A sycamore sapling with a probable case of anthracnose. Image: Denae Greene, DeRidder, LA

Sycamore Anthracnose

Denae had been landscaping and then reported a concern, “We have a sycamore tree we purchased at Forest Hill and have it planted. It was thriving and suddenly the leaves were turning brown and falling off. It was planted before the hard winds and flooding we had a couple of weeks ago. Could this be due to wind damage? I am including pictures for you.”

Denae probably has sycamore anthracnose, a native fungal pathogen. This disease is more of a cosmetic nuisance, and trees will resist and persist despite this disease. Gathering and destroying infected leaves reduces the number of fungal spores that can infect healthy leaves. Fungicides are unneeded unless there is a very rainy season. The London planetree has a similar appearance to the American sycamore, but it expresses resistance to anthracnose.

A blend of soil from several planting sites are used for soil testing. Image: LSU AgCenter.

Soil Sampling

AHA visited Tracy’s yard after last year’s brutal weather to help her grass recover. One of the restoring practices would include soil testing. Tracy emailed and asked, “Does the soil sampling work the same for a garden bed as it would for a lawn?” The short answer to Tracy’s question is “yes.” The only difference is to name the “crop” on the soil sample form. The “crop” could be turfgrass or could be cut flowers. The AgCenter has soil sample kits at its offices.

Tiger fig after pruning. Image: LSU AgCenter

Fig Pruning

Alex of Sugartown has a fig tree and wanted to know, “I pruned my figs in January, and they have sprouted back. I am trying to get some of them to one main branch. Should I do it again now to cut back the extra shoots that I do not want or wait till next fall?” Thinning the sprouts now will enable the tree to put its energy into the fruit. Here is a note about pruning from the AgCenter’s publication, Figs for Commercial and Home Production, “Regular pruning increases fruit size because of its thinning effect. Heading back of main branches and removing dead, weak and undesirable wood will accomplish this purpose. If pruning is done regularly, most cuts can be made with pruning shears.”

The "shepherd's crook" in the red circle is a symptom of fire blight. Image: Bryan Chaddrick, Evangeline Parish

Fire Blight

Bryan of Evangeline Parish asked about the leaves on his apple trees and sent pictures. One of his pictures has a very diagnostic symptom of fire blight (FB), a bacterial disease. AHA believes this tree is in the early stages of FB, and eventually, the leaves will look scorched as if the leaves were exposed to heat. Dr. Raj Singh, the AgCenter’s “Plant Doctor” reports, “The bacteria can then be dispersed to nearby blossoms or tender young shoot tips either by splashing water or by insects, especially honeybees.”

Raj recommends these treatments for FB,” The natural resistance of the plants can be further enhanced by applications of fosetyl aluminum (Aliette) or one of the phosphite fungicides. Careful pruning to remove infected branches will also help to reduce the amount of inoculum present in the spring. When pruning, be sure to cut back far enough into healthy tissue to ensure infected tissues are removed completely. Also be sure to clean and disinfest cutting tools frequently using a 10-percent-bleach solution (or other suitable disinfectant) to prevent the accidental spread of the bacterium. A weak solution of copper fungicide may be applied during the bloom period to reduce infection of the flowers, but such applications must be made every 4-5 days during the bloom period to be even moderately successful. As an alternative, streptomycin sulfate may be used, but repeated use of this antibiotic eventually will lead to the development of resistance in the bacterial population.”