scholarly journals Suppression of Basil Downy Mildew Caused by Peronospora belbahrii using Resistance Inducers, Mineral Salts and Anti-transpirants Combined with Different Rates of Nitrogen Fertilizer under Field Conditions

2017 ◽  
Vol 45 (1) ◽  
pp. 71-97
Author(s):  
Eman Ghebrial ◽  
Mohamed Nada
Keyword(s):  
Downy Mildew ◽  
Nitrogen Fertilizer ◽  
Field Conditions ◽  
Mineral Salts ◽  
Resistance Inducers

scholarly journals Bremia lactucae Infection Efficiency in Lettuce is Modulated by Temperature and Leaf Wetness Duration Under Quebec Field Conditions

Plant Disease ◽  
2015 ◽  
Vol 99 (7) ◽  
pp. 1010-1019 ◽  
Author(s):  
M. L. Fall ◽  
H. Van der Heyden ◽  
C. Beaulieu ◽  
O. Carisse
Keyword(s):  
Downy Mildew ◽  
Field Experiments ◽  
Field Conditions ◽  
Risk Indicators ◽  
Growth Chamber ◽  
Leaf Wetness ◽  
Risk Indicator ◽  
Bremia Lactucae ◽  
Infection Efficiency ◽  
Leaf Wetness Duration

More than 80% of Canadian lettuce production is located in the province of Quebec. Yet most of our knowledge on the epidemiology of lettuce downy mildew (Bremia lactucae) is derived from controlled-condition experiments or field experiments conducted in subtropical climates and, thus, cannot readily be applied to Quebec lettuce production. The influence of temperature and leaf wetness duration on the infection efficiency (IE) of B. lactucae was studied for 4 years (2003, 2004, 2012, and 2013) under field and growth-chamber conditions. IE was defined as the ratio of the number of lesions/leaf to the airborne conidia concentration (ACC). B. lactucae ACC was measured with rotating-arm samplers three times/week. In addition, 72 lettuce trap plants/sampling day were exposed to the potential airborne B. lactucae inoculum and disease intensity was assessed after 7 days of incubation in greenhouse. Under growth-chamber conditions, an ACC of 1 conidium/m3 was sufficient to cause 1 lesion/leaf, and IE ranged from 0.25 to 1.00. Under field conditions, an ACC of 10 to 14 conidia/m3 was required to cause 1 lesion/leaf, and IE ranged from 0.02 to 0.10, except in 2004, when IE ranged from 0.03 to 1.00. IE increased with increasing leaf wetness duration but decreased with increasing temperature. Also, considering an observed average temperature range from 10 to 20°C in the area of Quebec, 2 h of leaf wetness was sufficient for infection by B. lactucae. Therefore, under Quebec lettuce production conditions, a leaf wetness period of 2 h and an ACC of 10 to 14 conidia/m3 can be used as risk indicators to facilitate disease management decisions. Also, under typical Quebec weather conditions, measuring both morning and evening leaf wetness events could be used to improve the reliability of leaf wetness duration as a downy mildew risk indicator. Further research is needed to validate these risk indicators for integration into management strategies.

Effect of Different Nitrogen Fertilizer Rates and Plant Density on Growth of Water Efficient Maize Variety under Different Field Conditions

2020 ◽  
Author(s):  
A.R. Adebayo ◽  
F.R. Kutu ◽  
E.T. Sebetha
Keyword(s):  
Chlorophyll Content ◽  
Plant Height ◽  
Nitrogen Fertilizer ◽  
Plant Density ◽  
Block Design ◽  
Field Conditions ◽  
High Plant Density ◽  
Maize Variety ◽  
Number Of Leaves ◽  
Fertilizer Rates

Background: In most areas where maize is planted, the growth is usually affected by low nitrogen and high plant density. An experiment was carried out during the 2015/16 and 2016/17 planting seasons to investigate the effect of different nitrogen fertilizer rates and plant densities on growth of water efficient maize under different field conditions. Methods: The experiment was laid out in split plot arrangement fitted into randomized complete block design (RCBD) with four replicates. Measured growth parameters were plant height, chlorophyll content, leaf area, number of leaves and stem diameter. Result: Maize planted at Molelwane had tallest plant height (269.63 cm) than Taung. Maize sown at 33,333 plants/ha produced highest number of leaves (15.83) and highest chlorophyll content (59. 63 SPAD - units) was obtained in the plots fertilized with 240 kg N/ha. In this study, the plant density of 55,555 plants/ha and 240 kg N/ha can be recommended for cultivation of WEMA maize variety.

Duration of Downy Mildew Control Achieved with Fungicides on Cucumber under Florida Field Conditions

Plant Disease ◽  
2021 ◽  
Author(s):  
Andy Shirley ◽  
Gary E Vallad ◽  
Nicholas Steven Dufault ◽  
Richard Raid ◽  
Lina Quesada-Ocampo
Keyword(s):  
Downy Mildew ◽  
Fungicide Resistance ◽  
Yield Loss ◽  
Continuous Production ◽  
Field Conditions ◽  
Pathogen Population ◽  
Resistance Selection ◽  
Progress Curve ◽  
Field Activity ◽  
Nearly Continuous

Cucurbit production in Florida is impacted by downy mildew on a yearly basis. Cucurbit downy mildew (CDM), caused by Pseudoperonospora cubensis, is one of the most devastating cucurbit diseases and can lead to complete yield loss. Nearly continuous production of cucurbits occurs temporally throughout Florida, which puts extensive pressure on the pathogen population to select for individuals that are resistant to current fungicides labeled for CDM. Loss of efficacy due to fungicide resistance developing is becoming a major concern for Florida cucurbit growers who rely on these products to manage CDM. This study was established to evaluate the field activity of eleven currently utilized fungicides by determining their duration of activity when applied at various intervals for the management of CDM in cucumber under Florida field conditions. By comparing levels of percent CDM control and area under the disease progress curve (AUDPC) values, the fungicide’s duration of field activity was established. Field activities were less than one week for dimethomorph and fluopicolide; one week for cymoxanil; one to two weeks for chlorothalonil and mancozeb; two weeks for ethaboxam; two to three weeks for propamocarb , cyazofamid, and ametoctradin + dimethomorph; and two to four weeks for oxathiapiprolin and fluazinam. Knowledge of duration of field activity can potentially improve the development of CDM management programs and slow resistance selection.

Peronospora trifoliorum. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Medicago Sativa ◽  
Downy Mildew ◽  
Geographical Distribution ◽  
Systemic Infection ◽  
Seed Transmission ◽  
Field Conditions ◽  
Infected Leaf ◽  
Light Green

Abstract A description is provided for Peronospora trifoliorum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Medicago sativa subsp. saliva, M. sativa subsp. falcata. DISEASE: Downy mildew of lucerne (alfalfa). Infected leaflets, which tend to be near the top of the stem, are light green or yellow. The affected areas can vary from small localized spots to larger areas of infected leaf or a systemic infection where the entire shoot may become yellow, stunted and swollen. GEOGRAPHICAL DISTRIBUTION: Worldwide, wherever lucerne is grown. CMI Map No. 343 includes records on clover and other hosts. TRANSMISSION: Mycelium is reported to overwinter in the crown bud (42, 617). Conidia are produced the following spring and in damp and humid conditions soon spread the disease. Oospores occur but reports on their frequency under field conditions are so few that it is difficult to assess their importance in overwintering the disease. Seed transmission, though suspected by Eriksson (1930) and also reported from Italy in a sample of seed from Argentina (Campbell, 1922), is thought to be unimportant (Richardson, 1979).

Biochemical and Molecular Changes in Downy Mildew-infected Sunflower Triggered by Resistance Inducers

2011 ◽  
Vol 159 (7-8) ◽  
pp. 471-478 ◽  
Author(s):  
Katalin Körösi ◽  
Rita Bán ◽  
Balázs Barna ◽  
Ferenc Virányi
Keyword(s):  
Downy Mildew ◽  
Molecular Changes ◽  
Resistance Inducers
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