Things are rarely simple, and that's how it is with aphids. It helps to think of them as little green sap collectors for ants. Ants, you may remember, had decided that the polytunnel was the party tent for the allotment, so we have already removed 3 nests, but they still seem to be getting in from somewhere. The result is that you remove the aphids from the plants (literally rubbing them all off by hand), spray the plant with a washing up liquid and oil solution to at least annoy any remaining aphids, and then return the next morning to find that the ants have replaced them, because surely not even aphids can breed as fast as that...
We've tried putting some ladybirds into the polytunnel, but their numbers aren't high enough yet, and our experience is that it's the babies that really get to grips with the aphids, so they probably aren't going to do the job quickly enough.
|Guy checks the tomatoes for aphids|
So what to do now? Well, we have already decided to use our unplanted peppers and chillis as lure-plants, because we know they seem to get covered in aphids when other plants aren't affected, and they have already become sad little specimens. These have been put in the empty area which is awaiting the later planting of tomatoes to lengthen the season. Another trick is to put something reflective under the plants. This apparently upsets the aphids, as they normally prefer to be under the leaf on the shaded side, and the reflected light confuses them. In trials, plants with reflective mulches under them apparently had only 15% of the aphids found on un-mulched plants. Not sure if it will help in our trial, but we can tell you that after 1 day, we had some plants with aphids on the top side of some leaves, rather than on the bottom. Finally, we've introduced french marigolds into some parts of the tunnel. Our experience of these is that the aphids rush onto them, though some friends swear that they repel aphids. We'll see which of these is true this time, but we just hope they work!
|Our pie-tin reflector system|
|We'll see if it works...|
We'll keep you posted as to whether this works. Our next stop will be introducing predatory wasps...