Garden columnist Dan Gill answers readers’ questions each week. To send a question, email Gill at dgill@agcenter.lsu.edu. 

There is something odd growing on my lawn grass. There are small patches where the grass blades turn ashy gray. When I touch it there is a black residue on my fingers. I’m not sure if it is hurting the grass, but I don’t want a lot of damage to occur before I find out what is going on. What is this, and how should I handle it? Terry

This is a slime mold. They are commonly seen in lawns during summer, especially after a period of rain. Slime molds are odd looking and are often confused with fungi, but they are considered a separate group. They live in the soil and feed on decaying organic matter, bacteria and fungi.

During or after wet weather from late spring through fall, slime molds come to the soil surface and grow on low-lying foliage, lawn grasses, mulches, ground covers, bases of trees and other such places. The aboveground growth is their reproductive stage, and it produces spores. This growth may be gray, black, yellow, pink or other colors. How bizarre can they look? One that shows up in beds is called “dog vomit” slime mold.

The slime mold commonly seen on lawn grass is bluish gray, turning black. As bad as it looks, this is not a problem. Slime molds play an important role in breaking down organic matter and providing nutrients to the soil. Slime molds do not attack plants or damage them in any way. No control measures are necessary. You may use a strong stream of water to wash the slime mold from what it is growing on, but it will go away on its own if you do nothing. 

There is webbing on the bark of my tree. It does not look like spider webs. I’m concerned this is something that will hurt the tree — my neighbor recommended I get it sprayed by a tree company. The webbing covers a large area of the trunk and even extends out onto the major branches. Is this something I need to have handled professionally, or can I deal with it myself? Mark

Midsummer into fall is the time of the year when fine, silvery webbing appears on the bark of trees. These webs are caused by tiny insects called bark lice which are common in Louisiana.

The small, soft bodied creatures are about 3 to 6 millimeters in length, live under the webbing and may or may not have wings. The proper name for these insects is psocids. The webbing they produce on the trunk and branches is to protect them from environmental conditions and predators. The webbing looks alarming as it spreads on the tree from the ground to the upper branches.

Here’s the good news: Bark lice are in no way harmful to the trees. These insects feed on organic debris lodged in the bark such as molds, pollen, fragments of dead insects and similar materials. They will be active until fall (they usually go away about October, if not before), and once the bark lice begin to die, the webbing will break up and disappear. They will not injure your trees, and no control is necessary. If you can’t stand the appearance of the webbing, you can sweep it off with a broom or blast it off with water. Most of us just leave them alone and let them clean off the bark of the tree.

My fig tree is plentiful with green figs; however, they are not ripening. I’m concerned. Shouldn’t they be ripening by now? David

Most figs ripen in July. I would not become concerned then. There is nothing you can do to make figs ripen — they will ripen when they are ready. After the harvest season, fig trees may continue to produce green figs. These often fail to ripen, although some varieties will produce a late crop.

Garden tips 

OUT WITH THE COOL: If you planted petunias this spring, don’t be surprised if they begin to look poorly this month or in July. Petunias generally do not tolerate the intense heat of summers this far south. When they languish, pull them up and replace them with more heat-tolerant bedding plants such as angelonia, blue daze, celosia, coleus, gaillardia, lantana, ornamental sweet potato, Profusion zinnia, marigold, melampodium, narrow-leaf zinnia, pentas, periwinkle, purslane, salvia, scaevola or torenia. 

DEAD HEAD: Remove spent flowers from bedding plants such as marigolds, zinnias, pentas, cosmos, salvia and rudbeckia to encourage them to continue blooming as long as possible.

VEGGIES ON THE WAY OUT: Spring and early summer vegetables planted back last March, like snap beans, cucumbers, squash and tomatoes, often finish up in late June or July. When you remove them, you could plant a green manure crop in the bed to improve the soil over the summer. Peanuts and Southern peas make excellent ones. Just as the young plants come into flower, chop them up and till them under. Then apply a few inches of mulch or a layer of cardboard to control weeds. The green manure crop will decompose in the soil over the summer and the bed will be ready to plant your fall crops.

TRIM CRAPE MYRTLES: Remove suckers that appear at the base of crape myrtles as soon as they appear by cutting them off at their point of origin at the trunk or even below ground. Do not leave a stub or they are more likely to resprout. You could use a sprout inhibitor (available at local nurseries or online) to help reduce how often you must do this.