Tuesday, April 23, 2013

Pest of the month: Brown Soft Scale

I recently found a new pest on one of my Ficus microcarpa bonsai. This time it was a scale incest. In the lab at work, I identified it as the Brown Soft Scale (Coccus hesperidum) (see images above). This is a common cosmopolitan pest which attacks many plant species used for bonsai. Figs, citrus, stone fruit trees, apples, quince and even orchids are just a few of them. Unlike other kinds of scale insect, soft scales don’t secrete wax, and they retain their legs, antennae and eyes throughout their life. You can’t see those body parts with a naked eye, but they are there (see the arrows pointing at eyes). Adult females are wingless and sedentary. Adult males are either winged or wingless and look similar to aphids. Control of Brown Soft Scale infestations is tricky. The infestation in my garden was small and I removed all scales with my fingers. When there are too many scale insects, you have to spray the plant thoroughly with a systemic pesticide or with one of those pest oils, but be careful  because these chemicals can injure the plant. Some of my bonsai lost leaves and even secondary branches. So, make the pesticide solution weaker than specified on the label and spray twice two weeks apart. Personally, I prefer one of the systemic pesticides, but other bonsai practitioners believe that an oil spray is more effective as it smothers the scales and they suffocate.