Article 87 – ‘Plant husbandry 5’

Hi welcome to Taiga Bonzai, in this article the last in the series we attempt to answer some of the questions that continue to perplex the most learned concerning the demise of flora. In many cases the answer is given in a reasonably short time frame, but there are instances where no definitive explanation can be agreed upon.

Introduction – with the planet constantly evolving evidence exists of events that have resulted, some have been of minor consequence whilst others have caused complete devastation. In 1815 Mount Tambora on the island of Sumbawa in Indonesia erupted, the largest volcanic eruption in history. In 1954, a swarm of locusts invaded Kenya covering an area of 200km2, the estimated density was 50 million individuals per km2 a total number of 10 billion locusts in that swarm. A 15 metre tsunami hit Japan’s Fukushima Daiichi nuclear power plant in 2011 causing a major catastrophe.

Life expectancy – nothing on this planet lasts forever, all flora, fauna including humanoids have a life expectancy and nothing can change this phenomenon. Even planet Earth has a life expectancy, a subject for another time as the implications associated would make this article far too long, but for those of a inquisitive nature we point you to the NEW ATLAS and their scientific author Michael Irving who wrote an article on this subject in March 01 2021. Link below.

https://newatlas.com/environment/earth-atmosphere-oxygen-life-expectancy/

Humanoids and fauna – it can be argued that a debate on these two species would make for interesting discussion and much has been written by notable academics including, Alfred Russel Wallace and Charles Robert Darwin works include, The Descent of Man and Selection in Relation to Sex (1871), The Expression of the Emotions in Man and Animals (1872). But, at Taiga Bonzai for the moment we are only concerned with flora and the problems associated.

Flora – all humans especially government officials are responsible for the planet’s well being concerning plant life regardless of the scale. Pests and disease transmitted by our actions either knowingly or not have been in existence for thousands of years, we have written articles on this topic ‘Unseen enemies’ 62 to 66 and 56 ‘Bug apocalypse!’ In the previous article ‘Plant husbandry’ 4 we mentioned the deadly disease Xylella fastidiosa first discovered by plant pathologist Newton Pierce in 1892, a disease that is an aerobic, Gram-negative bacterium of the monotypic genus Xylella. This plant pathogen is transmitted exclusively by xylem fluid-feeding sap insects. 

There is no chemical control for Xylella fastidiosa as is the case for many pests and disease, infected plants are destroyed to prevent the disease spreading further. A downturn in crop production costing vast sums of revenue to the tune of billions. Although many countries are deeply concerned, they just cannot find common ground to find a solution to the problem. Yet they whine, moan and sabre rattle on unimportant trivial items, hence it is difficult to comprehend their logic and justification for such.

The enemy – most common plant pathogens are fungi, bacteria, mollicutes, parasitic higher plants, parasitic green algae, nematodes, protozoa, viruses, and viroids. We will give a brief description on these and their functionality should you encounter them.

Fungi – many people believe fungi are plants, this a misnomer they are neither plants nor animals but organisms that form their own kingdom of life. The way they feed themselves is different from other organisms: they do not photosynthesize like plants nor do they ingest their food like animals. Fungi can be deadly poisonous as in the ‘Death cap’ Amanita phalloides variety and is the world’s most toxic mushroom. It contains alpha-amanitin which is responsible for causing liver and kidney failure.

Death cap fungi

Bacteria – there are both beneficial and pathogenic, beneficial bacteria are involved in such diverse processes as digestion in animals, nitrogen fixation in the roots of certain legumes, the decomposition of animal and plant remains and sewage disposal systems. Pathogenic bacteria called fastidious vascular bacteria grow in either the xylem or phloem tissues and interfere with the transport of water and nutrients in the plant vectored by sucking insects such as leafhoppers, planthoppers and psyllids.

Mollicutes – are parasite in the class of bacteria distinguished by the absence of a cell wall. The word ‘Mollicutes’ is derived from the Latin mollis and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. The best-known genus in the Mollicutes is Mycoplasma colonies which show the typical ‘fried-egg’ appearance.

Mycoplasma image courtesy of wwwuser.gwdg.de

Parasitic higher plants and Green algae – Hemiparasites often referred to as water parasites, do injure their host plants, absorbing water and mineral nutrients from them. They possess chlorophyll and can manufacture their own carbohydrates by photosynthesis. Green algae are a foliar disease most commonly seen in warmer climates or in greenhouses. The main organism is Cephaleuros virescens, a green parasitic alga whose usual hosts are plants with leathery leaves such as litchi, magnolias, hollies, rhododendrons and viburnums.

Parasitic green algae on guava Image courtesy of Scot Nelson

Nematodes – often called ’roundworms’ are the most numerous multicellular animals on earth. A handful of soil can contain thousands of the microscopic worms many of them parasites of insects, plants or animals. Free-living species are abundant, including nematodes that feed on bacteria fungi and other nematodes. There are nearly 20,000 described species classified in the phylum Nemata many of which are associated with disease.  
 

caenorhabditis-elegans-nematode

Protozoa – are a group of single-celled eukaryotes either free-living or parasitic that feed on organic matter such as other microorganisms or organic tissues and debris. They come in many different shapes and sizes ranging from an Amoeba which can change its shape to Paramecium with its fixed shape and complex structure. Some are parasitic meaning they live in other plants and animals including humans where they cause disease. 

Protozoa Image courtesy of Frank Fox Microbiology Society 

Viruses, and viroids – a virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms from animals, plants and other microorganisms, including bacteria and archaea. Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants) and most cause disease.

Cowpea mosaic virus Image courtesy of Thomas Splettstoesser (www.scistyle.com) 

The hidden menace – in part 4 of this series we stated that “the problem with disease is that it cannot in reality be detected until there is visible evidence, either insect damage or that of fungi and canker.” Here is an example of our meaning, approximately 4 years ago we obtained a 3 year old Sea buckthorn plant Hippophae in the family Elaeagnaceae.

Sea buckthorn Hippophae

The aim was to train it into a Bunjin-gi literati style, in the first winter we did some work to the trunk and foliage right hand image. We decided to take our time with the design and make gradual changes so as not to stress out the tree and the cuttings were planted in different containers. All was progressing according to plan until beginning of summer 2022, when we discovered the trunk was coated in a white fungus, leaf drop had begun and remaining leaves showed signs of chlorosis. We knew the end was nigh for this plant hence it was destroyed.

Naturally our readers will want answers as to the tree’s demise so we will answer them here:

Q. what disease killed the tree – A. Verticillium wilt sp. was the culprit for which there is no effective treatment

Q. did the problems come from the soil medium, incorrect watering and bad position – A. when the plant was purchased the original soil was removed and the plant washed, it was re-planted in the same soil medium we use for all our deciduous species and we have no problems with it. Watering was twice daily in the summer and less in the winter; the tree had a good sunny position with plenty of light and air movement

Q. are any of your other trees showing signs of infection and what about the cuttings you took, A. no they are thriving very well and the cuttings were taken from the original plant after it had been repotted nevertheless, we will keep a watchful eye on them

Q. if there were no problems at your end how did the disease get there A. Verticillium wilt can lie dormant until the conditions are such that is activated, it can spread rapidly killing sea buckthorn varieties in two years with the variety Clara being the most infected; we are of a conviction that this was the case in this instance – it was already there when we obtained it.

Sea buckthorn is a plant that has few diseases. Among the diseases that can occur in sea buckthorn plantation we mention: verticillium wilt (Verticillium albo-atrum, Verticillium dahliae), Fusariosis (Fusarium sp.) and decay caused by fungi from the genera Phytium, Alternaria and Botrytis. Verticillium wilt can occur quite often in sea buckthorn plantations, the pathogen Verticillium sp. being so dangerous is able to kill the shrubs very quickly.

This series ‘Plant husbandry’ (1 to 5) has been a discussion on plant care and also on plant pathology and we trust that you have found the content useful. This website Taiga Bonzai has many more articles on various topics relating to bonsai and horticulture in general, feel free to browse at your leisure; until next time, BW, Nik.