was observed to begin a dramatic, rapid increase about the time of first harvest in the spring of 1989. This increase appears to continue until tomato vines are killed. It is believed this increase is due, in part, to coverage and penetration. Thus, it would be wise for growers to continue spraying for whiteflies until the crop is destroyed and to destroy the crop as soon as possible with the fastest means available. The importance of rapid vine destruction cannot be over stressed. Merely turning off the irrigation and allowing the crop to die will not do; application of a desiccant followed by burning is the prudent course. Herbicide performance depends on weather, irrigation, soil type, as well as proper selection for weed species to be controlled and accurate application and timing. Obtain consistent results by reading the herbicide label and other information about proper application and timing of each herbicide. Use only labeled herbicides and those herbicides in the proper formulation. When applying a herbicide for the first time in a new area, use only in a small trial basis. Information on labeled herbicides may be obtained from Weed Control in Tomatoes, Fact Sheet HS-200.