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Shann Tanner, Christina Wells, and Gregory Reighard

The effectiveness of soil solarization as an alternative to methyl bromide (MBr) fumigation in replanted peach orchards was investigated at the Musser Fruit Research Farm near Clemson, S.C. A split plot experimental design was used, with soil treatment as the whole-plot factor and rootstock as the sub-plot factor. In Spring 2002, preexisting trees were removed from the study site, and six orchard rows were cultivated and subsoiled. In June, two rows were covered with clear polyethylene sheeting and solarized for the remainder of the summer. In November, two additional rows were treated with MBr (474.3 kg·ha-1), while the two remaining control rows received no soil sterilization treatment. In Jan. 2003, 36 `Redglobe' peach trees budded on Guardian™ or Lovell rootstock were transplanted to the site, and one minirhizotron was installed beneath each tree. Minirhizotron observations were made every 14–21 days from Feb. through Oct. 2003, and stem caliper measurements were taken on four dates during this interval. Trees grew significantly larger in the MBr and solarized rows than in the control rows (P< 0.1; Tukey's hsd), but there were no differences in stem caliper growth between MBr and solarization-treated trees. Reduced aboveground growth in control trees may have been related to greater carbon expenditure belowground: in the absence of soil sterilization, fine root median life spans were reduced by 27–28 days (P< 0.0001; proportional hazards regression) and rates of root production and mortality were significantly higher (P< 0.1; repeated measures ANOVA). Solarization and MBr fumigation appeared to provide similar benefits in reducing root turnover and improving aboveground growth at this site.

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Christina L. Pierson, Carl E. Sams, Dennis E. Deyton, and Craig S. Charron

Biofumigation is an alternative to traditional methods of soil sterilization such as methyl bromide. Biofumigation utilizes volatile, pesticidal compounds in soil incorporated plant material from various Brassica species. Three experiments were conducted to study the degradation of allyl isothiocyanate (AITC) generated from the breakdown of glucosinolates present in Oriental mustard (Brassica juncea L. Czerniak). Mustard seed meal was incorporated into a sandy clay loam soil in all experiments. In the first experiment, samples were hydrated and then held in an incubator at 20 ± 0.2 °C. Samples were taken periodically for 7 days or until AITC was not detectable. For the second experiment, hydrated samples were removed from the incubator after 4 hours and 5 mL of ethyl acetate was added. The samples were then placed in a refrigerator at 4 ± 0.2 °C and samples were taken periodically over 77 days. For the third experiment, samples were taken from a strawberry plot experiment grown in a randomized complete block design. Samples were taken and 5 mL of ethyl acetate was added. Then samples were placed into a cooler until returning to the laboratory. The incubator experiment was repeated and showed that the highest concentration of AITC occurred between 2 and 8 hours after hydration. The storage experiment showed a stable relationship between time and AITC degradation. AITC was still present after 77 days. The strawberry plot experiment showed rapid AITC degradation similar to the incubator experiment. Future research will be done to confirm the effects of temperature and glucosinolate content on the amount of allyl isothiocyanate present.

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Shengrui Yao, Ian A. Merwin, and Janice E. Thies

Apple (Malu ×domestica) replant disease (ARD) is a soil-borne disease syndrome of complex etiology that occurs worldwide when establishing new orchards in old fruit-growing sites. Methyl bromide (MB) has been an effective soil fumigant to control ARD, but safer alternatives to MB are needed. We evaluated soil microbial communities, tree growth, and fruit yield for three pre-plant soil treatments (compost amendment, soil treatment with a broad-spectrum fumigant, and untreated controls), and five clonal rootstocks (M7, M26, CG6210, CG30, and G16), in an apple replant site at Ithaca, N.Y. Molecular fingerprinting (PCR-DGGE) techniques were used to study soil microbial community composition of root-zone soil of the different soil treatments and rootstocks. Tree caliper, shoot growth, and yield were measured annually from 2002–04. Among the five rootstocks we compared, trees on CG6210 had the most growth and yield, while trees on M26 had the least growth and yield. Soil treatments altered soil microbial communities during the year after pre-plant treatments, and each treatment was associated with distinct microbial groups in hierarchical cluster analyses. However, those differences among fungal and bacterial communities diminished during the second year after planting, and soil fungal communities equilibrated faster than bacterial communities. Pre-plant soil treatments altered bulk-soil microbial community composition, but those shifts in soil microbial communities had no obvious correlation with tree performance. Rootstock genotypes were the dominant factor in tree performance after 3 years of observations, and different rootstocks were associated with characteristic bacterial, pseudomonad, fungal, and oomycetes communities in root-zone soil.

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Elio Jovicich, John J. VanSickle, Daniel J. Cantliffe, and Peter J. Stoffella

The uninterrupted supply of high quality colored peppers to the U.S. is mainly from imports of greenhouse-grown fruits. Average year-round wholesale market price of these imports was $4.80/kg when U.S. field-grown fruit price was $1.60/kg for colored and $0.91/kg for green. High market prices and a suitable environment for growing colored peppers in inexpensive protected structures led to construction of 25 ha of greenhouses currently growing peppers in Florida. Greater demand for specialty vegetable crops, loss of methyl bromide, and an increase in urban sprawl and price of arable land may result in growers considering greenhouses to produce high value peppers. We estimated the profitability of a greenhouse enterprise with a budget analysis and calculated the returns to capital and management. We assumed use of current technology applied in commercial greenhouse crops in Florida, and in experimental crops at the Univ. of Florida. Revenues per square meter were estimated from current yields and historical fruit price data. Plants were grown in perlite in a high-roof polyethylene-covered greenhouse (0.78 ha) located in north central Florida. Transplanting occurred in August and fruits were harvested from November to May for a yield of 13 kg·m-2 with a total cost of production of $41.09 and an estimated return of $17.89. The return on investment was 17%. Only yields greater than 7.8 kg·m-2 generated positive returns using the average wholesale fruit price during the season ($5.29/kg). For this price, a range of possible yields (5–17 kg·m-2) led to returns ranging from $–9.52 to $30.84, respectively. The estimates indicated that production of greenhouse-grown peppers could represent a viable production alternative for Florida vegetable growers.

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James P. Gilreath, Bielinski M. Santos, Joseph W. Noling, Salvadore J. Locascio, Donald W. Dickson, Erin N. Rosskopf, and Steven M. Olson

Field studies were conducted in three Florida locations (Bradenton, Gainesville, and Quincy) during 1998-99 and 1999-2000 to: 1) compare the performance of two transplant systems under diverse MBr alternative programs in `Chandler' strawberry (Fragaria ×ananassa), and 2) determine the efficacy of these treatments on soilborne pest control in strawberry. Fumigant treatments were: 1) nonfumigated control, 2) methyl bromide plus chloropicrin (MBr + Pic) at a rate of 350 lb/acre, 3) Pic at 300 lb/acre and napropamide at 4 lb/acre, 4) 1,3-dichloropropene (1,3-D) plus Pic at 35 gal/acre and napropamide at 4 lb/acre, 5) metam sodium (MNa) at 60 gal/acre and napropamide at 4 lb/acre, and 6) MNa followed by 1,3-D at 60 and 12 gal/acre and napropamide at 4 lb/acre, respectively. Strawberry transplants were either bare-root or containerized plugs. There were no significant fumigant by transplant type interactions for strawberry plant vigor and root weight per plant, whereas ring nematode (Criconema spp.) and nutsedge (Cyperus rotundus and C. esculentus) populations, and total marketable fruit weight were only infl uenced by fumigant application. The nonfumigated plots had the lowest strawberry plant vigor and root weight per plant in all three locations. In most cases, plant vigor and root biomass per plant increased as a response to any fumigant application. With regard to the transplant type, bare-root transplants had similar plant vigor as plugs in two of the three locations. Fumigation improved nutsedge and ring nematode control. All fumigants had higher early and total marketable yield than the nonfumigated control, whereas transplant type had no effect on total fruit weight.

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Judy A. Thies, Jennifer J. Ariss, Richard L. Hassell, Sharon Buckner, and Amnon Levi

: Where do we need more research? 1999 Annual Research Conference on Methyl Bromide. Alternatives and emissions reductions. Paper #55. 3 Jan. 2015. < www.mbao.org/mbrpro99.html > Memmott, F.D. Hassell, R.L. 2010 Watermelon ( Citrullus lanatus ) grafting

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Stephen R. King, Angela R. Davis, Wenge Liu, and Amnon Levi

; Paplomatas et al., 2002 ; Tsror and Nachmias, 1995 ). Bacterial wilt of tomato caused by Ralstonia solanacearum (Smith) Yabuuchi et al. can be a devastating disease that has few control alternatives. Methyl bromide has not proven effective for control of

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Kirk D. Larson and Douglas V. Shaw

Strawberry (Fragaria ×ananassa L.) runner plant production during a 4-year period was compared on nursery soils treated with methyl bromide (MB) and chloropicrin (CP) mixtures (MB:CP) and three alternative soil treatments: CP, mixtures of 1,3-dichloropropene (Telone®) and CP (DP:CP), and no fumigation (NF). The effect of soil treatment on runner plant production for a single nursery propagation cycle was determined in all 4 years. In 2 years, runner production in a final propagation cycle was also determined as a function of soil treatment in previous cycles. A single propagation cycle in NF soil decreased runner production relative to all other treatments. Treatments with CP at rates of 140 to 191 kg·ha–1 generally decreased runner production significantly (P ≤ 0.05) in comparison with treatment with MB:CP; use of CP at rates ≥303 kg·ha–1 resulted in statistically equivalent runner production. In one trial, use of two DP:CP formulations (516 kg·ha–1 of a 7:3 DP:CP mixture, and 448 kg·ha–1 of a 3:7 DP:CP mixture) significantly reduced and did not affect runner production, respectively, relative to the use of MB:CP. Use of MB:CP in the previous propagation cycle also increased runner productivity in comparison with NF. Runner productivity of planting stock produced with 314 kg·ha–1 of CP did not differ statistically from that of stock produced with MB:CP, but productivity of planting stock on soil treated with 157 kg·ha–1 of CP was intermediate between that on NF and MB:CP-treated soil. Planting stock grown on nontreated soil in two previous propagation cycles produced 25% fewer runner plants than did similar stock grown on MB:CP-treated soil. Productivity of planting stock produced with CP at rates of 280 to 314 kg·ha–1 in two previous propagation cycles did not differ statistically from that of stock produced with MB:CP. Results of meta-analyses indicated that fumigation with MB:CP was more effective in increasing runner production than was CP or NF, regardless of the propagation cycle or rate of application. For mixtures of 1,3-dichloropropene and CP, nursery productivity was maximized by using at least 280 kg·ha–1 of CP.

Open access

Rong Zhang, Zhubing Yan, Yikun Wang, Xuesen Chen, Chengmiao Yin, and Zhiquan Mao

). Preplant soil methyl bromide fumigation to eliminate soil-borne pathogens is recognized as the best means of preventing and controlling ARD in China and abroad. However, its use has been prohibited because it causes pollution and environmental harm ( Koron

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Leonor F.S. Leandro, Lisa M. Ferguson, Frank J. Louws, and Gina E. Fernandez

alternative farming systems compared with large-acreage operations. Growers are currently faced with the serious challenge of implementing alternatives to soil fumigation with methyl bromide ( Wilhelm and Paulus, 1980 ; Yuen et al., 1991 ), banned in 2005