scholarly journals An IPM Program for Managing Fungal Leaf Blight Diseases of Carrot in New York

Plant Disease ◽  
2007 ◽  
Vol 91 (1) ◽  
pp. 59-65 ◽  
Author(s):  
B. K. Gugino ◽  
J. E. Carroll ◽  
T. L. Widmer ◽  
P. Chen ◽  
G. S. Abawi
Keyword(s):  
New York ◽  
Disease Severity ◽  
Crop Rotation ◽  
Disease Incidence ◽  
Leaf Blight ◽  
Yield Reduction ◽  
Weather Forecasts ◽  
Alternaria Dauci ◽  
Leaf Blights ◽  
Cultivar Susceptibility

Fungal leaf blight diseases caused by Cercospora carotae and Alternaria dauci occur annually on processing carrot in New York, with growers applying up to eight fungicide sprays to manage these diseases. An integrated pest management (IPM) program involving the use of a 25% disease incidence threshold to prompt the first fungicide application and timing subsequent sprays by monitoring for increases in disease severity and weather forecasts in conjunction with a 10- to 14-day spray interval was evaluated in grower fields in 1997 and 1998. The IPM plots, compared with the grower plots, required two to six fewer fungicide applications but showed no yield reduction. From 1999 to 2004, the IPM program was validated and the effect of crop rotation and carrot cultivar susceptibility also were assessed. Carrot plants growing in fields with 2-year or longer crop rotation intervals reached the 25% disease incidence threshold later in the season and required fewer fungicide applications. The less-susceptible carrot cultivars also reached the 25% disease incidence threshold later, required fewer fungicide applications, and were less severely diseased than more susceptible cultivars. Validation of the IPM program in New York showed that both fungal leaf blights can be managed effectively using a 25% incidence threshold to prompt the first fungicide spray and making the subsequent fungicide applications based on increases in disease severity, weather forecasts, and a 10- to 14-day spray interval.

scholarly journals Nitrogen and Fungicide Applications for the Management of Fungal Blights of Carrot

HortScience ◽  
2014 ◽  
Vol 49 (5) ◽  
pp. 608-614
Author(s):  
Catarina Saude ◽  
Mary Ruth McDonald ◽  
Sean Westerveld
Keyword(s):  
Disease Severity ◽  
Severity Index ◽  
Leaf Blight ◽  
Cercospora Leaf Spot ◽  
Marketable Yield ◽  
Alternaria Dauci ◽  
Leaf Blights ◽  
Mineral Soils ◽  
N Management ◽  
Cercospora Carotae

Alternaria leaf blight (ALB) caused by Alternaria dauci (Kühn) Groves and Skolko and Cercospora leaf spot (CLS) caused by Cercospora carotae (Pass.) Solheim are the major foliar diseases of carrot in Ontario, Canada. In addition to reducing photosynthetic area, the diseases can weaken carrot tops, which can break during mechanical harvesting, reducing harvested yields. Fungicides are commonly used to manage the disease, but there is potential to reduce fungicide applications through nitrogen (N) management. Trials were conducted on mineral soils from 2006 to 2008 to determine the importance of applied N and fungicide applications to control fungal leaf blights of carrot. Three rates of N (0, 110, and 220 kg·ha−1) and 0, 3, or 5 (2006 and 2007) or 6 (2008) fungicide applications were applied. Leaf blight severity was assessed biweekly throughout the season and at harvest. The severity of both ALB and CLS and combined disease severity index at harvest decreased with increasing N and fungicide application. In some cases, disease severity of carrots treated with high N and no fungicides was equivalent to carrots treated with no N and five fungicide sprays. Total and marketable yield increased with increasing number of fungicide sprays in 2006 and 2007, but N application did not affect yield. Results suggest that severity of ALB and CLS can be minimized through a combination of N and fungicide applications, but rates of N higher than 110 kg·ha−1 may reduce marketable yield through a decrease in stand and an increase in oversized roots.

scholarly journals Weather-Based Fungicide Spray Programs for Control of Two Foliar Diseases on Carrot Cultivars Differing in Susceptibility

Plant Disease ◽  
2006 ◽  
Vol 90 (3) ◽  
pp. 358-364 ◽  
Author(s):  
P. M. Rogers ◽  
W. R. Stevenson
Keyword(s):  
Disease Control ◽  
Disease Severity ◽  
Field Experiments ◽  
Host Susceptibility ◽  
Weather Data ◽  
Yield Reduction ◽  
Susceptible Cultivar ◽  
Foliar Diseases ◽  
Industry Standard ◽  
Alternaria Dauci

Foliar diseases of carrot caused by Alternaria dauci and Cercospora carotae occur every year in Wisconsin, requiring repeated foliar fungicide applications to minimize defoliation and yield reduction. Improved timing of fungicide applications combined with the use of disease resistant cultivars offer growers a means to improve disease control with fewer fungicide inputs compared with the current strategy of weekly fungicide applications to a susceptible cultivar. Field experiments in 2002 to 2004 examined fungicide application schedules indicated by a disease forecasting model that calculated the duration of environmental conditions favorable for A. dauci and C. carotae (adaptation of TOM-CAST) on two carrot cultivars differing in susceptibility to these foliar diseases. All fungicide programs were initiated at a 1% disease severity threshold determined by scouting. Intervals for weather-based spray programs were based on in-canopy leaf wetness and temperature data. Fungicide sprays were applied according to 15 and 20 disease severity value (DSV) application thresholds, and were compared with a weekly spray program and an untreated control. Results of this trial demonstrated that fungicide sprays made according to weather data may reduce fungicide inputs in most years compared with current industry-standard, calendar-based spray programs. Host susceptibility affected the efficacy of weather-based spray programs, resulting in longer spray intervals and fewer fungicide applications on the resistant cultivar Bolero when compared with the susceptible cultivar Fontana. Fungicide spray programs based on TOM-CAST diminished fungicide inputs by 30 to 50%, compared with the weekly spray program, by lengthening intervals between applications without compromising disease control or root yield.

scholarly journals Distribution of Baseline Sensitivities to Azoxystrobin Among Isolates of Plasmopara viticola

Plant Disease ◽  
2000 ◽  
Vol 84 (3) ◽  
pp. 275-281 ◽  
Author(s):  
Francis P. Wong ◽  
Wayne F. Wilcox
Keyword(s):  
New York ◽  
Disease Severity ◽  
Disease Incidence ◽  
Leaf Disc ◽  
Plasmopara Viticola ◽  
Grapevine Downy Mildew ◽  
Coefficients Of Variation ◽  
Control Versus ◽  
Strobilurin Fungicide ◽  
Effective Doses

An excised leaf disc assay was developed for determining the sensitivity of isolates of Plasmopara viticola (causal agent of grapevine downy mildew) to the strobilurin fungicide azoxystrobin. Five repeated assays with the same five single-sporangiophore isolates showed that the technique yielded reproducible results; that is, coefficients of variation ranged from 4.0 to 20% (mean 12%) for effective doses for 50% control (ED50 values) based on disease incidence and from 4.4 to 14% (mean 8.1%) for ED50 values based on disease severity. Then, the assay was applied to 81 single-sporangiophore isolates of P. viticola collected from 10 geographically distinct vineyards in western New York, providing a baseline distribution of sensitivities within this population. For disease incidence, individual ED50 values ranged from 0.05 to 0.94 μg/ml (mean 0.40 μg/ml), whereas for disease severity they ranged from 0.04 to 0.78 μg/ml (mean 0.24 μg/ml). When 61 of these isolates were similarly tested at a single discriminatory dose of 0.50 μg/ml, azoxystrobin provided 61% control of disease incidence versus 41 and 1.1% control for trifloxystrobin and kresoximmethyl, respectively; for disease severity (colony diameter), azoxystrobin provided 80% control versus 57 and 1.1% control for trifloxystrobin and kresoximmethyl, respectively. These results provide information that can be utilized in future monitoring of P. viticola resistance to azoxystrobin and indicate differences in the intrinsic activities of the three strobilurin fungicides against this pathogen.

scholarly journals Assessing Taro (Colocasia esculenta (L.) Schott) Leaf Blight Incidence, Severity, and Farmers’ Knowledge of the Disease in Fako Division of Cameroon

2020 ◽  
pp. 17-29
Author(s):  
Mandah Cicelia Takor ◽  
Ekwa Yawa Monono ◽  
Ojong Agbor Ntane ◽  
Jemimah Evenye Ngale ◽  
Lum A. Fontem
Keyword(s):  
Disease Severity ◽  
Disease Incidence ◽  
Management Strategies ◽  
Leaf Blight ◽  
Cultural Methods ◽  
Randomized Design ◽  
High Prevalence ◽  
Severity Of The Disease ◽  
Blight Disease ◽  
Taro Leaf Blight

Taro leaf blight (TLB), a major disease of taro plant caused by Phytophthora colocasiae, a pseudo-fungus, that occurs in many taro producing areas, especially in the South West of Cameroon. A Survey was conducted to assess farmers’ knowledge, as well as to determine the incidence and the severity of the disease in taro fields. Structured questionnaires were administered in selected locations (Bokova, Ekona, Muea, Mile 16, Mutengene, and Likomba) of taro production. Two farms were selected with two quadrats of 64 m2 each were carved to assess disease incidence and severity on taro. The number of plants infected with taro leaf blight were counted and the area of the affected leaves measured was used to evaluate the disease incidence and disease severity. Data collected were subjected to ANOVA for complete randomized design and the means were compared using Tukey test at 0.05 probability levels. The results revealed that most of the farmers could identify the disease while practicing cultural methods in controlling the disease. The results also revealed significant differences (p = 0.001) in disease incidence and disease severity in all the localities, with Mile 16 showing the highest percentage mean of 96.53% and 85.59%, respectively. The severity scored showed high infection range of 3 – 3.95 in all locations except in Likomba (2.60).  It could be concluded from the results that there were high prevalence of taro leaf blight disease in Fako Division. Good management strategies are therefore required to control Taro leaf blight and improve taro production in the area.

scholarly journals Effect of Inoculation of Plant Growth Promoting Rhizobacteria (PGPR) Mix I Formulations on Plant Growth, Yield, Disease Incidence and Disease Severity of Rhizoctonia Leaf Blight of Amaranthus (Amaranthus tricolor L.)

2021 ◽  
Author(s):  
A.R. Resmi ◽  
B. Lovely ◽  
A. Jayapal ◽  
G. Suja ◽  
N. Chitra
Keyword(s):  
Plant Growth ◽  
Disease Severity ◽  
Agricultural Research ◽  
Disease Incidence ◽  
Growth Yield ◽  
Plant Growth Promoting Rhizobacteria ◽  
Leaf Blight ◽  
Research Station ◽  
Plant Growth Promoting ◽  
Growth Promoting

Background: Amaranthus is the most popular and commercially cultivated leafy vegetable in the Southern part of India, especially Tamil Nadu and Kerala which is susceptible to a number of diseases. Among the different diseases affecting amaranth, foliar blight caused by Rhizoctonia solani Kuhn, is considered as the most serious disease in Kerala. Methods: A field experiment was taken up at Onattukara Regional Agricultural Research Station (O.R.A.R.S), Kayamkulam, Alappuzha, Kerala during December 2019 to February 2020 to assess the influence of dust and liquid formulations of Plant Growth Promoting Rhizobacteria (PGPR) mix I on growth, yield and disease incidence (Rhizoctonia leaf blight) in amaranthus. Result: The results of the study reveal that maximum number of leaves, number of branches per plant and yield were produced by the plants that were subjected to seedling root dip with 5% talc formulation followed by drenching with 5% talc solution at 30 DAT and 45 DAT. Regardless of talc or liquid formulation of PGPR mix I (2%) seedling dip followed by drenching at 15, 30 and 45 DAT provided the least disease incidence and disease severity in amaranthus at Onattukara condition. Hence use of PGPR mix I is a prerequisite for effective growth, yield and management of leaf blight of amaranthus at Onattukara.

scholarly journals Prevalence, Incidence, and Severity of Sorghum Diseases in Western Kenya

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 65-70 ◽  
Author(s):  
H. K. Ngugi ◽  
S. B. King ◽  
G. O. Abayo ◽  
Y. V. R. Reddy
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Gaussian Model ◽  
Gray Leaf Spot ◽  
Distribution Functions ◽  
Leaf Blight ◽  
Yield Reduction ◽  
Production Environment ◽  
Head Smut ◽  
Western Kenya

To assess the prevalence and severity of sorghum diseases in western Kenya, a 2-year survey was conducted (July 1995 and 1996), in 91 and 109 farmers' fields, respectively. Fields were generally <0.5 ha and production environment ranged from warm-humid to warm-semi-arid. Fourteen foliar and six panicle diseases were observed, with limited variation in disease prevalence and severity between the 2 years. The most common foliar diseases observed were (in decreasing order of prevalence) oval leaf spot (Ramulispora sorghicola), rust (Puccinia purpurea), ladder leaf spot (Cercospora fusimaculans), zonate leaf spot (Gloeocercospora sorghi), gray leaf spot (Cercospora sorghi), leaf blight (Exserohilum turcicum), and anthracnose (Colletotrichum sublineolum); with prevalence ranging from 95 to 97% of fields for oval leaf spot, and 44 to 65% of fields for anthracnose. Head smut (Sporisorium reilianum), was observed in 73 to 75% of fields, covered kernel smut (S. sorghi) 42 to 43% of fields, and loose smut (S. cruenta) 14 to 24% of fields. Head smut incidence was >25% in 3% of fields surveyed. Grain yield reduction from smut diseases alone was estimated to be 5%. Out of eight probability distribution functions compared, the double Gaussian model best described the frequency of disease severity levels for most diseases. Based on the best-fitting model, the proportion of fields with disease severity level thought to cause yield loss (severity rating >5 on a 1 to 9 scale, where 1 = no disease) was calculated as 26.6% for oval leaf spot, 15.3% for rust, 14.8% for anthracnose, 4.8% for ladder leaf spot, and 1.5% for leaf blight. The production environment influenced the prevalence of disease severity. Severe anthracnose, leaf blight, and ladder leaf spot were confined to fields in the humid LM1 and LM2 agro-ecological zones, rust was ubiquitous, and severe gray leaf spot was more prevalent in the dryer LM4 zone.

scholarly journals Bacterial Leaf Blight (BLB) Disease Incidence and Severity in Basmati and Non-Basmati Rice Growing Areas of Punjab, Pakistan

2020 ◽  
Vol 9 (3) ◽  
pp. 157-163
Author(s):  
Hafiz M. I. Arshad ◽  
Junaid A. Khan ◽  
Kamran Saleem ◽  
Syed S. Alam ◽  
Shahbaz T. Sahi
Keyword(s):  
Leaf Area ◽  
Disease Severity ◽  
Disease Incidence ◽  
Management Strategies ◽  
Leaf Blight ◽  
Bacterial Leaf Blight ◽  
Basmati Rice ◽  
Rice Varieties ◽  
Disease Symptoms ◽  
Rice Season

Bacterial leaf blight (BLB) is one of the most damaging diseases of rice in Asia and annually incurring significant yield loss to rice production in Pakistan. Management of disease required the information of BLB incidence and severity in basmati and non-basmati rice areas. The current study presented the observation of BLB disease incidence and severity in 19 major rice growing districts of Punjab. In this study, 9 Basmati growing and 10 non-basmati rice growing districts were surveyed from September to October in 2009, 2010, 2012, and 2013. Rice fields near to roadside, research stations and adjoining farmer fields were preferred for the survey. Each halt was after 10 km on the route depending upon the crop intensity. The general appearance of the field was observed for the absence or presence of BLB disease symptoms. The incidence of BLB was recorded as a percentage of plants infected in a field on a visual basis. For each field, 4 plants were observed at 5 points/hill along the diagonal transect for disease symptoms. The data of severity was recorded as the percentage of leaf area infected out of the total leaf area. Among the districts with basmati rice, the mean incidence of BLB was maximum in Gujranwala, Sheikhupura and Hafizabad followed by Mandi Bahauddin and Gujrat. A similar pattern of disease severity was observed in the basmati rice belt with maximum BLB mean severity in Gujranwala, Sheikhupura and Hafizabad having most of the field with a severity scale of 9. Overall, the disease trend showed that both the incidence and the severity were higher in 2010, 2012 and 2013 in the basmati rice belt. The ten districts, comprising of mostly non-basmati rice varieties showed relatively less BLB incidence and severity compared to basmati rice districts. The maximum mean incidence of 20-25% was observed in Faisalabad, Chiniot and Sahiwal in at least one year of the rice season. None of the field with BLB disease symptoms was observed in districts Okara, Khanewal and Bahawalpur during the 2012 and 2013 rice season. Maximum disease severity of mean value 3 was observed in Sahiwal during 2009 while the rest of the districts showed less than 2 mean severity during all rice growing season. Overall, in non-basmati rice districts, no specific trend of disease incidence and severity was apparent, however, the disease was present in very low magnitude or absent during the surveyed years. The information from this study is helpful in the selection of variety for basmati and non-basmati districts of Punjab and the adoption of appropriate disease management strategies.

scholarly journals Association of common bacterial blight (Xanthomonas axonopodis pv. phaseoli) epidemics with agro ecological factors in Southwestern Ethiopia

2021 ◽  
Vol 11 (1) ◽  
pp. 74-83
Author(s):  
W Adila ◽  
H Terefe ◽  
A Bekele
Keyword(s):  
Common Bean ◽  
Disease Severity ◽  
Crop Rotation ◽  
Weed Management ◽  
Bacterial Blight ◽  
Disease Incidence ◽  
Ecological Factors ◽  
Common Bacterial Blight ◽  
Xanthomonas Axonopodis ◽  
Southwestern Ethiopia

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli, is an economically important disease of common bean and causes significant yield losses in Ethiopia. A field survey was conducted to understand the spatial distribution, relative importance and association of common bacterial blight epidemics with agro-ecological factors in low and mid-land areas of Southwestern, Ethiopia, during the 2018-19 cropping season. A total 85 bean fields were assessed in four common bean growing districts. High diseases incidence and severity was recorded at Debub Ari (77.6 and 52.7%, respectively) while the lowest was from Male (38.5 and 28.0%, respectively). The associations between disease parameters and agro-ecological factors were analyzed using multiple logistic regression models. Agronomic practices including NPS fertilization, preceding crop, weed management and plant population had highly significant (P<0.0001) association with both disease incidence and severity. Also, altitude, seed source and cropping system significantly (P<0.05) influenced disease severity while cropping pattern showed significant (P<0.05) association with disease incidence in the reduced model. Higher mean disease severity (≥40%) had high probability of association with district, absence of NPS fertilization, poor weed management practice, and preceding crops, than their counter parts. Adequate NPS fertilization increases growth performance of the crop in turn decreases disease intensity, weed serve as alternate host for incoming inoculum and previous crops were source for inocula as well as crop rotation used as reduce inoculum load. Therefore, the present study showed that the disease is a major production constraint of common bean, and suggested proper nutrient and weed management practices, and crop rotation to reduce common bacterial blight in the study areas. Int. J. Agril. Res. Innov. Tech. 11(1): 74-83, June 2021

scholarly journals Managing Foliar Diseases of Processing Sweet Corn in New York with Strobilurin Fungicides

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 213-220 ◽  
Author(s):  
D. A. Shah ◽  
H. R. Dillard
Keyword(s):  
New York ◽  
Disease Severity ◽  
Sweet Corn ◽  
Cost Effective ◽  
Field Trials ◽  
Leaf Blight ◽  
Foliar Disease ◽  
Northern Corn Leaf Blight ◽  
Strobilurin Fungicides ◽  
Corn Leaf Blight

Processing sweet corn (Zea mays) growers in New York are more concerned about the cost effectiveness of fungicide use against foliar fungal diseases (common rust and Northern corn leaf blight) and less about whether such sprays will reduce disease intensity. To address this concern, field trials were done in 2006 and 2007 with three processing sweet corn hybrids (Jubilee, Bold, and GH 9597) that differed in susceptibility to common rust and Northern corn leaf blight, and two strobilurin fungicides (azoxystrobin and pyraclostrobin). Single strobilurin applications were applied in response to foliar disease severity thresholds of 1, 10, and 20%. Single fungicide applications did reduce foliar disease severities. Applications were most cost effective when made in response to the 1 and 10% foliar severity thresholds, and generally only in the susceptible hybrid Bold. Spraying at the 20% severity threshold did reduce final foliar disease severity but was not cost effective. Azoxystrobin and pyraclostrobin were equally effective in disease management. The results suggest that a single application of a strobilurin fungicide against common rust and Northern corn leaf blight can be cost effective for New York processing sweet corn growers when such an application is made before foliar disease severity exceeds 20%.

scholarly journals Effect Of NPK On The Incidence Of Alternaria Leaf Blight Of Mustard

1970 ◽  
Vol 36 (3) ◽  
pp. 407-413 ◽  
Author(s):  
F Khatun ◽  
MS Alam ◽  
MA Hossain ◽  
S Alam ◽  
PK Malaker
Keyword(s):  
Field Study ◽  
Disease Severity ◽  
Seed Yield ◽  
Nutrient Management ◽  
Disease Incidence ◽  
Leaf Blight ◽  
Recommended Dose ◽  
Soil Test ◽  
Alternaria Leaf Blight ◽  
Macro Nutrients

A 2-year field study was carried out to find out the effect of three macro nutrients NPK on the severity of Alternaria leaf blight and yield of mustard. Nitrogen @ 80, 100, 120, 140, and 160, phosphorus @ 15, 30, and 45, and potassium @ 30, 60, and 90 kg/ha were applied. Among the nutrients, 120-30- 60 kg NPK/ha was considered as recommended dose on the basis of soil test. Fertilizer dose 120-30-90 kg/ha appeared to be the best combination of N, P, and K in reducing the disease incidence and to increase seed yield of mustard. Higher dose of K (90 kg/ha) decreased the incidence of Alternaria leaf blight but higher dose of nitrogen (140 and 160 kg N/ha) increased the disease incidence. The highest seed yield of 1718 kg/ha was obtained with 120-30-90 kg of NPK/ha which was statistically similar to the doses of 120-30-60 and 120-45- 60 kg of NPK/ha. Higher seed yield and lower disease severity was also observed under these three treatments as compared to other treatments. Keywords: Mustard; Alternaria leaf blight; nutrient management. DOI: http://dx.doi.org/10.3329/bjar.v36i3.9269 BJAR 2011; 36(3): 407-413

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