A leaf infected with a fungal disease. Image: researchgate.net

Magnolia Leafspot

Lisa brought some leaves to our office from her southern magnolia trees with very large spots like the leaf shown in the image. Lisa’s leaf is probably infected with a Phyllosticta fungus. According to a website of Oklahoma State University Extension, many plants are susceptible to this disease: boxelder, cherry, crape myrtle, holly, leucothoe, magnolia, maple, sycamore, and many others. Dr. Raj Singh, the AgCenter’s “Plant Doctor” made these treatment recommendations:

• Spray with fungicides containing myclobutanil or propiconazole as an active ingredient may be helpful in minimizing damage.
• Avoid any abiotic stresses including drought.
• Maintain a proper fertilization program.

Kieffer Pear. Illustration: D.G. Passmore, USDA Pomological Watercolor Collection.

Pear Varieties

A gardener asked AHA which pears are best for table fruit, and which are best for canning. AHA consulted with his Master Gardeners, and they shared their recommendations:

• Canning: Kieffer, Orient
• Table fruit: Bartlett, Hosui, Pineapple, Baldwin

Mary Ferguson, a horticulture agent with the AgCenter, shared these notes about pear varieties, “Retired LSU fruit crops professor Dr. Charlie Johnson says that Kieffer and Orient are the varieties that he has observed produce most reliably in Louisiana. These are both ‘hard’ pears. While it is generally suggested that two varieties of pear be planted, both Kieffer and Orient can produce a crop without cross pollination. Other pears suggested for southern Louisiana include Baldwin and Spalding.

Pineapple, Hood, and Flordahome have performed well in climates like that of southern Louisiana, though these may bloom too early in some years due to their low chilling requirement and thus have flowers killed by a late frost….”

Whiteflies on a cucumber leaf. Image: David Riley, U. Georgia, bugwood.org.

Whiteflies

Bobby is fighting a pest problem in an enclosed site, “I am having problems with whiteflies. I have sprayed multiple times, but they keep coming back. Do you know of a pesticide fogger that I can use without removing the plants from my seed shed?” Dan Gill, retired horticulture specialist, wrote about treating whiteflies in ornamental plants, “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 temperatures are cooler. Check the label carefully for the safe and proper use of these pesticides as well as the list plants on which they may be used.”

Primrose jasmine. Image: Val Denley, Master Gardener

Primrose Jasmine

Val, a Master Gardener, sent an email with a note of frustration, “I have just been through ‘55 Yellow Blooming Flowers’ to no avail as to identify this sometimes out-of-control wild flowering shrub. Can RSFF help? Thanks.” AHA consulted Jason Stagg, Senior Landscape Manager at the AgCenter’s Burden Center, and he thinks the yellow flower is a Chinese plant called primrose jasmine. This plant requires a lot of space and can become “brush pile” headache without regular pruning.