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Friday, July 22, 2016

What to do about Japanese beetles

Jeffrey Hahn, Extension Entomologist

Japanese beetles have taken a lot of people by surprise by their abundance this summer, especially in the Twin Cities. They were numerous in the early 2010’s but a series of very dry summers reduced their populations. Japanese beetle eggs and recently hatched grubs do not survive very well in dry soils. However, we have had more normal precipitation the last few years which has allowed Japanese beetle numbers to rebound. Japanese beetles also started emerging sooner than expected this year as they were first sighted in late June. As a consequence, a lot of people are faced with damaged plants and questions about what they should do now.

One common question people ask is whether their tree will die because of Japanese beetle feeding. If the tree is healthy and mature, the tree is not going to die in one year from Japanese beetle feeding. Trees are quite resilient and can tolerate a lot of defoliation.

It is actually easy to kill a Japanese beetle but it is when they are so numerous that it is challenging to manage them so their damage is at acceptable levels. Physical removal is a good option, although it is a labor intensive method; plus if you are trying to protect a tree you will only be able to reach so high to get them. However, this is the best non-chemical option.
Although this linden does not appear to be to
be healthy, it will not be killed by Japanese
beetle feeding and will recover.  Photo:
Jeff Hahn, UMN Extension

Another non-chemical method that people consider using is Japanese beetle traps. While they can capture an impressive number of beetles, it is not likely to protect your garden. In fact, research has shown that when these traps are used in home gardens, you are more likely to see more damage as the traps attract more Japanese beetles than they can capture.

There are a few low impact insecticides available. Pyrethrins are effective but this product has no residual and beetles have to be hit directly by the spray. It also needs to be reapplied more than once. Neem oil is also an option. It helps to deter Japanese beetles but is less effective when large numbers are present. Both of these products can be toxic to pollinators so be sure to apply them when bees are not active.

There are residual insecticides that you can use, like permethrin or carbaryl (Sevin). To protect bees, you need to apply insecticides during late evening after bees are not active. The products should dry by morning when the bees become active again. If you are trying to protect a large tree, you may need to have it treated by a landscape or tree care company.

Deciding whether to treat trees and other plants will depend on how much of the leaves is still intact. If nearly all of it is already chewed up, then spraying does not help them. If there are still a lot leaves that are not affected yet, then it is worth your while to go ahead treat.

Some people wonder whether they should treat the grubs in their lawns to reduce the adults. However, this is not effective. The adults are very mobile and can easily fly onto your property from adjacent areas. Only treat your turf if you are seeing turf damage. The best time to treat preventatively is about the time Japanese beetles are laying eggs which late June or early July. You can treat curatively into August. There are a variety of products that can be used. Insecticides containing chlorantraniliprole (e.g. GrubEx) can be used both curatively and preventatively.

Friday, July 15, 2016

Dealing with Wind-Damaged Trees



Kathy Zuzek, Extension Educator

High straight-line winds and tornadoes have been all too common in Minnesota in June and July. If trees on your property were damaged during these storms, you may be wondering whether to salvage them and how to salvage them. Here are some considerations.

Safety always comes first!
  • As you start to assess tree damage, check for any downed power lines. Stay away from any power lines and call 911. 
  • Check tree canopies for hanging large limbs that may drop to cause injury. If they are present, call a professional arborist

Assess the damage to determine if your tree should be salvaged. Many factors play into this assessment:

  • Health of the tree prior to wind damage: If previous issues – unattractive habit, poor health from diseases, decay, insects, soil problems, salt damage, etc. – were already present before the wind damage, you may want to remove and replace your tree. 
  • Windthrown trees with roots ripped out of the ground: This usually occurs on larger trees because of some already-present root defect. Larger trees are not salvageable. Smaller trees less than 25’ in height may be salvageable. Uprooted trees should be straightened, replanted and staked immediately after the storm so that root desiccation is avoided. More information on staking can be found here
  • Leaning trees are hazardous and should be removed.
  • Trees with major trunk failure, such as large noticeable cracks and snapped off canopies should be removed. 
  • Canopy condition: Were large structural limbs broken off? How much of the canopy is left? If more than 50% of the canopy was damaged, the tree should be removed. 
  • How will the tree look in the landscape after pruning to correct wind damage? Is the tree too damaged for it to be an asset in your landscape? If so, consider removing and replacing the tree. 
  • If you are unsure about retaining or removing your tree, seek the advice of a professional arborist.
Determine how much of the corrective work you are capable of doing: 
    Never prune through a branch collar
     or a bark ridge.Graphic credit:  U of M
     Extension
  • Consider safety factors again! Ask yourself if you are experienced enough to handle all of the pruning work ahead of you. If corrective measures require a chainsaw, removal of large overhead branches, working off the ground and in the tree canopy, or removal of trees or branches near electrical lines or structures, consider hiring a professional arborist with the expertise to do this work safely. Also check your tree for bent and twisted branches that may be under pressure. Removal of these branches can be dangerous as a sudden release of pressure can cause a sudden and unpredictable kick back. 
Use proper pruning techniques:

The last thing you want to do is create more problems for your damaged tree. Poor pruning cuts serve as entry points for decay: Jagged storm wounds on branches are slow to heal and allow decay to enter. Remove these wounds with a clean pruning cut.
Don't leave branch stubs.
Photo credit:  K. Zuzek
  • Never cut through a branch collar (the swollen base found on some branches) or a bark ridge (a horseshoe-shaped raised bark ridge formed at a branch and trunk union and extending down both sides of the branch/trunk juncture) during branch removal. 
  • Never leave long branch stubs. 
  • Damaged branches that are long and/or heavy should be removed with a 3-step removal cut to prevent bark stripping below the cut. 
  • Wound dressings should not be applied as they usually do more harm than good. There is one exception. Wound dressing applications should be made to fresh pruning cuts on oaks if pruning occurs from April through mid-July in areas where oak wilt is a problem. This deters the insects that spread oak wilt when they feed on fresh wounds such as pruning cuts.
3-step removal.  Graphic credit:  U of M Extension
Bark stripping.  Photo credit:  K. Zuzek

Thursday, July 7, 2016

From the DNR: Advice for dealing with storm damaged trees

Reprinted from the MN DNR - July 6, 2016


Cleanup following a storm can be an overwhelming task for homeowners. Knowing which trees to save and which to remove can impact safety and the survival of remaining trees, according to the Minnesota Department of Natural Resources.

DNR forestry outreach specialist Jennifer Teegarden offers the following tips.


Do:

  • Approach damaged trees with caution. Stay clear of downed wires and call 911.
  • Carefully inspect standing trees for damage and deal with hazardous trees first. If possible, ask a forester or arborist for advice.
  • Trees should be removed if more than 50 percent of the trunk or live branches in the crown are damaged, and if the tree is unnaturally leaning or roots are damaged.
  • Watch for detached branches, loosely hanging branches and split or cracked trunks that can cause injury or further damage.
  • Use proper pruning techniques to remove broken limbs by cutting just outside the branch collar, but limit pruning to making the tree safe. Too much pruning can weaken an already stressed tree.
  • Water stressed and damaged trees weekly to help them repair and rebuild. Be careful not to overwater, especially in heavy clay soils.
  • Monitor damaged trees in upcoming years to make sure they don’t become a hazard.
Don’t:
  • Be rushed by promises of bargains from inexperienced or unqualified tree service providers. Improper pruning or unneeded removal can result in unnecessary costs or loss of healthy trees. Ask for references and proof of insurance.
  • Repair a broken branch or fork of a tree with tape, wire, bolts or other wraps. It will not heal, and the split will invite decay and further weaken the tree. Cabling or bracing should only be performed by a certified arborist and inspected annually.
  • Remove the tops of trees. This makes the tree more susceptible to insects and disease, and results in new branches that are weakly attached.
  • Apply paint or dressing to wounds as these materials interfere with the natural wound sealing process.
  • Remove small, leaning trees. Trees less than 15 feet tall may survive if they are gently pulled back into place. Press out air spaces in the loosened soil. The tree can then be staked for up to a year.
  • Fertilize stressed or damaged trees.
Information on tree care, proper pruning techniques and handling damaged trees is available on the DNR website at www.mndnr.gov/treecare/maintenance/stormdamage-prevention.html

For more extensive information on tree care, contact a DNR forester, city forester, certified arborist or county Extension staff.

Take the right steps to correct damaged trees so they can continue to provide shade, clean air, beauty and increased property value for many years to come.

Friday, July 1, 2016

Prevent Blossom End Rot

M. Grabowski,  UMN Extension

The current warm, dry weather combined with fast growing tomato plants creates ideal conditions for blossom end rot, a common problem in garden tomatoes. Fruit affected by blossom end rot have a tan to black, flat, leathery area on the bottom (blossom end) of the fruit. 

Fungal spores may be visible on the discolored area and rot may extend into the fruit, but this problem is not caused by a pathogen.  Blossom end rot is the result of a calcium deficiency in the growing tomato fruit. Any bacteria or fungi present are secondary organisms, taking advantage of the weakened fruit.

Although blossom end rot is caused by a calcium deficiency in the fruit, it does not mean that there is a lack of calcium in the soil. Often blossom end rot occurs as a result of several cultural or environmental factors that affect the plant’s ability to take up calcium. Fluctuations in soil moisture, heavy applications of nfertilizer, and injury to roots can all predispose tomato plants to blossom end rot.



Although symptoms may not yet be visible, now is the time for gardeners to take steps to prevent blossom end rot.

  1. Keep the soil around the tomato plant evenly moist but not waterlogged.  Do not allow the soil to completely dry out between watering. Fast growing tomato plants use lots of water on a hot, sunny day. Mulch the soil with straw, wood chips, or plastic mulch to reduce moisture loss. Touch the soil to determine if it needs water. Soil type, exposure to sun and wind, and plant size will all affect how frequently a tomato plant will need to be watered. Potted tomato plants may need to be watered more than once a day. 
  2. Do not over apply fertilizer to tomato plants with young growing fruit. Excess fertilizer results in quick growth spurts that can increase blossom end rot. In addition, many of the nutrients in fertilizers compete with calcium for uptake by the roots. Tomato plants do not need fertilizer with phosphate or potash at this time, but can be fertilized with 0.15 lb/100 ft2 of nitrogen if needed. Garden fertilizers will list three numbers on the label. These numbers represent that amount of nitrogen – phosphate –potash in the fertilizer. A fertilizer containing only nitrogen will have a number followed by two zeros (16-0-0). Follow the instructions on the package to apply the appropriate amount. 
  3. Avoid injuring tomato roots. Do not dig in the soil within 1 foot of the stem. 
  4. Some varieties are more susceptible to blossom end rot. If severe blossom end rot occurs regardless of good cultural practices, consider using a different variety next year.

Do not give up on the tomato plant if blossom end rot does occur. Often the first fruit are the most severely affected. Fruit produced later in the growing season may not have blossom end rot at all.

Fruit with blossom end rot can be eaten if the rotten part is cut out and the fruit is cooked. Any type of rot can affect the natural acidity of the tomato fruit. As a result, tomato fruit with rot should never be used for canning because the natural acidity plays an important role in keeping out harmful microorganisms. The fruit can be cooked and eaten, cooked and stored, or frozen, cooked and eaten.

Monday, June 27, 2016

Water Wisely: Five steps to conserving water in your garden



By Robin Trott, Extension Educator - Douglas County, MN and Julie Weisenhorn, statewide Extension Educator
2016 is the year to water wisely! From container plantings to lawns and gardens, in 2016, the Consumer Horticulture Team at University of Minnesota Extension are working statewide to help landowners use their water resources wisely. Excellent new Extension resources for gardens, trees and shrubs, and lawns can be found here: http://www.extension.umn.edu/garden/yard-garden/watering/
Five easy steps to conserving water in your yard and garden
1. Water thoroughly after planting, then water once or twice a week, applying enough water to wet the soil to a depth of 12-18 inches for trees and shrubs or 6-8 inches for annuals. If you're not sure how much water this is, do this easy test. Water your garden, wait an hour or so to allow the water to sink in, then dig a hole about 1 foot deep. Is the soil moist at the bottom of the hole? If not, water more. If it is sopping wet, water less.
2. Water your garden in the morning and containers in the afternoon. Research shows that containers watered after noon outperformed plants that were watered in the early morning. The optimal watering time for the rest of the garden is early morning before the temperatures start to rise. Avoid evening watering, as this can lead to fungal growth.
3. Mulch, mulch, mulch. Up to 70 percent of water can evaporate from the soil on a hot day. Mulch is one of the best moisture holding tools you can use. Use coarse mulch at a depth of 3-4 inches. Rock mulch might look pretty, but in full sun, rocks can heat up the soil.
4. Xeriscape. Select plants that are drought tolerant. Many of these plants require less water throughout the season. One way to tell if a plant is a good choice for your xeriscape is the color of its foliage. Plants with silvery foliage, such as many of the herbs, are almost always drought tolerant. Some examples of these are the Artemisia, catmint and Perovskia (Russian sage). Other drought tolerant flowering perennials include black-eyed Susan, Rudbeckia; butterfly weed, Asclepias; and obedient plant, Physostegia. For more information, visit www.arboretum.umn.edu/droughttolerantplants.aspx.
5. Increase organic matter in your soil. Organic matter absorbs many times its own weight in water, which is then available for plant growth. One of the easiest ways to build organic matter is to add compost that breaks down to humus. This has an amazing potential to hold moisture, nutrients and build soil health. It has a buffering effect against drought and plant stresses too.

Friday, June 24, 2016

Watch for lecanium scale

Jeffrey Hahn, Extension Entomologist

Lecanium scales, Parthenolecanium spp., have been commonly reported this year on a variety of hardwood trees, including oak, crabapple, ironwood, hickory, and maple. Look closely for them as appear as 1/8 inch reddish brown helmet shaped insects. They are typically clustered together along branches. Adults are covered by a waxing shell and move very little while newly hatched scales, called crawlers, are mobile but lack the waxy covering.
Lecanium scales. Photo: Dan Potter, Univ. of Kentucky

Scale insects use piercing-sucking mouthparts to feed on sap in the phloem layer of plants. The damage caused by this feeding varies. In most cases, especially on large healthy trees, little to no damage occurs. As scale infestations grow larger and more persistent, branch dieback can occur, and under extreme situations, plant death. Soft scales, like lecanium scale, are also prolific honeydew producers. Honeydew is a clear, sticky waste material. Its presence in a landscape can be very annoying.

There are several options for management. In most cases, trees can tolerate lecanium scale feeding and should be ignored. There are a variety of predators and parasitic insects that help minimize scales numbers. But they need time to build their numbers so patience is necessary.

However, if scale numbers are building too quickly and it is necessary to use insecticides to reduce their numbers, there are some options. It is important to know that direct insecticide treatments are not effective against adult scales because of their waxy covering. Instead, they are most vulnerable in the crawler stage. Different scale species hatch at different times of the year. Lecanium scales hatch in June and July and are vulnerable to insecticide sprays at that time.
Branch dieback on an ironwood due to
lecanium scale feeding.  Photo: Jeff Hahn,
UMN Extension

If you want to ensure crawlers are present before treating, there are a couple of methods for detecting scale crawlers. First you can shake an infested branch over a sheet of white paper or a paper plate and watch for tiny yellowish colored actively moving insects. If you see insects with wings, they are not crawlers. You can also place double-sided sticky tape around infestation and they check the tape for signs of crawlers.

Once you know crawlers are present, you can consider different insecticide options. If you want to use a low impact insecticide to protect natural enemies, consider insecticidal soap or horticulture oil. Both have to cover the crawlers directly as there is no residual. Repeat applications may be necessary. Horticultural oil can also be sprayed during late winter as a dormant application. There are also a variety of residual insecticides, such as permethrin, that can also be used if management is desired.

For more information about scales, including lecanium scale, see Scale insects on Minnesota trees and shrubs.




Thursday, June 23, 2016

Spotted wing Drosophila now active

Jeffrey Hahn, Extension Entomologist

If you grow raspberries, blueberries, blackberries, cherries, strawberries, or other soft-skinned fruit, beware that spotted wing Drosophila (SWD) has been detected. They were first discovered in apple cider vinegar traps in several locations in the Twin Cities on June 13. This is about two weeks earlier than they have been detected the last several years in Minnesota.
Male spotted wing Drosophila.  Note the dark spot near the
tip of the wing.  Photo: Bob Koch, UMN Extension

This small fly has become a very damaging pest in both commercial fields and home gardens. The larvae tunnel into ripening fruit causing brown, sunken, soft areas in the fruit, rendering them inedible. If you have susceptible fruit in your garden, monitor for SWD to determine if this insect is present in your garden. The adults look just like a typical fruit fly that you might find in your home except males have a dark spot on the tip of the wings.

If you find SWD in your garden, it is necessary to protect your crops with an insecticide application. There are several products to choose from; be sure that the specific product you wish to use is labeled for the fruit you want to treat.  Repeat applications will be necessary as SWD is active throughout the summer.

For more information on spotted wing Drosophila, including management, see Spotted wing Drosophila in home gardens.




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