Thank you for your question Michelle. I am only familiar with one disease that causes unusually small leaves in maples - sapstreak disease (fungus). Suggestions to prevent sapstreak include the prevention of wounds/injury to the main stem and roots of your tree. Another factor that may contribute to small leaf size may be moisture - too little or too much. Moisture stress can interfere with nutrient uptake, which may or may not cause abnormal leaf development. General “decline” can also cause unusually small leaves. “Decline” is generally attributed to a combination of factors including drought, flooding, pollution, disease, pathogens, de-icing salts, sidewalk/driveway/road construction, excessive fertilizer or pesticide use, root damage, etc.
Regarding abundant fruiting: this is commonly attributed to good spring weather (no “killing” frosts), which encourages above average pollination. It is not uncommon for maples to have back-to-back abundant seed crop years. However, stress on trees can also account for unusually abundant seed production, which could be the contributing factor in your case.
Overall recommendation: monitor the health and vigor of your tree next spring and summer. Make special note of any irregularities, including unusually small leaf size, leaf deformities, insect activity, or a sparse crown. Controlled watering, fertilizing, and pruning may also prove beneficial. Please feel free to call me directly if symptoms persist into next growing season. Worst-case scenario will require an on-site visit by a certified arborist or tree care specialist.
