Yard & Garden Line News Volume 3 Number 3                                                               March1, 2001

Features this issue: Should I Grow Grapes? A Decision-Making Checklist Winter Injury on Trees Growing Wax Plant, Hoya carnosa Tomato Time.....Well, Almost! Early-season Garden Pests Editorial Notes

Should I Grow Grapes? A Decision-Making Checklist
Doug Foulk, Extension Educator, Ramsey County

'Swenson's Red' Photo credit: U of MN Extension Svc.

It’s a fact steeped in history: tell a Minnesota gardener that he or she can’t grow a particular plant and the gauntlet has been thrown. Back in the mid-1800’s, it was widely believed that our climate was simply too harsh to grow apples. Enter Peter Gideon, who labored for years to produce the ‘Wealthy’ apple, a hardy cultivar still available today. ‘Wealthy’ has since been joined by numerous high-quality University of Minnesota-bred cultivars like ‘Haralson,’ ‘Sweet Sixteen,’ and ‘Honeycrisp’ ^TM. Minnesotans love a challenge.

Perhaps the love of challenge explains why so many Minnesotans want to grow grapes. Growing grapes in Minnesota is not for the faint of heart. To be successful you must not only provide a warm, sunny site and a structure for the vines to inhabit, but must also invest the time and effort necessary to learn an arsenal of terms and cultural practices. For gardeners who want luscious summer fruit with less effort, blueberries, raspberries and strawberries are all well adapted to Minnesota home gardens and should provide plenty of homegrown berries. For those who prefer the challenge, however, the lure of grapes may prove irresistible. Here are the questions you need to ask before you decide to try growing them.

IS THERE A CULTIVAR I’LL ENJOY EATING OR DRINKING?
In Minnesota we grow two types of grapes, ‘French Hybrid’ and ‘American.’ The French Hybrid types are actually crosses between hardier American-type grapes and Vitis vinifera, the ‘Old World’ grape species commonly used to produce wine. While most French Hybrid grape varieties require winter protection in Minnesota, there are exceptions, at least for the southern third of the state. These include ‘St. Croix’ and ‘Frontenac.’ ‘St. Croix’ produces a passable red wine, according to University of Minnesota grape breeder Peter Hemstad, but it’s ‘Frontenac’ that has the most potential for Minnesota’s fledgling wine industry. 'Frontenac', the newest introduction from the U of M, was bred specifically for red wine production and is the hardiest red-wine variety in Minnesota. The grapes have a high sugar and acid content at harvest, making a red wine that echoes the flavors of cherries and plums. Although flavor ratings are highly subjective, don’t expect a ‘Frontenac’ wine to taste like that bottle of ‘Cabernet Sauvignon’ you had with dinner. We just aren’t there yet.

'Frontenac' Photo credit: U of MN Extension Svc.

Most home gardeners prefer grapes for table use, however, and as luck would have it, we have several worthy candidates from which to choose. All are considered American-type grapes and all have Vitis labrusca in their parentage (think ‘Concord’). American grapes are generally much better suited for fresh eating and juice than their French Hybrid relatives. Our hardiest American grape cultivars for growing in Minnesota include ‘Beta,’ ‘Bluebell,’ ‘Worden,’ and ‘Valiant.’ ‘Bluebell’ is an early-maturing, disease-resistant, blue table grape with delightful flavor. It makes an excellent juice. ‘Worden’ is a Concord-like cultivar with greater hardiness and a more subdued flavor than its famous parent. All grapes hardy for our climate are seeded, so ask yourself if you’ll tolerate having to spit the seeds. The university publication ‘Growing Grapes for Home Use’ contains an extensive listing of grape cultivars suitable for growing in Minnesota and may be found online at: www.extension.umn.edu/distribution/horticulture/DG1103.html.

DO I HAVE A SUITABLE SITE FOR GRAPES?
Grapes require full sun and serious warmth to grow and ripen properly, period. Neither that north-facing slope nor that spot near the oak tree that receives half-day sun will suffice for grape growing. Grapes want the sunniest, warmest spot you can give them. Therefore, plant grapes in full sun on a south, southeast, or southwest-facing slope or on the south side of a building or windbreak. If you’ve got a sandy soil, you’ll do even better—a sandy soil warms up more quickly in spring than other soil types. Grapes won’t tolerate poorly drained soils, so if that’s what you’ve got, you’ll want to improve the drainage, create a raised bed, or select a different site.

Wire-trained grapes. Photo credit: Beth Jarvis

One other factor to consider in selecting a site for growing grapes is proximity to herbicide use, especially the broadleaf herbicide 2,4-D. Grapes are extremely sensitive to various herbicides. Even the vapors rising from a nearby application on a warm, still day can cause harm. Therefore, think about not only your own herbicide usage, but also that of your neighbor or the farmer across the road. Roadsides, small grain fields and lawns alike may receive frequent treatment. If anyone nearby uses 2,4-D or other broadleaf herbicides, you may want to consider growing a fruit crop other than grapes.

AM I WILLING TO LEARN THE TERMINOLOGY?
The most intimidating part of growing grapes for many home gardeners may well be the terminology of training and pruning. While terms like ‘trunk,’ ‘shoot’ and ‘cane’ sound like they could be different terms for the same thing, they actually differentiate separate parts of the plant. Training system terminology can sound strange and exotic as well. In Minnesota, the training system used for grapes depends upon whether the vines require winter protection or may be left on the trellis over winter. While our hardiest grapes may be grown using an upright system called the “4-Arm Kniffen,” more tender varieties require a “Mini-J” system that is easier to remove from the trellis in fall. Both training systems are described in ‘Growing Grapes for Home Use.’

"Mini-J" system. Photo credit: Beth Jarvis

AM I WILLING TO LEARN PROPER PRUNING TECHNIQUES?
In the same publication, check out the instructions for pruning grapevines. Once you have established the proper structure for long-term fruit production, annual pruning requires a reasoned approach. And you will prune. A lot. Not only will you remove most of the previous year’s rampant growth, you must also selectively prune toward two goals at once, thinking of both the fruit you want in the coming year as well as the canes you want to produce for next year’s crop. Such pruning requires attention to detail, an understanding of how grapevines grow, and patience.

AM I WILLING TO BUILD A TRELLIS?
Technically you don’t have to build a trellis—many a grapevine has thrived on a standard fence. However, if a sturdy fence doesn’t happen to be located where your grapes need to go, you’ll have to provide a suitable structure to support their rampant growth. The ideal structure for a cultivar not requiring winter protection consists of a pair of strong wires, located at 36 and 60 inches above ground level, supported by a series of sturdy posts. Remember, grapevines are long-lived woody vines. Skimp on a decent trellis now; swear at your shortsightedness tomorrow.

These are the questions you need to ask yourself before growing grapes. The good news is that once you’ve addressed the issues above, there’s nothing else about grape culture that should prove especially daunting. There are a few disease problems to be alert to—and thankfully, good sanitation measures are often sufficient for the home garden situation—and you might still have to figure out how to protect your ripening crop from raccoons or other uninvited guests. But if you enjoy a gardening challenge and have the site, tools, and knowledge to give growing grapes a shot, then that bowl of ‘Bluebells’ will seem all the sweeter at harvest time.

Winter Injury on Trees
Janna Beckerman, Extension Plant Pathologist

Winter injury above snow line. Photo credit: Dept of Plant Pathology

After being blessed with three mild Minnesota winters, the winter of 2000 felt particularly ferocious. As tough as this winter was on us, our poor trees and shrubs cannot escape winter's wrath. Winters like this can cause frost cracks, root or stem damage, winter browning, die back, or even plant death. Below are some of the symptoms of winter injury that you can anticipate seeing in your neighborhood.

Symptoms of winter damage are already appearing on our conifers. Red-brown foliage has started to appear on Colorado blue spruce and red pine around the area. This injury is usually due to freezing following a spell of warmer weather. Take care that the symptoms of winter damage are not confused with the symptoms of some of the needle cast diseases. Remember to make certain that none of the signs of needle cast diseases (black fruiting bodies on the needles or twigs) are present!

Another symptom to help you distinguish winter injury from disease is to examine where the injury occurs. Often, winter injury begins where the snowline ends. This results in the upper half of the tree having reddish-brown needles, while the lower half (which was protected by the snow) remains green. The snow cover prevents winter injury of young conifers by providing shelter from drying winds and from the glare of the sun. Finally, the reddish-browning of evergreens such as arborvitae and yew may not show up until May or June. That said, we are currently seeing these symptoms on yew at the St. Paul campus

Winter injury on yew. Photo credit: Beth Jarvis

Regardless of what type of evergreen you are dealing with, wait to prune affected branches until bud break occurs. Although numerous needles may be lost, the buds are usually protected and will leaf out come springtime. By patiently waiting until bud break occurs, you can more accurately determine where the damage ends. Prune out the infected portions of the plant, removing only dead branches.

Compared to conifers, winter injury on hardwoods is more difficult to diagnose. With hardwoods, the symptoms of winter injury due to root and stem damage include early leafing out, or no leafing at all. This is followed by shoot death when warm weather develops. You can avoid this problem if you use only zone hardy trees and shrubs. It is also important to remember to plant them in the proper site. Finally, to prevent winter injury in the future, generously mulch them with wood chips to help protect roots and prevent cold injuries. Fortunately, these types of injury would not be expected this year due to the tremendous snow cover we had this winter.

Cracked bark due to sunscald Photo credit: Chad Behrendt

Another type of winter injury that primarily affects (but is not limited to) hardwoods is sunscald. Sunscald and bark cracks occur mostly on the south and southwest sides of smooth-barked trees and shrubs. Maples and other thin barked trees seem to be particularly vulnerable, followed by apple and other fruit trees, linden, and mountain-ash. The cambial temperature of south to southwest facing trees can reach into the 60° range while the shaded portion remains at freezing (32°F). This heating results in the tree losing its dormancy, which is followed by lethal freezing when the sun sets. Sunscald, coupled with drought, can result in vertical frost cracks and death of the cambium.

Frost cracks also provide an infection court for decay and canker pathogens. Prevention is the best method of contending with sunscald. If possible, provide shade by strategically placing other plants or structures on the south sides of thin barked trees and shrubs. Tree wrapping with reflective or light color material may be effective in preventing sunscald and bark cracking. Current recommendations for trees that are newly planted is that they should be wrapped for at least two winters. Thin-barked species should be wrapped for several years or until mature bark is established. Regardless of how long you wrap your trees for, care must be taken to remove such wrapping in the spring. Moisture that collects between the bark and wrapping may provide an infection court for disease when the weather warms up.

The primary factor limiting the northern range of plant species is winter injury. Compared to the more boreal (arctic) species, such as aspen, black spruce and jack pine, many favored trees such as red and white pines, maples, and linden are much more vulnerable to injury, as is the non-native Colorado blue spruce and mountain-ash. Because Minnesota has such long winters, there is a greater likelihood of winter injury. However, with the proper protection and a little patience, your trees will recover their healthy green after the last red needles fall.

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

Hoya carnosa. Photo credit: U of MN Extension Svc.

Wax plant, Hoya carnosa, is an old-fashioned houseplant much prized for its hanging clusters of waxy, star-shaped flowers. Each bud opens to reveal velvety pinkish white petals with a miniature red star in the center, so perfect as to appear artificial. But despite its exotic beauty, wax plant is not for everyone.

Don't choose Hoya carnosa if you want instant gratification. It requires great patience, usually taking many years with nothing but leafy, vegetative growth before producing its first flowers. But once it finally begins flowering, your wax plant should bloom reliably every year. In fact, it might bloom twice annually, if you provide excellent growing conditions.

Hoya flowers fascinate, not only because of their unique appearance, but also their heavy, sweet "tropical" fragrance, so noticeable at night. In its native habitat, Hoya blossoms are pollinated by night-flying insects. Though the chances of those insects living in your home are slim to none, your wax plant will continue to behave just as it's been "programmed" through the ages, despite the change in living circumstances.

Growing a wax plant is easy. Its vining stems may be allowed to trail from a hanging container, or trained upwards on strings or a wire hoop, pushed into the soil. Give it an abundance of sunlight -- a west or south-facing window works best -- if you want it to bloom well eventually.

Hindu rope plant, H. carnosa 'Hummel's compacta' Photo credit: Deb Brown

Never trim back the long vines, though, even though they're not particularly attractive. Short flowering stems, called spurs, grow from the youngest, leafless portions of each vine. A new set of flower buds forms each year on the same spurs. By removing them you eliminate the potential for future flowering in those locations.

Don't pick faded flowers off, either. Instead, let spent blooms fall of their own accord to avoid risking injury to the spurs. (You might want to set something beneath the plant to collect those fallen blooms; they're usually sticky with sweet nectar.)

Always water wax plant thoroughly, using room temperature or tepid (not icy) water. Spill out any extra water that collects in the saucer below it, then allow the soil to become quite dry before you water again. Because its leaves are leathery, thick and succulent, Hoya carnosa can go a long time without water, particularly during cooler winter months indoors.

Its root system is rather modest in size, so you can keep your wax plant in the same container several years before moving it to roomier accommodations. A larger volume of soil will stay moist longer when you water it, so never transplant Hoya from a small container to one much larger. Instead, move it up in incremental steps. Fertilize the wax plant sparingly when you see spurts of new growth developing.

And there you have it; Hoya carnosa, a fascinating houseplant with fragrant flowers that will bloom for a lifetime....if you're patient enough to stick with it the first six or eight years with little reward.

Tomato Time.....Well, Almost!
Deborah Brown, Extension Horticulturist

Variety of home- started tomatoes Photo credit: Beth Jarvis

We're still buried under what feels like a ton of snow, but that hasn't kept many gardeners from thoughts of growing luscious, red ripe tomatoes! While it's still a little early to plant seeds, it's none to soon to buy them. It's also a good time to plan your strategy to have tomato seedlings reach just the right size and stage of development for transplanting once soils warm in late May or early June.

Some people raise their own tomato seedlings to save money. Usually, though, it's to take advantage of the multitude of different varieties offered through mail order catalogs and on seed racks in local garden centers....to say nothing of that sense of accomplishment you feel when you've raised your plants "from scratch."

Often people make the mistake of starting tomato seeds too early indoors. To time tomato seeding, count back only six to eight weeks from when you expect to transplant them into your garden. Seeds should sprout within five to eight days of planting, provided you can keep the growing medium relatively warm -- between 70 and 75 degrees. The cooler the soil, the longer you'll wait.

Short sturdy plants will "take off" faster in the garden than larger plants that have had their growth checked by sitting too long in small, constricting containers. In a summer with average temperatures, they'll be more productive over the long haul than tomato plants that were older and larger when you transplant them.

You don't need a lot of expensive, sophisticated equipment to start seeds indoors. However, if you want good results, it's best to invest in a shoplight that holds at least two fluorescent tubes. (Which size depends on how many packs of seeds you plan to start.) Seeds started on a window sill often grow tall and spindly, even in a sunny location.

Suspend your lights from a chain so you can raise them as the young seedlings grow. Maintain a distance of only three or four inches between the tops of the tomato leaves and your fluorescent tubes. If there's much more space between them, plants will stretch just as they would growing in a window.

Your second purchase should be an inexpensive timer that will turn the lights on and off for you, automatically. Set it to keep plants lit 16 to 18 hours daily. (When not in use for seed starting, it can do double duty, turning table lamps on and off for security when you're out of town.)

Another important key to raising tomatoes successfully from seed is paying close attention to sanitation. Always start with fresh "sterilized" potting soil, clean containers and tools. Garden centers sell a wide variety of plastic cell-packs, trays, peat pots and other systems for starting seeds indoors. They also have clear domes that fit over the trays to help maintain moisture during the germination process. To re-use plastic containers, first wash them in soapy water then soak them for 30 minutes in a disinfectant solution made of nine parts tepid water and one part liquid chlorine bleach such as Hilex or Chlorox. Rinse them thoroughly when they're done, and you're all set.

"Juliet', a newer cultivar Photo credit: All American Selection

In addition to re-using store-bought containers, you can save money and do your part for recycling by starting some seeds in small plastic tubs that originally held yogurt, margarine or other foods. Just be sure to punch a number of holes in the bottom of each to allow for good drainage. Soggy soil can result in root rot and encourages development of fungal "damping off" disease. It's also an attractive site for fungus gnat larvae.

When tomato seedlings develop their second set of true leaves, it's time to transplant them into individual containers. You'll also need to begin fertilizing them with a very mild starter fertilizer every couple weeks.

Don't be in too much of a rush to move young tomato plants outdoors. They'll grow best when both air and soil temperatures have warmed significantly. Before you plant tomatoes in the garden, harden them off by moving them outdoors during the day, but pulling them back to the shelter of a porch or garage at night. After about a week, they should be ready for planting in their permanent locations. Choose a cloudy day, or plant late in the afternoon when the sun isn't too strong. You may want to jam a sheet of cardboard into the soil behind each plant to give it a bit of protection from the sun, and in some cases, strong prevailing winds.

Early-season Garden Pests
Bruce Giebink, Entomology technician

Asparagus beetle. Photo credit: U of MN Extension Svc.

If you have a garden, you're also going to have insects. This article provides an overview of some common early-season garden pests in Minnesota. You'll be better prepared to anticipate potential pest problems this year and take action at the proper time. You'll need to properly identify the insect causing the problem and understanding enough about its biology and behavior to make an informed decision about what management steps you should take.

Remember, use insecticides only when necessary and ALWAYS READ THE LABEL ON THE PACKAGE BEFORE APPLYING THE PRODUCT. Follow the label directions.

We hope this article will help you get your garden off to a good start this spring!

Chewing insects: Flea Beetles, Asparagus Beetle

Flea beetle damage. Photo credit: Dept. of Entomology

Flea Beetle species
Flea beetles have an enlarged, muscular hind leg that allows them to jump (like a flea); they jump readily when disturbed. Pest species of flea beetles are small, often less than 1/5 inch.

Biology - Adults hibernate in the soil and immediately start feeding on the new growth of their preferred hosts, which are small and tender and very sensitive to feeding injury. Female beetles lay tiny white eggs on the soil near the base of the plant. Eggs hatch in about a week and the slender white larvae feed on the plant roots or tubers for 2-3 weeks. Feeding larvae cause little, if any, damage.

Damage - Beetles chew small pits or holes (often called "shotholes") in the leaves, making them more like a sieve than a leaf when feeding damage is severe. Because they feed on the undersides of leaves, you may see considerable damage but only a few beetles. High populations can be very devastating to newly emerged seedlings, sometimes killing them. Damage is usually limited to a few types of closely related plants, such as plants related to potatoes (Solanaceae) or cabbage (Cruciferae). The most severe damage occurs to seedlings during May and June.

Management- Since the greatest risk is to young plants, plant seedlings in well-prepared beds (to help promote rapid growth) or use larger transplants. Another non-chemical option is to exclude the beetles with floating row covers or other screening materials. If high populations are present, repeated treatments of a pesticide such as carbaryl (Sevin) or permethrin (e.g., Eight) can also provide some control.

Asparagus Beetle, Criocerus asparagi (L.)
These small brightly colored (blue-black and red with creamy-yellow spots) beetles are usually found anywhere asparagus is grown.

Shepherd's crooks.

Biology - Adult beetles are first active in early may, about when asparagus first starts to come up. At this time, they lay large number of eggs on asparagus shoots. Larvae mature in 2-3 weeks, drop to the ground, and pupate in the soil. After 10 days or so new adults emerge to repeat the cycle.

Damage - Larvae feeding along the sides of young shoot causes it to make a U-turn, a condition known as "shepherd's crook." The dark gray, fleshy larvae cause additional damage by devouring leaves and stems later in the season.

Management- Treat shoots in early to mid-May with an insecticide such as malathion or carbaryl (Sevin) if you find more than 1 in 10 (10%) of the asparagus shoots being attacked.

Boring insects: Common Stalk Borer, Papaipema nebris (Guenee)

Stalk borer. Photo credit: Jeff Hahn

Biology - Female moths lay their eggs on weeds, especially weedy grasses during late summer. These eggs spend the winter on these plants and hatch very early in the spring. Young larvae first feed within the stems of grasses until they outgrow their thin-stemmed hosts. They then seek out more think-stemmed hosts (such as giant ragweed or corn), which they enter on the side and proceed to bore upward into the stem. The larvae are very active and often move from one plant to another. They pupate in late summer just under the soil surface. Adults emerge in August and September, mate and lay eggs on nearby weeds.

Damage - Stalk borers are generally uncommon and occur sporadically, although they may be common in a localized site. The entire plant or a portion of the plant (corn, rhubarb, pepper, tomato, potato) wilts and then dies. Closer inspection may reveal a small entry hole, which is often full of frass.

Management- Plan ahead! If you've had problems in the past with stalk borers, the most reliable way to get rid of them in the future (or at least greatly reduce the problem) is by cleaning up nearby weeds. Female moths lay their eggs on these weeds and newly hatched larvae feed on them. By cleaning up these weeds, you'll force the next generation of moths the lay their eggs elsewhere, rather than next to or even in your garden. You can physically kill borers you find infesting plants but, unfortunately, there's not much you can do to save your plants once the larvae have already bored into them.

Soil Insects: Cutworms (esp. Black cutworm), Cabbage and Onion Maggots

Caught in the act! Photo credit: U of MN Extension Svc.

Cutworms (Black, bronzed and dingy)
Black Cutworm, Agrotis ipsilon (Hufnagel)
Bronzed Cutworm, Nephelodes minians (Guenee)
Dingy Cutworm, Feltia subgothica (Haworth)
Cutworms are a major headache for many gardeners. Most are active just at or below the soil surface but some species do climb and will feed on any part of the plans. Although several species occur in Minnesota, those most likely to harass Minnesota gardeners are the black, bronzed and dingy cutworms. The adults of all cutworms are moths with dark gray front wings and lighter colored hind wings. Like most moths, they are active at night, feeding on flower nectar and flying around lights.

Cutworms are common in grassy areas and may become severe in gardens that were lawns the previous year. Certain species are particularly damaging to tomato, bean, cabbage, and other young seedlings, clipping them off as soon as they are set out. This nocturnal feeding behavior, combined with their ability to hide in the soil, makes these cutworms among the hardest pests to control.

Biology - Most cutworms (such as the glassy, dingy, and bronzed) spend the winter as partially grown larvae in the soil or under leaves, plant stubble, etc. The black cutworm overwinters as either a larva or pupa. These larvae start feeding in the spring but only at night. Fully-grown larvae dig down into the soil several inches where they pupate. The adult moths that emerge mate and lay thousands of eggs, usually in grassy or weedy areas, which is why larval damage is so often associated with weeds, particularly grassy weeds.

Although the black cutworm (BCW) does overwinter here in Minnesota, adult moths migrating into the state during early spring on warm southerly breezes cause the majority of the damage. Damage outbreaks are closely associated with warm, stormy weather patterns. As with many insect pests, BCW damage can be sporadic, with severe damage one year and little or none the next. The Bronzed cutworm spends the winter here in the soil as a partially grown larva.

Damage - Plants are damaged at night. Leaves or developing fruit may be chewed. Entire plants may disappear or be found chewed near the soil line. Because cutworm caterpillars hide during the day (under cover near damaged plants or in burrows), gardeners seldom see them. If you do manage to find one, it'll be under the soil curled up into a tight c-shaped ball.

Management- If cutworms frequently damage your garden, protect your young plants by placing a metal or cardboard collar around each plant. Be sure to press it into the soil an inch or two to keep it in place and prevent larvae from burrowing under it. Another way to manage them is with carbaryl (Sevin) bait, which you should spread around near damaged plants during late afternoon or early evening. Finally, you could treat the soil with diazinon (Spectracide) granules before seeding or setting out transplants. Be sure to incorporate it into the top 4 inches of soil.

Cabbage and Onion Maggots

Cabbage maggot Dept. of Entomology

Cabbage Maggot, Hylemya brassicae (Bouche) or Delia radicum (L.)
Onion maggot - Hylemya antigua (Meigan) or Delia antigua (Meigen)
Cabbage Maggot (CM) can be a serious pest of cabbage, broccoli, cauliflower, turnips, and radishes, especially during cool, moist weather. Some people consider CB the most destructive early-season pest of cabbage and cauliflower.

The onion maggot (OM) is generally considered to be our most serious pest of onions. If we have a cool, wet spring, there's a good chance onion maggot (OM) will be a major problem. Some years they end up ruining the entire onion crop. When onions are small and growing close together, a single maggot may move from one plant to another and destroy several plants.

Biology - Both CM and OM spend the winter as a puparia, 1 to 5 inches down in the soil. About the same time transplants go into the garden, the adults (small gray or brown flies, slightly smaller than a housefly) emerge from their puparium and lays eggs at the base of plants and on the soil nearby. Small white maggots emerge from these eggs in 3-7 days and begin to feed on roots and stems just below the soil surface. Larvae feed for 3-4 weeks, pupate and then repeat the process several more times throughout the summer.

Damage -Maggots of both species feed within roots and underground stems, riddling them with brown tunnels. Lower leaves of young plants become tinged with yellow, fail to grow and, if damage is severe enough, wither and die. Injured plants are also more susceptible to, and often succumb to, diseases such as blackleg and bacterial soft rot.

Management- There are several ways to protect cabbage or onion seedlings from feeding larvae. One is to prevent the flies from laying their eggs by covering the soil surface with cheesecloth or a floating row cover. The other is to kill the larvae by treating the soil with a pesticide such as diazionon (Spectracide) before planting. Be sure to incorporate the pesticide into the top 4 inches of soil. You can also protect plants by spraying them directly with a residual insecticide such as permethrin or malathion. Finally, be sure to destroy any "throw-a-way" onions (culls) after harvest. This precaution will greatly reduce the potential for OM problems next spring.

Piercing-sucking: Aphids (especially on peas and tomato)

Turnip aphids. Photo credit: Dept. of Entomology

Aphids, also known as "plant lice," are small, soft-bodied, pear-shaped, sucking insects in the order Homoptera. They have a pair of tubes (cornicles) that look like tail pipes on their back near their rear end. Aphids come in all colors, can be winged or wingless and secrete honeydew (a concentrated plant sap).

Biology - For a tiny insect, aphids can have an incredibly complicated life cycle. Hosts, sex ratios, reproduction (sexual vs. asexual) and the presence or absence of wings can change form generation to generation. Males appear in the life cycle only once during the year, with the onset of cold weather in the fall.

Damage - Aphids can damage plants directly (by sucking plant juices from the plant) or indirectly (by introducing disease organisms such as viruses into the plant). This can result in a loss of plant vigor (stunting), deformation (puckering, curling) of the leaves, buds or flowers or death or reduced plant quality due to disease transmitted by aphids.

Management- If necessary, treat plants with an insecticidal soap, which is a "soft" insecticide that will kill soft-bodied insects but not harm to beneficial insects (predators and parasites) which play a critical role in controlling aphids. If this treatment doesn't produce satisfactory results, you could use an insecticide such as Malathion. Again, remember to apply any insecticides sparingly to minimize any adverse affects on natural enemies.

Slugs

Slugs on hosta. Photo credit: Dept. of Entomology

Slugs can be very damaging pests in moist, shady gardens. They thrive during rainy seasons and in well-irrigated gardens, especially in gardens with lots of mulch.

Biology - In Minnesota, slugs usually overwinter as eggs in protected sites, such as under plant debris, mulch consisting of coarse wood chips or boards. Eggs hatch during spring or early summer. Slugs are most active during evenings but may also be active during cool, damp days, particularly in cool, shaded sites.

Damage - Slugs damage the leaves of many plants and are particularly fond of seedlings. Feeding holes are irregularly shaped. Extensive feeding can result in plant stress and even death.

Management- Rake your garden in early spring to remove leaves, plant debris and slug eggs. Also, remove any other hiding places, such as boards. If you mulch, be sure to avoid using large wood chips and be sure not to put more than 3 inches of any mulch. Such a mulch will provide the benefits of a mulch (reduce weeds and conserve water) without creating a favorable environment for slugs.

Water your garden only when necessary. Water in the morning so plants are dry by evening. Reduce hiding places and allow for better air circulation by pruning lower leaves and staking larger plants. Thinning out crowded plants also helps.

Attract and trap them by setting out several flat boards, shingles, or damp newspapers. Check these traps in the morning and kill any hiding slugs. You can also attract and drown them by setting out shallow saucers of beer or other fermented beverages. Sink these saucers into the ground so that the lip is level with the soil level. Slugs are attracted to the odors, fall in and drown.

If you have a small garden, you may want to consider using copper strips or tape as a barrier to slugs. Garden supply stores sell these products specifically for slug control.

In addition to the above non-chemical tactics, you can also manage slugs with chemicals, such as iron phosphate or metaldehyde baits. Apply iron phosphate bait granules (e.g., Escar-Go, Sluggo) to the soil. After consuming the bait, slugs stop feeding and die in 3-6 dies. Metaldehyde baits (e.g., Deadline, Defender) are available as granules or liquid paste. Put the baits under a piece of board near slug-infested plants to protect birds and pets. Metaldehyde is more effective during warm, dry weather. Apply it after a rain and when the sunny weather is predicted for the next few days.

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

Wishbone flower. Photo credit: Beth Jarvis

Next month, we return to publishing two issues per month. For April 1, Dean Herzfeld, state pesticide applicator training coordinator, and I will report on things you should know about hiring a someone to apply lawn care chemicals.

We'll follow that up with the first of two articles on herbicides from Roger Becker, Extension weed scientist. Roger will tell us all about pre-emergence herbicides first, when there's still time to treat for crabgrass. Later, when the weeds are popping out all over, he'll follow up with information on post-emergence products.

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? Also this spring, we'll be hearing from Vince Fritz, Extension horticulturist, on research he and others are partcipating in on using cabbage to find a treatment for cancer.

In June, we'll have a report on the treated lumber study conducted by U soil scientists. Part of the research, regarding uptake by plants, is still underway.

The curious blue flower at the top is the wishbone flower. The Latin name is Torenia fournieri and it is named after a Swedish botanist and clergyman, Olaf Toren, though the plant is native to Vietnam. The common name comes from the two stamen that curve just like a wishbone. Increasingly common as bedding plants, wishbone flowers are available in pink/rose, purple, blue and white, all with yellow throats. These flowers do well in full sun to part shade. Seeds should be started inside now as they need to grow 10 weeks before they're ready to go outside. They need light to germinate and take 2-3 weeks to do so. (A trick I learned from commercial growers is to sprinkle vermiculite over the uncovered seeds. It helps hold moisture yet reflects light into the seed starting medium.) Given the high costs of heating this winter, we can only guess what garden centers will have to charge to cover their costs for bedding plants. Given the ample snowfall this winter, starting seeds indoors could be not only horticulture therapy for the winter-weary soul but a way to save a bit on plants. 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 have gardening questions, please call the Yard & Garden Line at (612) 624-4771.

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
or to unsubscribe, enter: unsub yglnewslist

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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