Are chum tree / shrubs susceptible to cherry maggots
Thank you for consulting Toronto Master Gardeners, ASK site.
Growing fruit trees is a joy and a challenge: your choice of a chum -cherry/plum cross, invites a bigger challenge, as there is little published.
Let’s assume that maggots of either the plum or the cherry may indeed infest and affect your special fruit.
Your best reference is Ontario’s own Ministry, which has many publications on its site.
When you look specifically at the sour and black cherry site, for example, you find information on the distinction between the maggot for the cherry and the plum. Note the difference in the head of the maggot. Cherry maggot is the Rhagoletis and the plum is the Curculio larva. The adult fruit fly may attack this tree, then.
If you are unfortunate to have this issue in the coming season, be prepared by consulting the OMAFRA regulations regarding acceptable chemical treatments.
Read more by visiting the OMAFRA site, with many publications. Ontario Ministry of Agriculture, Food and Rural Affairs – Fruit trees in the home garden.