scholarly journals Metalaxyl-M, phosphorous acid and potassium silicate applied as soil drenches show different chestnut seedling performance and protection against Phytophthora root rot

2021 ◽  
Author(s):  
Jorge Nuno Rosário ◽  
Valentim Coelho ◽  
M. Ângelo Rodrigues ◽  
Soraia Raimundo ◽  
Sandra Afonso ◽  
...  
Keyword(s):  
Root Rot ◽  
Phosphorous Acid ◽  
Potassium Silicate ◽  
Phytophthora Root Rot ◽  
Seedling Performance

Comparison of phosetyl-Al, phosphorous acid and metalaxyl for the long-term control of Phytophthora root rot of avocado

1987 ◽  
Vol 27 (3) ◽  
pp. 471 ◽  
Author(s):  
KG Pegg ◽  
AW Whiley ◽  
PW Langdon ◽  
JB Saranah
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Phosphorous Acid ◽  
Growing Season ◽  
Phytophthora Root Rot ◽  
The Third ◽  
Consecutive Season

Avocado trees affected by root rot caused by Phytophthora cinnamomi Rands recovered rapidly when given injections into the trunk of phosetyl-A1 or phosphorous acid. Injected trees had greater yields(47.9-67.5 v. 4.3 kg fruit per tree) and lower leaf chloride levels (0.8-2.4 v. 4.2%, w/w) than controls in the third season after starting treatment. Phosphorous acid residues (21-83 mg kg-1) were detected in fruit from injected trees. Metalaxyl applied to the soil twice each growing season successfully controlled root rot for the first 2 seasons, but there was a significant resurgence of decline symptoms after the third consecutive season of use.

scholarly journals Suppression of Phytophthora Root Rot in Red Raspberries with Cultural Practices and Soil Amendments

HortScience ◽  
2005 ◽  
Vol 40 (6) ◽  
pp. 1790-1795 ◽  
Author(s):  
Kevin Maloney ◽  
Marvin Pritts ◽  
Wayne Wilcox ◽  
Mary Jo Kelly
Keyword(s):  
Root Rot ◽  
Cultural Practices ◽  
Soil Amendments ◽  
Severe Disease ◽  
Phosphorous Acid ◽  
Growth And Yield ◽  
Phytophthora Root Rot ◽  
Disease Symptoms ◽  
Phytophthora Fragariae ◽  
Infested Site

Various soil amendments and cultural practices were examined in both a phytophthora-infested (Phytophthora fragariae var. rubi) (+PFR) and uninfested field (–PFR) planted to `Heritage' red raspberries. Although plants in the +PFR field did not exhibit typical disease symptoms due to unseasonably dry weather, their growth was less than those in the –PFR field. After 2 years, plants in the +PFR site had the highest yields in plots treated with phosphorous acid or amended with gypsum, whereas compost-amended plots had the lowest yields in both +PFR and –PFR sites. A second field study confirmed the positive effect of gypsum on growth and yield of raspberries in an infested site. In a third study, `Titan' raspberries grown under greenhouse conditions in pots containing unamended soil from the infested site, then flooded, exhibited severe disease symptoms; however, pasteurization of the soil, treatment with phosphorous acid and metalaxyl fungicide, or gypsum amendment mostly prevented symptoms from developing. These three studies suggest that a preplant soil amendment containing certain readily available forms of calcium, such as found in gypsum, can help suppress phytophthora root rot and increase survival, growth and yield of raspberries in sites where the pathogen is present.

Control of Phytophthora Root Rot of Avocado With Phosphorous Acid.

1985 ◽  
Vol 14 (2) ◽  
pp. 25 ◽  
Author(s):  
KG Pegg ◽  
AW Whiley ◽  
JB Saranah ◽  
RJ Glass
Keyword(s):  
Root Rot ◽  
Phosphorous Acid ◽  
Phytophthora Root Rot

Phosphonate treatment effects on Phytophthora root rot control, phosphite residues and Phytophthora cactorum inoculum in young apple orchards

Plant Disease ◽  
2021 ◽  
Author(s):  
Makomborero Nyoni ◽  
Mark Mazzola ◽  
J.P.B. Wessels ◽  
Adèle McLeod
Keyword(s):  
Root Rot ◽  
Dna Analysis ◽  
Foliar Spray ◽  
Phosphorous Acid ◽  
Phytophthora Cactorum ◽  
Limited Information ◽  
Phytophthora Root Rot ◽  
Trunk Diameter ◽  
Foliar Sprays ◽  
Young Apple

Phytophthora root rot, caused by Phytophthora cactorum, is an economically important disease on young apple trees. Limited information is available on the effect of different phosphonate application methods and dosages on disease control, fruit- and root phosphite concentrations and soil- and root pathogen inoculum levels. Evaluation of phosphonate treatments in three apple orchard trials (two in the Grabouw and one in the Koue Bokkeveld region) showed that foliar sprays (ammonium- or potassium phosphonate), trunk sprays and trunk paints, were equally effective at increasing trunk diameter in one trial and yield in a second trial over a 25-month period. Foliar ammonium- and potassium phosphonate sprays (12 g phosphorous acid/tree), and two different dosages of the ammonium phosphonate sprays (~ 4.8 g or 12 g phosphorous acid/tree) were all equally effective at improving tree growth. The addition of a bark penetrant (polyether-polymethylsiloxane-copolymer) to trunk sprays did not improve the activity of trunk sprays. The low dosage ammonium phosphonate foliar spray (~4.8 g a.i./tree) was the only treatment that in general yielded significantly lower root phosphite concentrations than the other phosphonate treatments. Root phosphite concentrations were significantly positively correlated (P < 0.0001) with an increase in trunk diameter and negatively with P. cactorum root DNA quantities (P ≤ 0.001). Phosphite fruit residues were less than 31 ppm for all treatments, with the trunk paint treatment (80 g phosphorous acid/tree applied annually) yielding significantly lower residues than the higher dosage foliar sprays (~12 g a.i/tree). Twenty-one months post-treatment, most of the phosphonate treatments in all of the trials similarly significantly reduced P. cactorum DNA quantities estimated directly from roots, but not from soil based on soil baiting DNA analysis. Pathogen quantities in fine feeder roots did not differ significantly from those in higher-order roots (< 5 mm dia.). Phytophthora cactorum DNA quantities estimated using DNA quantification directly from roots were significantly correlated (P < 0.0001) with those obtained through root leaf baiting DNA analysis, and to a lesser extent with soil leaf baiting DNA quantities (P = 0.025).

Phytophthora Species Differ in Response to Phosphorous Acid and Mefenoxam for the Management of Phytophthora Root Rot in Rhododendron

Plant Disease ◽  
2020 ◽  
Author(s):  
Jerry E. Weiland ◽  
Carolyn F. Scagel ◽  
Niklaus J. Grünwald ◽  
E. Anne Davis ◽  
Bryan R. Beck
Keyword(s):  
Root Rot ◽  
Production Systems ◽  
Foliar Spray ◽  
Phosphorous Acid ◽  
Phytophthora Species ◽  
Phytophthora Root Rot ◽  
Application Method ◽  
Affect Control ◽  
Pathogen Diversity ◽  
Significant Disease

Phytophthora root rot, caused by many soilborne Phytophthora species, is a significant disease affecting the $42 million rhododendron nursery industry. Rhododendron growers have increasingly reported failure by two systemic fungicides, phosphorous acid and mefenoxam, to adequately control root rot. Both fungicides may be applied as a foliar spray or soil drench, but it is unknown how application method, fungicide chemistry, or pathogen diversity affects disease control. Therefore, two experiments were conducted to (i) determine whether differences in application method or fungicide chemistry affect control of root rot caused by P. cinnamomi and P. plurivora and (ii) evaluate the sensitivity of Phytophthora species and isolates from the rhododendron industry to each fungicide. Results demonstrated that soil drenches of either fungicide were more effective than foliar sprays for control of P. cinnamomi, but were ineffective for P. plurivora. Furthermore, Phytophthora species and isolates varied in sensitivity to phosphorous acid and mefenoxam, and there were multiple fungicide insensitive isolates, especially within P. plurivora. Differences in sensitivity were also observed among isolates from different nurseries and production systems, with some nurseries having less sensitive isolates than others and with container systems generally having less sensitive isolates than field systems. Our results provide three potential reasons for why fungicide control of Phytophthora root rot might fail: (i) the fungicide can be applied to the wrong portion of the plant for optimal control, (ii) there are differences in fungicide sensitivity among soilborne Phytophthora species and isolates infecting rhododendron, and (iii) fungicide insensitive isolates are present in the rhododendron nursery industry.

scholarly journals Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

2011 ◽  
Vol 101 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Brantlee Spakes Richter ◽  
Kelly Ivors ◽  
Wei Shi ◽  
D. M. Benson
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Cellulase Activity ◽  
Enzyme Concentration ◽  
Disease Suppression ◽  
In Vitro Assays ◽  
Infested Soil ◽  
Phytophthora Root Rot ◽  
Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

scholarly journals Phytophthora Root Rot Resistance in Soybean E00003

Crop Science ◽  
2014 ◽  
Vol 54 (2) ◽  
pp. 492-499 ◽  
Author(s):  
Zhongnan Zhang ◽  
Jianjun Hao ◽  
Jiazheng Yuan ◽  
Qijian Song ◽  
David L. Hyten ◽  
...  
Keyword(s):  
Root Rot ◽  
Phytophthora Root Rot

scholarly journals Influence of Pure Mulches on Suppressing Phytophthora Root Rot Pathogens

2013 ◽  
Vol 31 (4) ◽  
pp. 221-226 ◽  
Author(s):  
G.C. Percival
Keyword(s):  
Root Rot ◽  
Crop Production ◽  
Prunus Avium ◽  
European Beech ◽  
Dry Weight ◽  
Urban Trees ◽  
Horse Chestnut ◽  
Phytophthora Root Rot ◽  
Tree Vitality ◽  
Lesion Severity

Mulching as a means of controlling Phytophthora root rot pathogens has become recognised as a potential cultural management system within the arboricultural, nursery and landscape industry. The influence of a pure mulch, i.e., mulch derived solely from one tree species, on reducing Phytophthora root rot severity has received little study. The purpose of the conducted research was to determine if a range of pure mulches derived from European beech (Fagus sylvatica L.), common hawthorn (Crataegus monogyna JACQ), silver birch (Betula pendula ROTH.), common cherry (Prunus avium L.), evergreen oak (Quercus ilex L.) and English oak (Q. robur L.) could reduce the development and impact of pathogen severity caused by Phytophthora cactorum and P. criticola on containerised horse chestnut (Aesculus hippocastanum). Irrespective of Phytophthora pathogen, leaf area, leaf, shoot, root and total plant dry weight following application of a pure mulch was higher than non-mulched controls. Likewise, leaf chlorophyll content, chlorophyll fluorescence Fv/Fm ratios, photosynthetic rates and root carbohydrate concentration as measures of tree vitality were higher in pure mulched compared to non-mulched control trees. Application of a pure mulch had a significant influence on Phytophthora root rot lesion severity. In the case of P. cactorum root rot lesion severity was reduced by 39–63%. In the case of P. criticola root rot lesion severity was reduced by 33–61%. In conclusion, pure mulches offer positive benefits for those involved in the care and maintenance of urban trees as well as nursery, forestry, orchard and horticultural crop production where Phytophthora pathogens are problematic.

scholarly journals Evaluating the Efficacy of the Systems Approach at Mitigating Five Common Pests in Oregon Nurseries

2014 ◽  
Vol 32 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Nancy K. Osterbauer ◽  
Melissa Lujan ◽  
Gary McAninch ◽  
S. Lane ◽  
Aaron Trippe
Keyword(s):  
Root Rot ◽  
Systems Approach ◽  
Phytophthora Root Rot ◽  
Potted Plants ◽  
Foliar Blight ◽  
Total Percentage ◽  
Phytophthora Spp ◽  
Root Weevils ◽  
Pest Incidence ◽  
Point Inspection

In Oregon, the U.S. Nursery Certification (USNCP), Grower Assisted Inspection (GAIP), and Shipping Point Inspection (SPI) programs are used to certify nursery plants as pest free. To compare the programs' effectiveness for mitigating pest risk, potted plants grown within two USNCP, two GAIP, and two SPI nurseries were surveyed for Phytophthora root rot (Phytophthora spp.), Phytophthora foliar blight (Phytophthora spp.), bittercress (Cardamine spp.), snails and slugs (Class Gastropoda), and root weevils (Otiorhynchus spp.). A total of 1,635 plots were surveyed in the nurseries, with one or more pests detected in 1,003 plots. Based on the total percentage of plots found infested with a pest, significantly fewer were detected in the GAIP nurseries (55%) than in the USNCP nurseries (68%). However, bittercress incidence was significantly higher in GAIP nurseries (21%), while snails and slugs incidence was significantly higher in USNCP nurseries (49%), and Phytophthora root rot incidence was significantly higher in SPI nurseries (31%). Also, the plant families grown by the nurseries had a significant impact on pest incidence for two of the target pests, Phytophthora root rot and root weevils. While the GAIP seemed the best at mitigating pest incidence overall, none of the certification programs was consistently the most effective against all five target pests.

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