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1.
Plant Dis ; 105(2): 324-330, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32762330

RESUMO

Fig limb dieback is a cosmopolitan disease caused by Neoscytalidium dimidiatum (Botryosphaeriaceae), characterized by branch and shoot cankers, discoloration of woody tissues, and dieback. The present study investigated the etiology of the disease in California that seems to have become prevalent among fig orchards in the last several years. During orchard surveys in Fresno, Kern, and Madera Counties over 3 years, we isolated consistently and evaluated the pathogenicity of N. dimidiatum under laboratory and field conditions. The effect of summer and winter pruning on the disease severity and the effects of different environmental and mechanical stresses, such as sunburn and wounding by mallets, were assayed. In addition, the susceptibility of six different cultivars and the effects of eradicating cankered shoots from the fig trees as a method to combat the spread of the disease were studied. Pathogenicity tests demonstrated that N. dimidiatum induces cankers on fig, mainly on wounded shoots. Results from the remaining experiments revealed that summer infection leads to more severe canker lesions than those induced by winter infection and that stressed shoots are more susceptible to infection than nonstressed shoots. 'Brown Turkey', 'Conadria', and 'Calimyrna' cultivars (all nonpersistent figs, i.e., needing pollination for fruit development) were less susceptible than the more susceptible 'Kadota', 'Sierra', and 'Black Mission' (all persistent figs, i.e., not needing pollination for fruit development). Canker removal from the orchard seems to be a good agronomic practice to avoid the spread of disease.


Assuntos
Ficus , Ascomicetos , California , Filogenia , Doenças das Plantas , Turquia
2.
Plant Dis ; 104(4): 1069-1075, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32027568

RESUMO

In this study, a mycelial growth assay was used to evaluate the sensitivity to thiophanate-methyl of 144 Botrytis cinerea isolates (collection A) from Californian vineyards and pistachio and pomegranate orchards. Based on the effective concentration that inhibits 50% of growth (EC50) values for mycelial growth inhibition on fungicide-amended media, 3, 28, 10, and 58% of the isolates showed sensitivity (SS; EC50 < 1 µg/ml), low resistance (LR; 1 < EC50 < 10 µg/ml), weak resistance (WR; 10 < EC50 < 50 µg/ml), and high resistance (HR; EC50 > 100 µg/ml) toward thiophanate-methyl, respectively. The LR and HR phenotypes were observed in pistachio and pomegranate orchards, even though pomegranate was not sprayed with thiophanate-methyl. Sensitivity to thiophanate-methyl of a historical collection of 257 B. cinerea isolates (collection B) isolated from pistachio orchards in 1992, 2005, and 2006 was assessed on potato dextrose agar amended with thiophanate-methyl at the discriminatory concentration of 10 µg/ml. Average percentages of thiophanate-methyl-resistant isolates were 50, 72, and 64% in the orchards in 1992, 2005, and 2006, respectively. A study of fitness components of selected thiophanate-methyl-resistant (LR, WR, and HR) and -sensitive (SS) isolates from collection A did not reveal any significant difference between them with respect to mycelial growth on fungicide-free media and pathogenicity on cultivar Crimson Seedless berries. Comparison of ß-tubulin sequences from resistant and sensitive phenotypes revealed that a glutamic acid at position 198 was changed to alanine in all HR isolates and three LR isolates. The occurrence of thiophanate-methyl resistance in B. cinerea populations should be considered when designing spray programs against blossom and shoot blight of pistachio and gray mold of grape.


Assuntos
Pistacia , Tiofanato , Botrytis , Farmacorresistência Fúngica , Fazendas , Frutas , Punica granatum
3.
Plant Dis ; 100(7): 1405-1413, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30686194

RESUMO

Panicle and shoot blight of pistachio caused by species of Botryosphaeriaceae fungi remains one of the major diseases of pistachio in California, with the highest potential for crop destruction because buds and fruit clusters (panicles) are killed. Pistachio fruit can also be damaged by various insect pests. For instance, hemipteran insects are considered major pests of pistachio and can attack maturing fruit, causing necrotic areas on the fruit epicarp (epicarp lesion). Surveys in pistachio orchards showed a putative association of punctures of pistachio fruit with infection by Botryosphaeriaceae fungi, resulting in panicle and shoot blight. This study was undertaken to determine any association of Botryosphaeriaceae fungi with fruit bearing epicarp lesions and whether hemipteran insects can actively carry propagules of the pathogens to healthy fruit and cause disease. Three large insects of the order Hemiptera (Thyanta pallidovirens, Acrosternum hilare, and Leptoglossus clypealis) were used in pathogen-spread and infection experiments. The most frequently isolated species of the family Botryosphaeriaceae in pistachio, Neofusicoccum mediterraneum, was used in these transmission experiments. Significantly higher incidence of fruit infected by N. mediterraneum was recorded when pistachio clusters were sprayed with a spore suspension of N. mediterraneum and caged with the above insects than the level of infected fruit sprayed similarly with the pathogen but caged without any insects. Furthermore, increasing the number of insects caged with pistachio clusters resulted in an increase of insect feeding punctures and, subsequently, disease incidence. Similarly, increasing the number of wounds per fruit made with a needle, simulating injuries caused by the insect's stylet, resulted in significantly higher incidence of infected fruit than for wounded fruit with fewer injured sites. In addition, bird-injured fruit were also associated with higher incidence of panicle blight than fruit not injured by birds, especially in orchards with high disease incidence. In laboratory experiments, wounding or applying fruit sap to nonwounded fruit resulted in significantly higher incidence of infected fruit than in nonwounded fruit without sap. In field experiments, wounding of fruit before or after inoculation with N. mediterraneum resulted in higher disease incidence than nonwounded and inoculated fruit. Additionally, fruit sap enhanced initial mycelial growth of N. mediterraneum. Protecting fruit clusters from injuries by hemipteran insects or birds using mesh cages significantly reduced the incidence of panicle and shoot blight. The association of wounding by hemipteran insects and birds with high incidence of infected pistachio fruit may explain partially the broad distribution of Botryosphaeria panicle and shoot blight among pistachio orchards of the central San Joaquin Valley, even in areas where inoculum sources are not nearby.

4.
Plant Dis ; 98(5): 636-652, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-30708543

RESUMO

Species of family Botryosphaeriaceae and genus Diaporthe (anamorph: genus Phomopsis, family Diaporthaceae) were reported and caused diseases on various fruit and nut trees in California. In the last several years, diseases on English walnut (Juglans regia) caused by species of Botryosphaeriaceae and Diaporthe were observed frequently in California. Disease symptoms include stem canker; shoot canker and blight; twig, leaf, and fruit blight; and necrotic leaf lesions. Isolates of the pathogen were collected from English walnut in 13 counties in California. The aims of this study were to identify these isolates and to test their pathogenicity to English walnut cultivars. In total, 159 California isolates were identified based on comparisons of DNA sequence data of the internal transcribed spacer, translation elongation factor 1-α, and ß-tubulin gene regions, and combined with the morphological features of the cultures and conidia. Research results revealed that isolates represent 10 species of Botryosphaeriaceae and two species of Diaporthe. These species include Botryosphaeria dothidea, Diplodia mutila, D. seriata, Dothiorella iberica, Lasiodiplodia citricola, Neofusicoccum mediterraneum, N. nonquaesitum, N. parvum, N. vitifusiforme, Neoscytalidium dimidiatum, Diaporthe neotheicola, and D. rhusicola. Pathogenicity on three English walnut cultivars ('Chandler', 'Tulare', and 'Vina') using a mycelium plug inoculation method revealed that all these species are pathogenic to all the tested cultivars, with L. citricola and N. parvum being the most pathogenic species, followed by N. mediterraneum, N. dimidiatum, and B. dothidea. Chandler was more tolerant to infection than Tulare and Vina. Results in this study determined that multiple numbers of the Botryosphaeriaceae fungi and two Diaporthe spp. cause cankers and blights of English walnut and vary in their virulence from highly to slightly virulent, respectively.

5.
Psychon Bull Rev ; 30(6): 2106-2115, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37322385

RESUMO

Sleep has long been thought of and promoted to be beneficial for memory. Some claims that sleep aids memory have been made in the absence of a critical interaction. This condition is necessary when using a commonly-used experimental design (a type of AM-PM PM-AM design). We propose that a sleep effect exists only if there is an interaction between groups (experimental and time-of-day controls) and the time of test or study (morning and evening). We show different patterns of results that would and would not support a sleep effect with empirical and model-generated data from recognition memory experiments and hypothetical data. While we use these data to make our point, our suggestions apply to any memory and non-memory-related investigation (e.g., emotional memory, false memory susceptibility, language learning, problem-solving). Testing for and finding the proper interaction will add to the evidence that sleep boosts performance.


Assuntos
Ritmo Circadiano , Sono , Humanos , Memória , Reconhecimento Psicológico , Emoções
6.
Plant Dis ; 96(2): 204-210, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30731809

RESUMO

Geotrichum candidum causes sour rot of fresh-market stone fruit such as peach and nectarine. Since 2001, the incidence of sour rot has increased in California, a semi-arid production area, which is considered atypical for the occurrence of the disease. In this study, sour rot developed at significantly higher incidence on wounded fruit compared with unwounded fruit, and disease severity increased as fruit matured. In packinghouse surveys, sour rot was found on up to 4% of non-fungicide- treated peach and nectarine fruit. In laboratory assays, sour rot developed when fruit were inoculated with a minimum of 20 conidia per inoculation site. Inoculum of G. candidum could be detected in California orchard soils at depths of up to 10 cm. The amount of inoculum in the soil was positively correlated with that on leaf and fruit surfaces of trees growing at a specific site. Moreover, inoculum of G. candidum was detected at different areas of packing lines in seven packinghouses. There were significant differences among the packinghouses evaluated, and these differences could be attributed, in part, to different sanitation practices used. Nitidulid beetles and fruit flies were found to play a role in disease transmission. These insects acquired sour rot inoculum in the orchard, and 25% of nitidulid beetles and 26% of fruit flies collected were positive for the pathogen. Spore survival in the soil over a 12-month period decreased significantly when soil depth increased from 10 to 20 cm. This study identified sources of inoculum of G. candidum in orchards and packinghouses, and provides information to guide development of disease management programs under the semi-arid conditions of California.

7.
Plant Dis ; 93(11): 1175-1181, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30754573

RESUMO

Two empirical models to predict infection events were evaluated for control of Botryosphaeria panicle and shoot blight, caused by a Fusicoccum sp., as well as the effectiveness of early-season fungicide sprays on the control of this disease of pistachio. A model incorporating wetness duration was superior to one based solely on duration of rains ≥1 mm/h for ≥4 h and with temperature ≥11°C. The wetness duration threshold (W) for rain events ≥4 mm at a given temperature (T) for high-risk infection events was W = -7.8 + 397/T and the threshold for medium-risk events was W = -6.9 + 220/T. Wet periods interrupted by ≤12 h were added together to calculate W. In two orchards with high levels of inoculum, one high-risk event resulted in 20 to 23% blighted fruit at harvest and two or three high-risk events resulted in 31 to 80% blighted fruit. Latent infections were 0 to 1% in instances where only low-risk events (one to two events) occurred prior to collection of pistachio fruit for determination of latent infections and were 17 to 36% with one to three high-risk events. Early-season fungicide sprays in April to May effectively controlled panicle and shoot blight when applied up to 12 days before predicted infection events or 5 days after.

8.
PLoS One ; 13(6): e0199127, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29924839

RESUMO

Interactions between pathogenic and nonpathogenic fungal species in the tree canopy are complex and can determine if disease will manifest in the plant and in other organisms such as honey bees. Seasonal dynamics of fungi were studied in an almond orchard in California where experimental release of the atoxigenic biopesticide Aspergillus flavus AF36 to displace toxigenic Aspergillus strains has been conducted for five years. The presence of the vegetative compatibility group (VCG) YV36, to which AF36 belongs, in the blossoms, and the honey bees that attend these blossoms, was assessed. In blossoms, A. flavus frequencies ranged from 0 to 4.5%, depending on the year of study. Frequencies of honey bees carrying A. flavus ranged from 6.5 to 10%. Only one A. flavus isolate recovered from a blossom in 2016 belonged to YV36, while members of the VCG were not detected contaminating honey bees. Exposure of pollinator honey bees to AF36 was detected to be very low. The density of several Aspergillus species was found to increase during almond hull split and throughout the final stages of maturation; this also occurred in pistachio orchards during the maturation period. Additionally, we found that AF36 effectively limited almond aflatoxin contamination in laboratory assays. This study provides knowledge and understanding of the seasonal dynamics of Aspergillus fungi and will help design aflatoxin management strategies for almond. The evidence of the low levels of VCG YV36 encountered on almond blossoms and bees during pollination and AF36's effectiveness in limiting aflatoxin contamination in almond provided additional support for the registration of AF36 with USEPA to use in almond in California.


Assuntos
Aflatoxinas/análise , Aspergillus flavus/isolamento & purificação , Abelhas/microbiologia , Produtos Agrícolas/microbiologia , Contaminação de Alimentos/prevenção & controle , Micobioma , Nozes/microbiologia , Controle Biológico de Vetores , Prunus dulcis/microbiologia , Animais , Abelhas/fisiologia , California , Produtos Agrícolas/química , Produtos Agrícolas/fisiologia , Comportamento Alimentar , Flores/microbiologia , Microbiologia de Alimentos , Pistacia/microbiologia , Polinização , Prunus dulcis/química , Especificidade da Espécie , Árvores
9.
Artigo em Inglês | MEDLINE | ID: mdl-18019229

RESUMO

We discuss the design of one-port surface acoustic wave (SAW) resonators using substrates with a partial or total degree of directivity, that is, the natural single-phase unidirectional transducer (N-SPUDT) effect. A general design method gives a resonance when all three frequencies (the required resonance frequency and the Bragg frequencies) are different. A second method has been derived from the resonance condition for a symmetrical substrate. Two further methods incorporate lamda/4 gaps. The capacitance ratio is presented as a function of the phase of the electrode reflection coefficient. The simulations use data for the N-SPUDT orientation of langasite. The reflection coefficient for Al electrodes has been calculated from finite element modeling (FEM) analysis. The approximate perturbation theory is found to agree well for small film thickness (h/lamda < 2%). The phase of the reflection coefficient is typically 150 degrees, not quite the ideal value of 180 degrees. Measurements on resonators using Al and Cu films are presented.

10.
Phytopathology ; 95(10): 1132-6, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18943464

RESUMO

ABSTRACT Brown rot, caused by Monilinia fructicola, is a destructive disease of stone fruit in California. Disease management requires information on inoculum dynamics and development of latent and visible fruit infections during the season to help make decisions on timing of fungicide treatments and choice of cultural practices. In this study, the daily spore concentration (ascospores and conidia) of M. fructicola in the air was monitored with spore traps in two prune orchards during the growing seasons in 2001 and 2002. The spore concentrations were low to moderate at early bloom, increased at full bloom, and decreased to the lowest level at the end of bloom. Improper timing of fruit thinning and irrigation in midseason increased spore concentration in the air and fruit infections late in the season. Artificial fruit inoculations were conducted periodically in 10 prune orchards in 2002 and 2004, and incidence of fruit rot at different inoculation dates was assessed. Fruit rot development rate increased linearly with inoculation date during the growing season. Natural blossom and fruit infections were monitored periodically in 10 prune orchards, and incidence of latent fruit infection was determined by using the overnight freezing-incubation technique. Incidence of fruit rot also was assessed 2 weeks before harvest in these orchards. The incidence of latent fruit infection at the pit hardening stage significantly correlated with that at the late stages and with the incidence of fruit rot at harvest.

11.
Phytopathology ; 94(11): 1189-97, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18944454

RESUMO

ABSTRACT Laboratory and field experiments were conducted to study the dispersal of Botryosphaeria dothidea conidia using single-drop impactions and natural and simulated precipitations. For laboratory studies, 200 single drops were released from a height of 1 m on infected pistachio nuts. On pieces of photographic film, 50% of the droplets were collected within 20 mm (average droplet travel distance) of the target area, and the droplets ranged from 0.041 to 3.19 mm in diameter, with an average of 0.3 mm. Each droplet carried an average of 23 B. dothidea conidia. In 3 years of field experiments, rainwater was collected in funnels connected to bottles positioned at different heights inside the tree canopy and at different distances away from the edge of tree canopy in three commercial pistachio orchards in San Joaquin, Yolo, and Glenn counties in California. Numbers of conidia in rainwater varied among and within sampling seasons by sampling dates and orchards. Up to 67,000 conidia/ml were obtained in rainwater samples collected from an orchard in Yolo County. Rainwater from orchards in Yolo and Glenn counties contained a consistently higher number of conidia than rainwater collected from the orchard in San Joaquin County. Variation in numbers of conidia also existed among heights where bottles were located. There were significantly more conidia in rainwater collected inside than outside tree canopies. Inside tree canopies, bottles located at 100 and 150 cm above ground collected more B. dothidea conidia than those placed at 50 and 200 cm. Conidia were collected as far as 1 m from the tree canopy edge. Based on data from the Glenn County orchard, a linear relationship between number of conidia (Y) and rainfall amount (X) in millimeters was determined as Y = 240X - 3,867, with r(2) = 0.91, which meant that a minimum of 16.1 mm of rain was needed to disperse conidia of B. dothidea. The power law model best described the dispersal gradients of B. dothidea propagules in the 1999-2000 and 2001-02 sampling seasons, with r(2) values of >/=0.73, whereas the exponential law model fit best for the 2000-01 data, with r(2) values of >/=0.81. In a rain simulation experiment, the intensity of the rain generated by a nozzle at 138 kPa of pressure inside the tree canopy was approximately five times higher than rain recorded outside the tree canopy. Rain removed up to 65% of conidia from infected fruit. These results confirmed that B. dothidea is a splash-dispersed pathogen with relatively short distances of spore dispersal within pistachio orchards. Only pycnidia are present in pistachio orchards; therefore, the results also indicate that inoculum of B. dothidea should be entirely splashed dispersed.

12.
Artigo em Inglês | MEDLINE | ID: mdl-15478978

RESUMO

A surface acoustic wave (SAW) longitudinally coupled resonator (LCR) filter consists of either two or three interdigital transducers located between two strongly reflecting gratings. The behavior of this structure is, in general, very complex because the transducers are of the single-electrode type, which gives strong electrode reflections. It is shown here that, for the filter passband, a number of realistic assumptions can be used to derive a very simple set of approximate relations for the device Y-matrix. The simplifications involve reciprocity, symmetry, and power conservation. The theory also uses the necessary fact that each grating, combined with its adjacent transducer, must have high directivity so that application of a voltage results in wave generation primarily toward the center of the device. For a three-transducer device, it is shown using symmetry that the central transducer behaves as if it were transparent, despite having strong electrode reflections. Hence, the device behaves as a single resonant cavity. The simple Y-matrix formulae are shown to agree very well with accurate results obtained by a coupling-of-modes (COM) analysis for both types of device. They also lead to simple formulae for the electrical loading required to obtain a flat, low-loss filter response. Equivalent circuits also are discussed.

13.
Plant Dis ; 81(12): 1416-1424, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30861795

RESUMO

In eight commercial prune (Prunus domestica cv. French) orchards, 43 to 69% of brown rot (caused by Monilinia fructicola or M. laxa) infections occurred in clustered fruit as opposed to solitary fruit. Fruit-to-fruit contact surfaces had cracked and thin cuticles and larger microcracks (up to 2,255 µm in length) surrounding the lenticels than those of non-contact surfaces (cracks up to 351 µm in length). Furthermore, fruit-to-fruit contact surfaces retained greater proportions of methylene blue, indicating absence of epicuticular wax, than the non-contact surfaces. Carbohydrate content of exudates in water placed on fruit-to-fruit contact surfaces was 15 and 22 mg/ml, while those of non-contact surfaces were 13 and 19 mg/ml after 15 and 28 h, respectively. Conidia of M. fructicola germinated faster and at higher rates, and the incidence of infection was significantly higher on fruit-to-fruit contact than on non-contact surfaces. Densities of fungal CFU were greater (27 to 98 CFU/cm2) on fruit-to-fruit contact compared to those of non-contact surfaces (7 to 29 CFU/cm2). In four experiments, after spraying to runoff with distilled water, surfaces of solitary fruit dried after 7 to 8 h at 23 ± 1°C compared to 12 to 14 h for groups of 5 to 6 fruit. After spraying the same mature fruit with 1.2 × 105 conidia/ml of M. fructicola and incubating at 24°C and >97% relative humidity, 26 to 70% and 38 to 100% of fruit placed in groups of 5 to 6 were infected after 3 days and 5 days, respectively, whereas only 2 to 13% and 21 to 65% of solitary fruit became infected. These results suggest that fruit-to-fruit contact surfaces predispose prune fruit to infection by M. fructicola, and that it might be possible to reduce fruit losses from brown rot in prune orchards by thinning fruit to reduce fruit clustering, applying early summer fungicide sprays before fruit contact occurs, and ultimately, by selection for non-clustering cultivars in prune breeding programs.

14.
Plant Dis ; 85(7): 745-749, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30823200

RESUMO

The effects of water potential (Ψ) on spore germination, germ tube elongation, mycelial growth of Botryosphaeria dothidea, and development of Botryosphaeria blight of pistachio caused by this fungus were studied in the laboratory and greenhouse. In laboratory tests, spore germination, germ tube elongation, and mycelial growth of B. dothidea increased as Ψ decreased from 0 to -2.0 MPa and declined as Ψ decreased below -2.0 MPa. Water stress (Ψ < -0.260 MPa) increased the severity of Botryosphaeria blight on young detached pistachio leaves. In greenhouse inoculation experiments, drought-stressed 2-year-old pistachio trees (leaf Ψ < -0.635 MPa) developed more severe Botryosphaeria blight disease than the nonstressed trees (Ψ > -0.485 MPa) in both 1999 and 2000 experiments. In a similar experiment using 1-year-old potted pistachio trees in 2000, withholding water treatments did not cause enough drought stress in pistachio leaves (Ψ > -0.584 MPa) and did not result in higher disease than the nonstressed trees (Ψ = -0.466 MPa). The correlation coefficient between Ψ and disease index for 1999 experiments was 0.954, and for 2000 experiments I and II was 0.981 and 0.939, respectively. These results indicate that drought stress can be a major predisposing factor of pistachio to infection by B. dothidea. Results from this study can be used to better understand the disease outbreaks in California pistachio orchards and to develop integrated management strategies by adjusting irrigation.

15.
Plant Dis ; 81(5): 519-524, 1997 May.
Artigo em Inglês | MEDLINE | ID: mdl-30861934

RESUMO

The significance of thinned fruit as a source of secondary inoculum in the spread of brown rot, caused by Monilinia fructicola, under semi-arid weather conditions of the San Joaquin Valley in California, was investigated in seven nectarine orchards in 1995 and 1996. Between 6 and 60% (depending on the orchard) of thinned fruit showed sporulation by M. fructicola. Brown rot was significantly less severe at preharvest (five orchards) and postharvest (one orchard) on fruit harvested from trees in plots from which thinned fruit were completely removed than on those in plots from which thinned fruit were not removed. M. fructicola sporulated more frequently on thinned fruit placed into irrigation trenches than on those left on the dry berms in tree rows. The incidence of preharvest fruit brown rot increased exponentially as the density of thinned fruit increased on the orchard floor. These results suggest that thinned fruit left on the floor of nectarine orchards can be a significant inoculum source of secondary infections. Removal or destruction of thinned fruit should reduce brown rot in nectarine and possibly other stone fruit orchards under semi-arid California conditions.

16.
Plant Dis ; 83(2): 189-193, 1999 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30849805

RESUMO

Four apple orchards were sampled periodically in 1995 and 1996 to determine the population levels of Mucor piriformis, the causal agent of Mucor rot. The highest population, 119 propagules of M. piriformis per g of dry soil, occurred during winter. Populations declined during summer and fall and increased again in winter and early spring of the following year. Isolates from soil and apple fruit of these orchards contained +, -, and neuter mating types, with the + being the predominant mating type. Depending on the orchard, up to 27.7% of apples infected by M. piriformis had zygospores developed on them. The time of increase in M. piriformis populations corresponded with postharvest drop and decay of apples on the orchard floor. Experiments were carried out to compare changes in M. piriformis populations in soil with intact fruit left on the orchard floor, sliced fruit, or after removal of fruit from the orchard. The greatest numbers of M. piriformis occurred in soil with apple pieces, followed by soil with intact apples, and the lowest in soil without apples. Results suggest that the best time to sample soils to determine the occurrence of M. piriformis in California apple orchards is from January to March, and practices of flail-mowing the orchard floor after harvest may increase population levels of M. piriformis in soil.

17.
Plant Dis ; 87(4): 359-365, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30831829

RESUMO

A potential microbial fungicide, Paenibacillus lentimorbus isolate CBCA-2, against Botryosphaeria dothidea, the pistachio panicle and shoot blight fungus, was obtained from healthy pistachio leaves by both in vitro and in vivo screening techniques. CBCA-2 caused 100% inhibition of pycnidiospore germination after 24 h incubation at 25°C. Malformation of pycnidiospores and hyphae, and lysis and swollen pycnidiospores of B. dothidea occurred in the presence of cell suspensions of CBCA-2. Among the five media tested, nutrient yeast dextrose broth significantly increased the production of antifungal compounds. Application of culture filtrates of CBCA-2 suppressed disease on detached pistachio leaves, but washed bacterial cells did not inhibit lesion development. Development of lesions on excised dormant stems was inhibited only when the culture filtrate was applied before fungal inoculation. Survival of the CBCA-2 after treatment with azoxystrobin (Abound), benomyl (Benlate), tebuconazole (Elite), propiconazole (Break), or trifloxystrobin (Flint) at the highest recommended concentration was not affected, but survival was affected by iprodione (Rovral). Spraying a suspension of CBCA-2 on pruning wounds before inoculation with pycnidiospores of B. dothidea significantly reduced infection compared with the unsprayed, inoculated controls.

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