scholarly journals Effect of Fungicide Mobility and Application Timing on the Management of Grape Powdery Mildew

Plant Disease ◽  
2020 ◽  
Vol 104 (4) ◽  
pp. 1167-1174 ◽  
Author(s):  
Brent Warneke ◽  
Lindsey D. Thiessen ◽  
Walter F. Mahaffee
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Quality Standards ◽  
Pinot Noir ◽  
Abaxial Surface ◽  
Phenological Stages ◽  
Application Timing ◽  
Abaxial Leaf Surface ◽  
Detached Leaves ◽  
Grape Powdery Mildew

Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on region or market, in an attempt to achieve the high fruit quality standards demanded by the market. Understanding how fungicides redistribute and targeting redistributing fungicide to critical crop phenological stages could improve fungicide protection of grape clusters. This study evaluated fungicide redistribution in grapevines from major fungicide groups labeled for GPM control. Translaminar and xylem redistribution was examined by placing fungicide-impregnated filter disks on the adaxial or abaxial leaf surface of detached leaves for 10 min and then incubating for 48 h before inoculating the abaxial surface with conidia. Vapor redistribution used Teflon disks sprayed with fungicides and placed on the abaxial leaf surface of detached leaves 48 h before inoculation. Disease development was rated 10 days later. Translaminar movement through calyptra was tested using flowering potted vines. All fungicides tested redistributed through at least one mechanism. Fungicide timing at critical phenological stages (early, mid, and late bloom) was assessed in small plots of cultivar Pinot noir vines. The application of trifloxystrobin, quinoxyfen, or fluopyram at different bloom stages showed that applications initiated at end of bloom resulted in the lowest berry infection probabilities of 0.073, 0.097, and 0.020, respectively. The results of this study suggest that integrating two carefully timed applications of redistributing fungicides initiated at end of bloom into a fungicide program may be an effective strategy for wine grape growers in western Oregon to produce fruit with low GPM infection.

New and noteworthy Melastomataceae from the Yanachaga-Chemillén National Park and surrounding areas in Oxapampa, Pasco, Peru

Phytotaxa ◽  
2018 ◽  
Vol 374 (3) ◽  
pp. 185 ◽  
Author(s):  
FABIÁN A. MICHELANGELI ◽  
RENATO GOLDENBERG
Keyword(s):  
National Park ◽  
Leaf Surface ◽  
Nodal Line ◽  
Abaxial Surface ◽  
North East ◽  
The North ◽  
The Andes ◽  
Abaxial Leaf Surface ◽  
Surrounding Areas ◽  
Sclerophyllous Forests

We describe six new species of Melastomataceae from the Yanachaga-Chemillén National Park and surrounding areas from the Department of Pasco, Province of Oxapampa in Central Peru. Macrocentrum andinum is the first species of the genus described from the Andes, found along creeks at 400–500 m elev. and characterized by its anysophyllous leaves, pubescent stems and four-merous flowers. Meriania rubriflora is found in forests above 2200 m elev. and it is characterized by stem nodes with stipular flaps, leaves with an acute base and four merous, deep red flowers. Miconia palcazuana is found along rivers and streams at 300–400 m on the eastern flank of the park, and it can be distinguished by its flowers with pink anthers with glands on the connective and narrowly oblanceolate to elliptic-lanceolate leaves. Miconia yanachagaensis grows in the dwarf-sclerophyllous forests at the top of ridges and grasslands over 2800 m elev. and it is characterized by its long dendritic-pedicellate trichomes on the abaxial leaf surface, the stems flattened to terete and the presence of a conspicuous annular nodal line. Triolena rojasae is found growing on rocks along the Palcazú River and its tributaries, and it is characterized by its lanceolate-crenate leaves. Triolena vasquezii grows on the northern end of the Huancabamba canyon and the North East portion of the park and can be distinguished by its pustulate leaves with purple abaxial surface and anthers with two ventral appendages. We also present the first report of the genus Wurdastom for Peru.

Mechanisms of Resistance to Glyphosate in a Ryegrass (Lolium Multiflorum) Biotype from Chile

Weed Science ◽  
2007 ◽  
Vol 55 (5) ◽  
pp. 435-440 ◽  
Author(s):  
Paola Michitte ◽  
Rafael De Prado ◽  
Nelson Espinoza ◽  
Juan Pedro Ruiz-Santaella ◽  
Christian Gauvrit
Keyword(s):  
Leaf Surface ◽  
Lolium Multiflorum ◽  
Glyphosate Resistance ◽  
Contact Angles ◽  
Italian Ryegrass ◽  
Foliar Uptake ◽  
Mechanisms Of Resistance ◽  
Abaxial Surface ◽  
Abaxial Leaf Surface ◽  
Target Enzyme

Glyphosate behavior was examined in Italian ryegrass plants from Chile that were sensitive (S) and resistant (R) to this herbicide. In order to explain the resistance to glyphosate, contact angles, spray retention, foliar uptake, herbicide translocation, and target enzyme activity were studied. Contact angles of glyphosate solutions at a field concentration were 40° to 45° on the abaxial surface of R leaves as compared to 70° on S. Glyphosate spray retention by R plants was 35% lower than by S plants. Glyphosate uptake by the abaxial leaf surface of R plants was about 40% lower than that of S plants. In addition, in the R plants more glyphosate migrated to the tip of the treated leaves. The target enzyme in R and S plants was sensitive to the herbicide. Based on these and previous results, it is concluded that resistance in this Italian ryegrass biotype results from lower spray retention, lower foliar uptake from the abaxial leaf surface, and altered translocation pattern. The decreases in spray retention and foliar uptake constitute new mechanisms of glyphosate resistance.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in Canada

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 781-781 ◽  
Author(s):  
R. F. Cerkauskas ◽  
J. Brown ◽  
G. Ferguson ◽  
S. Khosla
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Morphological Characteristics ◽  
Chili Pepper ◽  
Width Ratio ◽  
Old Field ◽  
First Report ◽  
Leveillula Taurica ◽  
Plastic Bags ◽  
Abaxial Leaf Surface

In 1999, powdery mildew on cvs. Oberon and Triple 4 of greenhouse pepper (Capsicum annum L.) and cv. FireFlame of chili pepper was reported simultaneously in two commercial greenhouses at two separate locations, Leamington and Vineland, geographically separated by 290 km, in southern Ontario. Losses of 10 to 15% each in the 2 and 3.1 ha greenhouse pepper operations were noted. The greenhouse pepper industry in Canada consists of 89.4 ha with sales of $43.6 million (Canadian). Lesions appeared as a white, powdery coating on the abaxial leaf surface only, generally on the lower foliage of pepper plants, while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In chili pepper, this chlorosis was restricted to interveinal tissue, causing the leaves to have a somewhat netted appearance. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development. No cleistothecia were observed. Pyriform and cylindrical, hyaline, single-celled conidia were present in equal numbers. Both conidia had a network of crests and granules containing tiny, thornlike projections on the surface. These projections were also evident on the lower half of conidiophores. Pyriform conidia ranged in length from 61.6 to 84.0 μm (mean = 70.8, SE = 0.7) and in width from 14.0 to 25.8 μm (mean = 21.1, SE = 0.4, n = 50), with a mean length to width ratio of 3.4. Cylindrical conidia ranged in length from 54.9 to 80.1 μm (mean = 66.3, SE = 0.9) and in width from 15.7 to 24.1 μm (mean = 18.6, SE = 0.3, n = 50), with a mean length to width ratio of 3.1. Short conidial chains borne on conidiophores consisted of a pyriform conidium first followed by cylindrical conidium. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid:EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, conidia from infected pepper leaves were dusted onto the water-misted abaxial leaf surface of 41-day-old greenhouse pepper cvs. Cubico and Edison, and onto the similarly treated adaxial leaf surface of 58-day-old field pepper cv. Renegade. Plants were enclosed in plastic bags for 24 h on a bench. Control plants were treated identically but not inoculated. Inoculated plants developed foliar powdery mildew symptoms, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus. This is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in Canada. Reference: J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in British Columbia, Canada

Plant Disease ◽  
2003 ◽  
Vol 87 (9) ◽  
pp. 1151-1151 ◽  
Author(s):  
R. F. Cerkauskas ◽  
A. Buonassisi
Keyword(s):  
British Columbia ◽  
Powdery Mildew ◽  
Morphological Characteristics ◽  
Width Ratio ◽  
Abaxial Surface ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Cotton Blue ◽  
Pepper Leaves

In 2003, powdery mildew of greenhouse pepper (Capsicum annuum L.) was reported simultaneously in two commercial greenhouses at two separate locations near Langley in southern British Columbia. Trace amounts of mildew on the foliage of cv. Zamboni in one operation, and 10 to 80% of the foliage of cv. Triple Four was affected in an organic operation, with losses in fruit yield of 2 to 4 kg/m2, were noted. The greenhouse pepper industry in British Columbia in 2001 comprised 76 ha with sales of $41.3 million (Canadian). Affected areas appeared as a white, powdery coating on the abaxial leaf surface of older foliage while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development (2). Hyaline, single-celled pyriform and cylindrical conidia were present in 40:60 proportion, respectively. Both conidia had a network of crests and granules sometimes with tiny thorn-like projections on the surface. These projections were evident also on the lower half of conidiophores. Pyriform conidia ranged in length from 53.8 to 79.5 μm (mean = 68.0, SE = 0.8), and in width from 12.9 to 28.0 μm (mean = 20.1, SE = 0.6, n = 50) with a mean length to width ratio of 3.5. Cylindrical conidia had a length from 48.2 to 84.0 μm (mean = 66.0, SE = 0.9), and in width from 13.4 to 25.2 μm (mean = 18.6, SE = 0.4, n = 50) with a mean length to width ratio of 3.6. Short conidial chains borne on conidiophores consisted of a basal pyriform conidium followed by cylindrical conidium. No cleistothecia were observed. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid/EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, a suspension of 2 × 104 conidia/ml from infected pepper leaves was applied onto the abaxial and adaxial leaf surfaces of 60-, 42-, and 28-day-old greenhouse pepper cv. Cubico, tomato cv. Trust, and cucumber cv. Corona, respectively. Plants were maintained in a growth chamber at 25/21°C day/night temperature and 80% relative humidity. Control plants in the same chamber were treated identically but not inoculated. After 21 days, inoculated pepper plants developed foliar powdery mildew symptoms on the abaxial surface, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus (2). To our knowledge, this is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in British Columbia. The disease was first reported in Ontario, Canada in 1999 (1). References: (1) R. Cerkauskas et al. Plant Dis. 83:781,1999. (2) J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals First Report of Powdery Mildew of Kenaf Caused by Leveillula taurica in South Africa

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 923-923
Author(s):  
W. J. Swart ◽  
J. Terblanche
Keyword(s):  
South Africa ◽  
Powdery Mildew ◽  
Seed Quality ◽  
Leaf Surface ◽  
Hibiscus Cannabinus ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Extensive Growth ◽  
Northwest Province

Kenaf (Hibiscus cannabinus L.) is a fast-growing, bamboo-like annual plant belonging to the Malvaceae. The stem, which ranges from 1.5 to 4 m, presents a source of high-quality cellulose fibers. The plant is being investigated in South Africa with a view to commercial production. In April 2001, at least 50% of 4- to 5-month-old kenaf plants grown from seed in trials near Rustenburg, Northwest Province, South Africa, were observed as having powdery mildew. Signs included extensive growth of white, superficial mycelium and emergent conidiophores on the abaxial leaf surface, followed by partial defoliation. On older leaves, the abaxial leaf surface was completely covered by powdery mildew, and chlorotic and necrotic patches were clearly visible on the adaxial surface. Symptoms were observed on all five planted cultivars (Everglades 41, Cuba 108, El Salvador, SF459, and Tainung 2), and no difference in disease severity was noted among cultivars. Leveillula taurica (Lév.) Arnaud (anamorph Oidiopsis taurica [Lév.] Salmon) was subsequently identified by the presence of endophytic mycelia, often branched conidiophores, and dimorphic conidia borne singly or in short chains (1). In 100 measurements of each type, pyriform conidia averaged 69 ± 5 × 18 ± 2 μm and cylindrical conidia averaged 62 ± 6 × 16 ± 2 μm. The teleomorph was not observed. The source of L. taurica for this reported outbreak is unknown, and powdery mildew was not observed in a field of mature cotton (Gossypium hirsutum L.) growing within 10 m of the kenaf plot. L. taurica was reported on kenaf in Texas in 1992 (2) and in Italy in 1995 (3). The pathogen can cause significant losses in seed yield and reduce seed quality in susceptible kenaf cultivars. Although L. taurica has been reported from Hibiscus sabdariffa in Egypt (4), to our knowledge this is the first report of the pathogen occurring on kenaf in Africa. References: (1) H. J. Boesewinkel. Bot Rev. 46:167, 1980. (2) C. G. Cook and J. L. Riggs. Plant Dis. 79:968, 1995. (3) S. Frisullo et al. Inf. Fitopatol. 45:37–41, 1995. (4) M. Khairy, et al. Phytopathol. Medit. 10:269–271, 1971.

scholarly journals Extracuticular Wax and Contact Angle Measurements on Wheat (Triticum Vulgare L.)

1967 ◽  
Vol 20 (3) ◽  
pp. 509 ◽  
Author(s):  
JH Troughton ◽  
DM Hall
Keyword(s):  
Contact Angle ◽  
Leaf Surface ◽  
Flag Leaf ◽  
Contact Angles ◽  
Abaxial Surface ◽  
Triticum Vulgare ◽  
Angle Measurements ◽  
Abaxial Leaf Surface ◽  
Contact Angle Measurements ◽  
Plant Grown

Extracuticular wax and contact angles on wheat were studied because of their influence on the retention of chemical sprays and on disease resistance. Wax formed extensive deposits on wheat, irrespective of variety, stage of growth, or part of the plant, and these deposits overlaid or projected from the cuticle as platelets and rodlets. Platelets covered the adaxial and abaxial leaf surfaces of seedlings and some mature plants, while a net of rodlets covered the ear, culm, sheath, and flag leaf abaxial surface. Rods were occasionally present on the abaxial surface of mature vegetative leaves. Wax influenced the advancing contact angle of water droplets on wheat. Contact angles were all high, i.e. greater than 130� and generally about 150�. The contact angle on the adaxial leaf surface was higher than on the abaxial leaf surface, except on glasshouse-grown reproductive plants, where there was no difference between the two sides. Seedlings had higher contact angles than mature plants, but there was no trend in contact angle with tissue age within a leaf or within a mature plant. The contact angle on the flag leaf of glasshouse-grown reproductive Aotea plants was 24� higher than on a similar plant grown in the field.

scholarly journals Infection Studies of Mycosphaerella fijiensis on Banana and the Control of Black Sigatoka with Chlorothalonil

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1185-1190 ◽  
Author(s):  
J. R. Washington ◽  
J. Cruz ◽  
F. Lopez ◽  
M. Fajardo
Keyword(s):  
Disease Control ◽  
Leaf Surface ◽  
Infected Leaf ◽  
Mycosphaerella Fijiensis ◽  
Black Sigatoka ◽  
Abaxial Surface ◽  
Disease Symptoms ◽  
Adaxial Surface ◽  
Abaxial Leaf Surface ◽  
Banana Leaves

Infection studies with Mycosphaerella fijiensis, causal agent of black Sigatoka disease of banana (Musa AAA), demonstrated that the abaxial leaf surface is the primary infection site. Inoculation of banana plants with M. fijiensis ascospores on the abaxial surface of young leaves resulted in disease symptoms in 100% of the leaves inoculated within 18 to 30 days; whereas only 5% of the leaves inoculated on the adaxial surface showed black Sigatoka symptoms within 10 weeks. Disease symptoms appeared more rapidly on the new, emerging leaves than on the first and second fully expanded leaves. Application of chlorothalonil (1.08 kg a.i. ha-1) to the abaxial surface of emerging leaves resulted in 99 to 100% disease control in the treated area. When the emerging leaf was not sprayed until fully expanded, disease control was reduced to 76 to 80%. Application of chlorothalonil to the adaxial surface of banana leaves had little or no impact on disease control. Chlorothalonil arrested hyphal growth when applied to banana leaves after ascospores had already germinated and reduced the rate of lesion expansion when applied to the abaxial leaf surface after symptom appearance. Chlorothalonil was less effective than systemic fungicides in reducing production of M. fijiensis pseudothecia in infected tissue. When systemic and protectant fungicides were applied to infected leaf tissue, none of the fungicides affected the viability of ascospores that were discharged from pseudothecia produced in that tissue. For successful control of black Sigatoka with chlorothalonil, deposition of the fungicide on the abaxial leaf surface is essential.

Defence reactions of Hordeum chilense accessions to three formae speciales of cereal powdery mildew fungi

2000 ◽  
Vol 78 (12) ◽  
pp. 1561-1570 ◽  
Author(s):  
D Rubiales ◽  
T LW Carver
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Penetration Resistance ◽  
Blumeria Graminis ◽  
Epidermal Cells ◽  
Hordeum Chilense ◽  
Adult Plant ◽  
Formae Speciales ◽  
Abaxial Leaf Surface ◽  
Stomatal Complexes

The histology of resistance to infection by Blumeria graminis DC Speer f.sp. hordei, Blumeria graminis f.sp. tritici, and Blumeria graminis f.sp. avenae was studied in 15 accession lines of Hordeum chilense. All were highly resistant to all formae speciales. There were small differences in spore germination rates and the morphological normality of germlings formed on the different lines. Relatively large differences between accessions were detected in terms of penetration resistance and the frequency with which attacked epidermal cells died. Greater penetration resistance was expressed by epidermal cells of the seventh-formed leaves than by earlier leaves, indicating that penetration resistance is a component of adult plant resistance in H. chilense. Epidermal cells overlying vascular tissues (long epidermal cells) were more resistant to penetration than cells adjacent or close to stomatal complexes. In a limited examination involving two accession lines, epidermal cells on the abaxial leaf surface of one line were more penetration resistant than those on the adaxial surface; the other line was highly resistant on both surfaces. However, in the few cases where long cells and abaxial cells were penetrated, the frequency of associated cell death was lower than in short cells or on the adaxial leaf surface. This is consistent with the macroscopic observation that the few colonies formed on H. chilense were often close to the mid-rib and more frequent on the abaxial leaf surface. The data support the view that H. chilense offers a valuable source of powdery mildew resistance for cultivated cereals.Key words: Blumeria graminis, Erysiphe graminis, powdery mildew, disease resistance, histology, Hordeum chilense.

Picking sides: feeding on the abaxial leaf surface is costly for caterpillars

Planta ◽  
2021 ◽  
Vol 253 (4) ◽  
Author(s):  
Sakshi Watts ◽  
Rupesh Kariyat
Keyword(s):  
Leaf Surface ◽  
Abaxial Leaf Surface

scholarly journals Continuous Lighting Reduces Conidial Production and Germinability in the Rose Powdery Mildew Pathosystem

Plant Disease ◽  
2010 ◽  
Vol 94 (3) ◽  
pp. 339-344 ◽  
Author(s):  
A. Suthaparan ◽  
Arne Stensvand ◽  
S. Torre ◽  
Maria L. Herrero ◽  
R. I. Pettersen ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Interspecific Hybrid ◽  
Day Length ◽  
Artificial Light ◽  
Potted Plants ◽  
Severity Of Disease ◽  
Detached Leaves ◽  
Growth Chambers ◽  
The Rose

The effect of day length on production and germinability of conidia and severity of disease caused by Podosphaera pannosa, the causal agent of rose powdery mildew, was studied. Whole potted plants or detached leaves of Rosa interspecific hybrid ‘Mistral’ were inoculated with P. pannosa and exposed to 0, 12, 18, 20, 22, or 24 h of artificial light per day in growth chambers equipped with mercury lamps. Increasing duration of illumination from 18 to 20 to 24 h per day reduced production of conidia by 22 to 62%. Exposure to 24 h of illumination per day also strongly reduced disease severity compared with 18 h. Our results suggest that increasing day lengths from 18 h per day to 20 to 24 h may suppress the disease significantly and, thereby, reduce the need for fungicide applications against powdery mildew.

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