1	Efficacy of 1,3-Dichloropropene plus Chloropicrin and Herbicides on Purple Nutsedge (Cyperus rotundus) Control in Tomato
2	Introduction Purple nutsedge is one of the most troublesome weeds in vegetable crops. The aggressive nature: Fast-growing weed, Asexual reproductive structures, Survival under stressful field conditions. Previous studies: Survive under continuous mowing, without losing tuber-sprouting ability, Ability to grow under low light situations.
3	Introduction In Florida: More than US$600 million, More than 30% of the total vegetable value. Fresh tomato is usually produced using plastic polyethylene mulch. However, plastic mulch is ineffective against purple nutsedge.
4	Introduction There are few selective herbicides for purple nutsedge control in fresh tomato. Tomato growers combine different control methods for effective purple nutsedge management. Between-row applications of glyphosate and paraquat, Bed fumigations with methyl bromide (MBr). MBr is being phased out. U.S. Clean Air Act and Montreal Protocol, Active search for MBr alternatives.
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6	C-35 + pebulate Previous studies: The combination of 1,3-D and Pic (C-17 and C-35) are among the most promising alternatives to MBr. This combination alone cannot effectively control purple nutsedge. The herbicide pebulate combined with C-35 increases efficacy on purple nutsedge.
7	Introduction Pebulate needs to be reregistered by the manufacturer. Additional herbicides need to be tested in combination with soil fumigants to broaden the spectrum available for tomato growers. Depth of incorporation could play a critical role on the efficacy of a given chemical alternative. Changes in soil humidity, microbial activity and temperature that occur throughout the soil profile. Scarce research has been conducted in this subject.
8	Objective Compare the efficacy of various herbicides, in combination with the soil fumigant C-35 on purple nutsedge control and their effect on fresh tomato yield.
9	Materials and Methods Two field trials. Gulf Coast REC, University of Florida. EauGallie fine sand (Alfic Haplaquods, sandy, siliceous, hyperthermic). 1.0% organic matter and pH 7.3. Fields heavily infested by purple nutsedge (»150 plants/m²). 285 kg/ha of 15N-0P-25K as starter fertilizer.
10	Materials and Methods Nine treatments in two seasons. RCB design with six replications. Combinations of C-35 and herbicides, a non-fumigated control and C-35 injected alone. The fumigant C-35 was applied as the combination of 1,3-D + Pic (65:35) at 350 L/ha. Standard N-pressurized fumigation rig (240 kPa) Three chisels per bed spaced 30 cm apart.
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12	Materials and Methods One day before C-35 injection:
13	Materials and Methods Herbicides application: Tractor-mounted three-nozzle boom with 8004 flat fan nozzles. Spraying volume was 430 L/ha, pressurized with CO₂ at 240 kPa. After herbicide application, beds were pressed and covered with low-density polyethylene film (0.038 mm thick). Under the mulch film, one drip irrigation line was placed.
14	Materials and Methods Single rows of ‘Solar Set’ tomato were planted 3 WAT on top of pressed beds. Tomato transplants were planted at spacing of 0.45 x 0.70 m. Variables: Plant vigor at 5 and 12 WAT, Purple nutsedge densities at 5 and 12 WAT, Fruit number and weight at 15 and 17 WAT.
15	Materials and Methods Statistical analysis: Purple nutsedge densities: Friedman nonparametric test. Plant vigor: Normalized with arc sin transformation, then ANOVA. Tomato yield: ANOVA and single-degree of freedom orthogonal contrasts.
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18	Summary and Conclusions At 5 WAT: When pebulate added to C-35, purple nutsedge control improved in comparison with C-35 alone. The deep incorporation of pebulate (20 cm) was more effective in reducing weed density than at 10 cm. Pebulate incorporated at 20 cm was more effective controlling purple nutsedge than all other herbicides. With regard to metolachlor rates, the high dose (2.25 kg ai/ha) increased purple nutsedge control.
19	Summary and Conclusions Tomato fruit number: A 48% increase with C-35 alone with respect to the untreated plots. A 35% increase by adding of pebulate to C-35. Deep incorporation of this herbicide improved fruit number by 28%. C-35 + pebulate at 20 cm deep had higher fruit numbers than all other C-35 + herbicides treatments. Tomato fruit weight: Increased 51% with the application of C-35 alone. Adding pebulate improved fruit weight by 22%. C-35 + pebulate was 41, 43, 63, and 77% higher than C-35 plus either napropamide, metolachlor, lactofen, and flazasulfuron, respectively.
20	Conclusions Supplementary application of herbicides is necessary to improve initial weed control. Pebulate was consistently more effective controlling purple nutsedge during the early stages of the crop than the other herbicides tested. In terms of tomato fruit yield, none of the herbicides tested was comparable to pebulate.
21	Conclusions Depth of pebulate incorporation is important: Deep herbicide incorporation could place pebulate more effectively in the purple nutsedge root zone. Pebulate fumes are less likely to escape from under the plastic mulch with deep herbicide incorporation. More research is needed to find other herbicides comparable to pebulate in combination with C-35.