Louisiana Master Naturalist Program-Greater New Orleans Chapter

Spiders and bats and gators...OH MY!

Alligator mississippiensis  at Jean Lafitte National Park

Impacts of Katrina on Bayou Sauvage lesson

The Louisiana Master Naturalist Program in the Greater New Orleans area is upon completion of a successful intensive series of naturalist workshops. 

What is a naturalist? A naturalist is an individual who studies natural history of the world, and attempts to understand the ecology, biology and ecosystem functions of living and non-living things. Through careful observation, students were trained how to look at nature in its complexity, in an attempt to understand and capture the beauty of ecosystems of Southern Louisiana. The training sessions spanned from late February and will continue to early June, and many ecosystems have been the palette for study. These included Jean Lafitte National Park, Bayou Sauvage Wildlife preserve, Northlake Nature Center & Big Branch, Turtle Cove, UNO Cerf, The Louisiana Nature Center, and Bayou Dupont. Students have learned a plethora of systems ranging from botany, mycology, zoology, hydrology, geology, and lichenology. 

Steminitis sp. at 2013 BioBlitz at
Jean Lafitte National Park

The ultimate goal is to "prime" students to look at nature and make connections with specific observations. The class is not designed to create world renowned experts, but to educate students about the natural history of Louisiana. 

There will be a class offered every Spring and Fall, and chapters in other areas of the state are in the works. More info to follow on the future classes. If you would like to get on the La. Master Naturalist-GNO list serve please email lamasternatgno@gmail.com.

Wood ear fungus, Auricularia sp. at Louisiana Nature Center

Blossom-end rot of tomatoes

Lately, I have received a lot of phone calls about this particular disorder, so I thought I would share some information and management strategies for this particular disorder.

Blossom-end rot is not caused by living causal agent, like a pathogen, but rather, a deficiency in calcium. This disorder is common in tomatoes, peppers, squash, and watermelons. If you had your soil tested, and the results suggested you have an adequate level of calcium in your soil, how did your tomatoes get a deficiency in calcium?

NCSU PDIC_Lookabaugh

Calcium moves quite slowly in plants and even slower in fruit, so adequate levels of calcium could still result in this deficiency. Indirectly, this disorder is caused by excessive levels of moisture or not enough moisture. Considering the excessive rainfall New Orleans received last month (about the time your tomatoes were in flower), it is not surprising to see a lot of blossom end rot. This disorder can affect all ages of plants, but is more common in 1/3-1/2 grown tomatoes. 

It begins as a small, water-soaked spot and develops into a dark brown, leathery spot that may involve half the fruit. The surface of the spot shrinks and becomes flat or sunken. Blossom-end rot is caused by a lack of calcium in the developing fruit. The uptake of calcium from the soil by the tomato plant can be reduced by fluctuations in soil moisture – either excessively wet soil or excessively dry soil.

The disorder commonly occurs when plants are growing rapidly and luxuriantly early in the season and are then subjected to prolonged dry weather. The disorder may be more serious on the windward side of a garden and on staked tomatoes rather than on unstaked or bushy plants.

Prevent blossom-end rot by maintaining a soil pH around 6.5 and uniform soil moisture by irrigating and mulching, and avoid heavy applications of nitrogen.

Control blossom-end rot by spraying foliage with 2 level tablespoons of 96 percent calcium chloride in 1 gallon of water at seven- to 10-day intervals. Do this for three to four applications. Begin spraying with first appearance of symptoms. Overdosing plants with calcium chloride may result in leaf burn. Spray on cloudy days or wait until the sun is low.

Calcium nitrate also may be used. Use 1 rounded teaspoon per plant. Apply calcium nitrate into the soil about 8 inches from tomato plant stems. A second application may be needed several weeks later as well. If foliar applied, use 2 level tablespoons per gallon of spray applied late in the day.

Spring is here and so are plant diseases!

Azalea gall caused by Exobasidium

Many times I receive phone calls from the public concerning plants in the landscape or vegetable garden becoming sickly, showing symptoms of some kind. The first feeling I get when receiving these phone calls is a feeling of excitement, as if I am a detective assigned to a case.

First things first, gather and organize the clues. The clues are the in the form of symptoms, signs and environmental condition in which the victim, I mean plant, is found. The symptoms are defined as any abnormality in “normal” growth of the plant. Signs are evidence of a pathogenic agent on the symptomatic plant; a few examples are mycelium (white fuzzy strings) and spores for fungi, and ooze for bacteria. The signs in combination with symptoms and pattern of symptomology on individual plants and/or groups of plants can paint a beautiful story for the detective or plant diagnostician.

Plant pathologists utilize the disease triangle as their hierarchical concept to determine the disease. Within the disease triangle, there are three parameters that work in a matrix to determine level of disease; they are susceptible host, pathogen, and environment. The level of each parameter will work in synchrony to determine the output, which is disease progress and severity.

I will survey some common problems I have seen this Spring:

Fire blight of pear and relatives:

Shepherd's crook symptom on flowering pear.

Fire blight is a disease common in Southern Louisiana caused by the bacterium Erwinia amylovora. Over 130 species of plants including: pear, apple, quince, hawthorne, contoneaster and mountain ash, are susceptible to this pathogen. Symptoms are observed as Shepherd’s crook necrotic foliage, in which the leaves appeared scorched and remain on the petiole or stem. This disease has been observed on Pyrus spp. including ornamental and fruit species. This disease is favored by warm, wet weather and spread by pollinators and wind driven rain. Improper fertilization, either too much or too little also favors this disease. Managing fire blight in the landscape is mostly management of fertilizer, planting resistant cultivars, pruning infected wood and lastly, chemical control.

Fire blighted pear tree

When pruning out diseased tissues, cuts should be made 12-14” down from the symptomatic tissues in the growing season and 8-10” down from symptomatic tissue in the dormant season.  Pruning shears should be sterilized with isopropanol between cuts to prevent the spread of the bacteria between cuts. Copper fungicides, such as Kocide 2000, can be sprayed following the label recommendations for the particular plant; keeping in mind copper can be phytotoxic to some plants. You should always read the label before spraying fungicides.

Powdery Mildew on rose

Powdery mildew on rose leaf

Conidia in white mat on rose flower

Powdery mildew is a disease caused by a fungus and can affect many plants including roses, crapemyrtles, dogwoods and many cucurbits. The disease is usually favored by warm dry weather by day, and cool damp weather by night, usually falling in or around the spring and fall for southern Louisiana. The disease is observed with new growth being distorted and dwarfed often covered in a mat of white “fuzzy stuff”, and old growth and flower buds appearing twisted and distorted also covered in white fuzzy growth. The white fuzzy material are the asexual spores of the fungus called conidia. The conidia are produced in chains and are abundant. This is how the pathogen spreads so quickly under favorable environments. Proper pruning to thin out the canopy, proper fertilization, and avoiding overhead irrigation can help prevent this disease. This disease can be managed with the following sprays:  3% baking soda and horticulture oil solution, noting the temperature limitations on oils, chlorothalonil, and copper sulfates. You should always read the label before spraying fungicides.

Conidia on rose leaf magnified at 4.5x with dissecting microsope

Daylilly Rust

streaking yellow symptom on laylilly

Daylilly rust is a disease caused by the fungus Puccinia hemerocallidis. The most obvious symptoms of this disease are yellow streaks  turning brown with age on the upperside of the leaf coupled with orange pustules of spores found on the underside of the leaf observed as yellow to orange raised areas at individual lesions. The disease was first identified in the United States in 2000, and quickly spread to 30 states by 2001. The disease is spread by wind carried spores that are developed on lesions. The rusts are a particularly interesting group of diseases in that many of the species of fungi that cause rusts require two completely distinctive hosts to complete their life cycle. In the case of daylily rust, daylilies are the primary host, where species of Patrinia  are the secondary host where sexual reproduction occurs and new genetics are generated. The best preventative method of management is by using resistant cultivars, and avoiding highly susceptible cultivars. Lists of resistant and susceptible cultivars can be found at this website: http://plantclinic.cornell.edu/factsheets/daylilyrust.pdf.  Another management strategy to limit the severity of this disease is to remove infected, dead tissues in the winter and burning or sending them to a landfill. In addition, daylily growers should avoid close proximity plantings of Patrinia spp. and Daylillies so the rust cannot complete its life cycle. Preventative fungicide sprays can help reduce the devastation of this rust disease. A few sprays available to the home owner are under the chemical names neem oil, potassium bicarbonate, sulfur, or Bacillus subtilis (Serenade, Plant Guardian). You should always read the label before spraying fungicides. 

Rust pustules on underside of daylily leaf.

Phytophthora foot rot of citrus

One sided blight of citrus typical of foot (root) rot

foot rot at graft union on navel orange tree

Phytophthora foot rot is the most frequently encountered disease on trunks of citrus trees in Louisiana. The disease is caused by a soilborne fungus, and wet conditions during the spring favor fruit rot development. Initial symptoms include water soaking of the bark that appears as a dark spot on the trunk. At first, the bark appears firm, but with age it becomes cracked an may shred as it dries. This disease is managed indirectly by managing good drainage of the planted area. Citrus trees should be planted in a well-drained area, and weeds and mulch should be avoided under the tree. Planting in raised beds with adequate drainage and pruning low hanging branches to allow air movement around the tree are the best management strategies for the homeowner.