Blue sticky fly traps

[Paul D]

I've used both yellow and pale blue sticky fly papers to keep an eye on things in the greenhouse, both quite successful. I've just received a pack of blue ones bought from Amazon, but surprised to see they are dark blue in colour. Made in China. Are dark blue ones at all effective? Should I send them back? Intuition suggests dark blue is not going to be attractive to thrips :/

[el48tel]

"Intuition suggests dark blue is not going to be attractive to thrips" -- an interesting hypothesis. I'd contemplated purchasing other colours to the yellow variety since the yellow ones in my greenhouse are already looking like the full specimen cabinets at the Natural History Museum, and I'd read that the yellow sheets caught insects "selectively". Insects see wavelengths of light other than the visible, and the reflectance of the sheets you describe may be in the near UV -- is a spectral data sheet available from the supplier?

[Paul D]

I appreciate that insects see a different spectrum- it was the darkness of the shade that I wasn't expecting (i.e. not reflecting as much light). But, as you say, perhaps they reflect outside the visible spectrum. Has anyone here used dark blue traps successfully?

[juster]

Sorry Paul, I have used both yellow and pale blue, but have never seen them in dark blue.

[Geoff Lovell]

I catch all I want to with yellow.

[Terry S.]

Blue traps are more attractive than yellow for Western Flower Thrips. However, the ones that I have used in the past were more of a mid-blue than a dark blue.

[topsy]

Hi Paul,

You may as well try them as you have them. They will probably fade in the sunlight quite quickly and become the shade of blue we are more used to.

Suzanne

[Ali Baba]

I now only use blue sticky traps in my greenhouse in the winter when the vents are closed but WFT are still very active. Blue attracts several species of native bees, and I don't like seeing them trapped

[MikeDom]

The reason for yellow (which I read many years ago) is that insects see yellow as new plant growth and are attracted to it. In one of my greenhouses I had a whitefly infestation on my caudiciform pelargoniums and bought encarsia wasps to eradicate the whitefly. As the wasps are only a millimetre or so in size, I put a fine bright yellow insect net across the door to keep the encarsia from escaping. As I was putting the net up, whitefly were coming off the plants and sitting on the net. Luckily the encarsia did their job; no more whitefly.