Q. One of my neighbor’s cottonwood trees has unusual growths distributed throughout the plant at the ends of the branches. Is there anything they should do or is it just cosmetic? – Gallatin County
A. The growths are most likely poplar bud galls caused by tiny mites in the Eriophyid family. The mites (Eriophyes parapopuli) are numerous, microscopic in size, and can affect cottonwood, poplars, and aspens. When the tiny mite infests the bud of the tree, it prevents the leaf buds from forming correctly and often causes a dark, cauliflower-like gall 1-2 inches in size. The color of the gall is initially dark green, progressing to red in the summer. It then becomes nearly black in the fall and late into the season.
The galls may be unsightly, but they are most often just cosmetic and do not often impact plant health. The galls can be pruned out, but it’s not really recommended. Pruning may be difficult as the galls are often on the top of the canopy and if the tree is large enough, it would make pruning almost impossible. If the galls are removed, they should be burned, buried, or disposed of. Spraying pesticides is largely ineffective as the active ingredient rarely comes in contact with the mites that are buried in the gall. The pesticides only provide control when applied immediately after bud break.
Finally, keeping the tree in good health will minimize the potential damage. Make sure the trees are well-watered and check for nutrient deficiencies. Overall, the worst infestations I have seen are often on trees that are stressed.
Q. With all of the wildfires in Montana, there has been a lot of smoke around the valley. Will all that smoke affect my landscape plants, especially my trees and shrubs? If so, is there anything I can do? – Glacier County
A. There are studies from Brigham Young University that show in a controlled study that photosynthesis was reduced on some species when they, as seedlings, were exposed to smoke. However, in the same study, it showed that there was no significant effect on growth. Information regarding the effects of smoke on gardens from New Mexico State University indicated that their garden could actually benefit from the effects of smoke. Benefits mentioned were lower or diffused sunlight, which can help reduce scalding in highly sunny environments, and increased carbon dioxide levels that generally benefit plants.
Overall, the smoke may affect landscape plants, especially if they are in the seedling stage. However, if a majority of landscape plants are mature plants, they will most likely be fine. At this time of year, there isn’t much that can be done but to make sure they are well-watered in fall and then again in spring.
Q. My apples did not produce well this past year. Should I be doing something different this year to get more apples next year? – Yellowstone County
A. You are not alone. Low fruit establishment was widespread this year. Due to the strange winter weather we experienced last year, the flower buds froze either last November when the temperatures plummeted over 70 degrees in 24 hours in some areas, or in the spring when the temperatures fluctuated extensively. Of the nearly 70 trees in the MSU Horticulture orchard, only one pear tree and only a few apple trees produced fruit this past summer. Some trees even died due to winter kill.
So, what can you do this coming year to promote more fruit? Most fruit trees need cross pollination from another cultivar to ensure fruit set, so make sure there is a compatible variety nearby and try to encourage pollinator activity. Also, be sure that the trees are watered and fertilized properly. You may want to perform a soil test this spring to assess nutrient levels. Don’t over-prune this winter/spring. Over-pruning may put the tree in a more vegetative state, thus the tree will not flower as much. However, keep in mind that much of what happened this past year was weather related.