Dear Neil: Over the course of the past 10 years my 30-foot magnolia has grown thinner and thinner. Now it has the patches of white growing on its trunk and branches. What causes this, and what can I do about it?

A: These are lichens, and they’re a tandem growth of algae and fungi. You’ll see the same sorts of lichen growth on “moss-covered” boulders in stone yards. They are harmless to the trunk of the tree (and the boulders). As for the thinning, that may be a combination of the really hot, dry summer we’ve had and the several others that we’ve had in the recent past. It’s not really apparent in your photo. My suggestion would be to apply an all-nitrogen fertilizer to this and other trees in midspring, early summer and early fall and to keep it watered deeply as well.

FIRE ANTS

Dear Neil: We’ve had a nice blueberry bush at our home in the Hill Country for seven years. Because it has trouble with alkaline soils we’ve grown it in a half whiskey barrel and we’ve acidified the soil to make it blueberry-friendly. It’s given us a nice crop of berries the past two years, but now we have an ant colony in the soil. They boil out every time I water the plant. Is there something I can use that won’t harm the plant?

A: Those may very well be fire ants. They are especially fond of potting soil. You can certainly use any of the fire ant baits, and applied around existing plants. Talk to your Texas Certified Nursery Professional and read the label carefully. Some of the specific fire ant mount treatments are damaging to roots.

LEAF MINERS

Dear Neil: My lantana is on my patio with a western exposure. It is blooming and has vigorous new growth, but it has these spots on many of its mature leaves. Is this a fungus? Could I have over-watered it? What can I do to make it look better? I try to use non-toxic materials whenever possible.

A: This is insect-related, I believe leaf miners. The larvae tunnel inside the surface of the leaves resulting sometimes in lines and spirals and other times in blisters. I would try a systemic insecticide if they were my plants. I respect your comment about “non-toxic materials,” but there is nothing that will kill insects and not be toxic.

BERMUDA SMUT

Dear Neil: I have this black fungus-like growth in my Bermuda lawn. I’ve replanted the entire lawn, but it keeps coming back. As I walk through the grass it turns my shoes black. What can I do?

A: That’s Bermuda smut. You’ll see smut on other grasses, corn included. It’s harmless to your bermuda – more an annoyance for the mess it can make with your clothes and shoes. The best ways of dealing with it are to mow frequently so seed heads can’t form (since that’s where it develops) and apply an all-nitrogen fertilizer to stimulate new leaves and runners. There is absolutely no need to replant.

TIMING FOR PRE-EMERGENTS

Dear Neil: I’m a recent Texas A&M graduate and am new in the commercial lawn care business. I want to do things properly. What is the timing for application of pre-emergents in the fall for winter weeds? I have a large spray tank. Are sprays as effective as granules?

A: Timing will vary a bit across the state of Texas, growth, but it has these spots on many of its mature leaves. Is this a fungus? Could I have over-watered it? What can I do to make it look better? I try to use non-toxic materials whenever possible.

PRUNING LIVE OAK

Dear Neil: We have a huge live oak that needs to be pruned. We hired someone to do it for us this month. He said he would be applying pruning sealant, but now we have heard that really hot weather is not a good time to trim trees and that pruning paint is not a good idea either. What are your thoughts?

A: It sounds like you found a very good arborist. Go with him. Research has found that (1) oak wilt is inactive once temperatures reach their summertime maximums by mid-July, and that (2) pruning sealant is always a good idea with oaks to lessen the chances of spreading oak wilt. I do not recommend pruning sealant for trees other than oaks, however.

Have a question you’d like Neil to consider? Mail it to him in care of this newspaper or e-mail him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.