Efficacy of 1,3-dichloropropene plus chloropicrin gelatin capsule formulation for the control of soilborne pests

A gelatin capsule (gel cap) formulation of the mixture of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) has been developed to reduce environmental emissions and potential human exposure from the use of 1,3-D/CP as a soil fumigant. The objective of the present study was to evaluate the biological efficacy of 1,3-D/CP gel cap formulations under greenhouse trial conditions. The current results indicate that a 1,3-D/CP gel cap formulation at 30 or 50 g a.i. m⁻² can reduce the soil populations of Fusarium spp., Phytophthora spp., Pythium spp. and Meloidogyne spp.. In all tested crops, the 1,3-D/CP gel cap formulation provided marketable yields that were significantly higher than untreated controls and equal to the methyl bromide and 1,3-D/CP liquid injection treatments. Yields of tomato and a subsequent melon crop in plots treated with 1,3-D/CP gel cap were 93% and 87% greater, respectively, than the control. The yields of grafted cucumber and the subsequent balsam pear crop were increased by 16% and 201% respectively, compared to the control. The present study confirms that the tested 1,3-D/CP gel cap formulation provides a promising method for soil pest and disease control and reducing environmental emissions and potential human exposure in greenhouse vegetable cultivation.     

Effectiveness of 1,3-dichloropropene as an alternative to methyl bromide in rotations of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) in China

Replicated field trials were conducted to determine the effect of 1,3-dichloropropene (1,3-D) as a potential alternative for methyl bromide (MeBr) in tomato–cucumber rotations in two successive cropping seasons in China. Fumigation with MeBr (400 kg ha⁻¹), three 1,3-D doses (180, 120 and 90 l ha⁻¹), an avermectin dose (187.5 g ha⁻¹) and an untreated control were compared. Tomato data revealed that MeBr was generally superior to the treatments involving 1,3-D and avermectin, which in turn were superior to the control, for improving tomato crop yield and inhibiting Meloidogyne incognita, weeds and mortality caused by plant disease. In a successive cucumber crop, all fumigants tested except avermectin, showed significant continual influence in the same plots. In most cases, the highest 1,3-D dose was comparable to MeBr. Overall, in both growth seasons, 1,3-D at the dose of 180 l ha⁻¹ was as effective as MeBr in increasing plant height, yield and in reducing the incidence of soil borne disease, especially in maintaining excellent M. incognita control, but it provided only moderate control of weeds. On the basis of these results, combining 1,3-D with other alternatives to MeBr, is recommended for satisfactory control of soil pests in tomato–cucumber rotations in China.     

Effects of emission reduction surface seal treatments on pest control with shank-injected 1,3-dichloropropene and chloropicrin

The phase-out of methyl bromide for preplant soil fumigation has resulted in an increased reliance on combinations of 1,3-dichloropropene and chloropicrin in many annual and perennial cropping systems in California. However, these fumigants also can have negative environmental and human health consequences and considerable research has been conducted on methods to minimize emission of these products from the soil to the atmosphere. To ensure that pest control efficacy is not compromised by emission reduction techniques, this research was conducted to simultaneously evaluate the effects of several surface seal techniques on fumigant emissions and the efficacy of soil-borne pest control with a mixture of 1,3-dichloropropene + chloropicrin. Results indicated that the interaction between emission reduction techniques and pest control efficacy can be complicated. For example in the 2006 trial, some surviving nematodes were observed in plots with both high (manure plus high density polyethylene film) and intermediate (pre-irrigation) 1,3-D cumulative emissions which suggested that emission loses are not solely responsible for some pest control failures. Weed control tended to be better with plastic film treatments and worse with pre-fumigation soil moisture manipulations but was affected less than expected by intermittent water seals. Although pest control clearly was affected by surface seal techniques, especially in shallow soil layers, some differences in nematode and weed control could not be explained solely by surface seals. These results underline the complex interactions among soil moisture and other environmental factors, application techniques, and emission reducing surface seal treatments. As new techniques and technologies become available to reduce fumigant emissions, we recommend that research include pest control efficacy evaluations before any emerging techniques are required by regulators or implemented by growers.     

Evaluation of non-fumigant alternatives to methyl bromide for weed control and crop yield in California strawberries (Fragaria ananassa L.)

In California, USA, agricultural fumigant use regulations hinder the complete transition from methyl bromide (MB) to alternative fumigants. Alternative fumigants such as 1,3-dichloropropene (1,3-D) and chloropicrin (Pic) are being used on approximately half of California conventional strawberry production fields. Geographic use limits and buffer zones set by the California Department of Pesticide Regulation for 1,3-D + Pic restrict a more complete replacement of MB. Due to the regulatory constraints and public resistance to fumigant use, it is necessary to develop fumigant-free strawberry production systems. Trials were conducted during the 2007/2008 and 2008/2009 strawberry growing seasons at Salinas and Watsonville, California. Non-fumigant treatments including steam, mustard seed meal (MSM), Muscodor albus, and furfural, fertilizers including Mustard Products & Technologies fertilizer and stabilised urea, and fungicide treatments including AG3(NP), fludioxonil + mefenoxam (mfx), and mfx + thiophanate-methyl were evaluated for weed control and strawberry fruit yield, and compared to MB + Pic (MBPic) standard soil fumigation and an untreated control. Steam treatment applied pre-plant to achieve soil temperature of ≥70 °C for 20 min up to 25 cm soil depth consistently provided weed control similar to the MBPic standard soil fumigation. Use of oxyfluorfen herbicide prior to fungicide applications in 2008/2009 also controlled weeds similar to the MBPic standard soil fumigation. Strawberry yields in steam-treated plots with the exception of steam alone in 2007/2008 at Salinas, were comparable to MBPic. At Watsonville in 2008/2009, treatment effect on strawberry yields was insignificant. Yields in furfural and MSM treatments were comparable to MBPic only in some years or sites. With the exception of steam, none of the treatments can be considered viable replacement to MB.     

Effects of the nematicide 1,3-dichloropropene on weed populations and stem canker disease severity in potatoes

The soil fumigant 1,3-dichloropropene (1,3-D) has been used in the UK for the control of potato cyst nematodes (PCN), Globodera pallida (Stone) and Globodera rostochiensis (Wollenweber), but its potential herbicidal activity has not been extensively investigated in this country. Field and glasshouse studies were therefore conducted to evaluate the potential of 1,3-D for the control of weeds in potatoes, and observations were made on the severity of potato stem canker, caused by the fungus Rhizoctonia solani Kühn [teleomorph: Thanatephorus cucumeris (Frank) Donk]. Autumn application of 1,3-D at 211.5 L active substance (a.s.) ha⁻¹ significantly suppressed the number of germinating weeds and the percentage of weed ground cover by 83% and 79%, respectively, relative to controls. There were also species-specific significant decreases (field pansy, Viola arvensis, in particular) in the number of weed seeds germinating in field soil in the glasshouse post-1,3-D treatment. The effect of 1,3-D declined in time and single (autumn or spring) or combined application produced a slight, but not significant, reduction in the number of weeds germinated on potato ridges relative to those recorded in untreated soil. The severity of stem canker on potato plants was not significantly reduced by 1,3-D but both mean number and weight of stems per plant were significantly increased compared with plants from untreated plots. These studies demonstrated that 1,3-D, in addition to giving PCN control, has efficacy against weeds; implications are the potential for reduced herbicide input in the crop rotation with accompanying economic and environmental benefits.     

Fumigation in the 21st century

The last quarter of the 20th century has seen the withdrawal of many compounds formerly used as fumigants. Methyl bromide, the fumigant with the widest range of applications is scheduled for worldwide withdrawal from routine use as a fumigant in 2015 under the directive of the Montreal Protocol on ozone-depleting substances. Phosphine, the only other commodity fumigant available worldwide, used principally on bulk grain but also on dried fruit, nuts, cocoa, coffee and bagged rice, is currently under regulatory review in the USA and Europe. The prospects for the continued use of fumigants to protect plant and animal health and commodity trading are discussed in the context of mounting pressures on compounds due to registration requirements, atmospheric emission controls, fears on safety or health grounds, the incidence of resistance, and the need to achieve increasingly high standards of pest control in international trade. Some recent research results relating to fumigant toxicity and gas application technology are presented which indicate ways in which the use of some of the few remaining fumigants can be extended in the 21st century.     

Effects of 1,3-dichloropropene on nematode,weed seed viability and soil-borne pathogen

1,3-dichloropropene (1,3-D, C₃H₄Cl₂) is one of the potential candidates as soil disinfectant since the restriction of methyl bromide (MeBr) in soil fumigation due to its ecological risk. Its nematode, soil-borne pathogen and weed control efficacies were evaluated in a laboratory dose-response study and in two commercial tomato fields. Laboratory studies found that the seeds of Digitaria chinensis Hornem. were the most sensitive to soil fumigation with 1,3-D, followed by Eleusina indica (Linn.) Gaertn., Echinochloa crusgalli (L.) Beauv. and Amaranthus retroflexus L. with the LC₉₀ values between 14.23 and 73.59 mg kg⁻¹ soil. Among the pathogens, Phytophthora capsici Leonian was the most sensitive and Fusarium oxysporum f. sp. fragariae was the least sensitive to 1,3-D fumigation with the LC₅₀ values were 0.24 and 1.55 g m⁻². Rhizoctonia solani Kühn., Phytophthora nicotianae var. nicotianae and Botrytis cinerea Persoon exhibited intermediate susceptibility. Field trials revealed that 1,3-D applied to the field at 180, 120 and 80 L ha⁻¹ could suppress Meloidogyne incognita root galling while maintaining high tomato marketable yields, better than Dazomet at the concentration of 400 kg ha⁻¹. Our results indicated that 1,3-D was an excellent nematicide and could provide good to moderate weed and pathogen control. Based on our results, 1,3-D, in combination with other alternatives to MeBr is recommended to reach an integrated pest management.     

Efficacy of fumigant treatments and inoculum placement on control of Macrophomina phaseolina in strawberry beds

Soil disinfestation is one of the main concerns of strawberry growers. The phased-out of methyl bromide (MeBr) and the lack of equally effective fumigants has increased the difficulty in controlling soilborne pathogens such as Macrophomina phaseolina, causal agent of charcoal rot. Soil fumigant treatments were tested in Dover, Florida during the 2012–13, 2013–14 and 2014–15 seasons. The treatments included MeBr as a standard and common alternatives such as chloropicrin (PIC), 1,3-dichloropropene (1,3D), dimethyl disulfide (DMDS), potassium N-methyldithiocarbamate (Kpam) and sodium methyldithiocarbamate (Vapam). The efficacy of different fumigation rates and application methods was also investigated. Treatment effects were evaluated using sclerotia of M. phaseolina buried in bags 7.6 and 20.3 cm deep in the center of the bed, or 7.6 cm deep on the side of the bed (7.6 s). Additionally, strawberry crowns infected with M. phaseolina were buried 7.6 cm deep in the center of the bed during the 2012–13 and 2013–14 growing seasons. At the end of the 2013–14 and 2014–15 growing seasons, plant mortality and charcoal rot incidence (%) were also determined. Except for 1,3-dichloropropene:chloropicrin 39/60, most treatments were effective in reducing the colony forming units (CFUs) of M. phaseolina in buried bags or crowns buried at the center of the bed and reduced percent of charcoal rot incidence each season. Most treatments applied by shank produced similar reductions in inoculum levels at the center and sides of the bed, whereas drip treatments effectively reduced inoculum in bags buried at both depths in the center of the bed, but not at the side of the bed. Thus, one of the main problems of the current fumigants is poor distribution in the soil beds and strawberry growers should consider application methods that will achieve a more uniform distribution of the fumigants.     

Efficacy of reduced rate fumigant alternatives and methyl bromide against soilborne pathogens and weeds in western forest nurseries

Preplant soil fumigation is commonly used to control soilborne pathogens and weeds in forest seedling nurseries of Oregon and Washington. However, lower chemical inputs are desired to meet state and federal application regulations, to minimize buffer zone size requirements, and to help protect the environment. Therefore, the objectives of this research were to evaluate the efficacy of three reduced rate soil fumigants under totally impermeable film (TIF) in managing soilborne diseases and weeds, and to determine if combined applications of up to four biocontrol agents improved soilborne disease control. Reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene, all applied in combination with chloropicrin, were effective in decreasing soil populations of Pythium and Fusarium as well as the presence of Pythium in root debris from the previous crop. The roots of Douglas-fir (Pseudotsuga menziesii) seedlings transplanted into each fumigant treatment were also colonized less by Pythium and Fusarium than those transplanted into nonfumigated control plots. However, biocontrol treatments were not effective against either pathogen. Weed biomass and weeding times were also significantly reduced by fumigation. Application costs were similar for all three fumigant treatments, but seedling size was largest from the methyl bromide and metam sodium treatments followed by the 1,3-dichloropropene treatment. Based on the results of this study, reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene show promise in managing soilborne diseases and weeds in forest nurseries.     

Effects of 1,3-dichloropropene plus chloropicrin on weed seed germination

Telone C-35, a commercial formulation of 1,3-dichloropropene (1,3-D) and chloropicrin (CP), is one of the potential replacements to methyl bromide (MB) for soil fumigation. A laboratory dose–response study and two field trials in tomato were conducted to evaluate their weed control efficacy and their effect on tomato yield. Laboratory studies found that the seeds of Digitaria chinensis were the most sensitive to soil fumigation with Telone C-35, followed by Eleusina indica, Portulaca oleracea and Stellaria media with the LC₅₀ values between 3.35 and 11.68 mg kg⁻¹ soil. Field trials revealed that Telone C-35 applied to the field at 327, 243 and 164 L ha⁻¹ could suppress the percentage of germination weed seeds while maintaining high tomato marketable yields, with no significant differences between MB + CP and the higher two Telone C-35 rates. The yield data from both seasons indicated that all Telone C-35 treatments had a positive effect on tomato yield; there was a 32%–62% increase the mean marketable tomato yield. Our results indicated that Telone C-35 was an excellent MB alternative and could provide acceptable weed control efficacy. Based on our results, Telone C-35, in combination with other alternatives to MB, is recommended to achieve integrated pest management.     

Efficacy of chloropicrin application by drip irrigation in controlling the soil-borne diseases of greenhouse pepper on commercial farms in Poland

Three demonstration experiments were conducted on commercial greenhouse farms to assess the efficacy of chloropicrin (CP), applied by drip irrigation, in controlling Verticillium wilt and root rot disease complex of bell pepper, in comparison with dazomet at 40 g m⁻². Chloropicrin was applied through drip irrigation system at 20, 30 and 40 g m⁻² of emulsified commercial formulation. The concentration of CP in water was constant, and the required doses were obtained by delivering different amounts of the irrigation water per area unit (from 12.5 to 33 mm). The highest mean efficacy in reducing the inoculum density of Verticillium dahliae in the soil at all locations was obtained after CP application at 30 and 40 g m⁻², about 85 and 86%, respectively. The number of viable microsclerotia recovered from the soil on the day of pepper planting was significantly correlated with the final incidence of Verticillium wilt disease (r = 0.962). The highest mean efficacy in controlling Verticillium wilt of pepper (86.4%) was obtained after soil treatment with CP at 40 g m⁻², and ranged from 80.2 to 95.6%. The yield was stronger correlated with root rot severity (r = −0.849**) than with progression of Verticillium wilt, expressed by AUDPC (r = −0.651**). The dominant soil-borne pathogen responsible for pepper root rot was Colletotrichum coccodes. All chemical treatments provided a significant reduction in root rot severity compared to the untreated control. On-thefarm evaluation revealed that soil fumigation with drip-applied chloropicrin presents a feasible option for pepper growers.     

Management of 1,3-dichloropropene in pineapple for efficacy and reduced volatile losses

Two application methods, single- and double-chisel injection of the fumigant nematicide 1,3-dichloropropene (1,3-D) were evaluated for efficacy and environmental fate in pineapple field experiments. The objectives were to compare the 1,3-D soil distribution between injection methods, evaluate volatile losses to the atmosphere, and to determine efficacy with each method. In a small-plot field experiment, 1,3-D (224, 337, and 393 1 ha⁻¹) was manually injected 30 cm deep with fumiguns to simulate the commercial practice of a single- or double-chisel injection per planting bed. 1,3-D concentrations in the soil atmosphere and in soil samples were determined and compared to nematode control. In two large-scale field experiments, 1,3-D (224 1 ha⁻¹) was applied with commercial injection equipment with and without polyethylene mulch. Air monitoring for 1,3-D showed a reduction in 1,3-D air emissions with single-chisel injection compared with double-chisel injection. In all experiments, the two injection methods resulted in equivalent 1,3-D concentrations in the plant line. Single-chisel injection resulted in improved retention of 1,3-D within the planting bed as shown by low 1,3-D soil concentrations in the interbed. Nematode counts and bioassay studies found equivalent nematode control in the planting bed with either injection method. The single-chisel method, however, resulted in reduced nematode control in the interbed region.     

Effect of pre-plant soil fumigants on Agrobacterium tumefaciens, pythiaceous species,and subsequent soil recolonization by A. tumefaciens

Paradox (Juglans hindsii × J. regia), the dominant rootstock used in the California walnut industry, is susceptible to crown gall caused by Agrobacterium tumefaciens. In practice, soil fumigation has been a common pre-plant management strategy for crown gall, but even the industry standard, methyl bromide (MeBr), results in inconsistent disease control. To examine MeBr efficacy and identify potential alternatives, combinations of 1,3-dichloropropene (1,3-D), chloropicrin, iodomethane, dazomet, and metam-sodium were examined. Except for 1,3-D alone, all treatments reduced A. tumefaciens and Phytophthora cactorum populations below detection limits. MeBr eliminated A. tumefaciens populations in buried gall tissue, but a combination of 1,3-D and chloropicrin (TC35) did not. An additional 280 kg/ha of chloropicrin in addition to TC35 eliminated A. tumefaciens populations in buried gall tissue. Of the treatments tested, TC35 was the best alternative to MeBr given its efficacy on soil populations of A. tumefaciens and P. cactorum and potential suppressiveness to soil recolonization by A. tumefaciens. MeBr reduced general aerobic bacterial populations below detection limits producing a temporary biological vacuum. A. tumefaciens reintroduced in soils treated with MeBr and TC35 reached significantly higher populations than in non-fumigated soil. However, A. tumefaciens populations in TC35-treated soil were 100-fold lower than MeBr-treated soil 110 d after reintroduction. Increased recolonization rates resulting in higher subsequent soil populations could be a mechanism underlying the observed inconsistent crown gall control after MeBr application.     

Efficacy of 1,3-dichloropropene plus chloropicrin application methods in combination with pebulate and napropamide in tomato

Small-plot research and large-field validations were conducted to determine the effect of 1,3-dichloropropene (1,3-D)+chloropicrin (Pic) application methods in combination with the herbicides pebulate and napropamide on pest control in fresh market tomato (Lycopersicon esculentum Mill.). In both the small-plot trials and the large-validation fields, various treatments compared the efficacy of soil fumigants and herbicides based on methyl bromide, in-bed and broadcast applications of 1,3-D+Pic, pebulate, and napropamide. The results consistently indicated that either in-bed or broadcast applications of 1,3-D+Pic in combination with pebulate and napropamide are equally effective against the weed Cyperus spp., the nematodes Tylenchorhynchus spp., Belonolaimus longicaudatus, and Meloidogyne spp., and the soilborne disease Fusarium oxysporum f.sp. lycopersici in fresh market tomato. Therefore, broadcast 1,3-D+Pic application can reduce personnel exposure and poisoning risks, without losing pest control efficacy.     

Stable high yields with zero tillage and permanent bed planting?

Subtropical highlands of the world have been densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen throughout this agro-ecological zone. This article considers practices that would sustain higher and stable yields for wheat and maize in such region. A long-term field experiment under rainfed conditions was started at El Batán, Mexico (2240 m a.s.l.; 19.31°N, 98.50°W; fine, mixed, thermic, Cumulic Haplustoll) in 1991. It included treatments varying in: (1) rotation (continuous maize (Zea mays) or wheat (Triticum aestivum) and the rotation of both); (2) tillage (conventional, zero and permanent beds); (3) crop residue management (full, partial or no retention). Small-scale maize and wheat farmers may expect yield improvements through zero tillage, appropriate rotations and retention of sufficient residues (average maize and wheat yield of 5285 and 5591 kg ha⁻¹), compared to the common practices of heavy tillage before seeding, monocropping and crop residue removal (average maize and wheat yield of 3570 and 4414 kg ha⁻¹). Leaving residue on the field is critical for zero tillage practices. However, it can take some time—roughly 5 years—before the benefits are evident. After that, zero tillage with residue retention resulted in higher and more stable yields than alternative management. Conventional tillage with or without residue incorporation resulted in intermediate yields. Zero tillage without residue drastically reduced yields, except in the case of continuous wheat which, although not high yielding, still performed better than the other treatments with zero tillage and residue removal. Zero tillage treatments with partial residue removal gave yields equivalent to treatments with full residue retention (average maize and wheat yield of 5868 and 5250 kg ha⁻¹). There may be scope to remove part of the residues for fodder and still retain adequate amounts to provide the necessary ground cover. This could make the adoption of zero tillage more acceptable for the small-scale, subsistence farmer whose livelihood strategies include livestock as a key component. Raised-bed cultivation systems allow both dramatic reductions in tillage and opportunities to retain crop residues on the soil surface. Permanent bed treatments combined with rotation and residue retention yielded the same as the zero tillage treatments, with the advantage that more varied weeding and fertilizer application practices are possible. It is important small-scale farmers have access to, and are trained in the use of these technologies.     

Soil organic carbon sequestration as affected by tillage, crop residue, and nitrogen application in rice–wheat rotation system

Despite being a major domain of global food supply, rice?Cwheat cropping system is questioned for its contribution to carbon flux. Enhancing the organic carbon pool in this system is therefore necessary to reduce environmental degradation and maintain agricultural productivity. A field experiment (November 2002?CMarch 2006) evaluated the effects of soil management practices such as tillage, crop residue, and timing of nitrogen (N) application on soil organic carbon (SOC) sequestration in the lowland of Chitwan Valley of Nepal. Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) were grown in rotation adding 12?Mg?ha^?1?y^?1 of field-dried residue. Mung-bean (Vigna radiata L.) was grown as a cover crop between the wheat and the rice. Timing of N application based on leaf color chart method was compared with recommended method of N application. At the end of the experiment SOC sequestration was quantified for five depths within 50?cm of soil profile. The difference in SOC sequestration between methods of N application was not apparent. However, soils sequestered significantly higher amount of SOC in the whole profile (0?C50?cm soil depth) with more pronounced effect seen at 0?C15?cm soil depth under no-tillage as compared with the SOC under conventional tillage. Crop residues added to no-tillage soils outperformed other treatment interactions. It is concluded that a rice?Cwheat system would serve as a greater sink of organic carbon with residue application under no-tillage system than with or without residue application when compared to the conventional tillage system in this condition.     

Note on effects of soil surface crust on the grain yield of sorghum (Sorghum bicolor) in the Sahel

The prominent effects of a soil surface crust on crop production, impedance to seedling emergence and reduced infiltration rate, were examined using a quantitative land evaluation model under the Sahelian environmental and soil conditions of north-central Burkina Faso. The model integrated data from climate, soil and crop for quantifying potential grain yield of sorghum (Sorghum bicolor), grown on a sandy loam soil for 14 production years (1977–1990). Crust development was induced using `simulated rainfall' with an intensity of 75 mm h⁻¹ from a 2 m height. Results revealed that seeding sorghum in small holes without sufficiently breaking the surface crust depressed grain yield. Observed and potential yield correlated closely over a 7-year period (r = 0.79, p < = 0.05). Substantial yield gap was found between estimated potential yield (crust broken scenario set to 75% of the predicted yield) and observed, indicating however, the possibility of significantly improving yield by using appropriate tillage to break the crust before seeding.     

Using dazomet to reduce broomrape seed banks in soils with low moisture content

Dazomet (Basamid^®) is a dry powder formulation that releases the toxic gas methyl isothiocyanate for the control of soil borne pests and weed seeds when applied to moist soils. We evaluated its efficacy for destroying Phelipanche mutelii (branched broomrape) seed banks. Dazomet is typically used where effectiveness can be improved with the addition of water but we examined its performance in soils with low moisture content in container experiments and field trials. In containers, less than 10% of P. mutelii seed remained viable 30 days after dazomet applications of 112.8–338.4 kg ha⁻¹ at soil moisture content from 0.05 to 0.15 g g⁻¹. Seeds buried at a depth of 5 cm needed to be in contact with the product for longer than one week before viability was affected. An initial field trial did not detect a decline in seed viability 7 days after dazomet application. Viability assessments in a second field trial were made 30 days after dazomet application with an airseeder at a rate of 338.4 kg ha⁻¹. Less than 10% of P. mutelii seeds at a depth of 5 cm survived and dazomet was as effective as two other soil fumigants, methyl bromide and a methyl iodide/chloropicrin mixture. The release of methyl isothiocyanate is reduced in soils in containers with low soil moisture content but occurs over a long time period. Methyl isothiocyanate dissipated more rapidly in soils in containers with higher soil moisture content and at lower dazomet application rates. A higher application rate is required in the field to ensure the dazomet powder is evenly distributed through the soil profile and there is adequate methyl isothiocyanate resident in the top soil layer to achieve seed kill. This has consequences for plant back times in fumigated land following dazomet application.     

Effects of soil disinfection on health status,growth and yield of strawberry stock plants

Two strawberry nursery field trials comparing soil disinfection with different fumigants (metam sodium, dazomet, chloropicrin, chloropicrin +1,3D) and a steaming system exploiting the exothermic reaction between steam and CaO (Bioflash System™) were conducted in 2010–2012 to evaluate the effect of treatments on Verticillium dahliae Kleb. inhabiting the soil, and on plant health, growth and yield of strawberry daughter plants. Chemical fumigants and the Bioflash System™ decreased the number of V. dahliae colonies in the soil, which corresponded to reduced incidence of Verticillium wilt (efficacy about 80%). The use of chemical fumigants had a positive impact on the size of the mother plants. The surface area covered by plants grown on the treated plots was 1.1–1.7 times larger than plants grown on non-fumigated control plots. The number of runners, as well as daughter plants, produced from plants grown on plots treated with all chemical fumigants was significantly higher than in the non-fumigated control or in the plots treated with the Bioflash System™. The disinfection treatments significantly increased the yield of marketable daughter plants, approximately 1.5–3 times higher in comparison to plants grown on control plots. Steam disinfection with the Bioflash System™ was the least effective treatment in this respect. The differences in marketable plants yield among the chemical fumigants significantly affected the net marginal return and the return on investment of the crop. In this respect, the steam disinfection was economically efficient only in one season. The efficacy in controlling Verticillium wilt even with low doses of metam sodium and dazomet and their influence on yield and quality of daughter plants is confirming the feasibility of these fumigants for strawberry nursery management.     

Two-year investigations on the integrated control of weeds and root parasites in Virginia bright tobacco (Nicotiana tabacum L.) in central Italy

The current revision of pesticides in the EU, including those for soil disinfection, will necessitate the introduction of alternative integrated methods for the control of weeds and parasites in tobacco production in Italy. The present study compared the effect of some soil fumigants, biocontrol agents, cover crops and mulching for the control of tobacco weeds and root parasites. The results show that the different soil fumigants had an important role in increasing tobacco yield, due to their ability to control weeds and the nematodes Meloidogyne incognita and Meloidogyne javanica. In particular, a typical nematicide like 1,3-dichloropropene did not control only nematodes but also Portulaca oleracea, a common weed in Italian tobacco fields. Fenamiphos, although showed a certain efficacy in controlling root-knot nematodes, did not generally have a satisfactory activity at the dose of 40 g m⁻¹; cover crops like Trifolium squarrosum and Eruca sativa and a commercial formulation composed by the endomycorrhizal fungi Glomus spp., the antagonistic fungi Trichoderma spp. and bacteria including Pseudomonas, Bacillus and Streptomyces (Micosat F, CCS Aosta, Italy), were not able to control root tobacco diseases. The investigations confirmed that a prolonged monoculture causes a reduction of black root rot. Soil fumigation and the use of Good Agricultural Practices (GAP), influencing the inoculum density of Chalara populations, can contribute to the maintenance or to the establishment of particularly unfavourable conditions for the saprophytic growth of the pathogen, leading to a lower development of the disease.