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Extension > Yard and Garden News > Archives > June 2012 Archives

June 2012 Archives

June 15, 2012 Issue

Brace For Impact: Japanese Beetles Are Coming!

Jeffrey Hahn, Asst. Extension Entomologist

The moment many people have been dreading has arrived - Japanese beetle (JB) are starting emerge. It is not necessary to panic as they are not out in force yet. There have been a few individuals that have been found early (normally JB is not out until the first week of July). However, you know the rest are not too far behind. In fact with the recent rains, we could be seeing large numbers will probably emerge within a week or less.

JB is a pest because the adults feed on the leaves and flowers of many plants while the grubs feed on the roots of turf grass. If you have seen JB grub damage in the past, July is a good time to treat your yard. Use a preventative insecticide, like imidacloprid, after you see adults flying, about late June or early July this year. By the time eggs are laid and grubs hatch, about two to three weeks, the insecticide will be taken up by the grass and the young grubs will be exposed to it.

As the grubs get older they are less affected by preventative insecticides. It is still possible to control them with a curative insecticide, such as trichlorfon (e.g. Dylox). You can effectively treat JB with a curative insecticide until about mid-August. Remember to only treat the grubs if you are experiencing problems in your lawn. It is not effective to treat grubs to reduce the number of adults that are seen in your garden. Adult beetles are good fliers and can easily fly into your yard from the surround neighborhood.

Jeff Hahn

Photo 1: Japanese beetle damage on linden

You have a variety of options for managing the adults, including handpicking, low impact products like Neem and pyrethrins containing PBO, and residual insecticides, like permethrin and carbaryl (Sevin).

Another option is the use of a systemic insecticide, like imidacloprid (various trade names) and dinotefuran (Safari). They 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 plants, like linden and roses, that are very 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 important consideration is that it takes some time, especially for imidacloprid, for the tree to translocate the insecticide (3- 4 weeks for large trees). If you have plants that have been plagued by JB in the past, now would be a good time to treat them with a systemic so the insecticide can protect them before much damage is inflicted.

For more information see Japanese beetle management in Minnesota.

Spots, Bands and Browning on Conifers

Michelle Grabowski, UMN Extension Educator

M.Grabowski, UMN Extension

Photo 1: Dothistroma Needle Blight on Mugo Pine


A wide variety of fungal diseases have been reported on pines, spruce and junipers this spring. Fungal needle blights may start out as a spot. As the infection continues the spot grows into a band that completely encircles the needle. Eventually all of the needle tissue beyond the infection dies, resulting in needles that are green at the base and brown at the tip. In other infections, the entire needle or the entire shoot is killed and turns brown.

It is important for gardeners to identify exactly what fungus is causing the problem on their conifer before attempting to control the disease. Each fungus infects different parts of the plant at a specific time of year. Control practices must be precisely timed in order to be effective.




M. Grabowski, UMN Extension


Photo 2: Kabatina TIp Blight on Juniper



The University of Minnesota Extension webpage has an online diagnostic tool called 'What's wrong with my plant?' that helps gardeners identify the pest that is affecting their tree. The diagnostic tool contains photos and descriptions of common pest problems in Minnesota. For each pest problem a link for more information will take the gardener to a publication with more information about pest biology and management options.

Karl Foord - Extension Educator, Horticulture

Swamp Milkweed (Asclepias incarnata) as you know is an important plant for Monarch Butterflies. The plant also produces significant amounts of nectar and thus attracts a host of other pollinators including various bees and ants (Photo 1).

Karl Foord

Photo 1: Milkweed flower (Asclepias incarnata)

On close examination the flower structure is bizarre. Typical corollas face backward (Photo 1), whereas prominent coronas fold to form a tube of sorts out of which a horn projects toward the center of the flower. The stamens have fused to form a cylinder around the pistil with a pink stigmatic surface in the center (Photo 2).




Karl Foord


Photo 2: Milkweed flower (Asclepias incarnata) close-up of unpollinated flower


Pollen has fused to form wings called pollinia which are connected by a dark pollinarium gland, the whole structure being called a pollinarium. You can see the wings protruding from the side of the fused staminal column (Photo 2). The strategy is for an insect to visit the plant looking for nectar and catch its leg on one of the pollinia wings which detaches from the plant and attaches to the insects leg. The insect carries the pollinarium to another flower where the horn may help in detachment placing pollen on the stigmatic surface.




Karl Foord


Photo 3: Milkweed flower (Asclepias incarnata) close-up of pollinated flower



I took many pictures hoping to find an insect with a pollinarium attached to its leg. Alas I did not find one. However, I did find pollinarium that had been transferred from another flower. They can be seen in Photo 3 where the top center section has three pollinarium and the top left section has two pollinarium where originally each had only one.

Megarhyssa, a Large Ichneumonid Wasp

Jeffrey Hahn, Asst. Extension Entomologist

A large wasp has been noticed in the landscape recently. This insect is a type of ichneumonid (ich-new-MON-id) wasp known as Megarhyssa (meg-a-RISS-uh). Megarhyssa is a reddish brown and yellow insect (another species is black with an orangish head) with a body length of about one and half inches long. That does not include it ovipositor which is another two to three inches long (that's up to over four inches total length!). In addition to the ovipositor, you will find two sheaths protecting it which sometimes gives the appearance that it has three 'tails'. Sometimes Megarhyssa is confused for other large sized insects, e.g. mayflies or dragonflies, so look closely to be sure it correctly identified.

Winnifred Williams

Photo 1: Megarhyssa ovipositng in a tree. Note the long ovipositor

Ichneumonid wasps are parasitic upon other insects. Megarhyssa is a parasite of horntails. Horntails attack dying or recently dead hardwoods, such as oak, maple, birch, and elm. With her long ovipositor, Megarhyssa can drill 1/2 inch or more into the wood to deliver an egg into the horntail larva. When people see this ichneumonid wasp ovipositing into a tree, they believe that it is attacking it. Of course, this is not true. Once the egg hatches, the Megarhyssa larva slowly feeds on the horntail, eventually killing it. After it matures into an adult wasp, it emerges from the tree.

Despite her large size and her menacing ovipositor, ichneumonid wasps, like Megarhyssa, pose no threat to people. They are not aggressive and avoid us when possible. It is possible that if someone handled a Megarhyssa, she could try to jab you with her ovipositor if she felt threatened but she could only inflict a minor wound at best.

If you see Megarhyssa, just ignore her. Any that you find will go away on their own in a short time. It is never necessary to treat them with an insecticide.

Karl Foord - Extension Educator, Horticulture

Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture


Rhubarb (Rheum rhabarbarum)

Karl Foord

Photo 1: Rhubarb (Rheum rhabarbarum)

Chives (Allium schoenoprasum)

Karl Foord

Photo 2: Chives (Allium schoenoprasum)


Common Thyme (Thymus vulgaris)

Karl Foord

Photo 3: Common Thyme (Thymus vulgaris)

Horseradish (Armoracia rusticana)

Earwigs: Pests of Homes and Gardens

Jeffrey Hahn, Asst. Extension Entomologist

Jeff Hahn

Photo 1: Earwig found outdoors in garden. Note the second earwig hiding in the crack between the pavers

Earwigs season is beginning as immature nymphs are starting to turn into adults. They are pests when they enter homes, often in large numbers, and become bothersome. They can also damage flowers and other plants in your garden. Earwigs can be challenging to control, especially when they are abundant. Here are some steps you can take to minimize them on your property.

Regardless of whether you are dealing with them in your home or garden, you can reduce their number by using traps in the landscape. Use rolled up newspapers cardboard tubes, or similar objects and set them up outside where you are see earwigs. They will crawl inside these objects by early morning in order to hide. You can then shake them into a pail of soapy water to dispose of them.

Moisture management is also important. Minimize excess moisture by keeping irrigation equipment in good working order. If you need to irrigate your garden, water less frequently but more deeply so the soil remains more dry, making it less conducive for earwigs.

Phil Pellitteri

Photo 1: Earwig found indoors. Has any friends joined him?

If you are having a problem with earwigs in your garden, you can supplement your non-chemical efforts with an insecticide. You can treat the mulch with insecticide, e.g. lambda cyhalothrin, or put out chemical baits, e.g. carbaryl, around the affected plants. You can also treat affected plants directly with any one of a variety of garden insecticides, e.g. permethrin.

If you are having a problem with earwigs coming into your home, check around the outside of your home and seal or repair any openings or gaps you find that allows earwigs to get inside. Check particularly around the foundation, windows and doors. Also examine where siding and foundation meet as well as the areas around water facets and vents. You can supplement this with an insecticide application around the exterior the home, e.g. permethrin or cyfluthrin.

June 1, 2012 Issue

In this issue of the Yard and Garden News:

Cold Wet Soils Help Root Rotting Fungi

What Kind of Moth Was That?

Flowering Plant Video Library - Peonies

Fern Leaf Peony (Paeonia tenuifolia 'Little Red Gem')
Tree Peony (Paeonia suffruticosa 'Guardian of the Monastery')
Common Garden Peony (Paeonia lactiflora 'Chalice')
Garden Peony Growing Recommendations

Forest Tent Caterpillars at End of Feeding

Flowering Plant Video Library - Lilacs

Dwarf Korean Lilac (Syringa meyeri)
Miss Kim Korean Lilac (Syringa pubescens subsp. patula 'Miss Kim')
Lilac Fasciation (crested growth form)
Many Types of Lilacs at the Arboretum

Cutworms Gone Wild

Cold Wet Soils Help Root Rotting Fungi

Michelle Grabowski, UMN Extension

H. Schwartz, Colorado State University, Bugwood.org

Photo 1: Onion seedlings suffering from root rot

Although spring came early in Minnesota this year, recent cold wet weather throughout the state is reminding many gardeners that summer is not here just yet. Many perennial plants, trees and shrubs have been leafed out for weeks now. However, gardeners should remember that when starting warm season vegetables from seed in the garden, it is important to wait for soils to warm up. Pumpkin, cucumber and squash seeds like soils that are 65F at a 2 inch depth. Melons prefer soil temps of 70F or above. Sweet corn seeds germinate best when soils are between 55 and 60F. Soil temperatures are measured weekly by the UMN Climatology group at several sites across Minnesota and can be viewed online.

Seeds planted into cold soils may sit and wait or may germinate but grow very slowly. In these very early stages of life, seedlings are highly susceptible to soil borne pathogens that cause root rot and damping off. Gardeners may notice that seeds are failing to emerge from the ground or that young seedlings emerge and then yellow and fall over. Older plants may become stunted by root rot. Leaves may wilt and dieback. The recent excess of heavy rain in many areas of the state has created ideal conditions (cool, wet soils) for these root rotting pathogens. Several cases of seedling damping off and root rot of young plants have been reported.

Dept. of Plant Pathology Archives, North Carolina State University, Bugwood.org

Photo 2: Impatiens transplants suffering from root rot

To prevent these early season root rotting pathogens, wait to plant warm season vegetables until soils have warmed to the recommended temperature and are moist but not heavily wet. In some areas of Minnesota, it may be necessary to start seeds indoors and transplant them into the garden when outdoor conditions improve. In addition many simple structures like cold frames and walls of water can help warm soils and protect plants. Black plastic mulch also warms soil in the root zone. By growing plants in a raised bed, gardens have improved drainage even in wet weather.

Seeds coated with a fungicide treatment will be protected at the earliest stages of growth. For gardeners that choose not to use treated seed, waiting until soil warms up to the appropriate temperature or using the techniques listed above to heat soil and improve drainage can be just as effective in preventing early season root rot.

What Kind of Moth Was That?

Jeffrey Hahn, Asst. Extension Entomologist

Terry Straub

Photo 1: Hummingbird moth (hummingbird clearwing)

There has been a variety of curiosity questions received recently about interesting moths. Several people have reported seeing hummingbird moths (also called hummingbird clearwing), Hemaris thysbe and/or bumble bee moths (also called snowberry clearwings), H. diffinis, in their gardens. These moths, a type of sphinx moth, are daytime flyers. They have relatively small, stout bodies and their wings are mostly clear, lacking scales on them. They fly like hummingbirds, deftly hovering and flying around flowers as they visit blossoms for nectar. 

You can distinguish between them as hummingbird moths are little larger with a wingspan of about two inches. They have a yellowish body and the borders and veins of the wings are reddish brown. Bumble bee moths are a little smaller with an average wingspan of about 1 ½ inches. They have a yellow and black body with black veins and a narrow black band on the edge of the wings.

Another sphinx moth that has been noticed lately is the whitelined sphinx moth. It is a large moth with a wingspan between 2 and 3 ½ inches. The first pair of wings are dark colored with a large white stripe running from the wingtip diagonally to the base of the wing and six smaller white lines crossing it. The second pair of wings is dark with a pinkish band. This moth is active at dusk as well as at night. It also flies around flowers like a hummingbird.

Terry Curtis

Photo 2: Whitelined sphinx moth

Later their larvae may be found in gardens feeding on evening primrose, grape, plants in the Rosaceae (rose family), and other herbs and woody plants. This caterpillar grows to be as large as three inches long with a distinctive horn on the end of its body. Most are green with black stripes and yellow and orange markings, although some are mostly black with some greenish yellow. 

Two giant silkworm moths may be seen now. Both species overwintered as cocoons and started to emerge during late spring. The cecropia moth is reddish brown with a wingspan of five to six inches. The polyphemus moth is a brown moth with a large blue and yellow eyespot on each hind wing. They will produce caterpillars that will become large and conspicuous by late summer and early fall as they feed on the leaves of a variety of hardwood trees.

The cecropia caterpillar grows up to 4 inches long. It is light green with a double row of reddish orange knobs (turbercles) on the thorax behind its head. There are also series of smaller yellow and blue knobs (turbercles) on the abdomen. The

Jeff Hahn

Photo 3: Cecropia moth

polyphemus caterpillar grows to be about 3 1/2 inches long when fully grown. It is a pale green with sparse long hairs along the top and sides of the abdomen. 

Karl Foord - Extension Educator, Horticulture

Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Fern Leaf Peony (Paeonia tenuifolia 'Little Red Gem')

Tree Peony (Paeonia suffruticosa 'Guardian of the Monastery')

Karl Foord

Photo 1: Guardian of the Monastery Tree Peony

Karl Foord

Photo 2: Guardian of the Monastery Tree Peony


Common Garden Peony (Paeonia lactiflora 'Chalice')

Karl Foord

Photo 3: Common Garden Peony 'Reward'


Garden Peony Growing Recommendations

Forest Tent Caterpillars at End of Feeding

Jeffrey Hahn, Asst. Extension Entomologist

If you are thinking about treating forest tent caterpillars, check their size because the odds are it is too late to treat them any more this year. If they are between 1 3/4 - 2 inches long, they are either finishing or are done with their feeding. Forest tent caterpillars, sometimes called (incorrectly) armyworms have been active since mid to late April and typically feed 5 - 6 weeks. The best time to treat them is when they are half full grown size, or about one inch long.

Gail Felton

Photo 1: Nuisance forest tent caterpillars crawling on home

Older larvae can cause problems by coming down from trees and wandering around looking for food. Sometimes they can severely damage nearby plants, including those in gardens. Other times, they are annoying when they crawl onto homes, sidewalks, decks, patios, outdoor furniture, and other objects. They may even pupate on homes and other things, further being nuisances.

They are difficult to deal with, especially when they are abundant. You can try to create a barrier with an insecticide, such as permethrin (be sure any insecticide you use is labeled for the area or plants you intend to treat). Otherwise use physical removal (avoid crushing the caterpillars if possible when they are homes). It is likely you will need to be persistent as effective physical removal is often time consuming. 

Click here for more information on forest tent caterpillars.

Plant Video Library - Lilacs

Karl Foord - Extension Educator, Horticulture

Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Dwarf Korean Lilac (Syringa meyeri)

Miss Kim Korean Lilac (Syringa pubescens subsp. patula 'Miss Kim')

Lilac Fasciation (crested growth form)

Many Types of Lilacs at the Arboretum

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