Tag Archive: disease

Potassium Deficiency in Hay Fields can Enhance Fungal Disease Issues

Potassium Deficiency in Hay Fields can Enhance Fungal Disease Issues

Jackson County Pensacola bahiagrass hayfield that was yellow and stunted at the end of June. The orange arrows point out green clumps of grass where the fire ant mounds were located. Photo credit: Doug Mayo

The Yellow Bahiagrass Hayfield

At the end of June, a Jackson County rancher noticed something strange about his hay field.  The field was gradually turning yellow and was not growing well.  Typically plants turn yellow as the result of a nitrogen deficiency, but this field had been fertilized for hay production.  Upon inspection, the leaves were yellow with dark brown spots, as in the photo below.  There were also green clumps scattered across the field.  The green clumps of grass were growing over fire ant mounds across the field.  Pensacola bahiagrass commonly gets Dollar Spot fungus that causes the tips of the leaves to wilt and turn brown or senesce.  This infection, however, was much different than Dollar Spot, so Dr. Ann Blount, UF/IFAS Forage Specialist, was contacted to set up a field visit.

Bipolaris leaf spot on Pensacola bahiagrass leaves. Photo credit: Doug Mayo

Dr. Blount had never seen this type of widespread fungal infection in Pensacola bahiagrass either, so samples were collected and sent to the UF/IFAS Plant Disease Diagnostic Clinic, in Quincey .  As it turns out the field was infected with Bipolaris Leaf Spot (Bipolaris micropa) or leaf blight.  In older publications, leaf spot was referred to as helminthosporium.  Bipolaris leaf spot is fairly common in Bermudagrass hayfields, but is not at all common in bahiagrass, but there have been documented cases of bahiagrass infestation in the Southeast.  Bipolaris can also infect small grains, and turfgrasses under the right conditions.

The Plant Diagnotic Report provided the following information from literature on this particular fungal disease:

Bipolaris micropa may cause extensive damage when the pathogen attacks crown, stolons or rhizomes.  This fungus can grow saprophytically on dead tissue and sporulates profusely when dry debris is re-wetted. During periods of cool, moist weather fungal spores may be spread to healthy leaves by wind, rain, irrigation, water, equipment or people. Moisture films on leaf surfaces are necessary for infection mainly under cool and wet conditions. 

June 2017 was not that cool, but it was certainly very wet. The Marianna FAWN station located a few miles from this field recorded 11.5″ of rain that fell on 19 of the 30 days in June.  Cutting and drying hay was extremely challenging in June, so this particular hay field was much more mature than normal. Combine constant wet conditions with very mature grass, and the conditions were right for fungal disease build up.  Even so, this just does not normally occur in bahiagrass fields.

In addition to the diagnostic disease sample, a diagnostic soil sample was collected from several areas suffering from the greatest infection.  The following were the results of the soil test report.  The pH at the site was 5.6, above the target pH for the crop, so liming was not an issue. There was a considerable deficiency in soil potassium, however.

UF/IFAS diagnostic soil test report from bipolaris leaf spot hayfield. The potassium level was very low, 11 ppm.

Hayfield Fertilization

Bipolaris leaf spot on Pensacola bahigrass. Photo credit: Doug Mayo

Nitrogen (N) fertilization is the key nutrient required for forage plant growth. Adding nitrogen fertilizer will boost yields of all types of crops. Put another way, “Nitrogen is the gas that makes grass grow.”  Potassium (K20), also commonly referred to by farmers as potash, on the other hand is an essential nutrient, but the yield boost from K20 fertilization is more subtle.  Hence, there is a temptation to simply apply nitrogen fertilization to hay fields and annual forages to reduce costs, but there can be a hidden cost from repeated use of this practice.

Nitrogen is very water soluble, so when we get into wet seasons with heavy rainfall and saturated soils, the nitrogen fertilizer can be washed away from plant root zones.  While not as soluble as nitrogen, potassium can also be washed below the root zone with heavy rains or continuous rainfall.  In general, potash will remain in the root zone longer than nitrogen, but in periods of heavy rainfall, like the month of June, it can become very short.

The immune system is one of essential systems in plants relies on an ample supply of potassium.  When there is a deficiency, plants cannot fight off challenges like fungal diseases.  Such is the case in forage grasses and annual forages with Bipolaris leaf spot (Bipolaris micropa).   Dr. Jim Marois, retired UF Plant Pathologist, once told me, “Leaf spot is normally like a common cold for plants.  Under normal conditions plants can fight if off and prevent major issues.  But if a plant is under major stress, the cold becomes pneumonia, and the plants suffer significant yield loss.”  Certainly a serious potassium deficiency can stress the immune system of forage plants.

This also helps explain why the clumps grass over the fire ant mounds were green and more vigorous. The fire ants import nutrients from the surrounding area as they haul in feed for the ants in the mound.  They also aerate the soil to reduce soil compaction in the root zone.  So in this case, the ant mounds provided enough potassium to boost  the health of the plants surrounding their mound, which allowed them to fight off the fungal infection.  At least in this case, the fire ant mounds were good.  Incidentally, fire ants are also the number one biological control of armyworms, so they are not all bad.  I do understand their mounds are really hard on hay equipment, but it was certainly interesting in this case.

For every ton of hay or baleage harvested, there is a net loss of soil nutrients that is exported to other locations where the harvested forage is actually fed. In general, harvested grasses and annual forages need at least a 4:1:3 ratio of N:P:K.  If you fertilize with 50 lbs. of N, then at least 37.5 lbs. K20 should be added.  In reality though, based on research trials, the actual removal of N and K are nearly equal, so  it is essential to soil test annually for both phosphorous (P) and potassium (K), to ensure the plants are getting the balance fertilization needed to maintain a healthy stand.

Summary

This was a very unique situation.  Biploaris leaf spot is a much more common problem with small grains and Bermudagrasses than bahia.  Dr Blount has been working with bahiagrass for over 40 years, and myself for almost 30 years and neither of us had run into this situation before.  You might say this was a perfect storm for fungal growth with continuously wet fields, frequent rainfall, very mature grass, and low soil potash.   There are no fungicides registered for bipolaris control in forages, so the best control options are prevention.  This situation serves as a reminder of why it is important to diligently follow the standard recommendations for quality hay production, even in bahiagrass fields:

  1. Soil test annually and use a balanced fertilizer for hay production with at least a 4:1:3 ratio for N:P:K
  2. Prevent heavy thatch build up that can serve as a host for fungal diseases, either through dormant season burning or frequent hay harvest
  3. If irrigation is part of the management system, avoid irrigation late in the day and after dark to prevent long periods of wet leaves
  4. Harvest hay every four to six weeks to improve hay quality and to reduce fungal disease build up
  5. ith heavy infections of fungal disease, forage removal through hay harvest is the best option for control.  Even though hay quality will certainly be reduced, it is a better option than bush-hog type mowing that will leave diseased thatch in the field.  With adequate fertilization, the regrowth should be able to overcome the disease challenge.
  6. If hay or baleage harvest is not feasible, consider grazing to remove very mature forage before fungal populations can build up to the point of yield loss

For more information related to this topic, use the following publication links:

UGA Leafspot Diagnosis and Management in Bermudagrass Forages

Getting the Most out of Bahiagrass Fertilization

PG

Author: Doug Mayo – demayo@ufl.edu

Lead Editor for Panhandle Ag e-news – Jackson County Extension Director – Livestock & Forages Agent. My true expertise is with beef cattle and pasture management, but I can assist with information on other livestock species, as well as recreational fish ponds.
http://jackson.ifas.ufl.edu

Doug Mayo

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2017/07/21/potassium-deficiency-in-hay-fields-can-enhance-fungal-disease-issues/

Corn Disease Management: When to Apply a Fungicide?

Corn Disease Management: When to Apply a Fungicide?

Southern Rust in field corn at the UF/IFAS Plant Research Center, Citra. Photo: Nick Dufualt.

By Nicholas Dufault and Maria C. Velez-Climent, UF/IFAS Plant Pathology Department

Recently, southern corn rust (Puccinia polysora) (Figure 1) was identified in Seminole County, Georgia and southern Alabama. With so many cloudy, and rainy days lately many producers have been asking if it would be beneficial to spray a fungicide? Spraying at the right time can be useful in protecting yields, especially with diseases like northern corn leaf blight and southern rust, which spread quickly and cause significant yield losses, if left untreated. So, when is the right time to spray?

Figure 1. Typical southern corn rust signs (left) with orange to light brown, small and densely packed pustules on the surface on the top of the leaf. But, the underside of the leaf surface has yellow flecks and very few, if any, pustules. (Right)

The choice of whether or not to apply a fungicide will vary depending on several key questions. These are:

  • What is your yield potential?
  • What are the variety’s resistance traits?
  • What is the current growth stage of the corn?
  • Is disease present in the field or locally?
  • Was a fungicide already applied?

It is critical to assess how the potential yield savings from a fungicide application will affect your budget, and if resistant traits are present for the disease of interest. Budget tools, such as UGA’s corn budget, can be very helpful in this decision process. Fungicides can usually save between 5 and 10 bushels per acre, but these values can vary depending on the amount of disease present in the field. Thus, it will be critical to evaluate a range of yield savings and the impacts they will have on the overall returns.

Growth stage is also important when considering the benefits of a fungicide application. An application in the V-stages can reduce disease severity in corn (Figure 2), but often does not lead to significant yield increases (Figure 3). In general, fungicide applications around VT (Tassel) to R2 (Blister) provide the best yield savings. There are situations where sprays outside these growth stages can be beneficial and further information about growth stage timing can be found at your local extension office.

Figure 2. Box plots of disease severity ratings for southern corn rust with fungicides sprays at V5 and VT for the products indicated. The variety was Dekalb DKC66-97.

Figure 3. Yield savings in bu/A for Priaxor (4 fl oz/A) and Headline AMP (10 fl oz/A) when compared to the untreated control for single sprays at V5 and VT. Southern corn rust was the primary disease present with severity values presented in Figure 2.

The timing of the first fungicide application and deciding whether or not to apply a second application requires gathering some information about the disease. If the disease is present in the field or locally (e.g. neighboring county) and environmental conditions are conducive for disease development, a fungicide spray has a high probability of saving corn yields. Monitoring corn diseases should be primarily done through scouting, however, there are multiple resources available to help with corn disease monitoring (e.g. blogs, extension newsletter and Twitter). The decision of a second fungicide application depends on when the first application was applied, the growth stage of the crop and if conditions remain conducive for disease. Basically, it requires going through all the questions again, and assessing the impact and duration of protection from the first fungicide. About two weeks after the first application is a rough time estimate to begin considering a second application and evaluating the impacts of a fungicide spray.

The final choice to make is which product to use. Luckily, there are many quality products available for corn diseases and this choice depends on which and how many diseases are present. For general insights on product efficacy, the fungicide efficacy guide provided by the Corn Disease Working Group is a great resource. Corn fungicide application decisions can be difficult to make. If the answers to the questions above indicate a high risk for disease, it is important not to hesitate when making a decision to spray fungicides, especially since southern corn rust and northern corn leaf blight can spread quickly in the right situations.

 

PG

Author: Nick Dufault – nsdufault@ufl.edu

Extension Plant Pathologist for Vegetable and Row Crops
https://www.facebook.com/pages/Field-Veg-Plant-Pathology-Lab-at-UF/510711278961763?sk=timeline

Nick Dufault

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2017/07/04/corn-disease-management-when-to-apply-a-fungicide/

Potato Disease Management Starts with Monitoring Your Seed Stock

Potato Disease Management Starts with Monitoring Your Seed Stock

field-dickeya-potato

Figure 1: Seed borne diseases, such as blackleg shown above, can go unnoticed until it is too late. Paying close attention to the seed from production to planting can help reduce the impact of these devastating pathogens. (Photo courtesy of Clay Pederson)

By: Nicholas Dufault, Rebecca Barocco, and Sajeewa Amaradasa

There have been many concerns this year with potato seed management related to the Blackleg problem, caused by Dickeya dianthicola, in the northern seed producing states (Figure 1). Seed borne diseases, such as blackleg, can go unnoticed until it is too late. Paying close attention to the seed from production to planting can help reduce the impact of these devastating pathogens.  This has led to the general question, “What can I do to monitor for Blackleg and other seed borne disease issues?

In general, there are 3 major steps to follow when monitoring potato seed:

  1. Potato seed management starts with a seed certification. All U.S. seed producers should have a seed certification program that provides a North American Certified Seed Potato Health Certificate. These programs produce high quality seed stock, but it is important to realize it is not disease free. It is impossible to inspect every plant or seed, but through the use of multiple samples, and an understanding of the seed grower’s field history, these programs are able to limit the spread of many microbes. Buying only certified seed is one of the best ways to start reducing seed borne issues.
  2. The next step in the process is to evaluate the shipment before accepting it. This can be done by visually inspecting the lot in the shipment container or by taking samples (using a 5 gallon bucket) from various areas and examining the seed closely. These inspections are done to look for external damage to the tubers, such as bruising, splitting or wounds (Figure 2). The symptoms can indicate infection points for storage pathogens and could be a good place to sample to see if further pest damage exists. There are many pathogens that resemble physical damage to tubers (e.g. powdery scab) (Figure 2 and 3), so if there is uncertainty about a symptom contact your local extension office with questions.
    Figure 2:Damage that can occur from wounding on the left and from excessive moisture leading to enlarged lenticels on the right.

    Figure 2:Damage that can occur from wounding on the left and from excessive moisture leading to enlarged lenticels on the right.

    Figure 3: Damage from fungal pathogens with an example of Fusarium dry rot on the left and powdery scab on the right.

    Figure 3: Damage from fungal pathogens with an example of Fusarium dry rot on the left and powdery scab on the right.

  3. The last step is to monitor the seed as it is being cut. In many cases it is not possible to see the presence of a problem externally (Figure 4), but when cutting the seed you may notice internal disease symptoms (Figures 3, 4 and 5). Periodic cleaning and sterilizing of the cutting equipment is a useful tool for managing disease spread in seeds. However, once an internal seed problem is noticed, especially soft-rotting tissue, it is vital to stop all cutting until the blade can be sterilized. Many pathogens can be transmitted by unclean cutting blades, and this is one major path in which blackleg can spread through a seed lot. Monitoring seed cutting is critical to limiting potato disease issues related to seed.
Figure 4: The blackleg pathogen, Dickeya dianthicola, can infect daughter tubers and go relatively unnoticed in seed pieces until cutting. (Photo courtesy of Clay Pederson)

Figure 4: The blackleg pathogen, Dickeya dianthicola, can infect daughter tubers and go relatively unnoticed in seed pieces until cutting. (Photo courtesy of Clay Pederson)

Figure 5: An example of bacterial soft rot in a potato tuber on the left and the physiological disorder internal heat necrosis on the right with some bruising also present on the edge.

Figure 5: An example of bacterial soft rot in a potato tuber on the left and the physiological disorder internal heat necrosis on the right with some bruising also present on the edge.

No matter what we do for seed management, there will always be some disease or pest issue that will go unnoticed. The goal of any seed monitoring program is not to eliminate an issue but rather keep it at a level that minimizes yield losses and pathogen spread. Seed monitoring is only one step in an integrated management program. Other integrated management techniques (e.g. seed treatments and in-season disease monitoring) are still need to produce a quality crop.

For more information on potato production, use the following link for Chapter 13 of the Florida Vegetable Production Guide:

Chapter 13. Potato Production

 

PG

Author: Nick Dufault – nsdufault@ufl.edu

Extension Plant Pathologist for Vegetable and Row Crops
https://www.facebook.com/pages/Field-Veg-Plant-Pathology-Lab-at-UF/510711278961763?sk=timeline

Nick Dufault

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/10/22/potato-disease-management-starts-with-monitoring-your-seed-stock/

Tropical Weather will Increase Disease Pressure on Late Planted Crops

Figure 1. Video of weather forecast for Friday September 2 showing movement through the Southeast of Hurricane Hermine. There is a brief advertisement at the beginning of the video.

Ian Small, Nicholas Dufault, Kelly O’Brien, and David Wright

Late season storms like hurricane Hermine (Fig. 1) and tropical depression Julia (and 12) often bring significant wind and rainfall to our region (Fig. 2). It is important to keep in mind the impacts this weather can have on your crops. While many row crops are already mature and in the process of being harvested, there might be some late planted crops, such as double crop soybeans and June-planted peanuts, that are susceptible to disease. So, what impact does the weather associated with Hermine and other tropical systems have on row crop growers? It means that the environment has become more conducive for disease, but more specifically, that:

  • A combination of high moisture and wind speeds creates an environment optimal for fungal (e.g. soybean rust, Cercospora leaf blight, and frog eye leaf spot), oomycete (e.g. downy mildew), and bacterial pathogens (e.g. bacterial blight) to grow, infect, and spread.
  • Weather systems like Hermine spread pathogens over short and long distances very effectively. Rain splash as well as wind-blown rainfall are efficient means for local dispersal of spores and bacteria in a field, but these factors are also critical to the release of spores into the atmosphere for long distance movement to fields miles away.
  • Too much rain creates problems for growers by limiting access to fields for fungicide sprays and other management practices.
Figure 2. Precipitation (inches) recorded for two weeks after hurricane Hermine.

Figure 2. Precipitation (inches) recorded for two weeks after hurricane Hermine.

The role that hurricanes can play in spreading pathogens has been demonstrated by soybean rust, which was introduced into the continental US by hurricane Ivan in 2004. Since 2005, a network of soybean sentinel plots has been used to monitor the spread of soybean rust (www.sbrusa.net). In 2016, leading up to hurricane Hermine, several sentinel plots across Florida (14 out of 21 scouted counties by May 31) were found to be positive for soybean rust early in the season.  By the end of August, 25 out of 27 scouted counties were positive,  well ahead of previous years.

Figure 3. Status of positive soybean rust reports (red color) on May 31 and August 31.

Figure 3. Status of positive soybean rust reports (red color) on May 31 and August 31.

The large number of positive counties with soybean rust was likely due to the mild winter conditions that enabled the pathogen to overwinter more easily. The combination of above average (positive) soybean rust reports in Florida, and weather from Hurricane Hermine suggests that it is highly likely that the moisture and wind conditions were favorable for the spread of soybean rust spores along the path of Hermine (Fig. 4). With approaching cool autumn temperatures, the rust will spread even more, but by then, it will no longer be a threat to soybean production.

Figure 4. Force wind swaths caused by hurricane Hermine.

Figure 4. Force wind swaths caused by hurricane Hermine.

A question many of you are probably asking is, what can one do about the issues hurricanes and tropical weather systems cause? There is no simple answer to this question, but the first thing would be to assess your risk for disease. Your risk will depend on a number of factors including your crop growth stage, choice of cultivar, presence of pathogens on your farm (or in your region) and fungicide management program. Understanding your risk is an important step to deciding how to respond to environmental events like hurricane Hermine. It is important to scout your fields for disease at repeated intervals, because disease symptoms are only likely to show up 7 to 14 days after a weather event such as Hermine. The book A Farmer’s Guide to Soybean Diseases from the American Phytopathological Society provides some good information on how to identify and manage many soybean diseases.

Ultimately, each situation will be unique and nothing makes up for experience when dealing with diseases. Contact your local Extension Agents and consultants to find out what diseases are present in your region, as well as the management options that are available.

Links to online publications with more information on this topic:

Soybean Production in Florida

NC State IPM Soybean Disease Management

Fungicide Efficacy for Control of Foliar Soybean Diseases

 

PG

Author: Nick Dufault – nsdufault@ufl.edu

Extension Plant Pathologist for Vegetable and Row Crops
https://www.facebook.com/pages/Field-Veg-Plant-Pathology-Lab-at-UF/510711278961763?sk=timeline

Nick Dufault

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/09/17/tropical-weather-will-increase-disease-pressure-on-late-planted-crops/

Ergot: A Fungal Disease in Argentine Bahiagrass Found in Jackson County

Ergot: A Fungal Disease in Argentine Bahiagrass Found in Jackson County

Ergot infected Argentine on the left and normal seadhead on the right

Ergot infected Argentine bahiagrass seedheads on the left and center,  normal seedhead on the right.  Photo credit:  Doug Mayo

Several calls have come in to the Jackson County Extension Office recently from producers regarding something unusual in their “Argentine” bahiagrass fields.  A parasitic fungal disease called ergot (Claviceps paspali) is growing on the seedheads (racemes) of Argentine bahiagrass, in fields that have been allowed to reach maturity for seed production or delayed hay harvest.  The weather conditions lately have certainly been favorable for fungal disease:  cloudy days, high humidity, and frequent rainfall.  If you have Argentine bahiagrass pastures, you should be familiar with the symptoms of this fungal disease, so you can monitor it and manage accordingly.  There are two major concerns with ergot:  1) ergot spores contain a toxin that affects livestock and 2) ergot decreases seed production. The fungus actually prevents flower fertilization and seed formation, so the main issue for seed producers is just a mild to serious loss in overall yield.  Ergot toxicity from bahiagrass is very rare, but could become an issue under the right conditions.

Ergot Identification

Argentine bahiagrass is much more commonly infected with ergot than the “Pensacola” cultivars (Tifton-9, TifQuik, UF Riata).  The “Pensacola” cultivars on the other hand are more susceptible to dollar spot (Sclerotinia homoeocarpa), which is a fungal disease of the leaf tissue.  Ergot spores are spread by wind, insects, or animal movement.  The fungus first infects the bahiagrass flowers and then grows in place of the seed.

Ergot frequently infects grasses in the genus Paspalum (bahiagrass) in the southern United States. The infection cycle begins with sexual spores (ascospores) spread by wind or possibly insects. The fungus infects the pistil of the flower at the time of flowering by colonizing the styles of susceptible plants, and a few days later the content of the ovary is replaced by fungal tissue.  The sign of ergot infection appears at flowering (anthesis) when a sugar-rich honeydew (exudate) is produced on infected flowers (florets). The honeydew makes seed heads feel sticky, and the exudates contain the asexual spores (conidia) that are responsible for initiating secondary infections (Fig. 1 A and B). Disease development is correlated to environmental conditions of high humidity, cloudy days, and warm temperatures, after which the disease cycle ends by forming a mass of dark fungal tissue (sclerotium) that replaces the seed and forces the glumes apart (Fig. 1 C and D). Additionally, ergot-infected seed contains alkaloids that are poisonous to animals.  Ergot Resistant Tetraploid Bahiagrass and Fungicide Effects on Seed Yield and Quality
FIGURE 1 Ergot (Claviceps paspali Stevens and Hall) in ‘Argentine’ bahiagrass: (A) early stage of honeydew development at anthesis; (B) dried honeydew in approximate 40% of the seed head and saprophytic fungi growing in a seed head postanthesis; (C) seed head at the time of harvest with three florets whose seed was replaced by ergot (note how the fungal tissue forced the glumes apart) while the other florets were not affected by the fungus; (D) normal caryopsis fully developed, right, and caryopsis replaced by ergot, left. Source: Ergot Resistant Tetraploid Bahiagrass and Fungicide Effects on Seed Yield and Quality

FIGURE 1 Ergot (Claviceps paspali ) in ‘Argentine’ bahiagrass: (A) early stage of honeydew development at anthesis; (B) dried honeydew in approximately 40% of the seed head and saprophytic fungi growing in a seed head postanthesis; (C) seed head at the time of harvest with three florets whose seed was replaced by ergot (note how the fungal tissue forced the glumes apart) while the other florets were not affected by the fungus; (D) normal caryopsis fully developed, right, and caryopsis replaced by ergot, left. Source: Ergot Resistant Tetraploid Bahiagrass and Fungicide Effects on Seed Yield and Quality

Toxicity

Ergot toxicity is not a common issue with grazing livestock, but is something worth monitoring in Argentine bahiagrass fields, at this time of year.  The fungus only affects the seedheads, so the rest of the plant is nontoxic.  With normal, rotational or continuous grazing, the percentage of mature seedheads in a given pasture is fairly limited.  The greatest concern is turning livestock in to graze a pasture with a high percentage of mature seedheads in mid to late summer.  This might be an issue in a field where seed production or hay production was abandoned and instead utilized for grazing. Or perhaps a pasture that has not been utilized for several weeks, that has become more mature than normal in a rotational grazing system.

The key to livestock poisoning is the amount of toxic spores that are consumed.  The old adage, “The solution to pollution is dilution” is certainly true with livestock. The key is to avoid long, continuous exposure, or feeding toxins in a high percentage of the diet.

Intake of ergot bodies should be <0.1% of the total diet, and concentrations of ergot alkaloids should be <100 ppm in the total diet. Ergotism can be controlled by an immediate change to an ergot-free diet.  Merck Vet Manual

The NRCS Bahiagrass fact sheet contains the following statement:

Caution: Seed heads of the cultivar ‘Argentine’ are often infected by ergot (Claviceps paspali). Pregnant mares can experience abortion problems, if they eat large quantities of infected seed heads. Also, ingestion of infected seeds can produce toxic effects in cattle. USDA NRCS – Plant Materials Center

There are different forms of ergot, depending on the crop, season and location.  According to Ergot as a Plant Disease, the form of ergot (Claviceps paspali) found in bahiagrass and dallisgrass affects the nervous system. The common name for animals affected is “Bahiagrass Staggers” or “Dallisgrass Staggers.”  The ergot that occurs in cool-seson forages or crops such as rye or wheat, and ryegrass (Claviceps purpurea) causes lameness, hoof and tail decay, and even gangrene.  Ergot toxicity can also affect milk production and abortions in pregnant animals.

Animals consume ergot by eating the spores (sclerotia) present in contaminated feed. All domestic animals are susceptible, including birds. Cattle seem to be the most susceptible. The responses of animals consuming ergot are usually quite variable and are dependent on variations in alkaloid content, frequency of ingesting ergot, quantity of ergot ingested, climatic conditions under which ergot grew, the species of ergot involved, and the influence of other impurities in the feed such as histamine and acetylcholine.  Two well-known forms of ergotism exist in animals, an acute form characterized by convulsions, and a chronic form characterized by gangrene. A third form of ergotism is characterized by hyperthermia (increased body temperature) in cattle, and a fourth form is characterized by agalactia (no milk) and lack of mammary gland development, prolonged gestations, and early foal deaths in mares fed heavily contaminated feed. Which form of ergotism is manifested depends on the type of ergot consumed and the ratio of major toxic alkaloids present in the ergot: ergotamine, ergotoxine,and ergometrine. Claviceps purpurea, the common cause of ergot in North Dakota, is usually associated with gangrenous ergotism. Claviceps paspali, an ergot of Paspalum species of plants (bahiagrass & dallisgrass), is most commonly associated with central nervous derangement.  The responses of animals consuming ergot are usually quite variable and are dependent on variations in alkaloid content, frequency of ingesting ergot, quantity of ergot ingested, climatic conditions under which ergot grew, the species of ergot involved, and the influence of other impurities in the feed such as histamine and acetylcholine.  Ergot as a Plant Disease

Symptoms of Bahiagrass Staggers

The same ergot fungus (Claviceps paspali) that affects Argentine bahiagrass also effects dallisgrass, that is more common in other parts of the South.  The following is a description of the symptoms of egrot toxicity from the same fungus that also affects Argentine Bahiagrass.

Clinical signs of Dallisgrass Staggers involve the animal’s nervous system. In the very early stages of the disease, the only sign seen may be trembling of various muscles after exercise. As the disease progresses, muscle tremors worsen so that the animal becomes uncoordinated and may show continuous shaking of the limbs and nodding of the head. When forced to move, this severely affected animal may stagger, walk sideways, and display a “goose-stepping” gait. Incoordination can be severe enough that the animal will fall down when attempting to walk. Some animals may be found down and unable to stand. Diarrhea may also be noted in some affected animals. Death can occur in severe cases, especially in scenarios where cattle are naïve to grazing dallisgrass. There is no cure for ergot poisoning, but removing cows from infected pastures when symptoms are first noticed usually results in uneventful recovery in three to five days. Mowing seedheads to prevent animals from grazing them helps prevent the problem from occurring. Ergot toxicity from dallisgrass hay is very uncommon since the total intake of hay forage dilutes any ergot contained in the hay. Ergot Poisoning and Dallisgrass Staggers

Management of Ergot in Bahia

The intent of this article was not to scare livestock producers, but simply to make them aware of a potentially serious issue. Before turning cattle or other livestock into an Argentine bahiagrass pasture with mature seedheads, it is a good idea to scout the field for the severity of this disease. Once a serious level, >20% of the pasture becomes infected, it would be better to be cautious, mow the seedheads off and wait a few weeks before grazing.  Pregnant animals, particularity mares should be moved to an alternate location, and even stalled if need be, until the severity of the infection in a pasture is reduced. Once the fungal materials are mowed off and the seedheads decay, there is always potential for reinfection, based on the right environmental conditions returning (heavy, continuous rainfall, humidity and mature seedheads).
Most of the cases of livestock fatalities and abortions involved contaminated feeds or bedding straw that were consumed on a regular basis, at fairly high levels.  Ergot toxicity from livestock grazing bahiagrass is not a common occurrence, but conditions at this point in the summer are ideal for the development of this disease, so it is something to keep an eye on.  If you do have animals grazing Argentine bahiagrass, and they seem to be acting strange, have muscle tremors, lack coordination, or are disoriented, the first course of action would be to move livestock to a new pasture immediately to change their diet,  monitor their behavior, and advise your veterinarian of the situation.  If conditions don’t rapidly improve, consult with your veterinarian.  There are other diseases that can cause similar symptoms that may require very different treatment.

Information sources used for this article:

Ergot Resistant Tetraploid Bahiagrass and Fungicide Effects on Seed Yield and Quality – Rios, E., Blount, A., Harmon, P., Mackowiak, C., Kenworthy, K., and Quesenberry, K. 2015. Plant Health Progress doi:10.1094/PHP-RS-14-0051.

Ergot as a Plant Disease – NDSU – Marcia McMullen, Extension Plant Pathologist & Charles Stoltenow, Extension Veterinarian

Ergot Poisoning and Dallisgrass Staggers – Dr. John Jennings, Extension Forage Specialist – University of Arkansas

Bahiagrass Plant Fact Sheet – Houck, M., 2009. USDA-Natural Resources Conservation Service, Louisiana

Ergotism – Merck Veterinary Manual

 

PG

Author: Doug Mayo – demayo@ufl.edu

Lead Editor for Panhandle Ag e-news – Jackson County Extension Director – Livestock & Forages Agent. My true expertise is with beef cattle and pasture management, but I can assist with information on other livestock species, as well as recreational fish ponds.
http://jackson.ifas.ufl.edu

Doug Mayo

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/08/13/ergot-a-fungal-disease-in-argentine-bahiagrass-found-in-jackson-county/

Boxwood Blight Update: Disease Confirmed in Leon County

Close up of Boxwood Blight symptoms from the pyramid boxwood to the right. Note the dark discoloration of the leaves. Stems presented same dark discoloration. Also note leaf drop on the soil inside the pot. Photo credit: Fanny Iriate

Close up of Boxwood Blight symptoms from the pyramid boxwood to the right. Note the dark discoloration of the leaves. Stems presented same dark discoloration. Also note leaf drop on the soil inside the pot. Photo credit: Fanny Iriate

Fanny Iriarte, Mathews Paret, and Gary Knox, University of Florida, North Florida Research and Education Center, Quincy

In April 2015, Boxwood Blight was confirmed in Florida in a commercial nursery in North Florida (Pest Alert: Boxwood Blight)  In February 2016, the disease was confirmed in the Florida Panhandle at a nursery and in a residential landscape in Leon County.

  • The Boxwood blight pathogen has been confirmed by the University of Florida NFREC Plant Diagnostic Clinic and the Division of Plant Industry, FDACS in a residential landscape in Tallahassee (early February 2016). In this case, a pyramid boxwood showing symptoms (photo above) had been purchased from a nursery in Georgia; in turn, the Georgia nursery had purchased the plant from Oregon. The plant was asymptomatic at the time of purchase and transport to Tallahassee. The pathogen started causing symptoms of disease in early January when environmental conditions were conducive for disease development (cool and wet).
  • A second finding of the disease was confirmed by Division of Plant Industry at a local nursery in Leon county (late February 2016). In this case, the plants came from Mississippi.
  • DPI, the property owner in the first case, and the nursery personnel in the second case are currently implementing strategies to eradicate the disease from the locations to avoid any further spread.

Recommendations for landscapers

  • Inspect boxwoods on your property for leaf spots and blight symptoms.
  • Keep in mind that besides infected plant material and plant debris, fungal spores can also be moved by water, wind, shoes, tires, clothing or animal fur. Disease can be also spread by pruning tools, shovels, hoses or any other landscape equipment from infected to healthy plants in the same property or to other properties.
  • Train employees and clients on how to identify Boxwood blight and how to avoid disease spread.
  • Whenever possible, purchase plants from nurseries that have a Boxwood Blight Compliance Agreement through their State Department of Agriculture (e.g.: Georgia Department of Agriculture).
  • Disinfect pruners, other tools, or shoes within and between different blocks of plants within the same landscape and specially when moving to other landscapes. Good products are Lysol Concentrate Disinfectant (2.5 Tbsp/gallon of water) or a 10 % bleach solution.
  • Submit samples for confirmation of disease:  PLANT DISEASE DIAGNOSTIC LAB SAMPLE SUBMISSION FORM

For more information on Boxwood Blight:

Pest Alert: Boxwood Blight (original Panhandle Ag News Article)
Nursery Industry Voluntary Best Management Practices for Boxwood Blight
www.boxwoodblight.org
North Carolina State Ornamental Plant Pathology

 

PG

Author: Mathews Paret – paret@ufl.edu


http://nfrec.ifas.ufl.edu

Mathews Paret

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/04/01/boxwood-blight-update-disease-confirmed-in-leon-county/

Cucurbit Disease Management in an El Niño Year

Cucurbit Disease Management in an El Niño Year

So far, mild winter temperatures and ample rainfall have led to multiple disease issues in many of northern Florida’s winter crops (e.g. forages). While temperatures are predicted to be below normal for the months February, March and April, it is projected that rainfall will continue to be above average during that same period (Figure 1). Recent frosts in north and central Florida could help with the management of various plant pathogens, however, it is still likely significant levels of inoculum will be present this spring related to these winter weather trends. Thus, now is a good time to start preparing disease management strategies for spring cucurbits and other vegetable crops.

Fig. 1: The 90 day (February, March and April) seasonal weather outlook for temperature and weather probabilities in the United States provided by the National Oceanic and Atmospheric Administration (NOAA). Figures were copied from the Agroclimate website (http://agroclimate.org/forecasts/Seasonal-Forecast/, accessed on 1/28/2016)

Figure 1: The 90 day (February, March and April) seasonal weather outlook for temperature and weather probabilities in the United States provided by the National Oceanic and Atmospheric Administration (NOAA). Figures were copied from the Agroclimate website (http://agroclimate.org/forecasts/Seasonal-Forecast/, accessed on 1/28/2016)

In general, the development of a quality disease management strategy starts by assessing the risk for diseases at each field site. This assessment should begin by examining the crop and field history of the site in relation to disease. Some general questions to consider are:

  • Was disease present last season, and if so, which one?
  • What variety will be planted and what are its disease traits?
  • What is the estimated planting date and how might that affect disease?
  • What was the crop rotation for the previous 3 years and how will that affect disease?

Answers to these questions will provide key insights about pre-plant disease risk. If the answers to one or more of these questions favor disease development, then options such as using a less susceptible variety or adjusting the planting date can be implemented to help reduce the risk level. This information can also be used to create and customize a chemical management program based on the identified disease issues. Further information about various chemicals available for cucurbits and types of programs available for watermelons can be found at the U-Scout website as well as in the Vegetable Production Handbook of Florida.

Assessing pre-plant disease is important for any integrated management strategy, however, in-season disease risks are just as important. The four main components of an in-season disease management strategy are prevention, monitoring, accurate diagnosis, and selection of optimal management tools. For example, monitoring cucurbit transplants and removing diseased seedlings will help prevent pathogen introductions especially for the diseases gummy stem blight and bacterial fruit blotch. Fungicides can also provide quality disease control and save yields, however, their effectiveness can vary depending on the pathogen present and the number of times products can be sprayed. Thus, once a disease is accurately diagnosed within a field, it is critical to adjust the chemical management plan appropriately. These adjustments can be made through consulting the resources listed below and/or by contacting local extension personnel for assistance.

Proper assessment of risk and planning for disease management will provide most of the tools needed for mitigating a disease’s impacts on yields. However, even with proper management, diseases can still be a problem (Figure 2), and weather also plays a major role in a disease’s impact. Thus, continued monitoring of the crops throughout the season as well as contacting extension and consulting specialists with questions about disease management strategies will be needed to maintain and/or modify in-season management programs.

Fig. 2: An example of disease presence in 3 different fungicide programs using products for gummy stem blight management. Applications were made on a regular schedule in all plots. Check treatments did not have any fungicide products applied to them.

Figure 2: An example of disease presence in 3 different fungicide programs using products for gummy stem blight management. Applications were made on a regular schedule in all plots. Check treatments did not have any fungicide products applied to them.

The prediction for increased rainfall this spring means that there is a good chance diseases will be an important concern in 2016 cucurbit production systems. Assessing the disease risk and developing a quality management program now will go a long way to saving time and money later in the season.

More information on cucurbit disease management can be found at:

 

PG

Author: Nick Dufault – nsdufault@ufl.edu

Extension Plant Pathologist for Vegetable and Row Crops
https://www.facebook.com/pages/Field-Veg-Plant-Pathology-Lab-at-UF/510711278961763?sk=timeline

Nick Dufault

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/01/29/cucurbit-disease-management-in-an-el-nino-year/

Dormant Sprays Useful for Insect and Disease Management in Fruits and Ornamentals

Dormant Sprays Useful for Insect and Disease Management in Fruits and Ornamentals

Crapemyrtle Scale, UF IFAS Extension

Crapemyrtle Scale, UF / IFAS Extension

During cold January weather, one doesn’t often think about spraying fruit trees and ornamental shrubs for spring insects and diseases. It’s just not on the radar. The fact is January and February are the best time to apply dormant sprays to combat insect and disease issues. Many ask, “What are dormant sprays” ?

Dormant sprays act on insects or disease pathogens differently. Many insects overwinter on trees and shrubs, either as eggs or immobilized in a protective shell (scale insects).  Horticultural oils applied during cool dormant conditions work by smothering the eggs of some insect species or encapsulated scale insects. Since they cannot breathe, they die.

On the other hand, dormant sprays containing copper or sulfur actually kill latent fungal spores that are ready to infect the moment weather warms. They also burn tender young plant tissue, so can only be used when the plant is not actively growing. These preventative sprays can delay disease incidence in early spring and allow for reduction or elimination of regular fungicide applications. The old adage “an ounce of prevention is worth a pound of cure” surely applies to these situations.

There are several products on the market for dormant applications.

Dormant oil is a type of horticultural oil, made of refined petroleum products, for application on trees or shrubs when the trees are not actively growing. It has been in use for over 100 years. They are effective in the suppression of scale insects and mites. Care must be used to not apply them when daytime temperatures are above 75 degrees or night temperatures below 28 degrees. Other horticultural oils exist that can be applied during the growing season to control soft-bodied insects, but not during extremely hot weather. Many different brands exist, some are certified organic by OMRI. They can be purchased at most garden centers, but the best selection is usually found at your independent nursery or farm store.

SONY DSC

Cottony Cushion Scale, Image Credit, Matthew Orwat, UF / IFAS Extension

Dormant fungicides can be classified into two groups. Those that contain copper and those that contain sulfur. The most common preventative remedy for fungal disease is lime-sulfur. It is applied to dormant plants and actually sanitizes the stem, killing all fungal spores. It cannot be used during the growing season since it burns leafy tissue. Caution must be taken when mixing and loading since, being an acidic product, can burn the skin. Wear chemical resistant gloves when applying (bought at your local hardware store for $ 4.00-$ 10.00), safety goggles and follow all label directions carefully. Also, never apply lime-sulfur within one month of horticultural oil applications. It should be applied in early to mid February, avoiding hard freezes for the 24 hours around application time.

Dormant copper sprays are effective on both bacterial and fungal pathogens and used primarily on fruit crops for the suppression of many fruit diseases including fire blight, bacterial leaf spot, powdery mildew, downey mildew and anthracnose. One popular option, the “Bordeaux Mixture” blends copper with lime. This lime reduces the acidic nature of the copper, thus reducing tissue damage when applied to plants. Always read the label for proper personal protective equipment and dosage rates, to avoid copper toxicity.

For more information, contact your local extension agent or consult these extension publications from: Disease Management Strategies, and Pest Control Using Horticultural Oils .

 

PG

Author: Matthew Orwat – mjorwat@ufl.edu

Matthew J. Orwat started his career with UF / IFAS in 2011 and is the Horticulture Extension Agent for Washington County Florida. His goal is to provide educational programming to meet the diverse needs of and provide solutions for homeowners and small farmers with ornamental, turf, fruit and vegetable gardening objectives. Please feel free to contact him with any questions you may have.
http://washington.ifas.ufl.edu/lng/about/

Matthew Orwat

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2016/01/14/dormant-sprays-useful-for-insect-and-disease-management-in-fruits-and-ornamentals/

Bacterial Gall: A Detrimental Disease of Loropetalum

Bacterial Gall:  A Detrimental Disease of Loropetalum

Warm and wet weather in the Florida Panhandle presents the optimum conditions for the development of bacterial gall on loropetalums.  Shoot dieback is usually the first and most noticeable symptom of the disease.  The dieback can be followed down the branch to dark colored, warty galls that vary in size.  The galls enlarge and eventually encircle the branch resulting in branch or plant death.  Olive, oleander, and ligustrum are also hosts for the bacteria that causes the galls, Pseudomonas savastanoi.

Plant Dieback

Dieback symptoms on loropetalum leaf from bacterial gall. Photo Credit: Matt Lollar, University of Florida/IFAS

Bacterial Gall

Bacterial gall on loropetalum. Photo Credit: Matt Lollar, University of Florida/IFAS

 

 

The most common source of bacterial gall is from the plant nursery.  Prior to purchase, inspect plants for galls near the soil line.  If plants have already been installed in the landscape, remove any branches containing galls.  Pruning cuts should be made several inches below the gall.  After each cut, dip pruners in a 10% bleach solution or spray with isopropyl alcohol to avoid spreading the disease to other parts of the plant or other plants.  Prune during dry weather.

The best control for bacterial gall is selecting good quality plant material.  For more information on this disease, please visit:  Bacterial Gall on Loropetalum.  More information on disease issues in the home landscape can be found at:  Lawn and Garden Plant Diseases.

PG

Author: Matt Lollar – mlollar@ufl.edu

Matt Lollar is the Jackson County Horticulture Agent. He has 5 years of experience with University of Florida/IFAS Extension and he began his career in Sanford, FL as the Seminole County Horticulture Agent. Matt is originally from Belle Fontaine, AL. He earned his MS and BS degrees in Horticulture Production from Auburn University.

Matt Lollar

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2015/10/20/bacterial-gall-a-detrimental-disease-of-loropetalum/

Vegetable Garden Insect and Disease Management

Vegetable Garden Insect and Disease Management

IMG_0603During this growing season, monitor your plants to keep them healthy. Healthy plants will be able to survive pest attacks better.

Nematodes are microscopic worms that attack vegetable roots and reduce growth and yield. Nematode populations can be reduced temporarily by soil solarization. It is a technique which uses the sun’s heat to kill the soil-borne pests. Also, adding organic matter to the soil will help reduce nematode populations. The organic matter will also improve water holding capacity and increase nutrient content.

If you choose to use pesticides, please follow pesticide label directions carefully. Learn to properly identify garden pests and use synthetic chemicals only when a serious pest problem exists, or a history of a particular problem exists at your site. Organic gardeners can use certain products like BT (Dipel) to control pest. Please remember not every product is for use on every crop, so be sure the target crop is listed on the label before purchasing the product. Follow label directions for measuring, mixing and pay attention to any pre-harvest interval warning. The pre-harvest interval is the time that must elapse between application of the pesticide and harvest. For example, broccoli sprayed with carbaryl (Sevin) should not be harvested for two weeks after application.

 

Pesticide application techniques:

  • Spray the plant thoroughly, covering both the upper and lower leaf surfaces.
  • Do not apply pesticides on windy days.
  • Follow all safety precautions on the label, keep others and pets out of the area until sprays have dried.
  • Apply insecticides late in the afternoon or in the early evening when bees and other pollinators are less active.
  • To reduce spray burn, make sure the plants are not under moisture stress.
  • Water if necessary and let leaves dry before spraying.
  • Avoid using soaps and oils when the weather is very hot, because this can cause leaf burn.
  • Control slugs with products containing iron phosphate.

Many common diseases can be controlled with sprays like chlorothalonil, maneb, or mancozeb fungicide. Powdery mildews can be controlled with triadimefon, myclobutanil, sulfur, or horticultural oils. Rust can be controlled with sulfur, propiconazole, ortebuconazole. Sprays are generally more effective than dusts.

If you have questions please call your UF/IFAS county extension office. We can provide helpful information about insect and disease identification.

 

PG

Author: Eddie Powell – pep5@ufl.edu

Residential Horticulture Educate the residents of Walton County who are unfamiliar with growing certain landscape and vegetable plants that grow in north Florida. Provide homeowners with information about why a good looking healthy lawn is important. Teaching proper fertilization and irrigation practices for successful backyard gardening and container gardening. Master Gardener Coordinator Develop in-school programs with use of Master Gardeners to reach school kids and youth. Also provide educational programs for developing community gardens and provide educational material at local festivals.
http://walton.ifas.ufl.edu

Eddie Powell

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2015/06/11/vegetable-garden-insect-and-disease-management/

Older posts «