Could this be rust fungus?

Question: Hello ! I had described a condition of our Bradford pears. I didn’t send a picture so it was impossible for you to know for sure. It appeared to be fire blight, but now we have an arborist who is going to treat it as rust fungus. They are going to be sprayed at two different times. Please look at the photos of our trees. ( We have 39 of them unfortunately.) does it look like rust fungus?
Thanks… Kathleen… landscape chairperson

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 07, 2023, 10:54 AM EDT
response: Hi,  There might be some rust in the trees,  but that's not the major cause of the symptoms pictured. Our team can see rust, fire blight, possible powdery mildew, and some other leaf infection.Since Bradford pear an invasive species it is probably are best to just budget to have the trees removed and replaced. Treatments this time of year for rust are ineffective too and need to be started in the beginning of the spring and followed through until weather changes that isn't favorable for rust. We would suggest that you replace the trees with a mix of species to avoid a widespread infection/infestation issue in the future. When trees (or any plants) are planted in a monoculture (all the same plants) it makes it easy for disease, insects, or devastation from an extreme weather event to effect them all at once.  Check out our Planting Trees In Our Changing Climate page for suggestions on how to select species appropriate for handling the challenging conditions in your neighborhood.  A few more webpages that may be helpful:  https://extension.umd.edu/resource/native-plants-and-climate-change https://extension.umd.edu/resource/tips-choosing-trees-and-shrubs Emily

responder: The Question Asker Replied June 08, 2023, 6:36 AM EDT
response: Thank you very much for your expert team diagnosis.  I really appreciate your advice and recommendations. I know how invasive these Bradford trees are. I did explore the sites you recommended, but I am hoping for more specific information. I did not find a list of trees that could work for Bradford Pear replacements.Can you offer some suggestions for us?Thanks again!KathleenSent from my iPad On Jun 7, 2023, at 10:54 AM, Ask Extension <<personal data hidden>> wrote:﻿

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 08, 2023, 5:07 PM EDT
response: Hello Kathleen,  You might want to see what a consulting arborist offers as suggestions since they could evaluate the on-site conditions, but there are many species to choose from and narrowing them down will depend on both your aesthetic or wildlife value priorities along with the growing conditions in these planting locations. We presume these are street trees, in which case they'll have to deal with limited root space, likely reflected heat and pollution from the roadway, drought stress, compacted and possibly oxygen-poor soil (at least during wet conditions), and possible salt contamination as well if the roads are treated with ice melt (not necessarily sodium as the "salt," but any number of minerals in this or fertilizer runoff from nearby lawns).  As one example, oaks are great ecosystem-supporting trees and Maryland is home to around 20 species, some with tolerances for wetness and others for drought, and so on with other varying adaptations. Nurseries tend to focus on only about four or five oak species in their offerings, so finding others might be more challenging. Sycamore is sometimes used along streets for its adaptability to wetter soils (which ties-in with a tolerance to poorly-oxygenated soil in general, like from compaction), but in dry years they can be stressed unless given supplemental water. Plus, any leaves they shed are sometimes considered a nuisance since they are large and occasional anthracnose outbreaks (as we're having this year) can cause a period of spring leaf drop as well. Ginkgo is fairly indestructible but isn't native, is slow-growing, needs to be male to avoid malodorous autumn fruits, and has very little wildlife value aside from its shade benefits and carbon capture just due to the fact that it's a large-growing, long-lived tree. Honeylocust (the thornless varieties sold) is very tolerant of harsh street-side conditions but can aesthetically be quite the eyesore come late summer if they've had a hard year, despite bouncing-back admirably the following spring as if nothing had happened. Hackberry, despite having an unappealing name, also does admirably well in tough spots but has a tendency to accumulate leaf galls made by insects, which despite being fairly harmless to the tree might be an eyesore for anyone noticing that leaf lumpiness. Hickories might do well but can be very tap-rooted when young so few nurseries stock them or older plants might be more expensive since they grow slowly and need careful root care when dug for sale. Osage-orange, native in the U.S. but not locally, can also be very tough but should be chosen as a thornless selection (the wild type has dangerous thorns) and male so the huge heavy grapefruit-sized fruits don't fall onto cars. As a generalization, among tree types that produce male and female flowers on separate plants (Maple, Black Tupelo, etc.), choosing male varieties will mean less potentially-messy fruit or seeds falling but more pollen to deal with in the spring, though tree fruits and seeds can be a draw for songbirds.  As these examples illustrate, there may be trade-offs to just about any selection and every tree is vulnerable to at least one insect pest or disease, so weigh what's important to your community with regards to ease of tree care and likelihood of survival with limited intervention versus year-round appearance and that might help reduce the list of candidates a bit. In either case, using multiple species overall as Emily mentioned is important to reduce the risk of an ailment affecting every tree equally, and the mix would also potentially be of greater benefit to wildlife and will offer more seasonal interest as well with different leaf textures, bloom seasons, and/or autumn leaf colors. (Granted, not many species of shade-tree stature have very showy flowers compared to understory-sized trees.)  Locally- or regionally-native tree species are preferred for ecological reasons, but non-invasive non-natives can be useful for their tolerance to the site conditions which due to development might no longer be as suitable for native species that would normally grow in that habitat. Certain cultivars of native species might also be better than their "plain" wild counterparts since they'll have improved resistance to disease, such as the newer American Elm varieties that are less vulnerable to Dutch Elm Disease.  We don't generate extensive tree-selection lists but the two resources linked previously about tree adaptability can help highlight some with potential. Some native trees might be more easily sourced as quite young plants through native plant nurseries either local or online, but their difference in age from the sizes nurseries typically sell won't be a detriment because young trees transplant with less stress and tend to catch-up to older specimens quite easily, since the older the plant installed, the more years it takes to settle-in. Mid-range height candidates that might suit street-side use include American Hornbeam / Musclewood, Hophornbeam / Ironwood, and Common Persimmon.  Miri