California Fan Palm - Pests and Diseases
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California Fan Palm

Spear leaf and next youngest leaf exhibiting typical symptoms of Phytopthora bud rot Fig. 1 magnifying glass
Spear leaf and next youngest leaf exhibiting typical symptoms of Phytopthora bud rot 

Only the spear leaf and next youngest leaf are affected by the pathogen; older leaves remain healthy. Fig. 2  magnifying glass
W. robusta
exhibiting typical bud rot symptoms. Only the spear leaf and next youngest leaf are affected by the pathogen; older leaves remain healthy.

Palm Leaf Skeletonizer
Fig. 5 magnifying glass
Palm leaf skeletonizer adult

Foliar yellowing symptoms of Lethal Yellowing on Caryota rumphiana Fig. 11  magnifying glass
Foliar yellowing symptoms of Lethal Yellowing on Caryota rumphiana

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California Fan Palm

Bud Rot of Palm

The most common bud rot pathogen in Florida is Phytophthora palmivora. Thielaviopsis paradoxa may cause this disease also. The first symptom is discoloration and wilting of the spear leaf and wilting/discoloration of the next youngest leaf. If severe, the spear leaf easily pulls from the bud.
In palms with a canopy above eye level, this first symptom is often missed. Instead, a lack of new leaves and an open-topped crown are often the first symptoms to be observed. Because the bud is dead, no new leaves emerge. Older leaves remain healthy for months after the bud dies.
Bud rot is also observed in association with cold damage. Cold damage allows entry of secondary pathogens, both fungi and bacteria.1

Bud rot of Cocos nucifera Multiple W. robusta in this field nursery are being affected by Phytophthora bud rot. Those most affected were juvenile palms in a low-lying area.
Fig. 3 magnifying glass Fig. 4 magnifying glass

Fig. 3. Bud rot of Cocos nucifera: no new leaves are emerging and crown is open-topped, while older leaves in canopy look healthy at this time.
Fig. 4. Multiple Washingtonia. robusta in this field nursery are being affected by Phytophthora bud rot. Those most affected were juvenile palms in a low-lying area.
 
In general, severely diseased plants should be removed and destroyed immediately to limit pathogen spread. Potting mix from diseased container palms should be removed from the nursery. For mature palms, the diseased palm should be removed and the canopy region (including the bud) destroyed. The lower trunk should be pathogen free, so it would be acceptable to chip it and recycle it in the landscape.

Further Reading
Bud Rot of Palm from the University of Florida pdf



Palm Leaf Skeletonizer

Homaledra sabalella (Chambers)

Symptoms appear on mid-canopy to older leaves as necrotic translucent blotches on the leaflets. Often only the epidermal layers of the leaves remain, hence the name "leaf skeletonizer" 2
Caterpillars feed on the upper and lower leaf surfaces, producing large quantities of " frass" that is often the first conspicuous sign of infestation. Tissue between the leaf veins is usually the preferred food, whereby the veins remain intact giving the leaf a skeltetonized appearance.
In Florida, larvae are present throughout the year and complete five generations per year in northern Florida. 3

Palm Leaf Skeletonizer Adult on Palm Leaf Early Instar Larva
Fig. 6 Adult magnifying glass  Fig. 7 Early instar larva magnifying glass
Late Instar Lava Palm Leaf Skeletonizer Damage to Cocos nucifera (pinnate palm) Palm Leaf Skeletonizer Damage to W. robusta (palmate palm)
Fig. 8 Late instar larva magnifying glass Fig. 9 magnifying glass Fig. 10 magnifying glass

The pattern of damage by this insect is different on palmate vs. pinnate palms.
Fig. 9. Palm leaf skeletonizer damage to C. nucifera (pinnate palm)
Fig. 10. Palm leaf skeletonizer damage to W. robusta (palmate palm)

Further Reading
Palm Leaf Skeletonizer from the University of Florida Okeechobee Extension pdf
The Palm Leaf Skeletonizer, Homaledra sabalella (Lepidoptera: Coleophoridae): Status and Potential Pest Management Options pdf 4 pages



Leathal Yellowing
(Fig.11)
Caused by a tiny organism called a phytoplasma

This palm is also susceptible to lethal yellowing disease and should not be planted where other palms are suffering from this always fatal disease.
Lethal yellowing (LY) is a systemic disease caused by a phytoplasma transmitted by a planthopper. Historically, LY has occurred only in the southern one-third of Florida. The disease was observed for the first time in Sarasota and Manatee Counties on the west coast of Florida in 2007 and in Indian River County on the east coast in 2012. LY symptoms are highly variable among Cocos nucifera (coconut) cultivars and among other palm genera. Palms with greater than 25% leaf discoloration or a dead apical meristem (bud) due to LY should be removed. Management of LY includes trunk injections of oxytetracycline HCl (OTC) every four months, and planting of palm species that are not hosts of LY. Very few palm species native to Florida and the Caribbean Basin appear to be susceptible to LY. 5
Lethal yellowing is the most important disease of coconut in Florida. Since LY was discovered in Key West more than 200 years ago, this disease has crept northward, killing hundreds of thousands of palm trees and endangering virtually all of the tall coconut palms in Florida. Lethal yellowing is caused by a tiny organism called a phytoplasma, which is visible only with the aid of an electron microscope. Early symptoms of LY are premature dropping of coconuts and blackening of flower stalks. The palm leaves then turn yellow, beginning with the lower leaves and progressing to the crown, which dies and eventually topples from the tree. The tree usually dies within six months after exhibiting the first symptoms of LY. 4

Further Reading
Lethal Yellowing of Palms from the University of Florida pdf 7 pages
Palm Diseases Caused by Phytoplasmas: Lethal Yellowing and Texas Phoenix Palm Decline from the University of Florida, Fort Lauderdale Research & Education Center


Bibliography

1 Elliott, Monica L. "Bud Rot of Palm." edis.ifas.ufl.edu. This document is PP-220, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication Jan. 2006. Revised July 2012, and Oct. 2015.  Web. 29 Oct. 2015.
2 Anderson, P.J. “Palm Leaf Skeletonizer." itp.lucidcentral.org/id/palms/resource/index.html. Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. 2011. Web. 26 Apr. 2014.
3 Redford, A. J., T.W. Walters, A.C. Hodges, F.W. Howard, and M.D. Trice. "Palm Leaf Skeletonizer." itp.lucidcentral.org/id/palms/resource/index.html.  Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. 2010. Web. 26 Apr. 2014.
4 Broschat, T.K. and Crane, Jonathan H. "The Coconut Palm In Florida." edis.ifas.ufl.edu. This document is HS40, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication April 1984. Revised June 2014. Web. 27 Apr. 2014.
5 Harrison, Nigel A. and Monica L. Elliott. "Lethal Yellowing (LY) of Palm." edis.ifas.ufl.edu. This document is PP-222, one of a series of the Plant Pathology Department, UF/IFAS Extension. Publication Oct. 2005. Revised Aug.2007, Aug. 2009, Aug. 2012, and Oct. 2015. Web. 29 Oct.  2015

Photographs

Fig. 1 Broschat, T. K. and Elliott, M. L. Bud Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig.2,3 Elliott, M. L. Bud Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu Web. 23 Apr. 2014.
Fig. 4 Broschat, T. K. Bud Rot of Palms. N.d. University of Florida-IFAS. edis.ifas.ufl.edu. Web. 23 Apr. 2014.
Fig. 5 Vargo, Jim. Palm Leaf Skeletonizer. 2010. Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. itp.lucidcentral.org/id/palms/resource/index.html. Web. 26 Apr. 2014.
Fig.6,7 Hollenbeck, Jeff. Palm Leaf Skeletonizer. 2010. Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. itp.lucidcentral.org/id/palms/resource/index.html. Web. 26 Apr. 2014.
Fig.8 White, Machele. Palm Leaf Skeletonizer. 2010. Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. itp.lucidcentral.org/id/palms/resource/index.html. Web. 26 Apr. 2014.
Fig. 9,10 Howard, F.W. Palm Leaf Skeletonizer. 2010. Screening Aid to Pests. In A Resource for Pests and Diseases of Cultivated Palms. itp.lucidcentral.org/id/palms/resource/index.html. Web. 26 Apr. 2014.
Fig. 11 Harrison, N.A. Lethal Yellowing. 2011. In A Resource for Pests and Diseases of Cultivated Palms. Florida Department of Agriculture and Consumer Service, Division of Plant Industry and Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. itp.lucidcentral.org/id/palms/resource/index.html. Web. 30 Apr. 2014.

Published 12 Apr. 2014 LR. Last update 29 Oct. 2015 LR
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