The spread of corruption, particularly in plants, was a powerful idea that Tolkien used in his work, especially the Lord of the Rings, to show that something was wrong.

“Wide flats lay on either bank, shadowy meads filled with pale white flowers. Luminous these were too, beautiful and yet horrible of shape, like the demented forms in an uneasy dream; and they gave forth a faint sickening charnel-smell; an odour of rottenness filled the air. From mead to mead the bridge sprang. Figures stood there at its head, carven with cunning in forms human and bestial, but all corrupt and loathsome.”
Conversely, healthy plants and food was a strong theme that he used for showing that all was well.

“In a twinkling the table was laid. There was hot soup, cold meats, a blackberry tart, new loaves, slabs of butter, and half a ripe cheese: good plain food, as good as the Shire could show, and homelike enough to dispel the last of Sam’s misgivings (already much relieved by the excellence of the beer).”
It was no coincidence that one of the most overtly good and friendly characters in the Lord of the Rings was Tom Bombadil’s wife, Goldberry.
Tolkien used the idea to show the enormity of the task that was faced by the free-folk of Middle-earth, with Gandalf saying, “And for my part, I shall not wholly fail of my task, though Gondor should perish, if anything passes through this night that can still grow fair or bear fruit and flower again in days to come.”
And when it was all over and the world was set to rights what better way to show this than in my favourite quote from LotR, “Altogether 1420 in the Shire was a marvellous year. Not only was there wonderful sunshine and delicious rain, in due times and perfect measure, but there seemed something more: an air of richness and growth, and a gleam of a beauty beyond that of mortal summers that flicker and pass upon this Middle-earth. All the children born or begotten in that year, and there were many, were fair to see and strong, and most of them had a rich golden hair that had before been rare among hobbits. The fruit was so plentiful that young hobbits very nearly bathed in strawberries and cream; and later they sat on the lawns under the plum-trees and ate, until they had made piles of stones like small pyramids or the heaped skulls of a conqueror, and then they moved on. And no one was ill, and everyone was pleased. Except those who had to mow the grass.”
As someone who has to prepare and maintain the local Domain grass cricket pitch, that sentence always makes me smile.

Why are these metaphors so effective for Tolkien?
We are coming up to our Southern Hemisphere Christmas soon. One of the best indications that our summer holidays and festive season is upon us is that local berries are starting to fruit. Christmas Day meals in New Zealand are often built around strawberries and raspberries (and sometimes blackberries and boysenberries). There are queues at local berry farms on Christmas Eve to grab punnets of these luscious, delicious berries. Some of my earliest memories of Christmas are about helping to remove the stalk and leaves off bowls of strawberries before adding the icing sugar.
I’m sure for Tolkien that berries and fruit represented the lazy, hazy days of summer as well (if not the Antipodean Christmas aspects). The berries only ripen and mature under good conditions. If things are not right then the berries spoil quickly. Who has not picked a bowl of berries only to find a day later that they have gone mouldy? Berries are then spoiled and not able to be eaten. All of that promise is gone. Things are not right with the world.
When Tolkien wants to show that darkness in stirring in Mirkwood he invokes the metaphor of rotting. “There lies the fastness of Southern Mirkwood,’ said Haldir. `It is clad in a forest of dark fir, where the trees strive one against another and their branches rot and wither.” When he wants to show happy times, such as when the entwives were active in the world, he invokes the metaphor of healthy fruit. “When Summer warms the hanging fruit and burns the berry brown; When straw is gold, and ear is white, and harvest comes to town; When honey spills, and apple swells, though wind be in the West, I’ll linger here beneath the Sun, because my land is best!”

One of the common sources of spoilage of berries is from the downy mildew (Peronospora sparsa). This fungus can infect the leaves of fruits, like boysenberries, in early spring causing lesions, which then cause more infections. If fruits are infected then they prematurely redden and harden. Downy mildew can easily cause 50% losses in boysenberry crops (and 100% in some organic crops).
Eirian Jones and Herath Mudiyanselage were tasked with finding a way to reduce downy mildew in boysenberries. There is a particular issue in that planting material often is not disease-free. Fungicides are typically used to remove the downy mildew but heat treatment (where plants are held at a high temperature of 34oC or so for several weeks) has proven successful for some other pathogens.

Eirian and Herath and their colleagues took boysenberry plant samples and subjected them to either a heat treatment, a heat + fungicide treatment, or a control with no treatment. After the treatments, the plants were grown for several weeks. They were observed for spore growth as well as having samples taken for spore DNA to be detected.
They have reported their findings in the European Journal of Plant Pathology. The untreated controls had 100% infection but the other two treatments were around 17% infected. The fungicide played no obvious role, implying that a heat treatment was the main reason for success. One important outcome was that the heat treatment allowed the production of mature plants that were downy mildew-free. These plants would then produce healthy fruit.
This research has the potential to allow more crops of berries to grow and be harvested, fresh and healthy. It will majorly reduce the amount of spoilage that occurs. This can only add goodness to the world! Tolkien would have approved.