Tag Archive: insects


Old School Gardener

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2-Calendula

A useful article by Andrew McIndoe on companion planting- find it here.

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

 

 

bug hotel cutteslowe and sunnymead park, oxfordBug hotel in Cutteslow and Sunnymead Park, Oxford

Old School Gardener

vines in california with pollinators kenwood winery

Vines at Kenwood Winery, California, with an  alley of pollinating plants

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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I featured a range of ‘hotels for the discerning’ earlier this year, and here are a few more ideas for desirable residences for the bugs you want in your garden.

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Hotels for the Discerning #5

5 star comfort

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Hotels for the Discerning #4

Multi Storey hotel

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Hotels for the Discerning #2

Royal Horticultural Society – School Gardening Bug Hotel

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