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August 2011 Archives

Contents: August 15, 2011

Bacterial Spot Shows up on Tomatoes

Michelle Grabowski, UMN Extension Educator

M.Grabowski, UMN Extension

Photo 1: Bacterial spot on an heirloom tomato

Bacterial Spot, caused by the bacteria Xanthomonas campestris pv. vesicatoria, has been found in several areas of Minnesota. This bacterial pathogen causes dark brown to black leaf spots with a pale yellow halo around them. Often the leaf spots dry up and crack, resulting in tiny holes at the center of the spot. Probably the most noticeable symptom of bacterial leaf spot of tomato, are the raised brown or black corky spots on fruit. These spots range in size from the diameter of a pencil tip to the diameter of a pencil eraser. Fruit spots can be seen on both green and ripe tomatoes. The spots are superficial and do not rot the fruit. Therefore the tomatoes can still be eaten, although they may be difficult to peel if you plan to use them in your next batch of spaghetti sauce. To learn more about managing bacterial spot of tomato read 'What are those spots on my tomato?'.

Peppers - Sweet and Heat!

Karl Foord

Photo 1: Sweet peppers

Karl Foord, UMN Extension Educator

I traveled to Bagley, Minnesota to Ter-Lee Gardens, the home and farm of Terry and Loralee Nennich. Ter-Lee Gardens offers Pick-Your-Own strawberries at the farm and almost every vegetable that you can think of, most of which is marketed at the Bemidji Area Farmers' Market. I had heard that Loralee was growing more than 50 varieties of peppers and was intrigued. Terry is a colleague of mine and he persuaded Loralee to give me a tour of the two high tunnels where she was growing her peppers. You can see the peppers she showed me on photos 1 and 2.

Karl Foord

Photo 2: Hot peppers

Most pepper cultivars come from the species Capsicum annuum, whose center of origin is Mexico. The Habanero and Tabasco peppers come from C. chinense and C. frutescens, respectively. The center of origin for these species is the Amazon River basin in northern South America. The amount of variation in size shape and color is impressive. Especially fascinating are the color changes that many of the cultivars go through as they ripen. Most but not all start out green and then turn various shades of yellow, orange, red, and purple. Others start out purple, chocolate, or gray green and stay that color. Beyond color and size C. annuum peppers can be divided nicely into those that are sweet and those that "bring the heat". Loralee had plenty of each.

Karl Foord

Click to enlarge

The spicy heat of a pepper is a function of the amount of the compound capsaicin present in the pepper; the more capsaicin the hotter the pepper. Capsaicin stimulates chemoreceptor nerve endings in the skin, especially the mucous membranes. Each hot pepper variety is characterized by a range of capsaicin that it may contain as denoted by the Scoville scale measured in Scoville heat units (SHU). The scale was named after its creator Wilbur Scoville. There is also a rating scale from 1 to 10 also based on SHU (photo 3).

Karl Foord

Photo 4: Cayenne Pepper 'Andy'

Although the genetics determine the potential of heat, the environment can significantly modify the production of capsaicin. Growing temperature, hours of sunlight, moisture, soil chemistry, and the type and amount of fertilizer used can all be influencing factors. The conditions under which it a pepper was dried can also influence heat. The habanero pepper seems particularly sensitive to environmental factors and can vary in heat by a factor of 10.

Karl Foord

Photo 5: Anaheim pepper

The names of many of the pepper types and or varieties reflect where they were developed. For example:

These peppers came from the Cayenne district of French Guiana (photo 4).

Karl Foord

Photo 6: Jalapeño pepper

Anaheim: this green pepper was cultivated for a canning factory in Anaheim, California. (Editor's note: The first American canning factory was constructed in New York City in 1812. The canning industry moved westward and became active in the latter part of the 19th century). These peppers are also known as California Chile and Chile Verde and are used in the making of chiles rellenos. If Anaheim peppers are left on the bush to ripen, dried and ground into pepper, the product produced is Chile Colorado (photo 5).

Karl Foord

Photo 7: Paprika pepper

Jalapeño: When dried, the Jalapeño is known as "Chipotle" and around 20% of the Jalapeño harvest is dehydrated for Chipotle sauce (photo 6).

Paprika: Paprika is the Hungarian word for pepper, and the actual pepper was developed in Hungary (photo 7).

Pimiento: "Pimiento" is the Spanish word for "bell pepper" while "Pimento" or "pimentão" are the Portuguese words. Pimento peppers are the familiar red stuffing found in prepared Spanish green olives.

Padron: These peppers came from the Padron region in the province of Coruna in Spain.

Habanero: traveled from South American and is postulated to have come from Cuba and named after Havana thus the name "Habanero".

Karl Foord

Photo 8: Bell pepper 'Lilac'

Check out a nearby farmers' market to see the variety of peppers available. If your market produces anything close to the variety that Loralee grows, you are in for a treat.

If you are interested in growing some of these varieties please see the publication: Growing Tomatoes, Peppers, and Eggplant in Minnesota Home Gardens

Special thanks to Loralee and Terry Nennich of Ter-Lee Gardens for sharing their time and expertise on peppers.

The Garden Blues

Samantha Lahman, University of Minnesota Extension Horticulture Intern, Douglas County

Centaurea cyanus, more commonly known as the annual Bachelor Button or Cornflower, is in full bloom in the garden this summer. Cornflowers are easy to grow and come in a great variety of colors, which has made them a long time favorite for novice and experienced gardeners. The Cornflower received its common name from the flowers that bloom wildly in the grain fields of southern Europe. It is even rumored that the Cornflower was selected as Germany's National Symbol of Unity because Queen Louise of Prussia; upon fleeing Germany to escape Napoleon, reportedly hid her children in a cornfield and kept them quiet by weaving Cornflowers into wreaths.

Samantha Lahman

Cornflowers are tall annuals that grow on beautiful grey-green stems. The most common color is a bright blue (Blue Boy), but other varieties range from pinkish white to deep maroon. Growing to a height of 24-36 inches, they can be easily placed in gardens of any size and are beautiful fillers along borders. They are also useful in cut flower gardens and are commonly included as dried flowers in everlasting arrangements. For an unusual twist, use their edible blooms to add color to salads and other dishes. Along with their aesthetic and tasteful qualities, Cornflowers are often used to attract bees, butterflies, and birds.

Cornflowers have become such a staple due to their prolific nature. Even the most inexperienced gardeners can grow them successfully. These plants thrive in full sun, but can also grow in partial shade. They prefer moist, well drained soils and will grow well in soil pH levels ranging from 6.6 to 7.8. They are also moderately cold tolerant and can endure temperatures that reach into the low 40s.

Cornflowers are most commonly grown from seed. Sow cornflowers in the spring, approximately 1 to 2 weeks before the last frost. Planting at this time will give you early spring blooms. Germination can be expected in 7 to 10 days. Seeds should be sown 1/4" deep and placed 1" apart .For earlier blooms, start seeds indoors about one month prior to the frost free date. When starting your seeds indoors sow 3 to 4 seeds per pot and cover the seeds with a 1/2" layer of the mix because centaureas need darkness to germinate. Cover your pots with plastic wrap, or a clear plastic dome to retain soil moisture and humidity. When seedlings emerge, remove the plastic covering to avoid overheating and leaf burn. Once your cornflowers are approximately 2 inches tall, transplant outside in your chosen garden location. For optimum success, transplant your seedlings on a calm, overcast day. While these plants are known to be tough, it is easier on the plants if they aren't immediately exposed to excessive heat and damaging winds. Remember to water immediately following transplanting. When seedlings are 1 to 2 inches tall, thin to 6 to 8 inches apart. Cornflowers bloom for approximately one month. If you wish to have an extended blooming season, consider successive plantings. Planting every two weeks will insure that your blooms last the summer.

Samantha Lahman

After they are established, watering should be done infrequently. Yes, infrequently. Another charming quality of cornflowers is that they are extremely drought tolerant. When over watered, the cornflower's stems will become droopy and soft. As with most flowers, remember to trim dead and expiring blooms to encourage the growth of new blooms. Cornflowers are generally pest resistant. The most common pest to invade Cornflowers is the aphid. To control aphids, you can spray them off with a garden hose or apply an insecticidal soap. These little flowers are also very resistant to diseases and fungi. Extremely wet weather leads to fungal problems such as: rust and powdery mildew. To help prevent fungal infections, water at the base of the flowers so as not to get the leaves wet, and remove any leaves or stems that you suspect are infected. Use fungicidal soap or garden sulfur to control rust on plants.

Before investing your area of garden to cornflowers forever, by planting centaurea Montana, the perennial version of centaurea, take into consideration that while Centaurea cyanus is an annual, this does not mean that you will need to replant year after year. Many times cornflowers will re-seed. To encourage this natural re-seeding, leave the last blooms of the growing season on the plants.

I adore blue in the garden, and am always looking for new and unusual "blues" to add. However, my staple "blue" is the prolific cornflower. If you also love "the blues", and are looking for attractive, multi-use blossoms, cornflowers are the way to go.

"The blues tells a story. Every line of the blues has a meaning."
John Lee Hooker

Samantha Lahman is the 2011 Summer Intern for the Horticulture Extension in Douglas County. This summer she has been busy writing the "Growing Green" newspaper column for local newspapers, diagnosing plant problems, identifying bugs, updating the West Central Gardener Facebook page, and creating a workshop for the Douglas County Master Gardeners to use in the future on "Growing Your Own Meadow Garden." Samantha will be a senior this year at the University of Minnesota, Crookston. Her major is Animal Science with minors in Communication and Agricultural Business. After college she hopes to work either for the U of M Extension in the 4-H and Youth Development areas or Public Relations for one of the Minnesota livestock associations.

Lydecker/BlackIce™ Plum: A New Plum for the Midwest

Brian Smith, UWRF

Photo 1: Lydecker® BlackIce™ Plum. 'Oka' ( Prunus besseyi x P. salicina) x Z's Blue Giant (P. sal.).

Emily Dusek, University of Wisconsin River Falls

Plums have long been regarded as a fruit that can be grown in the Midwest, but the size and quality has never measured up to that of California's plums. Well we Midwesterners need not lament anymore because the new Lydecker/BlackIce™ Plum (bred by Dr. Brian Smith from University of Wisconsin-River Falls) exhibits many of the characteristics of Californian Plums all while being a winter-hardy plum!

This was achieved because the BlackIce™ was bred from a flavorful Californian plum (Z's Blue Giant) and a winter hardy plum (Oka). With this combination of genes, the BlackIce™ has a dark purpley-black tender skin, with rich juicy red flesh on the inside, and free-stone pit that does not stick to the flesh. All while being winter-hardy to as low as -35 ºF (Zone 3b) and ripening 2 to 3 weeks earlier then any other large quality plum for the Midwest!

Brian Smith, UWRF

Photo 2: Lydecker® BlackIce™ Plum. 'Oka' ( Prunus besseyi x P. salicina) x Z's Blue Giant (P. sal.).

In addition to an earlier ripening period and larger sized fruit (5cm x 5cm), the BlackIce™ exhibits many other positive characteristics, such as being naturally semi-dwarf in size and only growing to about 10' tall and 8' wide. It also has a weepy growth habit, which gives the BlackIce™ an interesting appearance in the winter and spring--but its main attribute is its ability to produce California-like plums in the Midwest.

To get the optimum yield of these tasty plums, it is necessary to plant another cultivar of compatible genetic background with the same bloom-time so cross-pollination can occur. This is because plum trees are self-infertile, and for successful pollination to take place there needs to be another plum within 50 feet. The preferred pollinator for BlackIce™ is Toka, but if there is a late bloom season for the BlackIce™ either 'Compass' or 'Alderman' plums will suffice.

it is very important not to apply any insecticide to your trees while they are blooming because otherwise the bees will not be able to carry the pollen from one tree to the other to pollinate your flowers so they can develop into fruit!

Photo 3: Black knot on a plum tree.

When growing fruit, it is crucial to monitor for pests. In regards to insects, the BlackIce's™ problems include scale, plum curculio, cat-facing insects and peach tree borer, the best control for any pest is always sanitation. So remember to remove all of your dead plant debris from the ground! In addition to good sanitation, it is also necessary to have a spraying regime in place to prevent and control all insects. The BlackIce™'s disease susceptibility is average to above average. It is still moderately susceptible to brown rot and black knot, which are fungal diseases that are also best controlled by the removal of all plant debris from the ground, and pruning off of any infected areas. And fungicide applications should be done just before bloom/early bloom, mid-bloom, and late bloom. Luckily, BlackIce™ is more tolerant than its Japanese-American hybrid counterparts to bacterial spot.

Once these simple control measures are in place, the enjoyment you receive from planting, growing, and eating these sweet plums will be boundless. For with these multiple attributes of color, and firmness combined with the winter hardiness necessary to survive harsh winters and short-growing seasons it is evident that BlackIce™ has the potential to bring the fresh taste of California to our very own backyards.

Editor's note: A good article on cat-facing insects can be accessed at the Utah State University Cooperative Extension.

Emily Dusek graduated with an A.S in Horticulture from Century College in 2009. She is currently attending University of Wisconsin-River Falls to parlay her A.S. into a Bachelor's of Science. She has also received invaluable hands-on lessons working at Farrill's Sunrise Nursery in Hudson, Wisconsin. Emily first got into horticulture as just a baby; she has been told her first birthday present was a mini wheelbarrow and watering can!

Apple Sunburn

Photo 1: Sunburn necrosis of apple.

Karl Foord, UMN Extension Educator

Sunburn to apples should be distinguished from sunscald. Sunscald is damage to the bark of the tree when strong winter sun warms up tissues on the south facing side of the tree. When the sun sets, the temperature plummets and this softened tissue is damaged by freezing.

Sunburn is damage to the peel of the fruit. The temperature of the apple peel can be significantly greater than the ambient temperature ranging from 18°F to 29°F above ambient temperature on a clear day when other conditions are favorable (Schrader et al., 20011). Factors influencing peel temperature include solar irradiation, air temperature, relative humidity, wind speed and direction, and tree vigor.

Photo 2: Sunburn necrosis of apple.

David Bedford, a research scientist at the University of Minnesota Horticultural Research Center, noted seeing a lot of this type of damage due to the high temperatures and high dew points experienced this summer.

There are two types of sunburn damage, necrosis and browning. Sunburn necrosis involves the thermal death of the tissue and occurs at 126 ± 2°F (Photos 1 & 2). Sunburn browning describes the presence of a yellow, bronze, or brown spot on the sun-exposed side of an apple and occurs at peel temperatures between 115 to 120°F.
Proper pruning use of shade cloth and application of particle films are methods that growers can use to protect fruit and avoid sunburn.

Thanks to Janelle Daberkow, horticulture educator in Stearns and Benton counties, and the Benton County Master Gardeners for providing photos.

¹Schrader, L. E., Zhang, J., and Duplaga, W. K. 2001. Two types of sunburn in apple caused by high fruit surface (peel) temperature. Online. Plant Health Progress doi:10.1094/PHP-2001-1004-01-RS.

What's happening in the orchard? Blueberries!

Tomato tip:
Consider pinching the growing tip of your indeterminate tomatoes in the next few weeks. By eliminating the growing tip the energy produced by the plant is focused on ripening the tomatoes presently on the vine. If not the vine will continue to produce flowers and fruit that will not ripen before the first frost. The rule of thumb is about 1 month prior to historic first frost. If you have ways to protect your tomatoes from the historic first frost you can likely extend the season for another month, and can prune accordingly.

Contents: August 1, 2011

Japanese Beetle (JB) Q & A

Jeffrey Hahn, Asst. Extension Entomologist

Q. Where did JB come from?

A. The first JB was found in Minnesota in 1968 after which the Minnesota Dept. of Agriculture (MDA) started a trapping program. Despite traps being set up in the Twin Cites area, between 1969 - 1979, only three beetles were captured. Between 1980 - 1983, only 16 JB were found. There were no trapping between 1984 - 1991.

Jeff Hahn

Photo 1: Japanese beetle adult close-up. Note feeding damage.

The trapping program resumed in 1991 and in 1992 298 JB were trapped. In 1994, over 6,800 were trapped in 12 counties. In1999, nearly 36,000 were trapped; over a half million in 2000; and over 1 million JB trapped in 15 counties in 2001 (99% of these were found in Hennepin and Washington counties). Then in 2002, the numbers crashed and only 1,682 in 19 counties were found.

MDA discontinued their trapping program after that, feeling that JB was established. Very few reports were received by Extension over the next several years. Starting in 2005, Extension started receiving noticeably more calls and e-mails on JB. Each year afterwards contacts about JB gradually increased and as they become more common each year. As of 2009, JB had been found in 27 counties, primarily in the Twin Cites and the southeast and south central regions of the state.

Q. How long do they feed?

A. JB emerge about July 1 each year and are active through September. They have been reported as late as October during late falls.

Jeff Hahn

Photo 2: Physically remove Japanese beetles and toss them into a pail of soapy water.

Q. Are there any non-chemical methods for managing JB?

A. The best method is physical removal. A good way to do this is to take a pail of soapy water and brush them off or pick them off by hand so they end up in the pail. The soapy water kills them. If you just knock them off plants, they will fly and return to them. It is best to do this right away in the morning or in evening when they are less active.

Q. Are there any low impact products I can use on JB?

A. There are a couple you could consider. Products containing Neem are reasonably effective, especially when JB numbers are low to moderate. They act as an antifeedant to deter JB from feeding on plants. Pyrethrins containing PBO (Piperonyl butoxide) is also effective. Both products need to be reapplied fairly frequently.

Q. What residual insecticides can I use to treat JB?

A. Neonicotinoid insecticides, especially imidacloprid (various trade names) and dinotefuran (Safari) are good choices. They are systemic, are easy to apply, and are long lasting. They do not kill JB quickly but they do cause them to stop feeding with death coming later. One important drawback of these products is they are very toxic to bees. Avoid treating trees and shrubs, like linden and roses, that are attractive to bees. It doesn't matter that the trees and shrubs are not flowering at the time of application as these insecticides will be active for a year.  Another consideration is that it takes some time, especially for imidacloprid, for the tree to take up the insecticide.  You need to factor this lag time when using these products.

There are also a variety of residual insecticides that you spray directly onto the leaves that are effective, including pyrethroids like permethrin, bifenthrin, esvenfalerate, and lambda cyhalathron, and carbaryl. Be sure that the foliage is throughly treated.

Jeff Hahn

Photo 3: Japanese beetle damage on linden.

Trees and shrubs are best treated as soon as damage and JB are first noticed. Since they have had about a month to feed, you should consider how much damage has already occurred if you are still thinking of treating. If over half of the tree or shrub has been defoliated then it probably not worthwhile to treat it any more this year. If at least half of the tree or shrub is green, then there is still value to use insecticides to help protect trees.

Q. What can I spray on food plants, like apples and raspberries.

A. There is not a simple answer to this as one active ingredient, such as permethrin, may be labeled for food plants on one product but may not be on another. People need to check to see if the particular food crop you intend to treat is on the label of the specific product you want to use. If it is, then you can use that insecticide to spray your desired edible plant. Then be sure to observe the interval between when you spray and when crops can be harvested.

If the crop you want to treat is not on the label, then don't spray it. Check the label before you buy a product and again before using it to be sure you know what plants can be treated.

Q. How effective are JB traps?

A. JB traps can catch what appears to be an impressive number of JB. However, research shows that they actually draw more JB into the area than what they catch. The result is you not only do not reduce JB adults and their damage but you actually increase the amount feeding damage that occurs to susceptible plants.

Q. How effective is it to treat my turf to prevent JB adults from getting into my garden?

A. Treating for JB grubs does not protect your yard from adult beetles. Adults are very mobile and can easily fly in from outside your property. Only treat your lawn if you are seeing damage from the grubs.

Click here for more information on Japanese Beetles.

Gray Mold on Geraniums

Michelle Grabowski, UMN Extension Educator

Ger botrytis Y&G.jpg

M.Grabowski, UMN Extension

Photo 1: Gray Mold on Geranium

Gray Mold is a common disease of flowers and even some vegetables. The fungus Botrytis cinerea is the pathogen that causes gray mold. This fungus thrives in wet weather. Recent rains have resulted in increased sightings of gray mold. Gardeners should look for brown spots on leaves with concentric brown rings like a bull's eye. Flowers can be blighted by gray mold at any stage. Brown blossoms or petals can all be caused by gray mold. A fine fuzzy gray mold can be seen on infected plant parts when moisture sits on the plants. Early morning is a good time to check for this pathogen as dew often encourages the fungus to produce spores.

Read more about gray mold.

Lilies - One of the Queens of the Garden

Karl Foord

Lilium 'Heart's Desire' Asiatic Lily. To see more photos, please view: Lilies Photo Essay.pdf.

Karl Foord, UMN Extension Educator

When entering the world of lilies for the first time, one is dazzled by the large spectacular flowers with variations in color, texture, size, fragrance, petal shape, and flower orientation. This variation is a function of: 1. species groups, such as Asiatic and Oriental designations, 2. single species, such as Lilium longiflorum (the Easter lily), and L. regale (the Trumpet lily), and 3. hybridizations between the above such as Oriental x Trumpet identified as Orienpet or OT hybrids, and Longiflorum x Asiatic identified as LA Hybrids (LA). Although this is still a simplification, it seems like a good place to start.

Cultivars derived from the latter crosses are selected for the best qualities of each species. The result is a hardier more garden persistent heat tolerant plant with sublime beauty. The lily collection at the Minnesota Landscape Arboretum contains predominantly Asiatic, OT, and LA hybrids.

This photo essay is a small sampling of these types of lilies. Regardless of your present knowledge and experience of lilies, there seems to be plenty of room for further exploration of this genus. Click here to view the photo essay: Lilies Photo Essay.pdf

Previous Y&G articles addressing lily issues can be found at:
Selecting Lilies for Your Garden

New Lily Classes Grow in Availability and Popularity

Further information can be found through the North American Lily Society and the regional Minnesota affiliate.

Watch out for BOB (Bur Oak Blight)

J. Pokorny, MNDNR

Photo 1: Bur Oak Blight

Michelle Grabowski, UMN Extension Educator

In 2010 a new disease of Bur Oaks was identified in Minnesota. Bur Oak Blight, also known as BOB, is caused by a new, and yet unnamed species of the fungus Tubakia sp. It has been identified in Ramsey, Hennepin, Sherburne, Mille Lacs, Washington and Anoka counties in Minnesota. Gardeners should be on the look out for Bur oak trees with browning leaf veins and brown wedge shaped lesions on leaves. Symptoms typically appear in the lower canopy and progress upwards each year. Leaf blight symptoms generally appear in July and August. If you suspect a bur oak is infected with Bur Oak Blight call the Minnesota Department of Agriculture Arrest a Pest Hotline: 651-201-6684 (metro) or 1-800-545-6684 (Greater Minnesota).

More Information about Bur Oak Blight.

Flowers - Beautiful, Nutritious, & Dangerous

Karl Foord

Photo 1: Goldenrod Spider "Flower Spider" "Red-spotted Crab Spider Misumena vatia; Male on top of female who has Spring azure Blue Butterfly Celastrina sp. in grasp

Karl Foord, UMN Extension Educator

While photographing lilies for the article "Lilies - One of the Queens of the Garden," I came upon a blue butterfly (perhaps a Spring Azure Celastrina sp.). I was hoping to photograph it when it had opened its wings. I slowly drew closer only to realize that it was not to open its wings again. It was in the grasp of a flower spider (perhaps a Goldenrod Spider or "Red-spotted Crab Spider" Misumena vatia).

A smaller spider perhaps a male of the species jumped on top of the other spider and then fled. I would expect this was a wise thing to do. This spider was particularly well camouflaged on this Lilium 'Heart's Desire' Asiatic Lily. Flowers are beautiful, nutritious and dangerous, depending on your point of view.

Karl Foord

Calendar: August 1, 2011

Julie Weisenhorn

Big Sky series echinacea 'Sunset'

Constantly pick ripe and oversize produce from your gardens to minimize yellow jacket (wasp) activity and to encourage plants to remain productive as long as possible. Remove fallen fruit as well, before it begins to ferment. Yellow jackets usually aren't aggressive, provided you don't swat at them or disturb them. They're attracted to soda and other drinks, so be very careful when you drink from a can you've set down for a while.

Late August through early September is an ideal time to add flowering perennials to your garden, whether you buy them from the garden center or use divisions from your own or your neighbor's plants, Make sure there are still two or three weeks of decent growing conditions expected after planting. Mulch around the perennials, then cover the area with 4" to 6" of mulch later, when the soil freezes.

Yard and Garden News Editor: Karl Foord
Technical editor: Bridget Barton

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