Winter Movies 2019: And No Bird Sings

Time for winter movies, where plants play the starring role! This year I've chosen several episodes from the popular Rosemary & Thyme series that aired from 2003 to 2007. This "English cozy" style mystery series stars Felicity Kendal as Rosemary Boxer, and Pam Ferris as Laura Thyme.

The series is set mainly in England, but also in various European and Mediterranean locations (to accommodate the short window for good filming weather). The key for us is that it serves up lots of beautiful gardens, sun-drenched locations, and interesting characters, along with entertaining side dishes of mystery and murder, perfect for beating the dark days of winter.

And No Bird Sings (Season 1, Episode 1)

In the opening episode, Laura Thyme is leaving to see family friends, Sam and Vickie Trent, before checking into The White Hart bed-and-breakfast, after learning that her police officer husband of 27 years has dumped her for a younger woman. At the bed-and-breakfast, she meets Dr. Rosemary Boxer, a plant pathologist who was hired by Daniel and Alicia Kellaway to determine why trees are dying at their estate. Coincidentally, Daniel is suffering from severe skin and respiratory ailment but is attended by his seemingly doting wife. While investigating, Rosemary learns that she has been unfairly sacked from the university by her ex-boss/ex-boyfriend.

Laura and Rosemary hit it off, and soon they are pooling skills and experience to investigate the horticulture mystery. Laura is an avid gardener and was a police woman before she retired to raise a family, and Rosemary knows a lot about plants and their diseases. When Sam dies from an apparent heart attack, and Daniel begins to improve once he is hospitalized away from the estate, Rosemary and Laura determine to find out what's going on, and why the creepy housekeeper, Mrs. Potts, seems so familiar.

I enjoy the English cozy style of story telling, and like this version's integration of two modern and engaging women and the gardening theme. The beautiful setting at the Winterbourne estate with the beautiful plants and trees make this episode and series perfect for winter movie watching. If you'd like a little escapism, while waiting for seed catalogs to appear and early spring gardening tasks to do, I recommend this series. I found it on DVD in our local library and available through online retailers. I also found the synopsis of all episodes on Wikipedia, and filming locations on Wikimedia (more to keep you busy)!

The sedge has withered from the lake

And no bird sings.

By John Keats (1795–1821), from La Belle Dame Sans Merci

Rambles in Sunny Seattle

It was difficult to leave the cool misty land of my youth, with all its wonderful memories, hardy people, and natural beauty. My husband and I had a great time reconnecting with family and celebrating life together. On the way home from Alaska, we stopped in Seattle for a long-weekend with our wonderful son and daughter-in-law, and Mako the Granddog.

Catching up

Lounging in air conditioned bliss

It's always such a pleasure to see them and spend time together. Their youth, energy, and optimism is invigorating. They are busy making their way in the world, but always make us feel welcome.

Walk on the Duwamish Trail

Garden ideas - terraced border

Garden ideas - masonry work

One favorite activity is taking Mako for long walks in South Park. It's fun to see the neighborhoods, find interesting gardening ideas and plants, and catch up on each other's lives.



Another favorite activity is eating, whether we cook ourselves or go out to eat. Our son has become a wonderful and adventurous cook. This visit he made delicious Shepperd hand pies (with homemade rough puff pastry) served with delicious glazed carrots; rice with pork belly; and eggs-over-easy served on toast. Delicious!

Hudson's restaurant near the morgue

We  also enjoyed pizza from South Town Pie, burgers and fries from Lorretta's Northwestern, and a leisurely big breakfast at Hudson Seattle Restaurant (near the Georgetown Morgue). We celebrated the birthday of our tricenarian daughter-in-law at the wonderful Pomodoro Restaurant with its delicious Spanish-Italian food and welcoming ambiance. Someone shouted "Forever 21" when the flaming tiramasu was brought out (an excellent wish for everyone)!

Warm ambience at Pomodoro Restaurant

Flaming tiramasu and forever 21

Media update

One of the highlights of our short visit was a Saturday morning session of Bossa Nova jazz with Marco de Carvalho & Friends at C & P Coffee in West Seattle. Carvalho is a Brazilian musician from Rio de Janeiro, and graduate of the Music Conservatory in Rio de Janeiro. He and his talented band of musicians played for a couple of hours to a loyal crowd. We listened over coffee drinks and donuts.

Marco de Carvalho & Friends at C & P Coffee

Saturday morning

Coffee at C & P Coffee

Homey atmosphere at C & P Coffee

Sunday morning came too quickly, and we were soon on the plane zipping back to the San Francisco Bay Area. The visit was the perfect ending to a wonderful trip, filled with natural beauty, family, and birthday celebrations (or uncelebrations)!

The end to a wonderful trip

Summer on the Iron Horse Trail

What a difference a few months makes! When I last reported on the Iron Horse Trail, everything was green. Mount Diablo and the surrounding hills were green, the railroad bed was green, and the empty back lots lining the Trail were green. Trees had leafed out and wildflowers proliferated. Seven months of drought-busting rains turned San Ramon into an emerald green paradise (see Spring on the Iron Horse Trail).

Shady rest stop on the Iron Horse Trail

Mile 18.25 heading south from Concord to Dublin

Fast forward a few months and many days of 90- to 100-degree weather. San Ramon has been transformed back into the tawny paradise characteristic of the California landscape. The hills are once again golden brown with scattered oak trees. I've been getting my exercise swimming laps at the nearby San Ramon Olympic Pool and Aquatics Center, or taking quick walks around the Bishop Ranch lakes in the late afternoon, when the blissful marine breeze travels through the 580 corridor, and up the 680.

Countryside turns brown near Bishop Ranch (with California hills in the distance)

I finally made my way over to the Iron Horse Trail for a walk, and to see what impact the high heat is having. The Iron Horse Trail runs through San Ramon near Bishop Ranch, and provides a vital transportation and recreational corridor. I found a lot of tawny grasses, and hot sun, so kept to the Trail edge and explored some of the shady side trails and lingered under the big oak. I found a lot of tiny wildflowers amidst the grasses, and some interesting oak galls and plant diseases.

Shady side trail through pines	Oak Apple Galls
Another type of Gall	Morning Glory

HTML Tables

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)

Holiday Cooking – Cardamom

This month I’m continuing my research into the plants that flavor my holiday baking. Today I’m learning about cardamom, which is used to flavor Scandinavian baked goods; sausages and ground meats; and Indian curry dishes. My burning question – how did a main ingredient in Indian curries end up in Swedish cookies and breads?

Botanical illustration of Elettaria cardamomum from Koehler's Medicinal Plants.
Published before 1923 and public domain in the United States.

Elettaria cardamomum is in the Zingiberaceae family (ginger plants), and is native to India, Ceylon, Malay Peninsula, and Sumatra. Cardamom grows wild in shady forests, and loves wet feet. It thrives at an altitude of 2600 – 5000 feet (800 – 1500 meters), and at a uniform temperature of 72 F. (22 C.). According to Jan-Öjvind Swahn, ancient Vedic texts mention cardamom as medicine 1000 years before Christ; Greeks and Romans used it for cooking and medicine; Vikings encountered it in Constantinople in the eleventh century and introduced it to Scandinavia. Cardamom was recorded north of the Alps in the thirteenth century, and in botanical literature during the Renaissance. It was blended with coffee beans by the Arabs, and chewed with betel leaves in Southeast Asia.

The cardamom plants is a deciduous perennial that grow to 10 feet high, with leaves to 2 ½ feet long and 3 ½ inches wide. The inflorescence grows up to 2 feet long; and bears many greenish-white blossoms, each with a wide lip in the middle. The fruit is an oval capsule, containing three chambers, each bearing up to 20 aromatic seeds. Propagation is by division of rhizomes, and by seeds; plants succeed in moist, shady places in warm climates. In cultivation, the plants require quite a bit of care, but are productive over a 10-15 year period. They are susceptible to weather conditions, insect damage, and plant diseases, such as the mosaic viruses. The cardamom capsules are harvested, dried, and distributed as whole seeds or ground.

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)

Cedar-Apple Rust (Basidiomycetes)

Cedar-apple rust (Gymnosporangium juniperi-virginianae) is caused by a fungus in the Basidiomycota phylum. The disease life cycle involves two types of trees – apple or crab apple (Malus genus), and red-cedar or juniper (Juniperus genus). The apple or crab apple is an aecial host (the host plant on which heteroecious rust fungus produces aecia and pycnia); and the red-cedar or juniper is the telial host (the host plant on which a heteroecious rust fungus produces telia, and sometimes uredinia).



Telial gall of cedar-apple rust on cedar, with spore horns withered after spore germination. Photograph courtesy C. W. Mims from the APS slide collection, Introduction to Smut and Rust Fungi.

Some vocabulary, because this is complex:

• Aecia – the fruiting body of a rust fungus in which the first dikaryotic spores (aeciospores) are produced. Aeciospores infect the alternate host (in this case, the juniper). Dikaryotic spores have two sexually compatible haploid nuclei per cell and divide simultaneously.
• Pycnia – the flask-shaped haploid fruiting body of a rust fungus bearing receptive hyphae and sexual spores.
• Telia – survival spore, or teliospores, produced by rust fungus in which germination occurs.
• Uredinia – asexual dikaryotic, often rust colored spores, capable of infecting the host species on which it is produced.

Basidiospores form on the germinating teliospores of a red-cedar or juniper gall. The basidiospores infect apple leaves to produce pycnia. Aeciospores are produced in blisterlike aecia on the lower surface of the apple leave. The aeciospores infect junipers only (not the apple tree). The disease is monocyclic, meaning one life cycle per growing season (versus polycyclic which is even more complicated)!

For management tips, see the Integrated Pest Management (IPM) site. Prevention is the best strategy – remove junipers that are within five miles of apple orchards, and avoid planting junipers near apple trees in the landscape (although damage is not extensive to apple trees, except in very wet years). Because the disease is monocyclic, you can effectively apply fungicide applications timed to protect the apple trees during the time when basidiospores are released. Plant apple and crabapple trees that are disease resistant.

Black Spot of Rose (Ascomycetes)

Black Spot of Rose (Diplocarbon rosae) is caused by a fungus in the Ascomycetes phylum. It is frequently found on rose bush leaves here in the Bay Area, especially during the winter or in the fog belt. Symptoms include black spots and yellowing on the upper surface of leaves. The fungus produces ethylene, which induces chlorosis (yellowing) of the leaves, and eventually abscission (leaf drop). Ethylene is a growth regulator that affects leaf drop, fruit ripening, and plant senescence; and can cause vascular wilt diseases. The black spots may have a feathery margin and may include fruiting bodies (best seen with a hand lens). Inside the fruiting body, microscopic sexual spores called ascospores are produced in sacs called ascus (pl. asci), and released upon maturity.

The fungus requires water to reproduce and grow, and can survive in fallen leaves and infected stems. Overhead sprinklers may keep leaves wet for long periods of time, and may splash the fungus from infected to uninfected plant material.

Black Spot of Rose, with chlorosis. Photo courtesy of C. Ash, available by APSnet via License to Copy.

For management tips, see the Integrated Pest Management (IPM) site. Prevention is the best solution – plant resistant rose bushes in a sunny location with plenty of room for air circulation; remove fallen leaves and infected plant parts; and do not let moisture stay on the leaves for more than seven hours. This means you should avoid watering with overhead sprinklers; and, if you spray the leaves to remove dirt or pests, do so early in the day so the leaves have a chance to dry. You can manage black spots on leaves using a combination of bicarbonate of soda and horticultural oil, or using Neem oil or fungicides.

Plant Diseases – Fungi

Fungi are the last category of plant diseases in our year-long study of plant diseases that can affect our plants in the San Francisco Bay Area. Other categories have included bacteria, plant parasites, water molds, nematodes, and viruses. Our resources have included information from my plant diseases course at Merritt College in Fall 2012, Essential Plant Pathology, and Five Kingdoms. As with other categories, many fungi are beneficial for the ecosystem, but others can cause disease or damage.

Fungi are incapable of producing their own food, so seek nourishment from dead organic matter or living plants. Fungi are composed of filaments, which excrete enzymes that decompose organic matter so that the cells can absorb the nutrients. An individual filament is a hypha (hyphae), and the mass of filaments is the mycelium. Some parasitic fungi produce toxins that help them invade a host; others produce mycotoxins that are poisonous, causing illness or death to animals or humans who ingest them.

White mycelia of a wood decay fungi - great on the forest floor, on your roof - not so much.

Hypha cells contain mitochondria, nuclei, and other organelles. Nuclei are haploid (one set of chromosomes). Cell walls are made of chitin (similar to the shells of crabs and exoskeleton of insects), rather than cellulose (the main component of plant cell walls), making fungi more closely related to animals than plants. Additionally, fungi use glycogen for food storage (similar to animals), rather than starch (as plants do). The hypha may grow into survival structures (called fruiting bodies) that produce spores, such as puff balls, mushroom, and conks. Fungi reproduce by sexual and asexual spores. Sexual spores ensure genetic diversity and adaptability; asexual spores are clones that ensure survivability.

The four major phyla of true fungi are Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota. The phyla are called true fungi to distinguish them from organisms that were formerly classified as fungi, such as the water molds (or Oomycetes). The first two groups are especially important for plant diseases:

• Ascomycetes – bread and beer yeasts, morel mushrooms, and plant parasites that cause common diseases such as Chestnut blight, apple scab, leaf spots, Dutch Elm disease, post-harvest diseases, powdery mildews, and vascular wilts
• Basidiomycetes – root rots, rust fungi, smut fungi, wood decay fungi, turf grass diseases, and Sclerotium spp. blight

All parts of a plant—roots, stems, vascular system, trunks, flowers, and leaves—are susceptible to fungal diseases.

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.

Spiral Nematodes

Nematodes can be a threat to turfgrass, and have been found in golf courses, parks, and lawns in the San Francisco Bay Area. Spiral nematodes (Helicotylenchus spp.) are one of many nematode species that are found in the soil. Spiral nematodes have a wide host range, and do not cause excessive damage, but they can reduce the vigor of plants in a monoculture host like turf grass. Mature spiral nematodes are up to 1.2 mm long, and are so named because they curl up into a spiral when dead or relaxed. They are ectoparasites, meaning they feed outside the cell, although some may act as partial endoparasites—inducing growth of a food cell in which they bury their head to feed for long periods of time, before moving on to create a new food cell. These food cells do not grow like a gall, but the cell composition does change.

Spiral nematodes are all females, reproduce without mating, and lay individual eggs in the soil (unlike the root rot nematode that lays an egg mass). The first molt occurs within the egg (J1). If moisture is present in the soil when the egg hatches (J2), the nematode is motile and works its way to a plant root where it can feed. The nematode undergoes three more molts (J3 and J4), before becoming a mature adult. Populations are highest in late summer and early fall and lowest in spring when cold temperatures inhibit reproduction.

Spiral nematode turf damage is associated with bluegrass and Bermuda grass. Above ground symptoms include stunting, reduced plant vigor, yellowing or brown patches in the turf, and areas that succumb to weeds. There is typically a “hot spot” or dead zone, which is heavily infested. These symptoms can have other causes, so soil analysis is required to diagnose the problem: http://youtu.be/taW-VM-4IRw

For management tips, see the Integrated Pest Management(IPM) site. Prevention is the best approach, but strategies like crop rotation are difficult for turf. Chemical treatments exist, but some of them cause damage to turf, or must be repeated, since they also kill beneficial organisms that keep other diseases at bay. See UC IPM Pest Management Guidelines: Turfgrass (page 72) for additional information.

Root Rot Nematodes

Root-rot nematodes are from the genus Meloidogyne, and thrive in hot climates with short winters. They are not host-specific, and infect the roots of a wide host range, including flowers and vegetable crops (tomato, green pepper, corn, grains, and so forth). They are sedentary endoparasites—living and feeding from within their hosts.

Females lay their eggs in a gelatinous mass on a root gall surface; ensuring a protective, moist environment in which the eggs develop. The first molt occurs within the egg (J1 stage). After the eggs hatch, the second-stage juveniles (J2) are motile. They leave the egg; penetrate the root with their stylets, just behind the root cap; and secrete a liquid that stimulates growth hormones in the cells, causing them to divide and swell. This forms root galls that become permanent feeding sites. After molting through two more juvenile stages, (J3 and J4), reproductively mature females lay a new batch of eggs. This lifecycle occurs over the course of several weeks, so, in the right environmental conditions, plants can become infected very quickly. If the galls become separated from the roots, the eggs can exist in the soil for years, until the right conditions and a suitable host are available.

Galls on carrot from root-rot nematode. Photo by Claudia Nischwitz.
Copyright, ASPnet.

Above ground, plants exhibit symptoms that are similar to any disease that harms the root system, including stunted growth, wilting, and yellowed leaves. Reduced crop yield also results. To help with diagnosis, it is necessary to have the soil analyzed and to check the roots for galls, if at all possible.

For management tips, see the Integrated Pest Management (IPM) site. Since the eggs can remain in the soil for years, management is difficult. The solution is prevention – using resistant plant varieties; rotating crops so the nematodes cannot continue their lifecycles from season to season; leaving soil fallow periodically; amending the soil to keep it healthy; planting when nematodes are less active; and keeping infected plants or material from contaminating uninfected areas. Soil solarization, the process of heating the top 8 - 12 inches of the soil, can temporarily reduce the nematode population. Currently no chemical or soil fumigants are available to the home gardener.

Plant Diseases - Nematodes

This time I’m researching nematodes, which are non-segmented round worms found in soil, water, and extreme environments such as deserts and ice fields. A few can be seen with the naked eye, but most are tiny and require magnification. For resources I’m using Essential Plant Pathology, information from my plant diseases course at Merritt College in Fall 2012, and Five Kingdoms. Keep in mind that most nematodes are beneficial – they aerate the soil, consume detritus, feed on bacteria and other small life forms, and circulate organic and mineral soil components. Others cause considerable damage to crops, turf, and plants in the landscape. Nematodes can be found in the San Francisco Bay Area.

Nematodes are categorized as Eukarya in the Animalia kingdom. About 10% of all nematodes are plant parasites, and require a living host (obligate parasites). They are aquatic and typically live, feed, and move in the soil. They use a specialized feeding structure—called a stylet—to penetrate plant tissue, probe, secrete proteins and polysaccharides, and ingest cellular contents. Most nematodes are migratory and move from cell to cell to feed (ectoparasites). Others are sedentary and remain embedded in a plant throughout their lifecycles (endoparasites); some endoparasites induce formation of specialized feeding sites, such as galls, where they live and feed. A few do not fit either of these categories.

The female nematode lays hundreds of hardy eggs (some species do not require male fertilization of the eggs). The eggs can exist in soil for years or decades, until the right environmental conditions exist for them to infect a plant. Their life cycle includes four juvenile stages. Nematodes molt, shedding the outside cuticle and part of the lining of the stylet, from stage to stage as they grow. Juveniles look like miniature adults through all stages (they do not undergo a metamorphosis from stage to stage).

Take a look at several nematodes; of special interest (1) views of the stylet at 57, 107, and 145 seconds, (2) a root rot nematode at 159 seconds, and (3) a needle nematode at 202 seconds: http://youtu.be/Qf8oGjqyXFc

Clear Lake Plant Diseases

I’m afraid my Plant Diseases class from Merritt College in Oakland has despoiled me – I am always on the lookout for plant diseases! End-of-summer is a great time to spot them, as many plants have spent their reserves on reproduction, and are more vulnerable to attack. Here are some of the diseases I spotted in Clear Lake; oaks seem especially hard hit.



Sudden Oak Death –  I wasn't close enough for direct inspection, but this looks like SOD from afar; caused by the water mold, Phytophthora ramorum. 

Oak Gall – these little "nipples" are galls caused by asexual reproduction by the oak gall wasp.
When the wasp lays its eggs, hormones kick off a type of genetic engineering to create the perfect nursery (the gall).

Oak Apple Gall – this "strange fruit" indicates sexual reproduction by the oak gall wasp.

Tent Caterpillar – we found these gauzy structures all over foliage.
The residents had already moved on.

In many cases, these diseases do not cause permanent damage. An organism is simply taking advantage of a situation, and working through its own life cycle. After the class, seeing plant disease is not necessarily alarming. Plants in nature are rarely perfect; instead, they are teaming with all sorts of life forms. Learning to enjoy the whole ecosystem of a plant, both good and bad, can add to the enjoyment of nature as well as the garden. And raising your tolerance for imperfection can lower the need to combat the imperfect with pesticides.

Grape Leafroll Associated Virus (GLRaV)

The Grape Leafroll Associated Virus (GLRaV) colonizes the phloem in the plant’s vascular system, cutting off distribution of nutrients to leaves, shoots and fruit. This delays maturity of the grapes, reduces fruit yield, and lowers accumulation of sugars (the Brix), affecting wine quality. Symptoms include reduced vigor, yellowing of the leaf margin and veins, and the characteristic under curl of the leaves. The symptoms are more noticeable in red varieties than white varieties. Symptoms are typically most evident in mid-August, but, in some cases, there are no visible symptoms. The virus is a group of ten strains, identified as GLRaV- followed by a number. Take a look at the symptoms on a variety of grape types:

http://youtu.be/Es41Tdgd9L0

According to the brochure, "Grapevine Leafroll – an Increasing Problem in the Finger Lakes, the US and the World", published by the Cornell University Cooperative Extension, this is a worldwide problem threatening many grape-growing regions. The virus has been found in both eastern and western United States grape growing regions, including California. Even the San Francisco Bay Area backyard gardener may encounter the virus.

The virus spreads through infected bud wood cuttings and graft unions. If the grafts are not clean, infected starter plants can be distributed unwittingly around the globe. European researchers discovered the virus is also spread through insect vector - Pseudococcus mealy bugs (grape, obscure, and longtailed) and soft scales (Parthenolecanium corni and Pulvinaria innumerabilis). The vectors hitch hike on farm workers, equipment, and plant debris, and can quickly spread from an infected field to a neighboring clean field.

Since vines cannot be cured once they are infected, the best strategy is preventing infection. Plant only certified clean root stock. Inspect the plants routinely, looking for symptoms and signs. Manage mealy bugs and soft scales using organic methods. Once infection is detected, replace the infected vines with certified clean stock at once. Testing is available for several strains of the Grape Leafroll associated viruses; see the U.C. Davis Integrated Pest Management (IPM) site for information.

Tomato Leaf Curl Virus (TYLCV)

The Tomato Leaf Curl Virus (TYLCV) infects tomato plants, and sometimes other hosts in the Solanaceace family (nightshade and jimsonweed). Symptoms include small leaves that curl upward, crumpling, and yellowing on the margins and veins. Flowers fall off the plant, reducing the crop. The plants themselves look stunted—due to shortened internodes—giving the plant a bushy appearance. Other hosts may exhibit minimal symptoms, or no symptoms.

According to the Tomato Yellow Leaf Curl brochure, published by the University of California Agriculture and Natural Resources Statewide IPM Program, the disease was first observed in Israel in the 1940s; spread to the Caribbean islands and southeastern United States in the 1990s; moved to northern Mexico, Texas, and Arizona in the 2005-2006; and was found in a greenhouse in Imperial County in 2007. The disease thrives in tropical and subtropical environments, and in Mediterranean climates.

Upward leaf curling and reduction in internode length in tomato infected with TYLCV.
Copyright, ASPnet

Bemisia whiteflies and some leafhoppers are the main vectors for the disease. After feeding on an infected plant, the insect is infected for its lifetime and spreads the virus by feeding on uninfected plants. When tomato plant hosts are not available, it is thought that the virus can exist in weed hosts. The virus is not transmitted in seeds or mechanically (by touch), but can be transmitted if infected plants are transported to uninfected areas. If the virus spreads to California, it could have a significant negative impact for commercial tomato growers, and for backyard tomato enthusiast

For management tips, see the Integrated Pest Management (IPM) site. In general, recommendations include planting TYLCV-resistant varieties, maintaining “tomato-free” periods when there is no host, eliminating weeds that could be hosts during tomato-free periods, removing diseased plants, avoiding transport of infected plants to uninfected areas, and managing whiteflies. TYLCV symptoms resemble symptoms for other diseases, but accurate tests are available to identify the virus.