Nov 4, 2013 17:32 Groundwork column for Oct. 11, 2013 Groundwork column for Oct. 11, 2013 Treat camellia scales with oil bob souvestre Nov. 04, 2013 Comments Advocate file photo -- To keep your camellias free of scale, apply a horticultural oil in the fall.My camellia leaves are turning yellow and the undersides are covered in a fluffy white growth. What is it and how can prevent it? The plant is infested with camellia scale. When temperatures moderate this fall, apply a horticultural oil. Two or more applications will be required to kill the scale. A soil application of the systemic insecticide imidacloprid can provide seasonlong control when applied in early spring. I have large black ants in my tree. One stung me on the back and caused a five-week infection. What do I kill them with? It was likely a carpenter ant, and, while their bite can be painful, they usually are passive and nonthreatening. Carpenter ants frequently infest broken or rotting branches. These insects do not feed on wood but simply nest in the wood. Control carpenter ants by removing rotting tree limbs. Apply carpenter ant bait for control. How can I permanently kill nutgrass in my flower bed? Herbicides containing halosulfuron work quite well. Apply to healthy weeds and give it time to work. It will not prevent new plants from emerging from dormant tubers, but it will kill what is sprayed. Why are my navel oranges splitting wide open? Young trees and fluctuations in the weather, temperature and watering cause fruit split in citrus, especially navel oranges. A period of high humidity followed by a dry period can trigger splitting. Usually only a few fruit on any given tree are affected. Irrigate when the top 3 to 4 inches of soil have dried out. For two years, my potted plants have died from diseased soil. I have both clay and plastic pots. How can I prevent this from happening in the future? Remove all soil and plant parts from the pots. Soak the pots in a large container of nine parts water and one part bleach overnight. Remove, rinse and resoak overnight in clear water. Air-dry for one day and they will be ready to reuse. 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 firstname.lastname@example.org, or call Master Gardeners at (225) 763-3990.