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Tuesday, May 5, 2015

Plant Seeds When the Time is Right

M. Grabowski, UMN Extension

Warm sunny days inspire gardeners to work outdoors. Although everyone is anxious for fresh vegetables from the garden, it is important to be patient and wait for the correct time to plant. Spring soils can be cold and wet. Some vegetables like peas and many leafy greens easily tolerate these conditions and can be planted in the garden as soon as the soil thaws and can be worked.

Cucumber seedlings killed by damping off. M. Grabowski, UMN
Members of the cucurbit family, including cucumber, zucchini, summer squash, melon, winter squash, and pumpkin need warmer soils to grow. These plants originate from tropical climates. Other tropical plants like tomato, eggplant and pepper are often started indoors and transplanted to the garden when weather conditions are right. Unfortunately, although cucurbits can be transplanted with care, they have delicate root systems and often do better when direct seeded into the garden. Winter squash and pumpkin seeds can be planted when soils reach 65 F at a 2 inch depth. Zucchini, summer squash, and cucumber need soils that have warmed to 70 F at 2 inch depth. Melons prefer to wait until soils are between 70 and 90 F. Soil thermometers are available at many garden centers.

If planted too early, seeds will not grow or will grow very slowly. Sitting in cold wet soil, seeds are very susceptible to several root rotting pathogens that cause a disease known as damping off. Damping off is rarely a problem for vigorously growing seedlings in warm soil that is moist but not soggy. Under cool wet conditions, however, damping off can kill every seedling.

To learn more about how to grow vegetables in Minnesota, visit the UMN Extension Garden web page for vegetables in the home garden.

Check Spruce Trees for Rhizosphaera Needle Cast

Spruce buds opening. M. Grabowski, UMN Extension
M. Grabowski, UMN Extension

Spring is here and spruce trees are opening their buds and developing young new needles. Now is a critical time to inspect spruce trees for Rhizosphaera needle cast, a common disease of spruce trees in Minnesota.  Rhizosphaera needle cast is caused by the fungus Rhizosphaera kalkhoffii. This fungus infects the young growing needles of Colorado blue spruce, white spruce and Norway spruce. New infections do not have obvious symptoms and many gardeners do not recognize the disease until it is too late to prevent new infections this year.

What to look for
Discolored needles with black spore producing structures. USDAFS
Examine the fully grown needles at the branch tips. These needles were new needles last year and if infected, will be developing symptoms now. Look for discoloration of any kind. Needles should be dark green to blueish green. Needles that look pale yellow green, brown or purplish brown are unhealthy. Use a hand lens to examine the needles. Tiny raised black dots on the needles are suspicious and may be fungal spore producing structures. Spore producing structures may be found on green needles or discolored needles. If needle discoloration or potential spore producing structures are observed, contact an arborist or send a sample to the UMN Plant Diagnostic Clinic to determine if Rhizosphaera is the cause of the problem.

Help for sick trees
Spruce Needles at half their mature length. M. Grabowski
If a spruce tree is infected with Rhizosphaera Needle Cast it can be helped, but gardeners will need to act quickly to protect this year's needles. The fungal pathogen overwinters on previously infected needles. Spores are spread from last year's infected needles to new developing needles by splashing rain or irrigation. A fungicide with the active ingredient Chlorothalonil can be applied to protect needles but timing is critical. The first spray should be applied when new needles are half the length of mature needles. A second application should be made 3 to 4 weeks later. This will protect the needles from infection. Fungicide sprays should be repeated next year, but beyond that trees will just need to be inspected to determine if sprays are needed. Many trees recover from Rhizosphaera needle cast after 2 years of treatment.

If left untreated, infected needles will die and fall off after 1 year. If a branch looses its needles 3-4 years in a row, the branch dies. Untreated trees often have dead branches on the lower part of the tree and infected branches higher up.

Preventing future problems
Needle loss from Rhizosphaera needle cast, M. Grabowski UMN
Gardeners can help keep spruce trees healthy with several simple practices. Rhizosphaera needle cast is most problematic on stressed trees, so reducing stress will reduce disease problems. Remove all weeds and turf grass from around the base of the tree. Add a level 2-4 inch layer of woodchip mulch around the base of the tree to keep moisture in the root zone, reduce competition with weeds, and prevent accidental damage from lawn mowers and weed whips. Water the tree during periods of drought with a soaker hose or garden hose directed at the base of the tree. Redirect lawn sprinklers to keep needles dry. Spores of Rhizosphaera need splashing water and moisture to start new infections.

Thursday, April 30, 2015

Watch out for ticks!

Jeffrey Hahn, Extension Entomologist

Spring is finally here.  And it once again is tick season.  Be aware of these blood thirsty arachnids when you are in fields, wooded areas, and other areas where ticks are know to frequent.  There are two common ticks in Minnesota, the blacklegged tick (also called deer tick) and the American dog tick (also called wood tick).

Both are nuisances because they bite to take a blood meal from not only people but also pests including dogs and horses. Blacklegged (deer) ticks are also a particular issue because they are a potential vector of Lyme disease and other diseases (see also Tick-borne disease in Minnesota). 

Protect yourself when you are out in known tick areas:
  • Stay on trails and try to stay out of brushy, grassy areas where ticks are more common.  
  • Wear long, light colored pants; for additional protection, tuck your pants into your socks.  
  • Use repellants: Deet can be treated on clothes and skin while products with permethrin can only be applied to clothing
  • Do a tick check when you return from the outdoors.  They are small and can be easily overlooked so look carefully.  Be sure to look in out of the way places, like behind ears or behind knees.

Adult female blacklegged (deer) tick. a potential vector of
Lyme disease and diseases. Photo: Jeff Hahn, UMExtension
If you do find a tick, especially if it has been biting, get it positively identified.  While American dog ticks are not an important disease vector, blacklegged (deer) ticks can transmit an array of diseases, especially Lyme disease.  For more information, see Ticks and their control.

Wednesday, April 29, 2015

Ignore Andrenid Bees

Jeffrey Hahn, Extension Entomologist

Andrenid bees are a type of native ground-nesting bee that is first seen during early spring. Residents are discovering them now in their gardens and lawns.  Some people have been concerned that these insects may be ground dwelling yellowjackets (wasps) but the overwintering queens are only just starting to build new nests and people would not be seeing any activity from their nests this early.

Andrenid bees like to nest in sunny, dry areas of gardens
and yards. Photo: Jeff Hahn, UMExtension
Unlike honey bees and bumble bees which are social insects, andrenid bees are solitary so there is only one bee in a nest. But they are gregarious which means that there are many nests in a small area. They prefer to construct their nests in loose soils, like sandy or sandy loam soils. It is common to find andrenid bee nests on dry sunny slopes or small hills. The nests are somewhat mounded up and can resemble ant nests.

Andrenid bees are important pollinators. Tolerate them
whenever possible. Photo: Jeff Hahn, UMExtension
An andrenid bee is about ½ inch long with a black abdomen (sometime it has bands of hair giving it a striped appearance) and has whitish or yellowish hairs on its thorax (the segment behind the head). They are very gentle, docile insects and are extremely unlikely to sting even when there is activity around their nests. Since they are the only bee in their nest, they do not defend it like social bees and wasps would; they need to avoid being injured or killed so they can maintain their nests and care for their young.

These native bees are very important pollinators and should be tolerated. They are active for several weeks, and then complete their life cycle. They are gone on their own by May so they are only present during spring.

Check Junipers for Disease Damage

M. Grabowski, UMN Extension

Junipers may be tall, upright, and stately, or low creeping shrubs, but regardless of form, many junipers sport dead tips and brown needles in early spring. To determine the appropriate management strategy, gardeners must take a closer look to ascertain the true cause of the damage.

Juniper with brown dead branch tips.  M. Grabowski, UMN Extension
Kabatina blight - Look for brown tips and dead needles on the end of branches. At the point where brown and green tissue meet, the stem is gray and small raised black spots can be seen with a hand lens. This fungal pathogen infects wounds caused by insect feeding or snow load. Branches that are 1 year old are most commonly affected and symptoms are easily seen in early spring before new growth begins. To manage this disease, clip off diseased branch ends on a cool dry day. Burn or bury infected branches.

Raised black spore producing structures of Kabatina blight. M. Grabowski, UMN Extension
Phomopsis shoot blight - Symptoms are similar to Kabatina shoot blight. Branch tips are brown with dead needles. A section of gray stem tissue is seen where the green and brown tissue meet and raised black spore producing structures occur on dead stems. This fungal pathogen infects young growing shoots and symptoms typically appear in summer after new shoots have grown 4-6 inches. To manage this disease, keep foliage dry by using drip irrigation and making sure lawn sprinklers do not wet the foliage. Do not fertilize junipers with a history of Phomopsis shoot blight. Clip off and burn or bury infected branches. If junipers have been infected with phomopsis shoot blight several years in a row, fungicides can be used to protect young green shoots in spring. Some resistant varieties are available.

Gray stem tissue divides healthy green tissue from brown needles in Phomopsis shoot blight. M.Grabowski, UMN Extension

Rodent damage - Although juniper may not seem like a tasty meal to you or I, voles and rabbits have been known to strip bark off juniper stems during winter. Look for dead needles on one or more branches. Follow this branch back into the canopy and look for scrape marks and removed bark along the branches.

Vole damage to stems resulted in dead needles. M. Grabowski, UMN Extension
Removed bark and teeth marks in the wood clearly indicate vole feeding. M. Grabowski, UMN Extension
Junipers often tolerate tip death and some branch loss. New growth fills in holes left by killed branches. Unfortunately if disease or wildlife damage is severe the juniper may never recover the desired shape. In this case, identify the cause of the problem and search for resistant varieties to use as a replacement plant.

Monday, April 27, 2015

EAB confirmed in Fillmore County

Jeffrey Hahn, Extension Entomologist

(The following information is taken from an April 24, 2015 news release from the Minnesota Department of Agriculture)

Last Friday, the Minnesota Department of Agriculture (MDA) identified an emerald ash borer (EAB) infestation in Fillmore County. Fillmore County is the eighth county in Minnesota to confirm the presence of EAB. Additionally, EAB has also been found in Ramsey, Hennepin, Houston, Winona, Olmsted, Dakota, and Anoka (which was just confirmed last month) counties.

Suspected EAB larva and feeding activity consistent with emerald ash borer was found in a boulevard ash tree in the city of Rushford. The infested tree was found through a routine visual survey of ash trees currently being conducted by the MDA. This survey is designed to find EAB in new locations at high risk for EAB infestation.
Verify EAB by finding the larvae or its tunnels
Fillmore County will likely be put under an emergency quarantine this week. The quarantine is in place to help prevent EAB from spreading outside a known infested area. It is designed to limit the movement of any items that may be infested with EAB, including ash trees and ash tree limbs, as well as all hardwood firewood.

Minnesota is highly susceptible to the destruction caused by EAB. The state has approximately one billion ash trees, the most of any state in the nation.
  • The biggest risk of spreading EAB comes from people unknowingly moving firewood or other ash products harboring larvae. There are three easy steps Minnesotans can take to keep EAB from spreading:
  • Don’t transport firewood. Buy firewood locally from approved vendors, and burn it where you buy it;
  • Be aware of the quarantine restrictions. If you live in a quarantined county, be aware of the restrictions on movement of products such as ash trees, wood chips, and firewood; and,
  • Watch your ash trees for infestation. If you think your ash tree is infested, go to the MDA EAB page and use the “Do I Have Emerald Ash Borer?” guide.
For more information about EAB, see the University of Minnesota Extension publication, Emerald ash borer in Minnesota.

The original MDA news release can be found here.

Thursday, April 16, 2015

How to find help with a home landscape

Home owners often ask Extension how to find a student, a Master
Gardener, or an industry professional to help them with a home landscaping project or garden design.  They wonder if students need projects, if Master Gardeners can do this kind of activity for their volunteer hours or how to choose a landscape professional.

Landscape professionals typically have a degree in landscape design or a related area, and /or are licensed as a landscape architect. Some garden centers offer full service landscape design, implementation and maintenance services. Homeowners can also find firms by searching the Minnesota Nursery and Landscape Association website. Use the search function to find the type of help you are looking for in your geographical location; for example, "landscape designer St. Paul, MN". Word-of-mouth is also a very good way to find a landscape professional. When you see a landscape you love, ask the homeowner for a recommendation.   

To reach students looking for seasonal work or alumni in the landscape business, post a job description on GoldPass: Job, Internship and Volunteer Listings. GoldPASS is the U of M's online database to help connect students and alumni with employers, volunteer organizations, and internships across the country. Posting is free, easy to do, and open to anyone.

Homeowners may also choose to send a job description to the Extension Master Gardener program in your county. Master Gardeners are educated by University Extension, and volunteer by teaching the general public research-based horticulture information. While Master Gardeners are volunteers and are not allowed to accept payment or work on private properties as part of their volunteer hours, some are professional gardeners, designers or landscape architects by trade. A county program may have a website or newsletter for volunteers only where such job postings can be made available.

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