Check Pines Now for Stress, Disease 2/27/03

MANHATTAN, Kan. – Pines in the High Plains have faced several years of tough conditions that mixed weather stress with diseases.

Drought and the always-fatal pine wilt disease already have taken a severe toll. (See sidebar.) To protect the pines that remain, owners should start checking their trees now, said Ned Tisserat, plant pathologist with Kansas State University Research and Extension.

"Early spring is one of the better times for telling pine problems apart," he explained. "And mid to late spring is each year’s one-time-only chance to apply many pine disease controls."

Chop, Chip Dead Scots Pines by May

MANHATTAN, Kan. –– May is the absolute deadline for removing and either chipping or burning ALL dead Scots pines in Kansas.

"Even if they’re victims of drought, they can help foster a deadly disease called pine wilt," said Ned Tisserat, plant pathologist with Kansas State University Research and Extension.

In a matter of just a few years, pine wilt has become epidemic in eastern Kansas. It has spread through the state’s center and started killing pines in the west.

The disease’s symptoms show up in August-November. It can kill a mature Scots pine – and the occasional Austrian pine – within weeks.

But pine wilt spreads in the spring.

The pine sawyer beetle "transports" the disease-causing nematode. It lays eggs each fall in dead and dying pines. If a female beetle lays eggs in a nematode-infected tree, all of her offspring can be contaminated by the time they emerge and scatter late the following spring.

"If we don’t stop this cycle, statewide, we could be in danger of losing a lot of Scots pines that Kansans have gone to the trouble of planting," Tisserat said.

Kansas has no native pines.

Pines that were too dry through winter will have yellow needle tips now and may have yellow to tan bands along the rest of the needle.

Nothing will reverse this damage, "which is likely to be widespread this year through much of Kansas," Tisserat said. Still, the symptoms can signal a pine that needs tender loving care.

"Stressed plants always are more vulnerable to diseases and insects," he warned.

Unfortunately, Austrian, mugo and older Ponderosa pines can exhibit similar symptoms now if they have a disease called Dothistroma Needle Blight. Disease symptoms emerge in fall, but by spring are causing brown needle tips, often combined with discolored bands or spots.

Soon the needles’ base will turn brown, too. This will cause months of premature needle drop that can seriously weaken Austrian and Ponderosa pines – plus give them a strange "tufted" look.

"In late winter or early spring, the fungus that causes Dothistroma produces small black "fruiting" bodies that erupt through the surface of the needle," Tisserat said. "So, if you can identify them now, you’ll be able to control the disease in May-June and keep it from infecting this year’s new growth."

Scots pines typically are resistant to Dothistroma Needle Blight. But they and Ponderosa pines both can get a disease that looks similar – Brown Spot. By winter, the needles it affects usually are dead and sometimes start to drop. If they’re still around now, they’ll be totally brown.

"The only way you can diagnose Brown Spot at this time of year is by sending a sample to a lab. If you’ve got a Christmas tree plantation of Scots pines, though, a lab test might be a good investment. The best timing for controls is the last week in May or early June," the plant pathologist said.

Sphaeropsis tip blight kills needles, new shoots and even branches. It’s most likely to attack Austrian pines, but can affect Ponderosa, Scots, and mugo pines, too.

"We ‘ve got several months before we need to start looking for this year’s first Sphaeropsis symptoms. They develop by killing the tips of whole branches when the year’s new needles are about half-grown. As a result, the needles on the branch tip generally end up shorter than normal and may produce small droplets of resin," Tisserat said.

Dropping Pine Needles Don’t Always Mean Stress

MANHATTAN, Kan. – High Plains pine trees are having all kinds of problems now. But not every pine tree is a victim of weather stress, disease or insects – even if it’s shedding dead needles.

"Evergreens don’t keep all of their needles indefinitely," said Ward Upham, horticulturist with Kansas State University Research and Extension. "Pines, spruces and arborvitae are particularly prone to noticeably drop their older needles – the ones on the inside of the branch, closest to the trunk."

This is a natural process. It normally occurs in fall at the end of the growing season, he said.

Nonetheless, natural needle drop can happen all at once or be a gradual process, Upham added. Some evergreens keep their older needles for just a year. Others, including the Ponderosa and Scots pines, hold onto needles for up to three years.

So, in most cases, homeowners have no reason to worry unless the needles on the branch tips are becoming discolored or dying, too.

Sphaeropsis tip blight tends to start with lower branches and work its way up. Typically, the infected needles do not drop.

The Sphaeropsis fungus survives from year to year in pine cones and dead shoots and branches. It can even affect older shoots and larger branches, if they suffer "mechanical" damage from hail or insects. Repeated infections over several years can kill large branches or even the entire tree.

"Unfortunately, you must control this disease when new shoots are 1 to 2 inches long – often in mid to late April. So, you need lab results to know whether to apply controls this year. Otherwise, you’ll need to scout for symptoms later this spring and remember to treat infected trees next year," Tisserat said.

Local Research and Extension offices can provide specific information about the best way to control each disease. They can send photos of diseased branches by computer to diagnosticians at K-State. They also can forward a sample branch and lab fee to the Plant Disease Diagnostic Lab in Manhattan for testing.

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.