In a message dated 5/23/07 3:02:03 AM Pacific Daylight Time, [EMAIL PROTECTED] writes:
> "I am wondering what you all do about boisduval scale." I have had acceptable results (I say acceptable because the scale always reappeared within a year of application, implying they were not entirely eradicated) with three methods in a 16' x 25' intermediate greenhouse I was taking care of for several years. The collection was mostly Cattleyas, Dendrobiums (Formosae and Latouria types, with some other sections thrown in), Phrags, Oncidiums, and some misc. genera. The greenhouse was overcrowded (as so many hobby greenhouses are). And despite instruction, the owners insisted on watering way too frequently. I believe these two things contributed to the spread of the scale (especially on the Cattleyas). On one occasion I used Orthene aerosol total release cans. This really needs to be done late in the day when the vents have closed or the exhaust fan shut off (but with circulation fans going). There was no damage to foliage or flowers. I have also used Orthene wettable powder to which a small amount of dish detergent was added. The advantage here is that spray can be directed specifically to the undersides of the leaves and the rhizome where populations of the scale are heaviest. The disadvantage is that plants should be removed from the greenhouse (you really don't want to apply Orthene in an enclosed environment even with a respirator and protective garments). Here as well there was no damage to plants or flowers. Finally I have used light horticultural oil. This needed really thorough application, and had to be done three times (as opposed to twice with Orthene). It also damaged flowers and the foliage on some plants (a few Cattleyas, but a significant number of Dendrobiums). All three methods seemed to provide control. But as mentioned above, infestation reappeared within a year. I think that once you have had Boisduval scale on your collection, a complete spraying of the greenhouse should be done twice a year, whether you see the pests or not. Dennis ************************************** See what's free at http://www.aol.com. _______________________________________________ the OrchidGuide Digest (OGD) orchids@orchidguide.com http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
