Hi, welcome to Taiga Bonsai, in this article we continue our discussion on ‘Plant husbandry’ dealing with more harmful pests and disease.

Introduction – during World War II (1939 – 1945) many governments mandated that more produce be grown to feed those at the front line and rationing was introduced which lasted until 1954. Meadows and wildlife havens were turned into arable land and although the effects of this were not apparent at the time; it was the beginning of the end for the bug world.

The birth of the EEC – on March 25th, 1957 France, West Germany, Italy, the Netherlands, Belgium and Luxembourg signed the Rome treaty establishing the European Economic Community (EEC), also known as the Common Market. Later other countries joined and soon there was an abundance of food.

This excess including butter mountains, milk and wine lakes, gluts of potatoes, apples and other crops could have been given away to the poor, or countries facing drought and famine. Instead what could not be poured away was disposed of in disused mine shafts. The politicians and agricultural heads wanted to maintain ‘economic stability’ – ‘nothing is for free’.

The green and pleasant lands are now a bygone era, forests have and are being cut down. An area the size of Wales 20,779 km² (a country in southwest UK) is being removed on a daily basis in the Amazon.

The meadows that existed are now under housing estates, rivers are polluted and the air quality is deteriorating. The friendly bugs have gone and it is doubtful they will return. The crop harvests GMO or organic will devastated by marauding invaders many whom are immune to pest control.

A never ending battle – according to CABI News digital library (09 February 2022) they conclude there are approximately 73,000 different tree species on Earth, of which around 9,000 are thought to be undiscovered. In addition, there exist more than 80,000 known plant diseases worldwide.

All plants are vulnerable to attack by disease, including crop plants which are frequent victims. The result is enormous agricultural, horticultural and economic loss. Now due to the relaxed regulations pest and disease are able to infect countries that were free of this devastation.  

The problem with disease – is that it cannot in reality be detected until there is visible evidence, by insect damage or that of fungi. Science has told us that microorganisms can exist in a single-cell form or a colony like bacteria and fungi. Although they are often associated with dirt and disease, most microbes are beneficial. But as we are aware there exist those microbes, fungi and pathogens that have lethal potential; here a few examples.

Armillaria mellea is a parasitic fungus doing immense damage to forests, it attacks both coniferous and deciduous species. By the time the fruit bodies are in evidence, the damage done internally is usually so great that the tree is doomed.

It is widespread in northern temperate zones including North America, Europe, Northern Asia and in South Africa. Trees that are attacked become parasitized. The foliage becomes sparse and discoloured, twig growth slows down and branches die back. There are no known fungicides or management practices that can kill Armillaria mellea after infection without damaging the infected plant.

Canker is a small area of dead tissue, which grows slowly, some of these are of only minor consequence, but others are ultimately lethal and therefore, can have major economic implications for agriculture and horticulture.

They are caused by a wide range of organisms including fungi, bacteria, mycoplasmas and viruses. The majority of canker-causing organisms are bound to a unique host species or genus, but a few will attack other plants. Fungicides or bactericides can treat some cankers, often the only available treatment is to destroy the infected plant to contain the disease. The Butternut canker (shown below) is a lethal disease affecting Butternut trees for which there is no cure.

This is a deadly bacteria that attacks economically important crops such as olive, citrus, plum trees and grapevines. Since 2015, it’s been rapidly spreading from the Americas to Europe and Asia. Once the disease infiltrates a plant, it is there to stay, it starves the plant of water until the plant dies or becomes too weak to grow fruit. 

Xylella fastidiosa – is another deadly disease the bacterium (shown below)

X. fastidiosa costs $104 million per year in wine losses in California and in Italy. The bacteria has led to the decline of 180,000 hectares of olive groves destroying many centuries-old trees; a loss of €390 million over three years. X. fastidiosa constitutes a threat not only to Italy but to all the Mediterranean region’s economy.

X. fastidiosa is not known to be in the UK however, there have been outbreaks of the disease in mainland Europe in France, Italy and Spain. Portugal confirmed its first case in 2019 on lavender.

The UK Government is concerned about how to prevent the disease being accidentally brought into the country on imported plants. In 2020 Lord Framlingham a Conservative peer asked the Government what the UK’s regulations are regarding X. fastidiosa.

UK regulations were to introduce measures to strengthen the protection of plants from certain pests and diseases, including Xylella. They were made under article 52 of the EU Plant Health Regulation, allowing the UK to take additional temporary national measures. Providing they inform the European Commission and put forward a technical case to request EU measures against a specific pest.

However, those measures have not or will not be introduced in time to mitigate the risk concerned. Moreover, the UK Government has argued that current EU emergency measures on Xylella, do not address risks highlighted in the UK’s pest risk analysis on the disease.

In particular, it is not clear if or when the EU emergency measures will be reviewed to address these risks and ensure a greater degree of assurance of disease freedom, in relation to plants of those species being moved in the EU and introduced from third countries.

As such, there remains an unacceptable level of pest risk and this instrument introduces national measures under article 52, in the absence of EU requirements.

Verticillium– is a genus of fungi in the division Ascomycota, which is an anamorphic form of the family Plectosphaerellaceae. The genus used to include diverse groups comprising saprobes and parasites of higher plants, insects, nematodes, mollusc eggs and other fungi.

The genus, currently thought to contain 51 species, may broadly be divided into three ecologically based groups – mycopathogens, entomopathogens, plant pathogens and related saprotrophs. At least five species are known to cause a wilt disease in plants called verticillium wilt: V. dahliae, V. longisporum, V. albo-atrum, V. nubilum, and V. tricorpus. A sixth species, V. theobromae, causes fruit or crown rot, a non-wilting disease.

Verticillium wilt is a disease that can affect over 400 different plants and trees, many of which are economically important worldwide. Several characteristics of Verticillium make it difficult to manage: prolonged survival in soils without the presence of a host plant.

The fungus survives in the soil principally in the form of microsclerotia and invades the plant through the root system, colonising the vasculature eventually leading to plants demise.

The main mechanisms of it’s pathogenesis are xylem vessel blockage and toxin production. When the fungus propagates within a host plant, the mycelium blocks the xylem vessels, impairing the transport of water and nutrients in the host.

Thus forces of transpiration and respiration in leaves combined with blocked xylem transport, cause water imbalances in leaves that result in leaf yellowing and wilting, contributing to plant death.

In addition, Verticillium produces mycotoxins within the plant that can cause necrosis in leaves and impair metabolism in the plant’s body. In some systems, toxin production has been shown to be the main cause of plant wilting.

The diseases discussed here (Armillaria mellea, Butternut canker, Xylella fastidiosa and Verticillium) are very serious not to be taken lightly, they can infect other plant types within the vicinity. However, there are many more to be found within the 80,000 diseases that we know of. In the next article we look at the borers, until next time, BW, Nik.

Hi welcome to Taiga Bonzai, in this post we discuss horticulture in other parts of the world, where nations are having difficulty in controlling pests and disease.

Introduction – horticultural methods in general have two schools of thought when growing crops, either by (a) conventional methods (organic) or (b) genetically modified organisms. (GMO)

Conventional – is an agriculture term referring to a method of growing edible plants such as fruit and vegetables without the use of synthetic chemicals. (fertilizers, pesticides, antibiotics, hormones)

GMO – method of cultivation often use fertilizers and pesticides which allow for higher yield, out of season growth, greater resistance, longevity and greater mass.

Organic versus GMO – people have very strong opinions on which method of horticulture is better. Some advocate a preference for organic because it is healthier, tastes better and growers refrain from using pesticides. But there are negatives to this approach, fruit and vegetable yields will suffer due to the inevitable onslaught of pests and disease during the growing season for example.

Many insects attack Brassica species the most common are diamondback moth Plutella xylostella also called cabbage moth, tobacco cutworm, aphids and many others. Hence more is planted to compensate for the loss and although organically grown food is preferable and more beneficial to consumers because it does not contain chemicals; it is more expensive.

Whereas GMO use seeds that have been genetically modified to grow plants that have a faster growth rate, higher yields, are said to be pest and disease resistant and are cheaper to buy nonetheless, there are negatives to this approach.

The use of synthetic pesticides and fertilizers on fruit and vegetables may eradicate many known pests and disease, but also kills insects that are beneficial for example. The lady bird beetle Coccinellidae a predator extremely proficient in eradicating aphids and scale colonies.

Other nations – ‘Nilaparvata lugens’ the brown plant hopper (BPH), is a planthopper species that feeds on rice plants Oryza sativa L. These insects are among the most serious pests of rice a major staple crop for more than half the world’s population. 

They damage rice directly through feeding and also by transmitting two viruses, rice ragged stunt virus and rice grassy stunt virus. Up to 60% yield loss is common in rice cultivars attacked by this insect. BPH is found throughout Australia, Bangladesh, Bhutan, Burma (Myanmar), Cambodia, China, Fiji, India, Indonesia, Japan, North and South Korea, Laos, Malaysia, India, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Taiwan, Thailand, and Vietnam. 

The brown plant hopper is dimorphic and can be either ‘macropterous’ (long wings) or ‘brachypterous’ (short wings) forms. The macropterous forms are migrants and invade new fields/paddies. Adults usually mate on the day of emergence, and the females start laying eggs from the day following mating. Brachypterous females lay 300 to 350 eggs, whereas macropterous females lay fewer eggs; the eggs hatch in about six to nine days.

In Asia, India has the largest area for rice cultivation occupying 29.4 % of the global area, but has the lowest yield. The conventional paddy growing practices are in crisis due to social, biological and technical setbacks. Yet there is a growing demand for rice due to ever burgeoning population.

Rice demand in 2010 was estimated to be 100 million tonnes and this would increase by 50% in 2025 to assure food security in the world’s rice-consuming countries. However, with water becoming scarce many fields are drying out and coupled with increasing infestations of Nilaparvata lugens causing yield loss, it will difficult to fulfil the demand.

The cotton bollworm Helicoverpa armigera is a major pest of cotton Gossypium spp. maize, Zea mays, pulses, Fabaceae tomatoes, Solanum lycopersicum and sorghum bicolour throughout most of the world. But has only recently arrived in the Americas where it is rapidly spreading. It has documented resistance to 49 pesticides and is one of the most polyphagous and cosmopolitan pest species. 

This species of Lepidoptera is found in Asia, Australia, New Zealand, Europe, Africa and South America. The adults emerge from the soil in the first 3 weeks of May and 2-6 days later oviposition begins. This is a period lasting between 5-24 days. Within this time frame, a female may lay up to 3180 eggs, up to 457 in 24 hours singly and mainly at night on various crops.

Including, chickpeas, cotton, maize, okras, tobacco, tomatoes; when temperatures rise to 25°C, the eggs will hatch in 3 days and larvae immediately begin crop infestation and devastation. When fully fed, the larvae descend to the soil after 1-7 days pupate in an earthen cell 2-8 cm below the surface.

Pesticides – of which there are many used to control Helicoverpa armigera including, Lambda Cyhalothrin, Chlorpyriphos, Cypermethrin Acetamiprid and Profenos Cypermethrin. But as stated previously this pest has documented resistance to 49 pesticides. Moreover, we have pointed out many pests and disease cannot be eradicated.

In 2020 global pesticide usage was estimated to increase from 2 million tonnes to 3.5 million tonnes with China being the main user 1,763,000 tons followed by America 407,779 tons, Brazil 377,176 tons and Argentina 196,009 tons. One may argue that pesticides are beneficial for crop production, but extensive use of pesticides can possess serious consequences because of their bio-magnification and persistent nature.

Diverse pesticides directly or indirectly pollute air, water, soil and overall ecosystem which cause serious health hazards for living beings. One only has to look at the tens of thousands of lawsuits filed against Monsanto (now part of Bayer) over their chemical ‘Roundup’. Until next time, BW, Nik.