Get It Growing

Effective August 15th I will be moving into a position as Assistant Director for the Louisiana Cooperative Extension Service and be housed on the LSU campus in Baton Rouge. I have truly enjoyed the last 20 years as a field agent (13 years working as an Extension agent in Lafourche, St. Mary and Terrebonne parishes plus seven years in Iberia Parish) and will truly miss working on a local level as a 4-H agent, County and Area Agent.

Landscape Insect Pest

One of the worst pests of late summer is the whitefly, a small white insect slightly bigger than a gnat. Clouds of them will fly up from a heavily infested plant when it is shaken. Both the adults and the immature whiteflies feed on the plant by sucking the sap from the foliage. Infested plants will have a sickly appearance and dull leaves. A black deposit called sooty mold often appears, and leaves may turn yellow and fall off. Sooty mold may also be caused by other sucking insects such as aphids and scale.

Whiteflies are somewhat selective in what they feed on – often infesting hibiscus, cleome, lantana, mallow, poinsettia, gardenia, Confederate rose and many bedding plants. Make sure you properly identify this insect pest prior to any control measures being taken. Call me at 985-446-1316 to assist in this critical step of pest control. When spraying, pay especially careful attention to thorough coverage on the most heavily infested plants. Repeat applications as necessary.

Plants heavily infested with whiteflies also may be cut back to reduce population levels. Just be sure to discard the clippings. In addition, as a last resort, low-value landscape plants – such as bedding plants – may even be pulled up and disposed of.

Controlling whiteflies can be difficult, especially when the population levels get high. On ornamentals you can use Talstar, Malathion, acephate or dimethoate. Although oil sprays are not recommended for use in summer when daytime highs go above 85 degrees, highly refined paraffinic insecticidal oils, such as Bonide Year Round Oil, can be used now and are effective against whiteflies. Oils kill by suffocation and are an excellent low-toxicity insecticide. Spray in the early morning when it is cooler. Check the label carefully for the safe and proper use of these pesticides and the listing of plants on which they may be used.

Bark Lice on Trees

Some areas are experiencing early decorations for Halloween. The webbing that has recently appeared on trees has many homeowners puzzled on what is causing this. Most homeowners want to find out what this is and how to control the problem. The answer is Bark Lice that weave the web for protection from predators. The Bark Lice are actually cleaning the trees by feeding on organic matter on the trunk and limbs. They are beneficial insects and should not be destroyed or killed.

Summer Pruning of Roses

Now through mid-August is the best time to prune roses in your landscape. The pruning is less severe than what was done in February but necessary to maintain maximum health of your plants and will lessen disease pressure, remove old growth and improve the overall health of the plant. You should prune modern rose varieties such as hybrid tea, floribunda, grandiflora and shrub roses at this time.

According to LSU AgCenter horticulturist Dr. Allen Owings, it is very important to conduct this pruning or ‘dead-heading’ of flowers and cutting back of foliage if it was not done on a regular basis this growing season.

Pruning accomplishes several things: height is reduced, and new growth, which results in fall flowers, is promoted. In addition, thinning out old, damaged and diseased canes will develop a desirable growth habit.

Cut back large-growing modern rose varieties to a height of 24 inches. Use sharp pruning shears, and make cuts just above outward-facing, visible, dormant buds. Cutting just above this bud will reduce the incidence of cane dieback.

Owings lists other rose gardening work that needs to be done in August:

Clear debris from rose beds and pull any weeds that may be present.

Add new mulch if you did not refresh the bed earlier in the year (pine straw is an excellent material).

Continue a preventive fungicide spray program for blackspot control.

Apply a light application of a slow-release fertilizer at pruning. This improves late summer growth and fall flowering.

Question of the Week: How late can I apply light horticultural oil to citrus trees to help control sooty mold?

Answer: Do not apply horticultural oils to your trees after mid August as this can impact the natural maturing of your fruit. Always read, understand, and follow all label directions.

For more information on these as well as other horticultural topics, call me at 985-446-1316 or email me at bhfletcher@agctr.lsu.edu. You can also check out the LSU AgCenter website at www.lsuagcenter.com.