Brown Patch in Lawns

I have been seeing symptoms of brown patch on some lawns this past week. Brown patch is caused by the fungal pathogen Rhizoctonia solani and thrives in mild, moist conditions. Prior to the recent freeze, we have seen mild and moist conditions recently and this has caused this disease to be prevalent. We typically see the highest levels of this disease primarily during the spring and fall.

The recent mild weather has caused some lawns such as St. Augustine to remain in a state of mild growth and not going into dormancy, especially in protected areas. This atypical weather pattern may cause many lawns to have increased disease pressure during the late winter period. Remember, that we do not fertilize warm-season lawns until the first week of April in South Louisiana. If you have brown patch symptoms, you may want to hold back on fertilizing at all this year or until you get this disease in check. Increased nitrogen fertilizer enhances most lawn diseases.

Foliage of affected grass may be killed in a few hours. Foliage near the soil line is infected initially. This disrupts the transport of nutrients and water to the upper portions of the plant and can cause death. Weeds are usually not too far behind this disease.

St. Augustine and centipede grass are usually more affected than Bermuda grass. Bermuda and Centipede lawns are primarily dormant now. The initial symptoms of this disease are yellowing and then wilting of the foliage. The affected leaves will dry and turn reddish brown to a straw color of brown. This area (usually circular) may grow to several feet in diameter if unchecked.

When diseased leaves are pulled, they will separate very easily at the base from the rest of the plant. The basal portion of these leaves is often rotten and brown. Some tan to brown threads of the fungus are often visible. Sprigs that survive often grow and recover from the center leaving a donut appearance.

This disease can be prevented by following a well-balanced fertility program and by not over-fertilizing your lawn. The spread of this disease can be slowed by less frequent mowing and the collection of fungus-bearing clippings.

Several fungicides will do a good job in controlling brown patch. These include: protectant fungicides such as iprodione (Chipco), mancozeb (Dithane), PCNB or captan. Fungicides containing thiophanate-methly are systemic products you can use in a disease management program along with the protectant fungicides. ALWAYS READ AND FOLLOW LABEL DIRECTIONS.

I recommend that you secure a copy of the Louisiana Lawn Best Management Practices (BMPs) publication, number 2930 from the local Extension office or at www.lsuagcenter.com. This is an excellent resource that you can keep for this and other turf problem solving through research-based information from the LSU AgCenter.

Pruning Newly Planted Citrus

The primary purpose of pruning young nonbearing trees is to shape the tree so that scaffold branches will be well distributed. This initial pruning helps bring the tops of the plants and the root system into balance. It also stimulates good scaffold branch development. If scaffold branches are selected properly, the weak narrow crotches and downward growing branches can be eliminated and future breakage under heavy fruit loads can be avoided. Proper selection of scaffold branches also will reduce the large pruning cuts in the future years.

After the selection of the scaffold branches, only limited pruning is needed on citrus. All pruning on older trees should be done in February. Pruning trees of bearing age is practiced to thin out thick growth to spray and harvest easily. The removal of long vigorous growing shoots that stick up at the top of the tree will help to control the size of the tree. These long shoots should be traced to where they originate on larger branches and cut off flush at the point of attachment.

Dead branches, branches crossing over each other, water sprouts arising from the center of the tree and branches touching the ground should be removed. When pruning, cut all limbs flush at the point of attachment.

Peach and Japanese plum (most southern plums) trees bear their fruit on one-year-old wood. Because pruning stimulates this type of growth, it is the best means available to assure an annual supply of this essential fruiting wood. Japanese plums also produce fruit on spurs and should not be pruned as much as peaches.

Pears, apples, European plums and native plums bear their fruit on short growth structures called spurs. These fruiting spurs grow little each year, and excessive pruning is not advisable. Removing spurs may reduce fruiting.

Do not prune pear trees heavily after the third or fourth year. Heavy pruning can be risky because it often stimulates excessive growth susceptible to fire blight. With mature pear trees, limit pruning to broken and diseased limbs.

Question of the Week: What is the average time between planting Irish potatoes and harvest?

Answer: The time frame ranges from 90 to 120 days depending on the variety and the environmental conditions the plants are exposed to. The home gardener is doing a good job if he/she can dig potatoes by Mother’s Day.

The LSU AgCenter Extension Service office in Thibodaux is located on 402 West 5th Street, in Houma on 511 Roussell Street and in Franklin on the third floor of the St. Mary Parish courthouse. For more information on these or other horticultural topics, call me at 985-446-1316 or email me at bhfletcher@agctr.lsu.edu or check out the LSU AgCenter website at www.lsuagcenter.com