Geranium bronze butterfly

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tavira Tavira, Portugal Aug 22, 2014

I have been growing geraniums on the Algarve for some time. There is a plague of these butterflies, Cacyreus marshalli, which makes this very difficult. The product I was using, which was an insecticide stick you put in the earth every 3 months, has been withdrawn, and I cannot find a suitable substitute.
I would be very grateful for any suggestions. Thanks

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Diana_K Contra Costa County, CA(Zone 9b) Aug 22, 2014

If it is a true butterfly or moth then a product containing bacillus thuringiensis will highly likely work. This is a bacteria that is specific to the order Lepidoptera and kills the caterpillars when they eat it. Get it onto the plants early so the newly hatching caterpillars can take it in as they eat their way into the flower bud. If you wait too long the caterpillars are inside the flower bud where they cannot get enough of the bacteria to kill them.
B.t. is not effective against other insects (well, there is a different strain that works against mosquitos).

Also works: A screen over the plant so the butterflies cannot get to the plant to lay their eggs. If you have just a few plants you might build a bit of a tent around each one. Make sure the ends are secured (dig some soil over the edges so the butterflies cannot get in. If you are a commercial grower you might built a frame over all the beds where you raise these susceptible plants and mesh the whole thing.

OK, so they target the flower buds, not so much the leaves. Still, the screen should work. The timing on the pesticide will have to be very carefully matched to bud development. Keep the material active (the bacteria die soon when exposed to dry heat of a summer day) by frequent applications. Every few days.

http://www.cabi.org/isc/datasheet/10683

This message was edited Aug 22, 2014 5:47 PM

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tavira Tavira, Portugal Aug 24, 2014

Thanks for the helpful advice, Diana. I am not a commercial grower, I just have a lot of geraniums and pelargoniums, so cages and nets are not really for me. The worst affected by far are the ivy-
leaved, the pelargoniums not so much, and the cranesbills not at all.
I will certainly look into B.thur., althought summer is very hot here, 35 to 40C, so will have to use it more often. Thanks again.

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