Not sure which one you use for your trident, but anyone that's good for apple trees should work. Turns out what affects serviceberry isn't cedar apple rust but closely related (cedar-hawthorn rust).
Got this off of Missouri Botanical Garden's website:
"Cedar-apple rust (
Gymnosporangium juniperivirginianae), cedar-hawthorn rust (
G. globosum), and cedar-quince rust (
G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (
Juniperus virginiana) as well as many other junipers and an alternate host. Of these alternate hosts, cedar-apple rust is primarily a disease of apples and crabapples. Cedar-hawthorn rust, in addition to affecting apples and crabapples, sometimes infects pears, quince, and serviceberry. Cedar-quince rust has the broadest host range and can infect many genera in the rose family. In addition to those plants already mentioned, mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia are also hosts for this disease."
"Use preventive fungicides labeled for use on apples. Fungicide sprays are aimed at protecting developing foliage from infection during the time the galls on the junipers are orange and gelatinous. This usually lasts for several weeks and fungicide applications are not necessary once the galls become dry and inactive. Pesticides registered for use include
captan,
chlorothalonil (Daconil),
copper, mancozeb, maneb,
sulfur, thiophanate methyl (Cleary 3336), thiram, triadimefon, and ziram."
Hope this helps, don't know if you've eaten the berries before but they are delicious as long as they don't get the nasty fungus spikes on them...
