Karl Foord - Extension Educator, Horticulture
This spring I noticed the black color on the branches of my Taylor's Sunburst Pine (Pinus contorta 'Taylor's Sunburst'). I remember seeing the same thing on my Uncle Fogy Jack Pine (Pinus banksiana) last year. The cause was the same in both cases Sooty Mold that has formed on the honeydew secretions of the Pine tortoise scale (Toumeyella parvicornis). To confirm this I went to the What's Wrong with My Plant Diagnostic Tool via the Extension Garden web page/Pest Management/Diagnose a Problem link. I tracked through "Evergreen Trees and Shrubs" to "Pine" to Black powdery coating on "needles" and "shoots". This confirmed the Sooty Mold. I also tracked through "Sticky substance coating needles" to confirm the Pine tortoise scale as the culprit.
The scale organism put such stress on my Uncle Fogy Pine that the needles it produced were half the size of the normal needles. Upon removal of the scale the needles returned to normal size (photo 1). I had learned my lesson about the impact of Pine tortoise scale on my trees.
I knew that Imidacloprid had worked on Uncle Fogy so I grabbed the bottle and reread the label - not trusting my memory. I confirmed that yes this product is labeled for soft scales. I also reviewed the precautions about letting the chemical get into aquatic environments - no lakes, streams, or ponds nearby. I agreed with the label that whatever I used to measure the chemical should not be followed by using the same utensil for soup.
There was nothing on the label regarding protective equipment, however the label warned that this chemical can be harmful if absorbed through the skin so I followed my previous procedures of long sleeve shirt, long pants and plastic gloves for handling.
Because this was an evergreen ornamental tree I was not concerned about the potential effects of a systemic pesticide on pollinators because there would be no flowers to pollinate. Also because the product is used as a drench around the plant, I didn't have to worry about airborne spray drifting onto other plants, people, or pets. In addition there were no wet leaf surfaces so there was no issue of reentry to the area or drying time of the product.
The directions called for the tree trunk circumference in inches at a height of 4.5 ft. and that this length in inches should equal the number of ounces of product to be applied to the plant. But there were too many needles to measure the circumference so I estimated the diameter and multiplied by Pi. How often do you get to use the trigonometry you learned in high school? The amount came to @ 5 oz. I added this to a gallon of water as instructed and applied the solution evenly in a circle 2 ft. from the tree trunk. Put the container away and washed up.
I checked the tree every other day or so and several days later the scales were starting to look ill. In approximately two weeks all the scales were dead. My Taylor's Sunburst Pine is looking and growing nicely without having hundreds of Pine tortoise scale stylets sucking its "life's blood" plant sap.
Reading the label wasn't all that painful. Reading size 6 font text definitely required glasses for "mature" eyes. However, I did not skim the label or skip parts. I read carefully and made sure that I understood all parts and the risks involved. Yes following the label is the law. Following the label is also the responsible and intelligent thing to do. By proceeding in this manner I felt in command of the situation and understood that the action I was taking was going to solve the problem with minimal impact to the environment and all the other actors in our theater of life.