(04/09/16) HAMMOND, La. – A wet fall and warm winter followed by heavy rains this spring provided ideal conditions for pathogens and insects, fueling several problems for gardens and nurseries, said LSU AgCenter plant doctor Raj Singh.

His presentation was one of several on May 6 at the annual Margie Jenkins Azalea Garden Horticulture Lecture Series and Industry Open House, an event held at the AgCenter Hammond Research Station in recognition of Jenkins, a longtime Louisiana nursery owner.

Singh said leaf gall has been cropping up in azaleas and camellias. The disease won’t kill the plants but causes unattractive galls to grow on leaves and turn brown. Removing galls from plants and the ground is essential to manage the disease, he said.

Rust disease has also been a problem on flax lilies and roses in Louisiana because of favorable weather conditions this year, he said.

Leaf gall and rust are not new problems to Louisiana, Singh said.

On the other hand, rose rosette disease is new to the state and has been found in the Shreveport area. Knock Out roses and all other cultivars are susceptible to rose rosette, which can cause thickened canes, excessive thorns and reddish foliage, Singh said.

Leaf scorch in sweet olives and oleander is another new disease showing up in Louisiana, Singh said. The leaf scorch bacteria clog channels in plants, restricting the movement of water and causing the plant to wither. There is no cure.

Citrus greening and citrus canker continue to have devastating effects on citrus trees in Plaquemines Parish. “Disease surveys have almost been completed to determine the spread of these diseases in Louisiana,” Singh said.

A Section 18 exemption has been renewed for Louisiana, allowing the use of the Termidor insecticide to control tawny crazy ants, AgCenter entomologist Dennis Ring said. The ants can build up huge populations quickly.

“It’s very important not to move this ant to your area,” Ring said.

The field day also highlighted plants that perform well in Louisiana landscapes, including both natives and new releases.

The Southern Living Plant Collection and Encore azalea lineup both continue to grow, with several new varieties recently or soon to be released to the market, said Buddy Lee, director of plant innovation for Alabama-based Plant Development Services.

The Encore Autumn Fire azalea is a recent release with true red flowers on a compact plant that is heat- and cold-tolerant, Lee said. The Sunbow Azalea series offers similar shades – the orange-red Solar Glow and yellow Solar Flare – along with a honeysuckle fragrance and resistance to powdery mildew.

Lee also talked about the Sunshine ligustrum and Lemon-Lime nandina, which both offer bright color and are adaptable to many soil conditions; the Marvel mahonia, which has yellow, fragrant sprays of blooms in late fall and early winter; the Purple Daydream loropetalum, a compact plant and new release; and the Delta Fusion crape myrtle, a new addition to the Delta series with dark pink blooms and burgundy foliage.

The White Lightning hydrangea, which has a sturdy stem and large conical blooms, will be released soon, Lee said. He also pointed to cyrilla and cliftonia as examples of plants native to the South that do well in gardens.

“We’re moving to develop native plants that are more adaptable to gardens,” he said.

Jeff Kuehny, resident director of the AgCenter Botanic Gardens at Burden in Baton Rouge, shared information about some of his favorite annual, perennial and woody ornamentals as well as fruits and vegetables.

Some of those plants have been selected for the Louisiana Super Plants program, which promotes plants that are “university tested and industry approved” as top performers in Louisiana landscapes. More than 30 plants have been named Super Plants in the past six years.

Allen Owings, resident director at the Hammond Research Station, gave a tour of the Sun Garden at the station, where attendees saw a number of Super Plants. The 2016 selections include Evolution series salvia, which are available in white and violet and are easy to grow from seed; Serenita Raspberry angelonia, a good choice for a summer bedding plant; and Miss Schiller’s Delight viburnum, a native shrub that can be used in place of Indian hawthorn.

Also growing in the Sun Garden are 2015 Super Plants, including henna coleus, Fireworks pennisetum, Homestead Purple verbena and Leslie Ann camellia. Attendees also got a preview of 2017 and 2018 Super Plants selections, and saw “Plants with Potential,” which are less common ornamental plants that perform well in landscapes.

LSU AgCenter plant doctor Raj Singh, right, talks about plant diseases at the annual Margie Jenkins Azalea Garden Horticulture Lecture Series and Industry Open House at the AgCenter Hammond Research Station on May 6. Photo by Olivia McClure/LSU AgCenter

Allen Owings, research coordinator at the LSU AgCenter Hammond Research Station, right, gives a tour of the Sun Garden to attendees of the annual Margie Jenkins Azalea Garden Horticulture Lecture Series and Industry Open House on May 6. Photo by Olivia McClure/LSU AgCenter

People look around the grounds of the LSU AgCenter Hammond Research Station as research coordinator Allen Owings, left, talks about the Louisiana Super Plants program during the annual Margie Jenkins Azalea Garden Horticulture Lecture Series and Industry Open House on May 6. Photo by Olivia McClure/LSU AgCenter