Integration of partial resistance,plant density and use of fungicide for management of white mould in common bean

In-row plant densities have not been studied for common beans with type II growth habit and contrasting reactions to white mould. Advanced breeding lines with partial resistance or susceptibility to white mould were combined with 4, 7, 10 or 13 plants m⁻¹ and with or without fungicide at a constant between-row spacing of 0.5 m in five sprinkler-irrigated field trials conducted during the autumn–winter season in Brazil. White mould pressures in the trials covered the whole range from zero to moderate/high (46–60% of white mould severity index). In all trials, means of white mould incidence, severity and yield did not vary significantly between 7 and 13 plants m⁻¹ for the partially resistant line, regardless of the fungicide levels. For the susceptible line, 13 plants m⁻¹ increased white mould incidence and severity under moderate disease, regardless of the fungicide levels, and decreased yield compared with 10 plants m⁻¹ when fungicide was applied twice under moderate/high disease pressure. For the susceptible line, 7 or 10 plants m⁻¹ maximized yield in all trials, with or without fungicide applications. The results suggest that the current recommendation of 11–13 plants m⁻¹ could be used for type II beans with partial resistance to white mould in either a conventional or organic system. For susceptible genotypes, 7–10 plants m⁻¹ seems to be the most appropriate in-row plant density. This study may improve the recommendation of in-row plant density for type II beans cultivated under white mould pressure.     

Effects of sowing date on severity of blight caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> and yield components of five chickpea cultivars grown under two climatic conditions in Tunisia

Five chickpea cultivars, Chitoui, Neyer, Kasseb, Beja 1 and Bouchra, were planted on three sowing dates at two Experimental Stations in Tunisia: Bou Salem in the north and the more southerly Mornag, where the climate is drier. Severity of blight, caused by Ascochyta rabiei, was measured on a 1–9 scale (defined) on vegetative parts and on pods as percent infected and percent infected that were empty. At both locations, disease was essentially absent on plants sown on the third dates but present on plants sown on the two earlier dates. At Bou Salem, disease severity was highest for the second sowing date whereas at Mornag it was highest for the first sowing date; but for each sowing date, disease severity was lower at Mornag than at Bou Salem. Yield components were measured as number of pods per plant, number of seeds per plant, number of seeds per 100 pods, 100 seed weight and weight of seeds per plant. Both disease severity and yield differed significantly among sowing dates (differently at each location) and also among cultivars for each sowing date, these differences depending both on sowing date and location. A lower yield was always associated with a higher disease severity, although the quantitative relationship differed between cultivars and locations. Cultivar Beja 1 had the lowest vegetative disease scores at both locations and both sowing dates 1 and 2. Beja 1 also scored well for all yield components. Plants sown on the third (latest) date gave the highest yields for all cultivars at both locations (except for an unusually high yield of Neyer at Mornag on sowing date 2), in some instances being more than double those from the earlier sowing dates. Thus, in contrast to other studies, late sowing did not result in yield loss.     

Angular leaf spot of phaseolus beans: relationships between disease, healthy leaf area, and yield

ABSTRACT Five field experiments were conducted to investigate the relationship between the severity of visible disease (X), area under the disease progress curve (AUDPC), healthy leaf area index on any given day (HLAI), radiation intercepted by healthy leaf area on any given day (HRI), healthy leaf area duration (HAD), total healthy leaf area absorption (HAA), and yield of Phaseolus beans, cultivars Rosinha and Carioca, inoculated with Phaeoisariopsis griseola at several doses. In general, yield was not related to disease severity (X) or AUDPC. In contrast, the highest yields were always related to the highest values of HAD and HAA. The relationship between yield and HAD was linear in each of five trials (29.9 < R(2) < 70.2%, P < 0.001). The relationship between yield and HAA was linear in four of the trials (52.3 < R(2) < 70.3%, P < 0.001) and exponential in one of them (in which the plant canopy was the largest). Singlepoint models using HRI to estimate yield at various times during the crop season were developed. The slope of the yield-HRI relationship proved to be stable (26.8 +/-2.4 g MJ(-1)), regardless of cultivar, locale, planting date, and bean growth stage (from R5 to R8). The yield-HLAI relationship proved to be less consistent. HRI is proposed as a key explanatory variable for a transportable system of disease management; it may be useful in producing precise recommendations at the farm level.     

Determination of agronomic practices for the management of blight of chickpea caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> in Turkey: 1. Appropriate sowing date

In order to determine the most appropriate dates for planting chickpea in central Anatolia, Turkey, six cultivars were planted at three sites that differed in disease pressure. In two of the sites, disease pressure from Ascochyta rabiei was promoted by spreading infected chickpea debris on the soil surface at the time of planting and, at one of these, sprinkle irrigation was applied. In the third site, where conditions were dryer, no artificial inoculum was provided. Plants from seeds sown in early March had the most disease and in the sprinkle irrigated plots the disease severity ranged from 7.8 on the most susceptible cv. Canitez to 3.3 on the least susceptible Gokce as scored on the 1–9 scale where 1 = no disease and 9 represents a plant killed by the fungus. There was an inverse relationship between disease severity and yield, production from blight resistant cultivars of around 2,000 kg ha⁻¹ being more than twice that of susceptible ones. Delaying planting for 3–5 weeks reduced the severity of ascochyta blight but also reduced the yields in four of the six cultivars. In contrast, reduction in disease severity by delayed sowing resulted in yield increases for the susceptible cvs Canitez and Local, although yield level was not as much as those of the less susceptible cvs sown early. Delay of 6–9 weeks almost eliminated ascochyta blight but yields of all cultivars were seriously compromised by drought stress. In consequence, chickpea farmers are recommended to use resistant or tolerant cultivars and sow early in March. For less resistant cultivars, sowing in early April is recommended. Further delay is not recommended unless irrigation is provided and fungicide spraying is recommended where signs of infection are present under conditions conducive to the disease.     

基于连续14年国家绿豆品种区域试验的中国绿豆品种产量和性状变化

利用GGE双标图、变异系数法、相关性分析、多元回归和聚类分析等方法,分析了2003—2016年共14 a国家绿豆品种区域试验中来自内蒙古自治区、黑龙江省、吉林省、辽宁省、山西省等12个绿豆主产省（市、自治区）的29个育种单位提供的130个参试品种的生育天数、株高、主茎节数、主茎分枝数、荚长、单株荚数、荚粒数、千粒重以及产量在春播组和夏播组的变异,并比较了性状间的相关性以及不同育种单位选育的绿豆品种的性状差异。结果表明：2003—2016年春播组和夏播组绿豆产量分别增加14.0%和25.4%,年均增幅分别为1.0%和1.8%;主茎分支数分别减少12.0%和15.9%;其他性状变化不明显。春播组绿豆主要农艺性状的变异系数为5.14%~17.01%,均值为11.33%;遗传多样性指数为1.91~2.08,平均为1.99。夏播组绿豆主要农艺性状的变异系数为5.96%~19.99%,均值为12.52%;遗传多样性指数为1.98~2.17,平均为2.07。相关性和偏相关性分析表明,春播组中产量与荚长、单株荚数和荚粒数显著正相关,与其他性状的相关性不明显;夏播组中产量与单株荚数和荚粒数显著正相关,与株高、主茎分支数和荚长显著负相关。多元回归分析表明,春播组绿豆生育天数、株高、主茎分支数、荚长和单株荚数共同决定产量60.9%的变异;夏播组绿豆株高、主茎分枝数、单株荚数、荚粒数和千粒重共同决定产量87.7%的变异。依托品种选育区域的聚类分析表明,65个春播组品种被分为4类,在北京市、河北省、山西省、河南省、山东省、吉林省和陕西省综合表现较好;65个夏播组品种被分为6类,在河南省、河北省和山东省综合表现较好。2003—2016年,国家每轮区试的绿豆品种产量稳步提升,表明我国绿豆育种水平有了一定提升;但品种遗传基础狭窄,育种方法多样化程度较低,缺少突破性品种。     

Effects of soil moisture and sowing depth on the development of bean plants grown in sterile soil infested by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> and <Emphasis Type="Italic">Trichoderma harzianum</Emphasis>

The effects of soil moisture (varying from 15% to 42% (v/v)) and sowing depth (1.5–6.0 cm) on the development of bean plants grown in sterile soil infested by the pathogen Rhizoctonia solani and its antagonist Trichoderma harzianum were studied under greenhouse conditions. The four possible combinations of soil infestation with both fungi were tested. Disease severity, percentage of plants emerged, plant height and dry weight were evaluated 3 weeks after sowing. Emergence rate and growth of plants inoculated only with R. solani were not affected by soil moisture, but in the presence of both fungi, plant emergence, plant height and dry weight significantly decreased when soil moisture diminished. Deep sowing significantly reduced the emergence rate and growth of those plants that were inoculated with R. solani only. However, when the soil was infested with both fungi, the effect of sowing depth was not significant. At a sowing depth of 6.0 cm, the percentage of plants emerged was 50% in the presence of T. harzianum, but only 6.7% when the pathogen was inoculated alone. The antagonist protected bean seedlings from pre-emergence damping-off, reduced disease severity and increased plant growth in the presence of R. solani, especially in moist soil.     

Silicon and increased electrical conductivity reduce downy mildew of soilless grown lettuce

Downy mildew of lettuce, caused by Bremia lactucae, is difficult to control in soilless systems by using conventional methods of disease management because few chemicals are registered, while resistant cultivars face the problem of resistance break down; therefore other methods for disease control need to be investigated. The effect of silicon salt as well as increased electrical conductivities against downy mildew was evaluated in four experiments carried out in hydroponically systems, using the cultivar of lettuce “Cobham Green”, known for its susceptibility to the pathogen. Silicon, as potassium silicate, was added at 100 mg l⁻¹ of nutrient solution at three levels of electrical conductivity: 1.5–1.6 mS cm⁻¹ (EC1), 3.0–3.5 mScm⁻¹ (EC2, 0.70 g l⁻¹ NaCl) and 4.0–4.5 mS cm⁻¹ (EC3, 0.95 g l⁻¹ NaCl) respectively. Lettuce plants, grown for 14–20 (trials 1 and 2) and 36–45 (trials 3 and 4) days in the different nutrient solutions tested, were inoculated with B. lactucae conidia with a maximum of two inoculations before final disease assessment carried out 14–21 days after the inoculation able to give symptoms. EC and potassium silicate significantly influenced downy mildew incidence and severity, while their interaction was not a significant factor. The addition to the standard nutrient solution (EC1) of potassium silicate resulted in a significant reduction of downy mildew severity in trials 1 and 2 where plants were artificially inoculated 15 and 20 days after transplanting. This efficacy was slight on plants grown for 36 and 45 days before inoculation in a soil drenched with EC1 amended with potassium silicate. EC2 gave a significantly similar downy mildew reduction than EC2 added with potassium silicate in trial 3. Plants grown for 36 and 45 days at the highest electrical conductivity (EC3) showed a significant reduction in severity of downy mildew compared with that observed at EC2 level. The best results, in terms of disease control, were given by the addition of potassium silicate to the EC3 solution. This combination also led to a significantly increased plant biomass. The possibility and benefits of applying potassium silicate and increased EC amendments in practice is discussed.     

Ratio of rice reflectance for estimating leaf blast severity with a multispectral radiometer

 Rice reflectance was measured to determine the spectral regions most sensitive to leaf blast infection with a multispectral radiometer. As disease severity increased, reflectance also increased in the 400–500 nm (blue), 570–700 nm (red), and 900–2000 nm regions but decreased in the 500–570 nm and 700–900 nm regions. The increased reflectance in the blue and red regions may be attributed to decreased chlorophyll and carotenoid contents in response to the blast infection. The maximum and minimum reflectance differences occurred at 680 nm and 760 nm for the nondiseased and diseased rice, respectively. The spectral location of maximum sensitivity was 675 nm regardless of disease severity. Rice reflectance ratios were evaluated as indicators of leaf blast severity. Two ratios, R550/R675 (reflectance at 550 nm divided by reflectance at 675 nm), and R570/R675 quantified the significant disease severity. These wavelengths were selected based on the sensitivity minima and maxima. The ratios of nondiseased rice plants varied depending on growth stage. The variation in ratios must be considered when they are used to estimate leaf blast severity. Received: April 2, 2002 / Accepted: August 12, 2002     

Effects of Thiobacillus and Different Levels of Sulfur Fertilizer on Growth and Physiological Indices in Intercropping of Sesame (Sesamum Indicum L.) and Mung Bean (Vigna Radiata L.)

The two-location field experiment was conducted to investigate the effect of Thiobacillus and different levels of sulfur fertilizer on growth and physiological indices in the replacement intercropping of sesame and mung bean. A factorial experiment was performed based on a randomized complete block design in 3 replications in 2018. The experimental factors consisted of cropping ratio at five levels: 1. sesame sole cropping, 2. mung bean sole cropping, 3. 75% sesame +25% mung bean (3:1), 4. 50% sesame +50% mung bean (1:1), 5. 25% sesame +75% mung bean (1:3). Sulfur fertilizer was used at three levels: control level (S₀), 50% of recommended amount (S₁), 100% of recommended amount (S₂). Thiobacillus bacteria was used at two levels: T₀ and T₁. The results showed that growth indices chlorophyll a, chlorophyll b, total chlorophyll, biological yield, and grain yield of sesame and mung bean were significantly affected by the studied treatments. The highest growth indices, chlorophyll a, chlorophyll b, total chlorophyll, biological yield and grain yield of sesame were obtained by the 3:1 ratio. For the mung bean, the highest growth indices, chlorophyll a, biological yield, grain yield were obtained by mung bean sole cropping and the highest chlorophyll b and total chlorophyll were obtained by the 1:1 ratio. Also, sulfur fertilizer, 100% of the recommended amount, increased all studied indices in both plants except for chlorophyll a in sesame. Interaction effects of cropping ratio and location on growth indices, grain biological yield, chlorophyll a of sesame and mung bean were significant.

     

Mitigation of vanillic acid-promoted faba bean Fusarium wilt by faba bean–wheat intercropping

Long-term continuous monocropping of faba beans increases the incidence of faba bean wilt, while faba bean–wheat intercropping can effectively control it. This study aimed to understand the underlying mechanism of faba bean–wheat intercropping for the control of Fusarium oxysporum and vanillic acid (VA)-promoted occurrence of faba bean wilt. The occurrence of faba bean wilt was investigated among the monocropped and intercropped plants of faba beans in a field experiment. The contents and types of phenolic acids were examined in the rhizosphere soil. Monocropped and intercropped faba beans were examined under the dual stress of F. oxysporum and different concentrations of VA (0, 50, 100, 200 mg/L) to understand the alleviating mechanism of faba bean–wheat intercropping. Exogenous addition of high concentrations of VA significantly inhibited the growth and reproduction of F. oxysporum, but under the dual stress of F. oxysporum and different concentrations of VA, it significantly inhibited the defence enzymes of faba bean roots, stems, and leaves, and rhizosphere soil enzymes. Interestingly, faba bean–wheat intercropping alleviated VA stress and thereby the incidence and disease index of faba bean Fusarium wilt by improving plant resistance and soil enzyme activity. The dual stress of F. oxysporum and VA promotes the occurrence of Fusarium wilt by damaging the defence system of the faba bean root system and rhizosphere soil environment. However, faba bean–wheat intercropping effectively alleviates the autotoxicity of VA by improving the physiological and biochemical resistance of faba beans and soil enzyme activities, and thus controls the occurrence of Fusarium wilt.     

An Ulva armoricana extract protects plants against three powdery mildew pathogens

The protective activity of a crude extract prepared from the green macroalga, Ulva armoricana, previously shown to induce plant defence responses, was evaluated on three plant species, common bean, grapevine and cucumber, cultivated in the greenhouse and inoculated with three powdery mildew pathogens Erysiphe polygoni, E. necator and Sphareotheca fuliginea respectively. Chemical analyses showed that the extract was enriched in ulvans, which are green algae polysaccharides essentially composed of uronic acid and sulphated rhamnose. Weekly applications were performed by spraying of the green algal extract at various dilutions on bean, grapevine and cucumber leaves. A significant effect (50% protection) was observed using a dilution corresponding to about 3 g l⁻¹ dry matter and up to 90% reduction of symptom severity was obtained for the highest concentration (1/9 dilution, 6 g l⁻¹ dry matter) for the three plant species. To study the natural variability of the protective activity, five extracts prepared from algae batches harvested at different year periods were evaluated. Although polysaccharide composition varied among batches, all extracts elicit a reporter gene regulated by a defence-gene promoter in a transgenic tobacco line, and protect cucumber plants against powdery mildew infection. Together, these data demonstrate that U. armoricana is a reproducible source of active compounds which can be used to efficiently protect crop plants against powdery mildew diseases.     

Sorghum (Sorghum bicolor) as a bean intercrop or rotation crop contributes to the survival of bean root rot pathogens and perpetuation of bean root rots

Root rots (RR) are the main cause of declining bean (Phaseolus vulgaris) production in southwestern Uganda. Here, beans are mainly intercropped/rotated with maize (Zea mays), sorghum (Sorghum bicolor), sweet potato (Ipomoea batatas), potatoes (Solanum tuberosum) and garden peas (Pisum sativum). These crops also suffer from RR and bean RR pathogens have been isolated from some of these crops. This study aimed to determine the extent of RR on maize, sorghum and peas, and their potential to contribute to the survival of bean RR pathogens. Therefore, experiments were carried out in bean RR‐infested farmers’ fields as well as soils inoculated with bean RR pathogens (Pythium spp. and Fusarium spp.) under screen house conditions and a susceptible bean cultivar served as a control. High RR incidence/severity scores were recorded in beans and sorghum in both farmers’ fields and screen house experiments. The high field RR incidence/severity in sorghum correlated with the screen house scores. This study shows that RR is also a problem to other crops, especially sorghum, warranting attention. The findings also imply that sorghum plays a potential role as an alternate host to bean RR pathogens, increasing inoculum density of bean RR pathogens and potentially negatively impacting the bean RR problem. Intercropping or rotating beans with sorghum in this region is not recommended. However, maize was RR‐resistant and therefore appropriate as an intercrop/rotational crop to beans in the system. A holistic rather than commodity approach is recommended for managing RR in this cropping system.     

Plant defense activation and management of tomato root rot by a chitin-fortified <Emphasis Type="Italic">Trichoderma/Hypocrea</Emphasis> formulation

Tomato root rot caused by Rhizoctonia solani is a major soilborne disease resulting in significant yield loss. The culture filtrates of six isolates of Trichoderma/Hypocrea species were evaluated for in vitro production of hydrolytic enzymes. Results demonstrated that all the six isolates were able to produce chitinase, β-1, 3 glucanase and protease in the range of 76–235 μmol GlcNAc min^-1 mg^-1 protein, 31.90–37.72 nmol glucose min^-1 mg^-1 proteins and 63.05–86.22 μmol min^-1 mg^-1 proteins, respectively. Trichoderma/Hypocrea-based formulation(s) were prepared with chitin (1% v:v) and CMC (0.5% w:v) for root rot management in a greenhouse. Root dip application with bioformulation(s) resulted in a significant reduction of the root rot index. In addition, bioformulations increased plant growth attributing traits significantly relative to untreated control. Accumulation of total phenols, peroxidase, polyphenoloxidase and phenylalanine ammonia lyase increased in chitin-supplemented Trichoderma/Hypocrea formulation-treated plants challenged with R. solani. The results suggest that chitin-fortified bioformulation(s) could be an effective system to control root rot of tomato in an eco-compatible manner.     

Response of pinto and small red Mexican beans (Phaseolus vulgaris L.) to preplant-incorporated herbicides

Four field trials were conducted over a 2 year period at Exeter (2005, 2006), Harrow (2006), and Ridgetown (2006), Ontario, Canada, to evaluate the tolerance of pinto and small red Mexican (SRM) beans to the preplant-incorporated (PPI) application of trifluralin, dimethenamid, S -metolachlor, KIH-485, imazethapyr, and flumetsulam. All the treatments, including the untreated control, were maintained weed-free during the growing season. The PPI application of trifluralin, dimethenamid, and S -metolachlor resulted in minimal transient visual injury, with no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of the pinto and SRM beans. The PPI application of imazethapyr and flumetsulam, especially at the high rate, initially caused 13% injury and reduced the plant height and shoot dry weight by 15 and 28%, respectively, but these injuries were transient and had no effect on the seed maturity and yield of the pinto and SRM beans. The PPI application of KIH-485 caused 80% injury to the pinto and SRM beans and reduced the plant height, shoot dry weight, and yield. The dry bean maturity was also delayed. Based on these results, trifluralin, dimethenamid, S -metolachlor, imazethapyr, and flumetsulam, applied as PPI herbicides, have the potential to be used in a weed management program for pinto and SRM beans. However, KIH-485, applied as a PPI herbicide at the doses evaluated, does not have an adequate margin of crop safety for use in pinto and SRM bean production in Ontario.     

Epiphytic Curtobacterium flaccumfaciens strains isolated from symptomless solanaceous vegetables are pathogenic on leguminous but not on solanaceous plants

In Iran, during 2013–16, 16 Gram‐positive corynebacteria‐like strains were recovered from the epiphytic parts of solanaceous vegetables including eggplant, pepper and tomato. The strains were recovered accidentally as a result of monitoring for other bacterial pathogens in solanaceous fields. The strains were phenotypically different from Clavibacter michiganensis strains. Although none of the strains were pathogenic on their host of isolation or on any other solanaceous plants, 12 out of 16 strains were pathogenic on common bean, cowpea, mung bean and soybean. Colonization by strains was observed on maize, zucchini, faba bean, honeydew melon, rapeseed, sugar beet and sunflower plants under greenhouse conditions. In PCR tests, the primer pair CffFOR2/CffREV4, specific for Curtobacterium flaccumfaciens pv. flaccumfaciens, enabled the amplification of the appropriately sized fragment in 12 out of 16 strains, and all 12 strains were pathogenic on dry beans. Phylogenetic analysis, using the gyrB and recA genes, showed all 16 bacterial strains clustered within several pathovars of C. flaccumfaciens. A nonpathogenic yellow‐pigmented strain (Xeu15) was clustered with the type strains of C. flaccumfaciens pv. betae and C. flaccumfaciens pv. oortii. Bacteriocin profiling assays revealed no significant differences among the pathogenic and nonpathogenic strains. Host range and population dynamics of four representative strains on 17 plant species showed population build‐up of the strains only on common bean, cowpea, wheat and red nightshade plants. The results provide important insights into the possible role of nonhost plants as reservoirs of plant pathogenic bacteria, which has important implications in plant disease epidemiology and management.     

Identification of sugar beet germplasm EL51 as a source of resistance to post-emergence Rhizoctonia damping-off

Resistance of sugar beet seedlings to Rhizoctonia damping-off caused by Rhizoctonia solani has not been described. A series of preliminary characterisations using a single susceptible host and four different R. solani isolates suggested the disease progression pattern was predictable. Two AG-4 isolates and a less virulent AG-2-2 isolate (W22) showed a comparable pattern of disease progression in the growth chamber where disease index values increased for the first 5–6 days, were relatively constant for the next 7–8 days, and declined thereafter. Seedlings inoculated with a highly virulent AG-2-2 isolate (R-1) under the same conditions showed similar patterns for the first 4 days post-inoculation; however disease index values continued to increase until seedling death at 13–14 days. Similar results were observed in the greenhouse, and a small expanded set of other germplasm lines were screened. One tested germplasm accession, EL51, survived seedling inoculation with R. solani AG-2-2 R-1, and its disease progress pattern was characterised. In a field seedling disease nursery artificially inoculated with R. solani AG-2-2 R-1, seedling persistence was high with EL51, but not with a susceptible hybrid. Identification of EL51 as a source of resistance to Rhizoctonia damping-off may allow investigations into the Beta vulgaris–Rhizoctonia solani pathosystem and add value in sugar beet breeding.     

Control of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> at a strawberry nursery by paddy-upland rotation

Effects of crop rotation between rice paddy fields and strawberry nurseries on the control of Verticillium wilt of strawberry were studied. For detecting Verticillium dahliae, the causal agent of Verticillium wilt, in soil, eggplant was used as an indicator plant. We were thus able to detect as low as 1 microsclerotium/g dry soil. In field surveys of Chiba and Hokkaido from 2000 to 2003, V. dahliae was detected in 9 of 10 upland fields but in none of 21 paddy-upland fields. In Hokkaido during 2000–2007, strawberry mother plants were planted, and plantlets were produced in upland and paddy-upland fields to assess V. dahliae infestation. Verticillium wilt of strawberry had never occurred in 72 tested paddy-upland fields, compared to 13.2–73.9% of plantlets infected with V. dahliae in upland fields. In a pot experiment in a greenhouse, two flooding treatments or two paddy rice cultivations suppressed Verticillium wilt symptoms on eggplant. In field experiments, one paddy rice cultivation in Chiba and two in Hokkaido prevented development of Verticillium wilt symptoms on eggplant. Verticillium wilt of strawberry was controlled completely with one paddy rice cultivation in infested fields in Chiba. In these field experiments, the number of microsclerotia of V. dahliae decreased under the flooding conditions for paddy rice cultivation. Based on the reduction in microsclerotia, a crop rotation system with paddy rice for 3 years (three times), green manure for 1 year, and strawberry nursery for 1 year was designed for Hokkaido.     

Evaluation of fungicide application rates,spray schedules and alternative management options for rust and angular leaf spot of snap beans in Uganda

Yield losses due to rust and angular leaf spot (ALS) of snap beans may reach 100% in Eastern Africa. Where susceptible varieties are grown, farmers control these diseases with routine fungicide applications. To determine an optimum application rate and spray schedule for Orius® (tebuconazole 250 g/L), we sprayed 10 mL and 20 mL Orius® per 15 L spray water twice at two trifoliate leaf stage and 50% flowering, and three times at the same stages, with an additional application at pod initiation. In farmers’ fields, we tested the effect of fungicide sprays, use of resistant variety, intercropping, increased plant spacing and farmyard manure on rust and ALS diseases. Application three times of 20 mL Orius® per 15 L spray water reduced rust severity scores by 5.7 and 2.4 in 2010 and 2011, respectively. Lowest rust and ALS severities were observed when a resistant variety, fungicide or farmyard manure was used. Pod yield increments due to disease management ranged between 13% and 242%. Prophylactic fungicide application, use of resistant varieties and farmyard manure can be used to reduce disease severity and improve snap bean quality on smallholder farms.     

Temporal Progression of Bean Common Bacterial Blight (Xanthomonas Campestris pv. phaseoli) in Sole and Intercropping Systems

The effects of four planting patterns of bean (Phaseolus vulgaris) (bean only, maize–bean (MB), sorghum–bean (SB), and maize–bean–sorghum (MBS)) and four cropping systems (sole cropping, row, mixed, and broadcast intercropping) on the temporal epidemics of bean common bacterial blight (CBB) caused by Xanthomonas campestris pv. phaseoli were studied. The experiments were conducted during two consecutive spring and summer seasons in 1999 and 2000 in replicated field experiments. The Gompertz model described disease progress curves better than the logistic model. Intercropping delayed epidemic onset, lowered disease incidence and severity, and reduced the disease progress rate. The type of cropping system and planting pattern affected CBB incidence and severity at initial, final and overall assessments and also affected the rate of disease development. Statistical significance of treatment interactions based on disease assessments was found for incidence in all four experiments and for severity in three experiments. A slower disease progress rate and lower incidence and severity occurred on beans planted with maize or sorghum in row, mixed and broadcast intercropping than on bean planted alone. Incidence was reduced 36% and severity 20% in intercropping compared to sole cropping. The built-in disease delay and the slowing of the disease progress rate could provide protection for beans from severe CBB epidemics in intercropped systems. Variation between years appeared to be related to relative humidity (RH).     

Identification of factors associated with white mould in snap bean using tree-based methods

Most processing snap bean fields are treated with fungicides at flowering to suppress white mould, one of the more significant diseases of this crop. Farmers would like to know when their fields are at sufficient risk of white mould, to plan fungicide applications or avoid spraying if the risk is below a tolerable threshold. In 2006, 2007 and 2008, observational data were collected from processing snap bean fields across western and central New York State, USA. White mould was found in 20% of fields. Boosted regression trees were used to model white mould presence or absence in a field (a binary response variable) as a function of agronomic and edaphic variables, and macroscale drought indices. The five most important predictors were canopy openness during pod development, the number of days after planting, hydrologic soil group, canopy openness during bloom and elevation. The risk of white mould increased by about 20% when canopy openness was less than 20 cm at the bloom stage and c. 30% when canopy openness was less than 30 cm at the pod stage. The most relevant interaction was between canopy openness at the pod stage and hydrologic soil group. A random forest model for predicting the presence of white mould by bloom had an estimated classification accuracy of 73%. The extension of these results to remote forecasting of white mould in processing snap bean production is discussed.