Yard & Garden Line News Volume 2 Number 2                                                              February 1, 2000

Features this issue: Caring for Valentine Flowers Alternatives to Roses for Valentine's Day Understanding Amaryllis Start Onion Seeds Indoors Order Oriental Vegetable Seeds Two New Blueberries for Minnesota Grow a Little Love in Your Garden Pavement Ants in Homes During Winter Making an Accurate Plant Disease Diagnosis, Part 2 Getting To Know Your Fungicides: Lime-Sulfur Editorial Notes

Caring for Valentine Flowers
Deborah Brown, Extension Horticulturist

Cut flowers. Photo credit: Deb Brown

Flowers are such a special treat in the middle of winter you really want to make them last as long as possible. Follow these easy tips to wring extra days of enjoyment from those beautiful Valentine blooms:
* Your vase must be immaculately clean. Use a bottle brush to scrub the inside, or fill it with water and drop a foaming denture cleaner in it overnight to remove dried residue.
* Dissolve a packet of floral preservative in warm water, according to directions.
* Strip off any foliage that will be under water; left intact, it is likely to break down and foul the water.
* Recut the stems at an angle, so they won't rest squarely on the bottom of the vase. Use a sharp knife rather than a scissors that might compress them. Cut the stems under running water to prevent air blockage of the freshly cut tissue.
* Place your flowers in a cool place, out of direct sunlight, if possible. When you're not around to appreciate them, put them in the basement or a cool hallway. Except for orchids, the cooler you keep cutflowers (without freezing, of course) the longer they'll last.

Alternatives to Roses for Valentine's Day
Deborah Brown, Extension Horticulturist

Cyclamen.

Paphiopedalum, a tropical ladyslipper. Photos: Deb Brown

It's not too early to think about Valentine's Day flowers. If you're planning to send the traditional red roses, the sooner you order them, the better. But be aware; the laws of supply and demand mean they'll be rather pricey at holiday time.

Consider some of the alternatives; other cutflowers, flowering potted plants, and for those of you with a truly practical bent, tropical houseplants. A foliage plant which can be dressed up for the occasion with foil, ribbons, and a valentine ornament, will last for years in a home or office, so long as your choice doesn't demand terribly bright light.

If you're less concerned with the plant's longevity, you may opt for one with showy flowers, instead. You'll find azaleas, begonias, chrysanthemums, kalanchoes, Persian violets, and exotic kangaroo paws among those expected to bloom for several weeks. Hibiscus plants blossom indoors under bright light, then stop until they're put outside for the summer. And newer African violet hybrids bloom off and on, year-round.

Besides roses, there are dozens of different cutflowers available, from cheery spring tulips, daffodils, and iris to exotic anthuriums, heliconias, and birds-of-paradise. You'll find graceful spider mums, stems of sweet-scented lilies, sprays of delicate orchids, and spicy carnations. Old-fashioned mixed bouquets have become very popular in recent years.

But when all is said and done, remember there's something very romantic about one perfect rose. You needn't spend a fortune to say "I love you" with flowers.

Understanding Amaryllis
Deborah Brown, Extension Horticulturist

Many colorful amaryllis. Photo credit: Deb Brown

Most people achieve spectacular results when they first plant amaryllis bulbs, but many run into trouble getting them to bloom following years. The bulbs are too costly to feel good about enjoying them once, then tossing them away as you would hyacinth or crocus bulbs that were forced to bloom for the holidays.

Unfortunately, lots of misinformation is passed on about these amazing bulbs, including some questionable recommendations found in the instructions that often accompany their sale.

First, let's dispel the myth that amaryllis must spend the summer outdoors and the autumn in the basement. They can thrive indoors in a bright, sunny window year-round where they'll bloom each March or early April.

Still, gardeners usually prefer allowing amaryllis bulbs to become dormant each fall so they can bring the pots up every few weeks, spreading bloom over a long period of time.

There's also the consideration that their long, strap-like leaves do not make for particularly attractive foliage plants. But, oh, those flowers! Up to ten inches across, four to a stem, in shades of deepest carmine to blushing pinks and pure white with green throats and red edges, they're a sight to behold, especially on a cold, wintry day.

There are two keys to growing amaryllis bulbs successfully. The first is recognizing the plant's need for high light levels. Without adequate light amaryllis will only produce long, floppy leaves; no blooms beyond the first season.

Amaryllis need sunny spots. Photo credit: Deb Brown

The second is providing a deep container with soil that drains well, and planting each bulb so its upper half sits above the soil surface. Because they're so large and fleshy, amaryllis bulbs will rot easily when kept excessively moist.

Once sprouted, place amaryllis in a sunny location. The warmer your room, the faster they'll develop. As buds expand, you may choose to pull the pot out of direct sunlight into a slightly cooler place so flowers will last longer. Nip off blooms as soon as petals begin to fade, so no energy is lost in seed production. But don't pull out the flower stalk until it yellows and withers; it continues to gather energy as long as it remains green.

After flowering replace amaryllis in full sunlight. Once frost-danger has passed, you have the option of moving pots of amaryllis outdoors for the summer. Start off in a shaded place, but move them gradually to full sun. Fertilize two or three times with a liquid plant food meant for bulbs or flowers, checking often to see if you need to water. Set containers on stones so rainwater flows freely out their drainholes.

In September, before frost, move the bulbs to a cool, dark place in the basement. Stop watering entirely; remove foliage as it dries and browns. After two or three months in storage, begin bringing pots of amaryllis upstairs. By adding a little fresh potting soil, if needed, and watering the container thoroughly, you'll start the cycle over again. Six to eight weeks later your amaryllis should bloom, as lovely as before.

Start Onion Seeds Indoors
Deborah Brown, Extension Horticulturist

Onions (and pen). Photo credit: U of Mn. Extension Service

Many gardeners who plant onions from small bulbs or "sets" each spring are disappointed later in summer when their plants go to seed and stubbornly refuse to stop blooming. Once that happens, they don't increase much in size.

Onions are biennials. They normally bloom and set seed in their second growing season. Since sets have already experienced one growing season (granted, a short one) they're primed to reproduce after you plant them in the garden. Harvest them as green onions or use them in cooking. Don't count on them for long term storage.

If you want to grow large, firm onions for use next fall and winter, sow seeds late February or early March, indoors. Once they sprout, keep onion seedlings in a sunny, south-facing window, or better yet, a few inches below fluorescent lights.

Transplant the little, grass-like seedlings outdoors as soon as garden soil is dry enough to work thoroughly. If your soil is fertile and well-drained, there's plenty of sunlight, and you water regularly throughout the summer, you should harvest beautiful, large "keeping" onions next fall.

Order Oriental Vegetable Seeds
Deborah Brown, Extension Horticulturist

Bitter melon. Photo credit: Deb Brown

One of the benefits of more diverse cultures in Minnesota has been our exposure to interesting new cuisines, including many from Asia. People who visit farmer's markets in the Twin Cities have seen beautiful displays of produce grown by Southeast Asian families. They include " oriental vegetables" previously unknown to midwesterners, as well as many unusual varieties of vegetables more familiar to us.

Whether you're a seasoned, experienced gardener looking for something new to grow, or a beginning gardener with a yen for authentic stir fry, you can grow some of these vegetables at home next summer.

You'll need a nice, sunny location for most of them; five or six hours of mid-day and afternoon sun is considered a minimum for decent vegetable productivity. Stay away from large trees and hedges. Even when they don't shade the garden much, their roots will compete for moisture and nutrients.

Work plenty of organic matter such as composted leaves and grass clippings, baled peat or well-rotted manure into your garden. It helps open heavy, compacted soil so it will drain better, but actually holds onto moisture and nutrients in light, sandy soil. Organic matter does not add much nutrient content to the soil, so have your soil tested to see how much fertilizer to apply. If you want to try asparagus beans, bitter melons, edible gourds or other oriental vine crops it's best to construct a support system to grow them vertically rather than letting them sprawl on the ground. This saves garden space and lets you find the fruit more easily so you can pick it at the right stage of development. Even more important, it keeps the fruit clean and allows for good air circulation, which means less disease.

Asian veggie seeds. Photo credit: Beth Jarvis

Locate vertical supports on the north end of the garden if you've got direct sunlight all day. That way they won't shade shorter plants as the sun moves from east to west across the sky. If your garden receives mostly afternoon sun, put them on the east side so they get lots of strong sunlight from the south and west.

Here's a sample of some intriguing oriental seeds you can buy:

Red Beard Bunching Onion - These onion plants grow 2 1/2 feet tall, with long red stalks for slicing (no bulbs).
White & Long Radish - White skinned radishes, 2 inches in diameter, 16 inches long. Slice them as you would cukes.
Seedling Sugar Pea - Grow this pea for its tender young shoots; pick them when they're only 4 or 5 inches tall.
Chinese Fuzzy Gourd - Pick these squash-like vegetables while they're still small and immature.
Extra Long Eggplant - These eggplants grow about 1 foot long and are 1 1/2 inches in diameter, with light purple skin and delicate flavor.
Garland Chrysanthemum- Harvest these stems and leaves when they're 15 inches tall; use them in soups or stir fry.

Two New Blueberries for Minnesota
Erica Davis, Extension Educator - Horticulture, Hennepin Co.

Polaris blueberry. Photo credit: U of Mn. Extension Service.

Considering blueberries for your home landscape? White flowers in spring, beautiful red fall color and scrumptious berries are some of the best reasons to choose this plant if you have the right site. If you have acid, loose and well-drained soil in a sunny or mostly sunny location, you might consider planting Polaris and Chippewa, two new cultivars released in 1996 from the University of Minnesota fruit breeding program. Bear in mind that many blueberry cultivars benefit from cross-pollination with a different cultivar to achieve optimum fruit set and size.

Polaris is a very early ripening variety, producing very firm, medium to large-sized berries with a balanced and highly aromatic flavor and light blue color. Plants have an open growth habit, reaching 30 to 60 inches in height and spread at maturity. Polaris is highly self-unfruitful so it should be planted with another variety. Because of their firmness and small fruit scar, berries can be stored up to 3 weeks under refrigeration provided the berries are kept dry. Polaris was selected at Elk River, Minnesota in 1972 from a cross between B15 (cross between USDA selection G65 and a wild selection in northern New York called 'Ashworth') and Bluetta.

Chippewa ripens early to midseason and produces large, firm berries with a balanced, sweet flavor and very light blue color. Plants have a bushy growth habit, reaching 30 to 60 inches in height and spread at maturity. Because it is somewhat self-fruitful, Chippewa is recommended for home gardens and landscapes, but will produce more and better fruit if it is planted with a different cultivar. Storage life under refrigeration is short - only a week, so eat all you can and freeze the rest quickly! Chippewa was selected in 1972 at Elk River, Minnesota from the cross B18A and US3, made back in 1967. B18 was selected from a cross between USDA breeding program highbush selection (G65) and 'Ashworth.' US3, from the USDA breeding program, was selected from a cross between the highbush cultivar 'Dixi' and a wild blueberry selection (Michigan lowbush No. 1) from central Michigan.

Fall color. Photo credit: U of Mn. Extension Service.

Harvest times can vary from year to year. According to University of Minnesota fruit breeder Jim Luby, "The harvest period for any single bush lasts about 2 to 4 weeks depending on the crop load, with heavier cropping bushes taking longer." Harvest time for Polaris usually starts around July 4 near the Twin Cities. Of course this can vary by a week or so on either side depending on several factors, such as warmer or cooler microclimates. Chippewa and other cultivars recommended for Minnesota can be harvested starting around July 11-15. When in doubt, taste! Berry color should be blue rather than purple. When cross-pollinated, a typical yield for both Polaris and Chippewa is between 3 and 8 pounds per bush. Enjoy!

Soil pH is the most limiting factor in blueberry production and is most accurately determined by a laboratory soil test. Soil test forms can be obtained from your county Extension office. Optimum pH for growing blueberries is 4.0 to 5.0, but if your soil pH is between 5.5 and 7.0 and the soil texture is sandy to sandy loam, the soil can be modified by mixing in 4 to 6 inches of acid peat into the upper 6 to 8 inches of soil. Yellowing foliage is an indicator that soil pH is too high. If pH remains high for an extended period, plants will not survive. Elemental sulfur can also be used to acidify soil but requires at least one year for the pH to adjust.

Thank you to James Luby, Professor at the University of Minnesota Department of Horticultural Science, for the information he provided.

Grow a Little Love in Your Garden
Beth Jarvis, Yard & Garden Line Project Coordinator

Love-in-a-puff. Photo credit: Beth Jarvis

Trying to put a little "love" in a garden can be frustrating. Love-in-a-mist (Nigella damascena) just doesn't do it for me. Love-lies-bleeding (Amaranthus caudatus) sounds too sad to contemplate. "Love vine" is another name for dodder, a parasitic plant. But love-in-a-puff (Cardiospermum halicacabum) has potential!

Cardiospermum is Greek for heart seed. It's native to tropical America which transplates to hardy to USDA zones 10-12 (southern Texas and Florida). It's found growing wild as far north as UP Michigan and eastward. Although I've not yet found a spot for it my my garden, I'm delighted that Arla Carmichael, head gardener at Noerenberg Garden, keeps this annual vine as a (tender) perennial repeat visitor in her garden.

This soapberry (Sapindaceae) family member has a vining growth habit with alternate leaflets of 3 coarsely toothed leaves that provide a ferny foliage effect. Insignificant flowers, about 1/4" across, have 4 white, unevenly sized petals (click here to see the flower)that eventually give way to a green bubble, 1" to 1 1/2" in diameter. These green balloons are the seed capsules. Ok, so the capsules are the "puff", (click here to see puff)
so where's the "love"? It's the small black seeds found inside each puff. At the point where each seed was attached to the capsule, the seed now wears a white heart.

"Love" seeds.

This love is no shrinking violet, either. The plants climb, by tendrils, to about 10' in a season and should be spaced 12-14' apart for screening purposes. Love-in-a-puff grows best in moist, well drained soils and can become overly amorous (AKA: weedy). In fact, I found it listed on an Australian weed list where it was rated a "serious" weed. A not quite as serious weed on that same list was Dutchman's Pipe (Aristolochia durior). One gardener's weed is another's treasure.

If you plant to use them in your garden, start the seeds about 2 months before you plant to set them outside.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/Ent.htm

Pavement Ants in Homes During Winter
Jeffrey Hahn, Assistant Extension Entomologist

Pavement ant. Photo credit: U of M Entomology Dept.

Since Minnesotans have to endure cold, snowy winters, there are certain things we expect in return. Among other things, we assume we won't see many, if any, insects. Close to the top of that list are ants. They live outside and should be out of sight, out of mind during the winter. Unfortunately, ants have other plans. Not only do we see ants when it's cold, but some types of ants are more common in our homes during winter than during summer.

The ant most commonly seen in homes now is the pavement ant. This ant is about 1/8th inch long and reddish brown. With magnification you can see two nodes on their petiole (the waist between the abdomen and the thorax) and a pair of small spines on the back of their thorax. Pavement ants prefer to feed on greasy food, including meats, dry pet food, and peanut butter.

Pavement ants nest in the soil, usually under objects, such as stones, bricks, sidewalks, and driveways. They also commonly nest under concrete slab construction of homes. The warmth from homes helps keep nests active during winter. Workers move up through cracks into the home to forage for food and water. Ironically, many people that see pavement ants during winter do not see them in the summer (the ants are more likely to forage outdoors).

If you can determine where the pavement ants are entering through the slab, the best solution is to seal cracks in the concrete to prevent them from entering. If this isn't possible, the best long-term control technique is to bait them. You can purchase baits commercially; find one that is effective against grease-feeding ants. You can also hire a professional pest control service to treat your ants. Depending on conditions, baits take several weeks to several months to be effective, but will eliminate the colony.

It is also possible to make your own bait by mixing 2 parts boric acid to 98 parts meat grease. Home-made baits can be effective but there have been reports of pavement ants not accepting the bait after initialing taking it. This could happen if there is too much boric acid mixed into the bait.

You may tempted to spray the ants with an aerosol can of household insecticide. You can obtain immediate but only temporary relief from the invading ants; there is no effect on the colony and foragers will return. Don't combine spraying and baiting, as spraying interferes with the movement of the bait back to the colony, prolonging the problem.

If you do nothing to the pavement ants, in many cases they go away on their as the weather becomes warmer.

Not all ants seen during winter are pavement ants. Field ants and yellow ants are similar in habits to pavement ants and are just nuisances. Control for these ants would differ from that for pavement ants. Carpenter ants may also be seen during winter. They are potentially destructive to homes because of their preference for nesting in wood. If there is any question about ants seen in homes, the best, first step to have the ants identified to know the best methods to deal with them.

Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/Plpa.htm
Making an Accurate Plant Disease Diagnosis, Part 2
Chad Behrendt, Extension Plant Pathologist

Necrosis and chlorosis on lily of valley. Photo credit:

Infected spruce beside resistant spruce

Random necrosis on Snow on the mountain.

Uniform necrosis on American linden.

Dead, curled branch tips on crabapple. Photo credit: Photos: Chad Behrendt

In the last issue of the Yard and Garden News I provided an outline for making an accurate plant disease diagnosis. This outline consisted of five steps and a number of relevant questions for each step. In this issue I will discuss some of the potential answers to these questions, and how to interpret them. It is important to remember that a good diagnostician must ask questions, listen to the answers, and keep looking. A good diagnostician must also remember that there are always exceptions.

Before I begin there are a few terms that we need to define. Abiotic is defined as a non-living agent such as wind, moisture, or temperature. Biotic is defined as a living agent such as fungi, bacteria, nematodes, etc. Chlorosis is defined as a lack of chlorophyll or yellow coloration. Necrosis is defined as browning and death of the tissue.

Steps to making an accurate diagnosis; how to interpret answers.

1. What is the Host?
Identifying the host may be the easiest step in the diagnostic process, but still one of the most important. First, be certain that the host is properly identified. Spruce trees, which are often called pine trees, are infected by different diseases than those infecting pine. Proper identification of the host allows you to determine if the plant is hardy, the most common diseases affecting that plant, and whether the plant contains any resistance. For example, Colorado blue spruce is a common tree in the home landscape. Although this tree is able to survive in Minnesota, it is often stressed and heavily infected by two diseases, rhizosphaera needle cast and cytospora canker. Colorado blue spruce is also less resistant than our native white or Norway spruce to these diseases.

2. Identify the problem?
As stated in the original outline, this is probably the most difficult step in the diagnostic process. Although there are a variety of different questions that can be asked during this step, I am going to focus on a few of the most important.

a. What is the pattern of disease?
The question asks whether the problem is occurring uniformly or randomly throughout the plant. In general, a random distribution of the problem indicates a biotic problem, while a uniform distribution indicates an abiotic problem. For example, random spotting of the leaf tissue on the plant would indicate a fungal leaf disease, while a uniform browning of the leaf margins over the entire plant would indicate an abiotic stress.

b. What symptoms are present?
There are many different answers to this question, but the most common include yellowing or browning leaves, branch dieback, death of the plant or some part of it, wilting or drought like symptoms, spotting, curling, and irregular growth. Each one of these symptoms or combination of symptoms can be linked to a general problem. For example, wilting or drought-like symptoms signify that the plant is suffering from a lack of water. What we are unsure of is whether the lack of water is related to drought, a root rot, or a wilt disease. To identify the cause we would need to ask more specific questions. In some cases the described symptoms can be linked to a more specific cause. For example, circular, necrotic spots on the leaf tissue usually signify a type of fungal or bacterial leaf infection.

c. What portion of the plant is infected?

Disease spreading in pines. Photo credit: Robert Blanchette

The answers to this question may include top or bottom, leaves or branches, north or south, or the oldest or newest growth. Usually these answers are used in combination with previous answers to help eliminate other possibilities. For example, brown, necrotic leaf spots near the base of the plant indicate that the problem is most likely a fungal leaf disease. We make this assumption knowing that fungi germinate and grow where there is sufficient moisture and that fungi are disseminated from debris on the ground. Here is a second example. Both the leaves and the new growth (shoots) of an ornamental crabapple tree are blackened and curled. Since the problem is occurring on the new leaves, as well as the shoots, we can speculate that the problem may be spreading from the leaves to the shoot and therefore biotic in nature. Here is a third example. Many of the needles on a pine tree are yellowing and browning. There are no spots on the needles and the rest of the tree looks healthy. Only the oldest, inner needles are dropping. Knowing that trees naturally drop their oldest needles every fall, we can assume this is fall needle drop.

d. When did the plant become infected?
Typically you will not get an accurate answer to this question. However, knowing the time of year or season will help identify the problem. For example, anthracnose is a springtime disease of shade trees, wilt diseases are most conspicuous in mid summer, and powdery mildew is most noticeable in the fall. Knowledge of the common diseases and the time of year they occur comes with experience.

e. Is the problem spreading?
If the problem is truly spreading, it is most likely caused by a biotic factor. If the problem is not spreading, it is probably caused by an abiotic factor. This statement is based on the assumption that most environmental factors such as freezing and drought, affect the entire plant at the same time, while biotic organisms continue to infect plants over a period of time.

3. What were the previous growing conditions of the plant, both cultural and environmental?
Again, there are a number of different questions that can be asked, but I am only going to highlight a few of the key questions.

a. Was the plant planted on the appropriate site, properly fertilized, watered, and mulched?

This is simply a stress question, asking whether or not the plant is healthy and vigorous. If the plant is stressed it will be more vulnerable and susceptible to infection. For example, stressed turf is highly prone to infection by a number of fungi, specifically rust.

b. Were there problems with this specific plant or crop in previous years?
If there were problems in previous years, the cause may be a soil borne pathogen that is able to survive in the soil for many years.

c. What type of chemicals has the plant been exposed to?
This question is self explanatory, but important. Herbicides and road salt are two chemicals that frequently damage plants.

d. Is there a pattern to the problem?

Brown needles above snow line. Photo credit: Dept. of Plant Pathology

The answer and interpretation of this question is similar to the question above. A uniform distribution of the problem in the environment indicates an abiotic factor, while a random distribution indicates a biotic problem. In addition, movement or spread of the problem indicates a biotic problem, since environmental factors tend to affect all of the plants in that area at one time.
e. What other plants, if any, in the area are affected?
If most of the plants in the area are affected (uniform), the problem is probably abiotic. For example, a late frost may affect a number of plants in the landscape. Here is a second example. Large accumulations of road salt on a boulevard strip may kill the grass and cause marginal browning of the leaves on deciduous trees. Unfortunately, when only one species of plant is affected, we cannot make the assumption that the problem is biotic.

f. Where is the plant located?

Witch's brooming on ash beside road. Photo credit: Chad Behrendt

Microclimate and the location of the plant can provide a lot of clues as to the cause of the problem. Some examples: plants located along roadways are usually exposed to winter salt spray; plants located in low lands may suffer from flooding or wet soils; plants located near buildings may be sheltered from the wind, whereas plants in the open may suffer from winter injury.

4. The process of elimination.
The process of elimination should be ongoing and continuous. Every time you ask a question and receive an answer, you should be narrowing the field of possibilities. For example, as soon as you have identified the host you should identify the common diseases. The next step is to identify the problem and the symptoms involved, eliminating as many of the common diseases as possible. As you progress, your questions should become more specific to help narrow the field of possibilities.

Case Study:
P: A person wants to know what is wrong with their oak tree and why it is losing leaves?
Y: You should immediately ask the person what species of oak tree they have too properly identify the host.

P: The person thinks that the tree is a white oak.
Y: Now you should begin to think of a few common diseases that occur on white oak and start asking questions that will define the problem. For example: What symptoms are you seeing? What color are the leaves when they fall? When are the leaves falling? Are the leaves necrotic (brown) or chlorotic (yellow)? Are the leaves spotted? How many leaves are falling?

P: The person responds that many leaves have began to fall over the last week (it is now the first week of June). The leaves are brown and curled with some green. Some leaves appear to be spotted.
Y: You should begin to suspect a fungal leaf spot based on the answers provided, but you may be unsure. If you are unsure of the problem, you should continue to ask the person specific questions regarding the trees symptoms and recent weather. For example: What portion of the tree is losing leaves? Are there brown leaves in the tree? If so, where? What has the weather been like? Are there any other trees in the yard that are affected? Did this problem occur last year?

Leaf spots on oak. Photo credit: Chad Behrendt

P: The person responds that the brown leaves are near the base of the tree. It has been very cool and wet this spring. There are two white oaks that are losing leaves but no other trees, including oaks, are losing their leaves. The problem may have occurred last year, but it wasn't this severe.
Y: If you are still unsure, you should begin the process of elimination. For example: The problem is only occurring on two white oaks, so you should suspect a biotic problem. The problem appears to be affecting only the lower leaves and the leaves are spotted, so you can eliminate root rots, wilts, and stem cankers. Weather has been cool and wet, so there has been plenty of moisture for fungal activity. Therefore, your initial diagnosis should be a leaf-spotting organism. If you aren't familiar with the common diseases of oak, check a reference and you will find that anthracnose is a common spring time disease of white oaks.

It is important to remember that you are not going to be able to diagnose every problem or disease. In certain cases, multiple diseases or a complex of problems may occur making the diagnosis difficult. Remember to thoroughly utilize your reference materials and your local professionals when stumped. Finally, becoming a good diagnostician takes time and practice. The more diagnoses you make, the more background knowledge you will gain, and the more familiar you will become with the common diseases and the symptoms they cause.

Happy Diagnosing!

Getting To Know Your Fungicides: Lime-Sulfur
Chad Behrendt, Extension Plant Pathologist

Lime-sulfur, a fungicide composed of inorganic sulfur and lime, is commonly used today to control a variety of diseases such as plum pockets, black knot, black spot of rose, and a number of raspberry diseases. Lime-sulfur was originally developed in 1851 by Grison who was the head gardener at the vegetable houses in Versailles, France. Grison boiled "flowers of sulphur", freshly slaked lime, and water for 10 minutes, drew off the clear liquid and mixed it with water. He then used this solution to protect plants against mildews. The solution was originally known as the "Grison Liquid" or "Eau Grison". In 1886, lime-sulfur was used to control peach leaf curl in California.

Black knot on plum branch. Photo credit: Plant Disease Clinic

Sulfur is the only ingredient in the mix that is toxic to pathogens. It is able to kill pathogens through direct contact or fumigation (sulfur vapors). The vapor action of sulfur allows the fungicide to be effective from a distance and is important in killing spores of powdery mildew. Once taken up by the fungus, sulfur disrupts the transfer of electrons causing the reduction of sulfur to hydrogen sulfide (H2S), which is toxic to most cellular proteins.

Sulfur itself is also toxic to certain plant species and is capable of causing a phytotoxic reaction. As a result, lime has been added to the mix to reduce the phytotoxicity of sulfur. The more lime added to the mix the less phytotoxic. In general, lime is considered a "safener" for the plant. According to the label, lime-sulfur can be applied as a dormant season fungicide or as a growing season spray. Dormant season applications need to be applied in late winter or early spring when temperatures are above freezing, but before leaves are present on the plant. Growing season applications can be made after leaves are present on the plant, but should be applied in the early morning or late afternoon to avoid burning. Plant damage caused by lime-sulfur is most severe during dry weather when temperatures reach 80° to 95° F. Lime-sulfur is corrosive to the eyes and harmful if swallowed, inhaled, or absorbed through the skin. Appropriate precautions according to the label should be taken when applying lime-sulfur. Thoroughly read the label before purchasing, handling, or applying lime-sulfur.

Editorial Notes

Snowdrops, the first to bloom Photo credit: Beth Jarvis

Our coldest month is now behind us and the snowiest yet to come. Yet, by late March, just weeks away, the snowdrops should be up and blooming! Thoughts like that sustain us.

Next month, Doug Foulk, Ramsey Co. Extension Educator, who has been researching organic/low-input apple growing, will share some of his findings. Topics should include disease resistant apples and a bit about apple rootstocks. Christian Thill has promised a piece on potatoes this spring, as well. In an upcoming issue, Mary Blickenderfer, shoreline vegetation and landscaping specialist, will be sharing some ideas on landscaping around ponds.

I'm always looking for article ideas and have received some intriguing story suggestions. So, don't be shy!! Your story suggestions are most welcome!

Yard & Garden Line News is on its winter publication schedule. We will publish only on the first the month from now until April. Then, we'll resume twice monthly issues, on the first and 15th of the month.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, the Water Line, INFO U and the Soil Testing Lab.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771.

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator

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