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Yard and Garden News

More Apple, Less, uh, Protein

Each year we strive to produce apples free of apple maggot damage, a challenge to many backyard gardeners. The good intention of spraying the trees at the beginning of the season soon fades as we get busy enjoying our short summer. The next thing we know it is time to harvest our apples only to find the quality has diminished due to apple maggot damage.

To protect the fruit from the apple maggot we have found that bagging the apples has resulted in near perfect fruit. Testimonials from homeowners who have used the practice indicate that it is the first time many of them have had quality fruit from their trees. They have found the bagging process easy, bagging only as many apples as they expect to use.

The process begins the second or third week of June, a period when the tree is doing some natural thinning of apples. Many homeowners find that is a good time to do further thinning so they have high quality fruit at harvest time.

What's Your Bag?

My experience is that plastic baggies, handy in your kitchen drawer, will provide excellent protection from the apple maggot. My preference is a zip-type plastic bag. On the internet you may find information about using special bags such as the 2-layered paper apple bags used in Japan , but we have had great success with these plain plastic bags.

How to Bag ‘em

Normally one apple is placed in a plastic sandwich bag, although two apples can be placed in one bag. Make sure you do not put any leaves in the bag since they may rot in the bag and stain the fruit. Cut just the tips off of the bottom corners of the baggie so that rain and moisture drain out of the bag.

My procedure is to zip the plastic bag half way across and then slip the bag over the young apple and zip the other half up to the stem. It does not have to be tight against the stem, in fact it should be a bit loose so the stem can thicken. If your trees are in a windy area you may want to consider stapling the zip area next to the stem to prevent the bags from blowing off. The bags will give season-long apple maggot control and free you up from the spraying routine, allowing you to enjoy the summer.

 

Watch for rose chafers , tannish 5/16 to ½ inch long insects with long reddish legs. They are particularly common in areas with sandy soil. Rose chafers feed on the blossoms of roses, peonies, and other flowers. They will also gladly feed on fruit, such as grapes and strawberries, and skeletonize (feed between the large veins of leaves) foliage on other plants, such as roses, birch, and grapes.

Managing rose chafers is challenging. You can try handpicking the beetles and tossing them into a pail of soapy water - this is easier in small gardens. You can protect some plants by erecting a cheesecloth or similar barrier around the plants for as long as the rose chafers are active (until the end of June). You may also elect to use a residual insecticide, such as bifenthrin, esfenvalerate, or permethrin. Be sure the plant you wish to treat in on the label of the specific product you intend to use.

For information see Rose Chafers (http://www.extension.umn.edu/distribution/horticulture/M1198.html)

Apple Maggots are a major pest of apples. The adults damage the fruit when they lay eggs into the apples and the larvae further damage apples by tunneling through the flesh. They spend the winter as pupae in the soil and are active as adults starting about July 1.

There are several methods you can use to protect your apples from this pest. First, consider bagging them (see article this issue). Another non-chemical method is to hang sticky traps, about five in an average sized tree to capture the adult maggots as they try to lay eggs. Bag your apples or set up your traps by July 1.

You can also consider treating with an insecticide. There are not many options available to home gardeners, although carbaryl is available in a few products. Also look for products containing esfenvalerate, although read the label carefully. In one case, the product is limited to treating just dwarf and young apple trees.

There are several different schedules you can follow. Regardless of which schedule you use, do not spray before July 1. One schedule is to treat apples two days after a rain or irrigation of ½ inch or more of water. This is when the adults are most likely to emerge. You can also set up a trap in the tree and spray whenever you have trapped at least five apple maggot adults in one week. Another option is to treat apple maggots on a regular schedule, once every 10-14 days. This method is the most effective, but it also uses the most insecticide.

For more information, see Apple Maggot Management in Home Gardens (http://www.extension.umn.edu/distribution/horticulture/DG1007.html)

Be on the watch for Colorado potato beetles . Both the larvae and adults feed on potato leaves and are active throughout the summer. Handpicking adults and larvae and throwing them into a pail of soapy water is effective, especially for small gardens.

An effective insecticide with low impact to the environment is Bacillus thuringiensis var. tenebrionis . This naturally occurring bacterium is most effective against young larvae. It is less effective against older larvae and has no effect against adult beetles. Other low-impact insecticides that are reasonably effective are spinosad and azadirachtin.

Most synthetic insecticides (carbaryl and permethrin, for example) have little or no effect on Colorado potato beetles because of insecticide resistance. An exception would be esfenvalerate. This is a newer insecticide that does not yet have widespread insecticide resistance.

For more information, see Colorado Potato Beetles in Home Gardens (http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e246potatobeetle.html).

Fourlined plant bugs are still active - expect them to continue feeding until early July. Although they typically don't kill perennials or other plants they attack, they often do affect their appearance. Ignore them when possible. If you wish to protect the plant's appearance, apply a residual insecticide, such as bifenthrin, esfenvalerate, or permethrin. It is less important to treat these insects the closer we get to late June and early July.

For more information, see Fourlined Plant Bug (http://www.extension.umn.edu/projects/
yardandgarden/ygbriefs/e121plantbugs-fourlined.html).

 

Have you noticed a chartreuse glow along roadsides lately? If so, you may be seeing leafy spurge (Euphorbia esula), an invasive herbaceous perennial that spreads rapidly from seeds and rhizomes. Native to Eurasia, this troublesome weed has become widespread in the U.S. and is a particular problem in open rangeland in the Upper Midwest and Northern Great Plains states. Leafy spurge is present throughout most of Minnesota.

The tiny yellow flowers of leafy spurge bloom in June, but that roadside glow is mostly from the bright yellow-green, rounded bracts just below the flowers. The bracts remain showy throughout much of June and July. When the seed capsules mature in late summer they explosively propel the seeds up to 15 feet away.

Leafy spurge is on Minnesota's list of prohibited noxious weeds, which means that landowners are required to attempt to control or eradicate the plant. If caught early, small leafy spurge infestations can be controlled with herbicides such as picloram or glyphosate. Because of its extensive rhizomatous root system, leafy spurge is difficult to control through pulling or digging.

Large leafy spurge infestations are more difficult to treat. One of the most promising long-term management strategies is the use of biocontrol agents. In the case of leafy spurge, the Minnesota Department of Agriculture reports that the most successful biocontrol agents have been several imported species of European flea beetles. These beetles feed almost exclusively on leafy spurge and a few related species. Flea beetles from established populations are actively collected and relocated to leafy spurge-infested sites.

What can you do?

• Be able to identify leafy spurge.
• Work to eradicate infestations on your land.
• Don't move hay cut from infested pastures to other locations.
• If you see infestations on public land, like roadsides, notify local government agencies so appropriate management can begin.

For more information: http://www.mda.state.mn.us/plants/badplants/leafyspurge.htm

 

 

As the late spring rains and cool temperatures change to dry spells and 90 degree days, many gardeners are reminded of the long hot, dry months of the summer of 2006. The new growing season brought renewed growth in our lawns and garden perennials. It is our trees, however, that remind us of last year's drought and the damage it caused.

The Drought Monitor, run by the USDA and NOAA, reported that in August 1, 2006, all of Minnesota was under some form of drought conditions, from abnormally dry in the SE corner of the state to extreme drought in the north central region. These conditions had been building since mid June 2006. Although the southern counties of the state received some relief in September and October, the northern regions of the state remained in extreme drought conditions. By mid-November 2006 the majority of Minnesota was again under unusually dry conditions or worse, and stayed that way into the winter months.

Those who were paying attention to the landscape may have noticed that in addition to lawns turning brown, many landscape plants were wilting. Without sufficient water, leaves began to turn brown at the tips and far edges.

For trees, these drought conditions created more problems than a few wilting, brown leaves. Drought places stress on trees that makes them susceptible to opportunistic pathogens. Often considered weak, opportunistic pathogens are normally unable to infect or cause severe disease in an otherwise healthy tree. In a tree weakened by drought stress, however, these pathogens can be severe and sometimes even fatal.

A perfect example of an opportunistic pathogen is the fungi Nectria cinnabarina . Nectria lives on the surface of many different plants feeding on dead organic matter and residue. This type of feeding does not hurt the plant in any way. Whenever a stress or injury occurs, however, Nectria seizes the opportunity to infect. The fungus quickly moves into the injured tree, colonizing the bark, cambium, and sapwood. Being a true opportunist, Nectria is not picky about what to attack. It can infect over 90 genera of deciduous shade trees and shrubs, as well as a few conifers and even some palms.

Nectria grows unseen underneath the bark, often expanding during the cold winter months when the tree is dormant. These infections can completely girdle and kill the branch. Many gardeners may not realize that the dead branches they are seeing this spring may be a direct result of last years drought combined with an opportunistic pathogen. Infections caused by Nectria cinnabarina can be recognized by small spore-producing structures that push through natural openings and cracks in the bark of the infected tree in spring and early summer. These structures look like tiny cushions and can be pink, pale orange, or cream colored when young, but turn dark brown or black as they age or after they have been exposed to a frost. Later in the summer, smaller orange-red bumps will push through the bark as well. Both of these structures will produce fungal spores that allow the pathogen to spread.

For those trees that are currently suffering from infection by Nectria cinnabarina , much of the damage has already been done. Trees with dead branches should be examined for the cushion like spore producing structures. Dead branches can be pruned out of the tree, but this should be done when conditions are dry. Nectria produces spores in response to rain or other moisture. A pruning cut is an open wound that could easily be infected by these spores. After cutting out dead branches, pruning shears should be cleaned with a 1:10 solution of bleach and water (which can be very caustic to tools) or with a household disinfectant like Lysol or Listerine. Infected trees should not be pruned or fertilized in late summer or fall. This often causes a flush of new growth that is easily injured by winter temperatures and creates a perfect infection site for Nectria.

Providing a stress-free growing season for all trees this year will help avoid future problems with opportunistic pathogens. It's difficult to predict just how much rain will fall this summer, but if drought conditions occur, supplemental watering can help maintain the health of a tree for the current season and on into the future. Newly transplanted trees are especially susceptible to drought stress since their root systems have not had time to become established. For these trees create a 3 to 4 inch tall ring of soil around the root ball area of the new tree. When watering, fill this area with water and allow it to soak slowly into the soil. New trees may need up to 3 inches of water per week (including rainfall), depending on soil conditions.

Established trees - especially drought-intolerant species like sugar maple - may also need supplemental water during drought. For mature trees, use a lawn sprinkler to water the area around the tree. A tree's root system can expand as much as 3 times the width of its canopy and all of that area should be watered. Water until the top 6 to 8 inches of soil is wet. Wait to water again until the top 2 to 3 inches has dried. This type of deep, infrequent watering will encourage trees to develop deep roots that will support them in drier conditions.

Other stresses such as compacted soils, flooding, transplant shock, and planting trees where they are not truly winter hardy can also create an opportunity for a pathogen to start an infection. Wounds from a lawn mower, weed whip or poor pruning practices expose parts of the tree normally protected by the bark. Before planting a tree, learn about what environment it prefers and choose an appropriate location. Once in the landscape, use caution when working around trees to avoid wounds. If drought conditions occur this growing season, help trees out with extra water.

 

 

Deadheading (removing spent flowers) promotes additional blooms on a number of annual and perennial flowers. By deadheading, energy that would go towards fruit and seed development is diverted for other purposes, primarily additional vegetative growth and flowering. Common summer annuals that have an extended flowering period tend to respond favorably to deadheading. Annuals' greatest priority is seed production - they live only one year and need to try to ensure successfully reproduction, so they'll keep putting out new flowers if old ones are removed. In addition, some perennials are also capable of having some or stronger rebloom if spent flowers are removed.

Embryos within forming seeds release hormones that signal their presence. The mother plant responds by diverting energy to the developing embryos and surrounding fruit. Without the hormonal signal from the embryo, the spent flower with its immature ovary (beginnings of the fruit) typically turns yellow, dies, and can fall off the plant. Having a hormonal signal that communicates successful fertilization conserves energy resources for the mother plant so energy is only diverted to fruit with developing seeds. There typically is no benefit for a plant to develop a fruit that does not contain viable seed. Sometimes when there is an abundant crop of fruit that is greater than what the plant can support, fruit with fewer developing seeds tend to abort more readily in the process of natural fruit thinning (this can happen in apples). Fruit with more seeds have more hormone and therefore more potential for perpetuation of the species.

Larger-flowered annuals like geraniums, zinnias, and marigolds typically benefit most from deadheading. Removing their relatively large fruiting structures not only makes the plants more attractive, but also has a stronger impact on reflowering. Smaller flowered annuals like diascia, lobelia and sweet alyssum also reflower better with deadheading, but it can be impractical to deadhead individual spent flowers due to their sheer number and small size. For smaller-flowered species, one can deadhead more aggressively and remove not only the individual flowers, but also the wiry stems carrying spent as well as some fresh flowers in order to encourage new flowering stems to be initiated closer to the base of the plant.

When deadheading, try to cut close to the main stem in order not to leave a long stub behind. Stubs typically turn yellow, die back to the main stem, and may be a source of pathogen entry and disease. To deadhead, use a pruning shears, scissors, knife, or even your fingers. The flower stalks of some plants such as geranium (Pelargonium species) even have a natural swollen base near the main stem that will snap off cleanly just with finger pressure. This makes deadheading even simpler. When using pruning tools, make clean cuts which will then heal quickly.

Many recent cultivars of popular annuals have less need for deadheading in order for them to continue flowering throughout the season. This includes many of the very vigorous spreading or wave-type petunias. They have enough vigor and growth potential to be able to support seed development, yet continue to grow and flower abundantly. In addition, some vigorous foliage plants, have minimal flowering to detract from the production of colorful or otherwise attractive foliage such as some of the solar coleus. Some of the smaller flowering marigolds (dwarf French marigolds such as those in the Disco and Sparky series) and zinnias (Pinwheel and Profusion series) are so well branched and vigorous that new flowers tend to hide spent flowers. Although deadheading can help promote more blooms, it is not essential with some species or cultivars in order to maintain a relatively attractive plant. If you have little time for tasks like deadheading, choose some of these plants that continue to grow and flower well even without deadheading.

Some perennials with a relatively long flowering period can rebloom better if spent flowers are removed such as Jacob's ladder (Polemonium caeruleum), catmint (Nepeta faassenii), and salvia (Salvia nemorosa). Some perennials such as Asiatic lilies, peonies, and daffodils won't reflower even if deadheaded, but removal of spent flowers can produce a more attractive plant and can encourage more energy to be diverted to overwintering structures for a stronger plant the following season.

Additional points to consider with deadheading:

• For some species fruit is very ornamental and deadheading removes developing fruit. For instance, rose hips can be very ornamental and add color to the landscape well into fall and winter. Rose hips typically take about 3 months to mature and turn color. Although deadheading can promote faster rebloom on roses, one will not have rose hips if they deadhead. For other species like purple cone flower, allowing seeds to develop can be useful if one would like to draw birds or other wildlife.

• Deadheading can help circumvent potential weed problems with species that tend to reseed heavily. For instance, although heliopsis will continue to flower nicely without deadheading, volunteer seedlings can become a nuisance and deadheading spent flowers before seeds ripen can alleviate that problem.

 

 

The arrival of hot dry summer conditions can create very stressful conditions for our cool-season lawn grasses. The term “cool-season” refers to the fact that these grasses have peak growth activity during the cooler periods of the year, namely spring and fall.  When rainfall doesn't seem to be forthcoming, one of the best ways to moderate those stressful conditions is through timely, appropriate lawn watering. 

However, we are often confronted with community watering restrictions and our own desires to be good stewards of our water resources, which includes conserving water. While that may seem to run contrary to meeting lawn watering needs, there are different schemes that can be used to ensure lawn survival and even maintain green, actively growing lawns during those stressful periods. 

When the desire or need is to maintain a green, actively growing lawn, you will need to be applying about 1 to 1.5 inches of water every 7-10 days.  Where soils are very hard and compacted, or very sandy, it is usually best to apply about ½ to ¾ of an inch per watering, but do it twice in that same time period. As a general guideline, during hot and windy conditions, the interval between waterings should be shorter due to the increased rate of drying. Remember, the amount of suggested moisture per week includes that received in any rainfall events.

Your lawn grasse s will let you know when they are getting thirsty. When you start seeing areas of a dark, bluish-gray color in your lawn, that is a good ind icator that the lawn is beginning to dry out and some additional water will help ease that stress. In addition, when you walk across your lawn and your footprints in the lawn don't spring back to a vertical position fairly quickly, that is another ind icator of the lawn drying out and would benefit from some additional water.

Where some loss of green color can be tolerated, a thorough soaking (1/2 inch to 3/4 inch) every 7 to 10 days will keep lawns alive. Actually, our grass plants have relatively good tolerance to hot and dry periods, especially where they have been conditioned properly.  Nonetheless, there are limits to that tolerance, especially with many of the contemporary bluegrass and perennial ryegrass varieties that have been introduced over the last several decades.  If the plant gets too dry internally, tissue damage can occur and the plant usually dies.  Again, during extremely hot, dry and/or windy conditions the interval between waterings may need to be shortened.

Finally, those with automated lawn watering systems can increase the amount of time water is applied and put longer time periods between waterings. This can help accommodate community water restrictions such as odd/even address-based watering schedules. 

 

 

It is now possible to see orange leaf spots on hawthorns (Crataegus spp.) and serviceberries (Amelanchier spp.). These infections are caused by the same rust fungi responsible for some of the gelatinous orange stars seen last month on junipers. The leaf spot infections rarely cause serious damage to landscape plants and can be tolerated.

Watch for powdery mildew infections on susceptible garden plants. Minor infections that consist of only a few white spots on a few leaves can be tolerated and don't need to be treated. In plants where leaves are yellowing or falling off because of the powdery mildew infection, treat with sulfur, potassium bicarbonate, chlorothalonil or thiophanate methyl fungicides to protect new leaves. Always read and follow the label instructions before using any pesticide product.

 

 

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Back issues Yard & Garden Line News for the past nine years are online at http://www.extension.umn.edu/projects/yardandgarden/ygline-news.html.

Deb Brown will answer gardening questions as a recurring guest on the Midmorning show on MPR. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

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.

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Happy gardening!

Nancy Rose
Editor
Regional Extension Educator - Horticulture

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