Pest and Diseases

A. Diseases caused by fungi

1. Rust (Different types of fungi)

1.1 Symptoms: Brown to yellow pustules on the leaves. First you will notice only a few, but they multiply quickly during favourable weather conditions. Although not lethal to the plant, they can slow down the growth of the plant.

1.2 Treatment: Spray regularly with one of the following broad spectrum anti-fungi: Bravo; Diathane 45; Funginex or Zineb.

 

 

2. Leave dieback (Microphoma agapanthii)

2.1 Symptoms: The leaves die back from the tips of the leave, leaving a pale, brown remains. If left untreated, the leave will die back to the base of the plant. (With sunburn only the front tip of the leave die back and it has a brown/straw like colour.)

2.1 Treatment: The best way to treat is to cut of the leave as far as possible from the infected part. Treat the wound with Bravo or Diathane 45.

 

 

3. Damp-off disease (Rhizoctonia, Fusarium, Phytophthora and Pythium)

3.1 Symptoms: Pythium: Plant starts to rot and die back. It affects adult plants as well as seedlings. Usually occurs in summer when it is hot humid.

Phytophthora: This fungi cause's root rot. The plant usually shows effects of drought. On closer inspection you will find that all the roots are soft and rotten

3.2 Treatment: Pythium: Use Kocide 2000 to give the plant or seedlings a good drench.

Phytophthora: Thoroughly clean and cut away the affected parts of the plant and treat with neat Bravo. Leave the plant in the shade for a couple of days and then plant it in sterilized sand or milled pine bark.

 

 

I noticed rust on marks on the penduncles. I spoke to Bill Smit of Effekto @ 021-804-1008. He said he had not heard of it yet, but recommended I use Funginex in conjuction with Bravo. Last year I cropped some 2,000 seed that had been pollinated for breeding purposes.

Nick Primich
Newsletter Vol. 6 No 4 Dec 1996

 

Damping off of young seedlings is probably the worst disease to contend with. As mentioned earlier this problem can be eliminated by using a pathogen-free germinating mix.

James Haxton
Newsletter Vol. 8 No 2 Winter9 1999

 

To prevent fungal diseases, drench plants with a solution of fungicide and water - do not wait until plants are affected, but treat preventatively to avoid damage.

Mick Dower
Newsletter Vol. 9 No 1 Autumn 2000

 

Take three teaspoons Jeys fluid to 3/4 bucket of water. Clean the rotten parts off the stems and put the Clivia into the mixture - for a day or so. Take out and spread under the shady trees. Leave until they start to grow. They can be left there for many weeks and then be planted.

Marie Doyer
Newsletter Vol 9 No 4 Summer 2000.

 

The reason that many plants start rotting is because they are receiving too much water in one way or another. ie A potting mix which doesnt drain well, or a drip from a sagging shade cloth roof,  or perhaps overwatering.

Here in the Cape   ( South Africa )  a system which is practised by many is as follows:

Remove the plant from the growing medium. Clean thoroughly,  removing all sign of rot.  This can be quite drastic. Treat the wound with , at least, Flowers of Sulphur or a stronger fungicide if you wish. Neat Bravo is often used here. Allow to dry for a day or two in a cool spot.

Then,  plant in good clean river sand,  or the sand used for swimming pool filters. Dont overwater. Usually,  the results are absolutely excellent and the response almost immediate.

At present I have a plant that has been battling for months.  I mean from about July last year,  and had virtually all the growing base cut away.  I placed it in some fine, clean river sand and to my complete amazement,  it
is sending out roots. I really didnt think this one had a chance.  I am quite convinced that had this been placed in water,  it would have been thrown out in a horrid bath of slime long since.

Felicity Weeden
Enthusiasts 10 February 2004

 

I have done some research and found that leaf die-back is a "fungus", rife in "Agapanthus", known as " Macrophoma  Agapanthi", which also damages the foliage of Clivias. To solve this problem spray the plants every two weeks with copper oxycloride. The product I have used successfully, which contains copper oxychloride is a product known as KOMBAT RUST', distributed by Starke Ayres Pty Ltd.

Dickie Gunston
Enthusiasts March 2004

 

May I add that the milk has an antifungal property too. I mist my seedlings at least once a week with 50/50 milk and water.

Denise Wiltshire
Enthusiast e-mails – Jul 2004

 

The dairy product and clivia topic is getting very interesting.

Not so long ago I asked a horticulturist at one our botanical garden in Amsterdam about the spread of virus in plants. She advised me to dip the scissors or cutting utensil in low-fat milk when removing or trimming leaves.

What's next - clivias grown in milk?

Hans van Verseveld
Enthusiast e-mails – Jul 2004

 

Let me add my tupence's worth.  American New Scientist (a journal subject to peer review) carried an article a while ago concerning milk and Botrytis (downy mildew).  A 10% full cream milk/water was found to be extremely effective against mildew.  I have tried it in my nursery and can testify to the efficacy of this broth!  Only - Clivias never get Botrytis!

Mike Viviers
Enthusiast e-mails – Jul 2004

 

I am involved in the greenhouse industry and can report that milk has been used for many years to "sterilize!" equipment/instruments like knives, prunig seccateurs etc. during operations to prevent diseases from being spread from plant to plant by the equipment that are used to remove leaves, side shoots etc.

Prof. Gert Venter
Enthusiast e-mails – Aug 2004

 

The usual belief is that virus isn't transmitted by seed. I've never heard of an instance.

The virus streaks are usually accompanied by a "thinning" of the cells and are not usually regular. This has helped me detect virus in orchids, and keep virused plants out of my collections.

However, variegated Clivias that are striped are not virused. With Camellia flowers, the rule is striped streaking is not virus, but blotches are. Some popular Camellia cultivars are virused: growers don't seem to care. My favourite Camellia is a virused cultivar and I'd never grow it.

Better news is that, if new growth is clean and unstreaked, then the plant is not virused.

The worst news that a virused plant can lurk, symptomless, for years.

Glenn Callcott
Enthusiast e-mails – Aug 2004

 

I decided to look into the use of peroxide a bit more. If you do a yahoo search and use " plants hydrogen peroxcide" for your search, you will find many interesting articles on the subject of horticulture use of H202.  Here are the basics.  It is suggested you use a 35% solution of food grade peroxcide to start. Farm suppliers may carry it.  I guess it is less expensive to use. Then you mix it down to a 3% solution.  The drug store kind is already a 3% solution and it can be used too.  I think there is some stabilizer ingredients found in the drug store kind that make it unfit for certain uses of hydrogen perxocide, such as internal.  Here is the solution mixes and their uses.

Add 1 oz of 3% solution to 1 pint of water and soak seeds overnight. Add 1 oz of 3% solution to in quart of water or 16 drops to 1 quart of water to make a solution for watering and misting plants. Add 8 oz of 3% solution to 8 oz. of white sugar and 1 gallon of H20 to make an insecticide. According to the artcicles, the H202 will prevent root rot and correct exixting root rot by adding oxygen to the soil. The oxygen will kill the anerobic rot and stimulate the root growth. It is used to contol algae and fungus.

Tracy Ann Hyde-Garriga
Enthusiast e-mails – Oct 2004

 

My main guess (from your description) is that your plant has root or crown rot. This is cause by fungus like Phytophthora and others like Rhizoctonia and Pythium.. The main cause of this disease is poor drainage and poor air circulation. The cause of yours will probably be phytophthora. You can easily tell by smelling the "rotting" end. It will exude a very distinct strong rotting "green" smell. The other cause will be Bacterial Soft rot cause by a bacteria in the Erwinia family. You can recognise this by the rot under the leaf surface like a clear bubble.

For the cheap treatment of wounds, many people have been very successful just by using the flower of Sulphur or just plain sulphur powder. Of course there are many plant "wound" sealants that can be used. Normally, the plant is cut down to a clean part, then spray with a fungicide and dry a little before sealing the wound. Please note that these diseases can be spread on contact. Therefore the last cut must be made with a sterilized sharp knife.

For prevention, firstly there's the aeration and then the growing media must be free draining. Preventative fungicides includes both systemic and contact:

Some of the fungicides used successfully are: Dithane M45 - contact, Physan - semi systemic, Captan, Consan - contact, Tersan - contact, Benlate - systemic, Ridomil - systemic (very good for phytophthora but expensive), Terrozole, Aliette, Banrot, Terraclor and Fongarid.

Please note that some fungicides are pathogen specific, so you have to know what type of disease you have for the best effect. some of the Fungicides with a broad spectrum are Banrot, Truban and Tersan or Physan. Aliette and Ridomil are used extensively for the control of phytophthora.

Please note that I have given Common or Commercial names. You can look up their active ingredients and may be source a product containing that ingredient locally.

Chris Ong
Enthusiast e-mails – Nov 2004

 

I think it would be ok to dump them in a compost pile. I understand that viruses, whether in plants or in animals, do not survive for very long outside living plant tissues - they have to be transmitted to a plant rather directly, for example, via an insect bite. Does anyone know any more about this?

M ary Gorton
Enthusiast e-mails – Dec 2004

 

I'm not a compost expert but I can tell you why not to put diseased plant material on a pile. The heat created in a compost pile is not sufficient to kill virus. Plant material on the edges of the pile would never attain any proper degree of killing heat, thus, it would only perpetute the virus and pass it on to other plants whe the compost is used. The same principle applies to weeds. The heat will not kill the seeds or plants. And as such, you are putting weedy seeds/plants that can survive anywhere in the richest soil possible.

John Ingram
Enthusiast e-mails – Dec 2004

 

Now that the Tetracycline treatment of a virused plant has come to rest thanks to the advice of some very prominent professionals in the biochemical/medical fields let's all get down to basic on how to avoid this "incurable" disease.

The main vector for the spread of virus diseases of plants is MAN or politically correctly known as a person. As usual, it is the tools he wield in his hands that spread the disease. Any person who have ever taken a keen interest in Orchids knows how this disease can spread and the by-word in the orchid world is seek and destroy. No quarters given. Of-course, this is only an advise. The practical is another thing.

Virus in Orchids are mainly spread by the transference of 'sap containing virus particles' from one plant to another. 99% of this transfer is via gardenning tools; mainly the cutters. Therefore it is recommended that Tools be sterilized between use from one plant to another.

There are a number of ways that are recommended for this sterilization process.

Heat treatment. The cutting edges be burned in a burner until 'very hot'. Note that this process can distemper your precious cutting tools or destroy special coatings on them. I used to switched to "cheap" cutters and being lazy just dip the cutting section into spirit and burn this off. Do this 2 to 3 times just to be comfortably sure.

Sterilising solution - Recommended 10% bleach or saturated Trisodium Phosphate (there may be others). Please note that "bleach" can destroy stainless steel and the other is very corrosive. So please use gloves if you are going to be using these.

It looks like there are many Orchidphiles among the Clivia growers. Let us not have a situation where "virus" becomes as common a word in Clivias as it is in Orchids.

Note that not all virused plants will show symptons and not all "like" symptons are due to "virus". There was a general rule that if the "virus symptons" shows through on both sides of the leave, the chances are it is virus.

I understand that this may be that much "basic" news for most. Just trying to help those that may fall into the "novice" category like myself in Clivia.

Chris Ong
Enthusiast e-mails – Dec 2004

 

On the use of Confidor
The only problem with this is that the product only lasts for about 3 weeks if used as a foliar spray, where if it is used as a drench it can last 3 to 4 months. The BTAS control, I think says it lasts a year though. My friend that works for Bayer told me that on citrus trees that were treated once, aphids died almost 3 years later after that application so it does stay in the plant for a long time and the easier to kill insects die for a longer period of time, where scales and harder to kill insects die only 3 to 5 months later.

Tom
Enthusiast Group – May 2005