I've seen various articles/posts to say that decoy artificial white butterflies, such as the one I just made, are effective in preventing attack of brassicas by the white butterfly Pieris rapae. The thesis is that the insect is highly territorial and will fly off if it sees a competitor. But are these reports just publication bias or does it really work? I'm looking for controlled studies. white butterfly decoy


They do not help at all. The presence of another butterfly will often attract these, and you will often see numbers of them visiting the same plants. Even when finding a spot to lay eggs. They avoid a spot that has another butterfly on it (because of caterpillar food competition), but it really doesn't stop them from taking advantage of the plants. My neighbor used decoys similar, and reported absolutely no difference.

He said the plants near the decoys took the same hit as the ones further off. And that didn't surprise me at all. I think a better option would be to cover the plant(s) with floating row cover or similar.

  • I need to do the experiment again. The choy sum on the left has had a number of eggs laid on it, but the bok choy on the right has had none. Either the decoy has prevented the egg laying behavior, or, the choy sum is a preferred plant. My other bok choy in the garden are getting attacked. So, I need to put two plants of similar size near each other with one with a decoy. – Graham Chiu Feb 11 '16 at 8:13
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    I'm now thinking that they don't work because pieris rapae eyes operate in the uv spectrum, and the patterns on their wings have a particular UV signaI which is not reproduced with a simplistic drawing. I need to capture some butterflies and embed them in an epoxy resin to see if they can be recognised. – Graham Chiu Jan 19 '18 at 9:05
  • @GrahamChiu Have ever you tried placing bread clips (the plastic ties on bread bags) around some of the branches of the affected or nearby plants? – init_js Feb 6 '18 at 23:14
  • Nope, what's supposed to happen? – Graham Chiu Feb 7 '18 at 5:32

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