Whitefly Plague

It’s been one of those weather weeks – doesn’t matter what the weatherman says, it’s either raining or, as happened on Wednesday, that windy that doing anything was tricky.


In the greenhouse everything continues to produce well but a few whitefly have become a plague. I know enough to know that with pests it’s best to act quickly but I haven’t done and now we’ve a right problem.

The reason to act quickly, by the way, is exponential growth. There’s an old story that illustrates this. A man saves the life of the king who offers him a reward. Anything he wants, gold, jewels, or whatever but the man just asks for some rice.

He says. “Oh King, just give me rice. Take your chess board and on the first square, place one grain. On the second, two grains and on the third, four grains. Just double it for each of the squares.”

The king agrees only to find that he has bankrupted the kingdom for on the 64th square he must place 9,223,372,036,854,775,808 grains of rice and on the board as a whole 18,446,744,073,709,551,615 grains of rice, weighing roughly 461 billion tons. That’s an awful lot of curry!

So, before we all die under the weight of whitefly I need to act. It’s a bit beyond yellow sticky cards now which leaves either using the biological control or a spray. I picked up an organic spray which kills on contact as there would be a delay on getting the biological whitefly control.

The first spray reduced them down by about 80% and the next day I sprayed again reducing them down to hardly noticeable. Oddly they’re not on the tomatoes as far as I can see but they love the peppers and aubergine.

On Thursday we went over to see my father-in-law so I took the opportunity to pop into Interhort near Crewe for some bonemeal and hoof and horn fertiliser. They do deliver but it seemed a bit daft to pay for a delivery when it only took us a couple of miles out of our way. I’m planning on planting quite a few fruit trees, which is what I wanted the fertilisers for.

I don’t suppose we’re alone in not really fancying salads when it’s cold and raining so our glut builds up. We’ve peppers, cucumbers, tomatoes, lettuce and radish enough to feed a vegetarian convention.

Hopefully the weather is improving and September will be nice.

Posted in Allotment Garden Diary
5 comments on “Whitefly Plague
  1. Colin says:

    I too have suffered a plague of greenhouse whitefly, chiefly on cucumbers but also on some climbing French beans (Algarve) that have done well in previous years.
    The only commercial spray I could find was ‘insecticidal soap’ (to use an unbranded description) that “offers a measure of control”. Being translated this means several costly spray bottles will reduce the number of whiteflies and coat your plants with a dirty deposit. The whiteflies then regroup and come back.
    A “grandmother’s” solution has helped temporarily (I must not mention it because the EU have proscribed it), but I would love to know the name of an organic kill-on-contact spray.

    • John Harrison says:

      @Colin: Bug Clear – but then I found Agralan which can be used in conjunction with biological controls (encarsia formosa wasps)

      Agralan also make yellow sticky cards which work to some degree once things are under control.

  2. Colin says:

    I have ordered Agrilan Whitefly spray and will comment on my results.

  3. Duncan Robinson says:

    I had masses of whitefly on the underside of the leaves of my ‘Invitation’ swedes. I have sprayed with permethrin twice and this seems to have knocked them back quite a bit. They haven’t touched the Medwyns Giant Cabbages a few feet away!

  4. Angela Hunt says:

    I have just learnt that Nicantra physalodes repel white fly going to try planting them with salad and beg next year be back to let you know if it works.

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