Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Posts Tagged ‘disease’

Canola Sclerotinia Problems

Posted by romeethredge on March 12, 2015

We are starting to see Sclerotinia Stem Rot in Canola now. It can be a very serious disease here in the winter. Fortunately we don’t see it in our summer crops this far south. We often spray a fungicide to help control it.

Consultant Wes Briggs sent me this photo yesterday showing the readily apparent problem. He says he has been seeing a fair amount of it this week. He saw some last week.

 

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Sclerotinia stem rot, also known as white mold, is caused by the soil-borne fungus Sclerotinia sclerotiorum. It has a wide host range and can attack almost any broadleafed plant, but it is not a problem on grasses. This fungus is active only during cool, wet weather. In Georgia, the fungus is active only during the winter months and has never been a problem on any of our summer crops, although it has been present in the soil throughout Georgia for many years. Infections on canola have not been observed before December, and new infections are rarely seen after April.

The fungus survives the hot summer months as sclerotia in the soil. Sclerotia can survive for a year in southern Georgia soils and for up to 2 years in northern Georgia with no decline in viability. Viability declines over subsequent years. Any time during the winter, if the soil becomes very wet for several days, sclerotia can germinate in two ways: by producing mycelium in the soil or by producing small mushroom-like apothecia that produce spores above the soil surface. These spores are disseminated by wind and rain to other parts of the field or to adjacent fields.

Neither the mycelium nor the spores can invade a healthy canola plant directly. Both must become established in dead organic matter in contact with healthy tissues to initiate disease. Once a disease lesion is initiated, the fungus secretes acids and enzymes that kill additional plant tissues. The fungus can rapidly destroy small plants or girdle the stem of large plants if the weather remains wet and cool.

There are no canola cultivars with resistance to stem rot and, in very wet seasons, some plants may be killed in any field in Georgia. In drier years, fewer plants will be killed by this disease. Poorly drained fields suffer losses much more frequently than well-drained fields. The most important control measure is to select well drained fields that have not had canola or another susceptible crop for the past two winters.

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Posted in Agriculture, Canola, Plant Pathology | Tagged: , | Leave a Comment »

Peanut Leaf Scorch

Posted by romeethredge on June 12, 2014

Peanut Leaf Scorch is showing up, but is nothing to be concerned about.

 Leptosphaerulina crassiaca is the causal organism of Peanut Leaf Scorch. We’re seeing some of this now. This was in a field of Tiftguards variety peanuts that had Cruiser Max seed treatment, so we knew it was not Thimet burn.  Dr Bob Kemerait, UGA Extension Plant Pathologist, says it causes some leaf symptoms but does not cause yield loss in peanut. Our normal fungicides used in peanut probably help with this as well.

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Posted in Agriculture, Peanuts, Plant Pathology | Tagged: , | Leave a Comment »

Wheat Update

Posted by romeethredge on April 4, 2014

Wheat is at flag leaf , boot or heading stage in most fields, now.  The top leaf or flag leaf is next to the grain head and supplies most of the photosynthate to produce grain. So we want to protect this leaf and the head from plant disease.

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Some varieties have genetic resistance to plant diseases at some level ,but we find that our diseases shift races and we can loose resistance pretty easily at times. Most growers seeking high wheat yields apply a fungicide to wheat just after the heads emerge, to protect the flag leaf from leaf rust and other diseases, and also protect the head.

I just heard that they found leaf rust in some plots in Plains. See below for more info.

 

Dr. Alfredo Martinez-Espinoza, UGA Extension Plant Pathologist, gives us the following report concerning wheat.

Wheat Foliar Disease Update-4/4

Wheat Leaf Rust. Just a quick update on wheat leaf rust: leaf rust was observed on an early-planted, highly susceptible variety in the UGA CAES Southwest Georgia Research and Education Center in Plains GA on April 2. There are no indications or reports of wheat leaf rust in other areas of GA. However, environmental conditions are becoming conducive for leaf rust epidemics to develop. Therefore, field monitoring for leaf rust and/or Stagonospora (leaf-glume blotch) in your area is advised.

If leaf rust is present in your field this warrants a fungicide application, the options are:

 

Triazoles

 

metconazole (Caramba)

propiconazole (Tilt, Propimax)

prothioconazole (Proline)

prothioconazole + tebuconazole (Prosaro)

tebuconazole-containing products (Folicur, others)

Strobilurins

 

azoxystrobin (Quadris)

fluxastrobin (Evito)

picoxystrobin (Aproach)

pyraclostrobin (Headline)

Mixed mode of action

 

fluoxapyroxad + pyraclostrobin (Priaxor)

propiconazole + azoxystrobin (Quilt, QuiltXcel)

propiconazole + trifloxystrobin (Stratego)

prothioconazole + trifloxystrobin (Stratego YLD)

pyraclostrobin + metconazole (Twinline)

tebuconazole + trifloxystrobin (Absolute)

A complete list of wheat fungicides, rates and specific remarks and precautions can be found on page 58 of the 2013-14 Wheat Production Guide or on page 484 of the 2014 Georgia Pest Management Handbook. Always read product label for fungicide applications restrictions. Take a look at pages 9 to 11 of the 2013-14 Wheat Production Guide for wheat variety responses against leaf rust.

http://www.caes.uga.edu/commodities/fieldcrops/gagrains/documents/2013-14WheatProductionGuide.pdf

For more information on wheat leaf rust go to

http://plantpath.caes.uga.edu/extension/plants/fieldcrops/WheatLeafRust.html

Posted in Plant Pathology, Wheat | Tagged: , | 2 Comments »

Wheat fusarium foot rot

Posted by romeethredge on May 4, 2012

Fusarium foot or stem rot of wheat can be serious if everything wrong works together.

This year this has been the case in some fields.  We see this most often in droughty conditions, in fields that have had several years of wheat in them, especially when there’s a hardpan, or there has not been any deep tillage, and untreated seed are more susceptible.

Here’s some comments concerning this disease by our UGA Extension Plant Pathologist Alfredo Martinez, when I sent him a sample of the wheat in photo below.

” Typical pink and brown discoloration characteristic of fusarium foot rot was observed in the stem at the soil line. Dry soils promote the disease and drought stressed plants are more susceptible to the infection for Fusarium. Untreated seed and planted too deep will be more susceptible to fusarium infections. Cultural practices that leave crop residue on or near the soil surface will promote the disease. Rotation to non-susceptible crops (broadleaf) will help to reduce inoculum levels.”

 

Posted in Plant Pathology, Wheat | Tagged: , , | Leave a Comment »

 
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