Halosulfuron is a proposed alternative to methyl bromide for managing nutsedges (Cyperus spp.) in several vegetable crops, including cucurbits. Field studies were conducted to evaluate the crop sensitivity to halosulfuron in a spring squash (Cucurbita pepo L.)—fall cucumber (Cucumis sativus L.) rotation from 2000 to 2002. Treatments included application of halosulfuron to the soil surface after forming the bed, but before laying mulch (halosulfuron-PRE), halosulfuron applied through drip irrigation (halosulfuron-DRIP) after forming bed and laying mulch, metham applied through drip irrigation after forming bed and laying mulch, a nontreated control with mulch, and nontreated control without mulch. Each treatment was applied to both direct seeded and transplanted zucchini squash. Halosulfuron treatments reduced squash plant diameter relative to metham, however plant diameters in halosulfuron-PRE (transplant and direct seed) and halosulfuron-DRIP (transplant) treatments were not different from the nontreated control. Halosulfuron-PRE delayed squash fruit production relative to the mulched nontreated control. However, application of halosulfuron-PRE and halosulfuron-DRIP did not reduce squash yield at the conclusion of the season, relative to the nontreated control. Cucumbers were transplanted and direct seeded into previous squash plots and received either an application of halosulfuron-DRIP, or were not treated. Differences in cucumber yields were not detected with second crop treatments. Cucumbers appear to have adequate tolerance to halosulfuron, making it a potential replacement for methyl bromide for nutsedge control. Suppression of early season squash growth by halosulfuron may hinder the adoption of halosulfuron as a methyl bromide alternative for squash.
Theodore M. Webster and A. Stanley Culpepper
Shengrui Yao, Ian A. Merwin and Michael G. Brown
This research was supported in part by USDA-IREE Methyl Bromide Alternatives projects NYC-145560 and 145-530 and by CSREES project NYC 145409. We thank Drs. Lailiang Cheng and Alan Lakso for critical reviews of the manuscript. Journal
Monica Ozores-Hampton, Phillip A. Stansly and Thomas A. Obreza
Methyl bromide will be unavailable to conventional vegetable growers in the year 2005, and it cannot be used by organic growers. Chemical alternatives are more expensive and may also be subject to future restrictions. Non-chemical alternatives like solarization and organic amendments are as yet largely unproven but do offer promise of sustainable solutions free of government regulation. The objective of this study was to evaluate the effects of soil-incorporated biosolids and soil solarization on plant growth, yield, and soil fertility. Main plots were a biosolids soil amendment (37 Mg·ha-1 and a non-amended control. Treated main plots had received some type of organic amendment for the previous 6 years. Sub-plots were fumigated with methyl bromide as they had been for 6 years, or non-fumigated. Non-fumigated plots were further split into solarized and non-solarized plots. Bell pepper (Capsicum annuum `X 3R Aladdin') was grown for 8 months. Nitrogen fertilization was reduced to 50% of the recommended rate in the biosolids plots due to expected N mineralization from the biosolids amendment. Plant biomass was higher in the biosolids plots compared with the non-amended plots but there were no differences in marketable pepper yields between biosolids and non-biosolids plots. Plants grown in solarized soil produced lower plant biomass and yields than the methyl bromide and non-fumigated treatments. Soil pH and Mehlich 1-extractable P, K, Ca, Mg, Zn, Mn, Fe, and Cu were higher in biosolids plots than in non-amended control plots. Soil organic matter concentration was 3-fold higher where biosolids were applied compared with non-amended soil. The results suggest that regular organic amendment applications to a sandy Florida soil can increase plant growth and produce similar yields with less inorganic nutrients than are applied in a standard fertilization program. However, methyl bromide and non-fumigated treatments produced higher yields than soil solarization.
Mario Orozco-Santos, Javier Farías-Larios, José Gerardo López-Aguirre and Jaime Molina-Ochoa
In the Pacific Central region of Mexico, 17,000 ha are cultivated with cucurbitaceous crops. Most are affected with wilt caused by Fusarium oxysporum f. sp. melonis. The use of fungicides, such as methyl bromide, for soil disinfecting is a common practice; however, this practice has adverse effects on beneficial microorganisms, and soil is rapidly infected again. Soil solarization is a sustainable alternative, and it is feasible to be integrated in production systems. It has been used to delay the establishment of symptoms and to reduce the incidence of fusarium wilt in watermelon fields. The objective of this study was to evaluate the effect of soil solarization and methyl bromide on control of fusarium wilt on cantaloupes in western Mexico. The experiment was conducted in the Ranch Fatima located in the municipality of Colima. Severe wilt incidence and damage were previously observed in the cantaloupe cultivar Impac. Dripping irrigation system was used. Treatments established were: 1) solarization; 2) solarization + vermicompost; 3) solarization + chemical products [methyl bromide + chloropicrine (98/2%)]; 4) methyl bromide; and 5) control (without solarization or chemicals). Soil solarization was done during the 6 months before planting using clear plastic mulching (110 thick). A completely randomized design with five treatments and four replications was used. Six beds, 10 m long and 1.5 m wide, were used as experimental unit. Variables registered were: leaf area, leaf number, dry and fresh weight, propagule number, soil temperature, number of diseased plants showing wilt symptoms, and yield. Treatments 1 and 3 exhibited the highest agronomic variable values, and best control of fusarium wilt and fruit yields.
B. de los Santos, C. Barrau, C. Blanco, F. Arroyo, M. Porras, J.J. Medina and F. Romero
support. The field trials and laboratory assays reported herein are part of the national project INIA SC 97-130 on methyl bromide (MB) alternatives to pre-plant soil fumigation in strawberry cultivation.
Monica Ozores-Hampton, Philip A. Stansly, Robert McSorley and Thomas A. Obreza
Many vegetable growers rely on methyl bromide or other soil fumigants to manage soil pathogens, nematodes, and weeds. Nonchemical alternatives such as solarization and organic amendments are as yet largely unproven, but do offer promise of more sustainable solutions. The objective of this study was to evaluate the effects of long-term organic amendments and soil solarization on soil chemical and physical properties and on growth and yield of pepper (Capsicum annuum L.) and watermelon (Citrullus lanatus [Thunb.] Manst.). Main plots consisted of a yearly organic amendment or a nonamendment control. Four subplots of soil sanitation treatments consisted of solarization, methyl bromide, Telone, and nonfumigated. Each subplot was divided into two sub-subplots, one with weed control and one without weed control. Plant biomass was higher in plots with organic amendments than in nonamended plots. There were no differences in marketable pepper and watermelon yields between organic amended and nonamended plots during the 1998-99 and 1999-2000 seasons, respectively. However, higher pepper yields were produced from organic amended plots in the 1999-2000 season. Soil pH and Mehlich 1-extractable P, K, Ca, Mg, Zn, Mn, Fe, and Cu were higher in organic amended plots than in nonamended control plots. Soil organic matter concentration was 3-fold higher in amended soil than in nonamended soil. Effects of soil sanitation and weed management varied with crop and season. The methyl bromide and Telone treatments produced higher yields than soil solarization. In general, weed control did not affect plant biomass and yield for any of the crops and seasons. The results suggest that annual organic amendment applications to sandy soils can increase plant growth and produce higher or comparable yields with less inorganic nutrient input than standard fertilization programs.
Craig Dilley and Gail Nonnecke
Sustainable strawberry production depends on effective weed and soil management. Alternative weed management strategies are needed because few herbicides are registered for use in matted-row strawberry culture. Soil analyses are often measured in terms of chemical and physical properties alone. Measuring biological indicators of soil quality that are sensitive to changes in the environment can enhance these analyses. The experiment compared the effects of four weed management systems on weed growth, soil quality properties, and strawberry yield, growth, and development. Treatments were killed-cover crop mixture of hairy vetch (Viciavillosa) and cereal rye (Secalecereale); compost + corn gluten meal + straw mulch; conventional herbicide; and methyl bromide soil fumigation. Results indicated that there were no differences in percentage of weed cover or number of strawberry runners between the four weed management treatments in the planting year (July or Aug. 2004). The soil quality parameters, infiltration rate, soil bulk density, earthworm number, and total porosity were similar for all treatments. Plots that received the straw mulch treatment had a soil volumetric water content 20% higher and air-filled porosity that was 26% higher than the average of other treatments. Although treatment plots received similar N, leaf nutrient analysis showed that plants receiving the straw mulch + corn gluten meal treatment had a similar amount of total N when compared to the conventional and methyl bromide treatments, but was 21% higher than the killed-cover crop treatment.
James S. Gerik
Field trials were conducted to test fumigants as alternatives to methyl bromide (MB) for production of hybrid freesia (Freesia × hybrida). One trial compared rates of 1,3-dichloropropene (DP) combined with chloropicrin (CP); the second trial compared iodomethane (IM) together with CP, DP:CP, and furfural with and without metham sodium; and the third trial compared rates and formulations of IM:CP to the standard MB:CP treatments. Most treatments reduced populations of Pythium spp. and controlled weeds compared to the untreated controls. Formulations of IM:CP reduced the incidence of disease caused by Fusarium oxysporum. Treatments of IM:CP performed as well as MB:CP, and treatments of DP:CP performed as well as IM:CP. Presently only the DP, CP and metham sodium formulations are registered for use on ornamental crops. Registration of the IM formulations will improve the options available to cut flower growers for management of plant pathogens and weeds.
Bielinski M. Santos and James P. Gilreath
Among the current methyl bromide alternatives under study, propylene oxide (Propozone) has shown potential to control soilborne diseases, nematodes, and weeds in polyethylene-mulched tomato. However, further research is needed to determine the appropriate application rates to control nutsedge in the crop. Also, the effect of this fumigant on tomato nutrient absorption has not been determined yet. Therefore, field trials were conducted for this purpose in Bradenton, Fla. Tested rates of Propozone were 0, 190, 380, 570, 760, and 950 L·ha–1 and were shank-applied in raised planting beds three weeks before `Florida 47' tomato transplanting. Examined data indicated that there was a rapid decrease in nutsedge density with 570 L·ha–1. For phosphorus (P) and potassium (K) foliar content, there was a linear increase of P concentrations as rate increase, whereas K content increased rapidly after 190 L·ha–1. The highest tomato yields were obtained with 760 and 950 L·ha–1 of Propozone.
Krista C. Shellie and Robert L. Mangan
`Dancy' tangerines (Citrus reticulata Blanco) were harvested after color break and exposed to high-temperature forced air (HTFA) at 45C for 3.5 or 4 h to kill Mexican fruit fly [Anastrepha ludens (Loew)] larvae. Heat-treated and control fruit were stored subsequently for 2 weeks at 4C. Tangerines harvested after color break (naturally degreened) tolerated exposure to HTFA in a similar fashion as tangerines harvested before color break and degreened by postharvest exposure to ethylene. Titratable acidity (TA) was significantly lower after heat treatments. Flavor, soluble solids concentration, external appearance, incidence of decay, percent juice yield, percent weight change, and flavedo color of heat-treated fruit were not different from nonheat-treated, control fruit. Exposure to HTFA is a viable alternative to methyl bromide for disinfestation of `Dancy' tangerine.