Pink Rot

Pink Rot is an opportunistic disease that attacks weak or stressed palms. Palms lack the ability for secondary growth, which means they are not able to repair damaged tissue. This makes them more susceptible to diseases such as Pink Rot when damaged or pruned heavily. Various species of palms are susceptible to the disease, including many popular varieties found throughout Southern California, such as California Fan Palm (Washingtonia filifera), King Palm (Archontophoenix cunninghamiana), and Queen Palm (Syagrus romanzoffiana). The pink spores are often visible and can be found at the area of infection. This disease can attack any part of the plant including the trunk, but most often affects new growth.

Management Practices for Pink Rot

Selecting the right plant for your location is key. California Fan Palms (Washingtonia filifera) are native to the deserts of Southern Californian. They don’t do well along the coast, so don’t plant them there. Plant at the right time. Don’t plant palms in the middle of winter. Proper cultural care is crucial. Water and care for your palms properly. Avoid wounding the palm. An open wound is a perfect opportunity for Pink Rot to attack. Fungicides can be used to suppress the disease, but the cause of the stress has to be addressed to completely control Pink Rot.

Fusarium Wilt

Primarily attacks Canary Island Date Palms (Phoenix canariensis). It is a vascular disease which means it attacks the plants ability to move water and nutrients through it’s system. There are forms of Fusarium that are species specific. It’s primarily spread by pruning tools. There is no cure for the disease. It is 100% fatal; however, it is nearly 100% preventable through the use of safe pruning practices. When infected, the lower leaves die back as the palm dies from the bottom up. The fronds will often die on only one side. While this is a good indicator of Fusarium, it’s not always 100% accurate as other diseases may cause similar symptoms.

Management Practices for Fusarium Wilt

Prevention is important because there is no cure. Don’t use chainsaws to prune because they can cause large open cuts that are susceptible to disease. Prune with a hand saw instead and disinfect the blade between trees. Remove diseased palms as soon as possible since once infected, the disease is 100% fatal. Avoid spreading the soil or replanting the same species in the same location as a previously diseased tree, since Fusarium may be present in the soil. Control water runoff as it may carry the disease to a new location and infect other trees. Control trunk and root debris. Saw dust was collected in an experiment during the removal of an infected plant. They were able to grow Fusarium from the saw dust in a petri dish. Saw dust blowing around during pruning could potentially spread the fungus to adjacent palms.

Sudden Crown Drop

Sudden Crown Drop primarily affects both the Canary Island Date Palm (Phoenix canariensis) and to a lesser extent Date Palm (Phoenix dactylifera). As the name implies, this disease causes the crown, or top of the palm, to just suddenly topple over, often with little or no warning. This is potentially dangerous and people have been killed in the past from falling debris. At first look, the crown appears normal. The trunk decays internally, and it’s not until you look at the cut away sections that you can see how the disease chokes the plant. Infection is typically caused by excessive pruning.

Management Practices for Sudden Crown Drop

Once again, prevention is key since no cure is available. Management practices are similar to what was previously mentioned for Pink Rot and Fusarium Wilt including proper selection and cultural care. Do not use chainsaws or spikes. Disinfect hand saw blades between trees. A mallet can be used to tap the trunk and listen for areas of decay.

Diamond Scale

Diamond Scale is a fungal disease and not an insect as the name may imply. It primarily attacks California Fan Palms (Wasahingtonia filifera) and usually only those located in areas of marine influence. The fruiting bodies are black in color and diamond shapes. They look similar to scale, hence the name, and are found on the leaves.

Management Practices for Diamond Scale

There is no chemical control for Diamond Scale. Don’t plant Washingtonia filifera near the ocean. Use Mexican Fan Palm (Washingtonia robusta) or Guadalupe Palm (Brahea edulis) as an alternative in coastal areas.

Summary of Best Management Practices for Palm Diseases

Proper planting/transplanting is important in reducing stress to palms. Don’t plant during the fall and winter months. Don’t plant palms too deep. Practice proper cultural care methods. Don’t over-water and make sure to provide good drainage. Avoid causing wounds by not using chainsaws or spikes if possible. Practice good sanitation by properly removing and disposing of debris. Most importantly select the proper species for the location.

The above material was based on a presentation by Donald Holden. For further information please see the article “Palm Diseases in the Landscape” by Mr. Holden.  West Coast Grounds Maintenance is a commercial landscape contractor serving the Los Angeles and Orange County areas. If you have any questions we can be reached at (800) 339-2102 or by email at info @ wcgminc.com. If you would like a quote for services, please fill out the quote request form on our Contact Us page.

Topping or hat-racking as it’s also known, is much too common. Even professional landscape contractors have been guilty of this atrocious act. So why would anyone, professional or not, want to top a tree anyway? The main reason is to limit the size of the tree, and there are many legitimate reasons to want to do so. Safety, security, view restoration, and utility line clearance are just a few. However, in most instances topping is not necessary. It’s common because it’s the fastest and easiest way to quickly reduce height, especially for an untrained or inexperienced tree worker. There is one pruning method that can be used to reduce the size of a tree and I’ll discuss that more in detail later. First, let’s cover some of the consequences of topping.

• Damage to Aesthetics: Topped trees are unsightly because the trees are completely defoliated, and only the bare trunk and branches are left. Topping destroys the natural look of the tree, permanently in most instances.The rapidly growing shoots that grow in reaction to the severity of the cuts can also be unsightly.
• Death: Many times severe topping can ultimately result in the death of the tree. Topping leaves large wounds that are susceptible to disease, decay, or insects. You’ve also removed most or all of the foliage, the energy producing portion of the tree, effectively causing starvation. With no canopy the tree is now completely exposed to sun, which can cause shock and potentially lead to death as well.
• Rapid Growth: Occasionally property managers will top a tree heavily thinking they won’t have to prune it again for a few years in an attempt to save money. That actually has the opposite effect. The problem is that because the topping cuts leave large wounds, the tree’s response is to rapidly push new growth known as watersprouts. These sprouts are more numerous, weaker, and tend to grow straight up. In the end you will have to prune sooner rather than later.
• Weak Limbs: Improper pruning cuts can lead to decay. Sometimes that decay can work it’s way into a point on the tree that can cause severe weakening of a large limb. I’ve seen some cases where the decay wasn’t visible until the limb had split off. Watersprouts are also weakly attached and can more easily break than normal growth. Both of these are a serious hazard situation that could potentially injure or even kill someone.
• Monetary Loss: Topping a tree can save money in the short run, but in the long run it can cost much more. If the tree dies there is the cost of removing and replacing the tree. There could be a loss in property value. There is the potential cost of liability if a weak limb were to break and cause loss of property, or worst yet, life. If the property owner were to choose to perform a crown restoration there is great expense in that as well. Crown restoration can take years to accomplish.

Now there is a way to reduce the height of a tree without topping, it’s known as drop crotching. This pruning method involves removing longer branches down to a smaller lateral branch that can replace it. With this method we can reduce the overall height of the tree while still maintaining it’s natural shape. There are other benefits including less injury and stress. Certain trees with strong central leaders, such as pine trees may not be conducive to drop crotching because of their growth pattern and shape. In these cases it’s probably best to remove the tree and replace it with something that will stay below the required height.

As usual, prevention is the best medicine and planting the appropriate tree for that location to begin with would solve most problems. For example, never plant a tree that will grow 60+ feet tall under power lines! Keep trees with large destructive roots, such as a Ficus, away from buildings, walls, and sidewalks. Don’t plant any type of tree or shrub right up against a fence where security might be an issue. I think you get the point. Most people just don’t take the time to stop and look up before they plant. Always take into consideration the mature size of the tree and how that will impact it’s location before planting.

With worsening economic times, I predict that I’ll be seeing more and more hat-racking. As companies look to save some money, they’ll either be hiring contractors that are less than qualified, or prune more heavily to feel that they got their money’s worth. I hope that I am wrong. In the meantime I am doing my part to educate my customers and those around me. As property managers, you can help by ensuring that you’re hiring licensed, professional contractors that understand the ramifications of topping.