Palm tree diseases pictures

Found in warmer growing climates, mealybugs are soft-bodied, wingless insects that often appear as white cottony masses on the leaves, stems and fruit of plants. They feed by inserting long sucking mouthparts, called stylets, into plants and drawing sap out of the tissue. Damage is not often significant at low pest levels. However, at higher numbers they can cause leaf yellowing and curling as the plant weakens. Feeding is usually accompanied by honeydew, which makes the plant sticky and encourages the growth of sooty moulds. Mealybugs are a common greenhouse pest that affect ornamentals, houseplants, avocados and fruits.

Identification

Adults (1/10 — 1/4 inch long) are soft, oval distinctly segmented insects that are usually covered with a white or gray mealy wax. Small nymphs, called crawlers, are light yellow and free of wax. They are active early on, but move little once a suitable feeding site is found.

Note: There are approximately 275 species of mealybugs known to occur throughout the United States.

Life Cycle

Adult females deposit 300-600 eggs within an excreted, compact, waxy cottony-appearing mass mostly found on the underside of leaves (these egg cases can be confused with downy mildew). Egg laying is continues for about 2 weeks with the female dying shortly after all eggs are laid. Hatching occurs within 1-3 weeks and the small active yellow nymphs begin migrating over the plant in search of feeding sites on which to settle. As they feed, they secrete honeydew and a waxy coating begins to form over their bodies. Female nymphs pass through three stages (instars) with a generation taking as little as one month, depending on temperature. Male nymphs pass through five instars. They do not feed after the first two instars and exist solely to fertilize the females. In the greenhouse, continuous and overlapping generations occur throughout the year. There is little winter survival outside of greenhouses in the North.

Mealybug Control

  1. Prune out light infestations or dab insects with a Q-tip dipped in rubbing alcohol.
  2. Do not over water or overfertilize — mealybugs are attracted to plants with high nitrogen levels and soft growth.
  3. Commercially available beneficial insects, such as ladybugs, lacewing and the Mealybug Destroyer (Cryptolaemus montrouzieri), are important natural predators of this pest.
  4. Use the Bug Blaster to hose off plants with a strong stream of water and reduce pest numbers. Washing foliage regularly with a leaf shine — made from neem oil — will help discourage future infestations.
  5. Safer® Insecticidal Soap will work fast on heavy infestations. A short-lived natural pesticide, it works by damaging the outer layer of soft-bodied insect pests, causing dehydration and death within hours. Apply 2.5 oz/ gallon of water when insects are present, repeat every 7-10 day as needed.
  6. Neem oil disrupts the growth and development of pest insects and has repellent and antifeedant properties. Best of all, it’s non-toxic to honey bees and many other beneficial insects. Mix 1 oz/ gallon of water and spray every 7-14 days, as needed.
  7. BotaniGard ES is a highly effective biological insecticide containing Beauveria bassiana, an entomopathogenic fungus that attacks a long-list of troublesome crop pests – even resistant strains! Weekly applications can prevent insect population explosions and provide protection equal to or better than conventional chemical pesticides.
  8. Fast-acting botanical insecticides should be used as a last resort. Derived from plants which have insecticidal properties, these natural pesticides have fewer harmful side effects than synthetic chemicals and break down more quickly in the environment.
  9. Washing foliage regularly with a leaf shine will help discourage future infestations.

Tip: Control ants when releasing beneficial insects. Ants feed on the honeydew that mealybugs produce and protect the bugs from predators to ensure this food supply.

How To Get Rid Of Mealybugs

If you notice that your plant looks like it is covered with snow or leaves have some white spots, your plant is under the attack of Mealybugs.

No need to panic, we know the way how to get rid of these fluffy visitors.

Read below:

Inspect all your plants regularly to ensure early detection. It’s far easier to rid of a small infestation than to eradicate a full-blown attack but you should definitely try 😀

Isolate the infected plants from the rest of the plants. If you touch or treat this plant, make sure to wash your hands before touching any other plants.

Remove all yellow and brown leaves.

Suggested cure:

a) Dishwashing liquid – for light infestation.

Any soap will effectively suffocate the mealybugs as the soap coats the bug and also breaks down their protective waxy layer. Just mix the dishwashing soap in water and spray on the plant twice a week until all white spots disappear.

Check on your plant regularly, and spray this mixture if you see any of the symptoms return.

b) Neem oil – for light to medium infestation.

Neem oil is non-toxic. Oil derived from the Neem tree has insecticidal properties in addition to being a fungicide and having systemic benefits.

Clean mealybug infestations with a moist cotton ball. Spray affected area after, and continue to spray once a week until all white spots disappear.

Check on your plant regularly, and spray Neem oil if you see any of the symptoms return.

Purchase Neem Oil here – http://amzn.to/2un4fcz

c) Rubbing alcohol – for heavy infestation.

Clean mealybug infestations with a cotton ball dipped in rubbing alcohol. Simply dab the critters and rub them away. The alcohol strips away the waxy coating leaving the mealybugs exposed.

After you cleaned your plant, spray it with alcohol. Continue spraying twice a week until all white spots disappear. Check on your plant regularly, and spray alcohol if you see any of the symptoms return.

Green Luck To You!!!

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How To: Get Rid of Mealybugs

Photo: istockphoto.com

At first glance, mealybugs definitely don’t look like your typical pest. Their 1/16- to 1/8-inch-long bodies are white, oval in shape, and covered with wax, which makes an infestation look more like cotton balls than bugs. Even with this relatively distinct appearance, they can be hard to spot since they gravitate toward the undersides of leaves, leaf axils, or protected areas at the base of certain plant varieties. Typically you’ll find these pests in warmer climates, targeting citrus trees and ornamental plants such as orchids, gardenia, English ivy, fuchsia, coleus, and more, both indoors and outdoors but especially in greenhouses.

When they latch onto your greenery, mealybugs will suck out its sap (its primary food source) and harm the plant. While low numbers may not cause significant damage, large populations can slow plant growth, so you’ll want to keep an eye out for signs. Mealybugs may cause existing leaves to turn yellow and new growth to fail, and they excrete wax and sticky honeydew, which is often accompanied by black, sooty mold—any of which are good indicators that the mealybug may be the culprit for failing plants, even when the bug itself may otherwise be hard to spot.

Once you’ve ID’ed the pests, it’s time to try out some strategies for how to get rid of mealybugs.

Step 1: Removal

Chemical treatments typically aren’t very effective because they are repelled by the mealybug’s waxy coating. Try these methods as your first course of action.

Photo: istockphoto.com

• Manual removal of the bugs: Hand-pick mealybugs from infested plants if there aren’t a prohibitive number of pests present. Use a drop of isopropyl alcohol on a cotton swab and dab it on the bug to remove it. Test the solution on a small part of the plant one to two days ahead of time to make sure it doesn’t burn the leaf. Spray sturdy plants with forcible streams of water if mealybugs are present to knock large numbers of them off the plant.

• Introduction of natural enemies: Some predatory insects that prey on mealybugs can help control the mealybug population under controlled settings. The Cryptolaemus montrouzieri, known as the mealybug destroyer, is available commercially—if you can’t find them available at your local garden center, they can be ordered online—to be released in greenhouses.

• Control of the ant population: Ants are known to protect mealybugs from natural enemies, so they can feed upon the honeydew produced by the mealybug. Use ant control techniques if you spot unusual numbers of ants on your plant.

• Removal of the infested plant: Finally, often the best course of action is to remove the source plant completely if it’s heavily infested to minimize further spread. Once you’ve done that, inspect pots, tools, and other materials that may have come into contact with the plant for mealybugs and egg sacs; discard or clean any that show signs of infestation.

Where there is too large a population to use manual or biological methods, consider insecticides. Though they won’t speedily wipe out your entire infestation, the young mealybugs will be affected of first, as they are particularly susceptible because they haven’t yet developed their full waxy protective covering. Insecticidal soaps, horticultural oil, or neem oil insecticides may provide some suppression. Rotate methods each time you apply an insecticide to delay resistance; multiple applications will be needed throughout the season for best results. Make sure to apply these thoroughly to the undersides of the plant, since that is where mealybugs often hide.

Step 2: Prevention

Now that they’re gone, make sure mealybugs never get in your garden again. Always inspect every new plant for mealybugs—remember: watch out for honeydew and black mold on leaves—before bringing them home. As you grow your garden with new plant purchases, you may also want to work with the garden center expert so as to stay away from plants known to be mealybug bait.

Palm trees are one of the defining characteristics of our beautiful Florida landscapes. However, these magnificent trees can become eyesores if infected by disease or insects. If left untreated, worse case scenarios can mean the total loss of your once gorgeous palm trees. Let’s take a deeper look at the diseases and insects that can prey on your palm trees and how our tree care experts at Superior Spray Service can help.

Fusarium Wilt

Fusarium Wilt is one of the greatest threats to the health of your palm trees. It is a fungal disease that is spread from palm to palm. It is commonly spread through the use of dirty or contaminated pruning equipment. The fungus clogs the water-conducting tissue in a palm. This leads to progressive wilt and, eventually, death. This disease has run rampant leading to the death of many Canary Island Date palms. In many cases, Fusarium Wilt develops in a palm tree when a homeowner chooses to prune the palm themselves. The use of equipment that has not been properly disinfected between uses allows the fungus to infect the tree.

Lethal Yellowing

Lethal yellowing is most commonly seen on the Coconut and Christmas varieties of palm trees. Although this disease can be hosted by a wide variety of palm species. The disease is caused by a phytoplasma, a type of bacterial parasite, and is transmitted by an insect called a leafhopper.

Ganoderma Butt Rot

This fungal disease attacks and deteriorates the lower trunk of a palm tree. All palms are susceptible to and can host the fungus, referred to as Ganoderma Zonatum. There is no known way to prevent this disease, nor is there a known cure. A palm that is infected with Ganoderma Zonatum fungus should be removed as soon as possible by a professional. If is not removed the fungus can spread to the soil. Therefore you should not plant a new palm in the same location.

Texas Phoenix Palm Decline

Texas Phoenix Palm Decline is caused by a strain of phytoplasma and affects palm trees in Florida and Texas. This disease showed up in Florida in 2006. Since then it has had a devastating effect on palms across the state. Symptoms of this disease include a fruiting palm dropping most, or all of its fruit in a short time period, as well as discolored foliage.

Rugose Spiraling Whitefly

This insect, which is very common in Florida, produces “honeydew”, a sugary substance that is sticky and messy. It will stick to your trees, as well as your house, car and other property. As with most insects, they have the tendency to multiply rapidly. Infested areas can look like they are dusted with snow. The honeydew substance can also lead to the build-up of a dark, sooty mold that results in leaf drop.

How Can I Protect My Palm Trees?

If left untreated, these problems can be disastrous to your palm trees. Our tree care professionals can determine if your palm trees are suffering from any of the above problems. If so, they will identify which one and be able to treat it immediately.

At Superior Service, our technicians are skillfully trained and certified by Arborjet to provide preventative and curative treatments for various trees and palms. Arborjet is an eco-friendly method to protect trees against pests and disease. Arborjet substances are injected directly into the trunk of the tree. Therefore minimizing any impact on you, your family, and the environment surrounding the tree.

Do you think your palm trees could be suffering from diseases or insects? Give us a call at 863-682-0700 to schedule a free consultation with one of our professionals today.

Superior Spray Service is proud to serve customers in Lakeland, Orlando, and Tampa and the surrounding central Florida areas. Follow us on Facebook and Instagram

Palm Tree Pests

There’s a new way to help with these beetles. It’s called a light trap. Date farmers with large numbers of trees are using them for their orchards.

If you are positive of an infestation then the best control could be destruction of the tree before the larvae become adults.

They will ALL then look for other nearby trees to infest and before you know it many trees in a wide area are infested.

Spider Mites-Palm Tree Pests

Spider mites can be a particular problem for palms and lots of other plants kept indoors.

They also thrive in dry areas.

These palm tree pests feed on any part of the leaf.

They will leave behind a very fine thin webbing usually running between the fronds on the underside.

You may even be able to see the tiny dots busily moving around on the foliage.

Look for your leaves to spot with yellow or even stipple. The whole leaf may even look like it is paler than normal in color.

Treatment of spider mites includes a wash- not just mist- with insecticidal soap or horticultural oil.

There are also products called miticides that are specially formulated to combat these pests.

If you have a severe infestation then the miticides may prove the better product to gain a handle on them.

Then the others can be used once a month in a preventative manner -like a wash or mist bath.

I hope you have a better knowledge and understanding of what to look for as well as how to treat the most common palm tree pests.

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NOTE : About Buying Palms

If you are looking to buy palm trees of any kind then I would highly recommend purchasing through the Real Palm Tree Store.

They are a huge nursery based in Florida with connections to many quality growers.

Whether you are ordering from inside the United States, Canada or another part of the world– ordering one tree for your landscape or many for a commercial project– I’m confident you won’t be disappointed.

Their customer service is second to none; all products are high quality and backed by a money back 100% satisfaction guarantee.

Make sure to visit real palm trees, ask questions and read the reviews before buying anywhere else.

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Palm Tree Passion > Palm Tree Care > Palm Tree Pests

Symptoms and Biology: The palm has a much reduced canopy of leaves. Symptoms usually appear in older or lower leaves in the canopy first, then move toward the upper or newest leaves, although occasionally mid-canopy leaves are affected first. Leaves turn yellow then brown but remain hanging on the palm.

Initially symptoms might affect the leaflets or pinnae on only one side of the leaf. Pinnae on the other side remain green, although they eventually also will turn brown and die. This pattern was once thought to be diagnostic for Fusarium wilt, but other diseases such as petiole and rachis blights and pink rot also can cause one-sided death of leaves. Pinnae death typically occurs first at the base then moves progressively toward the leaf tip, although this pattern sometimes is reversed.

In contrast to petiole and rachis blights (see later), which also produce one-sided leaf death but only on a few leaves, typically with Fusarium wilt many leaves in the canopy are affected or dead. The quantity of diseased or dead leaves or green, healthy leaves in the canopy can help to identify most cases of Fusarium wilt. Typically with Fusarium wilt a preponderance of leaves in the canopy will be affected or dead. Similarly, if the palm is frequently pruned to remove dead leaves and constantly appears to have a much reduced canopy of living leaves, it likely has Fusarium wilt.

Another common symptom of Fusarium wilt is extensive, external, brown to black discoloration or streaking along the petiole and rachis. This streaking corresponds to internal discoloration of vascular tissue when viewed in transverse section. Internally the tissue is reddish-brown and often has a slight pinkish blush; although incompletely understood, this pinkish discoloration might be diagnostic for the disease.

In the landscape, Fusarium wilt nearly always spreads on pruning tools, especially chain saws. The pathogen enters cut petioles and, in extreme cases, the cut and exposed vascular tissue of severely pruned or skinned trunks (trunks where the persistent leaf bases have been skinned or peeled off). The pathogen can spread indirectly during pruning, because contaminated sawdust can drift as far as 100 feet.

The pathogen also can spread by entering the palm through its roots. Canary Island date palms tend to form a dense, extensive network of above-ground roots called pneumatophores, especially under excessively damp or wet conditions, and these may facilitate pathogen entry.

Fusarium wilt might spread if people dispose of diseased palms or their seeds using a municipal yard-waste program that recycles debris into mulch. The pathogen can survive in the soil for at least 25 years.

Infected palms can die within a few months after symptoms appear, or they can linger for several years. Because wilt diseases decrease the ability of the host to take up water, palms with Fusarium wilt in cooler, more humid environments such as near the coast, might show reduced disease severity and survive for many years. Infected palms in hotter, drier interior climates might show severe symptoms and die rapidly.

Because Fusarium wilt stresses palms, the opportunistic and mostly secondary disease pink rot is frequently present and can obscure or mask symptoms and hasten death. In fact, pink rot might kill a palm before Fusarium wilt runs its course.

Management: Because no cure exists for Fusarium wilt and it is nearly 100 percent fatal, prevention and exclusion are critical to disease management. When first planting, obtain palms from a reliable source, and avoid poorly drained soils and excessive irrigation that can increase the formation of above-ground roots.

Keep the area around the base of the trunk free of plants, which can damage above-ground roots, and avoid using municipal yard waste as mulch on Canary Island date palms.

Do not replant a Canary Island date palm in the same site where one died or was removed because of Fusarium wilt. The fungus surviving can infect a new, healthy palm. Instead, use other species of palms including Mexican blue palm, San Jose hesper palm, Guadalupe palm, pindo palm, queen palm, and Mexican fan palm.

If you want the date palm “look,” consider staminate (male) plants of the date palm (Phoenix dactylifera), which are more robust than the pistillate (female) fruit-bearing plants and more closely imitate the larger, robust habit of Canary Island date palms.

Frequently pruned Canary Island date palms are more likely to suffer from Fusarium wilt than those in an unmaintained setting. If you must prune, thoroughly clean and disinfect all tools prior to work on each palm by vigorously brushing them to remove sawdust and other particles. Disinfect the tools for 10 minutes in a 1:3 pine-oil-to-water solution, 1:1 solution of household bleach, or heat saw blades for at least 10 seconds per side with a handheld butane torch. Clean and disinfect (as described above) all tools used in the root zones of Canary Island date palms such as shovels, spades, rakes, hoes, and weeders, because they can spread the disease.

Use manual pruning saws rather than chain saws whenever possible, because chain saws are difficult if not impossible to clean and disinfect adequately. If you have extremely valuable palms, consider using a new saw for each tree, which you either could discard after one use or dedicate for future use on that one palm only. Avoid pruning palms in windy weather to minimize the spread of sawdust.

Because a Canary Island date palm with Fusarium wilt eventually will die, it is prudent to remove it as soon as possible. To avoid spreading the pathogen, excavate the root ball and use a crane to remove the palm with its crown of leaves, trunk, and root ball still attached, if possible. Keep cutting, grinding, and digging to a minimum.

Use plastic or wooden barriers to contain sawdust and other diseased plant parts during removal. After collecting and securely bagging all debris, prepare removed palms for incineration or removal to a landfill; do not use a waste recycling program. Removing the soil will likely not prevent the spread of Fusarium wilt because just one small piece of infected root is all that is necessary to infect a newly planted palm.

Table 2. Common Palms of California and Their Relative Disease Susceptibility.

Mostly Disease Resistant Diamond
Scale
Fusarium
Wilt
Petiole/Rachis
Blights
Pink
Rot
Sudden
Crown Drop
Australian fountain palm (Livistona australis) X
Bamboo palm (Chamaedorea spp.) X
California fan palm (Washingtonia filifera) X X X
Canary Island date palm (Phoenix canariensis) X X X X
Chinese fountain or fan palm (Livistona chinensis) X
Chinese windmill palm (Trachycarpus fortunei) X
Date palm (Phoenix dactylifera) X X X
Fishtail palm (Caryota spp.) X
Guadalupe palm (Brahea edulis) X
Kentia palm (Howea forsteriana) X
King palm (Archontophoenix cunninghamiana) X
Lady palm (Rhapis spp.) X
Majesty palm (Ravenea rivularis) X
Mediterranean fan palm (Chamaerops humilis) X
Mexican blue palm (Brahea armata) X
Mexican fan palm (Washingtonia robusta) X X
Pindo palm (Butia odorata; sometimes known by the misapplied name B. capitata) X
Pygmy date palm (Phoenix roebelenii) X X
Queen palm (Syagrus romanzoffiana) X
San Jose hesper palm (Brahea brandegeei) X
Senegal date palm (Phoenix reclinata) X X
Triangle palm (Dypsis decaryi) X

PETIOLE AND RACHIS BLIGHTS

Cocoicola spp. and Serenomyces spp. are the primary pathogens causing petiole and rachis blights in palms although other fungi, including Diplodia, Dothiorella, Fusicoccum, Macrophoma, Phoma, and Phomopsis have also been implicated. The diseases cause the petiole (the slender stalk holding the leaf blade to the leaf base) and sometimes the rachis (the extension of the petiole with pinnae along its length), and then the entire leaf to die. Although typically not lethal, they can stress the palm sufficiently that other diseases kill it.

Hosts: Petiole and rachis blights primarily attack date palms and California and Mexican fan palms.

Symptoms and Biology: The palm often has a reduced canopy of leaves. Lower or older leaves are first and most severely affected. In the pinnate-leaved date palms pinnae typically die on one side of leaf blade first, with those on the opposing side remaining green (compare with Fusarium wilt earlier). In the fan palms, segments in the leaf blade yellow and die in a wedge-shape pattern. In both types of palms the petiole and rachis typically have a reddish brown, dark brown, or even black streak that corresponds to internal discoloration of vascular tissue when viewed in transverse section. Close examination of diseased petioles and rachises might reveal fungal structures of the pathogen, especially fruiting bodies, causing the blight. Eventually the entire leaf dies.

In contrast to Fusarium wilt on Canary Island date palms, which also produces one-sided leaf death and affects many leaves in the canopy, typically with petiole and rachis blights only a few leaves in the canopy are diseased.

While pinnae (of a pinnate leaf) or segments (of a fan or palmate leaf) die, they are not infected; only the petiole or rachis is infected. Pinnae and segments die because the pathogen has caused vascular tissues in the petiole or rachis to die. Although the disease can move higher into the canopy, killing more leaves, it rarely kills the palm; however, it can weaken or stress a palm so that another disease like pink rot can kill it.

Management: Little is known about management of petiole and rachis blights and environmental factors that favor disease development. Because fungal spores are probably the primary methods of disease spread and high humidity is likely an important factor encouraging disease development, sanitation and water management are critical in managing these blights.

Removal and disposal of affected leaves might be a means of reducing disease spread to nearby palms. On smaller palms avoid overhead irrigation. Maintain palms in optimal cultivation and health as described earlier.

PINK ROT

The fungus Nalanthamala vermoeseni (previously called Penicillium vermoeseni or Gliocladium vermoeseni) causes the disease pink rot. Caused by a weak but opportunistic pathogen, pink rot primarily is a secondary disease that affects stressed, weakened, and or wounded palms. While it can attack all parts of a palm, it is most problematic in the growing tips, or apical meristem where new leaves are produced, and in newly emerged leaves. Its role in causing trunk decay on queen palm and other species is unconfirmed.

Hosts: Pink rot can affect nearly all outdoor landscape and indoor palms in California, including king palms, bamboo palms, some date palms, Chinese windmill palms, kentia palms, queen palms, and California fan palms.

Symptoms and Biology: Symptoms of pink rot are variable and include spotting and rotting on nearly any part of the palm. Symptoms occur on leaf bases, petioles, rachises, blades, the apical meristem area where leaves are produced, inflorescences (flower stalks), roots, and even the trunk although this latter occurrence is unconfirmed in many cases. Stunting, distortion, discoloration and even death of new leaves as they emerge from the apical meristem is common. Pinkish spore masses, from which the disease derives its name, are often present, especially when protected behind overlapping leaf bases or other structures. Brownish syrupy exudate also might be present. Infected plants weaken and decline and eventually can die, especially if the apical meristem is attacked.

Like diamond scale, disease severity frequently can be cyclical in large, established palms. For example, the pathogen can infect growing tips and spear leaves, the youngest leaves that have not yet unfolded, during the cooler, moist weather of winter and spring when leaf production and growth are slow. This scenario is especially true of California fan palms. As weather warms in late spring and early summer and the winter-produced spear leaves push out and unfold, previous damage appears even though the disease no longer is active. The palm then produces an abundance of disease-free leaves during vigorous summer and fall growth. As leaf production and growth slow in the winter, the disease becomes more active again. This cyclical nature and the way palms produce leaves sequentially in the crown often results in a distinctive pattern of a few damaged leaves regularly distributed among otherwise healthy ones.

Cultivation or environmental conditions can stress or weaken palms, making them susceptible to pink rot. These conditions include:

  • palms planted too deeply
  • transplanted palms, especially when done at the incorrect time of year, such as the fall and winter
  • excessive irrigation
  • poor drainage
  • poorly aerated root zones
  • improper nutrition
  • pest infestations and other diseases and disorders
  • cold weather or freeze damage
  • inappropriate pruning and leaf-base removal
  • poorly adapted species

Although not always necessary for disease development, wounds facilitate pathogen entry and increase infection risks. Avoid injuring palms when pruning and performing other horticultural procedures. Especially avoid premature leaf-base removal, which can tear and wound the trunk, causing permanent damage and increasing infection risk.

High humidity and temperatures of 65° to 80°F favor the pathogen and disease development. Palms grown in cool, humid, coastal areas are more susceptible to pink rot than those grown in warmer, more arid, inland sites. Pink rot is unusually problematic on bamboo palms produced in humid greenhouses nurseries, especially if overhead sprinkler irrigation is used; in these situations it causes leaf and trunk rot, bleeding, wilt, and death.

The fungal spores that cause pink rot are everywhere and can travel by wind and water; therefore, removing and disposing of infected leaves is probably not a viable management strategy.

The judicious and temporary use of some fungicides can be effective in suppression of pink rot until the cultivation problems stressing the palm can be corrected; however, fungicidal treatment alone is not a viable management strategy. Fungicides can be beneficial after heavy pruning to protect wounds and freshly cut, immature tissue, or both, or temporarily to protect stressed palms in unfavorable environmental conditions.

SUDDEN CROWN DROP

Sudden crown drop is a lethal disease where, as the name implies, the entire crown, including the canopy of leaves and upper part of the trunk, which can weigh several tons, fails and drops from the top of the trunk with little or no warning. Hidden internal decay weakened the trunk until it could no longer support the crown.

Although the fungus Thielaviopsis paradoxa has been isolated from Canary Island date palms that have failed due to sudden crown drop, it is unconfirmed that this pathogen is the primary cause of the disease. Other pathogens might be involved, either alone or in tandem with T. paradoxa.

Hosts: Sudden crown drop primarily affects Canary Island date palms and, to a lesser extent, date palms.

Symptoms and Biology: Unfortunately, no conspicuous symptoms of sudden crown drop occur. The canopy of leaves typically remains green and healthy and the outer layer of trunk tissue (pseudobark) appears normal and intact, making this disease extremely problematic to detect. However, internally hidden decay is destroying the trunk in a roughly hourglass shape, with the healthy tissue on the inside and the decayed tissue on the outside still within the intact pseudobark. Sufficient healthy tissue remains inside the trunk to maintain a normal-appearing canopy of leaves. Eventually, the healthy tissue in the “waist” or constricted part of the hourglass is insufficient to support the weight above it, and the trunk fails, suddenly dropping the crown of leaves and attached portion of trunk.

Although cultural factors, including drought stress, may promote disease development and severity in Canary Island date palms, the extensive use of chain saws to prune leaves and to shape and sculpt “pineapples,” the ball-like mass of persistent leaf bases just below the leaves, and especially to “skin” or “peel” trunks of old, persistent leaf bases can create gaping wounds that facilitate pathogen entry and onset of decay. Thus, annual screening or testing is essential for detection.

Frequently pruned Canary Island date palms, especially those with a history of chain saw pruning, are the most susceptible to sudden crown drop. Look for palms with sculpted pineapples or, especially, skinned or peeled trunks below the leaves where the surface appears smooth, devoid of elliptic leaf base scars, or even straight-sided instead of round, sure indicators of past chain saw use. Not only can such severe pruning create entry sites for the pathogen, the typical position of such pruning, high up on the trunk where tissues have yet to attain anywhere near their maximum strength and resistance to decay, increases the likelihood of decay and crown drop.

Management: Avoid pruning practices such as sculpting pineapples, and skinning or peeling trunks of old leaf bases, which typically create large wounds that facilitate pathogen entry.

Thoroughly clean and disinfect all pruning tools prior to work on each palm by vigorously brushing them to remove sawdust and other particles. Disinfect the tools for 10 minutes in a 1:3 pine-oil-to-water solution, 1:1 solution of household bleach and water, or heat the saw blades for at least 10 seconds per side with a handheld butane torch. Clean and disinfect as described all tools used in the root zones of Canary Island date palms, such as shovels, spades, rakes, hoes, and weeders, which can spread the disease.

For detection of sudden crown drop use a heavy rubber mallet or sturdy wooden stick to sound and listen for hidden decay in the upper part of the trunk. When sharply struck, healthy tissue emits a solid, sharp, resonating tone and the stick bounces back quickly. In contrast, decayed tissue emits a low, dull thud when sharply struck and the stick does not bounce back with much force. If sounding detects decayed tissue, then the area can be probed with a long, sharp, slender tool to determine extent of decay. If decay is extensive, the palm should be removed.

Because a Canary Island date palm with sudden crown drop will eventually die and poses an extreme and imminent hazard, it is prudent to remove it as soon as possible following the same procedures outlined earlier under Fusarium wilt to prevent the spread of pathogens.

WARNING ON THE USE OF PESTICIDES

Broschat TK, Hodel DR, Elliot ML. 2014. Ornamental Palms: Biology and Horticulture. Hort. Rev. 42: 1-120.

Downer AJ, Uchida JY, Elliott ML, Hodel DR. 2009. Lethal palm diseases common in the United States. HortTech. 19: 710-716.

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PUBLICATION INFORMATION

Pest Notes: Palm Diseases in the Landscape
UC ANR Publication 74148

AUTHOR: Donald R. Hodel, UC Cooperative Extension, Los Angeles County

TECHNICAL EDITOR: K Windbiel-Rojas

ANR ASSOCIATE EDITOR: AM Sutherland

EDITOR: B Messenger-Sikes

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