Wood-boring pests find easy pickings in Idaho landscapes

Moscow, Idaho-They've got a job to do and they're going to do it well.

Long before man invented chainsaws, borers were recycling dead and dying trees, converting their wood into nutrients that other organisms could use.

They're doing it in our landscapes, too--thanks in no small part to us.  Healthy broadleaf trees can form callus tissue that thwarts borers' progress, and healthy evergreens can flush borers out on resin flows, says Ed Bechinski, University of Idaho Extension integrated pest management specialist.  But because many of our landscape trees aren't healthy enough to defend themselves, ash borers, bronze birch borers, locust borers, peach tree borers, poplar borers and dozens of others take their unwelcome toll.

According to Bechinski, our taste for trees from environments vastly different from ours plays right into borers' tastes for undefended wood.  Tree species that thrive in neutral or acidic soils struggle to pull life-sustaining nutrients from our often highly alkaline soils.  Our shallow irrigations-too little, too often-leave the deeper roots of many trees dry, and our lawnmowers and string trimmers chip and slice tree trunks, supplying handy places for the borers' flying parents to lay their eggs.

In Elmore County, Extension educator Mir Seyedbagheri says about a fifth of the calls he gets from homeowners are about borers.  They've spotted sawdust-like frass on the trunks of trees or at their bases; they've noticed rivulets of sap leaking from suspicious-looking holes or a random pattern of dying branches in their tree tops, or they've been battling borers for years and want to know what they can try next.

Seyedbagheri says a relatively new insecticidal soil drench containg the active ingredient imidacloprid combined with deep root feeding of chelated zinc, chelated iron and liquid nitrogen, phosphorus and potassium is saving many Elmore County trees from bronze birch borers.  the insecticide travels upward from the tree's roots in the narrow xylem layer located just beneath the bark.  Seyedbagheri recommends applying it by mid-May against the borers listed on its label and cautions that all label instructions must be carefully followed. 

Other systemic treatments include imidacloprid-or acephate-containing trunk implants, which also release insecticide into the xylem layer, but Bechinski notes that neither drenches nor capsules will control borers that have burrowed into heartwood and beyond the chemicals' reach.  "Systemic insecticides generally don't kill other common borers-like ash borers, locust borers and poplar borers- because the grubs don't spend enough time in the xylem layer to contact a lethal dose," he says.  For these borers, Bechinski recommends preventative bark sprays of other insecticides labeled for this use.

In Bonneville County, Extension educator Wayne Jones helps homeowners try to prevent borer infestations by spraying trunks and branches when the flying adults are mating and laying eggs.  Timed correctly for their flights, the sprays can kill adults as they land and larvae as they hatch. "But the best way to control borers is to keep the tree healthy."

Jones has seen borer-vulnerable quaking aspens that are still thriving in Idaho Falls' landscapes after 35 years because they've received the water, fertilizer and disease protection they've needed.  Typically, however, "if you have a 30-year-old quaking aspen, that's ancient for down here."

For homeowners who'd rather avoid pesticides, Bechinski suggests inserting a sharp wire into active borer holes-ones with fresh sawdust day after day-and acutally skewering the pest.  "You get the satisfaction of feeling like you're doing something," he says, "and it can be pretty effective, especially with peach tree borers, because their larvae don't chew very deeply into the tree."

Another option- one with reportedly mixed results-is injecting borer holes in trees with watery solutions of beneficial nematodes called Steinemema.  When they find their wood-damaging prey, these beneficials infect them with lethal bacteria, then have their carcasses for lunch.  Although steinemema nematodes aren't easy to buy locally, Bechinski says he would personally give them a try for a tree he really valued.  After squirting a suspension of nematodes into the hole, just cap it with wax and "hope for the best," he says.

Although borers are "one of the most frustrating insect pests to deal with, for homeowners and for me," Bechinski says they're not necessarily a death sentence.  "You can even have susceptible birch trees as shade trees in Idaho, but it's not a freebie.  You have to work at it.  You have to do everything you can to maintain a healthy root system and to remove small, dead branches at the first sign of infestation."

To learn more about preventing and treating borer infestations in Idaho, contact your county's University of Idaho Extension educator.

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Some Idaho Gardens are Aflush with an Unusually Early Spring, While Others are Still Napping

BOISE, Idaho-Daffodils in bloom.  Turf greening up.  The season's earliest weeds already germinating and leafing out.  "It's way too soon for all of this warm weather," says Jo Ann Robbins, University of Idaho Extension horticulture educator in Jerome County.

Unwary homeowners risk weeds galloping ahead of them in unusually warm springs like this one, but that's a gardening problem they can at east do something about.  Unseasonably early bloom in fruit trees, lilacs and other woody plants is not.  "if we didn't have another hard frost, it wouldn't be a concern.  We would just be ahead of the season," Robbins says.  "But I've never seen that happen."

Extension horticulture educator Tony McCammon says hard frosts-24 degrees Fahrenheit or lower-can occur even on April 19 in Payette County, where he is based.  All of the county's apricots, some of its pears and even a few of its peaches are already breaking bloom, and McCammon says apples won't be too far behind.  "If everything is in bloom and it doesn't get pollinated before we have another hard frost, we will lose a lot of fruit crops."

McCammon is also concerned about fire blight, a bacterial disease that over-winters in bark crevices of infected plants and spreads easily in wet, windy weather to susceptible plants, especially those with open blossoms.  Apples, crabapples, pears and quinces are particularly vulnerable, although the potentially destructive disease can also infect hawthorns, mountain ashes, serviceberries, cotoneasters, pyracanthas and other members of the rose family.  Chemical preventatives-but no after-the-fact treatments-are available.  Once the characteristic symptoms of water-soaked blossoms, light brown to blackened leaves and black "shepherd's crook" twigs appear, it's too late for gardeners to respond with anything but pruning shears and loppers.

What's really bugging Payette County homeowners, however, is a pest that's a lot more obvious at the moment: boxelder bugs.  "The adults have over-wintered and are resurrecting themselves like goldfish after a freeze," McCammon says. "They're really bad right now." But because boxelder bugs are simply a nuisance, he suggest managing them with soapy water or insecticidal soap rather than anything more toxic.  "The drown very easily."  Follow up by removing the leaf debris that's collected at the bases of structures, trees and shrubs and by wetting down the soil that was beneath it.  That's where the next generations of boxelder bugs are likely to be hatching. 

In Lewiston, Mike Bauer says crabgrass is two weeks ahead of schedule and the window for applying dormant sprays to woody plants is rapidly closing.  "For dormant sprays, temperatures must be between 40 and 70 degrees, and we've already had a few days above that," says the University of Idaho Nez Perce County Extension horticulture educator.  Homeowners can still use dormant sprays on cooler days, but only on plants whose buds are still showing a little green and haven't yet burst into the "popcorn" phase.

Bauer is also getting calls about tip damage in junipers-a cosmetic problem caused by wintertime freeze-thaw cycling.  On cold, sunny days, evergreens lose moisture from their leaves but can't replace it from frozen ground, he says.  "If you have sunny weather followed by a cold snap and wind thrown in, you can have tip damage."

Bauer says now's a good time for Nez Perce County residents to start mowing their lawns-but no lower than 2 inches.  When it comes to planting even cold-hardy perennials, however, he recommends caution.  "Whatever you plant now has to be frost-tolerant," he says.  "Don't get to anxious to start.  Spend your time preparing the soil, adding organic matter, doing soil tests and deadheading your existing perennials."

McCammon agrees.  "Everybody gets itchy to get in the yard but what they really should be doing now is a lot of designing."

In Franklin County, where Extension educator Stuart Parkinson is still finding ice under his asparagus ferns, there's plenty of time left for dormant sprays and dormant-season pruning. "We're ahead of schedule but it's still pretty cool here," he says. "I'm crossing my fingers that it will stay cool for awhile before spring growth initiates."

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Count 'em.  Idaho's Four Billbug Species are Lying in Wait    This Spring

ABERDEEN, Idaho-With at least four species of billbugs chewing on the roots and growing points of Idaho lawns, successful billbug control may be getting more complicated-and frustrating-for Idaho homeowners and golf course managers.

Tom Salaiz, University of Idaho turfgrass specialist, says the Phoenician billbug has now joined its cousins-the bluegrass, hunting and Denver billbugs-in Idaho turf.

Most control strategies and chemicals were designed to battle the bluegrass billbug, which over-winters as a harmless adult and whose grass-damaging larvae don't start emerging from spring-laid eggs until late May or early June.  Denver billbugs, on the other hand, spend the winter as both adults and rarin'-to-go- larvae and may also continue laying eggs later in the season.  The results aren't in yet for the Phoenician and hunting billbugs.

Historically, recommendations called for applying damage-preventing chemicals around May to kill billbug adults before they lay eggs in the bases of grass stems.  Salaiz says early to mid May is still the best time to put down these pesticides, although older, larger and deeper over-wintering larvae of the Denver species may escape control.  In addition, later generations of Denver billbugs may cause turf damage after the chemicals' effectiveness lapses.

 

Entomologists from Ohio State University and Purdue University are currently conducting billbug monitoring research on Treasure Valley golf courses.  In addition, Salaiz is trapping billbugs on golf courses and public grounds at Aberdeen, American Falls, Idaho Falls, Rexburg and other sites in southern Idaho.

"The implications of determining the extent of the billbug complex-particularly the Denver billbug-are that we will be able to make more accurate decisions on timing insecticide application," Salaiz says. "We need to conduct additional research on fine-tuning application timing as well as on the possibilities of late-summer and early-fall applications.

In the meantime, Salaiz says homeowners who are aiming for optimum billbug control should time their applications for the appearance of the black, weevil-like adults on their sidewalks in May.  Because the chemicals must soak down below the turf's thatch layer, Salaiz says it's also essential to follow the irrigation recommendations on pesticide labels.

Lawns damaged by billbugs look like they are under drought stress because the grass blades are basically severed from the roots and come up readily with a slight tug of the hand.  A healthy, vigorously growing lawn will recover from moderate billbug damage and symptoms may go unnoticed, Salaiz says.  But under-fertilized or otherwise stressed lawns will be more susceptible to billbug damage.

Researchers say that planting "endophytic" perennial ryegrasses, tall fescues and fine fescues remains an effective billbug-control strategy.  These grasses support a fungus that produces billbug-deterring or billbug-killing alkaloids in their crowns and leaf tissues.  For maximum effectiveness, 40 percent of the grass plants in a given stand must be endophytic, Salaiz says. 

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Green-loving Homeowners Can Save Water in Their Landscapes

PAYETTE, Idaho-Ask homeowners what they want to see in their landscapes and they'll tell you: green.  Tony McCammon, a University of Idaho Extension horticulture educator, says they can have it even in landscapes with only moderately thirsty plants. 

McCammon, a recent graduate of Utah State University, joined the Payette County Extension faculty last year.  An experienced designer of water-thrifty landscapes, he wrote his master's thesis on consumer landscape preferences.  He developed three alternative landscapes that were identical in design but different in turf, trees, shrubs and ornamentals.  Then he asked homeowners to rate them before and after he turned off the irrigation for five rainless weeks in mid-summer. 

The results: On a scale of 1 to 7, with 1 being "strongly dislike" and  7 being "strongly like", the northern Utah homeowners gave the traditional high water-use landscape a 5.4 in June but only a 4.4 in August.  They rated the low water-use landscape of native and drought-adapted plants a 4.6 in June and a 4.2 in August.  But the landscape whose water needs were intermediate between the two scored an encouraging 5.1 in June and an even higher 5.3 after five long weeks without water.

"In my overall opinion, the color of the grass told the whole story," McCammon says.  "If the grass was green, they liked the landscape more.  If the grass turned brown or got weedy, their opinion of the landscape changed."

According to McCammon, the Kentucky bluegrass in the traditional landscape turned off consumers when it turned an unappealing yellow during its temporary drought-induced dormancy.  The tall fescue in the intermediated landscape, on the other hand, stayed nearly unfalteringly green.  The native landscape's buffalograss-which would have benefited from an additional year of development-scored consistently low.

If homeowners could appreciate blue-greens and greys as much as they do deep greens, prospects for native-plant gardens in the Intermountain West would markedly improve, McCammon says.  Until then, he endorses intermediate landscapes and plants that use moderate amounts of water while still giving homeowners the green grass and season-long bursts of floral color they like. 

Even in traditional landscapes, homeowners can stretch water use by grouping plants according to their irrigation needs, creating optimum-rather than maximum-sized lawns, using mulches, improving soils, irrigating efficiently and adopting other principles of Xeriscaping, McCammon says.  He estimates that most Intermountain homeowners use 25 to 50 percent more water than their landscapes need and spend 60 percent of their home's drinking water on their yards.

"There's considerable potential to save water through conservation," McCammon notes.

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New Publication Suggests Fire-Resistant Plants

MOSCOW, Idaho-Because fires are a natural part of the Pacific Northwest landscape, homeowners who live in the wildland-urban interface must take precautions to protect their lives, homes and property.  That includes creating a "defensible space" where potential fuel has been modified, reduced or cleared in order to slow the spread of wildfire to their  homes. 

A new publication by Pacific Northwest Extension tells homeowners how they can select plants that may reduce their risk from wildfire.  Entitled "Fire-resistant Plants for Home Landscapes", The 46-page, full-color publication includes photos and descriptions of carefully selected ground covers, perennials, shrubs and trees for irrigated and non-irrigated landscapes.

Plants that are fire-resistant are not fireproof, but their foliage and stems don't contribute significantly to potenti8al fuel and therefore to a fire's intensity.  They can be damaged or even killed by fire, but they don't readily ignite from a flame or other ignition source.  Typically, they have moist and supple leaves, they accumulate little deadwood or dry material and their sap isn't resinous or gummy.

Combined with proper plant placement, plant spacing and ongoing plant maintenance, the use of fire-resistant plants can create a fuel break and help protect homes by blocking intense heat.

To order the publication, click here  http://www.info.ag.uidaho.edu or email calpubs@uidaho.edu or simply call (208) 885-7982.

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Fell Your Perennial Weeds in Fall

RIGBY, Idaho-It often surprises the homeowners he talks with, but Brian McLain says fall is the absolutely best time of year to control many perennial weeds.

McLain, UI Extension educator in Jefferson County, says weeds like quackgrass, Canada thistle, field bindweed and dandelions are most susceptible to herbicide treatments in the fall.  That's because the season's shorter days and cooler temperatures prompt these unwelcome plants to transfer energy reserves from their leaves to their roots.  "When you spray them in the fall, that same process carries the herbicides down with them, giving you a better kill," McLain says. 

Fall spraying won't make a dent in populations of annual weeds.  Their top-growth and roots die right along with the cold weather anyway, and their seeds have already been dispensed for sprouting next spring.  But for perennial weeds that would otherwise return next year, fall herbicide treatments can thwart those plans. 

"You'll reduce older, established perennial weeds a lot by next spring and you'll get even better control of younger ones," says McLain.  But finishing the job may take a year or two of treatments in fall and in spring.

To maximize the effectiveness of your fall herbicide applications, it's important to spray as much of the weeds' surface as possible.  Also, make sure that your weeds are healthy and actively growing before you zap them.  Weeds under stress from drought, frost, disease or mowing tend to "shut down," inhibiting their ability to take up and translocate herbicides.  Dust or dirt on leaves also reduce the bang you get for your herbicide buck.  "A healthy, actively growing weed is easier to kill than a sick or stressed one," McLain says. 

 

You can increase your weeds' vulnerability to fall-applied herbicides by irrigating them for a few days before spraying and by letting your Canada thistle rosettes grow to 6 inches across and your field bindweed and quack grass grow to 6-18 inches, respectively, before treating them.

Always identify your targeted weeds and know which herbicides to use.  Some herbicides are non-selective while others will kill only broadleaf plants-not grasses.  Spray on a warm, sunny day in early to mid-fall, before the first killing frost.  Avoid winds that can carry herbicide drift to desirable plants that you do want to see again next spring. 

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Ornamental grass care is almost as easy as watching grass grow

ABERDEEN, Idaho-Their intriguing motion, distinctive textures, pleasing colors and exceptional  winter-time beauty have made ornamental grasses fundamental elements in Idaho landscapes, says Steve Love, University of Idaho Extension horticulturist in Aberdeen.

Easily maintained, these perennial plants can be clustered in mixed borders, massed in bountiful groups, featured as solo accents or scattered throughout naturalized gardens.  "Different grasses are adapted to virtually every situation, soil type and climate in Idaho," Love says-from water conserving landscapes to backyard water features.  He offers these tips for ensuring their peak performance and picture perfection:  Surround your ornamental grasses with mulch to keep the soil cool, retain moisture and improve weed control.  Give them about one-and-a-half inches of water weekly, either all at once or-if your soils are sandy-divided into shorter, more frequent watering sessions.  Water less often if your varieties are drought-tolerant or if the weather has been cool and rainy.  It won't hurt and can sometimes help to apply a high-nitrogen fertilizer in spring, but grasses often need no fertilizer at all.  Cut back flower spikes and dead leaves to a height of 3-4 inches.  Do this in the late fall for grasses that shatter, break or collapse during the winter or do it in the early spring-just before new growth appears-for grasses that keep their looks through the cold weather.  Since grass-killing herbicides will damage ornamental grasses right along with grassy weeds, either dig out encroaching weeds manually or wipe their leaves with a sponge that's been dipped in and herbicide like Roundup.

Love says ornamental grasses are plagued by very few pests.  However, mealybugs-which deposit a cotton-like substance for protection-can stunt Miscanthus grasses and prompt their premature dormancy.  Mealybugs can be controlled by direct streams of water, insecticidal soap or registered insecticides.  Slugs and snails can also chew on grass blades, leaving glistening slime trails in their wake; they're not likely to damage ornamental significantly but can take refuge in them, so you might want to set out pet-safe baits.

Several fungi may also attack ornamental grasses, causing the upper surfaces of older leaves to turn prematurely yellow, orange or brown and the plant itself to eventually decline and die.  To prevent flare-ups of these rust diseases, avoid planting ornamental grasses too densely and remove all dead plant material at the end of the growing season.  If it's too late for prevention and your plants are already infected with rust, try a registered fungicide. 

"If properly placed and well cared for, ornamental grasses can add interest and texture to the landscape that no other plants offer," says Love.  "They are a good addition to any landscape in any climate."

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Monitor the menu if your pets eat your plants

CALDWELL, Idaho—Love your pets? Love your garden?  Ever wonder if the two are compatible?

Yep, you know your plants are sometimes at risk from digging, trampling or smashing dogs and from rolling, clambering and thrashing cats.  But a lot of popular garden plants have their own ways of fighting back—ways that can sicken Fido or Tabby or, unfortunately, even kill them. 

Stephanie Etter, University of Idaho Extension educator in Canyon County, has developed a short list of plants that she cautions gardeners about.  She advises Idaho gardeners to make sure their companionable critters aren’t chewing on azaleas, black walnuts, bleeding hearts, foxgloves, lilies, rhododendrons, yews, grapes, onions, tomatoes or tulip and daffodil bulbs. Etter notes that:

As little as 2 tablespoons of fresh or dried yew can be lethal to dogs or cats.  The alkaloids in yew affect primarily the heart, producing such signs as weakness, tremors, inability to walk, respiratory difficulty, acute collapse and –in dogs- seizures.  Animals that eat as one-tenth of one percent of their body weight in azalea or rhododendron leaves can show signs of poisoning by those plants’ grayanotoxins.  These signs include vomiting, drooling, weakness, central nervous system depressions and erratic heartbeat.  Seriously affected animals can die within a day or two if they’re not treated.  The cardiac glycosides in live or even dead foxglove leaves, stems, flowers and seeds can initially cause vomiting and diarrhea and can progress to a brisk, weak or irregular pulse, rapid breathing and a fatally irregular heartbeat.  “Taken in the right amount, these alkaloids are similar to drugs that are used therapeutically to regulate the heart,” says Etter.  “But over that amount, they can become toxic.” 

Moldy nuts from the black walnut tree can cause rapid breathing, dilated pupils, frequent urination, convulsions and death in dogs; the potentially lethal toxin produced by this mold can also be found in compost piles and garbage.  Pets that eat bleeding heart can suffer muscle tremors and staggering, and cats that eat lilies can succumb to kidney failure.  Tulip and daffodil bulbs can produce diarrhea, vomiting, drooling and lost appetite in dogs.  The leaves, stems, flowers and unripened fruit of tomatoes, potatoes and nightshade plants can cause gastrointestinal upset and muscle weakness in canines and felines.  “Quite a bit” of onions, garlic or chives destroy red blood cells, leading to anemia in dogs and cat, and an unknown number of grapes can cause dogs’ kidneys to stop functioning. 

Your pets and your plants may have coexisted peaceably and uneventfully for years, and may continue to do so, says Etter.  “But if you have a dog that tends to dig up the flower beds or a cat that likes to nibble on a lot of plants, you may want to be careful.”

For more information, visit http://www.aspca.org .  In an emergency when you can’t reach your veterinarian, call your nearest human poison control center for free help (1-800-222-1222) or animal poison control centers for a fee (ASPCA-Animal Poison Control Center at 1-888-426-4435) or Animal Poison Hotline at 1-888-232-8870).

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Gardeners, warm up to cold frames!!      

BOISE,Idaho-Cold frames are hot! June Swanson, University of Idaho Advanced Master Gardener, says many Idaho gardeners could easily warm up to their innumerable uses. 

These any-sized, often-homemade structures-enclosed on all four sides and covered with a clear top-can let gardeners in most Idaho climates grow salad greens all winter long, start cold-hardy vegetable and flower seeds up to eight weeks before the last spring frost, keep cool-season vegetables growing an extra month or two in the fall and harden off young seedlings that were started indoors.  Gardeners can even use them for forcing pots of early-season tulips, daffodils or other bulbs; to root cutting of geraniums, fuchsias, roses or other plants, and to store carrots, turnips, beets and other veggies over the winter-a la root cellar.

Swanson, who gardens organically, loves to see how far she can stretch her growing season, both early in the spring and late in the fall.  "I know it's a lot easier to run to the store and buy a bag of produce, but I just enjoy it," she says.

Much of the fun is in the experimenting.  One winter, when the Swanson's wanted to visit the Southwest for a few weeks, June just tossed blankets over her cold frames.  To her delight, the vegetables inside kept growing, even though they were completely in the dark.

Swanson also enjoys fashioning cold frames from whatever's literally lying around her yard.  The can be made from old lumber, old window frames or retired sandboxes covered with storm windows.  (Just don't use treated wood or creosote-soaked railroad ties, she cautions: the chemicals can leach into the soil.)  Gardeners can even form straw bales or concrete blocks into rectangles and set fiberglass, corrugated plastic or other transparent materials on top.  To let rain and melting snow drain off easily, cold frames are ideally built higher in the back than the front. 

Ventilation is a must: on a clear, sunny day at 40 degrees, the inside temperature can quickly reach 75, Swanson says.  "You need a thermometer inside the cold frame and out of direct sun; when it reaches 70-72 degrees, prop open the cover."  Because ventilation can be tricky-especially if no one is home during the day-to monitor temperature-many gardeners use automatic venting systems that are available commercially.

Swanson fills her cold frames with enriched garden soil-3 inches of soil; 1 inch of peat moss, rotted straw or leaf mold, and 1 inch of compost or well-rotted manure.  After blending the soil, she closes the cover on a hot sunny day to try to cook the soil and fry weed and insect pests.

As to the best place to set a cold frame, Swanson says "location, location, location!"  Frames need sunny spots for maximum winter sun.  Indeed, in just such a spot-protected from north winds-Swanson harvests lettuce and spinach all winter long.  They grow from seed to people feed in sex weeks.  "I like to keep a good supply coming," she says.

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It's Not the Hardiness, It's the Heat

In a world gone ga-ga over gigabytes, it shouldn't be surprising that Idaho gardeners will soon need to learn another digit.  Many already know their USDA Plant Hardiness Zone, but they're being challenged to get chummy with their American Horticultural Society Plant Heat Zone as well. 

Increasingly, plants will be identified by four numbers-the first two representing the range of hardiness zones within which they'll thrive and the second two representing a comparable range of minimum and maximum heat zones.  The USDA Plant Hardiness Zone (developed in 1960, updated in 1990 and currently undergoing another revision) indicates a plant's ability to survive winter cold; the AHS Plant Heat Zone tells buyers about its ability to endure summer heat. 

H. Marc Cathey, AHS president emeritus, says the "effects of heat damage are more subtle than those of extreme cold, which will kill a plant instantly.  Heat damage can first appear in many different parts of the plant:  Flower buds may wither, leaves may droop or become more attractive to insects, chlorophyll may disappear so that leaves appear white or brown, or roots may cease growing."  Death by heat is "slow and lingering," Cathey notes, with plants failing over months or years. 

To find out your plant heat zone, click here Heat Zone Finder. 

To find your Hardiness Zone, click here Hardiness Zone Finder.

Idaho's heat zones range from 2-8. Using 1974-1995 climate data, the AHS chose the average number of days that temperatures exceed 86 degrees Fahrenheit as the basis for the heat zones.  In zone 2, the average number of such days is 1-7; in zone 8, it's 91 through 120.  The AHS assigned altogether 12 heat zones to US sites

Cathey cautions that the heat-zone ratings assume that a plant consistently receives adequate water.  "The accuracy of the zone coding can be substantially distorted by lack of water, even for a brief period in the life of the plant," he says.  Other factors that can skew the heat-zone ratings are oxygen, light, day-length, air movement, surrounding structures, soil pH and nutrients.

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Two New UI Publications Help Homeowners Manage Fruit Trees

    If one of your 2006 gardening resolutions is to subdue the recurring pest problems in your home fruit trees, are yourself with two freshly revised publications from the University of Idaho Extension.

 “Insect Control for Apples and Pears in the Home Garden” and “Insect Control for Stone Fruits in the Home Orchard” can be downloaded for free from the Educational Communications web site www.info.ag.uidaho.edu or purchased fro $1.00 each (plus sales tax, shipping and handling) by calling (208) 885 7982 or sending e-mail to calspubs@uidaho.edu .

 The publications discuss the abundant insect pests that can plague your fruit trees and offer detailed recommendations for overcoming them.  They describe control of aphids, caterpillars, cherry fruit flies, codling moths, European earwigs, leafhoppers, leaf rollers, mites, peach twig borers, pear psyllas, pear slugs, Oriental fruit moths and scale. 

In addition to conventional chemicals, you can read about the potential usefulness of such alternatives as insecticidal soap, neem oil, Bacillus thuringiensis, Beaveria bassiana, sponosad, kaolin clay, adhesives and barriers.  You can also learn how pheromone traps can help you time insect sprays.  Detailed guides in the back of each publication outline which conventional and alternative insecticides to use against which pests and when to apply them. 

Because fruit tree management is an unusually intensive task for the casual gardener, the authors caution homeowners against planting more trees than the can care for.  “Neglected or under-managed fruit trees become a source of pest insects and a problem for neighbors,” they note. 

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Wintertime is Tough on Houseplants

JEROME, Idaho-They're snug and warm inside and getting lots of water and fertilizer, so why do so many houseplants fail to thrive in the winter?

University of Idaho Extension educator Jo Ann Robbins offers a few hints: they're short on light and humidity and, chances are, long on water and fertilizer.  "Ninety-five percent of all problems with houseplants have to do with light, water, humidity and fertilization," she says.  "Frequently, the problem is a combination of these factors."

Take light, for example.  Robbins says that at low light levels, most common houseplants are classified as "long-term perishable" and should be replaced every tow years or so.  Plants need at least 50 to 75 foot candles of light to grow.  They get about 100 foot candles if they're 1 foot from a window but only 25 foot candles if they're 2 feet away.  Winter's shorter day-lengths don't help (tropical plants thrive in 12-16 hours of daylight), but artificial lights can.  So can moving your houseplants very close to-but not touching -your sunniest south-facing windows, where daylight is more intense.

Too little light produces symptoms like weakness, spindliness and long distances between nodes.  Leaves turn yellow and drop-usually beginning from the bottom of the plant-and variegated houseplants revert to solid green.

Too little heat produces other symptoms, so don't leave your houseplants unprotected near uncovered windows at night.  If temperatures are too low, their leaves will curl up, turn brown and drop off. 

Your houseplants may also need less-or more-water than they did during the summer, depending on the environmental conditions inside your home.  Before watering them, Robbins suggest checking for moisture 1 inch or so below the soil surface or tapping the sides of their pots and listening for a hollow sound.  Symptoms of over watering (or poor drainage) include curled, wilted, blackened and dropped leaves and dark-brown or dark-gray soft rotted roots.  Symptoms of under watering include leaves that darken and turn crisp, lower leaves that drop and plants that gradually wilt.

Finally, try to raise the humidity around your houseplants by grouping them together, setting them on top of gravel in water-filled trays, misting them frequently or using a humidifier.  When humidity is too low, houseplants can develop brown leaf tips and yellow leaf margins, and their leaves and buds can wilt, shrivel and drop.

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