Q. I hope you can give me some advice on what is ailing my redbud tree. When I examine the somewhat tattered leaves I don’t see anything crawling or chewing on them. Also I don’t see anything crawling on the trunk. There is a bulge on the trunk that is about the size of a small cantaloupe. When examining the canopy I found smallish brown bumps (spore?) on lots of the small branches. When I scratch at them they are dry and empty. Also, there are so many brittle small stems that can break off easily and leaves are falling off daily. We have several other trees in the backyard that are doing well, but it’s the redbud that has us most concerned. What do you think? – C.C., Albuquerque
A. First I can’t tell how the tree is tended. From the photos it looks like the redbud lives in a graveled space. I’m hoping you do have a wide well or moat surrounding the tree and that when it’s watered you fill the well slowly to assure the tree a good drink.
The bulge, or burl, was created by the tree by stress, a fungal/bacterial infection or insect invasion. Perhaps a branch was incorrectly removed from the tree to shape it, and doing so cut too deeply into the trunk. Maybe the tree was injured and that became a gateway for some sort of fungi or pest. But as long as the tree is kept healthy, the burl isn’t weeping sap and you don’t see bugs congregating, I’d not worry too much about that.
The “spore” you found is the covering made by a bug called scale. You’re correct that now they are empty, since the scale bug has gone through it stages and has left those “houses.” As long as you don’t see an undulating mass of creepy crawlies surrounding or moving within the tree, now isn’t the time to treat for them.
I will recommend that you invest in a horticultural oil – dormant or superior oil – to spray on the tree. But don’t do that now as it’s far too hot! My organic gardening book strongly suggests that any oil spray should not be applied when the daily temperature rises above 85 degrees.
What the oil spray does is very effectively clog up the bugs at most any stage.
Just be sure to NEVER spray a spruce tree with the oil since it can maim them. Make sure you read the oil label completely for any other known restrictions or cautions.
I suggest that you make a point of applying an oil pesticide several times a year to keep the redbud more pest free. During the winter months, perhaps October, after the tree has dropped its leaves. Again 6 to 8 weeks later, late December to early January, again the label will give temperature restrictions, to cover any overwintering bugs. And again just before buds break in the early spring.
The spring spraying, especially on a redbud will need to be very timed since you don’t want to risk of an oil spraying distorting the marvelous bloom of the redbud, and you don’t want to harm any pollen gathering insects.
As to the holes and tears in the pictured leaves, some could be pest related, but to me it looks like wind and or hail damage.
You didn’t mention fertilization. If the redbud hasn’t been fertilized lately, consider doing so. Any tree specific granular fertilizer watered in, following label application dosages. Make sure you’ve watered first, because as I’ve preached time and time again, YOU NEVER FERTILIZE A DRY PLANT!
Make sure you rake up and dispose to the leaf-litter this fall, create and maintain a periodic oil spraying, water deeply and consider a fertilization soon and again in the early spring. Since redbuds are my most favorite flowering tree ever, I hope yours gets healthy and continues to be a marvel for you!
Happy Diggin’ In!
Tracey Fitzgibbon is a certified nurseryman. Send garden-related questions to Digging In, Albuquerque Journal, 7777 Jefferson NE, Albuquerque, NM 87109, or to firstname.lastname@example.org.