MANHATTAN, Kan. -- Pioneers saw nary a pine when covered wagons crossed Kansas’ plains.

Since then, the stately evergreen tree has become a favorite in landscapes and windbreaks.

But keeping pines healthy in Kansas’ non-native environment can still be a challenge, according to Kansas State University scientists. In some cases, long-established trees can be even more vulnerable than bare-root or balled-and-burlapped seedlings.

To avoid disappointment with pines planted this spring, Kansans should know the risks, the scientists said. [See below.] They should note which species are vulnerable to life-threatening damage in their region. They should assess whether they’ll be willing to invest effort and cash if a disease or insects attack.

For pines already on their property, residents should go on the alert now. Most of the state’s major pine pests become vulnerable to controls only in April-June.

For example, the mugo pines in many landscapes could be showing obvious feeding damage as April ends, said K-State Research and Extension entomologist Bob Bauernfeind.

That’s when European pine sawfly larvae become large enough to stop stripping needles’ outer layer. Instead, they consume entire needles, leaving bare spots in infested pines.

For a limited infestation, pruning off and disposing of affected twigs is all that’s needed, the entomologist said. More often, however, controlling the European pine sawfly requires spraying an infested tree thoroughly before the larvae stop eating -- typically in mid-May.

Plant pathologist Ned Tisserat added that May 1 is an important deadline for Scots pine owners, which include the lion’s share of the state’s Christmas tree growers. If Kansas’ former Scots pine owners don’t get rid of their dead trees by then, pine wilt may continue its recent and seemingly ever-increasing killing spree.

The disease is epidemic in eastern Kansas, Tisserat said. It’s expanding through the central part of the state, and it showed up last year for the first time in at least two southwestern counties.

Bauernfeind said the pine sawyer beetle carries the nematode responsible for pine wilt. The beetle’s larvae and the pinewood nematode both overwinter in infected pines. Each beetle that emerges the following spring can take up to 100,000 nematodes along for the ride.

The nematodes leave their "carrier" and enter living pine tissue through the wounds caused by the beetle’s feeding, Tisserat said..

"This creates the potential for pine death in the near future," Bauernfeind said. "Depending on when a tree begins to look off-color, it can go from green to a burned-looking brown within weeks."

Tisserat added, "The saying around Wichita now is ‘If your Scots pine is brown, cut it down.’ But you can’t even leave a stump from affected pines. You also must chip, burn or bury infected wood to stop this year’s pine sawyer beetles before they mature enough to fly."

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Symptoms: Affected needles get yellow-tan spots (often resin-soaked and sometimes "banded") in late August - early September. Black fruiting structures also appear in fall.

Controls: Infections spreads through growing season, but peaks in early June as new needles are developing. Bordeaux mix, mancozeb or chlorothalonil can protect trees if applied in late May or early June (and again 3 - 4 weeks later if the weather’s wet).

Special Considerations: Scots pines being grown for Christmas trees seem to develop the worst infestations. Infected needles may either drop to ground or stay on tree.

Pine Hosts: Austrian and ponderosa (especially older), plus mugo. Scots are resistant.

Symptoms: Dark green bands or scattered yellow-tan spots enlarge into red bands in late summer - early fall; needle tips turn brown, base stays green. In late winter - early spring, tiny black fruiting structures rupture through infected needles; the base of needles turns brown. Premature needle drop follows through spring and summer.

Controls: Spray one of the appropriately labeled copper-containing fungicides. One application in early June may do the job. But a spray in mid-May, followed by one in mid- to late June can provide better protection.

Special Considerations: Austrian and ponderosa pines keep needles three to four years, so premature needle loss can reduce tree vigor, as well as give new growth a "tufted" look. New growth will be susceptible to fungus spors by midsummer. Injury may look like needle scorch or chemical damage, but those problems don’t "fruit" or rupture needles.

Pine Hosts: Mostly Scots and mugo. All state pines susceptible

Symptoms: Larvae mostly overlooked until twisted, brown needles appear in April (with small larvae tightly packed underneath) and whole branches become bare in early May (as larvae grow and are able to eat whole needles).

Controls: Apply an appropriately labeled product containing Orthene, Dursban, sevin, or horticultural oil/soap before larvae stop feeding in mid-May. Or, for a light infestation, remove affected branches.

Special Considerations: Pest finishes eating before new needles arrive. Tree may look like trimmed poodle, but this won’t kill plant in one season. Ponderosa damage may look like Dothistroma needle blight, so require a lab analysis.

NANTUCKET PINE TIP MOTH (insect)

Pine Hosts: Most serious on Scots under 6 feet tall.

Symptoms: Three generations of small orange larvae bore into the shoots of two-needle pines, killing needle tips.

Controls: Spray appropriately labeled product containing acephate, carbaryl or chloropyrifos 10 days after each moth flight begins, often in late April to early May, then late June to early July, and finally late July to early August.

Special Considerations: Problem worst for Christmas tree growers (who use "traps" to gauge when moth flights peak). Experience suggests first flight in Kansas peaks when the Snowdrift crabapple reaches full bloom

PINE NEEDLE SCALE (insect)

Pine Hosts: Mostly pines in eastern U.S. (and Kansas).

Controls: Use appropriately labeled product containing acephate, chlorpyrifos, carbaryl or diazinon as soon as "crawlers" appear (before they have time to form a waxy protective cover).

Special Considerations: In very early spring, a dormant oil treatment can kill overwintering pine needle scale eggs. Unchecked, scales can eventually kill pine twigs, branches, even entire trees.

PINE WILT (insect carried, nematode caused disease)

Pine Hosts: Scots most susceptible; Austrian and ponderosa can get. Disease is epidemic in east and already is spreading into all but northwest Kansas.

Symptoms: Infested pines wilt, yellow, turn brown, and die within three months -- generally in late summer or early fall. Symptoms may be uniform or branch-by-branch. Dead needles stay attached up to a year. Twigs and branches are brittle.

Controls: "If a Scots pine is brown, cut it down" -- before May 1. Don’t leave a stump. Chip, burn or bury the wood. That’s the only way to stop the year’s newly emerging pine sawyer beetles, which carry the infecting pinewood nematode from dead trees to vulnerable pines.

Special Considerations: A sawyer can carry 100,000 pinewood nematodes, so dead pine removal MUST be communitywide. Early pine wilt damage can look like winter burn, but that problem leaves branches flexible, not brittle.

Pine Hosts: Austrian and ponderosa (especially older), plus mugo. Scots and white, less susceptible.

Symptoms: New candles don’t elongate properly in late May to early June; stunted needles turn a dull tan-brown and often are resin-soaked as they die back. In late summer, small black fruiting structures appear at base of stunted needles and on two-year-old cones.

Controls: Apply thiophanate-methyl, Mancozeb, propiconazole or an appropriately labeled copper-containing fungicide in the third week of April when new shoots are 1-2 inches long (i.e., needles are breaking out) and again 10-14 days later. Also, don’t crowd trees, avoid soil compaction, and apply water as needed, to reduce the stress that can make latent cases emerge.

Special Considerations: Skipping preventive sprays may spur development. Sprays may be less prudent than tree replacement in large windbreaks. KSU micro-injection trials have not shown such products to be effective. Disease may require a mid-May spray in wet years. Blight can look like winter damage (which kills shoots BEFORE needles emerge) and pine tip moth injury (which causes hollow buds that may hold a larvae).