Boisduval scale or as I like to call it "Coconut scale" (because it looks like sprinkled desiccated coconut) is easily the worst and most difficult pest to control.
Even when dead, it still looks alive and confuses the poor orchid grower.
It seems to effect Cattleya alliance orchids most often, but also enjoys giving Australian Dendrobiums a good infestation.
At “The Australian Orchid Nursery" we don’t have Coconut scale, its only when we buy in new stock or purchase rarities from old collections that it sneaks back in.
This is the reason for this article is because a highly valuable breed stock orchid 'Dendrobium Jazz 'Windsor Downs'' just turned up with two badly infested leaves as seen in the photos added.
For control we use Confidor and Confidor or Initiator Pills tablets. click below to veiw and purchase
Secondly we spray heavily with Diazanon.
This gives us total control.
WE don’t use or recommend Oils such as Eco Oil and or White or summer oils, due to the damage that may occur n the warmer months.
Also a great tip. Scrub off the old dead scale using a stiff toothbrush and a little soapy water. Cant tell if they are alive or dead unless you remove the controlled dead ones.
(From Orchids -World) The damage is not restricted to one place. Boisduval scales can be found in the leaf axils, hidden under sheaths, under new leaves, close to the ground near the roots, on pseudo bulbs, bark, aerial portions of the plant, etc.
When you notice leaves with yellow stains if you lift the leave, under the leave you will notice a “white messy looking mass” of Boisduval scale. A colony of thousands of nymphs, is ready to desiccate your orchids. Often you can recognize the adult males and females. All orchids are attacked: Brassias, Bulbophyllums, Cattleyas, Cymbidiums, Dendrobiums, Encyclias, Epidendrums, Oncidiums, Vandas, etc.
If you get Boisduval Scale it is extremely difficult to get read of it. Some suggest to keep plants apart so that their leaves do not touch to stop “crawlers” moving from infested plants onto clean ones; however, that's not the answer.
The life cycle of scale is very brief. Scale moves from eggs, to the nymph stage called crawlers, to adults in the matter of a little less than two months, and there may be several generations of scale within a year.
These cycles are fastest in an indoor or greenhouse environment. As a result, management, once orchids have been infested, is very difficult.
The caretaker must be very persistent in his or her approach and must apply treatment at least every ten days. If you have been using the same treatment for more than a few months and still have scale problems, you must switch treatments as some of the scale may have become immune.
The scale is most easily treated during its crawler stage, this is also the stage when it moves between plants.
The last stage of the life cycle for a female scale is when it hardens and lays eggs under the protective covering that it is named for.
Once the eggs are laid and the shield is hard the scale dies