Should I Take Down My Bird Feeder?

The highly pathogenic avian influenza (HPAI) virus is threatening the poultry industry and showing up in eagles and other bird species. Does this mean I should take down the hummingbird feeder and put away the water dishes that I set out for local and migrating birds? Watching birds in the garden is a wonderful pastime, so I'd hate to give them up, but I don't want to endanger the small birds that visit us either. 

Hummingbird feeder cleaned and ready for visitors

I turned to the Cornell Lab of Ornithology article, Avian Influenza Outbreak - Should You Take Down Your Bird Feeders, for information and guidance. According to Julie Lenoch, DVD, Director of National Wildlife Disease Program (NWDP), there is low risk of an outbreak of avian flu among wild songbirds. Most of the concern is that a rare individual might transmit an infection to backyard poultry or the poultry industry. This makes it important to keep songbirds and poultry away from each other. 

The article recommends several methods for cleaning feeders, based on research reported in the article Safe Feeding Environment: Feeder Care. Methods include:

• (Most effective) Scrub debris off feeders, soak them for 10 minutes in a diluted bleach solution, and then wash them with soap and boiling water.
• Or, soak them for 10 minutes in a diluted bleach solution or one hour in a weak vinegar solution and then scrub with a clean bottle brush. Rinse thoroughly.
• Or, wash them in a dishwasher on a hot setting. Allow to dry completely before refilling.

Birds visiting the communal water dish

I'm relieved to know that with diligent cleaning practices, I should be able to continue offering fresh water and sugar water to our avian visitors. At least for now!

Learn More

• USDA Avian Influenza and Wild Birds
• USDA Avian Health

Farewell to the Chinese Elm

 Farewell to the Chinese elm (Ulmus parvifolia) that has graced our yard with shade and dappled light for many years. It has also provided sanctuary for the many birds and squirrels that make use of our yard throughout the seasons.

Chinese elm with broken branch (Summer 2021)

The Chinese elm was infected with Anthracnose, a slow-moving fungal disease that causes lesions on leaves, cankers on twigs and stems, and distorted limbs. Eventually the disease can surround a branch, causing it to die and then drop to the ground after heavy rain or wind. Our arborist monitored the tree for the last 20 years, and pruned as needed to keep the tree as healthy as possible. Over the last couple of years though, limb drop has become more frequent. This last summer, two limbs came down in a windstorm, revealing more cankers.

Two broken branches revealed more cankers and disease

The disease had progressed to a point where the tree was no longer safe and had lost quite a bit of its canopy from therapeutic pruning. Time to remove the Chinese Elm! Oakland is known for its trees, and protects them rigorously. We followed the city's procedure and applied for a permit to remove the tree. This request becomes public record, and citizens have several weeks to protest the tree removal. We posted our red card, to indicate the tree in question. The process takes about six weeks.

Permit request procedure invites public discourse

Our permit was issued with no protest, and a crew from Elite Tree Service removed the tree professionally and efficiently. A few days later they returned to grind the stump. I'm sorry to see the tree go, but I did feel a sense of relief that no more branches would be descending into the yard, or onto cars parked on the street.

Chinese elm stump

Remains of the stump after grinding

We requested the wood chips, and ended up with a nice pile of them. They will be recycled here on our small urban lot, and return to the land. 

Wood chips from the Chinese elm

Full view of the oak tree without the Chinese elm

Without the tree, we feel a little exposed to public view, but now have an opportunity to plant a new tree in the prepared area. Farewell to the Chinese elm, but your wood chips remain!

The Chinese Elm Drops a Branch

Our Chinese Elm (Ulmus parvifolia) recently dropped a branch after several days of intense rain. The tree has Anthracnose, a slow moving fungal disease that eats away at the bark and causes cankers. Eventually a branch may become weak and die.

Branch descended from the Chinese Elm (Spring 2019)

The tree dropped another branch about two years ago, in similar circumstances, after the heavy rains that brought us out of the drought. What's unique about the tree is that, in both cases, the limbs descended slowly, making muted snapping sounds as the compromised wood fibers gave way. The branches did not come crashing down as they might have in other trees.

Another branch blocked gate (Spring 2017)

Our arborist has been monitoring the disease over the last 20 years, trying to keep the tree for as long as possible. It has lovely mottled bark, shiny single-toothed leaves, a graceful stance, and provides lovely dappled shade along side our big oak tree. So far we have been able to save the tree. As always, we called Brende and Lambe to clear away the fallen branch, aesthetically prune what remains, and assess the safety of the tree.

The branch has been removed and the tree still provides shade (Spring 2019)

Discriminating Squirrels

Last fall, I noticed the squirrels were leaving many acorns from our Quercus agrifolia on the ground, rather than stashing them. Typically they grab nuts as soon as they fall, scamper to a hiding place, glance around, and then quickly bury the nut. Sometimes they double-back, dig up the nut, and rebury it somewhere else. Instead, they were ignoring many nuts, and burying only a few.

Acorns from Quercus agrifolia in the Bay Area.

Naturally, this behavior change caught my attention. My folks were visiting from Alaska, so we launched an investigation. The first thing we noticed is that almost all of the ignored nuts had a bore hole in them. My dad split open a healthy nut, and several nuts with bore holes. The unhealthy nuts were filled with frass, but no inhabitants.

Acorn with a bore hole.

Two insects that target acorns in the San Francisco Bay Area, are filbert worms (Cydialatiferreana) and several species of filbert weevils (Curculio spp.). After mating in spring, the female filbert weevil drills a small hole in an immature acorn, and inserts her eggs; the female filbert worm lays her eggs on the outside of an acorn, and the larvae bore into the nut. In both cases, the larvae develops and feeds in the acorn, leaving its frass; and then bores out in the fall, moving to the soil until spring. The number of infected acorns varies by year, environmental conditions, and the individual tree. The infestation does not harm the tree, but the acorns are infertile.

Left: healthy acorn. Middle and right: infested acorns.

Interestingly, birds and squirrels can discriminate between the healthy and infected acorns. Much like humans, they separate the infested nuts, and preserve the healthy!

Learn More:

• Filbert Pests in Live Oaks (prepared and edited by John M. Harper, Richard B. Standiford, and John W. LeBlanc)
• Pests of Acorns (prepared and edited by Richard B. Standiford and Pamela Tinnin)

Plant Diseases: Wrap Up

Delve into all the things that can go wrong with your plants via diseases of all types (bacteria, parasites, water molds, nematodes, fungi, and viruses), and the built-in arms race between predator and prey that keeps balance.

Plant distortions and diseases

Getting Started

Diagnose sick plant symptoms, and figure out what to do about it.

Sick Plant Symptoms
Sick Plant Resources
Sick Plant Clinic
Back to School – Plant Diseases (Aug 2012)
Plant Diseases Update (Oct 2012)
Finished Plant Diseases! (Dec 2012)

Plant Diseases

Learn about the main categories of plant diseases, and deep dive into examples of them all.

Plant Diseases – Bacteria Fire Blight   Crown Gall
Plant Diseases – Flowering Plant Parasites Mistletoe   Lichen (not a disease)
Plant Diseases – Water Molds Downy Mildew   Sudden Oak Death
Plant Diseases – Viruses Tomato Leaf Curl Virus (TYLCV)   Grape Leafroll Associated Virus (GLRaV)
Plant Diseases – Nematodes Root Rot Nematodes   Spiral Nematodes
Plant Diseases – Fungi Black Spot of Rose (Ascomycetes)   Cedar-Apple Rust (Basidiomycetes)

Plant Diseases in Action

Head into the field to experience plant diseases all around us in the garden and nature.

SOD Blitz 2013
SODMAP App
SODBlitz Partnership
Mushrooms
Mistletoe in Bend
Clear Lake Plant Diseases
Discriminating Squirrels (Feb 2016)
Summer on the Iron Horse Trail (July 2019)

Books and Movies

Read about plant diseases and plant pathology, and enjoy films where plant diseases play a role.

Five Kingdoms
Essential Plant Pathology
All That the Rain Promises and More ...
Winter Movies 2013: Nausicaa of the Valley of the Wind
Rosemary & Thyme: And No Bird Sings (Jan 2019)

SOD Blitz Partnership

I love the idea of the SOD Blitz partnership between the UC Berkeley science community, the USDA Forest Service, and “citizen scientists” to gather data on Sudden Oak Death. A similar idea has been used to gather information about migration of birds, butterflies, and fish. It also reminds me of the crowdsourcing projects run on the web, using members of the online community to solve complex problems.

Tip blight symptoms on tanoak caused by P. ramorum. Photo by Joseph
O'Brien (Creative Commons Attribution 3.0 License).

SOD Blitz participants are trained to look for symptoms, and to conduct testing on  specimens. The SOD Blitz project website provides information on training dates, symptoms, testing, and meetings.  The 2014 Spring SOD Blitz is currently being organized, so the training schedule has not yet been published. If you are interested in participating in a Blitz, check the website regularly for updates. In the meantime, there are plenty of workshops and lectures scheduled for Fall 2013.

SODMAP App

A free SODMAP application, with SOD Blitz research information, is available as a plugin to Google Earth. It can be installed on the desktop or on smart phones (Android and iPhone). The application shows you visually where SOD Blitz specimens were taken, and the test results. SODMAP categories include infected and uninfected trees, oaks, tanoaks, and water samples.



SODMAP application running on a desktop computer. Click on an icon to drill down to detailed information.

Icons on the map represent either a single record for one of these categories, or multiple records. Drill down to view detailed information, or to see multiple records and their details. Some trees are tagged, and checked every year. Others are sampled randomly from year to year.

This icon indicates a SOD infected tree - here a bay laurel (Umbellularia californica).

On smart phones with GPS, you have the added capability of the app identifying where you are, and automatically displaying details for your surroundings. This is great if you are out in the field. Currently I have SODMAP running on my desktop and iPad, and really enjoy scoping out the results of the San Francisco Bay Area SOD Blitz. 

The icon indicates a SOD infected oak or tanoak tree - in this case live oak (Quercus agrifolia).

SOD Blitz 2013

I recently attended a lecture at University of California, Berkeley (UC Berkeley, or Cal) by Dr. Matteo Garbelotto, to summarize the results of the 2013 SOD Blitz. Dr. Garbelotto is an adjunct professor at UC Berkeley. He received his B.S. and M.S. degrees in Forestry from the University of Padua, Italy, and then completed his graduate and post-graduate work in forest pathology at UC Berkeley. He has been studying SOD since its discovery in California, and is an engaging speaker, making information accessible for both scholar and community. Fittingly, the lecture was held under a mature oak tree outside Tolman Hall on the UC Berkeley campus.

SOD Blitz—or Sudden Oak Death Blitz—refers to an event where professionals and trained “citizen scientists” join forces to fan out over Northern California, look for evidence of Sudden Oak Death, and gather specimens. The specimens are tested and analyzed in the lab. In this way, a lot of field data has been gathered in the last six years to study the introduction and spread of SOD in California. Data is published online, and available via a free app for Android or iPhone. Professionals include USDA Forest Service and the UC Berkeley Forest Pathology and Mycology Laboratory. SOD Blitz also refers to community outreach to inform the community about Sudden Oak Death.

Symptoms of ramorum leaf blight on California bay laurel. Photo by Joseph
O'Brien (Creative Commons Attribution 3.0 License).

Several items interested me. In general, the overall infection rate of tanoaks and live oaks decreases after a dry year, and then spikes after a wet year. However, a comparison between 2012 and 2013 research shows some deviation - increases were observed in two colder areas, and decreases in hotter areas. This supports observations that the disease operates differently between coastal forests and inland forests. Infestation typically happens during the spring rains (March, April, May), and not the early rains in November, December, January, February), so you should avoid pruning during spring rains.

Plants such as bay laurel, Rhododendron, and Camellia are intermediate hosts for Phytophthora ramorum; removing them from the presence of a high value oak can reduce chances of its infection. Use of phosphonate to treat healthy oaks is very promising, but they are reevaluating delivery mechanisms, since plugs may cause damage to the trees. Additionally, Dr. Garbelotto observed that the disease is relatively slow moving, which is giving scientists a chance to study it. These lectures are offered periodically and well worth your time.

Sudden Oak Death

The plant pathogen Phytophthora ramorum, commonly called Sudden Oak Death (or SOD), is a water mold in the Oomycota class. I reported on Sudden Oak Death a couple of years ago as part of a series on oak trees. Most Phytophthora species are soil-dwelling, root pathogens, but P. ramorum is a leaf pathogen. Spores from the leaves and twigs of infected trees spread to an oak through water, wind-driven rain, plant material, or human activity. Once the spores are on the oak, microbes use natural openings to access bark tissues. The microbes kill cells, causing bark cankers, clogged water and transport systems, leaf die-off, and ultimately death of the tree. Take a look at SOD zoospores: http://youtu.be/rTo6UwnZiQg

Fascinating to me is that P. ramorum has a wide host range (including tanoaks, and non-oaks, such as California bay laurel, Rhododendron, and Camellia), but these hosts are not killed by the pathogen. Oaks, on the other hand, are considered terminal hosts; when they encounter the pathogen, they may become infected very quickly in the right conditions. According to the IPM, the best predictor of the disease is the presence of a California bay laurel.

Since there is no cure, prevention is the best way to manage Sudden Oak Death. Purchase non-infested nursery plants from a reputable dealer; remove infected oaks following local ordinances; remove non-oak hosts (such as California bay laurel); and dispose of infected plant debris properly (leave on the property as mulch or compost). The IPM website lists using phosphonate fungicide treatments (Agri-Fos) as a preventative measure. The treatment must be made on healthy trees, and repeated every year or two, so it is recommended for high-value trees.

Essential Plant Pathology

For a great resource for learning about plant diseases, I recommend the text book we used for the Plant Diseases class at Merritt College last fall. Essential Plant Pathology was written by Dr. Gail L Schumann and Dr. Cleora J. D’Arcy, and published by American Phytopathological Society Press in 2010 (Second Edition).

It is not your standard text book, in that the text is very accessible (except for a few deep-dives into genetics), and it is filled with graphics, photos, case histories, high-level summaries, references, web resources, and a CD, all of which are great for visual learners. Case histories, called Disease Classics, appear throughout the text, and describe Host, Pathogen, Symptoms and Signs, Disease Cycle, Management, and Significance. A glossary and index help the reader grapple with new concepts and terminology.

The presentation is organized around plant diseases from the five kingdoms – fungi, bacteria, animals, plants, and protoctista, as well as viruses and environmental factors. The idea is that by understanding the phylogeny of organisms, you can use the information to identify the pest or disease, understand its life cycle, and use the knowledge to mitigate the problem. The book’s emphasis is on learning a system for diagnosing plant diseases, rather than memorizing many plant diseases.

 

Sudden Oak Death

For the past twenty years, oaks in Northern California have been under siege from a plant pathogen called Phytophthora ramorum, commonly referred to as Sudden Oak Death (SOD). P. ramorum produces spores that are dispersed through the air or water, or carried by people, animals, plants, soil, and equipment. The ideal condition for P. ramorum is warm (68 degrees) and moist, making riparian woodlands especially susceptible. Coastal counties from Humboldt to Monterey have been especially hard hit.

Forest near Big Sur, California showing symptoms of Sudden Oak Death.
Photo by Hemhem20X6 (released into the public domain, by the author),

Symptoms include cankers on the trunk or limbs of a tree; and rapid leaf or canopy death over a two to three week period. Quercus agrifolia and Q. kelloggii oaks have a high mortality rate. Other woody plants in the plant community may be hosts to the disease—including rhododendron, California bay laurel, madrone, Manzanita, redwood, coffeeberry, and California buckeye. The pathogen is not native, and may have been introduced through an imported ornamental plant, possibly from Asia. So far there is no known cure; infestations should be reported for diagnosis, since other diseases have similar symptoms.

The California Oak Mortality Task Force was assembled in 2000 to address the pathogen and its affects, and to coordinate with other agencies, universities, and other private and public groups. Several websites provide information: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74151.html, www.suddenoakdeath.org, and www.na.fs.fed.us/SOD.