“Groundwork” column for Sept. 16, 2012

Recent rains and the transition into fall make September a perfect month to treat fire ants in your lawn and landscape. Fire ant colonies reach their peak in the fall having grown throughout the summer months.

The ants tend to be most active in the spring and fall, when daytime temperatures are between 70 and 85 degrees. During the fall especially, they spend a lot of time foraging for food. Actively foraging ants will pick up bait and carry it into the nest within the first hour or two. Always apply baits early in the morning.

Treat fire ants by first broadcasting a fire ant bait like Amdro. Follow the product label carefully. When properly applied, this should suppress the ants about 90 percent. This can be done either across the home lawn or in a 4-foot circle around each mound. Do not disturb the mounds. Never apply bait using a spreader that’s been used to spread fertilizer. Fertilizer can contaminate the bait by altering the smell.

Allow the bait to work for a week to 10 days. Then kick the ant mounds or poke them with a stick and step back quickly. If there is any ant activity, apply a contact insecticide to target the mounds.

Get a long stick and run it down through the center of the mound. Pull the stick out quickly and pour in the pre-mixed insecticide. Pour the insecticide quickly as the ants will scatter once the mound is disturbed. A pre-mixed gallon or two of insecticide should fill the mound from the bottom up.

Dusts or powders can also be sprinkled on the surface of the mound if you prefer dry treatments. One really excellent one is Orthene (acephate). For those colonies that might survive the bait treatment, a second treatment of the mound with this material is an excellent idea.

Bothersome bluegrass

One of the most bothersome winter weeds in lawns is annual bluegrass (Poa annua). It seeds prolifically and the best time to control its growth is to apply a pre-emergent herbicide now through October, before seed germination.

The seeds and tiny seedlings must be killed as they try to sprout. Read and follow label directions. Look for herbicides with one of these active ingredients: atrazine, benefin, bensulide, dithiopyr, pendimethalin, prodiamine, metolachlor, oxadiazone, oryzalin, simazine, trifluralin and their combinations.

Flying good time

Butterfly expert Gary Ross will be featured at the Hummingbird and Butterfly Festival from 8 a.m. to 5 p.m. Saturday at Mizell Farms in Covington. Stroll through the gardens, butterfly flight house and nature trails. Watch hummingbirds being weighed and banded by Steven Locke.

This is one of the largest butterfly and hummingbird garden in Louisiana. The plants that attract butterflies and hummingbirds grow on site and will be available for purchase. There will be vendors, seminars, a children’s table, and a butterfly release. For directions and details, visit http://www.mizellfarms.com.

Wet soil?

Hurricanes can create excessively wet soil that when combined with high temperatures can create stressful, and potentially destructive, conditions for bedding plants, perennials, vegetables, shrubs and even trees.

When the soil is saturated with water, pore spaces in the soil that normally hold air are filled with water. Since the roots of plants get the oxygen they need from the air in those spaces, the roots can literally drown when soils stay waterlogged for an extended period. A sick root system leads to a sick plant. Plants in this situation often lose vigor, look wilted, yellow, stunted or may even die.

These wet conditions also encourage fungus organisms in the soil to attack the roots or crown of a plant and cause rot. The crown is the area where the stem of a plant enters the soil. These disease organisms can cause dieback or severe damage or even kill plants. Once infection occurs, little can be done to help a plant.

Landscape losses

One of the greatest landscape losses during hurricanes is mature shade trees. It takes decades for shade trees to achieve their mature size, so they cannot be quickly replaced. Large trees create shady conditions in landscapes and largely determine what kind of plants can be grown. Areas shaded by trees are planted with plants that prefer and thrive in shade.

When large trees are blown over and removed, areas that were previously shaded will receive substantially more sun. Suddenly exposing plants that were shaded to full sun will burn or scorch their foliage. Some plants will adapt and the new growth they produce in the sunnier conditions will do well. Most shade-loving plants, however, will not do well in the sunnier conditions. These plants should be transplanted to areas of the landscape that are still shady, and sun-loving plants should be planted in their place.

When choosing a replacement tree, do not simply focus on rate of growth. People always want a tree that will grow as fast as possible to replace the lost tree. It is also very important to look at the appropriate mature size and whether the tree needs to be evergreen or deciduous. Ornamental features should also be considered such as flowers, attractive berries, brightly colored fall foliage or unusual bark. Be sure to choose trees that are well adapted to your local growing conditions and soil type. Even fast-growing tree species will take at least five years to begin to create much shade.

Got a gardening question? Write to Bob Souvestre, horticulturist with the LSU AgCenter, at Burden Center, 4560 Essen Lane, Baton Rouge, LA 70809, or email to [e-mail], or call Master Gardeners at [phone].