Neil Paur <[EMAIL PROTECTED]> spaketh thusly:
>I was curious if anyone has had any real luck controlling red spider
>and two spotted mites with predatory insects such as Phytoseiulus
>persimilis? I have a small (12X12) greenhouse and total coverage
>with a chemical such as Avid is difficult.
>
>I do realize that once introduced spraying with a typical broad
>spectrum insecticide kills everything, so it's somewhat of a single
>shot control.
Back when I was making frankenplants, we had to use preds
rather than pesticides as the plants were meant to be fed to critters
later. We used persimilis from a company in Canada that sold these
little cuties. As with most predatory bugs, control is possible but
eradication is unlikely.
My take on the whole thing is that larger greenhouses tend
to be more stable than smaller ones in terms of pest control,
provided there are *some* natural controls lingering about. When we
broadcast chemical controls, we kill predators as well as the pests,
which really throws things out of whack as it puts the predators
behind the ball- there are fewer of them, and they tend to multiply
more slowly. Net result: you have to spray again. It's a pretty
savage circle, eventually leading to pesticide resistance. One of the
more clever controls for aphids involves the use of feeder colonies
of wheat aphids; buckets of wheat are grown here and there in the
greenhouse, infested with a wheat aphid that feeds ONLY on the wheat.
Then the predators- I forget which predator is used most favorably-
always has something to feed on. When another species of aphid takes
hold, there are good, thriving populations of predators actively
hunting in the greenhouse- no need to buy more.
This is, in a way, one reason I think mites are commonly
seen as being most successful in dry, warm conditions: these
conditions are detrimental to the predators moreso than the mites.
Isobyl La Croix notes in her excellent book on African orchids that
she and her husband (an entomologist) have observed mites living on
their plants with the worst cases often being those showing up right
in front of their humidifier (African Orchids in the Wild and in
Cultivation, page 63). What's happened is not that the mites have
exploded because of the dry air, but because the predators have been
stressed or decimated by the conditions, allowing mites to thrive;
this may be exacerbated through the use of chemical pesticides
effecting the population of predators, as above.
She also notes that persimilis has proven effective in their
greenhouses.
As an aside, I've used Talstar once or twice with good
results in grow chambers too small to reasonably support the use of predators.
Cheers,
-AJHicks
Chandler, AZ
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