Category: Pests and diseases


Picture by Barry Simmons

Picture by Barry Simmons

Old School Gardener

horticultural_fleeceHorticultural fleece laid over plants can bring earlier crops and other benefits.

Fleece is a finely woven material that protects crops from wind and cold, and raises soil and air temperatures slightly, all helping plants to advance faster than unprotected crops. If it is anchored in the soil properly it also protects against flying pests, such as carrot root fly.

Because fleece allows water and air to penetrate, it reduces watering requirements and increases airflow around the plants. This encourages hardier growth and discourages disease build – up. If used carefully, fleece can last for many seasons.

Being porous, fleece does not warm the soil as well as plastic cloches or black plastic sheeting. It can also lay flat in wet conditions, making germination difficult, and it can easily tear on windy sites.

Fleece comes in all shapes and sizes, like this zip up jacket protector for tender shrubs by Harrod Horticultural

Fleece comes in all shapes and sizes, like this zip up jacket protector for tender shrubs by Harrod Horticultural

Other uses of fleece:

  • to extend the growing season, making maximum use of the garden

to improve the performance of half hardy crops, such as peppers

to produce softer, more palatable growth in vegetables that become tough with winter exposure, such as spinach and chicory.

In recent years another material called ‘Enviromesh’ has come on to the market. This fine-weaved plastic netting is strong and lasts for ages. It is fine enough to keep off small insects such as butterflies, carrot fly, flea beetles and leaf miners, and yet durable enough to keep pigeons off. It is also good frost and wind protection. I use it here in Old School Garden, both early in the season to protect young crops and also later as a useful cover for raspberries and other bush fruit which is otherwise unprotected against birds. The downside is that it is more expensive than fleece, so shop around!

Enviromesh tunnel using pegs to hold it down- picture Enviromesh Ltd.

Enviromesh tunnel using pegs to hold it down- picture Enviromesh Ltd.

Alternatives which can do pretty much the same job are old net curtains (you can get off white ones relatively cheaply from charity shops) or builder’s netting used around scaffolding or to protect against falling debris.

Sources and further information:

Gardeners’ Advice- RHS Wisley Experts, Dorling Kindersley 2004

Alys Fowler- Netting

Old School Gardener

pest controlPests and diseases-

Buy varieties of plants that are restistant to pests and diseases. If you want to grow vegetables, choose modern varieties that are easier to grow and protect them with crop covers such as insect-proof mesh or garden fleece. Encourage natural predators to take up residence in your garden by growing nectar-rich flowers, providing nesting and overwintering sites, and by feeding birds in winter. Use bilogical controls in the greenhouse.

Further information:

Natural pest and disease control

Biological Pest control- RHS

Source: ‘Short Cuts to Great Gardens’ (Reader’s Digest 1999)

Old School Gardener

 

cat in cloverA few more clippings from a book I bought in a charity shop last summer ….

Mesh Maxim:

The best-laid schemes of mice and gardeners aft a-gley, especially where cats and kids are concerned. It’s one thing to install a cat-proof, child-proof seedling net. It’s another thing to prove to the cats or children that they can’t get through it.

Bamboo Laws:

1. Stakes to support floppy plants are used by children to break the floppy plants they supported.

2. Bamboo canes make more realistic spears than those sold in the toy shop.

The Cat Trap:

The only way for a cat hater to keep cats out of his garden is to get a moggy of his own.

Laws of Attraction and Repulsion:

1. Where dogs, cats and children are concerned, seedbeds and wet concrete have irrestible magnetic propoerties.

2. If you lay a path to protect the lawn and the flowerbeds  you are simultaneously creating a force field which prevents children and animals from using it.

Kidology

Children are always on their pest behaviour in the garden.

children in gardenFrom : ‘Mrs. Murphy’s Laws of Gardening’ – Faith Hines (Temple House books, 1992)

Old School Gardener

 

Large-trees-HD-picture-5-44992A few more clippings from a book I bought in a charity shop last summer ….

Celsius Curse:

Anything that survives the coldest, wettest summer since records began will perish during the mildest winter on record.

First Law of Arboriculture:

The magnificent mature tree you spotted in the National Trust garden and a similar sapling bought later at your local nursery at great expense take a hundred years to mature. no one told you this. Even if you did live to see it, the full-grown tree wouldn’t look the same in your garden.

Au Soleil:

The carefully selected, ideal situation chosen for the specimen, shade-loving shrub in November will get the full force of the sun all summer.

Law of Planters Can’t Be Choosers:

A gardener who is hunting for shrubs or trees looks first at the specimens suitable for his land, then at the substitutes on his list, and finally buys the one he can afford.

Incredible-Flowering-Shrubs-Design-ideas-for-pretty-Landscape-Traditional-design-ideas-with-columns-flowers-grass-hosta-landscape-design-Porch-shade-garden-shrubs-turf-vineFrom : ‘Mrs. Murphy’s Laws of Gardening’ – Faith Hines (Temple House books, 1992)

Old School Gardener

 

greenflyA few more clippings from a book I bought in a charity shop last summer ….

Altruism Truism:

A garden is an area of land devoted to growing fruit, flowers and vegetables, which in turn are dedicated to insect rearing.

corollaries;

1. The earth is alive to the sound of mastication.

2. Healthy plants breed healthy bugs.

Law of the vegetable patch:

A dose of insecticide whch would wipe out a medium-size town will do no more than temporarily stun a cabbage white. You can fool all of the people some of the time, but you can’t fool the caterpillars.

Law of Killing Generosity:

Don’t look a gift horse in the mouth, but if it comes from a garden centre, do check for trojan aphids somewhere in its anatomy.

A Winning Aside:

In the fight between you, the world and blight, back the blight.

PotatoLateCycleFrom : ‘Mrs. Murphy’s Laws of Gardening’ – Faith Hines (Temple House books, 1992)

Old School Gardener

 

ornamental bug hotels

I love these ornamental bug hotels!

Old School Gardener

soil fungusToday is ‘Anti Biotics Awareness Day’ in the UK (I think this extends to the whole week in north America). Last night I attended a fascinating series of talks about work being done in the Norwich Research Park (this includes the University of East Anglia, John Innes Centre, Institute of Food Research and Norfolk and Norwich Hospital) to search for ways to expand the options for combatting infectious diseases. 

The Problem

‘Antibiotics are used to treat bacterial infections in humans. Even though these antibiotics are very powerful, some pathogenic bacteria have evolved resistance to all antibiotics currently available. There is an urgent need to find new ways to combat these drug resistant bacteria.’

268044-medicinesSolutions?

Most of the antibiotics we currently use are made by a group of benign soil bacteria called actinomycetes. Scientists are now searching environments not previously investigated to find new actinomycetes which might produce new antibiotics; for example deep oceans, desert, rainforests and insects. They are also manipulating actinomycetes bacteria to produce new antibiotics.

This is the first strand of work I heard about last night. It also featured a fascinating look at leaf cutter ants. You’ve probably seen these minute creatures on nature documentaries. They cut pieces of leaf from nearby plants and take these back to their nest. But they don’t eat the leaves, well not directly anyway. Instead they feed them to a fungus which produces the food they use. A sort of ‘agriculture’ that has been going on for 50 million years! It’s this fungus that scientists are studying, and specifically the antibiotics it produces, to see if they could be useful against human diseases.

The second strand of work concerns improving the diagnosis and use of antibiotics. Up to now we’ve been rather profligate with our use of antibiotics, including in animal husbandry (where they encourage weight gain) and agriculture.

This widespread use of antibiotics has led to the crisis we now face- many bacteria developing resistance to ‘broad spectrum’ (a cocktail) of antibiotics and a lack of will to develop new antibiotics as the investment and risk are judged to be too high in relation to the potential returns by pharmaceutical companies. The technology available for analysing bacterial infections is advancing – the speed is increasing and the costs reducing-  so that it is increasingly likely that a more precise diagnosis of infections can be made and a more targeted approach to using antibiotics can follow. This will both increase the effectiveness of their use and reduce the side effects- of killing off a lot of other (beneficial) bacteria and inducing the development of resistant pathogens.

penicillium_coloniesFinally,  I heard about work being done to harness the inherent bacteriological power of the human body.

Not only are humans walking factories of millions of bacteria, but it turns out that different parts of the body carry different bacteriological ‘eco systems’ of their own. The work to date has revealed the benefit of human breast milk in child development (as well as containing nutrients it transfers a range of bacteria from the mother which help to develop the child’s own bacterial systems). This has included giving ‘pro biotic’ supplements to babies born prematurely to help them make up the deficit they have on full term babies and so helping to reduce infections and premature mortality.

Work is also being done on the human gut and experiments with some very sick patients have shown how powerful an infusion of new bacteria can be in combatting diseases; this infusion takes the form of a ‘faecal transplant’- literally transfusing a healthy person’s gut bacteria to a sick person via their faeces (of course converted into a suitable form!).

On this special day, it’s encouraging to see the work in hand by a wide range of brilliant people (who happen to be on my doorstep) to try to extend our ability to fight infectious diseases. Part of the answer lies in discovering and teasing out new anti biotics from a wider range of soils and other sites, but it seems that better targetting of antibiotics and harnessing the body’s own ‘bacteria factory’ have an important part to play.

To finish, here’s a little quiz about leaf cutter ants…

Further information:

Antibiotic Hunters

BBC News Report

John Innes Ant Cam- live

Old School Gardener

 

I recently had a ‘tweet’ from fellow Norfolk resident, Claire in Thetford. She was wondering what the growths on these leaves were.

I must admit to being a bit puzzled at first, but some further research suggested that they are some sort of Gall, which Wikipedia describes as:

‘…abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites. Plant galls are often highly organized structures and because of this the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite plant galls.’

My guess from the pictures was that these were galls possibly created by some sort of parasitic wasp (in this case on the leaves of a Lime Tree). Claire’s own research came up with a more precise description: a ‘Nail Gall’ formed by a small mite Eriophyes tiliae. These microscopic mites overwinter in the bark of lime trees and crawl on to the underside of the foliage in spring to feed. The mites secrete chemicals into the leaves causing them to produce the unusual projections into which the mites move to continue feeding during the summer. Infestations of mites and the nail galls they induce don’t appear to affect the health of the trees and there’s no way of controlling or preventing them. The galls caused by this mite are said to be yellow-green or red in colour (see picture below). It may be that the whitish nails in Claire’s picture have been be caused by another mite (Aceria lateannulatus), which affects both the small-leaved lime (Tilia cordata) and the Common Lime (Tilia x europaeus), but not the large-leaved lime (Tilia platyphyllos).

Nail Galls cauised by Eriophyes tiliae

Nail Galls cauised by Eriophyes tiliae

Galls are fascinating phenomena. As Wikipedia continues, those created by insects are:

‘…highly distinctive plant structures formed by some herbivorous insects as their own microhabitats. They are plant tissue which is controlled by the insect. Galls act as both the habitat and food source for the maker of the gall. The interior of a gall can contain edible nutritious starch and other tissues. Some galls act as “physiologic sinks”, concentrating resources in the gall from the surrounding plant parts. Galls may also provide the insect with physical protection from predators.

Insect galls are usually induced by chemicals injected by the larvae or the adults of the insects into the plants, and possibly mechanical damage. After the galls are formed, the larvae develop inside until fully grown, when they leave. In order to form galls, the insects must seize the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.

The meristems, where plant cell division occurs, are the usual sites of galls, though insect galls can be found on other parts of the plant, such as the leaves, stalks,branches, buds, roots and even flowers and fruits. Gall-inducing insects are usually species-specific and sometimes tissue-specific on the plants they gall.’

Galls are also caused by fungi, bacteria, viruses and nematodes. It seems that in many instances these growths do not cause any significant harm to the plants they infest, though in some cases long term harm can be caused to some species, for example by affecting their overall shape and vigour.

Crown Gall on apple- RHS

Crown Gall on apple- RHS

Crown gall affects a wide array of plants and roses are definitely one of them. It is a plant disorder caused by the bacterium Agrobacterium tumefaciens, that interferes with the plants ability to take up water and nutrients. This results in poor growth and weak plants that are easily stressed and injured- the only remedy in this case is to dig up the plant and dispose of it.

The study of plant galls is called cecidology. While these weird structures have intrigued humans for many years, there is still much that we don’t know about them.

Wiches Broom Gall - picture Rosser1954

Wiches Broom Gall – picture Rosser1954

While some galls are well hidden and hard to spot, others are much more conspicuous. Have you ever looked up into a birch tree (Betula spp.) and noticed what looked like large, dense birds’ nests? In some cases these may well be nests, but very often they are actually galls called ‘witches’ brooms’. These are caused by a fungus (Taphrina betulina), which stimulates the tree to produce numerous extra shoots, resulting in a dense nest-like cluster. The fungus can then feed on the shoots. It was once believed that they were caused by witches flying over the tree!

If you spot an odd-looking growth on a dog rose (Rosa canina) it could well be a Robin’s pincushion gall, caused by a wasp (Diplolepis rosae). There was once a belief in England that these were caused by the woodland sprite, Robin Goodfellow or Puck. It is hardly surprising that people ascribed supernatural causes to some galls – they look pretty strange, and their causes aren’t exactly obvious.

'Robins Pincushion' gall on a Wild rose

‘Robins Pincushion’ gall on a Wild rose

The real gall specialists include gall midges, gall flies and gall wasps. Perhaps one of the most familiar galls is the oak apple, caused by a tiny wasp (Biorhiza pallida).

Oak apples

Oak apples

There are actually hundreds of species of oak gall wasps and they cause a fantastic variety of galls on oaks (Quercus spp.). A single oak tree may support many thousands of galls. Each gall wasp species creates its own unique and outlandish structure: some resemble cotton wool or marbles, pineapples or tiny UFOs!

Here’s a gallery of some of the other amazing galls to be found.

This slideshow requires JavaScript.

Sources and further information:

Galls- Wikipedia

Eriphyes tiliae- Wikipedia

British Plant Gall Society

Trees for Life- Galls

RHS- Crown Gall

Old School Gardener

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