Impatiens Downy Mildew Makes Its First Confirmed Appearance in the Louisiana Landscape

We had our first confirmed report of downy mildew on Impatiens walleriana here is south Louisiana this weekend. My wife commented that one of the double impatiens that she’d gotten at one of the big box stores a couple of weeks ago was not looking all that good, and sure enough it has downy mildew caused by Plasmopara obducens. With the onset of warm, drier weather, I wouldn’t expect it to become a major problem, but our nighttime temperatures are still quite favorable and as long as we have 3- to 4-hour periods of dew on a regular basis, the disease will likely continue to develop. None of the fungicides readily available to homeowners are particularly effective in controlling the disease, so it’s probably best to remove and destroy any infected plants as soon as they are found.

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Sclerotinia Diseases in the Vegetable Garden

Last week was our annual tour of commercial vegetable growers in West Feliciana Parish. AgCenter personnel and several of the commercial growers met and spent the morning touring the various growers’ operations. We saw some early blight on tomatoes, but the highlight of the day was the white mold on beans and timber rot on tomatoes, both caused by the fungus Sclerotinia sclerotiorum. The cool nights, wet weather and close spacing of the plants made the conditions ideal for the development of these diseases.

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Leaf Roll in Tomato

Once again we’re seeing quite a bit of leaf roll in tomatoes this year. This is a physiological problem that has been attributed to a number of causes, including excessive nitrogen, excess moisture and extended periods of warm dry weather as we transition from spring to summer. Certain varieties tend to be affected more than others, and indeterminate varieties seem to be more prone to the condition than determinate varieties.  The good news is that it doesn’t really hurt production.

Physiological leaf roll of tomato.

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Recent Rains Bring on Diseases in the Garden

André Brock and I visited a 100-year-old gardener in West Feliciana Parish the other day.  This gentleman has a beautiful garden and said he spends an hour a day tending to it, although his daughter helps with the harvesting as his eyesight “isn’t what it used to be”.  He had what he thought was “blossom end rot” on his tomatoes, which seemed a little odd considering the amount of rain we’ve had this spring. (Blossom end rot is a calcium deficiency that we typically see more often in dry years.) It turned out that his tomatoes have buckeye rot,  a disease caused by the soil-borne water mold Phytophthora when rain splashes infested soil onto the lower fruit. We advised him to remove all of the infected fruit from the garden and put down a layer of either newspaper or plastic mulch to prevent any more splashing soil from splashing onto the fruit.

This same gentleman had originally called trying to find out why his blackberries had flowered nicely, but once again produced no fruit.  The variety he is growing is Black Satin, which is supposed to do well here in Louisiana and is self-fertile, but we suspect that the problem is due to poor pollination as our weather this spring has not always been the best for bee activity.

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it’s Time to Control Early Blight on Tomatoes

Visited several commercial vegetable growers in Livingston Parish with Kenny Sharpe yesterday. Starting to see early blight showing up on tomatoes at various locations and one tomato field with bacterial speck causing a significant amount of damage on the variety Applause. Warm, wet, humid weather is ideal for the development of both of these diseases and growers should be putting on preventative sprays of chlorothalonil or one of the strobilurin fungicides to keep the early blight in check.

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DuPont’s Fontelis™ fungicide is now registered for use in Louisiana

I received notice today that DuPont’s Fontelis™ fungicide is now registered for use in Louisiana. The active ingredient is penthiopyrad, a carboxamide (SDHI) fungicide in FRAC group 7. Fontelis™ is labeled for the control of Botrytis gray mold, powdery mildew and Alternaria diseases, among others, and is labeled for use on strawberries, stone fruits and most vegetables. The pre-harvest interval ranges from 0-3 days for strawberries and most vegetables.  The same active ingredient is labeled as Vertisan™ for use on sweet corn and field crops.  For more information, see

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Current Status of Citrus Greening in Florida

Here’s the latest on attempts to deal with citrus greening (huanglongbing) in Florida from at

The most troubling bit of news in the article is that University of Florida plant pathologist Jim Graham “cited research by U.S. Sugar, also one of Florida’s largest citrus growers, that shows 43 percent of the state’s 62.5 million orange trees were infected by greening as of last year. The infection rate continues to double each year…”

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