Do Not Fertilize Lawns

Clinton "T-Boy" Lirette
March 7, 2008
March 11
March 11, 2008

It is still too soon to fertilize your lawn but the time is drawing close. LSU AgCenter Best Management Practices (BMP’s) recommend that you wait to fertilize your lawn until the first week of April in South Louisiana. Warm season turf grasses such as Bermuda grass, St. Augustine and Centipede are currently in a transitional period slowly awakening from a dormant period. If you fertilize too early you can force early season growth and increase disease problems. In addition, early nitrogen application can cause rapid growth and set your lawn up for cold damage if we get a late frost.

Both of these situations can open the door for weed, insect, and disease pests to move into your lawn. Wait until the first week of April and base your fertility program on a soil analysis from the LSU AgCenter soil test lab. Give me a call to find out the best way to take a soil sample.

Home Garden Update

Home vegetable gardens are in full swing as many of you have tomato transplants in the ground and shooting for that first ripe tomato by Mother’s Day. The LSU AgCenter tomato variety demonstration plot will be planted in the next 10-14 days with different tomato varieties in the ground at Waterproof Ridge Farm near Houma and preparations are being made for our “Tomato Field Day” that will be held in early June.

The recent cooler weather is a reminder that we can still have a late frost or light freeze during the month of March. Our last typical date for a frost is March 15th but I have seen them into early April.

Many gardeners have their Irish potatoes marking the ground and growing rapidly. Make sure you are checking for aphids under the leaves as well as monitoring for Early or Late Blight on the foliage. Late blight is caused by Phytophthora infestans and all plant parts are susceptible to infection. Late blight is a major problem in potato production worldwide and the Irish potato famine of the 1840s was caused, in part, by this disease.

It has been fairly dry up to this point so foliar diseases will be lessened until we get into April showers. Malathion will control aphids in your Irish potatoes at the rate of two teaspoons per gallon of water. Make sure your water pH is around 6.0 for best results. A fungicide containing chlorothalonil will help prevent Early and Late Blight on potatoes and tomatoes.

Citrus Insect Pests

In late winter and early spring you will see insects such as white flies attacking the recent lush growth on most citrus trees in the area. White flies basically suck the sap out of these leaves and secrete honeydew that will eventually turn into what we call black sooty mold.

White flies can multiply very rapidly and basically turn the foliage black in a short period of time. This sooty mold can stress the plant by inhibiting the plant’s ability for photosynthesis to occur. This will cause additional stress as if the insect’s initial damage was not enough. Homeowners can use a product called ultra fine oil per label directions for good control.

A combination of the insecticide Malathion per label directions will enhance the control of white flies. It is important to remember that the water pH in the spray tank must be buffered to 5.5 to 6.5 prior to mixing in any insecticide for best control. You can find a buffer at your garden center or feed store.

Leaf miners can also be a pest to the new flush growth of your citrus trees. This insect causes the squiggly lines in the leaves and can have a negative effect on very young trees. There is a new product that does an excellent job in controlling these insect pests. Go to your garden center or feed store and ask for a product that contains spinosad as the active ingredient. This product will control leaf miners and caterpillars as well as aphids and is very safe.

Question of the Week: When is the next Louisiana Master Gardener program going to be offered in the area?

Answer: The next class will be offered in August through October. Call 985-446-1316 to register for the classes, which are typically offered once per week in two three hour blocks per day.

For more information on this or other horticultural topics, email me at, call me at 985-446-1316, or come by 402 West 5th Street in Thibodaux