I am reaching out to our Agrofroestry Extension expert. Will get back to you shortly!

Scotch pines (Pinus sylvestris) are not susceptible to this fungal disease. It infects spruce. https://extension.umn.edu/plant-diseases/rhizosphaera-needle-cast

However, pines can be affected by needle rust diseases. More information can be found here: https://extension.umn.edu/solve-problem/plant-diseases#tree-and-shrub-diseases-1872363

Re: Rhizosphaera needle cast on spruce - Our Extension Educator, Gary Wyatt, replied as follows:

It looks like recommendations are for the bottom 2/3's of the trees need to be treated when new shoots begin to grow. Follow label directions.

I haven't seen anything in the literature that mentions spraying the ground or mulch, possibly a waste of chemicals. Spraying the new growth and buds is most important. Note attachments and recommendations below.

Penn State recommends:

• Apply an appropriate fungicide when new shoots are ¾–1¼ inches long (needles are half elongated) and a second spray 3 weeks later (needles are fully elongated). Moderately infected trees may require 2 years of fungicide applications.
• In some areas, it may be necessary to make another application in mid-August to early September to prevent late summer infection.

NDSU recommendations: Protect new needles from new infections for a minimum of two months early in the growing season for two to three years. The timing of these applications is extremely important. Complete the first application just after bud break when needles are about half the size of the previous year’s needles. Timing of the second application depends on which fungicide is used. Carefully follow all label directions. Protect the new needles for two to three years to allow infected needles to be shed and decompose. Use equipment that is large enough to get fungicide onto the lower two-thirds of treated trees. Follow label directions for optimum coverage.

Rhizosphaera fungal spores can survive on living and recently killed needles, so it probably wouldn't hurt to rake up needles that have fallen and dispose of them. Sanitation is always helpful in reducing disease spread.

Gary also sent along these two attachments.

You are welcome! Good luck with your trees!