Cooperative Extension: Garden and Yard

There are a number of foliar conditions that can cause this kind of leaf spotting and early leaf fall, and it’s often difficult to diagnose from photos, but there is obviously something going on with your pear and crabapple. Pear scab and pear rust are separate fungal pathogens, and of the two I would lean toward suspecting scab from the appearance (you can see examples of rust in that link). Apple scab (which also often affects crabapples) is caused by a very closely related species to the one that causes pear scab, so it would make sense with common growing and environmental conditions that this could be a likely culprit. I don’t think the peach or plum would be at risk of spread for those particulars funguses, but there are other things to consider, like bacterial spot, which can present similarly on the leaves and can affect all 4 plants. If we are looking at scab, your first line of defense is the easiest: increased sanitation (e.g., removal of infected tissue, prompt disposal of all fallen plant debris, sanitizing tools after use to prevent spreading to the next plant worked on) and proper pruning (thinning the canopy increases airflow and mitigates the close, still, warm air conditions in the interior of the tree that drive spore proliferation). There are also some fungicide recommendations in the above links, but increased sanitation and a bit of TLC can often manage scab effectively, if it isn’t too widespread.

However, because visual diagnosis is often tricky, I will also suggest you consider submitting these photos and/or a physical sample to the UMaine Plant Disease Diagnostic Lab if you are still concerned, or if my advice doesn’t improve things or doesn’t match what you’re seeing. There is a small fee for their service, but you’ll get lab confirmation of any pathogens present. Situations like this are also a good time to have your soil tested through the UMaine Analytical Soil Lab (test kits are available in any Extension office, or the lab can mail you one) and to review the best practices protocols for fruit tree care in Maine (available in the pruning link above)–healthy vigorous plants weather these conditions better.

Happy gardening.