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Most seedless watermelons are grown on black polyethylene mulch to aid crop establishment, growth, yield, and quality and weed control. However, nutsedge is a persistent problem in this production system, as it can easily penetrate the mulch. Halosulfuron-methyl is registered in some crops and provides excellent yellow nutsedge control. The objective of this research was to determine the effects of reduced halosulfuron-methyl contract to the watermelon plant on fruit yield and quality. The seedless watermelon cultivars, Tri-X-313 and Precious Petite, were transplanted into black polyethylene mulch and sprayed 16 days later. Halosulfuron-methyl at 35 g a.i./ha plus 0.25% (v/v) nonionic surfactant was applied at 187 L·ha–1 with a TeeJet 8002 even tip nozzle. Treatments were no spray, 25% of the vine tips, 25% of the crown, and over the top (entire plant). Plants in each treatment were rated (0% = no damage, 100% = fatality) for herbicide injury and the longest vine was measured on four plants. The no-spray treatment had the longest vines (156 cm). The topical halosulfuron treatment resulted in the shortest vines (94 cm) and the highest visual damage rating (63%). The herbicide caused foliage to yellow, internodes to shorten, and stems to crack. Treatments receiving halosulfuron-methyl applied to 25% of the vine (tip end) or 25% of the vine (crown end) resulted in reduced injury compared to the topical application. Generally, the 25% vine tip application was the safest halosulfuron treatment. The total yield (kg·ha–1) and number of watermelons/ha were similar among treatments. The no-spray treatment produced 4450 kg·ha–1 and 8300 watermelons/ha. The over-top treatment produced 3500 kg·ha–1 and 7300 watermelons/ha. Watermelon in the no-spray treatment weighed 4.4 kg, while watermelons weighed 3.9 kg with the over the top treatment. Halosulfuron-methyl is registered to apply to middles between watermelon rows; however, topical applications are prevented due to the possibility of crop injury. This research suggests that reduction of topical application to only 25% contact of the crop may improve crop tolerance. Thus application to nutsedge patches where limited contact to watermelon occurs may be a possibility in the future.

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Field research was conducted to evaluate pre-transplant (PRE) applications of sulfentrazone (0.20 or 0.41 kg·ha-1 a.i.) and flufenacet (0.045 kg·ha-1 a.i.), or early postemergence (EPOST) halosulfuron (0.027, 0.036 or 0.054 kg·ha-1 a.i.) on phytotoxicity and yield of field-grown chili (var. Sonora), jalapeño (var. Grande) and bell (var. Giant Belle) peppers (Capiscum annuum) in Texas. Crop injury recorded 15 days after sulfentrazone treatments (DAT) showed minor stunting at the low rate, but moderate stunting and temporary leaf malformation when applied at 0.41 kg·ha-1 a.i. Increased stunting occurred 37 DAT at both rates; however, new leaf growth was not affected. Flufenacet did not result in crop injury to any of the three types grown. Phytotoxicity from halosulfuron recorded 7 DAT gave significantly higher ratings for stunting/chlorosis for broadcast EPOST treatments when compared to EPOST-directed applications. Injury from halosulfuron was temporary and considered minor with all EPOST treatments by 22 DAT. Pepper yield data showed that EPOST halosulfuron treatments were statistically equivalent to the untreated controls for each of the three types, but there was a trend for lower yields with rates higher than 0.027 kg·ha-1 a.i. All peppers treated with flufenacet gave excellent yields. Sulfentrazone applied at the high rate gave the greatest yield losses in all three types, and this was significant in the jalapeños. The results indicate that all three herbicides have potential for use in commercial pepper production in Texas. However, more research is needed to evaluate these and other herbicides for improved crop safety in peppers.

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Two experiments were conducted to evaluate processing pumpkin and processing squash tolerance to preemergence herbicides. The experiments were randomized complete block designs with three or four replications. The herbicides were applied after seeding the crop using a CO2-pressurized sprayer delivering 233 L/ha. We evaluated clomazone alone, and in combination with either halosulfuron or sulfentrazone. The first experiment was conducted in Morton, Ill., using `Libby's Select' processing pumpkin (Cucurbita moschata). None of the treatments caused any significant pumpkin phytotoxicity. On 7 July all treatments reduced the number of grass weeds compared to the untreated control. There were no differences in grass control between the herbicide treatments. Broadleaf control was best in sulfentrazone at 0.56 kg/ha or clomazone + halosulfuron at 0.56 + 0.13 kg/ha and worst in the untreated control. Weed control decreased by the 29 July rating; grass and broadleaf weed control was unacceptable in all treatments due to infestation with perennial weeds. Sulfentrazone alone or with clomazone was safe for use on pumpkins in heavier soils. The second experiment, conducted in Champaign, Ill., used `NK530' processing squash (Cucurbita maxima). None of the treatments caused any squash phytotoxicity. The best control on 14 July was with combinations of clomazone and sulfentrazone. On 10 Aug., all herbicide treatments were similar in their control of broadleaf weeds. Sulfentrazone and halosulfuron do not injure processing pumpkin or squash when applied either alone or in combination with clomazone.

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At present, pitahaya (Hylocereus undatus Britt and Rose), a nonconventional crop and cactus native from Mexico, is considered very promising because of its high adaptability and tolerance to extreme agricultural conditions of tropical regions (poor soils, drought, and elevated temperatures), where they are cultivated. In addition, pitahaya fruit is well-accepted and identified as a nutraceutical food that lowers cholesterol and glucose levels in blood and might prevent stomach and colon cancers. However, little or no scientific information on chemical control alternatives of weeds in pitahaya commercial plantings have been generated. In this work, the phytotoxicity degree of seven commercial herbicides (metribuzin, glyphosate, glyphosate trimesium, paraqut, paraquat+diuron, atrazine, and halosulfuron methyl) in pitahaya plants grown under plant nursery conditions was assessed. A completely randomized design with 12 replications was used. The experimental unit was a flowerpot with a 5-month-old plants. The phytotoxicity degree was evaluated at 3, 7, 14, and 21 days after application using the scale proposed by EWRS. The herbicides that caused injury to the plants were paraqua+diuron (79%) and paraquat (77%), respectively. Metribuzin, halosulfuron-methyl, and atrazine did not cause any injury to the plants.

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A field study was conducted in 2002, 2003, and 2004 to evaluate various pre-emergence herbicides (ethafluralin & clomazone, ethafluralin & clomazone + halosulfuron, and ethafluralin & clomazone + imazamox) with or without a winter rye (Secale cereale L.) cover crop in tillage and no-tillage `Appalachian' pumpkin (Cucurbita pepo L.) production. All herbicides were applied within two days of seeding, and no injury was observed with any of the herbicides evaluated at any time during the three growing seasons. Early- and late-season control of all weed species [giant foxtail (Setaria faberi Herrm.), common cocklebur (Xanthium strumarium L.), redroot pigweed (Amaranthus retroflexus L.), and common waterhemp (Amaranthus rudis Sauer)] were highly correlated (0.47 ≤ r ≥ 0.86, P ≤ 0.01) with pumpkin yield and fruit size. The winter rye + no-tillage system provided greater weed control compared to the tillage systems and the no cover crop + no-tillage production system. Although winter rye alone had little influence on pumpkin yield, the no-tillage system improved pumpkin yield and fruit size compared to the tillage system. The two herbicide combinations (ethafluralin & clomazone + halosulfuron and ethafluralin & clomazone + imazamox) improved weed control and pumpkin yields compared to only ethafluralin & clomazone. Although this study indicated that the use of a high-residue winter rye cover crop in no-tillage pumpkin production will provide some weed control, the choice of pre-emergence herbicides is critical to maximize pumpkin productivity. No-tillage pumpkin production is feasible with proper herbicide use and timing, although current herbicide options will not provide optimal weed control.

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Watermelon is the major fresh-market vegetable grown in Oklahoma, but growers have few labeled herbicides from which to choose. Grower surveys in Oklahoma have identified weed control as the major production problem facing watermelon producers. In 1995 and 1996, various mechanical and chemical weed control strategies have been explored. `Allsweet' watermelons were grown with various combinations of labeled and unlabeled herbicides, as well as mechanical control treatments. Treatments included bensulide, clomazone, DCPA, ethalfluralin, glyphosate, halosulfuron, napropamide, naptalam, paraquat, pendimethalin sethoxydim, and trifluralin. Certain chemicals were used in combination. Paraquat and glyphosate were used as wipe-on materials. Glyphosate and paraquat could not be applied until weeds were taller than the watermelon foliage, causing serious weed competition. In general, superior results were obtained from hand-weeded plots, trifluralin, and DCPA. Halosulfuron gave superior control of broadleaf weeds, but had a negligible effect on grasses. Napropamide gave good control of grasses and broadleaf weeds other than solanaceous weeds. No chemical, when used alone, gave satisfactory control throughout the growing season. Early cultivation, followed by chemical application at layby, appears to be one of the better treatments.

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Herbicide use is an important component of weed management in field nursery crops. No single herbicide controls all weed species. Oxyfluorfen, simazine, and isoxaben are preemergence herbicides effective against broadleaf weeds. Oryzalin, pendimethalin, and prodiamine are effective in preemergence control of grasses and some small-seeded broadleaf weeds. Metolachlor is the only herbicide currently labeled for nursery crops that is effective in preemergence nutsedge (Cyperus) control. Fluazifop-butyl, sethoxydim, and clethodim are selective postemergence herbicides used for grass control. Glyphosate, paraquat, and glufosinate are nonselective postemergence herbicides used in directed spray applications for broad-spectrum weed control. Bentazon, halosulfuron, and imazaquin are effective postemergence nutsedge herbicides. These herbicides are discussed with respect to their chemical class, mode of action, labeled rates, and current research addressing their effectiveness in nursery crops.

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The Food Quality Protection Act may result in the withdrawal from use of many herbicides in the “minor” crops: fruits, vegetables, herbs, flowers, and ornamentals. An obvious mitigation strategy is to test and register newer, low-rate herbicides that are currently used only in large-acreage field crops. The newer herbicides have low mammalian toxicity, few off-target effects, and are often used at rates of less than 0.1 kg/ha. Many of the older herbicides are applied at rates of several kg/ha and have off-target effects that can make their use problematic. Low-rate herbicides could replace the older chemicals commonly used in horticultural crops. We have tested several promising low-rate herbicides: carfentrazone, cloransulam, dimethenamid, halosulfuron, rimsulfuron, and sulfentrazone. Broccoli, cantaloupe, carrot, lettuce, onion, spinach, and processing tomato varieties were screened for tolerance to low-rate herbicides at four locations in California that included desert, inland, and coastal environments. All of the crops tested had tolerance for one or more of the low-rate herbicides. Data on similar tests for other horticultural crops will also be presented. The potential for registering these herbicides in vegetables and other horticultural crops varies with the crop and the pesticide's manufacturer. Pesticides that may soon face removal from widespread use will be reviewed. Herbicides and other potential alternatives to currently registered herbicides will be examined to determine possible practical alternatives for specific crops and weeds.

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Preemergent and postemergent herbicides were evaluated in the Mediterranean climate of the southern San Joaquin Valley and the desert climate of the Imperial Valley from 1998 through 2000. Sixteen herbicide treatments were applied both as preemergence (PRE) and postemergence (POST) applications to carrot (Daucus carota L.). Carrot was generally more tolerant to PRE herbicide applications than to POST applications. Carrot was tolerant to PRE and POST imazamox and triflusulfuron at both locations. Carrot root losses due to herbicide were consistent with visual ratings. Treatments that injured carrot tops early in the growing season did not always reduce yield at the end of the season. PRE applications of imazamox and triflusulfuron did not affect carrot tops or the number or weight of marketable carrots. Carrots grown in the Imperial Valley and in the San Joaquin Valley were tolerant to PRE applications of carfentrazone, sulfentrazone, and imazamox. Results were similar for POST applications, although carfentrazone slightly injured carrot roots. PRE application of herbicides increased forked roots more than POST. Chemical names used: α, 2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1, 2,4-triazol-1-yl]-4-fluorobenzenepropanoic acid (carfentrazone); N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]me thanesulfonamide (sulfentrazone); N-(2 carbomethoxy-6-chlorophenyl)-5-ethoxy-7-fluoro (1,2,4) triazolo-[1, 5-c] pyrimidine-2-sulfonamide (cloransulam-methyl); 2-chloro-N-[(1-methyl-2-methoxy)ethyl]-N-(2,4-dimethyl-thein-3-yl)-acetamide (dimethenamid); (2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-(methoxymethyl)-3-pyridinecarboxylic acid) (imazamox); 3-chloro-5-[[[[(4,6-dimethoxy-2-pyrimidinyl) amino] carbonyl] amino] sulfonyl]-1-methyl-1H-pyrazole-4-carboxylic acid (halosulfuron); N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide (rimsulfuron); (methyl 2[[[[[4-(dimethylamino)-6-[2,2,2-trifluoroethoxy)-1,3,5-triazin-2-yl] amino] carbonyl] amino] sulfonyl]-3-methylbenzoate) (triflusulfuron).

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clethodim (Envoy Plus; Valent USA, Walnut Creek, CA), carfentrazone (Shark EW; FMC, Philadelphia, PA), halosulfuron (Sedgehammer; Gowan, Yuma, AZ), and clove leaf oil (Matran; Ecosmart Technologies, Franklin, TN). On all other plots, the same products were

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