Dealing with pesticides is a difficult issue since often safest and most effective are not available to the home gardener.
As for boisduval scale - a strong water jet to dislodge the insects will help control large infections - removal of the insects and their bodies is imporant. even though the adults may be dead if the colonies remain there can be thousands of eggs to replace them. In severe infections the layers of boisduval are so dense that they protect many of the adults from being killed by insecticides. I use an on-off valve just barely opened to create a fine jet of water to remove the scale insects. Peeling back sheaths on Cattleyas and really working in all the nooks and joints of the leaves is important. Of course its best to do this outside the growing area. 1-2% solution of horticultural oil works best after that for good contact kill. Of course you must be careful of hort oil in high temperatures as it can smother the plants and cause them to burn as well. The best insecticide i have found for Boisduval scale is an insect growth regulator called Distance. It is trans-laminar (working through the leaf) and I have used it with phenomenal results in a very large mixed genera collection with no ill effects to the plants. I have heard that in very high concentrations and repeated applications it can cause floral deformities in developing buds. marc _______________________________________________ the OrchidGuide Digest (OGD) orchids@orchidguide.com http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
