Yard & Garden Line News Volume 3 Number 5                                                               April 15, 2001

Features this issue: Flood Damage Effects On Trees Try Growing Spuds Getting Your Yard and Garden Ready for Spring Pre-emergence Herbicides in the Lawn and Garden Brace for Forest Tent Caterpillars Sowbugs Common in Homes This Spring Blacklegged Ticks Are Active Now Editorial Notes

Flood Damage Effects On Trees
Janna Beckerman, Extension Plant Pathologist

Flooding park. Photo credit: Dave MacDonald

Unlike previous years, the absence of midwinter thaws has left us with record snow cover across much of the state. Concerns about flooding are already being expressed due to the deep snow falls that have accumulated during the winter of 2000. Even with a gradual thaw, the sheer volume of water is expected to cause flooding in some areas. If spring arrives quickly and with great warmth, the risk of flash flooding is compounded. Finally, if we didn’t have enough water in the form of snow, spring rains could compound the potential for flooding.

Although the impact of flooding on humans is almost immediate, how flooding affects trees is less obvious. There are several factors to take into account when considering the impact of flood stress on a particular tree. These include: 1) Species tolerance to flooding, 2) overall tree health, 3) length of flood and 4) sediment accumulation around tree roots.

Some species of trees are better able to adapt to flooded conditions. Trees that have evolved in a floodplain ecosystem have mechanisms to cope with the periodic flooding that may occur and are better able to handle flooding. However, urban areas that end up flooded are not usually forested by trees that are adapted to flooding. There are some notable urban exceptions: boxelder, silver maple, hackberry, green ash and downy hawthorn are all considered relatively tolerant to flooding stress. It should be noted that the pines and oaks (with the exception of eastern pin oak and swamp white oak) are all relatively intolerant of flooded conditions.

When examining flood damaged trees, keep in mind that urban life is stressful to many species of trees, making them particularly susceptible to flood-related damage. Flooding compounds these stresses, leaving trees highly predisposed to additional mortality due to insect and disease attacks. If death does not occur outright, then it may be due to secondary agents of plant disease. Those trees that weren’t killed in the initial flood event are considered predisposed, and can die quickly due to the combination of physical injury and rapid invasion from insects or diseases. Conversely, well-maintained and healthy trees can and do recover quickly. Most trees fall within these two extremes. How well a tree copes with flooding and the secondary agents of plant disease depends upon how vigorous the tree was prior to flooding, and how long the flooding occurs.

Symptoms of flood stress
It is important to remember that plants respond differently to flooding and that this response depends on tree species, health and site. For this reason, trees that are flood stressed exhibit a range of symptoms that include: leaf chlorosis and subsequent defoliation, reduced leaf size, development of epicormic shoots (watersprouts or small shoots emerging from the main stem), and crown dieback. These stresses may produce early fall coloration and leaf drop. It also is not uncommon for declining trees to produce either large seed crops or no seed crops in years following a flood. Symptoms may develop over a period of several years or they may abate as the tree recovers. Finally, it is important to remember that the symptoms may progress and ultimately result in tree death. However, this tree death may occur several years after the flood. It is very difficult to link a flood from several years ago as the cause of tree death years later.

Secondary Agents of Plant Disease
You need to be on alert for the possibility that flood-stressed trees may become invaded by insects or infected with disease. The likelihood of this occurring depends upon the severity of the flood and tree health. A tree that is already predisposed because of stressful urban conditions can have this stress compounded by flood. This tree should be considered a prime target for opportunistic insects and disease causing agents. These opportunists invade or infect only those hosts that are predisposed by stress. In this case, the insect or pathogens are actually secondary agents of tree disease. Flooding could act as the predisposing agent or an inciting agent of plant disease if the flood period is prolong or intense. Although not well understood, it is generally believed that predisposed plants emit a biochemical signal which attract secondary agents of plant diseases.

Flood stressed trees are especially susceptible to collar and root rot diseases caused by species of Phytophthora and Pythium, which are considered "water molds" and are not "true" fungi. Free-standing water aids in both the reproduction and dissemination of these fungi. Oxygen starvation, wounding and loss of cell permeability due to flooding provide ideal infection sites for these organisms to colonize.

Symptoms of Phytophthora collar rot of flood damaged trees include brown to reddish water-soaked lesions with abrupt margins underneath the bark. A reddish brown liquid sometimes exudes from the canker margin. Cankers may not be noticed until foliar symptoms develop, which include sparse, chlorotic(yellow) leaves, premature fall color and dieback. Pythium root rot produces less distinctive diagnostic symptoms that included root rot and dieback.

Even trees that have appeared to recover are still at risk for infection by a group of opportunistic pathogens, members of the genus Armillaria. These fungi are the causal agents of shoestring root rot. There are hundreds of species of Armillaria, some of which are virulent pathogens and others of which only act as contributing factors to tree death. Although drought is usually considered the inciting agent that allows Armillaria to establish itself and infect, flooding has been implicated as a factor of Armillaria root rot in oak, chestnut and larch.

Symptoms of Armillaria infection include leaf chlorosis, defoliation, reduction in leaf and shoot growth, dieback, and/or death. Key diagnostic signs of this disease are white mycelial fans under the bark; black, shoestring-like rhizomorphs attached to roots, and the fall development of honey-colored mushrooms growing in clumps at the tree base.

Flooding is but one of the many injurious factors trees face over the course of their lives. Proactive maintenance of tree health is the best way to contend with periodic flooding. As the tree recovers, it needs to replenish food reserves. To increase tree vigor, the US Forest Service recommends application with a low nitrogen fertilizer, aerating the soil, mulching, and watering if soil conditions become excessively dry after the flood. Dead or cankered branches should be removed. Prune trees only when bark surfaces are dry or during the dormant season to minimize infection by opportunistic pathogens. In the absence of tree maintenance, flooding and other environmental extremes leave trees susceptible to further injury or death. How well a tree copes with these stresses is dependent upon how healthy the tree was prior to the flood.

Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/PlantPathWeb/Plpa.htm
Try Growing Spuds
Deborah Brown, Extension Horticulturist

New potatoes! Photo credit: Cindy Tong

I love eating potatoes in any just about any form, but I've never grown them in my garden. I've always been satisfied with spuds from the grocery store. But friends tell me that freshly dug potatoes are significantly tastier than their supermarket counterparts, and I'm inclined to believe them. Perhaps I can tempt you into growing your own spuds this year.

Here's some information about potatoes culled from an article I wrote for the Star Tribune a while back.

* Awareness of different potato varieties is expanding. People used to think there were only three types of potatoes: round white ones, oblong "bakers", and red-skinned "boilers". Exposure to new varieties in local farmers' markets, gourmet restaurants, and even in the produce section of some supermarkets has expanded the notion of what a potato can be.

* Yellow-fleshed potatoes are becoming more popular. Europeans have always preferred yellow-fleshed potatoes to white. Now Americans are turning to yellow potatoes more frequently because they look rich and buttery without any added fat or calories. Some people swear they even taste buttery - which might go to show how much we "taste" our food with our eyes.

* Fingerling potatoes are becoming less novel and more accepted. These slender potatoes have a smooth, moist, delicious texture that makes them perfect for salads and other specialty dishes that call for potato slices.

* There's more demand for colorful potatoes, from gourmet chefs to folks who garden with their children. In addition to typical white or creamy-fleshed potatoes and yellow ones that look buttered, potatoes may be blue, purple, pink or reddish-fleshed.

Growing Potatoes

Potatoes form along stem below soil. Photo credit: Potato Breeding Project

Always buy certified seed potatoes to reduce any likelihood of disease. Since most spuds should be planted when soil temperatures range between 55 and 70 degrees -- about ten to fourteen days before the last frost -- the time to order them is now.

Potato plants need plenty of sunlight and grow best in loose, well-drained soil. If your soil is too alkaline they'll be more prone to potato scab, so it would pay to acidify the soil by mixing in peat moss and fertilizing with a product meant for acid-loving plants.

Start by digging a trench that's six to eight inches deep. Plant your seed potatoes about a foot apart, then rake about three quarters of an inch of soil over them. Wait until stems are roughly eight inches tall to "hill" them by hoeing more soil up around them. They should be covered half way to their tops. Repeat the hilling process twice more at two week intervals, adding just an inch or two of soil each time.

New tubers will form between the original seed potato and the soil surface. Make sure there's enough soil mounded around the stems to prevent developing tubers from exposure to sunlight which will turn them green, bitter, and mildly toxic.

If you garden in sandy soil, you'll probably need to water potato plants even if you've incorporated lots of peat and organic matter. On more moisture retentive soils, you might get by without watering your potatoes. They should be tastier and more nutrient-dense without irrigation. But they'll also be knobbier if the developing tubers are exposed to fluctuating moisture levels, such as experiencing a heavy rainfall after a long dry spell.

Harvesting the Fruits of Your Labor
If you're growing some unusual potatoes for the first time, you might not be able to resist the urge to try them before they're fully mature. You should be able to harvest some tiny new potatoes seven or eight weeks after planting the earliest varieties. If you're careful, you should be able to wiggle your fingers in the soil and take a few small tubers from each plant, leaving plenty to grow larger for harvesting later in autumn.

Growing Potatoes in Containers
You can increase your potato yield greatly in small spaces by planting potatoes in bottomless containers or cages, provided you're willing to water frequently. The containers need to be at least eighteen inches across at the base, and two feet or more tall.

Set the cage or container over soft, fertile soil. Put one large seed potato in each, then cover it with four inches of soil. As the plant grows, continue to add more soil, mulch, or compost, covering no more than one third the height of the potato vines at any given time. If all goes well, you should be able to harvest two to three times the number of spuds that you could in the same amount of garden space.

Getting Your Yard and Garden Ready for Spring
Deborah Brown, Extension Horticulturist

Uncover tender roses soon. Photo credit: Beth Jarvis

Here's a checklist of yard and garden activities to prepare for spring:

Around the Yard

*Keep off the lawn if it feels moist and spongy underfoot. You run the risk of damaging grass crowns and roots by walking on them.

* Lawn care begins with a brisk raking with a lightweight, fan-shaped rake to break up snowmold mats and remove potentially dangerous debris before it can be run over by a power mower. As for the snowmold, allowing oxygen to reach the grass crowns is usually all that needs to be done to eliminate long term damage. And as for the bones, stones, tiny metal cars, and other flotsam that shows up after the snow melts, they can be a safety hazard should a power mower pick them up and fling them out again at a high speed.

*Hold off any fertilizing until the grass is growing rapidly enough to require mowing. If you fertilized twice last fall, wait until early June, or skip spring fertilization altogether.

Prune non-flowering shrubs now. Photo credit: Beth Jarvis

*Crabgrass typically sprouts around Memorial Day in the Twin Cities. Pre-emergence herbicides that prevent seed germination need to be applied and watered into the soil about two weeks before weed seeds are expected to sprout. If it doesn't rain in time, water the product in, yourself.

(Most of these products are a mixture of fertilizer and herbicide. Even the all-natural corn gluten meal pre-emergence products are, by their nature, ten percent nitrogen. This means you rarely need to apply additional lawn fertilizer if you use a pre-emergence product this spring.)

* Unwrap rigid plastic and kraft paper wrappings from the trunks of young trees in early April. While there's controversy among tree specialists as to whether tree wrap is beneficial, everyone agrees that it must come off early spring, before weather warms for good. Tree wrap helps keep trunks moist in warmer weather, increasing the likelihood of rotting and damage.

* Prune shrubs that aren't grown for their attractive flowers, any time now. You'll want to wait to prune other spring-flowering shrubs until right after they've finished blooming.

*Don't prune oak trees during April, May, or June. Wait until later in the season, or better yet, next February or March to have them pruned.

In the Garden

Put garden debris in compost pile. Photo credit: Beth Jarvis

* Remove protective mulch from roses, perennial flowers, spring-flowering bulbs, and strawberries as it loosens and thaws. Tender roses are typically uncovered around mid-April; stems may be killed when temperatures drop below twenty degrees.

*Pull out any large weeds or stubble from last year's plants that still remain in the garden. Except for seedy weeds, plant debris may be composted. Small plants may be turned back into the garden soil with a little additional fertilizer.

*Turn the soil over, using a garden fork or tiller. If your garden is large enough, you can save some back-breaking labor by hiring someone to come out and rototill for you.

*Have your soil tested if it's been several years since you've had it checked. It's the only way to know for sure which type of fertilizer (and how much of it) to use. Call the Yard & Garden Line for instructions or contact the University's Soil Testing Lab directly at 612-625-3101. You can also visit their website at http://soiltest.coafes.umn.edu.

*Add organic material to your garden soil, especially if it is sandy or clay-like. Completed compost, packaged aged manure, and peatmoss all work well. You can add a thin layer of dry leaves, too, but be sure to add more nitrogen to help them break down without "robbing" nutrients from young plants.

*If you plan to grow watermelons or other plants that take a long time to mature, or you just want to get a jump on the season and put out tomato and pepper transplants as early as possible, spread dark plastic over some of the soil to heat it faster. Clear plastic actually is most efficient, but it acts like a little greenhouse; before long a crop of weeds will be growing vigorously beneath it.

* Start saving frozen orange juice cans to use as collars around tomatoes, peppers, and other transplants, to ward off cut worms. Buy your milk in one gallon plastic containers, then cut the bottoms off and use them as cloches or "hot caps" over the transplants when they first go into the garden. (Remove the lids.)

*If you haven't already done so, sit down and make a plan of your gardens. Take into account which plants will come back from last year, and which plants you want to try this year, either from seeds or transplants. It's too easy to go to a great garden center, then come back loaded with more plants than you possibly have room for. *It's not too late to order seeds from a mail order catalog for planting directly in the garden. Check local garden centers, too. Most have an excellent selection of flower, vegetable, and herb seed packets on display.

Pre-emergence Herbicides in the Lawn and Garden
Roger Becker, Extension Weed Scientist

Crabgrass along sidewalk. Photo credit: Beth Jarvis

Weed management in turf begins by maintaining a healthy, vigorous turf through proper management: mainly fertility, mowing practices, and water management. In garden or flower beds, good weed management begins with keeping the ground covered with mulches or a competitive plant canopy to reduce the establishment of annual weeds and ultimately preventing weed seed production. If weeds invade or persist in spite of proper management, herbicides are one option for control.

Pre-emergence herbicides are applied prior to emergence of the weed. Some products are used for general vegetation management and are non-selective, depending on the rate applied. Be sure to read the label! "Season-long" control provided by a non-selective product will prevent pretty much anything from coming up. Most herbicides used in lawns and gardens are selective, taking weeds out of desirable vegetation. Pre-emergence herbicides work on annual weeds and few have any effect on perennial weeds such as dandelions. Pre-emergence herbicides affect seedlings that have germinated and do not kill seeds that remain dormant in the soil. Therefore, it is critical to apply pre-emergence herbicides just prior to the emergence of annual weeds that have already germinated below the soil surface.

The trick is knowing when the weed seedlings will emerge. Summer annuals such as crabgrass need warm weather to germinate. In gardens, flower beds, or other areas where the soil may be disturbed, often some annual weed species are present that will germinate within a week or two after the soil is disturbed. If the garden is disturbed in late April or early May, you likely will get some early emerging cool season annuals such as knotweed and common lambsquarter. Soil disturbance later during mid- to late-May or early-June will typically result in the peak emergence of annual weeds such as crabgrass, fall panicum, and redroot pigweed - weeds that like warm soil temperatures.

In lawns, crabgrass moves in during the summer when it gets hot and turf growth is less vigorous or turf goes dormant. Historically, application of pre-emergence herbicides for crabgrass control in turf work best when applied between May 5th and May 20th around the Twin City area. See general aspects of weed control in, Weed Control in Lawns and Other Turf. Applying at this time insures the herbicide will be "activiated" or will move into the surface layer of soil by the time crabgrass begins to germinate.

Pre-emergence herbicides require moisture shortly after application through either irrigation or rainfall to move the herbicide into the top inch of the soil profile. This is what some call herbicide "activation". A word of caution, if irrigation is applied to bare soil, gently water the herbicide in. Do not erode or move soil. If soil moves, applied pre-emergence herbicide will move with it.

Chickweed, a common annual weed. Photo credit: Beth Jarvis

In turf settings, herbicide is easily incorporated through irrigation and is less likely to move off-site because vegetation prevents soil movement and encourages water infiltration. Excessive rainfall can literally leach some pre-emergence herbicides below the zone of weed seed germination, the top one-inch of the soil profile.

Herbicides such as Dacthal are water soluble and weakly adsorbed (bound to soil) which means they can leach. Excessive rainfall will reduce weed control with these types of herbicides as leaching dilutes the herbicide and moves it below the zone of weed seed germination.

The dinitroanaline herbicides, which includes herbicides such as trifluralin (found in original Preen® and Team®) or pendimethalin (many brand names and formulations) are not mobile and will remain in the upper seed germination zone. Many of the crabgrass products used currently are dinitroanaline products. They do require at least a half an inch of precipitation or irrigation to move them into the soil profile, but once there, they do persist throughout the season and provide long-term control of annual grasses and some small seeded broadleaf weeds.

Another phenomena of pre-emergence herbicide use is that the herbicide needs to be uniformly distributed on the surface. Uniform coverage means that no matter where a seedling starts to emerge through the soil profile, herbicide is available to control the weed. Non-uniform application can result in skip areas where weeds establish. Weeds that escape herbicide control can be controlled with shallow tillage, but should leave the herbicide in the one-inch surface soil layer to control subsequently germinating weeds. Deeper tillage will dilute the herbicide and bring new weed seeds to the soil surface that will germinate, possibly resulting in more weed problems than if tillage or hand hoeing were never done.

Pre-emergence herbicides can cause some injury symptoms when applied to turf, ornamentals, or vegetable or fruit crops, particularly if there is an extended, cool wet period following application. In cases such as these, the desirable vegetation does not metabolize or break down the herbicide as readily as it normally would and temporary symptoms of herbicide injury may appear. This herbicide injury usually will not persist and the desirable plants fully recover. On the bright side, conditions that cause this injury to desirable vegetation generally result in excellent weed control because the herbicides are more active in plants in general, including weeds. Conversely, extended hot, dry periods can result in poor activity of pre-emergence herbicides. Again, watering or irrigation of lawns or gardens can avoid this problem.

Lambsquarter. Photo credit: Beth Jarvis

The behavior of the pre-emergence herbicides will influence how you should use the products to their best advantage, but also to avoid environmental concerns. Generally speaking, most pre-emergence herbicides are not volatile. This means that after the product is applied, you will not see injury on plants adjacent to the treated site through the movement of vapors in the air. There is a possibility of movement with soil though if you have exposed soil on slopes and a heavy rain occurs shortly after application. This can move the soil with the newly applied pre-emergence herbicide off-site. Even if soil does not move, highly soluble herbicides can move with water runoff if heavy rain occurs before the herbicide has leached into the soil. If fairly large areas are to be treated, be aware of surrounding vegetation down slope from the treatment area. Avoid using extremely soluble herbicides that may affect the vegetation that is down slope in case a heavy thunderstorm does occur shortly after application.

Another phenomena of herbicides used for pre-emergence weed control is the length of time the herbicide persists in the soil. There are two sides to this story. The longer a pre-emergence herbicide persists, the longer it will control newly germinating and emerging weed seedlings. However, if the herbicide does not tie strongly to soil and is highly soluble, the longer lived materials can also leach or move off-site with surface water runoff. Ideally, products have enough persistence to last the season but also are adsorbed (bound) to soil so they stay put to do the job until they break down. A classic example of products that do both, have persistence and therefore long weed control and tend not to move off-site are the dinitroanaline herbicides commonly used for annual grass control in turf and in ornamental plantings.

Practices that are used to manage nitrate or phosphorous movement will also reduce leaching or surface run-off of pre-emergence herbicides. The University of Minnesota Bulletin BU-5726-GO, Turfgrass Management for Protecting Surface Water Qualityhttp://www.extension.umn.edu/distribution/horticulture/DG5726.html gives details on ways to prevent movement of applied chemicals. Pesticides that are soluble and relatively weakly adsorbed to soil or organic matter behaved much like nitrates from fertilizer. Herbicides that have lower solubility and are more strongly bound to organic matter or soil behave much like phosphorous in the environment. The difference is that herbicides dissipate and revert back to their individual elements, mainly carbon, hydrogen, oxygen, nitrogen, and in some cases chlorine, sulfur, or fluorine. The amount of any of these elements introduced through herbicide application is negligible, so levels are not high enough to be a plant nutrient source. Because herbicides break down and dissipate, the goal is to keep them in place where they were applied until they degrade to natural elements. As with the use of any herbicide, always read the label for use information including protection of the applicator, and any environmental or non-target issues of which the applicator should be aware.

Brace for Forest Tent Caterpillars
Jeff Hahn, Assistant Extension Entomologist

Forest tent caterpillar. Photo credit: Dept. of Entomology

One of the most anticipated pest problems this year is forest tent caterpillars. Also know as armyworms, these insects are expected to be extremely abundant in many areas of Minnesota, particularly the northeast and north central regions. Full-grown caterpillars are about two inches long, mostly blue and black, with a row of white, footprint or key-hole shaped markings along their backs, and many hairs along the edge of their bodies.

Forest tent caterpillars have a cyclical life cycle. They occur in very low numbers at first and are generally not seen. For about 8 - 13 years their populations gradually increase, eventually building to tremendously large numbers. They remain at outbreak populations for about 3 - 4 years. After that, their numbers crash and the cycle repeats itself.

The last time we experienced high forest tent caterpillar populations was in the late 80's an early 90's. We have gone through much of the 1990's without seeing these hungry caterpillars. But in the spring of 1997, they started to become conspicuous again. Their numbers have continued to increase and could be peaking this year.

Forest tent caterpillars overwinter on trees as eggs and hatch sometime during early to mid-May. Their favorite host is aspen, although they also love birch, basswood, oak, ash, and other deciduous hardwood trees. They rarely feed on red maples and pine, spruce, and other conifers. They feed for about 5 - 6 weeks then pupate. Adults emerge in mid-July and lay eggs which remain until the following spring. There is just one generation each year.

These caterpillars are considered to be a forest pest, but forest tent caterpillars can also be a pest in home yards. When populations are high, trees are often severely defoliated. Healthy, vigorously growing trees can tolerate even complete defoliation in two or three years consecutive years without serious injury. However, during an outbreak (four consecutive years or more of severe defoliation), moderate or severe defoliation can reduce growth, cause branch dieback, or possibly even kill trees. Young or unhealthy trees are less tolerant of severe defoliation in a single season.

Control of forest tent caterpillars in wood lots and other large areas of trees is generally not suggested. However, it may be desirable to protect a small number of landscape plants. if you had problems last year or anticipate caterpillars this year, be sure to check your trees for egg masses. The number of egg masses tells you the relative risk the tree faces from defoliation. When practical, remove as many egg masses as possible before they hatch to reduce caterpillars.

If it is necessary to protect your landscape trees, watch them closely for emerging caterpillars, starting in late April or early May. It's easier to manage caterpillars when they're small but it's also harder to see them. There are many residual insecticides for treating forest tent caterpillars. Less toxic products effective against caterpillars are Bacillus thuringiensis var. kurstaki, insecticidal soap, spinosad (e.g. Conserve), azadirachtin (e.g. Azatin, BioNeem). These insecticides are more effective against small, young larvae.

Sowbugs Common in Homes This Spring
Jeff Hahn, Assistant Extension Entomologist

Sowbugs. Photo credit: Jeff Hahn

Sowbugs are small, turtle or armadillo-like arthropods. They are about 3/4 inch long and brownish-gray. They are not insects but actually are a type of crustacean, similar to shrimp, crab, lobster, and crayfish. They require damp conditions and are typically found under leaves, mulch, logs, loose bark on stumps, brush piles and other accumulations of debris, and similar places. They feed on decaying plant material.

It is common for sowbugs to be found in homes during fall. Because they need damp conditions to survive, they often die within a few days of entering a home because the humidity is too low. Others find safe refuge in wall voids and cracks and crevices around the foundation, hibernating there through the winter. Sowbugs are more common in homes during cool, rainy autumns.

Now that the weather is warming, the surviving sowbugs are emerging from these overwintering sites. Some find their way outside but others go the wrong direction and become accidently trapped indoors. Fortunately, sowbugs are very innocuous creatures. They do not bite people, eat our food, or destroy our furniture or other property. However, sowbugs can by annoying particularly if they occur in large numbers.

There is no practical method for preventing sowbugs from moving into the living space of a home once they are all ready within the home. The best control is to physically remove them, e.g by sweeping or vacuuming. To prevent sowbugs problems in your home in the future, caulk or seal cracks and spaces that allows them to enter your home. Remove potential harborage areas close to your home to help minimize their opportunity to find their way into your home. In years of particularly high numbers of sowbugs, supplement this with a residual insecticide application around the home's exterior.

Blacklegged Ticks Are Active Now
Jeff Hahn, Assistant Extension Entomologist

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

The Yard and Garden Clinic received our first blacklegged tick (formerly known as deer tick) sample last week. Blacklegged ticks are potential vectors of Lyme disease and human granulocytic ehrlichiosis. They are first active when temperatures reach 39^oF. The chance of a tick bite is not as high now as it will be in spring and summer when temperatures are warmer. But don't be fooled by cooler early spring days, there is still some risk.

If you have been out are in a place where blacklegged tick are known to be present, be sure to check yourself thoroughly for ticks soon after being in that area. Wearing long-sleeved shirts and long pants and applying a tick repellent (products containing DEET or permethrin) also helps to reduce your exposure to ticks. Identification of ticks that you find on your person is important as not all ticks are vectors of Lyme disease or human granulocytic ehrlichiosis. Sometimes you can rely on color for a proper identification, but this is not always reliable. Take any suspected blacklegged ticks to an expert for diagnosis.

Not all blacklegged ticks are infected with Lyme disease and not all infected ticks that bite transmit Lyme disease. Adults need about 36 hours and nymphs about 24 hours to successfully vector the disease spirochetes. A similar time is needed for blacklegged ticks to transmit human granulocytic ehrlichiosis. If the tick you find is not engorged with blood, then it probably has not been biting long enough to transmit disease. Consult with a physician if you think you have been infected with a tick-borne disease.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm
Editorial Notes

Cat proofing. Photo credit: Beth Jarvis

We gardeners are thinking about planting. Most of us have only started tomatoes and a other long season crops indoors. I've heard tell of some who have direct seeded cool season crops outdoors, already. Unfortunately, when I think of planting seeds outdoors, I also think of my neighborhood cats. They delight in the 4' x 8' sandy loam litter boxes they think I prepare for them every spring. There is a city animal ordinance that is routinely disregarded by scofflaw cat owners and I haven't a clue where the cats live.

I like cats, but not in my garden. I don't want to dump repellents in my vegetable garden and I resent buying repellents to keep other peoples' cats out. In my small space garden, I trellis many things and the trellises aren't used until a bit later in the season. So, once I till and plant my garden beds, I lay the trellises over them. The trellises do a fine job of keeping Puff and friends from raising havoc with my freshly seeded spinach, etc. I lift the trellises off after the plants are up several inches. It seems that once there's a vegetative cover over the garden, the cats don't think of it as a litter box. Just thought I'd pass this along, for what it's worth.

If you want to read more on the subject of using dog and cat manures in home gardens, click on http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h238manure-dog-cat.html.

May 1, Vince Fritz, Commercial Vegetable Production specialist, will tell us about some research he's participating in using cabbage to find a treatment for cancer. Then, just in time for lilac and dandelion bloom, May 15, Roger Becker will be back with a follow up piece on post-emergence herbicides.

In June, we'll have a report on the treated lumber study conducted by U soil scientists. We'll also hear from Forestry folk on options and alternatives to treated lumber.

In the months ahead, we'll be learning about soluble salts. You've seen it on soil test reports, but what does it mean? Also planned is a piece on conservation biocontrol--what is it? Mary Meyer will write about new ornamental grasses. I'll also have a story on rain gardens in an upcoming issue.

I rely on your comments and questions for ideas for future articles. Please, keep the story ideas coming! We really try to be responsive to your needs.

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.extension.umn.edu/pesticides/

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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