Pestalotiopsis (Pestalotia) Diseases of Palm
November 12, 2009 by Brian Brown
Filed under Plant Problems
Summary
- Pestalotiopsis is a fungus that causes diseases of both the palm leaf petiole and leaf blade, often at the same time. Palm leaf diseases caused by Pestalotia are the same as those caused by Pestalotiopsis.
- Many palms are hosts to these fungi. However, the disease is often observed in Florida on Phoenix roebelenii (pygmy date palm), where it can cause a fatal bud rot.
- Leaf spots will begin as very small, yellow, brown or black spots that enlarge in size. The spot usually turns gray with a black outline. Lesions on the petiole and rachis are similar.
- Symptoms may occur on multiple leaves at once, especially on juvenile palms.
- Sanitation and water management are critical for disease management, especially in a nursery (both container and field). Injury prevention and good palm nutrition are part of the overall management strategy.
- Fungicides may be useful as part of an integrated management program, but they should never be the sole component of a program.
Introduction
The fungus Pestalotiopsis causes leaf spots, petiole/rachis blights and sometimes a bud rot of palms. In other words, unlike the other leaf spot and petiole blight pathogens, which attack either the leaf blade or the leaf petiole, Pestalotiopsis attacks all parts of the leaf from base to tip. It is also one of the more ubiquitous fungi in the palm canopy, and is easily isolated from healthy palm tissue.
For information on other leaf spots and petiole/rachis blights, refer to the following documents: Leaf Spots and Leaf Blights of Palm at htttp://edis.ifas.ufl.edu/pp142; and Petiole/Rachis Blight of Palm at http://edis.ifas.ufl.edu/pp145.
Pathogen and Hosts
Pestalotiopsis palmara is the primary, but not the only, Pestalotiopsis species associated with palms. References in the literature to Pestalotia are probably the same disease, as it is difficult to distinguish between these two genera of fungi.
As indicated previously, Pestalotiopsis can be readily isolated from healthy palm tissue. The fungus is not host specific, and has been isolated from a wide variety of palms.
It has been demonstrated that the fungus usually requires wounds for the plant penetration (infection) necessary for disease development. It is not uncommon to isolate Pestalotiopsis and another pathogen from the same diseased tissue. In most cases, it is likely the other pathogen was the primary pathogen (the fungus that invaded the healthy plant tissue first), and Pestalotiopsis invaded via the wound created by the primary pathogen. In Elaeis guineensis (African oil palm), it is well-documented that insect damage is necessary for disease development.
Symptoms
Disease development by Pestalotiopsis can be restricted to only the leaf blade (leaflets or leaf segments) or only the petiole and rachis; or, it can develop on both tissues at the same time (Figure 1). Spots will begin as very small yellow, brown or black spots. If the disease is restricted, the spots may never be more than 1/4 inch in size. Under optimum environmental conditions, the spots may expand and increase in number until they merge (coalesce) to form a leaf blight or rachis blight (larger area of affected tissue) (Figure 2). Often, the spots turn a grayish color that are outlined in black. The same type of lesions occurs on the petiole or rachis of the palm. One may even see lesions occur on leaf spines.
Figure 1. Expanding spots on both leaflets and rachis of Pseudophoenix sargentii caused by Pestalotiopsis.
Figure 2. Petiole lesion on Phoenix roebelenii due to Pestalotiopsis.
If the pathogen is restricted to only causing leaf spots, the disease may not be very damaging to the palm, especially a mature palm in the landscape. However, with juvenile palms that have no trunk and only a few leaves, the palm could be severely affected by the leaf spots.
If the pathogen is causing a rachis or petiole blight, the disease is a more serious problem for two reasons. First, as the pathogen destroys tissue in the rachis or petiole, it will affect the vascular tissue which in turn affects tissue in the leaflets or leaf segments. Second, if the pathogen has infected the spear leaf or other younger leaves, it may spread down the rachis or petiole to the apical meristem (bud) region and affect the growing point of the palm.
While all palms are probably susceptible to diseases caused by this fungus, pgymy date palm (Phoenix roebelenii) appears to be affected quite often in Florida, especially during the winter months. With these palms, a bud rot has been observed that can kill the palm (Figure 3). This has been observed on juvenile and mature palms.
Figure 3. Note dark lesions caused by Pestalotiopsis on petioles of this Phoenix roebelenii, especially at base of young leaves emerging from bud.
Diagnosis
The exact diagnosis of Pestalotiopsis diseases is based on identification of the fungal pathogen. The pathogen is identified by examining the fungal spores. These may be examined directly on the plant tissue if spores are being produced, or by placing the diseased tissue in a moist chamber to induce sporulation. Isolation of the pathogen can be made on artificial media, and this growth then induced to sporulate.
It is not uncommon to observe or isolate more than one potential pathogen from the same diseased tissue. In some cases, it is apparent which fungus was the first pathogen to invade the healthy tissue, while the second fungus moved into the resulting necrotic (dead) tissue as a saprobe.
The Florida Extension Plant Disease Clinic (FEPDC) network is available for pathogen identification. Contact your local county Extension office or FEPDC for details on sample submission and cost of a laboratory diagnosis.
Disease Management
Pestalotiopsis produces abundant spores that can be easily dispersed by wind and water movement (splashing from rain or irrigation), so sanitation and water management are critical. Wounds or plant damage often seems to be a prerequisite for disease development, either naturally or from insects, other pathogens, nutrient deficiencies or human activity.
Water management requires limiting the length of time when the leaves are wet or exposed to high humidity levels. This includes elimination of overhead irrigation or irrigating in the early morning hours when dew is already present. Leaf wetness can also be decreased by increasing air circulation and increasing plant spacing.
In a nursery situation, severely diseased leaves should be pruned and destroyed to reduce spores available to infect healthy tissue. If the palm is small with only a few leaves, eliminate the palm completely.
In the landscape or field nursery where nutrient deficiencies are often problematic, pruning diseased leaves may make the deficiency worse. Thus, one needs to decide which is or will debilitate the palm most – the disease or the nutrient deficiency. In many situations, the nutrient deficiency causes chlorosis (yellow) and necrosis (death) of the leaf tissue, creating the wound necessary for Pestalotiopsis infection. By eliminating the deficiency symptoms, one prevents disease development also. Thus, proper nutrient management is critical for disease prevention and management.
While fungicides may be useful to prevent further spread of the disease, they are merely a supplement to water management, sanitation, injury prevention and good palm nutrition. Fungicides alone will not solve the problem. It is critical to understand that fungicides do not cure the leaf spot or petiole blight already present. Once a leaf spot or petiole lesion occurs, it will remain for the duration of the life of that leaf. Fungicides are used to prevent further spread of the disease by protecting leaf tissue that has not been infected by the fungal pathogen.
In the nursery situation, prune severely diseased leaves prior to fungicide application. These leaves need to be removed anyway, and this will reduce the amount of fungicide used in the process. In the landscape situation, unless the leaf spot disease is severe, leaf pruning is not recommended unless the palm is free of nutrient deficiencies. In general, nutrient deficiencies are far more debilitating to the landscape palm than leaf spot diseases.
Fungicide trials to examine efficacy of these products on palms have not been extensive. Foliar application of broad-spectrum fungicides would be suggested. Examples include, but are not limited to, products with the active ingredients mancozeb or chlorothalonil.
Selected References
Uchida, J. Y. 2004. Pestalotiopsis diseases. Pages 27-28 in: Diseases and Disorders of Ornamental Palms. M. L. Elliott, T. K. Broschat, J. Y. Uchida, and G. W. Simone, eds. American Phytopathological Society, St. Paul, MN.
Footnotes
1.
This document is Fact Sheet PP-217, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date January 2006. Revised January 2009. Visit the EDIS Web site at http://edis.ifas.ufl.edu.
2.
M. L. Elliott, professor, Plant Pathology Department, Fort Lauderdale Research and Education Center–Ft. Lauderdale, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.
Texas Phoenix Palm Decline
October 26, 2009 by Brian Brown
Filed under Plant Problems
Summary
Texas Phoenix palm decline (TPPD) is a new disease in Florida. This disease is caused by an unculturable bacterium that has no cell wall — a phytoplasma.
The TPPD phytoplasma is similar to, but genetically distinct from the phytoplasma that causes lethal yellowing (LY) disease of palms.
Texas Phoenix palm decline is a fatal, systemic disease that kills palms quickly. The TPPD phytoplasma is spread naturally to palms by sap-feeding insects, such as planthoppers.
Palms showing symptoms of more than 25 percent foliar discoloration or a dead spear leaf due to the disease should be removed immediately.
Management of TPPD includes protection of susceptible palms in disease-active areas by
trunk injection with oxytetracycline HCl (OTC) every four months and
planting palm species that are not known to contract this disease.
As of February 2009, palm species known to be most severely affected by TPPD were Phoenix canariensis (Canary Island date palm), Phoenix dactylifera (edible date palm), Phoenix sylvestris (wild date palm) and Sabal palmetto (cabbage palm).
Introduction
Until recently, lethal yellowing (LY) was the only palm disease in Florida caused by a phytoplasma. In late 2006, a second phytoplasma disease was identified in the coastal areas of Central Florida (from Sarasota to Tampa), affecting Phoenix (date) species. In early 2008, this second phytoplasma disease was confirmed as the cause of declining Sabal palmetto (cabbage palm) in Hillsborough and Manatee counties. The disease is known as Texas Phoenix palm decline because it was originally described in the southern coastal region of Texas on Phoenix canariensis (Canary Island date palm).
Pathogen and Hosts
Texas Phoenix palm decline is caused by a phytoplasma, an unculturable bacterium that has no cell wall. Among phytoplasmas, the TPPD agent has been classified as a member of 16S rDNA RFLP group 16SrIV, subgroup D (16SrIV-D). The signature DNA sequence obtained from TPPD phytoplasma in Florida is a perfect match to the signature of the phytoplasma known to cause TPPD on P. canariensis (Canary Island date palm) in the Corpus Christi area of Texas. Analysis of DNA has determined the TPPD phytoplasma is related to, but genetically distinct from the phytoplasma that causes LY.
Phytoplasmas systemically colonize the phloem tissue (vascular tissue transporting photosynthates) of plants. Phytoplasmas are transmitted to plants by piercing-sucking insects that feed on phloem sap. The insects spread the phytoplasma from plant to plant as they visit different hosts during their feeding activities. Phytoplasmas are not known to survive outside their host, whether the host is plant or insect. Planthoppers, treehoppers or psyllids are the most-likely groups of insects to transmit phytoplasmas.
It is not known when the TPPD phytoplasma arrived in Florida, but considerable time would have been necessary for both the pathogen and the vector populations to establish and for TPPD disease incidence to increase to its present level in Florida.
The presence of TPPD phytoplasma has been confirmed in Florida in symptomatic P. canariensis (Canary Island date palm), P. dactylifera (edible date palm) or P. sylvestris (wild date palm) in landscape and field nursery sites in the following counties: Highlands, Lake, Sarasota, Manatee, Pinellas, and Hillsborough, as well as in western portions of Polk County. The TPPD phytoplasma has been most recently detected in Sabal palmetto (cabbage palm) in landscapes and natural areas in Hillsborough, Manatee, Sarastoa, Polk, DeSoto and Hardee counties. However, in 2008 the primary concentration of diseased cabbage palms in Florida was in southern Hillsborough County and in Manatee County.
A map illustrating sites in Florida where the disease has been confirmed can be found on the Florida Division of Plant Industry Web site, http://www.doacs.state.fl.us/pi/caps/TPPD_maps/TPPD.pdf. This map will be periodically updated as new cases of the disease are verified.
How far and how quickly TPPD will spread to other Florida counties is unknown. However, since movement of palms occurs widely in Florida, it is likely people will unknowingly spread the disease by moving vector and infected hosts.
Currently, the known susceptible hosts for the TPPD phytoplasma are P. canariensis, P.dactylifera, P. sylvestris, P. reclinata, Sabal palmetto and Syagrus romanzoffiana (queen palm). Only a few queen palms in only three nursery sites — one each in Hillsborough, Manatee and Pinellas counties — have been confirmed with this disease, whereas the disease has been observed widely among Phoenix species in a five-county area (Sarasota, Manatee, Pinellas, Polk and Hillsborough counties).
Symptoms
The symptoms of this new disease appear to be exactly the same as those associated with LY of Phoenix species, with possibly one exception; root decay has been observed with TPPD.
The first obvious TPPD symptom on mature palms is premature drop of most or all fruits at one time (Figure 1). The fruit drop occurs within a few days. The fruit drop is not spread out over a prolonged period of time. Inflorescence (flower) necrosis (death) follows (Figure 2). However, these two symptoms will only be observed if the palm is mature enough to produce fruit, if it is the season for flowering and fruiting, and if the flowers or fruits have not been trimmed from the palm.
Figure 2. Death of the inflorescence (flowers) is an early symptom of TPPD. This photo also illustrates a dead spear leaf (youngest leaf that has not unfolded), which is tan and not green.
Figure 3. Discoloration of the lowest (oldest) leaves is an early symptom of TPPD.
Figure 4. Discoloration of the lowest (older) leaves is an early symptom of TPPD in cabbage palm.
Figure 5. Discoloration of the leaves begins at the leaf tips.
The next symptom is discoloration of the foliage, beginning with the oldest leaves. The leaves do not turn yellow (or do so briefly), but quickly turn varying shades of reddish-brown to dark brown or gray (figures 3 and 4). The discoloration begins at leaf tips (Figure 5).
Unless the palm is being monitored closely, the onset of leaf discoloration is usually first recognized as a greater number of dead older leaves than is normal for natural senescence. This symptom might be confused with other problems, such as early senescence due to nutrient deficiency (e.g., potassium) or Ganoderma butt rot. However, if the dying or dead leaves are being regularly removed (nobody likes an untidy palm!), even this TPPD symptom of foliage discoloration and death may not be obvious.
Figure 6. Phoenix sylvestris exhibiting symptoms of TPPD. Note more dead lower leaves than normal for a healthy palm. Also, the spear leaf (youngest leaf that has not unfolded) is tan and not green.
In Phoenix species, when less than one-third (and usually less than one-quarter) of the oldest leaves have discolored and become necrotic, the spear leaf dies (Figures 2, 6 and 7). Death of the spear leaf indicates the apical meristem (bud or heart) has died. Once the apical meristem has died, no new leaves will develop, and the remaining leaves will continue to discolor from the oldest to the youngest leaves. In cabbage palms, approximately two-thirds of the oldest leaves will have discolored before the spear leaf dies (Figure 8).
In some instances, by the time the spear leaf dies, mature roots of the palm at or near the soil surface are soft in texture and easily broken. The palm can be easily rocked back and forth in the ground because the root system is decaying. This symptom is not typical for palms affected by LY.
Figure 7. Close-up of dead spear leaf in Figure 6.
Figure 8. Sabal palmetto (cabbage palm), exhibiting symptoms of TPPD. Note more dead lower leaves than is normal for a healthy palm. Also, the spear leaf (youngest leaf) has died and is a tan color, rather than green.
Death of the spear leaf may not always be obvious. Both Phoenix species and cabbage palms have numerous young leaves surrounding the spear leaf. Unless you see the spear leaf is dead (Figure 2 and 6) or find it hanging from the canopy (Figure 9) or on the ground, you will probably need to physically examine the canopy up close to determine whether a healthy spear leaf is present (Figure 10). Also, as the young spear leaf of Phoenix palms — in normal, healthy conditions – is often enclosed in a thin, brown sheath (which tears like paper), be careful not to confuse the normally occurring brown sheath for a dead spear leaf.
Two juvenile queen palms have been diagnosed with the TPPD phytoplasma. Extensive root decay early in disease development was a common symptom to both palms. Leaf necrosis was exhibited on the lowest leaves first and continued upward through the canopy. It is not yet clear at what stage in the disease process the spear leaf dies, but initial observations indicate the spear leaf dies early in the disease process. The TPPD symptoms observed in these juvenile queen palms were distinctly different from Fusarium wilt, another new disease of queen palms. (For information on Fusarium wilt in queen palms, see the following: http://flrec.ifas.ufl.edu/palm_prod/pdfs/New-Disease-Queen-Palms-Mexican-Fan-Palms-July.pdf.)
Figure 9. Note the spear leaf has died and is hanging down from the canopy of this Phoenix sylvestris affected by TPPD.
Figure 10. The spear leaf has already died in this Phoenix sylvestris, and the spear leaf has broken off from the canopy. Unlike the examples shown in figures 6, 7 and 9, without a close examination of the bud on this palm, it would not be apparent that the spear leaf had died.
Diagnostics
Initial diagnosis of TPPD is based on the palm symptoms described above. Since the phytoplasma is not culturable, a molecular diagnostic test is used to confirm the presence of the pathogen. If pathogen confirmation is necessary, contact your local county Extension office — http://solutionsforyourlife.ufl.edu/map — for information on sample submission and cost of laboratory diagnosis. This information is also available on the Web site for the UF/IFAS Fort Lauderdale Research and Education Center — http://flrec.ifas.ufl.edu/pdfs/LY-TPPD-Trunk-Sampling.pdf.
Sampling is accomplished by boring into the trunk. The sampling process requires a drill with a long, large-diameter drill bit. Do not obtain samples without first reviewing the complete set of instructions. The quality of the sample is critical for an accurate diagnosis.
It is currently not known how early in the disease cycle TPPD phytoplasma can be detected via trunk-tissue sampling. However, the TPPD phytoplasma is usually not detectable in palms that are not exhibiting symptoms. This phytoplasma may not be detectable until the spear leaf dies.
Phytoplasma detection by means of testing a trunk tissue sample is like searching blindfolded for a red marble in a bowl that is mostly full of white marbles. If there is only one red marble (phytoplasma) in the bowl of white marbles (trunk tissue), the likelihood of selecting that red marble, if you were blind folded, would be slim. However, the likelihood of selecting a red marble increases as the number of red marbles increase.
The molecular test for the TPPD phytoplasma is best used to confirm the presence of the disease in symptomatic palms in a nursery or community in order to track the spread of the disease and to devise a management program for remaining, susceptible palms. The molecular test does not certify a palm is phytoplasma free.
Remember that palms die or appear to be dying for a number of reasons; Texas Phoenix palm decline is just one reason. Before submitting a sample, take the time to make the best possible field diagnosis.
Disease Management
If the spear leaf has died, the palm should be removed as soon as possible. Death of the spear leaf indicates the apical meristem (bud) has died, so no new growth will occur. Although lower leaves may remain green for a number of months after the spear leaf dies, it is in the best interest of the nursery grower or the community to remove the infectious palm as soon as possible. The diseased palm serves as a source of the phytoplasma that can be transmitted by an insect vector to still-healthy, TPPD-susceptible palms.
If TPPD symptoms are present, but the spear leaf has not died, therapeutic treatment of the disease may be achieved by application of the antibiotic oxytetracycline HCl (often referred to as OTC), administered to palms by liquid injection into the trunk. Treatments would continue for the life of the palm on a four-month treatment schedule.
The most effective use of the antibiotic is as a preventive treatment to protect susceptible palms when TPPD is known to occur in the area. Again, these preventative antibiotic treatments should be made every four months. However, only palms known to be susceptible should receive the treatments. To date, palms known to be most susceptible to TPPD are the following: Phoenix canariensis (Canary Island date palm), Phoenix dactylifera (edible date palm), Phoenix sylvestris (wild date palm) and Sabal palmetto (cabbage palm).
The only source for oxytetracycline HCl — a product registered by the U.S. Environmental Protection Agency (EPA) — is TreeSaver® (http://www.palmtreesaver.com). This product is for distribution and use only in Florida. Please read and follow label directions. The Web site for the company provides helpful hints for successful use of this product.
As with LY, landscape disease management of TPPD via control of the vector population is not recommended, especially since the TPPD vector is unknown at this time. Use of host resistance represents the most practical long-term solution. However, the complete palm host range of this phytoplasma is probably not yet known.
References
Harrison, N. A., E. E. Helmick, M. L. Elliott. 2008. Lethal yellowing-type diseases of palms associated with phytoplasmas newly identified in Florida, USA. Annals of Applied Biology 153:85-94.
Harrison, N. A., M. Womack, M. L. Carpio. 2002. Detection and characterization of a lethal yellowing (16SrIV) group phytoplasma in Canary Island date palms affected by lethal decline in Texas. Plant Disease 86:676-681.
McCoy, R. E. 1975. Effect of oxytetracycline dose and stage of disease development on remission of lethal yellowing in coconut palm. Plant Disease 59:717-720.
McCoy, R. E. 1982. Use of tetracycline antibiotics to control yellows diseases. Plant Disease 66:539-542.
Footnotes
1.
This document is PP243, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date, November 2007. Revised February 2009. Visit the EDIS Web site at http://edis.ifas.ufl.edu.
2.
Nigel A. Harrison, associate professor, and Monica L. Elliott, professor, Department of Plant Pathology, Fort Lauderdale Research and Education Center–Ft. Lauderdale, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer’s label.
