Cedrus blights and its control

What is the disease causing needle drop, and even killing in some cases, Cedrus trees in our area? Is there a fungicide recommended to help control the disease, and if so, what timing is recommended?

I can’t be absolutely certain what the cause might be, but taking a look at some Northwest integrated pest management resources could provide ideas on the likely culprits.

Oregon State University’s IPM site mentions Kabatina and Sirococcus conigenus.

Here is what the print companion to the website (2008 Pacific Northwest Plant Diseases Management Handbook) says about Cedar needle blight:
“The fungi Sirococcus conigenus and Kabatina sp. have been associated with blighted needles of Atlas and Deodara cedars in both Oregon and Washington; however, Sirococcus is found most often. More of a problem in years with prolonged wet, cool springs. Infection is on or adjacent to needle bases on new shoots. The disease cycle is completed in 1 year, although spore dispersal from dead parts may continue (…) 10 months. The fungus overwinters in dead shoots. Conidia are dispersed by splashing water in spring and summer. (…) Temperatures of 60 to 70 F are most favorable for disease development.(…) Cultural control: Remove and destroy blight plant material and debris that is found under trees or caught in limbs. Chemical control: No chemicals are specifically registered for this disease on cedar.” (The full information is available in the link above.)

Washington State University in Puyallup has a document indexing plant hosts of various pathogens, and for Cedrus they list Sirococcus species as well as Phomopsis.

There are discussions on the topic of Cedrus blights at University of British Columbia Botanical Garden’s online forum which mention tip blight sometimes appearing in tandem with borers or mites.

Dark leaf spots on Photinia

I have a 75-foot long Photinia x fraseri hedge that is losing leaves. The leaves have dark spots on them. I wonder if it is a mold or fungus. I have not removed trimmings in previous years and air circulation has not been optimum. Some plants have lost almost all their leaves but there is new growth there too. The hedge is about 4 feet tall and is about 20 years old. I was thinking it could use some sort of fertilizer and mulch after I clear out all the old prunings. Any suggestions?

There are a few possible reasons your hedge is dropping leaves. In my own experience with Photinia, they were constantly dropping leaves throughout the year. Some of the leaves had dark spots, but some were just older foliage, reflecting this plant’s tendency to shed older leaves. According to Washington State University’s Landscape Plant Problems (2000), spots on Photinia leaves can be caused by a fungus called Entomosporium mespili, but they can also occur in fall and winter with no disease present. The fungal spots tend to have purple black edges and ash grey centers. Virginia Cooperative Extension has descriptions and images of this fungal disease.

There is another leaf spot of unknown origin, simply called ‘physiological leaf spot,’ described by Washington State University Extension as follows:
“Physiological leaf spot occurs on Photinia in western Washington. The symptoms resemble those of early fungal leaf spot infections. Small red to purple spots appear on the leaves, but do not develop the dark centers characteristic of fungal leaf spot infections. This problem is more common than fungal leaf spot. It causes little damage to plants, although some leaf drop may occur. While the cause of this problem is unknown, leaf spotting appears to be more severe on plants in low-lying or shady areas. Cold temperatures appear to be involved.”

If you want to know for certain what the spots are, you should bring samples to your local county extension agent so that they can identify the cause.

Improving air circulation and removing and disposing of all fallen leaves are always good garden hygiene practices. Avoid getting the leaves wet when you are watering the garden, and avoid summer pruning. The American Horticultural Society book Pruning & Training (DK Publishing, 1996) recommends pruning in spring, though hedges will need to be clipped two or three times a year.

I don’t recommend adding fertilizer, as it could cause your hedge to grow more quickly than you want to prune it. Mulching lightly with compost would probably be beneficial. In general, Photinia is a tough and vigorous plant, and the leaf spots are unlikely to cause its demise.

rose bush buds won’t open

I have several roses that bloom just fine but one particular rose bush produces buds that never open. Why is this happening?

It is possible that your rose has a problem with insects like thrips, which can cause buds not to open. If you see tunneling in the buds (holes in the petals), it could be caused by beetles. There is also a possibility that a disease is causing the problem. Fungal infections like botrytis blight can result in buds which do not open, but you would probably notice signs of the fungus during warmer temperatures, such as gray-brown fuzzy growth, and blotched petals or drooping buds. The Northwest Center for Alternatives to Pesticides provides information describing various rose problems, and organic solutions.

Here is a description of botrytis blight from University of California, Davis Integrated Pest Management. This is a brief excerpt:
“Botrytis blight, caused by the fungus Botrytis cinerea, is favored by high humidity. Affected plants have spotted flower petals and buds that fail to open, often with woolly gray fungal spores on decaying tissue. Twigs die back and large, diffuse, target-like splotches form on canes. Reduce humidity around plants by modifying irrigation, pruning, and reducing ground cover. Remove and dispose of fallen leaves and petals. Prune out infested canes, buds, and flowers. Botrytis blight is usually a problem only during spring and fall in most of California and during summer along coastal areas when the climate is cool and foggy.”

The Olympia Rose Society also has information on these potential causes of failed buds. Below is their description of thrips:
“Buds do not open, or flowers are deformed. Petals have brownish yellow streaks and small dark spots or bumps. White and pastel roses are particularly susceptible. Thrips (are) tiny orange insects with elongated bodies. Thrips feed at the bases of rosebuds and on the petals of open flowers. They seem to be attracted to light-colored blossoms.”

The Organic Gardener’s Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale Press, 1996) suggests encouraging natural predators of thrips and, if the infestation is severe, spraying weekly with a safer insectidical soap or pyrethrin-based product. This same resource suggests that if your roses have botrytis blight, you will see the buds turn brown and decay instead of opening, and you should pick off and dispose of any diseased buds. They recommend spraying with sulfur once a week during the growing season.

A few things that are always a good idea when growing rose:

make sure there is good air circulation around your plants
don’t water from above the plants (keep the leaves dry)
always clean up around the plants–don’t let leaf debris or any diseased buds lie on the ground under the rose bushes

This (now archived) site has many pictures of rose pests and diseases for you to compare with what you are seeing on your plant. Since I cannot diagnose the problem without seeing the plant, I recommend that you take samples of the affected buds to a Master Gardener Clinic.

Portuguese laurel’s growth and height

My customer says his Portuguese laurel which is now a 5 foot tree won’t be growing any bigger. It is in the shade, but don’t these get 15 feet in height?

SelecTree, the website of the Urban Forest Ecosystems Institute, says that Portugal Laurel (Prunus lusitanica)will do well in sun to partial shade, and may grow up to 35 feet tall, at a rate of two feet a year.

The Sunset Western Garden Book (2001) says that a multi-trunked tree can get as large as 30 feet high and 30 feet wide. Perhaps your customer is expressing wishful thinking, and aspires to grow a shrub rather than a tree. Some people do grow it as a hedge, and clip it frequently to control its size.

on Parrotia persica’s foliage

I have a Parrotia persica tree that has never developed the dramatic purple color that the Sunset Western Garden Book says it should have. Its leaves do turn gold in the fall. What nutrient is it missing? It gets full sun, and is at the top of a sloping area of lawn. I have wondered if the run-off could be leaching something from the soil.

Any suggestions?

According to this article in Fine Gardening online, Parrotia persica only has that purple color as the leaves emerge in spring:
“Reddish-purple when unfolding in spring, the leaves are a lustrous dark green in summer, and yellow to orange or scarlet in fall. Leaves hold their color for a long period. Older branches and trunks develop an exfoliating gray, green, white, and brown color that is a welcome asset in the winter garden. It grows successfully in Zones 4 to 8, tolerates sun and partial shade, and is easy to transplant. Often, vegetatively propagated forms offer more reliable fall color.”

According to Dirr’s Hardy Trees and Shrubs (Timber Press, 1997), there is some variability in the foliage color: “[…]the developing leaves are reddish-purple to bronze, maturing to lustrous dark green.” I don’t believe missing nutrients are the reason you are not seeing dramatic purple color but if you are concerned, you can do a soil test for any imbalances.

Russian sage care

Last year I planted 25 gorgeous Russian sage in 1 1/2 gal pots. They were fabulous last year, but barely came back this year. We had a mild winter here in New Jersey, but even so, I know that is not an issue with that plant as I’ve grown it for years. This year I planted an additional 40 in the same hillside and they are doing phenomenally well. On last year’s plants, some have flowered a tiny bit, but none have come back to the size they were and most are so small, they look like they came from a 6-inch pot! Do you have any thoughts as to what I can do to improve the situation?

Also, although we haven’t had much rain, I am seeing what I’m assuming is mold on several of my plants: trumpet vine, roses, honeysuckle. The zucchini and cucumbers have been totally decimated so there is no fruit. White is covering the leaves and with the veggies, the leaves are crumbling and disintegrating.

There are a few possibilities for the poor showing of your Russian Sage (Perovskia atriplicifolia, now renamed Salvia yangii) plants. However, without knowing more details about the growing conditions, I may be offering you advice that does not help. If the pots you selected to grow your plants in were made of a thin material, there is a chance you did not provide them with enough protection from the winter temperatures. Planting them directly into the ground can help to avoid this, if it’s possible for you to do so in their location.

Depending on the amount of sun and moisture your plants are receiving, poor growth can result. Russian Sage plants like “a well-drained soil and need to
have a warm to hot, sunny position” in the garden. (The Cultivation of Hardy Perennials by Richard Bird published in London by B.T. Batsford Ltd in 1994) If the soil is too wet, root rot can occur.

If they are in the proper cultural environment (lots of sun and well-drained soil), then perhaps they are lacking nourishment. The Plant Care Manual by
Stefan Buczacki (published by Crown Publishers in New York in 1993), suggests feeding your plants with a general purpose fertilizer in mid-spring and in mid-summer.

As for your second question, I believe what you are describing is a case of powdery mildew. It is a fungus that shows itself in times of dry weather. The
main thing you will need to do is destroy all the foliage affected by the mildew. The mildew on infected foliage will spread to new foliage.

Powdery mildew thrives where plants are crowded and there isn’t enough air circulation, so give your plants space, a sunny site, and try watering in the
morning, and watering from beneath the plants (not over the leaves) so they are able to dry off during the course of the day.

Here is a link to the University of California-Davis, Integrated Pest Management
website. You can learn more about this fungus, including host plants, life cycle and management.

Colorado State University Cooperative Extension has some information about powdery mildew as well, including preventative measures and a recipe for making your own baking soda fungicide.

on skeletonizing birds

My pet cockatiel died, and I want to know how long it will take to compost the bird in the soil before I can dig up the skeleton and save it.

I am sorry for the loss of your cockatiel. I think that you can either put the body in the compost or find a way to salvage the skeleton, but not both. Bird bones have hollow cavities, and would likely break down quickly in the soil. Some permaculture discussion groups online suggest not burying birds, but instead storing them in the freezer until there are active ant nests, and then leaving them exposed for the ants to clean. I was not sure if this would work, so I consulted Dennis Paulson, Director Emeritus of the Slater Museum of Natural History at University of Puget Sound in Tacoma.

He says that “putting something as small as a cockatiel in the ground isn’t the best idea, as their smaller bones would probably suffer. Putting it near an ant nest might not be much better, as the ants could carry off those small smaller bones. To make a good skeleton, you need to skin the bird and remove a lot of the bigger muscles (in particular, the flight muscles on the breast) as well as the intestines and other organs from the body cavity.” The Slater Museum of Natural History can skeletonize small birds by using their colony of dermestid beetles that eat all the soft tissues, which is the best way to skeletonize something of that size. The museum accepts donations of specimens, but they may also be willing to assist someone who wants to commemorate their pet bird in this way.

In general, dead animals that are not pets and weigh over fifteen pounds must be collected by Seattle Animal Control, but smaller animals that show no signs of disease may be double-bagged and put in the garbage. King County has similar guidelines. Dead wild birds (particularly crows and jays) that may have been affected by West Nile virus should be reported to the Public Health department at 206-205-4394.

aloes with red foliage

Is there such a thing as a red aloe? Or an aloe that gets that color when planted in a sunny spot? I am especially interested in any that have a reddish tone. Do any of these survive the winter outdoors here in the Pacific Northwest?

The most famously red aloe is Aloe cameronii. In her book Succulent Container Gardens (Timber Press, 2010), Debra Lee Baldwin mentions several species that change color in sun:
“Aloes that turn color when given full sun include Aloe cameronii (crimson), Aloe buhrii (orange), and Aloe taurii and Aloe dorothaea (bright red). Softball-sized Aloe nobilis, which forms dark green rosettes with wedge-shaped leaves toothed with white or yellow prickles, turns shades of red-orange.”
Baldwin’s book also includes “design-oriented plant lists” with guidance about color.

In our climate, most aloe species will need to be sheltered over the winter in a greenhouse. One local nursery, Desert Northwest lists a couple of winter-hardy (or almost-hardy) aloes, but they are not the ones noted for their red foliage.

safety of wooden pallets for vegetable gardens

My son wants to use wooden pallets for a vegetable garden. Is the wood in these pallets safe for contact with food crops?

Pallets (especially those used in international shipping) are very likely to be treated, since wood packaging must now comply with the International Plant Protection Convention’s International Standards for Phytosanitary Measures Guidelines for Regulating Wood Packaging Material in International Trade (ISPM 15). Here is more information from an article by Wendy Priesnitz, editor of Natural Life Magazine:

“Pallets made of raw, untreated wood are not compliant with ISPM 15. To be compliant, they must be debarked and either heat-treated to certain specifications or fumigated with methyl bromide, which affects the central nervous and respiratory systems. Heat-treated pallets bear the initials HT (or sometimes KD for kiln dried) near the IPPC logo. Pallets treated with methyl bromide bear the initials MB. In 2010, a phase-out of the use of methyl bromide began because it is an ozone depleting substance under the Montreal Protocol. However, many pre-2010 pallets are still around and, in fact, are likely to be the ones nearing the end of their useful lives as pallets.

“Older pallets could also have been pressure-treated with chromated copper arsenate (CCA), which has been phased out for many residential uses. The arsenic in CCA-treated wood can be dislodged so that direct contact with wood can lead to exposure, thought to be a problem especially for children, and it can leach into ground water. A 2008 Australian study found that one percent of pallets tested contained CCA. Copper-treated wood varies in color from a very light green to an intense green color, depending upon the amount of chemical impregnated into the wood. However, it ages to a silver color, as does untreated wood, so color is not a reliable indicator, especially with older wood.”

A related question about reusing wooden pallets appeared in the online journal Grist, and their columnist raised the issue of chemical treatment as well as the possibility of the wood having absorbed dangerous bacteria, so I think it’s wise not to use wooden pallets for growing food.

If you want to recycle the pallets, there are places in King County which will accept wooden pallets for reuse, listed on the King County Solid Waste website What Do I Do With…. ?. If you know where the pallets came from, you might ask that business if they will let you return them.

cross-pollination of Asian pears and European pears

I am looking for a European variety of pear tree that cross-pollinates with an Asian pear tree. I thought I’d heard that Bartlett pear trees can pollinate an early blooming Asian pear. Is this right?

The University of California, Davis Fruit & Nut Research Center indicates that European pears may be used for cross-pollination with Asian pear.

Excerpt:
“Pollination: Asian pear varieties are partially self-fruitful but better crops are set where two or more varieties are planted together. In Fresno and Tulare counties, 20th Century or Shinseiki are known to set good crops when planted alone in large one-variety blocks. In areas with cooler temperatures at bloom-time, cross-pollination by European or Asian pear varieties will be necessary. Cross-pollinated fruit with seed tend to be larger and more uniformly round than fruit with few seeds due to inadequate pollination.”

Washington State University’s Tree Fruit site shows which European pears will be compatible pollenizers for specific varieties of Asian pear. (click on the plus sign to expand the information on pollination for pears)
It indicates that Bartlett will work for Chojuro and Nijisseiki.

Washington State University’s Fruit Handbook for Western Washington says “pears and Asian pears are genetically compatible, so they can cross-pollinate just the same as any varieties whose bloom periods overlap. It is, however, important to note some limitations. Asian pears (…) tend to bloom earlier as a group; furthermore, not all European pears are suitable pollenizers. Conference is a good early blooming pear that can pollinate Asian pears in most years (…) Pear flowers are not particularly attractive to bees, so for good pollination when growing pears and Asian pears, try to minimize the availability of other flowers (eg., dandelions) when pears are in bloom.”