Question
I have recently discovered what appear to be eggs on my orchids, small black brown eggs on the petals and the leaves have a sticky residue on them. I have not seen any bugs on them.
What do you think the problem is. I am in the south of England, and the orchids are in my lounge and have previously thrived
Thanks and regards
ian swindells

Answer
Ian, good description of a sucking insect called "scale".  There are three principle stages in this insect's life cycle: egg, crawler, and adult.  You have described the adult stage.  The adult stage is where the name "scale" comes from as it is an apt description for this stage.  There are several types of scale insects.  You have the brown scale. The larval or crawer stage is not as easy to spot as its coloration matches plant tissue and it is soft.  The adult scale forms a hard hemispherical shell on the leaf.  It is the gg laying stage and the shell protects the soft cottony eggs.  Scales are one of the most common pests of orchids and can appear seemingly out of thin air and multiply quickly.  They live on the plant's sap which is sticky due to its sugar content.

Step one is to remove  this plant from the vicinity of all other plants.  Secondly, examine all other plants that have been near your infested orchid plant.  Look carefully for the somewhat transparent crawlers for those that move around and do most of the damage.  If you see any on any other plant, isolate and treat that plant the same as my suggestion for the orchid plant.

First treatment is to take a swab or cloth and soak it in 70% isopropyll alcohol (ie rubbing alcohol).  Do this to all leaf surfaces (top and bottom) so that none of the shells remain.  That is stage one.  Next locate a systemic insecticide that is appropriate for scale insects.  Your local garden center can be helpful in finding one for you.  Prepare a "drench" by mixing the proper proportions of insecticide in water.  Make enough of this solution so you can submerse you entire plant in the bucket containing the insecticidal solution (be sure to wear chemical glovew to avoid skin exposure).  Remove the plant from its pot and discard anl potting mix by bagging it and setting it outside.  If you wish to reuse the pot, it too will need to go into the drench.  Before placing the plant in the drench, rinse all potting mix from the plant's roots. Repot after a 30 minute drench.  Repot in fresh orchid potting mix and set aside to dry and air out.  You ay want to place the plant outside for a while becuase some of these insecticides have quite an odor.