Rhizopus oryzae as a causal agent of a head rot of sunflowers in Queensland

The causal agent of a common head rot of sunflowers in Queensland was isolated and identified as Rhizopus oryzae. Field experiments were conducted to investigate the environmental and host conditions suitable for disease development, and control of the disease by the use of fungicides. The disease occurs in wound inoculated plants when atmospheric humidity is high. Dicloran is capable of restricting established infection, but wound inoculations made after the application of the fungicide avoid the protective barrier and are uninfluenced by it. The possible use of chemicals to control the disease is discussed.

Download Full-text

Rhizopus Head Rot of Confectionery Sunflower: Effects on Yield Quantity and Quality and Implications for Disease Management

Phytopathology ◽

10.1094/phyto.1997.87.12.1226 ◽

1997 ◽

Vol 87 (12) ◽

pp. 1226-1232 ◽

Cited By ~ 13

Author(s):

D. Shtienberg

Keyword(s):

Growth Stage ◽

Field Experiments ◽

Rhizopus Oryzae ◽

Development Stage ◽

Crop Growth ◽

Growth Stages ◽

Yield Quality ◽

Crop Growth Stage ◽

Head Rot ◽

The Individual

The effects of Rhizopus head rot, caused by Rhizopus oryzae, on the yield of confectionery sunflower and its quality were studied in field experiments conducted from 1994 to 1996. The extent of yield loss was related to the crop growth stage at inoculation. When heads were inoculated at the budding stage, loss was not apparent, because inoculated heads were not infected. When inoculated at the anthesis stage, loss was relatively high (42.5 to 99.1%), and both the number of achenes per head and the individual achene weight were reduced. When heads were inoculated at the seed development stage, yield was not reduced significantly (although the entire receptacle was rotted). Effects of Rhizopus head rot on measures of yield quality were examined as well. Inoculation with R. oryzae did not affect the size of the achenes at any crop growth stage. In contrast, the incidence of discolored achenes (an external sign of nutmeats with a bitter off-flavor) was affected by the disease at all crop growth stages. A survey in eight commercial fields from 1992 to 1996 found that, by the end of the season, incidence of disease ranged from 2.3 to 17.4%. However, since disease intensified late, resultant yield losses were minor and did not exceed 3.1%. Loss figures were estimated by means of a model that was developed and validated in the field experiments. The disease did affect the incidence of discolored achenes. Thus, the conclusion drawn is that the effects of Rhizopus head rot in confectionery sunflower on crop yield is of minimal concern, at least when disease intensifies late, as was the case in the studied fields, but management of the disease should be considered in some situations. The objectives would be to prevent a reduction in yield quality, not yield quantity.

Download Full-text

Pestalotia Leaf Spot and Fruit Rot of Strawberry

EDIS ◽

10.32473/edis-pp357-2020 ◽

2020 ◽

Vol 2020 (5) ◽

Author(s):

Juliana S. Baggio ◽

Natalia A. Peres

Keyword(s):

Plant Pathology ◽

Leaf Spot ◽

Fruit Production ◽

Causal Agent ◽

Fruit Rot ◽

Disease Development ◽

Plant Parts ◽

Pathology Department ◽

And Control

Pestalotiopsis-like fungi cause diseases on many different species of plants worldwide, including strawberry. The pathogen is not necessarily new to strawberry and was first reported causing fruit rot in Florida and Israel in the 1970s. However, during the 2018–19 and 2019–20 strawberry seasons, severe and unprecedented outbreaks were reported in Florida, characterized by symptoms on nearly all plant parts including roots, crowns, petioles, fruit, and leaves. This new 4-page publication of the UF/IFAS Plant Pathology Department describes the disease and its causal agent and briefly covers what is known about disease development and control practices. This document will provide valuable information to strawberry nursery and fruit production growers. Written by Juliana S. Baggio and Natalia A. Peres.https://edis.ifas.ufl.edu/pp357

Download Full-text

Rhizopus oryzae Associated with Melanagromyza splendida and Stem Disease of Sunflowers (Helianthus annuus) in California

Plant Health Progress ◽

10.1094/php-rs-14-0042 ◽

2015 ◽

Vol 16 (1) ◽

pp. 39-42 ◽

Cited By ~ 3

Author(s):

Febina M. Mathew ◽

Jarrad R. Prasifka ◽

Stephen D. Gaimari ◽

Li Shi ◽

Samuel G. Markell ◽

...

Keyword(s):

Helianthus Annuus ◽

Seed Production ◽

Geographic Distribution ◽

Sunflower Seed ◽

Rhizopus Oryzae ◽

Causal Agent ◽

Parental Line ◽

Disease Symptoms ◽

Stem Infection ◽

Head Rot

In September 2012, a female parental line in a Yolo Co., California, sunflower seed-production field began displaying external stem symptoms that could not be attributed to any known disease. Symptoms appeared to be associated with tunneling caused by an unidentified insect. Stems were collected, and Rhizopus oryzae (causal agent of Rhizopus head rot) and a minute fly, Melanagromyza splendida, were identified as the causal agent and associated insect, respectively. Further, R. oryzae was isolated from intact fly puparia. All commercial hybrids evaluated in the greenhouse were susceptible to stem infection by R. oryzae isolates. Yield implications and geographic distribution of this novel stem disease are unknown. This is the first report of R. oryzae causing stem disease in sunflowers, and of its association with M. splendida. Accepted for publication 10 January 2015. Published 25 March 2015.

Download Full-text

Molecular Tracking and Remote Sensing to Evaluate New Chemical Treatments Against the Maize Late Wilt Disease Causal Agent, Magnaporthiopsis maydis

Journal of Fungi ◽

10.3390/jof6020054 ◽

2020 ◽

Vol 6 (2) ◽

pp. 54 ◽

Cited By ~ 1

Author(s):

Ofir Degani ◽

Shlomit Dor ◽

Assaf Chen ◽

Valerie Orlov-Levin ◽

Avital Stolov-Yosef ◽

...

Keyword(s):

Field Experiments ◽

Causal Agent ◽

Disease Symptoms ◽

Chemical Treatments ◽

Highly Sensitive ◽

Fungicide Mixtures ◽

Pcr Method ◽

Pathogen Dna ◽

Molecular Tracking ◽

And Control

Late wilt is a destructive disease of corn: outbreaks occur at the advanced growth stage and lead to severe dehydration of susceptible hybrids. The disease’s causal agent is the fungus Magnaporthiopsis maydis, whose spread relies on infested soils, seeds, and several alternative hosts. The current study aimed at advancing our understanding of the nature of this plant disease and revealing new ways to monitor and control it. Two field experiments were conducted in a heavily infested area in northern Israel seeded with highly sensitive corn hybrid. The first experiment aimed at inspecting the Azoxystrobin (AS) fungicide applied by spraying during and after the land tillage. Unexpectedly, the disease symptoms in this field were minor and yields were high. Nevertheless, up to 100% presence of the pathogen within the plant’s tissues was measured using the quantitative real-time PCR method. The highest AS concentration tested was the most effective treatment, and resulted in a 6% increase in cob yield and a 4% increase in A-class yield. In the second experiment conducted in the following summer of the same year in a nearby field, the disease outbreak was dramatically higher, with about 350 times higher levels of the pathogen DNA in the untreated plots’ plants. In this field, fungicide mixtures were applied using a dripline assigned for two coupling rows. The most successful treatment was AS and the Difenoconazole mixture, in which the number of infected plants decreased by 79%, and a 116% increase in crop yield was observed, along with a 41% increase in crop quality. Evaluation of the effectiveness of the treatments on the plants’ health using a remote, thermal infra-red sensitive camera supported the results and proved to be an essential research tool.

Download Full-text

Colletotrichum crown rot (anthracnose crown rot) of strawberries

EDIS ◽

10.32473/edis-pp156-2007 ◽

2007 ◽

Vol 2007 (18) ◽

Author(s):

Steven MacKenzie ◽

Natalia Peres

Keyword(s):

Plant Pathology ◽

Causal Agent ◽

Crown Rot ◽

Disease Development ◽

Production Region ◽

Fact Sheet ◽

Serious Disease ◽

And Control

PP-238, a 3-page illustrated fact sheet by Steven MacKenzie and Natalia Peres, describes this serious disease of strawberries in warm production region, its causal agent and symptoms, disease development and spread, and control. Includes a table of products labeled for control of colletotrichum crown rot. Published by the UF Department of Plant Pathology, June 2007. PP 238/PP156: Colletotrichum Crown Rot (Anthracnose Crown Rot) of Strawberries (ufl.edu)

Download Full-text

Field and Greenhouse Procedures to Evaluate Onions for Botrytis Leaf Blight Resistance

HortScience ◽

10.21273/hortsci.31.3.436 ◽

1996 ◽

Vol 31 (3) ◽

pp. 436-438 ◽

Cited By ~ 3

Author(s):

Thomas W. Walters ◽

LeRoy A. Ellerbrock ◽

Jan J. van der Heide ◽

James W. Lorbeer ◽

David P. LoParco

Keyword(s):

Field Experiments ◽

Leaf Blight ◽

Causal Agent ◽

Blight Resistance ◽

Disease Development ◽

Field Methods ◽

Botrytis Squamosa ◽

Colony Forming Units ◽

Mycelial Fragment ◽

Experimental Plots

Greenhouse and field methods were developed to screen Allium spp. for resistance to botrytis leaf blight (causal agent Botrytis squamosa Walker). In greenhouse evaluations, plants were sprayed with laboratory-grown mycelial fragment inoculum and were incubated at 20C in a chamber with an atomizing fogger. For field inoculations, a portable fog system with windbreaks was erected around experimental plots, and the plants were sprayed with the inoculum on evenings when windless, temperate (18 to 22C) conditions were forecasted. The most effective mycelial fragment inoculum was <21 days old and had ≈45 to 50 colony-forming units/μl, resulting in an absorbance at 450 nm of 0.2 to 0.3. Rubbing the wax cuticle from leaves was essential to disease development in greenhouse but not in field experiments. Evaluations of eight Allium species, including 55 A. cepa L. accessions, were in agreement with previous studies.

Download Full-text

Charcoal Rot of Strawberries Caused by Macrophomina phaseolina

EDIS ◽

10.32473/edis-pp161-2007 ◽

2007 ◽

Vol 2007 (20) ◽

Author(s):

Natalia A. Peres ◽

James C. Mertely

Keyword(s):

Plant Pathology ◽

Macrophomina Phaseolina ◽

Causal Agent ◽

Crown Rot ◽

Disease Development ◽

Charcoal Rot ◽

Fact Sheet ◽

Rot Disease ◽

And Control

PP 242, a 2-page illustrated fact sheet by N.A. Peres and James C. Mertely, describes this new crown-rot disease in Florida -- causal agent and symptoms, disease development and spread, and control. Published by the UF Department of Plant Pathology, November 2007. PP242/PP161: Charcoal Rot of Strawberries Caused by Macrophomina phaseolina (ufl.edu)

Download Full-text

EPIDEMIOLOGY AND CONTROL OF A SUNFLOWER HEAD ROT IN ISRAEL CAUSED BY RHIZOPUS ARRHIZUS

Canadian Journal of Plant Science ◽

10.4141/cjps70-053 ◽

1970 ◽

Vol 50 (3) ◽

pp. 283-288 ◽

Cited By ~ 5

Author(s):

M. ARNAN ◽

M. J. PINTHUS ◽

R. G. KENNETH

Keyword(s):

Helianthus Annuus ◽

Soft Rot ◽

Causal Agent ◽

Rhizopus Arrhizus ◽

Single Application ◽

Helianthus Annuus L ◽

Head Rot ◽

And Control

Injury of the heads was found to be necessary for the infection of sunflower (Helianthus annuus L.) by Rhizopus arrhizus Fischer, identified as the causal agent of a soft rot. Infection did not take place before flowering. Birds visiting the heads in search of seed were implicated in the spread of the disease. The disease was controlled by a single application of Copper 8-quinolinolate.

Download Full-text