Timing of susceptibility of highbush blueberry cultivars in northwestern Washington to Monilinia vaccinii‐corymbosi,the cause of mummy berry

Mummy berry, caused by Monilinia vaccinii‐corymbosi, causes significant yield losses in blueberry fields in the coastal region of the Pacific Northwest, including northwestern Washington (WA). Development of effective disease control strategies are hindered by lack of knowledge of disease epidemiology in this region. This study compared floral and vegetative bud development of four blueberry cultivars, Duke, Bluecrop, Liberty and Draper, by evaluating the timing and number of susceptible buds on plants during the ascospore release period in two counties in northwestern WA in 2015 and 2016. Ascospores were detected from early March until early April in both years. All four cultivars presented susceptible vegetative and floral buds during this period but susceptible floral buds were consistently more numerous and observed earlier than vegetative buds. The timing of peak numbers of susceptible floral buds was earlier in cultivars Bluecrop and Duke compared to Draper and Liberty and peak numbers of susceptible vegetative buds of Bluecrop were observed earlier compared to the other three cultivars. Differences in susceptibility of these cultivars in the field may therefore depend on the timing of ascospore release relative to host development rather than differences in innate susceptibility. The frequency and spatial distribution of primary infections was also examined and seasonal variation was found in the incidence between bud types and no significant association between canopy heights. The outcomes of this research will be used to develop targeted and effective methods to prevent primary mummy berry infections in WA.     

Environmental and host requirements for field infection of blueberry fruits by Colletotrichum acutatum in British Columbia

Higher recovery of Colletotrichum acutatum , the causal agent of anthracnose (ripe-rot), from blueberry tissues during the growing seasons of 2002 and 2003 was found at bloom and ripe berry than at other stages of plant development. The effects of leaf-wetness duration and ambient temperature on fruit infection frequency were determined during the growing seasons of 2001–03. Potted 2-year-old blueberry plants were exposed for 1-week periods to prevailing environmental conditions and natural inoculum in a commercial field, and grown to harvest, when fruit infection was assessed. Three peaks of infection were observed: early during bloom, mid-season during the mature green berry stage, and later in the season when berries had ripened. Weather data collected simultaneously indicated that a minimum of 10 h of leaf wetness at 11°C was sufficient for fruit infection. These conditions preceded each peak of infection. To determine whether peaks of infection in the field were also caused by changes in host susceptibility or available inoculum, groups of potted blueberry plants were artificially inoculated at weekly intervals during the growing season of 2004, exposed to prevailing environmental conditions, and fruit infection assessed at harvest. Flowers and developing fruits were found to be susceptible throughout the season, indicating that specific peaks of infection were associated with environmental conditions and availability of inoculum.     

Inoculum prevalence, host infection and biological control of Colletotrichum acutatum: causal agent of blueberry anthracnose in British Columbia

To identify the causal organism of anthracnose (ripe-rot), which reduces yield and postharvest quality of blueberries grown in British Columbia, Canada, 80 isolates were recovered from diseased fruits collected from commercial blueberry fields during 2002–04 and identified as Colletotrichum acutatum using colony morphology, growth rate and species-specific PCR primers. In vitro incubation of replicated sets of inoculated detached berries at various temperatures produced infection at temperatures of 7–30°C, with an optimum at 20°C. Colletotrichum acutatum could not survive on the soil surface as mummified berries but the pathogen was detected mostly within flower buds and less so in blueberry twigs and fruit trusses. Infection of developing flower buds in May–June of the preceding growing season gave the highest inoculum recovery in the following year. Two commercial fungal biocontrol agents, Prestop ( Gliocladium catenulatum ) and PlantShield ( Trichoderma harzianum ), each reduced anthracnose development in 2003 and 2004 by up to 45% when sprayed three times onto plants between flowering and fruit ripening.     

Interactions Between Chill-Hours and Degree-Days Affect Carpogenic Germination in Monilinia vaccinii-corymbosi

ABSTRACT The relationship of cumulative chill-hours (hours with a mean temperature <7.2 degrees C) and heating degree-days (base 7.2 degrees C) to carpogenic germination of pseudosclerotia of Monilinia vaccinii-corymbosi, which causes mummy berry disease of blueberry, was investigated. In two laboratory experiments, pseudosclerotia collected from rabbiteye blueberry in Georgia were conditioned at 5 to 6 degrees C for 26 to 1,378 h prior to placement in conditions favorable for germination and apothecium development. The number of chill-hours accumulated during the conditioning period affected the subsequent proportion of pseudosclerotia that germinated and produced apothecia, with the greatest incidence of carpogenic germination occurring after intermediate levels of chilling ( approximately 700 chill-hours). The minimum chilling requirement for germination and apothecium production was considerably lower than that reported previously for pseudo-sclerotia from highbush blueberry in northern production regions. The rate of carpogenic germination was strongly affected by interactions between the accumulation of chill-hours and degree-days during the conditioning and germination periods; pseudosclerotia exposed to prolonged chilling periods, once transferred to suitable conditions, germinated and produced apothecia more rapidly (after fewer degree-days had accumulated) than those exposed to shorter chilling periods. Thus, pseudosclerotia of M. vaccinii-corymbosi are adapted to germinate carpogenically following cold winters (high chill-hours, low degree-days) as well as warm winters (low chill-hours, high degree-days). Results were validated in a combined field-laboratory experiment in which pseudosclerotia that had received various levels of natural chilling were allowed to germinate in controlled conditions in the laboratory, and in two field experiments in which pseudosclerotia were exposed to natural chilling and germination conditions. A simple model describing the timing of apothecium emergence in relation to cumulative chill-hours and degree-days was developed based on the experiments. The model should be useful for better timing of field scouting programs for apothecia to aid in management of primary infection by M. vaccinii-corymbosi.     

Spatiotemporal Description of Epidemics Caused by Phoma ligulicola in Tasmanian Pyrethrum Fields

ABSTRACT Spatial and temporal patterns of foliar disease caused by Phoma ligulicola were quantified in naturally occurring epidemics in Tasmanian pyrethrum fields. Disease assessments (defoliation incidence, defoliation severity, incidence of stems with ray blight, and incidence of flowers with ray blight) were performed four times each year in 2002 and 2003. Spatial analyses based on distribution fitting, runs analysis, and spatial analysis by distance indices (SADIE) demonstrated aggregation in fields approaching their first harvest for all assessment times between September and December. In second-year harvest fields, however, the incidence of stems with ray blight was random for the first and last samplings, but aggregated between these times. Spatiotemporal analyses were conducted between the same disease intensity measures at subsequent assessment times with the association function of SADIE. In first-year harvest fields, the presence of steep spatial gradients was suggested, most likely from dispersal of conidia from foci within the field. The importance of exogenous inoculum sources, such as wind-dispersed ascospores, was suggested by the absence of significant association between defoliation intensity (incidence and severity) and incidence of stems with ray blight in second-year harvest fields. The logistic model provided the best temporal fit to the increase in defoliation severity in each of six first-year harvest fields in 2003. The logistic model also provided the best fit for the incidence of stems with ray blight and the incidence of flowers with ray blight in four of six and three of six fields, respectively, whereas the Gompertz model provided the best fit in the remaining fields. Fungicides applied prior to mid-October (early spring) significantly reduced the area under disease progress curve (P < 0.001) for defoliation severity, the incidence of stems with ray blight, and the incidence of flowers with ray blight for epidemics at all field locations. This study provides information concerning the epidemiology of foliar disease and ray blight epidemics in pyrethrum and offers insight on how to best manage these diseases.     

Relationships Between Blueberry Flower Age, Pollination, and Conidial Infection by Monilinia vaccinii-corymbosi

ABSTRACT Monilinia vaccinii-corymbosi infects open blueberry flowers via the gynoecial pathway, leading to mummification of the developing fruit. To determine the effect of flower age on infection, stigmata were inoculated with conidia of M. vaccinii-corymbosi between 0 and 5 days after anthesis, fungal growth rates through the stylar canal were measured in detached flowers in the laboratory, and fruit disease incidence was determined in plants grown in the greenhouse. Hyphal growth rates were greatest in flowers inoculated on the day of anthesis, declined linearly with increasing flower age at inoculation (r = 0.921; P < 0.0001; n = 12), and were unaffected by the presence or absence of pollen applied at the time of inoculation. In greenhouse-grown plants, the percentage of infected fruit decreased exponentially with increasing flower age at inoculation (R = 0.878; P = 0.0057; n = 10), with disease incidence ranging from 76.4% for flowers inoculated on the day of anthesis to 15.5% for those inoculated 4 days later. Fruit disease incidence in the greenhouse was linearly correlated with hyphal growth rates in detached flowers (r = 0.985; P < 0.0001; n = 9), justifying the use of detached flowers when investigating gynoecial infection by M. vaccinii-corymbosi. In separate experiments, the effects of timing and sequence of pollination and inoculation on hyphal growth rates through the stylar canal and on disease incidence were investigated. Application of pollen to detached flowers 1 or 2 days before inoculation reduced hyphal growth rates by between 14.0 and 42.9% compared with flowers that received pollen and conidia simultaneously. Similarly, reductions in fruit disease incidence by between 9.5 and 18.3% were observed on greenhouse-grown plants for pollination-to-inoculation intervals ranging from 1 to 4 days. These results document that newly opened flowers are most susceptible to infection by M. vaccinii-corymbosi and that fruit disease incidence is reduced if pollination occurs at least 1 day before inoculation. Strategies that lead to early pollination of newly opened flowers may be useful for managing mummy berry disease in the field.     

Effects of shading and soybean Glycine max (L.) interference on Solanum ptycanthum (Dun.) (eastern black nightshade) growth and development

Summary. Solanum ptycanthum (Dun.) vegetative and reproductive growth was evaluated under shade and in the field with soybean interference. In full sunlight without soybean interference, a S. ptycanthum plant produced 243 g shoots and 5957 berries in 20 weeks, but only 38 g and 576 berries in 11 weeks. Plants grown in 94% shade produced 3 g of shoots and 23 berries in 20 weeks, and 1 g and 1 berry in 11 weeks. S. ptycanthum plants that emerged with the soybeans and were positioned between 75-cm rows produced 43 g shoots and 264 berries, whereas plants positioned in 75-cm rows and emerging 6 weeks after the soybeans produced 1 g and 16 berries. When grown between 37·5-cm rows for the same period of time this weed produced 12 g and 2 berries plant⁻¹; plants positioned in 37·5-cm rows produced shoots less than 1 g in weight and one berry plant⁻¹. Shoot growth and berry production of S. ptycanthum increased from 80 to 200% in a 2-week period between the initiation of soybean leaf abscission and maturity. In a season about 50 000 seeds weed⁻¹ were produced in full sunlight; 20 000 or less were produced under soybean interference. When grown in irradiance levels from full sunlight to 94% shade, viable seeds were first detected 10 days after anthesis and essentially all seeds in the berry were viable 24 days after anthesis     

蓝莓间座壳芽枯病病原菌鉴定及其生物学特性

<正>蓝莓(Vaccinium corymbosum L.),属于杜鹃花科(Ericaceae)越橘属(Vaccinium)多年生小浆果类果树,果实蓝色,营养丰富,具有良好的保健作用。随着蓝莓的大面积商业化种植,其病害的发生也愈加频繁。2013年7月对沈阳市蓝莓种植园病害调查时,发现一种新病害。该病主要危害基生枝中上部芽眼,受害芽坏死,芽眼周围出现褐色或红褐色椭圆形病斑,凹陷,后期中部呈灰白色,病斑     

豆荚野螟对豇豆不同器官的产卵选择性研究

豆荚野螟对寄主不同器官具有产卵选择行为,已有的产卵选择性研究尚未明确豆荚野螟对寄主花、蕾以及其他器官的产卵选择性差异。本研究调查了盛花初期和盛花期豇豆花、蕾、茎尖、叶片和豆荚上豆荚野螟的卵粒分布情况,在此基础上设计室内豆荚野螟对盛花期豇豆器官的产卵选择性试验。结果表明,有54.1%的卵粒分布在盛花期的豇豆蕾上,并且蕾上的平均卵量显著高于花、茎尖、豆荚和叶片上的卵量。本研究结果证实了豆荚野螟对寄主不同器官具有显著的产卵选择性,进一步明确了豆荚野螟偏好于在寄主蕾上产卵的特性,为豆荚野螟的综合治理提供了理论指导。     

Analysis of the association between the incidence of two spatially aggregated foliar diseases of strawberry

ABSTRACT Association of the incidence of leaf blight (caused by Phomopsis obscurans) and leaf spot of strawberry (caused by Mycosphaerella fragariae) was assessed at multiple scales in perennial plantings at several commercial farms over 3 years (1996 to 1998). For each field, the presence or absence of each disease was recorded from n = 15 leaflets in each of N approximately 70 evenly spaced sampling units, and the proportion of leaflets with blight, spot, and total disease (blight or spot) was determined. Individual diseases and total disease incidence were all well described by the beta-binomial distribution but not by the binomial distribution, indicating overdispersion of disease. The Jaccard similarity index was used to measure disease co-occurrence at the leaflet, sampling-unit, and field scales. Standard errors of this index for the lower two scales were obtained using the jackknife (resampling) procedure, and data randomizations were used to determine the expected Jaccard index for an independent arrangement of the two diseases, conditioned on the incidence and spatial heterogeneity of the observed disease data. Results based on these statistics showed that only 4 of 52 data sets at the leaflet level and no data sets at the sampling-unit level had Jaccard index values significantly different from that expected under an independent rearrangement of the two diseases. Rank correlation and cross-correlation statistics were calculated to determine the degree of covariation in incidence between the two diseases. Additionally, covariation between diseases was tested using a new procedure in the Spatial Analysis by Distance IndicEs (SADIE) class of tests. Covariation was detected in 21% of the data sets using rank correlation methods and in 15% of the data sets using the SADIE-based approach. The discrepancy between these two methods may be due to the rank correlation procedure not taking into account the effects of spatial pattern of disease incidence. There was no relationship between mean disease incidence per field of spot and blight or between degree of heterogeneity of the two diseases (as measured by theta of the beta-binomial distribution), demonstrating lack of covariation at the field scale. Incidence of leaflets with either disease (total disease incidence) could be well predicted using a linear combination of the estimated probabilities of leaf blight and leaf spot incidence based on independence of the two diseases. Heterogeneity of total disease incidence, measured with the estimated theta parameter of the beta-binomial distribution, could also be well predicted using a linear combination of the weighted theta values for leaf blight and leaf spot, with weights proportional to incidence of the individual diseases.     

The epidemiology of powdery mildew on concord grapes

ABSTRACT Vitis labruscana 'Concord' is a grape cultivar widely grown in the United States for processing into juice and other grape products. Concord grapes are sporadically but sometimes severely damaged by the grape powdery mildew pathogen, Uncinula necator. Although the foliage is often reported to be moderately resistant to powdery mildew, severe fruit infection occurs in some years. We observed the seasonal development of powdery mildew on leaves, rachises, and berries of unsprayed Concord grapevines. Inoculations of flower and fruit clusters revealed a brief period of berry susceptibility and a protracted period of rachis susceptibility. The rachis remained highly susceptible to infection, and the severity of rachis infection increased throughout the growing season until the rachis formed a periderm shortly before harvest. In contrast, berries were nearly immune to infection within 2 weeks after fruit set. Rachis and berry infections were detected before the disease was observed on foliage, and the incidence of rachis and berry infection often exceeded disease incidence observed on foliage until after fruit acquired substantial ontogenic resistance. Excellent control of fruit infection, and adequate control of leaf infection, was achieved by two fungicide applications targeted at the peak period of fruit susceptibility. Although Concord is thought to be moderately resistant to powdery mildew, the rachis is highly susceptible, and may be the avenue by which prebloom infections make their way onto the developing fruit. Late-season infection of the rachis neither spread to the fruit, nor did it cause fruit to drop prematurely, and may be of little economic consequence on fruit destined for processing. Although fruit of V. vinifera cultivars have been reported to remain susceptible to infection until berry sugar levels reach 8 to 15%, Concord fruit become nearly immune to infection nearly 6 weeks before this stage of development. Because powdery mildew does not become conspicuous on foliage until late summer, it is generally regarded as a late-season problem on Concord grapes, and previous management programs have reflected this belief. However, the greatest contribution to control of fruit infection is due to fungicides applied during the peak period of fruit susceptibility, from bloom until shortly after fruit set, long before the disease is observed on foliage.     

Verbena as a trap crop to suppress thrips-transmitted Tomato spotted wilt virus in chrysanthemums

The effect of verbena as a trap crop on the occurrence of western flower thrips, Frankliniella occidentalis, and the incidence of Tomato spotted wilt virus (TSWV) in chrysanthemums were investigated. Verbena cvs. Pink Parfait and/or Fancy Parfait were cultivated alongside chrysanthemum cv. Jimba in a greenhouse in the proportion of 17%–25% of the chrysanthemum plants. Verbena plants attracted vector thrips, reducing western flower thrips colonization of chrysanthemum until flower bud initiation, and markedly suppressing TSWV incidence on chrysanthemums until flowering. Significant quantities of linalool oxide pyran were produced by the flower of cv. Fancy Parfait; and the ratio of cis-linalool oxide pyran, an attractant for vector thrips, to the trans-type was approximately 1 : 5. Our results suggest that cultivation of verbena as a trap crop may be useful in integrated pest management programs as a control for thrips-transmitted TSWV in chrysanthemums.     

Population dynamics of epiphytic mycoflora and occurrence of bunch rots of wine grapes as influenced by leaf removal

Population dynamics of epiphytic fungi associated with the summer bunch rot complex of five wine grape ( Vitis vinifera ) varieties in commercial vineyards in the San Joaquin Valley of California were monitored every two weeks by berry washings during 1989-1992. Vines in the five replicated experiments were subjected to basal leaf removal or left unaltered. Although numerous genera of fungi were isolated, species of Cladosporium, Aspergillus, Penicillium and Alternaria predominated. Population densities of most fungal taxa increased at or after véraison. Leaf removal in the fruiting zones of bilateral cordon-trained vines generally reduced ( P >0·05) mid to late season numbers of epiphytic mycoflora: species of Penicillium, Botrytis and Aspergillus were most commonly reduced. Populations of Alternaria spp. and yeasts were not consistently affected by leaf removal. Numbers of fungi were no lower on berries when leaves were removed from both sides of vines than when leaves were removed only from the shaded side. Incidence and severity of bunch rots (sour rot, rots caused by Botrytis cinerea, Aspergillus niger , and total rot) at harvest were consistently reduced where leaves had been removed in comparison to vines where no leaves were removed. In one experiment, berries from vines sprayed with the grower's choice of pesticides at 50% or 100% of label rates had similar numbers of epiphytic mycoflora in both cases frequently lower than those from unsprayed controls. There was a significant interaction between chemical rate and leaf removal on the incidence of sour rot at harvest. Timing and extent of leaf removal did not affect population dynamics of epiphytic fungi, or incidence or severity of bunch rots ( P ≤0·05) at harvest in other trials.     

Assessment of the impact of mid-season late blight infection on disease development and yield of potato variety Russet Norkotah in Maine

Development of late blight of potatoes caused by Phytophthora infestans (US 8 fungal genotype, A2 mating type) was monitored in two Russet Norkotah commercial fields at Fort Fairfield in 1996 and Duncan Farm in 1997. Experimental plots representing various disease treatments (low, moderate, high and random late blight severity levels) were established in two fields in 1996. In 1997, only low and high disease treatments were established. The application of fungicides for late blight control was conducted in both years. Late blight incidence and severity were assessed in each plot of each treatment. Components of late blight disease development, tuber blight incidence and tuber yields were determined from each plot. Progress of late blight disease was rapid in 1996 but not in 1997. During the 1996 cropping season, mean disease incidence and severity in the random disease treatment plots were 84 and 21% respectively within 10 days of disease detection. In 1997, low levels of late blight severity were detected in the field plots. Average numbers of late blight leaf and stem lesions on infected plant and fungal sporangia on the diseased leaf were not significantly affected by disease treatment. Late blight foliar severity significantly affected potato tuber yields. Lowest tuber yield was obtained in plots with high disease levels and highest yields were recorded in plots with low late blight severity in 1996. Late blight severity was significantly correlated with tuber yield but not with per cent tuber blight.     

Influence of canopy structure on sheath blight epidemics in rice

Sheath blight (caused by Rhizoctonia solani) is one of the most important constraints in achieving high grain yield in intensive rice production systems. Canopy structure can influence the development of sheath blight epidemics. The objective of this study was to determine the effect of canopy structure parameters such as shoot number, leaf area index, biomass production, contact frequency, light transmittance and plant height on the development of sheath blight epidemics in commercial fields. Field experiments were conducted in both early and late seasons of 2009 and 2010 in Wuxue, Hubei province, China. The effects of nitrogen (N) rate and hill density on structure and production parameters and sheath blight severity were investigated. Sheath blight severity was recorded as a sheath blight index or relative lesion height on inoculated and uninoculated plants in each crop. Lesion length was measured on inoculated plants in 2010. The results showed that the sheath blight index increased with an increase of N rate and hill density in uninoculated plots in each trial. Stepwise multiple regression analysis demonstrated that contact frequency was consistently related to sheath blight. Lesion length on inoculated plants was not correlated with canopy structure. These results indicate that canopy structure influences sheath blight epidemics. A ‘healthy’ canopy resulting from appropriate crop management practices can be used to suppress sheath blight epidemics in rice.     

冬型中国梨木虱在梨树不同部位的产卵特点

昆虫母代产卵部位的选择特点直接影响到子代的生存适应性,但已有研究对冬型中国梨木虱产卵部位选择特点尚未明确。本研究调查了冬型中国梨木虱随时间变化在梨树花芽、叶芽、枝条基部、花柄、幼叶上产卵特点的变化。结果表明,冬型梨木虱产卵期约45 d,以枝条基部刻痕处着卵量最大,显著高于其他部位。冬型梨木虱产卵部位的选择随梨树的物候变化而变化:萌芽前,优先选择枝条顶芽,其次在腋芽和枝条基部刻痕处产卵;花期和展叶期,花芽、叶芽、枝条基部刻痕处着卵量下降,主要于花柄和幼叶部位产卵;冬型梨木虱产卵部位的选择顺序依次为花芽、叶芽、枝条基部、花柄、幼叶。本研究明确了冬型梨木虱在梨树不同部位产卵的变化特点,研究结果可用于指导梨木虱防控。     

转cryAb基因克螟稻对水稻白叶枯病和纹枯病的抗性评价

转cryAb基因克螟稻对水稻白叶枯病、纹枯病的抗病性在田间进行了人工接种鉴定,根据亲本材料秀水11及2个转基因材料克螟稻1号(KMD1)和克螟稻2号(KMD2)的发病情况,初步明确两个转基因材料的抗病性与亲本存在显著的差异,对白叶枯病的抗性比亲本材料有所上升,但对纹枯病的抗性则不如亲本秀水11。     

玉米病害发生现状与推广品种抗性对未来病害发展的影响

 随着全球气候变化、耕作方式改变和新品种推广,我国玉米病害的发生也有所改变。在春玉米区,丝黑穗病仍然持续严重为害,大斑病呈加重趋势;在夏玉米区,局部地区小斑病发生较重,而矮花叶病普遍发生较轻;以往的次要病害已成为重要病害:如,南方锈病在夏玉米区南部严重发生,瘤黑粉病成为生产中的突出问题,土传病害日益加重,细菌性病害发生渐多。对玉米主要推广品种、近年国家和主产省份审定品种的抗病性分析表明,在北方春玉米区,由于品种抗性水平降低、个别感病品种的推广及病原菌致病力变异,大斑病在近年仍将呈现较重发生趋势;丝黑穗病的发生则由于推广抗病品种和种子包衣技术而有所减轻,但局部地区仍会严重发生;由于缺乏抗病品种,灰斑病和弯孢菌叶斑病的发生将主要取决于气候因素。在北方夏玉米区,小斑病暴发的可能性较小,但已有强致病力菌株出现;由于推广品种普遍对茎腐病抗性水平较低并受耕作制度的影响,茎腐病和苗枯病将成为主要病害;多数品种对南方锈病缺乏抗性,南方锈病发生面积将继续扩大,发病程度也将增加。     

Berry infection and the development of bunch rot in grapes caused by Aspergillus carbonarius

The effects of different levels of inoculum of Aspergillus carbonarius and time of inoculation on berry infection and the development of aspergillus bunch rot on grapevines (cv. Sultana) were studied under field conditions. Inflorescences at full bloom were inoculated with aqueous spore suspensions of A. carbonarius containing 0 or 1 × 10⁶ spores mL⁻¹ in 2004/05 and 0, 1 × 10² or 1 × 10⁵ spores mL⁻¹ in 2005/06. In both years, the incidence of infection in inoculated berries was significantly higher than in uninoculated berries. Incidence of infection in berries from veraison until harvest was higher than at earlier stages of bunch development (berry set to berries that were still hard and green). Inoculation of bunches at veraison did not significantly increase A. carbonarius infection prior to harvest, at harvest, 6 days after harvest or when berries were over-ripe. Bunches inoculated at harvest did not significantly increase infection 6 days after harvest or when berries were over-ripe. Aspergillus carbonarius was isolated more frequently from the pedicel end (53·1%) than from the middle section (37·5%) and distal end (35·0%) of berries that were inoculated with 10⁵ spores mL⁻¹.     

Studies of crop loss in potato blight caused by Phytophthora infestans

Relationships between healthy haulm area (HHA) and yield, and between losses of HHA and yield in the potato late blight system, were evaluated in several seasons and fields variously affected by the disease in Israel. The results showed that because of the different yield potential of potatoes cultivated in different conditions, evaluation of crop losses cannot be separated from evaluation of yield potentials of the crop as influenced by environmental and cultural factors.
In one calculation the yield and the HHA in the healthiest plot in each field were equated to 100% and losses in other plots were derived from comparisons with this plot. In such a calculation the relationships of yield loss to HHA loss in all fields and seasons fitted one regression equation, and a high correlation was obtained between both parameters. However, the actual haulm areas and yield weights differed widely from one field to another, even in the healthiest plots. Also, a similar percentage of destroyed haulms sometimes corresponded to different areas of the remaining haulms and to different yields. So no correlation was found between HHA and yields over all fields and seasons. Such a correlation was found only for several plots, variously affected by late blight, in the same field and season and in different fields and seasons yields responded in a different way to increases in HHA.