Washington State University Extension

Garden Tips

Archive for June 2011


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

It seems like the question on almost everyone’s mind this past week is what’s wrong with the area sycamore trees? The problem is sycamore anthracnose (a.k.a. sycamore blight). I talked briefly about this fungus disease two weeks ago, but with so many frantic sycamore owners I think we need to talk more in-depth about the current sycamore blight epidemic.

Most of the older sycamores in our area are not resistant to anthracnose and have been infected numerous times over the years when cool (50 to 60 degrees F), wet spring weather has prevailed. We typically don’t experience these spring conditions in successive years like we have last year and this year. Our trees have been dealt a “double whammy,” with this springs’s infection being severe.

Sycamore anthracnose is called a “leaf and twig blight” but it should be called a twig, bud, shoot, and leaf blight because the fungus can attack all of these parts of new spring growth. According to plant pathologists at Clemson University there are four distinct phases of the disease:

1. Twig blight occurs before the leaves emerge and kills the smaller twigs.

2. Bud blight occurs when cankers girdle the twigs, preventing developing buds from getting water and nutrients.

3. Shoot blight occurs when new shoots and leaves suddenly dieback because of girdling cankers.

4. Leaf blight occurs after the leaves have fully developed is characterized by angular brown lesions associated with the leaf veins. Infected younger leaves will just look brown and crinkled and drop from the tree.

Will the trees die? Probably not. Healthy, well cared for sycamores that haven’t been topped can usually withstand repeated defoliation several times in one season. The presence of many large older sycamores in the area shows that they can survive. However, severe successive infections will weaken trees and they could die.

Can the disease be controlled? You can help manage the disease by raking up and disposing (not composting) of all fallen leaves and twigs. They serve as a source of fungus spores for next year. Cankers on twigs and branches also produce spores. Where practical, prune these out. Keep the tree in good health, providing adequate water during the summer, as well as during the fall and winter. Trees that have been badly infected this spring should be fertilized now to encourage new growth.

There are numerous fungicide sprays recommended for control of the disease, but these are applied in early spring when the buds begin to swell and the bud caps are starting to break and then again 10 to 14 days later. If your sycamore is taller than ten feet, you won’t be able to apply the spray materials effectively over the entire tree and should contract with a commercial pesticide applicator/arborist for treatment.

On very large trees, some arborists may recommend systemic fungicide injections in the trunk of the tree. The injected chemical is moved via the tree’s water conducting vascular tissues throughout the tree and will protect against early spring infections. There are several products available only to licensed commercial pesticide applicators/arborists. One of these is Arbotect 20-S. Arbotect 20-S has given excellent control over multiple field-trial seasons. According to the label Arbotect 20-S is applied “after the tree has fully leafed out (post infection) through late summer or early fall. Treatments will aid in control of anthracnose for up to three growing seasons.”

There’s no way to know if we’ll have a long cool, wet spring again next year, but if you have a particularly valuable sycamore tree you may want to consider having it injected with Arbotect 20-S. Otherwise, let’s hope for a warmer, drier spring in 2012!

Published: 6/18/2011 9:08 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Longtime gardeners have learned their tips and tricks by trial and error and from other gardeners. Earlier in the year I gave novice gardeners a few tips on growing great veggies. Now, here’s some helpful tips on growing great tomatoes.

Stake or Cage Tomatoes? Tomatoes are the favorite crop of home gardeners. What varieties did you pick from the staggering number of choices available at garden stores? Do the ones you planted have determinant of indeterminant growth habits?

Determinant tomatoes are more compact with growth that’s easier to contain. They grow to a predictable height and then flower and set their fruit over a relatively short period of time. The smaller “bush” types that grow three feet tall or less usually don’t need any extra support in the garden. However, the taller determinant varieties may benefit from the support of wire cages, especially with the “occasional” windy days encountered here.

As “vines,” indeterminant tomatoes keep growing and growing until frost kills them in the fall. They flower and set fruit over an extended period. You can allow the vines to sprawl along the ground, but this makes them difficult to tend and takes up valuable garden space. Caged or staked upright, indeterminant tomatoes will take up less space. I favor wire cages because they require less work.

You can make your own cage out of concrete reinforcing wire or purchase a sturdy one from the garden store. For determinant tomatoes you should have a cage that’s at least 4 to 5 feet tall and 2 feet wide. As the tomatoes grow, you simply redirect stems that escape the cage, placing them back inside. If you anticipate heavy vines or have a windy garden spot, it’s a good idea to secure the cage to a couple of stakes hammered into the ground.

Even Soil Moisture is a Key to Tomato Success

One key to success with tomatoes is maintaining even soil moisture. This is best achieved by checking the soil moisture regularly and watering when needed. A thin layer of mulch, such as grass clippings or compost , will help conserve soil moisture and moderate soil temperatures. Close attention to soil moisture will help avoid blossom end rot and fruit cracking, both common abiotic disorders of tomatoes related to soil moisture.

When Tomatoes Don’t Produce Any Fruit

Tomatoes are self-fertile and depend primarily on the vibration of wind for pollination to occur, but they’re notoriously finicky about day and night temperatures, as well as humidity, watering, and fertility. Most tomatoes set best when temperatures are between 70 and 90 degrees and will drop their blossoms without setting fruit if:

1. Night temperatures are too low – below 55 degrees F for four or more nights

2. Night temperatures that are too high – above 75 degrees F

3. Daytime temperatures are too high – above 90 degrees F

4. Water stress and excess soil moisture

5. To much nitrogen in the soil or too little

6. Low humidity, below 40 per cent. You may be able improve blossom set when the weather is hot (between 90 to 100 degrees) and dry (below 40 per cent humidity) by spraying the blossoms with water twice during the hottest part of the day.

Find out from other gardeners in your area what tomato varieties produce the best for them. They can also tell you their “tips and tricks” for growing great tomatoes

Published: 6/11/2011 9:06 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Woe is me! The cool weather has slowed down our gardening season so much that I’ve almost abandoned hope that I’ll get ripe tomatoes before the end of summer. Slow growth isn’t the only problem that the abnormally cool, moist weather has been causing. These conditions have been perfect for fungal plant diseases on certain garden and landscape plants.

When it comes to fungal plant diseases, local gardeners can usually consider themselves lucky. Our typically dry climate isn’t conducive to an abundance of troublesome fungal diseases, but this spring’s cool temperatures and repeated rains have created the perfect conditions for trouble.

Sycamore anthracnose is a fungal disease which attacks sycamores. Look around at many of the older area sycamores. They look like they’re slow to leaf out this spring, but the problem is anthracnose which attacked the leaves as they first began to emerge. Severe infections of sycamore anthracnose occur if the weather is cool (below 55 degrees) and moist when the leaves start to emerge. Years when our spring weather is warmer (above 60 degrees) or drier, anthracnose is not a problem.

By the time anthracnose is noticed, it’s too late to apply fungicide sprays that will protect the emerging leaves. Fungicides must be applied just as the buds begin to swell and open. Repeat applications are needed if the weather stays cool and wet. Many sycamores look pretty sick right now, but most will survive by producing a second set of leaves. Hopefully, this new set of leaves won’t also become infected, but they can be protected with fungicide sprays.

While anthracnose seldom kills sycamores, it can render them pretty ugly after repeated attacks. Fertilizing affected trees to encourage new growth is recommended. If you’re considering planting a sycamore, select one of the anthracnose resistant cultivars, Bloodgood or Liberty.

Powdery mildew is a group of diseases identified by whitish powdery spots or patches on the surface of green leaves and stems. Young, succulent tissues of susceptible plants are most prone to infection. Badly infected growth usually becomes stunted and distorted.

The different powdery mildews look very similar, but only attack specific host plants. Rose powdery mildew is different from the powdery mildew that attacks grapes, and the one that attacks lilacs, and the one that attacks apples and the one that attacks turf.

Unlike many other fungal plant diseases, powdery mildews don’t need free water on leaf surfaces for infection to occur. Instead, they’re favored by cool temperatures, high humidity, and lower light intensity. Our weather this spring has been very conducive to powdery mildew infections. Powdery mildew can also be a problem when gardeners create favorable conditions by crowding plants and causing poor air circulation, situating plants in damp shady areas, or irrigating lightly frequently.

Problems with powdery mildew can be mitigated by planting mildew resistant varieties, avoiding crowded plant growth, properly pruning to remove excess growth, and planting in full sun. There are dormant fungicides available for control of powdery mildew on woody plants that should be applied just before growth begins in the spring. New growth can be protected with regular applications of fungicide. So far, I’ve been seeing powdery mildew on crab apples, ornamental pears, apples, and roses.

It’s a good idea to check your garden for signs of insect pests and plant diseases, such as powdery mildew. This year our plants need all the tender loving care that we can provide. How does your garden grow?

Published: 6/4/2011 9:00 AM



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