Effect of Anaerobic Soil Disinfestation and Mustard Seed Meal for Control of Charcoal Rot in California Strawberries

ABSTRACT

Anaerobic soil disinfestation (ASD) and mustard seed meal (MSM) appear to be promising non-fumigant alternatives for soilborne pathogens control. However, studies of their effect on charcoal rot caused by Macrophomina phaseolina in California strawberry are limited. A demonstration field trial with ASD with rice bran 20 t ha^–1 (ASD-RB), MSM 4.5 t ha^–1 (MSM), and ASD with rice bran 6.7 t ha^–1 + MSM 4.5 t ha^–1 (ASD-RB+MSM) treatments was conducted in a M. phaseolina-infested organic field in Oxnard, CA. A doubling of fruit yields relative to the grower standard, and a reduction in plant mortality by M. phaseolina, was achieved by ASD-RB. MSM failed to control M. phaseolina and resulted in fruit yields that were more than 20% below the ASD-RB yield. Fruit yield in the ASD-RB+MSM plot was intermediate between ASD-RB and MSM. Treatment effects on soil pH, EC, inorganic N dynamics, and soil microbial communities were also examined.     

Non-Fumigant Treatments and Their Combinations Affect Soil Pathogens and Strawberry Performance in Southern California

ABSTRACT

Finding effective non-fumigant solutions to soil disinfestation is an international priority for sustainable strawberry production. In these studies at Ventura, California, combinations of steam, solarization, and mustard meal were evaluated to manage troublesome soil-borne pathogens: Macrophomia phaseolina and Fusarium oxysporum. Treatments containing steam and solarization reduced levels of these pathogens in soil 70–96% compared to untreated soil and had lower rates of late season pathogen-related plant mortality. All treatments improved plant canopy growth and fruit production of ‘San Andreas’ strawberry 58% to 83% compared to untreated control. Even though these treatments did not eradicate pathogen spores and sclerotia in soil, they enhanced early and whole season fruit production and when feasible can be applied in non-fumigated and organic strawberry fields to help sustain production.     

Soil Disinfestation with Steam: A Review of Economics,Engineering, and Soil Pest Control in California Strawberry

ABSTRACT

Increasingly stricter fumigant regulations will limit their use and require effective non-fumigant treatments if large-scale strawberry production is to continue in California. Steam has long been used for soil disinfestation in greenhouse soils where it controls most soil pests. The challenge of field-scale soil disinfestation with steam in place of fumigants is availability of machinery capable of treating a large acreage in a timely manner while making the most efficient use of fuel and water. Steam can be a component within an integrated set of fumigant and non-fumigant practices. Steam used together with other practices may permit technically and economically sustainable strawberry production into the future by allowing growers to adapt to more stringent fumigant use restrictions. It may be possible to overcome some of the limitations of steam because steam generator technology has advanced in recent years as well as recent developments in co-applications with steam, including exothermic compounds co-applied with steam and mustard seed meal co-applied with steam. Regarding steam generator technology, direct-fire steam generators are more energy efficient than traditional steam boilers and avoid the hazards of steam pressure vessels. Steam is arguably the most effective non-fumigant method of soil disinfestation and it likely has a role in a future California strawberry production system that is forced to use much less fumigant than it does at present.     

Status of Macrophomina phaseolina on Strawberry in California and Preliminary Characterization of the Pathogen

ABSTRACT

Macrophomina crown and root rot has become a significant soil-borne disease issue in California. For many locations in the state, the disease is associated with fields that are no longer pre-plant, flat field fumigated with methyl bromide + chloropicrin. Inoculation experiments indicated that some differences in strawberry cultivar susceptibility to Macrophomina phaseolina were seen a short time after the inoculation, but as disease progressed such differences did not persist. Preliminary characterization studies of Macrophomina phaseolina isolates from strawberry indicated that such isolates may have a host preference for strawberry. Macrophomina phaseolina isolates from watermelon, thyme, and apple failed to cause disease in strawberry. Five cover crop species, which can be rotated with strawberry, did not develop disease when inoculated with strawberry isolates. In preliminary analysis using simple sequence repeat markers, isolates obtained from strawberry formed a separate group compared to isolates recovered from other known Macrophomina phaseolina hosts.     

蔬菜土传病害生态防控技术研究

蔬菜土传病害是由土传病原菌引起的一类维管束病害,对我国的蔬菜行业造成严重危害。在分析当前防治措施的基础上,提出采用有机肥调控土壤生态环境防治蔬菜土传病害。指出有机肥除能改善土壤环境外,也能向土壤中引入大量的有益微生物,用时有机肥能通过营养竞争、直接寄生和分泌抗生素作用来抑制土传病害,从而实现农业蔬菜的可持续发展。     

草莓连作土壤灭菌与施用有机肥对根际土壤酚酸及土壤酶活性的影响

针对草莓连作土壤灭菌后与正茬相比草莓植株根系生长受到抑制,研究了连作土壤灭菌与施用不同种类肥料对草莓幼苗（移栽60 d后）根系分泌酚酸及土壤相关酶活性的影响。结果表明：连作土壤灭菌与施用有机肥料处理显著提高了草莓植株根际土壤中酚酸的含量,其中施用蚯蚓粪（经蚯蚓食用处理的牛粪）的增幅显著低于施用牛粪。土壤灭菌处理后施加不同肥料,土壤多酚氧化酶活性均能较快恢复;有机肥较无机肥能显著促进过氧化氢酶活性的恢复;蚯蚓粪较牛粪和无机肥能显著促进土壤脲酶活性的提高;土壤蔗糖酶受土壤灭菌影响显著降低且施加不同肥料对其没有显著地影响。综上所述,对于草莓连作土壤,无论灭菌与否,施用蚯蚓粪较牛粪能减轻连作障碍中的酚酸化感效应,促进脲酶等土壤相关酶活性提高,是缓解连作障碍及连作土壤灭菌对草莓植株生长发育影响的有效措施。     

Planting density for grafted melon as an alternative to methyl bromide use in Mexico

One of the major challenges of melon (Cucumis melo L.) yield is the decrease of fruit yield and quality caused by soil diseases. Soil disinfection with methyl bromide (MB) has been used to prevent soil-borne diseases damage; however, use of MB is being restricted because this substance damages the ozone layer. Searching for new MB alternatives, field experiments were carried out in open fields in soils infested with Fusarium oxysporum f. sp. melonis, Olpidium bornovanus, and Melon Necrotic Spot Virus (MNSV) in Colima, Mexico, where melons had only been grown previously using soil fumigation with MB. Yield and quality of melon cultivar Cruiser F1 (Harris Moran seed company) grafted on two rootstocks of Cucurbita maxima Duchesne × Cucurbita moschata Duchesne (“RS841”; Séminis seed company and “Shintosa Camelforce”; Nunhens seed company) were evaluated during two consecutive years. Each experiment had five treatments, two of which with non-grafted plants at a density of 18,519 plants/ha, with and without MB fumigation. The other three treatments consisted of grafted plants in non-fumigated soil with plant densities of 14,815, 11,111, and 9260 plants/ha. The use of melon grafted on “RS841” and “Shintosa Camelforce” rootstocks significantly increased the average fruit weight and the total yield of melons in soil without the need for MB. Grafting may be considered an alternative to MB fumigation. With the use of grafted melon plants, planting density may be reduced by 60%, obtaining higher yields than those obtained from non-grafted plants grown on fumigated land. Fruits harvested from grafted plants had equal firmness than those harvested from non-grafted plants, without affecting the content of soluble solids.     

亏缺灌溉对草莓生长和果实品质的影响

 采用负压控水系统将土壤水分控制在不同的水平上, 研究了亏缺灌溉对草莓果实特性、植株生长和产量形成的影响。随着土壤水分的降低, 植株的株高、叶片数、结果数、产量和单果质量逐步减少。不同土壤水分处理条件下果实的理化特性明显不同, 亏缺灌溉降低了果实含水量, 提高了果实硬度、可溶性固形物含量(Brix) 、滴定酸度、糖酸比、维生素C 含量。相关分析表明, 果实的鲜样质量、直径与土壤水分含量呈显著的正相关, 而可溶性固形物含量(Brix) 、糖酸比与土壤水分含量呈显著的负相关。     

Arbuscular mycorrhizal fungi communities improve the phytochemical quality of strawberry

The application of arbuscular mycorrhizal fungi (AMF) in strawberry cultivation can improve its growth and development. The objective of this study was to evaluate if strawberry plants in the absence and presence of inoculation with AMF communities, obtained from soils collected in reference-sites in the cultivation of this species, differ in their morpho-horticultural performance. Two experiments were carried out: in experiment I (frequency of AMF communities species) the treatments were eight soils containing AMF communities, collected from natural and agricultural ecosystems in reference-sites of strawberry cultivation in southern Brazil, with nine samples per treatment; in experiment II (use of AMF communities in strawberry) the treatments were eight AMF communities and one control (non-mycorrhizal plants), arranged in a completely randomised design, with three replicates. The species Claroideoglomus aff. luteum, C. claroideum, C. etunicatum, Funneliformis mosseae and Glomus sp2 were the most frequent in the studied sites and the morpho-horticultural performance of strawberry plants was improved when plants inoculated with AMF communities. Strawberry plants inoculated with mycorrhizae develop a more profuse root system and fruit anthocyanin content is increased.     

Investigations on Chlorosis of Fruit Trees.: III.—A Chlorosis of Plums Due to Potassium Deficiency.

Summary

Grafting is a suitable method to control soil-borne diseases in melon (Cucumis melo L.) crops. To date, several Cucurbita species and their inter-specific hybrids have been tested as rootstocks. However, graft-scion incompatibility and lower fruit quality have prevented their commercial use. The wild accession ‘Pat 81’ ssp. agrestis of C. melo is highly resistant to Monosporascus cannonballus Pollack et Uecker root rot, and develops a root system that is more suitable to withstand infested soils than that of cultivated melon. The potential of ‘Pat 81’ as a rootstock for melons (e.g., ‘Piel de Sapo’ type, C. melo ssp. melo) compared with the popular rootstock ‘RS 841’ (Cucurbita maxima Cucurbita moschata) has been evaluated here. The response of grafted plants to Monosporascus root rot disease, and rootstock effects on plant performance and fruit quality have been investigated using both classical methods and modern technologies (e.g., root image analysis and real-time PCR). The results indicate that, during infection, the root system of ‘Pat 81’ adapts to the needs of the aerial part of the ‘Piel de Sapo’ scion, displays a high level of resistance to M. cannonballus (similar to ‘RS 841’), and provides the plant with more healthy roots, with a higher root/vine biomass ratio compared with non-grafted ‘Piel de Sapo’. In addition, ‘Pat 81’ rootstock retains its favourable root structure (i.e., larger total length and root area) to withstand soil stress. In healthy soils, ‘Pat 81’ rootstocks had less effect on fruit quality than ‘RS 841’, leading to a lower percentage of non-marketable products. The high resistance of ‘Pat 81’, and its reduced effect on fruit quality, point to it as a good rootstock for the grafting of melons to resist M. Cannonballus infested soils.     

The Effect of a Substrate Containing Arbuscular Mycorrhizal Fungi and Rhizosphere Microorganisms (Trichoderma,Bacillus, Pseudomonas and Streptomyces) and Foliar Fertilization on Growth Response and Rhizosphere pH of Three Strawberry Cultivars

Abstract

Vegetatively propagated plants of three strawberry cultivars-‘Senga Sengana’, ‘Elsanta’ and ‘Kent’-were grown for 20 weeks in rhizoboxes filled with 1.85 kg of sterilized mineral soil. Ten plants were treated with an N-P-K foliar fertilizer (F, control), or inoculated with a substrate containing arbuscular mycorrhizal fungi, Trichoderma viride and rhizosphere bacteria (PGPR-Plant Growth Promoting Rhizobacteria) without any fertilization (M), or inoculated with the mixture of microorganisms and treated with the foliar fertilizer (MF). Total plant biomass was increased by the M treatment in all cultivars. M treatment resulted in higher total root length and number of root tips in ‘Senga Sengana’, whereas the other two cultivars showed different responses of root morphology. Shoot/root ratio was decreased by the M and MF treatments in comparison with control plants. Foliar fertilization of inoculated plants caused different growth responses in the three cultivars and a general decrease of root growth. After the MF treatment, the biomass of ‘Senga Sengana’ increased and the biomass of ‘Elsanta’ and ‘Kent’ decreased. Inoculation with the mycorrhiza-PGPR substrate increased rhizosphere pH irrespective of foliar fertilization. Plant mineral content was highly modified by the treatments in all the cultivars examined. In particular, changes were noted in N, P, K, Fe, B and Mn uptake. The results show an interaction between foliar fertilization and root inoculation with microorganisms, as well as genotype-dependent influences, on growth responses and rhizosphere pH of strawberry plants.     

Evaluation of Strawberry Genotypes for Chaetosiphon fragaefolii (Strawberry Aphid) Preference

ABSTRACT

Thirty-one strawberry genotypes were evaluated for supporting the reproductive success of the strawberry aphid (Chaetosiphon fragaefolii), a vector of several strawberry viruses. A pure colony of C. fragaefolii was initiated from eggs collected from field strawberry leaves in Fall 2013. In Spring 2014 greenhouse-grown strawberry plants with four to five leaves were placed in screened cages (16 genotypes/cage) and five aphids were placed on each plant. After 30–32 days, the number of aphids in each of four developmental stages was counted on each plant. Total aphid numbers/plant ranged from a mean of 33 on Fragaria chiloensis CFRA 48 (PI 551459) to 279 on F. × ananassa ‘AAC Lila’. Cultivars with relatively low numbers of aphids included ‘Bounty’ (106 aphids), ‘Mira’ (114 aphids), and ‘Annapolis’ (115 aphids). This experiment, part of a larger project on aphids and virus diseases associated with the cultivated strawberry, will inform decisions in the strawberry breeding program.     

A novel method for Citrus propagation: Seed grafting

Summary

We have developed a novel technique for grafting citrus seeds onto citrus rootstock plants that resulted in successful graft-take with normal vascular connections between the emerging seedling stem tissues and the rootstock plant. The method was found to be suitable for producing grafted plants from seeds of six cultivars and hybrids of Citrus and the citrus relative Murraya paniculata, using four common Citrus rootstocks. Plants produced by this method developed normally and were established in the field more rapidly than those produced by the common practice of grafting the rootstocks with budwood derived from seedlings prepared from seed in soil-based media. Seed grafting is expected to find a range of uses in breeding programmes; for example, by reducing the time required for the evaluation of hybrid seedlings, in cases where the female parent is mono-embryonic, for testing for vertical transmission of pathogens, and for screening for pathogen resistance among hybrid and mutagenised seed sources.     

Evaluation of Four Commercial Composts on Strawberry Plant Productivity and Soil Characteristics in California

ABSTRACT

Composts can have beneficial effects on strawberry production and these benefits can be dependent on the type of compost used. Four commercial composts were evaluated: cow manure, spent mushroom, yard trimmings, and vermicompost. The nutrient composition, abundance of fungi and bacteria, and microbial activity were determined. Five field trials assessed effects on plant growth, root development, soil microbial activity, nutrient availability, and yield during one growing season. Manure and mushroom compost significantly increased soil electrical conductivity levels to 9.9 ± 1.7 dS/m and 7.3 ± 0.8 dS/m, respectively. Manure, yard trimmings, and mushroom composts shifted soil pH toward optimal levels for up to 7 months. Mushroom compost had the greatest effect on soil nitrate, which was up to 32 mg/kg of soil higher than non-amended soil. Significant effects on yield were more likely to occur where environmental conditions and management practices were less than optimal or compost was not routinely added. Several factors important to plant production were significantly affected by compost: soil salinity, plant establishment, soil nitrate, production curves, soil microbial activity, and soil pH.     

The response of onions to solar heating,agricultural practices and pink-root disease

Solar heating (solarisation) of the soil, by means of mulching with transparent polyethylene sheets in the hot season, is used for disease control. The effect of soil solarisation, under different agricultural practices, on incidence of pink-root disease caused by Pyrenochaeta terrestris, and on onion yield and quality was investigated. Onions were seeded in beds of non-infested, either non-solarised or solarised, soil and transplanted into growth containers filled with soil either non-infested or infested with the pink-root pathogen. Growth of plants pre-grown in solarised beds was improved as compared to plants originated from non-infested beds. Plants grown in the infested soil suffered considerably, as expressed in leaf number and length, root quantity and bulbing-process. In a field experiment, early sowing resulted in a higher disease incidence than later sowing. Soil solarisation controlled the disease, improved seedling survival and increased yield in most cases. Delay in harvest to 100% falling tops increased yields and reduced percentage of undersized bulbs. At high plant-population density (170 plants m^?2), percentage of small bulbs was higher and rates of double bulbs were lower than at low plant density (90 plants m^?2). Soil solarisation resulted in effective disease control and higher yields and facilitated accurate planning of plant population in the field, extension of the growing-season and higher yields of better quality.     

Efficacy of Insecticides against Lygus hesperus Knight (Hemiptera: Miridae) in the California’s Central Coast Strawberry

ABSTRACT

The western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae), is an important insect pest of strawberry (Fragaria ananassa Duchesne) in the Central Coast of California. Because little is known about efficacy of new insecticides, especially sulfoxaflor and flupyradifurone, against L. hesperus, two replicated insecticide experiments were conducted in 2014 and 2015 in commercial strawberry fields naturally infested with L. hesperus. The insecticides, sulfoxaflor, flupyradifurone, flonicamid, thiamethoxam fenpropathrin, essential oils (rosemary and peppermint oils), and mineral oil, were compared with untreated check. Higher and lower rates of flupyradifurone and sulfoxaflor were tested. Higher rates of sulfoxaflor and flupyradifurone were effective in suppressing L. hesperus. The industry standard, thiamethoxam + fenpropathrin, was effective in 2014 but not in the 2015 experiment. Flonicamid provided a moderate level of efficacy against L. hesperus in both years. The number of predacious bugs was significantly lower in the higher rate of flupyradifurone than in other treatments, although the number of spiders was not significantly different among treatments.     

Soil seed banks are short-lived and triggered by the first effective rainfalls in the vacant lots of Santiago,Chile

We studied the temporal variation of the soil seed banks in the urban lots of Santiago, Chile. As most of the plants that emerge from the seed banks in lots are also found in open habitats and are easily germinable, we hypothesize that the seed banks in lots are highly dynamic and short-lived, with the bank depleted every year during the germination season to be reloaded with new seeds during the next seed dispersal period. In each 20 lots for two year (2017 and 2018), 9 soil samples were collected. These samples were obtained from three sampling points randomly distributed across the plots. The seed bank was estimated by seed germination in soil samples placed in plastic trays. The samples of all the lots were stratified at 2 °C by 3 months before sowing. In order to record the seed persistence, soil of three lots watered in 2017 for six months were dried and maintained under dark and non-watered conditions until re-sowing in autumn 2018. To determine if the seeds present cold-associated germination triggers, soils of five lots were maintained under dark conditions for 3 months (soils without cold stratification) for comparison with soils with cold stratification of the same lots. The above-ground plants were recorded in all lots for both years. Forty plant species were recorded in soil bank. The total emerged seedling densities ranged between 7,944 (2017) to 3,700 seedlings m^-2 (2018). Species per lot varied between 17 and 7 during 2017, and between 14 and 3 during 2018. In five lots, seedling densities were not statistically different between cold stratified soil at 2 ° C and non-stratified. In three lots with re-sown soil, seedling density of the first sowing (4,096 seedlings m^-2) was significantly higher than second sowing (201 seedlings m^-2). Thirty-seven plant species were recorded in the above-ground vegetation during 2017 and 42 species in 2018. Species frequency of the seed bank was positively correlated with species frequency of above-ground vegetation. Concluding, the bank is highly dynamic, short-lived, and is depleted every year during the germination season, which begins with effective rainfalls, would be reloaded with seeds during the seed dispersal period.     

The Influence of Vigour and Nitrogen Status on the Fruitfulness of Talisman Strawberry Plants

In a study on the growth and cropping of strawberries under contrasting soil nitrogen conditions in a trial extending over six years, annual split applications of Nitrochalk maintained distinct regimes of mineral nitrogen in the soil but 30 tons/acre F.Y.M., prior to planting, had little additional effect. Nitrogen deficiency was achieved by preplanting applications of straw but this only lasted for one season.

There was a regular pattern in leaf nitrogen concentration associated with the different phases of strawberry growth. The concentration showed a linear response to increments of fertilizer nitrogen. Leaf colour gave visual evidence of these differences.

F.Y.M. did not affect plant growth or cropping but nitrogen applications resulted in small increases in both plant spread and number of crowns per plant.

Nitrogen at 200 lb. N/acre depressed the yields of marketable fruit in each of the four years. This was due only in part to an increase in wastage and it is suggested that a high nitrogen status in the plant could reduce the number of fruits per truss. The lower rate (50 lb. N/acre) gave yields generally similar to the nil control.

Nitrogen levels had little influence on the intensity of flowering in spring, whereas autumn flowering decreased sharply as nitrogen levels increased. Floral initiation thus appears much more sensitive to the nitrogen status of the plant in July than in September.     

土壤微生物-抑病性与土壤健康

土壤微生物对维持土壤系统稳定性和受损土壤系统的恢复有重要作用,与土壤系统健康紧密相关。现代农业种植体系中由于施肥、管理措施不合理,降低了土壤微生物多样性,破坏了土壤微生物群落结构和功能, 导致土传病害爆发。改进农业土壤管理能提高土壤微生物群落多样性和功能,是控制土传病害发生的一条有效途径。本文对土壤微生物与土壤系统健康的关系、土壤微生物的抑病性以及健康土壤管理等问题进行概述,指出未来健康的土壤农业生产体系将从以植物为主体的常规管理体系向以植物和微生物为主体的综合管理体系发展。     

花椒籽饼熏蒸对番茄根结线虫的防效及作用机理

采用温室盆栽试验、GC-MS分析方法以及根结线虫二龄幼虫离体触杀试验,研究了花椒籽饼对番茄根结线虫的防治效果及其作用机理。结果表明:土壤生物熏蒸处理30d后,随花椒籽饼施用量的增加,土壤中全氮、全磷、全钾、碱解氮、速效钾含量均显著增加,土壤p H值呈上升趋势,速效磷含量则下降;番茄定植30d后,随花椒籽饼施用量的增加,植株根结指数逐渐下降,株高、茎粗则呈现先增加后降低的趋势;不同浓度的花椒籽饼浸提液均对根结线虫虫卵孵化产生抑制作用,且随浸提液浓度的增加抑制作用增强;GC-MS分析结果表明,花椒籽饼中含有28种挥发性物质,其中具有杀线作用的D-柠檬烯和芳樟醇两种物质之和占总成分的13.53%;不同浓度的D-柠檬烯和芳樟醇均能够有效抑制根结线虫二龄幼虫的活性,且表现出明显的浓度效应。综上,适量施用花椒籽饼不仅能够改善土壤理化性质,促进番茄植株生长,而且能够有效地抑制根结线虫的发生,其杀线机理主要归因于花椒籽饼中含有丰富的D-柠檬烯和芳樟醇。