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  • Author or Editor: Lisa M. Ferguson x
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Lettuce (Lactuca sativa) is one of the most important U.S. fresh-market vegetables with year-round consumption. For winter markets, lettuce is produced in the southwestern states with plantings in early fall when soil temperatures are high. Seed germination of lettuce, however, is inhibited by soil temperatures over 25 °C. The objective of this study was to test the emergence and growth of five lettuce cultivars using two seedlots produced in winter or summer to provide information for improving stand establishment at high temperatures. Seeds of five cultivars (`Empire', `Parris Island Cos', `Waldmann's Green', `Prizehead', and `Dark Green Boston') produced in Yuma, Ariz., during summer or winter months were used. Seeds were planted in a greenhouse mix in plastic trays and grown in a growth chamber at 23, 25, 30 and 35 °C. After 4 weeks, number of emerged plants, number of leaves, height, fresh weight, dry weight, and leaf area were measured. At lower temperatures (23 and 25 °C), more plants emerged and plants developed more rapidly than at higher temperatures (30 and 35 °C). More plants emerged of `Empire' and `Parris Island Cos' than of `Waldmann's Green' or `Dark Green Boston'. Growth varied greatly for the different cultivars. At 35 °C, only `Empire' winter seed emerged. At other temperatures, summer seed lots generally were better than or equal to winter seedlots. This information suggests that seeds developed during the summer are more vigorous at emergence than those developed during the winter.

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Strawberry (Fragaria ×ananassa Duchnesne) growth and productivity were compared in fumigated and nonfumigated production systems. Strawberry transplants grown in potting mix amended with Trichoderma hamatum (Bonord.) Bainier, strain T382, Trichoderma harzianum Rifai, strain T22, or untreated, were planted in field plots treated with compost, compost amended with T. hamatum strain T382, Telone-C35, or not treated. Plants were sampled throughout the growing season, and dry weights of roots, crowns, leaves, flowers and fruit, leaf area, and total and marketable yield were determined. Trichoderma amendments to the potting mix improved plant dry weight and leaf area of strawberry transplants in the first year and suppressed root rot incidence in the second year but did not affect plant growth or disease incidence once the plants were set in the field. Field plants in fumigated plots had greater root, leaf, and crown dry weights, leaf area, and yield compared with plants in the other soil treatments. We conclude that Trichoderma amendments (1) alone had little benefit to plug plant growth and (2) in combination with compost, had no benefit to strawberry plant growth in the field. The task remains to develop a reliable and sustainable strawberry production system that does not rely on chemical fumigants.

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Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr) based on their cost-effectiveness in the production of strawberries (Fragaria ×ananassa). The analysis was conducted for two geographical areas: the piedmont and coastal plain area (including North Carolina and Georgia) and the mountain area of western North Carolina, based on 7 years of field test data. The fumigation alternatives evaluated were Telone-C35 (1,3-dichloropropene 61.1% + chloropicrin 34.7%), Telone II (1,3-dichloropropene 94%), chloropicrin (Chlor-o-pic 99% and TriClor EC), InLine (1,3-dichloropropene 60.8% + chloropicrin 33.3%), and metam sodium (Vapam or Sectagon 42, 42% sodium methyldithiocarbamate). The MeBr formulation was 67% MeBr and 33% chloropicrin (Terr-O-Gas) with the exception of the earlier trials where a 98:2 ratio was used. In the piedmont and coastal plain area, the soil treated with chloropicrin showed the best results with an additional return of $1670/acre relative to MeBr, followed by Telone-C35 with an additional return of $277/acre. The projected return associated with shank-applied metam sodium was approximately equal to the estimated return a grower would receive when applying MeBr. Fumigating with drip-applied metam sodium, InLine, and Telone II as well as the nonfumigated soil treatment resulted in projected losses of $2182, $2233, $4179, and $6450 per acre, respectively, relative to MeBr. In the mountain area, all of the alternatives resulted in a projected increase in net returns relative to MeBr. The largest projected increase was $1320/acre for the InLine treatment, while the added returns for the TriClor and Telone-C35 applications were estimated to be $509 and $339 per acre, respectively. The drip-applied metam sodium application resulted in an additional return of $40/acre, and the added revenue for the nonfumigated soil treatment was $24/acre more than MeBr treatment. Although technical issues currently associated with some of the alternatives may persist, results indicate that there are economically feasible fumigation alternatives to MeBr in the production of strawberries in the southeastern U.S.

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Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr) based on their efficacy and cost-effectiveness in the production of tomato (Solanum lycopersicum). The analysis was conducted for the mountain tomato production region based on 6 years of field test data collected in Fletcher, NC. Fumigation alternatives evaluated included 61.1% 1,3-dichloropropene + 34.7% chloropicrin (Telone-C35™), 60.8% 1,3-dichloropropene + 33.3% chloropicrin (InLine), 99% chloropicrin (Chlor-o-pic), 94% chloropicrin (TriClor EC), 42% metam sodium (4.26 lb/gal a.i., Vapam), and 50% iodomethane + 50% chloropicrin (Midas). The MeBr formulation was 67% methyl bromide and 33% chloropicrin (Terr-O-Gas). Chloropicrin applied at 15 gal/acre provided the greatest returns with an additional return of $907/acre relative to MeBr. Telone-C35 provided an additional return of $848/acre and drip-applied metam sodium provided an additional return of $137/acre. The return associated with broadcast applied metam sodium was about equal to the estimated return a grower would receive when applying MeBr. Fumigating with a combination of chloropicrin and metam sodium; shank-applied chloropicrin at 8 gal/acre; drip-applied chloropicrin, Midas, or InLine; and the nonfumigated soil treatment all resulted in projected losses of $156/acre, $233/acre, $422/acre, $425/acre, $604/acre, and $2133/acre, respectively, relative to MeBr. Although technical issues currently associated with some of the MeBr alternatives may exist, results indicate that there are economically feasible fumigation alternatives to MeBr for production of tomatoes in North Carolina.

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