Yard & Garden Line News Volume 2 Number 6                                                              May 1, 2000

Features this issue: Think "Color" When Choosing Flowering Annuals Potato Potpourri Plum Pox, a New Threat to U. S. Stone Fruits Necrotic Ring Spot is Back! New Disease Resistance Information for Honeycrisp and Zestar! Spring Leaf Diseases Beware of Blacklegged Ticks Andrenid Bees Are Active Now White Grub Damage Eastern Tent Caterpillar Is Active Now Watch Out For Cutworms in Your Garden Clover Mites Still Very Common Larder Beetles Now Here's Something You Don't See Everyday Editorial Notes

Think "Color" When Choosing Flowering Annuals
Deborah Brown, Extension Horticulturist

Zinnias.

Hyssop and perilla.

Purple petunias.

Cosmos. Photo credits: Deb Brown

This is an exciting time of year for flower lovers. Nurseries and garden centers will soon be ablaze with color, ready to tempt even the most practical and parsimonious among us to buy more bedding plants than we had planned. If you haven't got your pansies in yet, time's a wasting!

Though it seems obvious, color is an element of garden design that's often overlooked. When choosing garden plants many gardeners tend to focus on the beauty of individual flowers rather than the relationships between groups of flowers. And there's often a tendency towards going for sizzle rather than subtlety, especially with flowering annuals.

One of the nicest aspects of growing annuals is that you can repeat really great combinations year after year, but it's also easy to experiment with new plants and new colors any time you're dissatisfied the last summer's results.... or just for the creative fun of it.

Color choices are a matter of personal taste. But there are some universal characteristics of color that you ought to take into consideration when selecting bedding plants.

Visually, yellow, orange, and red are considered "hot" colors, while green, blue, and violet are considered "cool". Hot colors not only make you feel warmer, they appear to advance towards the viewer. Cool colors appear to recede; they make you feel cooler.

If you have gardens at the very back of your yard, or you want your flowers to be seen from a distance by people driving past your house, choose lots of intense, sunny colors. They're dramatic, and they'll show up well.

Scarlet petunias or zinnias, bright gold or yellow marigolds, and red-orange cosmos or Mexican sunflowers all stand out from quite a distance. So do neon rose-colored impatiens, hot crimson geraniums and tangerine tuberous begonias.

Cool-colored flowers are best viewed close up; they tend to disappear at a distance, particularly the darker shades. You can plant fascinating, nearly-black pansies, but you won't even notice them in the garden unless you're standing almost on top of them.

Petunias, salvia, bachelors' buttons, Chinese forget-me-not, heliotrope, and impatiens are some of the many annuals available in soft shades of blue and lavenders. They lend a cool feeling to the garden, and can be used to create an inviting, restful look on your deck or patio and in other parts of the yard where you'd like a visual oasis from summer's heat.

White or cream colored flowers are neutral, as is the silver foliage found in dusty miller. Take advantage of these colors to separate clashing combinations and help "cool down" unrelieved hot spots.

Some colors take on a life of their own at sunset, as anyone who's grown moon flower will attest. White flowers such as annual baby's breath, petunias, sweet alyssum, and geraniums, are particularly adept at reflecting what little light is available, including moonlight. `Blue Pearl' impatiens and pale lavender New Guinea hybrid impatiens seem to glow with inner light at dusk.

Except for plants you use as edging (dwarf marigolds, lobelias, petunias, sweet alyssum) group bedding plants in clusters to form drifts of color that will have more impact. Save straight rows for corn and beans!

Potato Potpourri
Beth Jarvis, Yard & Garden Line Project Coordinator

Tiny seeds are carefully planted--the first step to finding a new cultivar. Photo credit: Potato Working Group

Talk to almost any potato gardener these days and they'll complain about Colorado potato beetle (CPB).

Ask a potato researcher what to do and, for a small garden setting, he'll say squash them–the beetle egg masses, that is. Dr. Christian Thill, project leader for the U's potato breeding program, says the best control of Colorado potato beetles is to squash the yellow, dime-sized egg masses as they appear on the undersides of leaves. It's easy, organic and an excellent job for kids.

Resistance to CPB is just one of the traits Thill and the interdisciplinary research team, the University of Minnesota's Potato Working Group (PWG), is factoring into their screening criteria of potential new potato cultivars. It's a juggling act balancing desirable market characteristics with disease and insect resistance.

And it's time consuming, because producing a new potato cultivar (cultivated variety) can take 10 to 15 years. Part of Thill's research includes reducing the time it takes to produce new cultivars. Potato breeding program leaders tend to hang around. The Minnesota program started in 1919 and Thill's only the third person to head it. F. A. Krantz and Florian I. Lauer, his predecessors held their jobs 39 and 37 years respectively.

Seeds turn into seedlings. Photo credit: Potato Working Group

The program is the Horticulture Department's largest, based on acreage, as it has over 80 acres planted in 11 sites scattered across Minnesota and North Dakota. The sites have different functions. Several are models of commercial production, one is a certified seed farm and others are trial sites for disease, insect, and frost tolerance. They range in size from 35 acres in Morris for seed potato production to little one-acre patches. Some locations are at research and outreach centers (formerly experiment stations) and some are in grower fields. The research is funded by the U of M College of Agriculture, Food and Environmental Sciences, Red River Valley Potato Growers, Minnesota Area II Potato Research and Promotion Council and US Department of Agriculture grants.

Talking 'Taters

Potatoes are the most important vegetable crop in Minnesota and the North Central region with a "farmgate"(what grower gets) crop value of $453 million The region accounts for 28% of the US potato acreage.

As the most important vegetatively propagated food crop in the world, potatoes rank 4th after rice, wheat and corn in overall importance, world-wide. Potatoes produce more food per acre than any other crop.

Americans eat an average of 143 pounds of potatoes per person per year. Of that 63% is processed as fries, flakes, mashed, starch or flour.

To many of us, potatoes are "russets" or maybe those small reds, known a "B"s in the trade. Actually, there are four types.

Reds are mostly for fresh market and selected for bright red skin color and skin that stays on. Some are very early maturing and some are late maturing and actually sit in the ground a while.

Round whites have two purposes, fresh market and potato chips. Potatoes used in chips must be high in starch and low in sugar. (Sugar turns dark when fried.) High starch means less water. In frying, water is replaced with fat so a high starch potato yields a less oily chip. Rounds whites destined for chips should have shallow eyes, which clean easily, and a blocky shape, for less waste.

Russets are used in processing and fresh market. Desirable traits are the same as the round whites. These also must store 8 to 9 months in commercial storage. The term "russet" technically refers to the potato skin color, however, most people use it to refer to a long, netted-skin cultivar.

Novelty potatoes include the yellow or purple fleshed, fingerlings, small reds, etc.

When asked if he recommends specific varieties for Minnesota, Thill said any can be grown. While earlier maturing cultivars (90 days), would be better bets for northern Minnesota, he was quick to point out that over half of North Dakota is in USDA Zone 3 yet it ranks second in seed potato production acreage in the US. (In Minnesota, the northern half is USDA zone 3.)

Lots of different-looking potatoes! Photo credit: Potato Working Group.

In fact, potatoes are grown in all 50 states. Florida, Texas and California provide fresh potatoes in early spring, with an April harvest that's used up by June. New Mexico, Virginia, Missouri and Georgia produce the potatoes for summer potato salad. The harvest moves north with Minnesota grown potatoes coming into the market in August through October. Most of the crop will sit in storage until May or June, which explains why long storage is a desirable trait that potato breeders consider.

This northward migration is because potatoes can't be double cropped (two consecutive crops) in the southern US. It's too hot then there are insect and disease considerations. In fact, home gardeners should rotate potatoes with legumes, corn, root crops or leafy crops on at least a 3-year cycle to keep insects and soil-borne diseases down. Tomatoes, eggplant and peppers are related to potatoes and are subject to some of the same diseases.

Potato 101

A potato is really a stem that's modified for storage; the eyes are really buds. So technically, potatoes are vegetatively propagated, from stem cuttings. To propagate them, cut a potato into several chunks, each with at least one healthy eye, and plant each chunk about 4" deep. (The soil temperature should be at least 50 degrees F.) Planting potatoes in a trench, 6-8" deep then filling with soil may work better for some gardeners.

The potato that is lopped into the chunks is called a seed potato. By dividing it, you're releasing the dormant buds from a hormonal inhibition and letting them all sprout. (Sprouted potatoes generally have one dominant bud if the tuber is left intact).

Start hilling when the plants reach 5-6" tall. At that time they can be hilled to the point of being buried. Hilling encourages the development of stolons (underground runners) upon which potato tubers form. Hilling once is enough; it's not necessary to hill until the plant blooms. Thill said blooms are the signal of tuber initiation.

Once the foliage emerges, maintain an even water supply as the tubers swell with accumulated carbohydrates, nutrients and water. Finally, the plants turn yellow and start to die. The skin on the tubers sets, ceasing to be the tissue thin peel of "new" potatoes.

Potato seed pods. Photo credits: Potato Working Group

When buying seed potatoes, always buy certified seed potatoes for your garden. Certified means the potatoes meet state guidelines for quality and disease tolerance. You're more likely to have disease problems if you plant the last of the bag of sprouting, store-bought potatoes or potatoes saved from last year's garden.

Speaking of seed, in mid-summer, sharp-eyed gardeners may notice green marble size fruits amid the foliage of their potatoes. Each of these fruits yield approximately 300 true seeds. Seeds like these are used by potato breeders to find potential new cultivars as each one is geneticially distinct, like children in a family.

Just for fun, clean and save some of the seeds and plant them inside in mid-March. (You need not worry about disease transmission as you would with "seed potatoes", as very few diseases are seed transmitted.) After frost danger has passed, transplant the potato seedlings into the garden and wait. See what you get! Notice how variable the potatoes are from plant to plant. If you garden with children, you may plant a seed that will turn this year's bug catcher into a future potato breeder.

Plum Pox, a New Threat to U. S. Stone Fruits
Chad Behrendt, Extension Plant Pathologist
Dwight Robinson, Minnesota Department of Agriculture
Kevin Connors, USDA-APHIS

Healthy plums. Photo credit: Beth Jarvis

Plum pox, a newly introduced disease in the United States, is capable of infecting a number of different stone fruits including almonds, apricots, sweet and sour cherries, nectarines, peaches, and plums. This disease is currently established in many European and Asian countries including the Middle East, Mediterranean, Russia, and India. This disease has also been reported in Chile. Although the United States has been officially free of the disease, that status changed last year when a peach grower identified the virus in an orchard in Pennsylvania. It is now known to be infecting about 18 orchards in two counties in that state.

Plum pox is considered a devastating and economically important disease worldwide. Infected fruit becomes unmarketable, while infected trees produce less fruit. In severe cases, plum pox may cause 80 to 100% yield losses. Plum pox (PPV) is caused by a potyvirus and is thought to be the only potyvirus infecting Prunus species. There are currently four different strains of the virus, which are referred to as PPV-M, PPV-D, PPV-EA, and PPV-C. Not all strains infect the same species of Prunus. In addition, plum pox is able to infect a variety of annual herbaceous plants and a few woody, perennial plants when artificially inoculated.

To date, only PPV-D has been found in the United States. PPV-D, considered to be one of the milder strains, infects apricot, peach, and plum. Like other strains, aphids spread PPV-D. However, PPV-D does not appear to be vectored as easily as PPV-M. In addition, PPV-D is not known to be seed transmitted, unlike PPV-M. While aphids can transmit the virus in a non-persistent manner over short distances, long distance transport depends on humans moving infected bud wood or rootstock.

Plum pox can infect the leaves, flowers, fruit, and seed. Symptom expression and the severity of disease depend on the viral strain, Prunus species, season, and environment. Symptoms may be present, absent, or dormant. However, infected leaves and fruit typically produce yellow and/or brownish rings. These yellow and brown colors may also form bands, streaks, or blotchy patterns, commonly described as mottled or mosaic in appearance. Infected plums often develop irregular, curled, and/or puckered fruit, while chlorotic rings may develop on the stones (pit). Symptoms expressed on infected peach flowers are often described as color breaking. In other words, the color of the flower is not uniform, but blotchy or streaky.

Healthy Prunus triloba 'Multiplex' --a non-fruiting plum. Photo credit: Beth Jarvis

Although plum pox has been isolated from peaches in Pennsylvania, it is uncertain where the virus originated. Therefore, a nationwide survey is being conducted to determine if other introductions of plum pox exist in the United States. Since peaches are not truly hardy in Minnesota, only plums and apricots are considered to be at risk in Minnesota. The USDA-APHIS and the Minnesota Department of Agriculture (MDA) are jointly conducting a statewide survey of nursery and orchard plum trees.

Plum trees grown in Minnesota are also susceptible to a number of native diseases. One of these diseases, plum pockets, may produce symptoms similar to plum pox. To differentiate between these two diseases, carefully examine the fruit. Plum pockets will not produce symptoms on the leaves. If the fruit is spongy, hollow, and swollen (up to 10 times larger than normal) the disease is caused by plum pockets. These fruit are often referred to as bladder like. If the fruit is irregular and puckered, but firm and not hollow, the disease may be caused by plum pox.

Plum pox is a serious threat to both native and cultivated plums and apricots in Minnesota. Therefore, suspicious trees should be reported immediately, while infected trees are subject to quarantine regulations. To report suspicious trees, or for more information contact the Gary Thomson, USDA, Senior PPQ Officer, (612) 725-0080 or FAX: (612) 727-2442 or MDA at (651-296-8578).

Necrotic Ring Spot is Back!
Chad Behrendt, Extension Plant Pathologist

Necrotic rings in turf.

Note green grass in center of ring. Photo credit: U of M Extension Service

Last year the Yard and Garden Clinic received many lawn calls and samples describing brown circular rings. Well, the clinic is again receiving many calls describing rings in the home lawn. These rings vary in size, but are generally about one foot in diameter, and best described as a donut.

The center of the ring or the hole in the donut is filled with green grass, along with the area surrounding the donut. Only the ring or donut itself is brown in color. In addition, the ring is often sunken or lower than the surrounding grass. Unfortunately, there are two common diseases that may cause these types of symptoms, Yellow Patch and Necrotic Ring Spot. Therefore, an accurate diagnosis typically requires the submission of a sample. Before submitting a lawn sample call the Yard and Garden Clinic. There is a $5.00 charge for samples.

Necrotic ring spot is most frequently observed on newly sodded lawns, which are 2 to 5 years old. Generally, the sod is laid on top of a couple of inches of black dirt, which is laid over clay. This layering effect creates drainage problems and poor root growth. In addition, most newly sodded lawns are heavily watered and fertilized. The vigorous growth produces a thick layer of grass material called thatch, which stimulates fungal growth and the development of plant disease symptoms when greater than ˝ " thick.

To manage necrotic ring spot begin with good cultural practices. Properly water, fertilize, and mow your lawn. Dethatch and aerate your lawn to help reduce the thatch layer. If disease is severe, fungicides can be applied in the spring. Cleary's 3336 with the active ingredient thiophanate-methyl is currently registered for turf. For more information on Necrotic Ring Spot see the extension publication, Turf Patch Diseases.

New Disease Resistance Information for Honeycrisp and Zestar!
Chad Behrendt, Extension Plant Pathologist

Apple scab. Photo credit: Chad Behrendt

Apple scab and fire blight, two severe diseases of apple, can cause premature defoliation and branch dieback. To minimize the severity of these diseases homeowners should consider planting resistant varieties. Initially, the resistance of Honeycrisp and Zestar!, two of the more popular varieties, was unknown. However, recent investigations by Dave Bedford at the University of Minnesota, Horticultural Research Center, have shown Honeycrisp trees to be resistant to apple scab and fire blight, and Zestar! trees to be intermediate in their resistance to apple scab and fire blight. For more information see the Yard and Garden Briefs, Apple Scabs and Fire Blight (http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/p223fireblight.html).


Spring Leaf Diseases
Chad Behrendt, Extension Plant Pathologist

Oak anthracnose. Photo credit: Chad Behrendt

Just as April showers bring May flowers, April showers also bring plant diseases. Probably the most common diseases are fungal leaf spots such as ash and oak anthracnose, iris leaf spot, and apple scab. Each disease is caused by a different fungal organism, but all of them require moisture for germination and infection. Therefore, the incidence and severity of these diseases varies from year to year, depending on rainfall. Frequent spring rains are likely to yield high levels of disease, while infrequent rains are likely to yield minimal infections.

All of these diseases survive winter in infected plant material on the ground or on the plant. Reproductive structures within infected debris become active and release spores, with the onset of spring rains. These spores are rain-splashed and windblown to healthy leaves, where they cause new infections. Therefore, the incidence and severity of disease is also dependent on the amount of infected material surviving winter.

Apple scab. Photo credit: Chad Behrendt

Although each fungus produces spots on the leaves, they all produce unique, diagnostic characteristics. Anthracnose produces irregular brown spots and brown leaf margins. Infected, brown margins often curl as leaves continue to grow and enlarge. Iris leaf spot produces small brown spots with dark green margins, which later turn gray with red-brown margins. Apple scab produces velvety, olive-green to black, circular spots. All of these diseases may produce multiple leaf spots on the same leaf, which eventually coalesce to form large irregular blotches.

One can predict the severity of each disease by monitoring previous disease levels, the number of initial infections, and spring rainfall. To manage fungal leaf diseases begin with good cultural practices. Remove and destroy all infected plant material before spores are released in the spring (fall is the best time for clean up). Maintain plant vigor by properly watering, fertilizing, and mulching. Water plants at ground level early in the morning to reduce leaf moisture and provide adequate airflow, when possible, to reduce moisture levels.

If disease has been severe for several years or plants are grown for edible fruit, fungicides may be applied. Fungicides should always be applied according to the directions on the label. However, fungicide applications are not typically recommended for landscape plants. Fungal leaf spots may be aesthetically displeasing, but do not generally cause serious harm to the plant.

Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/Plpa.htm
Beware of Blacklegged Ticks
Jeffrey Hahn, Assistant Extension Entomologist

Blacklegged tick, female and male. Photo credit: Jeff Hahn

People are commonly encountering blacklegged ticks now as they spend more time outside. The black legged tick, formerly known as the deer tick, is a potential vector of Lyme disease and human granulocytic erhlichiosis. This tick is commonly found in hardwood forests and grassy fields but is uncommonly seen in maintained lawns. The greatest numbers of blacklegged ticks are in the central and east areas of Minnesota.

An adult female blacklegged tick is orangish brown with a black spot near the head. It is a little smaller than an American dog tick (a.k.a. wood tick). However be careful about using color and size to identify ticks. Ticks can be engorged or unfed, female or male, or immature or adult. These differences can alter their ‘normal' appearance making identification difficult.

To discourage ticks when you are outside in areas where they may be found, wear protective clothing, such as long-sleeved shirts and pants. Tuck pants into socks for extra protection. Walk in the middle of the trail and avoid grassy nearby areas. Apply a repellent to your clothing to discourage ticks. Products containing DEET can be applied to clothing or skin. Repellents containing permethrin should only be applied to clothing.

Periodically inspect yourself and others for ticks on all parts of the body. On children, particularly check on the head. If a tick is found biting, carefully remove it with tweezers by grasping it around the head as close to the skin as possible and gently yet firmly pulling it out. Home remedies such as covering the tick with vaseline or touching it with a lit match do not work. Save any ticks that are biting to be identified by an expert.

A blacklegged tick that is crawling on you is not biting and can not transmit Lyme disease. When a blacklegged tick is biting (i.e. its mouthparts are imbedded in your skin), it needs to be feeding for at least 36 hours to transmit Lyme disease, while nymphs need about 24 hours. Initial research gives a similar time for blacklegged ticks transmitting human granulocytic erhlichiosis. The first visible sign of Lyme disease is a rash that eventually clears in the center. However, not all people will experience this and many other symptoms can occur. Other symptoms can include chills, fever, headache, malaise. Human granulocytic erhlichiosis can exhibit similar symptoms. If you have been bitten by a blacklegged tick and have suspicious symptoms, see a physician right away.

Andrenid Bees Are Active Now
Jeffrey Hahn, Assistant Extension Entomologist

A solitary bee. Photo credit: Yard & Garden Line

A type of solitary bee, known as an andrenid bee, is common now in gardens and yards. One commonly seen species is about 1/2 inch long with a yellow thorax and a shiny black abdomen. Andrenid bees are solitary and live in individual burrows. Unlike social honey bees, andrenid bee species do not have a caste system (i.e. queen, workers, drones). Some andrenid bees overwinter as pupae and emerge as soon as the weather becomes warm. Adults are relatively short-lived, surviving for no more than a month. They spend most of their time building a nest to lay eggs. They provision the nest with pollen balls so her larvae will have food when they hatch. When this work is completed, the bee closes the nest entrance with soil. The adult andrenid bee flies off and dies. The larva spend its entire life in the nest, eventually emerging as an adult the following spring.

Andrenid bees often nest in dry, sunny sites that contain sparse vegetation. While they are solitary, andrenid bees are also gregarious with many bees nesting close together. People become concerned when they see dozens of bees flying around in a small area. Fortunately, these bees are very docile and nonaggressive and stings are very rare.

Tolerate andrenid bees as much as possible. They are active for no more than a month and then go away on their own. Remember that the risk of stings is extremely low. Because they like dry sites, you may be able to discourage them by keeping an area well-water. If they are nesting in an area where they can not be tolerated, try drenching burrows with soapy water to kill them. This should be considered as a last resort.

White Grub Damage
Jeffrey Hahn, Assistant Extension Entomologist

Grubs. Photo: credit: John Kyhl

If you noticed white grub damage in your turf last fall, that does not automatically mean that your lawn still has a white grub problem. Before you attempt to treat your lawn, check for an active infestation. This is important because in a lot of cases, white grubs are probably gone. White grubs have a three life cycle. Many of them are at the end of this life cycle. If you saw one inch-sized grubs last year, that means that they are in the process of pupating this spring and turning into June beetles in another month. June beetles may lay eggs into your lawn again, but feeding is minor and will probably not be noticeable this year. Watch your lawn more closely in 2001. If you have white grubs this is when damage will probably first start to be visible.

If you discover white grubs in your turf this spring, treat them right away to minimize their damage. You can treat affected areas with one of the following insecicides: diazinon, halofenzamide (MACH-2), imidacloprid (Merit or Grub-ex), or isofenphos (Oftanol). Be sure treated areas are watered thoroughly after application to help move the insecticide into the root zone where the white grubs are located.

Eastern Tent Caterpillar Is Active Now
Jeffrey Hahn, Assistant Extension Entomologist

Eastern tent caterpillar. Photo credit: Jeff Hahn

Small eastern tent caterpillar nests have been reported in the Twin Cities the last week of April. These silken webs are made in forks of tree limbs. These caterpillars prefer to eat the leaves of fruit trees, such as apple, cherry, flowering crabapple, plum, and chokecherry. You may also find them defoliating other hardwood trees, including ash, birch, maple, oak, and willow.

Eastern tent caterpillars feed during the day and retire to their tent at night. They also stay ‘indoors' during rainy or cold weather. As caterpillars grow larger, they also enlarge their nest. Caterpillars feed for about four weeks. Eastern tent caterpillar feeding does not seriously damage healthy, mature trees, even if they completely defoliate a tree. Vigorously growing trees will leaf back out several weeks after caterpillars have finished feeding. When full grown, an eastern tent caterpillar is about two inches long, hairy and blue with a conspicuous white line running the length of its back.

An easy method to manage eastern tent caterpillars is to remove webs with a broom or a stick and crush, burn, or bury the webs along with the caterpillars. Wait until the caterpillars are inside their tent, like on a cool or rainy day, before removing the web. If you want to use an insecticide to protect trees, spray the foliage with a registered product, such as Bacillus thuringiensis, acephate, permethrin, or carbaryl. Be sure most caterpillars are no longer than one inch. If they're larger, don't treat them; they're done feeding and spraying them doesn't help the health of the tree. If trees are flowering, spray Bacillus thuringiensis, a type of bacterial insecticide, to protect pollinating bees. This insecticide is nontoxic to humans and other animals.

Watch Out For Cutworms in Your Garden
Jeffrey Hahn, Assistant Extension Entomologist

Cutworm. Photo credit U of M Dept. of Entomology

Expect cutworms to be out in gardens now. They feed on many young garden plants, including tomatoes, peppers, beans and other vegetables and flowers. They chew the stems about one or two inches above ground, often knocking plants over. Damage is most likely to occur when seedlings and transplants are more tender.

You are not likely to see cutworms feeding as they are active at night and hide during the day. Fortunately, cutworms usually do not move too far from where you find damaged plants. They move about an inch under the soil where they wait until night. If you cutworm injury, search your garden thoroughly during the day for any hiding cutworms. Crush or drown (in soapy water) any that you find.

You can also control cutworms nonchemically by using protective collars. Place juice cans, cardboard rolls from tissue paper or paper towels, or similar items around tomatoes, peppers, and other transplants, when putting them into the garden. These collars should be two inches above and below the soil to prevent the cutworms from reaching the plants. Because cutworms prefer to stay near ground level, they generally do not climb above the collars or dig below it. If you don't notice cutworms until later, try wrapping plant stems with aluminum foil to discourage cutworms.

If these nonchemical methods are not completely successful, there are several insecticide options you can use to supplement your efforts: Apply an insecticide, such as diazinon, to the plants' stem to kill cutworms as they attempt to feed. A bait, such as carbaryl (e.g. Sevin), sprinkled at the base of the plant also is effective. Granules, such as diazinon, can also be applied as a preplant treatment.

Cutworm damage should not persist much past mid-June

Clover Mites Still Very Common
Jeffrey Hahn, Assistant Extension Entomologist

Clover mites continue to be very common in homes. They have been particularly abundant this spring. See the Yard & Garden Line News for April 15, 2000 for information about these very tiny, reddish nuisances.

Larder Beetles
Jeffrey Hahn, Assistant Extension Entomologist

Larder beetle, adult and larvae. Photo credit: Jeff Hahn

It can be common to find a few larder beetles in your home during spring. Adult larder beetles are between 1/4 and 1/3 inch long, oval and black with a cream-colored band across their back. These beetles hibernate outdoors during winter as adults. They start looking for food in spring as soon as the weather starts to warm up. They enter homes through cracks and small spaces. Finding a few larder beetles now does not mean there is a problem. Just remove the occasional larder beetle by hand.

However, if you see moderate to large numbers of larder beetles, especially if you also find larvae, that indicates an infestation. The immature larvae are worm-like, dark brown, hairy, with a pair of hooked spines on their tail end. Larder beetles are scavengers, and are known to feed on high protein foods, including animal hides and furs, feathers, dead insects, cured meats, dry pet food, and cheese. Probably their most common food source in homes is dead cluster flies that have accumulated in wall voids.

Check dry pet food, furs, hides and get dispose of any infested material. If the source of the infestation is dead insects or a dead animal, there isn't any practical method for removing the food source and control larder beetles. If you have an ongoing problem with animals or insects getting into your home and eventually serving as food for larder beetles, take steps to prevent them from entering your home. For example, to exclude cluster flies, caulk and seal cracks and spaces before August and treat the home's exterior with an appropriate insecticide during late summer.

Insecticides are not normally needed to control larder beetles. As long as a food source is present, larder beetles will continue to be a pest and insecticides do not solve the problem. Once the food source is eliminated, the larder beetles will go away on their own.

Now Here's Something You Don't See Everyday
Jeffrey Hahn, Assistant Extension Entomologist

Bot fly: Immatures and adult. Illus. credit: USDA.

In the ‘aren't you glad that doesn't live in Minnesota' category comes a sample from a medical center in Racine, Wisconsin. A patient had recently returned from South America and discovered a larva that was infesting him under his skin. This was identified over-the-phone (and verified later with a sample) as a human bot fly larva, Dermatobia hominis. This insect does not occur in the United States but is found in parts of Mexico and Central and South America, roughly between latitudes 25° N and 32°: S. Human bot flies infest humans, as well as cattle, swine, cats, dogs, horses, sheep, and other mammals and a few birds.

Human bot flies have a fascinating biology, one that makes you wonder how they have succeeded over time. The adult fly captures blood-feeding flies, such as mosquitoes, and lays eggs on their bodies. When a carrier fly bites a host, newly hatched bot fly larva(e) penetrate the host skin. The larva creates a subdermal cavity where it feeds for five to ten weeks. A person can be infested by more than one human bot fly, but there would only be a single larva in a specific subdermal cavity. Eventually the larva drops to the ground to pupate. Fortunately, human bot fly myiasis rarely causes death, although such infestations are uncomfortable to say the least.

Editorial Notes

Bloodroot. Photo credits: Beth Jarvis

This bloodroot photo was taken at Nerstrand Woods State Park, just south of Northfield. It's a lovely place to visit, especially in spring.

In the last issue, I included a shot of naturalized squill. I've recently discovered quill have started to naturalize in my front lawn! What lovely "weeds"!

An observation: Dutch hyacinths are generally regarded as short lived bulbs, virtually annuals. Years ago, probably 1988 or so, I planted an assortment of Dutch hyacinths--pink, orange, red, yellow, blue, purple and white. Last weekend, I realized that there are 4-6 of both the blue and the purple left, and there are a lot of flowers on the flower stalks. I wonder if there's something more persistent about the blue/purple shades. Anyone else notice this??

Coming up in future issues: How to make sense of a soil test, what to do about hazard trees and landscaping around ponds.

I'm always looking for article ideas, so, don't be shy!! Your story suggestions are most welcome!



Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist
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Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator

Websites
Sustainable Urban Landscape Information Series. This site contains everything from landscape design planning and lawncare to both herbaceous and woody plant selection databases. The URL is:http://www.sustland.umn.edu


For pesticide info, for both home owner and professionals, check out:

http://www.crc.agri.umn.edu/~mnhelps/

There's also some very interesting reading at Forest Products website. To get there from here, click on: http://www.cnr.umn.edu/FR/extension/

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