Aphid Attack!

, written by Jeremy Dore gb flag

Aphids on lettuce

It is around this time of year that pests seem to appear from nowhere in the garden.  Of all the insects that suddenly spring up, aphids are the ones that always take me by surprise – within a matter of days plants can be covered with one of the various varieties of them: whitefly, greenfly, blackfly, mealy aphids and root aphids.  So just how serious is it when your garden comes under attack and what can be done to counter such an invasion?

Aphids are interesting pests because there is such a diversity of opinion on them.  There are a few facts that everyone agrees on:

  • Most aphids live on or under the leaves of plants, piercing them and extracting sap, which can cause leaves to deform or curl up .
  • Grey-white root aphids, on the other hand, live in the soil and can attack plants causing them to suddenly wilt and die.
  • Aphids can transmit mosaic virus to plants, which turns the leaves a mottled yellow colour and stunts growth.
  • They excrete a sticky honeydew on plants that can be home to sooty molds, blocking the leaf pores.  This is why ants actually farm aphids, protecting their eggs over winter and carrying the hatched aphids to plants so that they can feed from the honeydew they produce.

Despite these facts there is far less agreement on how serious aphids attacks are, or how to treat them:

  • Some organic gardeners believe that aphid attacks are simply a sign of weak plants and that good organic cultivation should prevent most serious consequences.  Charles Dowding writes in his book ‘Salad Leaves for all Seasons’: ‘Severe infestations of aphids often point to plants that are unhealthy and are an indicator to the gardener that something is not quite right, for example that the soil is too dry, or the plant is growing out of season.  He recommends simply using water to reduce their numbers and encouraging predators such as ladybugs.
  • Others suggest spraying aphids as soon as they are spotted with insecticide such as pyrethrum, derris (now banned under EU regulation) or soft soap solutions (although insecticidal soap is also banned).  To be effective these sprays have to actually land on the aphids themselves and this is the main problem – aphids usually populate the most inaccessible parts of the plants: in between and underneath leaves.  It is therefore very difficult to actually treat all the aphids and numbers can rapidly increase again.
  • Simply picking aphids off plants, or squashing them, can be a simple but effective means of keeping numbers down.  I have even heard of gardeners who use a vacuum cleaner to suck them off leaves but that might be taking things a bit far!

I tend to agree with the ‘let them be’ approach – in a well managed garden where crops are rotated aphids can usually be controlled by good companion planting to encourage predators such as lacewings, hoverflies and ladybugs.   I don’t mind having to wash off a few aphids before eating produce from my garden and I am prepared to lose the odd plant in preference to using sprays. 

However, there are occasions when the unexpected happens: we recently had over a week of dry weather with high temperatures and little rain which was quite unusual for the end of spring in Northern England.  Unfortunately the companion plants I usually plant to draw in predators had not yet flowered - poached egg plant (Limnanthes douglasii), marigold (Tagetes) and dwarf morning glory (Convolvulus tricolor). Suddenly I got an attack of several aphid varieties in my salad bed: greenfly and whitefly on the leaves and three or four lettuces just suddenly wilting from root aphid attacks.  So currently I am spraying them with plenty of water and keeping a close eye on the situation.

In my opinion organic pest control is all about balance.  It is always tempting to get out a spray or take drastic action but I think it is more important to try and prevent attacks with good garden management and concede the occasional loss to nature.  Aphids are one of those grey areas – they rarely kill plants so I can live with a few of them, work to control them and take measures to ensure that they don’t get out of control.  To my mind that is much better than spraying the salad which will end up on my plate in a few days’ time.  Aphids are resilient pests and using nature’s own predators to fight them is the best weapon available to the organic gardener.  I just wish those ladybugs would hurry up and do their job of guarding my garden...

If you have any tips for dealing with aphids then please do add them below...

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Show Comments


"Hi Jeremy...Whenever I see too many ants on any plant or veggie in my garden I can pretty much expect there to be aphids. I always hose them off with a strong spray of water, never insecticidal sprays. That seems to control them somewhat. It seems to me the ants are as much if not more of a problem than the aphids so it's forever war on the ants that protect them so the beneficial insects can have themselves a field day. Good composted soil has made a big difference in my garden but stopping the love affair between ants and aphids is still the biggest challenge. "
Sharon on Saturday 13 June 2009
"Sharon - Yes, I should have mentioned that ants really hate water, so spraying with water regularly really helps to keep them down. They usually just move elsewhere but that's fine as long as they are not farming the aphids as you mention."
Jeremy Dore on Saturday 13 June 2009
"Hi my garden seems to be doing fine, except my basil is being eaten and cannot figure it out, i have marigolds planted, a variety of other herbs, tomatoes, etc. what like basil? thanks"
naomi on Sunday 28 June 2009
"Naomi, The most common cause of seedlings being eaten (including basil) is slugs, so I suggest you take a look at our GrowBlog article on slugs (http://www.growveg.com/growblogpost.aspx?id=28), put down some slug beer traps and perhaps do some checks with a torch at dusk."
Jeremy Dore on Monday 29 June 2009
"Update on this article: since publishing it the national press in the UK has confirmed that we have had the worst plague of greenfly for 25 years in Britain (see http://www.express.co.uk/posts/view/111040/Hot-spell-attracts-the-green-invaders). So since the numbers of greenfly are well under control in my garden now, I think the organic methods worked pretty well."
Jeremy Dore on Wednesday 1 July 2009
"thanks, jeremy i just put ladybugs in last night, i will get some beer, do i have to put the beer all over the garden or just what is being eaten, "
naomi on Wednesday 1 July 2009
"Naomi, The beer goes in slightly sunken pots or plant saucers (at least an inch deep). The edge should be about a half inch above soil level (to prevent good insects like beetles falling in) near to the crops you want to protect. You can get slug traps which do a slightly better job from most garden suppliers."
Jeremy Dore on Wednesday 1 July 2009
"can i still use soil to re-pot plant that is previously infested with aphids? I have about 5 gallons of black soil which is used for corn plant..."
aldwin on Wednesday 12 October 2011
"Some aphids (e.g. lettuce root aphid) do overwinter in soil so I would have reservations about using that soil for crops that suffer aphid damage. You could of course bury the soil so plants get the benefit but aphids can't hatch out."
Jeremy Dore on Wednesday 12 October 2011
"I have container garden with variety of ornamental, flowering and veg plants on my porche. one container has a small marigold plant which looks very healthy and suddenly i saw the leaves twisted. i saw aphids. killed some but the ants are still going round even with wood ash sprinkle and water. i am scared the marigold plant will get damaged. any suggestions. i use organic kitchen waste compost for the pots."
platty on Monday 5 May 2014
"Thanks for sharing the pointers. Aphids are the bane of my existence. I'm using a spray that I made with cayenne pepper, dish soap, and threw in a clove of garlic. Smells horrible, makes me cough when I spray but it does the trick. I also added some aluminum foil to see if this trick works: http://typearamblings.blogspot.ca/2014/05/patio-gardening-reflective-mulch.html Has anyone tried this method and found success with it?"
Pam on Thursday 29 May 2014
"Will my vegetables grow back after ants have eaten all the leaves off the young plants....new gardener here. Thanks!"
deanna on Tuesday 31 March 2015
"Good article. This past summer was the first time I've started an urban garden. The ants ??, and subsequent aphids, were a real battle for me! They completely destroyed my bean plants, and I've always had good success with them everywhere else that I've lived. Having said that, we DID have a serious drought, lasting 5 months, so maybe that explains the over abundance of ants. I was afraid that it was an urban problem. I now have a very tiny garden, so can't afford to be nice, and lose my crops. I've planted plenty of predator attracting flowers, but saw only one ladybird. Again, perhaps an urban problem. Then again, I think I've started the first garden ever in this garden. Fingers crossed for net year. "
Nancy on Sunday 27 November 2016
"'next' year"
Nancy on Sunday 27 November 2016

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