What’s that on My Pine Trees?
Earlier in the fall some of my favorite pine trees on Minnetrista’s campus started catching my eye, and not in a good way. The low growing sprawling pine is Hillside Creeper Scotch Pine. It is featured in our Bird and Butterfly Garden and they were covered in white all along many of their needles.
As I looked closer, I noticed the white coloration made up many individual spots and were oval shaped, looking very similar to scale, which can sometimes be a problem on a variety of plants in the gardens.
After a quick internet search for “white scale on pine,” it was apparent that the Hillside Creeper plants in the garden were suffering from an infestation of pine needle scale, aka white scale.
Scales are insects that have piercing mouthparts, allowing them to suck sap from plants. There are many types of scale, and they are often described by the plants they feed on, and whether or not they are armored or soft. Some are generally harmless, even in big populations, while others can kill your plants. Most others will cause aesthetic issues, preventing your plant from looking its best.
In the case of pine needle scale, it is armored and can cause death of branch parts or even whole plants if the population is high. Like other armored scale, insecticides are of little use when the insect is mature because of the armored scale. There are however, windows in the life cycle where they are effective.
In the spring, overwintered eggs will hatch from under the scales left over from their mother. They will emerge and begin to move around the plant. They are very vulnerable in this crawler phase and can be killed with insecticides. There are usually two life cycles in our region, so depending on the success of a spring treatment, a follow up spray during the next hatching can help too.
Of course most insecticides are deadly to more than just the pest problem. In the case of pine needle scale, ladybug larvae and other insects, like certain wasps, will actively eat the scale. Careful monitoring of these beneficial insects should be done prior to choosing insecticide. If you’re lucky, nature will take care of the plant by itself.
In our case at Minnetrista, we’ll go with a dormant oil spray in late March or April. This oil will smother overwintering eggs. We’ll then monitor for natural pest control partners like ladybugs, and adjust our approach as needed throughout the summer.
