Diseases

Plumeria Today > Plumeria Care > Diseases

Mildew

Mildew is also known as ‘downy mildew’ and as the disease spreads, the leaves curl up, necrotize and eventually fall off. The parts of the mycelium that contain the spores of the fungus emerge through the stomata of the plant. In good light it can readily be identified by the gray or purple felt like covering on the back of the leaves.

About mildew

  • What is mildew?
    • The term mildew refers to a group of phytopathogenic fungi that causes diseases in plants.
  • What can you see?
    • In general, mildew is found on the upper side of the leaf, but there are exceptions. One type of mildew only grows on the underside of the leaf. The leaf looks as if it has been dusted with powder.
  • What can you do?
    • Keep humidity low and keep your growing area clean.

About powdery mildew

Powdery mildew is also known as Oidium. Before any symptoms become visible the leaf starts to develop blister-like patches, which is followed by the characteristic white powder where the blister was. The leaf looks as if it has been dusted with powder. In general, mildew is found on the upper side of the leaf, but there are exceptions. One type of mildew only grows on the underside of the leaf, so it’s no surprise that this often gets overlooked. However, as the disease advances, the leaves can end up being completely covered in this white layer and it can even colonize the fruits, with subsequent losses in crop size and quality.

How to prevent the disease?

The best treatment against these types of fungi is prevention; once they have set in and developed, they are very difficult to eradicate, sometimes even with chemical fungicides. Try to prevent spores coming in from elsewhere and contaminating your plants by keeping your growing area clean. You can do this by using only clean equipment and washing your hands thoroughly before entering.

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Identification

How To Identify Powdery Mildew Damage

  • Plants infected with powdery mildew look as if they have been dusted with flour.
  • Powdery mildew usually starts off as circular, powdery white spots, which can appear on leaves, stems, and sometimes fruit.
  • Powdery mildew usually covers the upper part of the leaves and affects the older leaves first; the leaves turn yellow and dry out.
  • The fungus might cause some leaves to twist, break, or become distorted.
  • The white spots of powdery mildew will spread to cover most of the leaves or affected areas.
  • The leaves, buds, and growing tips will become distorted as well. These symptoms usually appear late in the growing season. 

Control and Prevention

How To Control Powdery Mildew 

  • Rubbing the infected leaves together can help partially remove the disease from your plants.
  • Remove all the infected plant parts and destroy them. Remember, do not compost any infected plant, as the disease can still be spread by the wind.
  • Spray infected plants with fungicides. Effective fungicides for powdery mildew treatments or cures include sulfur, lime-sulfur, neem oil, and potassium bicarbonate.

How To Prevent Powdery Mildew

  • Choose plants that are resistant or tolerant to powdery mildew.
  • Powdery mildew thrives in hot and humid weather, so avoid overhead watering to reduce humidity. Also selectively prune overcrowded areas to increase air circulation; this also helps reduce humidity for your plants.
  • Spray your plants with fungicides according to their directions. If you don’t want to use fungicides, try spraying your plants with a solution of 1 teaspoon baking soda in 1 quart of water. Remember to spray your plants thoroughly.

Plumeria that grow in crowded, humid or shaded conditions are susceptible to powdery mildew, a form of mold. Powdery mildew is a common fungal disease that affects many types of plants, from squash to plumerias. The signature symptom of powdery mildew is white or gray powdery spots on the upper sides of plumeria leaves. The spots sometimes appears on flowers, buds, the undersides of leaves and new shoots. As the infection progresses, the leaves turn yellow, become distorted and drop off prematurely, and flower buds fail to open. The fungus overwinters in brown or black fruiting bodies.

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Black Tip Fungus

black-tip-fungus-plumeria-3-294x300The fungus known as black tip occurs after the plumeria crowns have been exposed to frost or sometimes just cold winter morning dew. The healthier and larger the frangipani, the more resistant it will be to black tip damage. Some fungicides treat it better than others but it can be treated. If the black tip is severe, the tip will die and new shoots will grow from the sides of the branch, creating branches. When you see new shoots growing from the side of the plant, you should cut off the dead tip with a clean cut. Sometimes, rot can start in a damaged tip.

  • In early spring,at the first signs of new growth, a bacterial problem commonly known as “black tip” can appear. This causes die back of the new growth but creates more branches.
  • “Black tip” rarely kills the tree.
  • The cause of the “black tip” fungus is low spring temperatures combined with high humidity.  By late spring when temperatures increase the “black tip” disappears.
  • To try and reduce its unsightly appearance seaweed extract liquid fertilizers can help. Begin foliar spraying at the first signs of new growth prior to the first signs of the “black tip” fungus and then spray once a week until early summer.
  • Using hydrogen peroxide has been know to minimize the damage.

Black Tip Fungus is very hard to control once it gets a big head start.  Black Tip can pop up at any time of the year.  Black Tip Fungus loves cool, wet, and shady areas.  When the conditions are right is can pop up virtually overnight, and spread like wildfire.

Black sooty mold forms a black mold on plumeria leaves. You’ll know if the black tip fungus has attacked your plumeria tree if you see black tips on the branches’ growing tips in spring. Affected branches will stop growing. If you catch this fungal disease soon after it first appears, you’ll have success in halting its spread. Spray the tree with an approved fungicide as soon as possible, and also cut affected branches back to disease-free wood.

If left uncontrolled it will kill the growth tips of mature trees, and kill entirely a small plumeria.   If Black Tip has killed the growth tips on a mature plumeria and temperatures warm up, the black tip will die off.  Then the blacked tips will callus and break off.  Next, the plumeria will branch back out as if it was pruned.  Sometime on a tree it’s not all bad, because it gets a ton of new branches, but if it happens every year, or disgustingly, twice a year you will have hell getting you plumerias to bloom. 

You can help control it by controlling ants, which bring aphids and scale to your tree and feed on their sticky excretion. If you smear a think (1/2 inch) layer of a product called Tree Tanglefoot around the base of your plumeria tree, ants will be unable to pass over it. Black sooty mold can also result from exposure to whiteflies and thrips: control these pests with yellow sticky traps and insecticidal soap spray. If necessary, spray your tree with a broad spectrum fungicide.

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Plumeria Rust

Rust Fungus is caused by Coleosporium dominguense and Coleosporium plumeriae 

In general, however and given rust is rather specific in its host range.  Many rust have several kinds of microscopic spores.

The plumeria cultivars most susceptible to this fungus are the Plumeria rubra types and the Plumeria obtusa. This fungus manifests itself as red-orange pustules on the backsides of leaves. It presence can always be determined be the appearance of yellow, orange or reddish-brown powdery pustules on the leaves, stems, or buds of the infected plant. The spores produced in these pustules are carried by splashing rain or air currents to near-by healthy plants where new infections will occur. Your first line of attack should be to cut off affected leaves. Do not add them to a compost pile because the disease can spread. The Plumeria Society of America recommends using a broad spectrum fungicide—those products containing bayleton, benomyl or oxycarboxin are appropriate. Cutting down tall weeds around plumeria trees helps to improve air circulation and will reduce the humidity this pathogen needs to survive. Also, when you plant plumeria trees, be sure to leave plenty of space between trees.

Rust Fungus does not kill Plumeria, but can rapidly de-foliate an entire tree.

Most plumeria cultivars grown are susceptible to the pathogen and have numerous powdery spore masses on the underside of leaves. Leaves can turn brown and fall from the plant as early as two months after the springtime flush of new leaves is infected by the fungus.

How to Control Rust Fungus

  • Keep the growing area clean and free of fallen leaves.
  • Carefully remove and place infected leaves into trash bags.
  • Mild outbreaks can be controlled by fungicides such as GreenLight “Fung-Away” spray.
  • The only proven chemical to control rust is products containing Bayleton. Bayer Bayleton 50 fungicide and Strike 50 are two products know to help control rust.
  • To best control rust, you will need to setup a regular  regiment and treat the entire infected area. 
Rust fungus will over-winter on infected plants.   


Additional Ideas for Controlling Rust Fungus

Plumeria trees in sunny, well-ventilated locations are less susceptible to mold infections. Fungicides, including mycobutanil, control plumeria rust, according to the University of Hawaii at Manoa Cooperative Extension. Dispose of fallen rust-infected leaves, and spray the ground under the tree in the winter. Apply copper fungicide, neem oil or horticultural oils during early stages of powdery mildew infection, and remove any diseased leaves and stems. To prevent sooty mold, inspect stems and the undersides of leaves for insects, and remove the insects by hand or with insecticidal soap or a forceful stream of water. Carefully follow pesticide label directions and precautions.

Additional reading form University of Hawaii  pd-61-1

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Sooty Mold

Sooty mold is actually a symptom of an aphid, whitefly or thrip infestation. These tiny insects feed on plumeria leaf and stem juices and secrete a sticky, sugary liquid called honeydew. Clusters of the insects may be visible on the undersides of infested leaves. Black sooty mold grows in the honeydew on plumeria leaves and stems. The mold can interfere with photosynthesis as it coats the leaves, and can cause stunted growth and reduced plant vigor.

Control

Plumeria trees in sunny, well-ventilated locations are less susceptible to mold infections. Fungicides, including mycobutanil, control plumeria rust, according to the University of Hawaii at Manoa Cooperative Extension. Dispose of fallen rust-infected leaves, and spray the ground under the tree in the winter. Apply copper fungicide, neem oil or horticultural oils during early stages of powdery mildew infection, and remove any diseased leaves and stems. To prevent sooty mold, inspect stems and the undersides of leaves for insects, and remove the insects by hand or with insecticidal soap or a forceful stream of water. Carefully follow pesticide label directions and precautions.

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(FMV) Virus-causing color break in Plumerias

(FMV) Virus-causing color break in Plumerias

Based upon visual observation of infected plumeria plants from various places for a number of years, it seems that Frangipani Mosaic Virus (FMV) has a minimal effect on the growth and the health of most plumerias with the exception of severe cases in a few cultivars. Its symptoms may include, e.g., leaf malformation, mottled leaf, and/or splash or color break (CB), especially on the petals. Some plumeria trees appear normal with only an occasional CB on the petals, which is attractive to some people.

From my point of view, however, the color break is unacceptable since it distorts the original colors of flowers. In addition, unlike other diseases, it is incurable, and the virus that resides in the infected plant may accidentally spread to other plumeria trees somehow, and finally, the whole collection may all be infected.

According to ICTVdb, the FMV transmitted by mechanical inoculation not involving a vector. 

Suggested reading related to Frangipani Mosaic Virus: click…DPVWeb or 
https://www.ncbi.nlm.nih.gov/pubmed/26239043

Characterisation and diagnosis of frangipani mosaic virus from India.

Author(s) : Alok Kumar; Vikas Solanki; Verma, H. N.; Bikash Mandal

Author Affiliation : Advanced Centre for Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi, 110 012, India.

Author Email : leafcurl@rediffmail.com

Journal article : Virus Genes 2015 Vol.51 No.2 pp.310-314 ref.14

Abstract : Frangipani mosaic virus (FrMV) is known to infect frangipani tree (Plumeria rubra f. acutifolia) in India but the virus has not been characterized at genomic level and diagnosis is not available. In the present study, an isolate of FrMV (FrMV-Ind-1) showing greenish mosaic and vein-banding symptoms in P. rubra f. acutifolia in New Delhi was characterized based on host reactions, serology and genome sequence. The virus isolate induced local symptoms on several new experimental host species: Capsicum annuum(chilli), Nicotiana benthamiana, Solanum lycopersicum and S. melongena. N. benthamianacould be used as an efficient propagation host as it developed systemic mottle mosaic symptoms all round the year. The genome of FrMV-Ind-1 was 6643 (JN555602) nucleotides long with genome organization similar to tobamoviruses. The Indian isolate of FrMV shared a very close genome sequence identity (98.3%) with the lone isolate of FrMV-P from Australia. FrMV-Ind-1 together with FrMV-P formed a new phylogenetic group i.e. Apocynaceae-infecting tobamovirus. The polyclonal antiserum generated through the purified virus preparation was successfully utilized to detect the virus in field samples of frangipani by ELISA. Of the eight different tobamoviruses tested, FrMV-Ind-1 shared distant serological relationships with only cucumber green mottle mosaic virus, tobacco mosaic virus, bell pepper mottle virus and kyuri green mottle mosaic virus. RT-PCR based on coat protein gene primer successfully detected the virus in frangipani plants. This study is the first comprehensive description of FrMV occurring in India.

ISSN : 0920-8569

DOI : 10.1007/s11262-015-1228-3

URL : http://link.springer.com/article/10.1…

Record Number : 20153349035

Publisher : Springer

Location of publication : Dordrecht

Country of publication : Netherlands

Language of text : English

Language of summary : English

How to Avoid FMV Virus in Plumerias

Note: There is no effective treatment for FMV transmitted by mechanical inoculation not involving a vector.

Viral-contaminated cutting tools used in grafting and pruning are likely the most common means of FMV transmission. Unfortunately, it is how this particular virus spreads rapidly and covertly in plumerias, especially in Thailand

Nowadays, symptoms are commonly seen in plumerias which are sold in the markets everywhere. Some virused plumerias may look normal, but the symptoms generally appear in a later stage. Thus it is important to address this issue to increase growers’ awareness, to keep the virus under control, and to save all great plumeria cultivars from being infected. 

Follow these Practices to prevent the spread of FMV

1. In an attempt to keep the whole plumeria collection virus-free, newly acquired plumerias should be isolated over a period of time to observe or check (test) for the presence of virus.

2.  All FMV-infected plants should be separated from the rest of collection and/or destroyed.

3.  Using a sterilized cutting tool is also the key to preventing the spread of the FMV, which may be present in the plumeria trees growing in the garden, to the rest of the collection.

4.  My routine practice of pruning plumerias in the garden is to carry as many sterilized knives as possible with me and use only one knife per plumeria plant. They are then sterilized in boiling water for further use.

5. Plumerias with the virus should not be allowed to be registered as a new cultivar based upon its appearance of the flowers with the color break. It is just a diseased plant, not an innovative one.

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Stem Rot

Stem Rot is a disease that causes the decaying of the inner layers of the Plumeria. The plumeria stem becomes soft and squishy as the inside rots away.  Stem rot moves very quickly and is almost always fatal to cuttings. Stem Rot usually occurs while trying to root cuttings or during winter storage.

Cool temperatures and wet soil contribute to Stem Rot.  Rooting cuttings and newly rooted plumerias are at highest risk for developing stem rot.

Stem rot officially is a disease caused by a fungus infection in the stem. Fungus that causes stem rot are Rhizoctonia, Fusarium and Pythium. Stem rot can readily infect crops that are in their vegetative or flowering stages. The disease can survive up to five years in the soil. Symptoms of stem rot includes staining of infected area, reduced crop yield and crop failure.

  • The disease can be spread through the use of unfiltered water as well as unsterilized tools.
  • Also leaving previous dead roots in soil can increase the risk of stem rot. Spores can also enter the plant through injured stem tissue on the plant including from insect attacks. The fungus impedes stem functions like transporting nutrients. It can cause water to leak through the lesions of stem tissue.
  • An issue with maintaining this disease is the lack of management by crop producers. Producers of plumeria tend to not manage for the disease because it normally results in the loosing of the affected cuttings or newly rooting plants.
  • Fungicides can be used to manage the disease as well as burning the crop after harvest or letting it decompose.

What it does

Stem rot leads to formation of lesions and production of chalky grains and unfilled panicles.

Why and where it occurs

The infection bodies or sclerotia are found in the upper soil layer. They survive in air-dry soil, buried in moist soil, and in tap water. They can also survive on straw, which is buried in the soil. 

Infection is high on plants with wounds as a result of taking cutting with infected tools or rooting cuttings with infected soil. The panicle moisture content and nitrogen fertilizer also influence disease development.

How to identify?

Check the plant for the following symptoms:

Infected stem rots

  • visible numerous tiny white and black sclerotia and mycelium inside the infected culms
  • infected culm lodges and caused unfilled panicles and chalky grain
  • The stem becomes soft or mushy.
  • Initial symptoms are small, irregular black lesions on the outer leaf sheath near water level. Lesions expand as the disease advances.

Why is it important?

The infection is seen on the rice crop during early heading and grain filling. The leaf sheaths decay and cause lodging and lower grain filling. It can cause heavy losses in many countries.

For example, in Japan, there are 51,000−122,000 hectares infected and estimated annual losses of 16,000−35,000 due to this disease. In Vietnam, the Philippines, and India, losses from 30% to 80% were recorded.

How to manage?

  • Burn straw and stubble or any crop residue after harvest or let the straw decompose.
  • Drain the field to reduce sclerotia.
  • Balance the use of fertilizer or perform split application with high potash and lime to increase soil pH.
  • Chemicals such as fentin hydroxide sprayed at the mid-tillering stage, thiophanate-methyl sprayed at the time of disease initiation can reduce stem rot incidence in the rice field.
  • Other fungicides such as Ferimzone and validamycin A also show effectivity against the fungus.
  • Do not reuse soil know to to have had infected plants.
  • Root only in fresh sterilized soil.

Once a Plumeria has survived it’s first winter, Stem Rot is usually not a problem.

Plumeria Cuttings:  Infected cuttings typically fail to root. Instead they develop rot that gradually moves up the stem. Leaf wilt and leaf spotting may be evident. The rotted stem eventually becomes shriveled, turns dull dark brown to black in color, and falls over in its pot.

Mature Plumerias:  Although rare,  mature plants can lose a branch or two from stem rot and/or freeze damage.  Freeze damage looks almost the same as Stem Rot.  In either case, with mature plumeria just cut off the affected areas and a mature plumeria will bounce right back with new branches and leaves.

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Plumeria – Frangipani mosaic virus


196
August 1978		 Family: Virgaviridae
Genus: Tobamovirus
Species: Frangipani mosaic virus
Acronym: FrMV

Frangipani mosaic virus

A. Varma – Division of Mycology and Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India

A. J. Gibbs – Research School of Biological Sciences, Australian National University, Canberra, Australia

Contents

Introduction
Main Diseases
Geographical Distribution
Host Range and Symptomatology
Strains
Transmission by Vectors
Transmission through Seed
Transmission by Grafting
Transmission by Dodder
Serology
Nucleic Acid Hybridization
Relationships
Stability in Sap		 Purification
Properties of Particles
Particle Structure
Particle Composition
Properties of Infective Nucleic Acid
Molecular Structure
Genome Properties
Satellites
Relations with Cells and Tissues
Ecology and Control
Notes
References
Acknowledgements
Figures

Introduction

Described by Francki, Zaitlin & Grivell (1971).
Synonym
Temple tree mosaic virus. A virus with tubular particles 300 nm long and 18 nm in diameter. Sap transmissible. No vector known; is spread in cuttings of infected frangipani (Plumeria spp.). Restricted host range, grows best at 30-35°C.

Main Diseases

In Plumeria acutifolia the virus causes mosaic, ringspots, veinbanding and bronzing. In P. alba, it causes ringspots, leaf distortion and necrosis. No flower symptoms.

Geographical Distribution

Common in eastern Australia and northern India.

Host Range and Symptomatology

Host range not yet tested extensively, but seems restricted. More species become infected at temperatures above 25°C than below. At 35°C symptoms show in 3-6 days, at 22°C they take 2 weeks or more.

Diagnostic species
Datura stramonium. Chlorotic, necrotic or black lesions develop in inoculated leaves after 1-2 weeks in the glasshouse at 22°C. At 35°C, in controlled environment cabinets, similar symptoms develop in 3 days; one strain causes systemic necrosis along the veins and leaf margins.
Nicotiana glutinosa. At 22°C inoculated leaves develop chlorotic lesions in about 2 weeks. Not infected systemically.
N. tabacum (tobacco) cvs Samsun, Virginia Gold or White Burley. Rarely infected at 22°C. At 35°C all strains induce bright chlorotic or necrotic ringspots in inoculated and systemically infected leaves.
N. clevelandii x N. glutinosa. Not infected at 22°C. At 35°C inoculated leaves develop faint chlorotic lesions which become necrotic or develop ringspots. Not infected systemically.
Propagation species
Nicotiana glutinosa. Inoculated leaves give a good yield after 2-3 weeks at 22°C.
Assay species
Datura stramonium is the most reliable assay species.

Strains

Three distinct strains from different provenances have been distinguished by the symptoms they produce. They are the Adelaide strain (Adel) (Francki et al., 1971), and the Allahabad (Ald) and Delhi (Del) strains (A. Varma & A. J. Gibbs, unpublished data). Leaves of D. stramonium kept at about 22°C develop faint chlorotic lesions after inoculation with strain Adel, necrotic lesions after inoculation with strain Ald, and chlorotic lesions, later becoming black, after inoculation with strain Del. At 35°C symptoms developed more quickly and spread more: strain Adel gave necrotic lesions, strain Ald gave lesions with chlorotic haloes or ringspots, and strain Del gave spreading black necrotic ringspots and systemic veinal and marginal necrosis. N. tabacum cv. Virginia Gold was susceptible at 22°C to strain Del only, showing chlorotic and necrotic local lesions. At 35°C in the same tobacco cultivar, strain Adel gave faint necrotic ringspots, strain Ald gave bright necrotic ringspots and strain Del gave large ringspots both in inoculated and in tip leaves.

Transmission by Vectors

No vector is known.

Transmission through Seed

Not transmitted through seed of D. stramonium or N. tabacum cv. Samsun.

Serology

Particles of the virus are strongly immunogenic. They give flocculent precipitates in tube precipitin tests, and form one band of precipitate in gel diffusion tests.

Relationships

Properties, serological relationships and particle morphology place the virus in the tobamovirus group. The particles of frangipani mosaic virus are morphologically indistinguishable from those of other tobamoviruses. The Adel, Ald and Del strains are serologically closely related to each other. All three strains are related distantly to cucumber virus 4, cucumber green mottle mosaic virus, and an isolate of sunn-hemp mosaic virus from Queensland, Australia (but not one from West Africa); and even more distantly to TMV-type strain, TMV-U2 strain, tomato mosaic virus and ribgrass mosaic virus. (A. J. Gibbs & A. Varma, unpublished data; Franckiet al., 1971). There was no detectable serological relationship with Sammons’ opuntia virus even though comparisons of coat protein composition indicate a close affinity (Description No. 184).

Stability in Sap

Very stable. Sap from infected D. stramonium was not infective after heating to 95°C for 10 min, and lost 90% of its infectivity in 10 min at 90°C. The sap was still infective after 10 weeks at room temperature, and at dilutions up to 10-5.

Purification

The virus is easily purified from infected leaves of frangipani or N. glutinosa by several methods. The following methods give good yields:

1. Francki et al. (1971), based on McLean & Francki (1967) and Francki & McLean (1968). Homogenise infected leaves of N. glutinosa in 1.5 volumes of 0.2 M Na2HPO4, clarify by adsorption with charcoal and DEAE cellulose and filter through Celite. Sediment the particles by centrifuging at 44,000 g for 90 min. Resuspend pellets in distilled water and emulsify with equal volume of chloroform. Centrifuge at 12,000 g for 10 min. Collect aqueous layer and sediment the particles by centrifuging at 16,000 g for 30 min. Repeat chloroform extraction and sedimentation.

2. Based on Varma, Gibbs & Woods (1970). Triturate infected leaves mechanically with 2 ml/g of neutral phosphate-ascorbate buffer (equal volumes of 0.1 M disodium hydrogen phosphate and 0.05 M ascorbic acid). Add a quarter volume of chloroform, emulsify, centrifuge at 8000 g for 10 min, collect supernatant fluid and centrifuge for 1 h at 75,000 g. Resuspend the pellets in a small quantity of the buffer. Further purify by rate zonal centrifugation at 45,000 g for 75 min in gradients of 10-40% sucrose.

Properties of Particles

In dilute solutions the virus sediments as a single component with sedimentation coefficient (s20, w) of 188 S (R. D. Woods, unpublished data).A260/A280: 1.21.

Particle Structure

The virus has rod-shaped particles about 300 nm long and 17 nm wide. The preparations also contain shorter particles (Francki et al., 1971) (Fig.6).

Particle Composition

 Nucleic acid: The particles contain c. 5% RNA.Protein: Each subunit of the coat protein of strain Adel contains about 158 amino acid residues: Ala, 14; Arg, 11; Asx, 17; Cys, 1; Glx, 16; Gly, 9; His, 1; Ile, 11; Leu, 13; Lys, 4; Met, 0; Phe, 7; Pro, 4; Ser, 14; Thr, 13; Trp, 5; Tyr, 5; Val, 13 (Francki et al., 1971). Of the other tobamoviruses whose coat proteins have been analysed, Sammons’ opuntia virus has a composition most similar to that of frangipani mosaic virus..

Relations with Cells and Tissues

In the cytoplasm of infected parenchymatous cells of D. stramonium leaves, the particles of frangipani mosaic virus aggregate as microcrystals of various shapes and sizes. Particles were not seen in mitochondria, chloroplasts or nuclei although these organelles are not of normal appearance.

References

  1. Francki & McLean, Aust. J. biol. Sci. 21: 1311, 1968.
  2. Francki, Zaitlin & Grivell, Aust. J. biol Sci. 24: 815, 1971.
  3. McLean & Francki, Virology 31: 585, 1967.
  4. Varma, Gibbs & Woods, J. gen. Virol. 8: 21, 1970.

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