Sunday, April 30

Matriarchal society aphid style

We have begun our battle with the battalions of gardening saboteurs. The slugs and snails have munched their way through lettuce seedling and the mice have dug up the sweet pea seeds.

The next battalion to move in will no doubt be made up of some members of the 500 species of aphids found in Britain. Commonly called greenfly they actually come in an array of colours, green, pink black, white and no doubt other colours too. Many are visible on our plants and other lurk underground feeding on roots.
At this time of year eggs that have overwintered hatch. The hatching is well timed to take advantage of the emergence of tasty new shoots. In also coincides with the time that the birds are hunting for insect food for nestlings, just one good reason for not resorting to spraying. Early greenfly colonies on our roses are made short work of by our garden allies. We often see birds foraging for aphids in the branches of the fruit trees on the plot too.
The newly hatched aphids or nymphs are all females and are just smaller versions of their mothers. As with other insects as the nymphs grow they shed their skins. A week after birth they are fully mature and capable of reproducing. They do this without any need to mate. In some species aphids are actually born already carrying another generation.
The females can give birth to five live young each day for a period of about thirty days so it is easy to understand why infestations build up so quickly. If all offspring survived, a single female could be responsible for a line of aphids 27,950 miles long,

If a food supply is no longer capable of sustaining the colony, it triggers the production of winged females. These individuals are not capable of strong flight but can be carried long distances on the wind. When they land on a suitable food supply they will start a new colony.
The cycle continues all summer until temperatures fall. Around October, winged males are produced. Their only purpose is to mate with winged females. Once mated the females deposit eggs in a safe place to overwinter and so the circle is completed until the following spring when it all starts again.

Aphids belong to the bug family and feed by piercing the plant with a feeding tube through which they draw sap from the plant. Feeding aphids can cause leaves and buds to become deformed and they can also transmit viruses and disease from one plant to another.
Aphids ingest more sugar than they need and any excess is passed out through two tubes at their rear end. This sugary substance or honeydew causes plant leaves to become sticky and forms an ideal feeding site for sooty mould which coats the surface of the leaves with a black fungus. Although the fungus doesn't harm the plant it does stop light reaching the leaves and prevents the plant from producing food.The overall result of an aphid infestation is a weak and struggling plant.
Aphids do have an unlikely ally. Ants love the honeydew produced by aphids and will protect aphids from their enemies so that they can maintain a flock of honeydew producers. Some ants even farm aphids but that's another story. 

Fortunately we have many allies in our war against aphids so we need to take care that our attempts to control aphids don't inadvertently harm our garden friends.
If you are interested I have written on aphids in a little more detail on our website here.




24 comments:

  1. Oh, I hope our late frost helps reduce some of those numbers this year! Great macro shots by the way

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    1. I'm guessing that the frost will have had no or little effect, Belinda considering that they seem to survive much worse conditions.

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  2. Goodness, they're horrible things when you see them up close like that, great photos.

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    1. They are horrible things all the time. Jo.

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  3. A fascinating post Sue, with fantastic photos. Somehow the winged ones make their way into the house and on to my windowsill seedlings, it always surprises me. There are some good clusters building up on the roses out there at the moment. The birds are doing their best though, we have had an amazing amount of bird life in the garden this past couple of weeks.

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    1. We get then on out houseplants too CJ. I don't know whether they come through open windows or migrate from cut flowers on new plants which could harbour eggs.

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  4. What a wonderful post - so many details I had no idea about. Aphids aren't too much of an issue here (knock on wood!). We do get a few on the favas and I also had issues when trying to grow Mei Qing Choi later in the season but that's about it. Without the benefit of all those wonderful predators, however, it's a different story - when I tried to overwinter peppers, yikes - they took over! I had to get rid of the plants and haven't made an attempt at that since.

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    1. Once they take hold, they are difficult to get rid of Margaret.

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  5. Oh I didn't realise the number of species of aphids in Britain Sue. I somewhat naively thought that there were whitefly, greenfly and black fly :) Good luck with the battle to keep their numbers down. Here I've been red lily beetle hunting today.

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    1. Until I read up on them, I had no idea either, Anna. What's more they can switch food plants which makes them even more impossible to control.

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  6. What an interesting post, I did enjoy it. I'm amazed at your photos given how tiny these creatures are. They are smothering my roses at the moment.xxx

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    1. The tits in the garden seem ti make a good job of clearing the roses, Dina. They do get greenfly but if we leave them they disappear and I'm pretty sure that this is courtesy of foraging birds.

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  7. After slugs, I think aphids are the biggest threat to my veggies. I'm sad that no Bluetits have used our nesting-box this year (they fought over it with some Sparrows, but in the end neither moved in), so I won't have their help in keeping the aphids in check.

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    1. The only positive, Mark is that the birds must just be overwhelmed by choice of nesting sites. Our nest box with webcam is empty again so I am wondering whether there is something about it that they don't like. Even if they don't nest maybe they will come to feed.

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  8. A most informative post. Thanks Sue. I feel so much better about not doing anything a rash of blackfly that erupted on a random campion in our hedge at home - Although now I realise it might be at the sooty mould stage!

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    1. You could just blast them with a jet of water, Mal

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  9. Great post Sue! Aphids are a year round pest in my mild climate, a constant battle. My first line of defense is to grow flowers that will attract the critters that will help battle them. I let sweet alyssum grow all around the garden and let fennel, coriander, carrots, and parsley volunteer and bloom around the garden as well. The result is lots of hover flies (flower flies) and parasitic wasps that will lay their eggs on and near the aphids. It's amazing how many aphids a few hover fly larvae can eat.

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    1. Rallying the troops, Michelle. We grow lots of flowers on our plot too.

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  10. Horrible little blighters! They have arrived here too, and so have the ants but the ladybirds are small in numbers still. I also see the birds nipping at the branches so I am hoping they will keep them in check for now. Great post Sue and lovely photos even if they are a bit yucky!

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    1. We have had a lot of ladybirds, Helene all busy procreating. At least the aphids provide the birds with fresh food.

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  11. The overwhelming numbers of aphids on my sweet peas last year were the reason that I couldn't pick any for indoors, or offer flowers to my neighbours. They were all over the tulips as well but don't seem to be so bad this year, although I saw a few on the tulips recently. Sparrows and blue tits have a feast on them in the fruit trees here.

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    1. I hope that you have better luck with sweet peas this year, Caro.

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  12. Aphids use to attack my yard long beans in the past! How you tackle them? with natural way of predator?

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    1. We use various methods to minimise them, Malar. The predators help so if we do have to resort to a spray we use something that won't harm them. Otherwise I may use a soft tissue or similar and rub and squish them off. We may fire water jets at them and we also cover things lie brassicas with mesh. I've also been known to carry ladybirds to plants with lots aphids.

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