Pecan trees dropping leaves with black spots in June

Asked June 12, 2014, 5:05 PM EDT

Hello, two pecan trees around our house just started dropping leaves with black blotches on them. The huge trees on our acreage date from the 1950's. We are just north of Pearland, TX. We have many pecan and other trees on the property (we're not growers). We spent the winter cleaning up all the leaves under the trees. We're new to the area, and would appreciate advice on how we can help our trees or whether this is something to be handled by a commercial firm. Thanks!

Harris County Texas

2 Responses

Pecan trees are native to Texas, and as such have several insect pests and fungal or bacterial diseases that can cause problems with the fruit (pecans) and foliage. Since you have several trees on your property, you may want to become familiar with some of these annual problems. Websites that may help you are http://pecankernel.tamu.edu/ and
http://pecan.ipmpipe.org/
The leaf in your picture is infested with pecan phylloxera galls--an insect. There are two forms of phylloxera and I have to assume since the leaves are falling, that you have the form (called pecan phylloxera, rather than leaf phylloxera) that attacks stems, leaves and even nuts. The spots you see are actually raised bumps, called "galls" that contain immature forms of these aphid-like insects.

This insect does its damage at the time of budbreak, so there is nothing you can do now to stop the damage. The tree will form new foliage over then next few weeks. Your crop may be partially or completely lost for that tree. Not all trees on a particular property may show the problem each year (and we don't know why), but there is some chance for spread, and trees with the problem this year are likely to show it next year. An insecticide must be applied at budbreak to all of the canopy to prevent this from happening again.

This diagnosis is based on your one picture. There are possibly other things contributing to foliage drop, but pecan phylloxera is at least one thing that you have.


Thank you! This info is now on my calendar for next spring budbreak.