GardenBanter.co.uk - Leaf miners yet again

On 7/17/11 2:26 PM, Paul M. Cook wrote:
So I pulled up many of my third panting of cucurbits. The leaf miners
destroyed them in the cotyledon stage for the second time now. Even
spinosad applied heavily could not stop them. I have no idea why this is a
new problem as the last two years were free of this problem. So no
cucumbers for me this year. No melons either. Is there some product like a
transparent tent that would kep the flies off the seedlings? Looking for
ideas for next year.

This might start a flame war, but I know how to set filters in my
newsreader and will do so if necessary.

There is a systemic insecticide called imidacloprid, which is sold under
various brand names. This is NOT approved for use on edibles. However,
research indicates it is not harmful to mammals, including humans.

I use imidacloprid on my dwarf citrus when I first see any damage from
the citrus leafminer. (No, I do not make any preventative treatment,
only a curative treatment.) I mix a measured amount into a gallon of
water. Then, I drench the soil around the infected tree. One treatment
lasts about a year.

For my dwarf citrus, it takes about 2-3 weeks for control to begin.
After control begins, damaged foliage remains damaged; but new foliage
escapes damage.

I have also used imidacloprid on house plants in my breakfast room
greenhouse window. It did a good job of eliminating scale.

I'm not sure how much imidacloprid would be needed for a bed of
cucurbits. Being fast growing annuals, I would expect control to begin
after only 1-2 weeks.

If you use imidacloprid, be sure that the drench soaks completely into
the soil. In the summer, bees sometimes need to take up water to
prevent their honey from crystalizing. Imidacloprid is definitely toxic
to bees, so you must avoid leaving the drench as a standing puddle in
your cucurbit bed.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary