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I suddenly have a mass of what I think are greenfly on my tomatoes in the polytunnel. (Actually on everything in the polytunnel) Do they do any harm? If so, what should I do? Washing up water?
Hi Kate, yes it is probably greenfly, because aphids are common just now and I have seen many less ladybirds than usual, to eat the aphids, could do with some!
Aphids are to some extent a sign of plants under stress from eg dry soil, wrong temperatures, weak variety or lack of ventilation. I have some in different parts of greenhouse and tunnel, for all those reasons! and am not too worried as they usually diminish as summer goes on, with predators arriving.
However if you have a lot and are concerned, you can spray soapy water, I have never done it and perhpas someone else can suggest a soap or other additive?
Actually not too much unless leaves and stems are really covered, in which case an itintial wash off is good, followed by soapy spray. Aphids suck sap, secrete a sticky and unpleasant "honeydew" which can lead to sooty mould, and attract ants who farm them.
I usually cut off a handful of the older leaves from around the bottom of the Tomato plants(as ironically tomato leaves are toxic to aphids), chop them up finely, sometimes adding a clove of garlic also finely chopped, I then tie it all up in a small piece of muslin and put it in a bucket with about a litre of water and leave it overnight. It is then ready to spray. As Charles has pointed out predatory insects will generally keep the numbers down and I mainly use this spray for younger seedlings or larger gatherings.
Hi Kate — Just posted a mix to spray them with which they hate. It is a ‘tea’ made from garlic, nettles, basil or wormwood. As slug hunter says the tomato leaves are loathed by them as well, I would chop up a ton of those too for good measure and add them to the brew.
Apparently the aphids suck the sap from the plant turning it into a sticky gloop which ants love as Charles said. I hope you can get rid of them before the ants locate them.
You could also catch any ladybirds you can find and put them on or near the plants effected. Each ladybird eats up to 400 aphids per day !
Good luck. Do let us know how you get on.
Very best wishes
Julie
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