Released: February 22, 2007

Annual Scale Hunt Deadline For Yards, Gardens Nearing

MANHATTAN, Kan. – It may be cold, but February is when yard, garden and orchard owners should take time for an outdoor hunt.

“Checking woody plants for scale infestations is easiest when the deciduous plants are bare. February is kind of a deadline, though, because you control scales with dormant oil spray. And, the best timing for that application is before this year’s new leaves bud. For Kansas peaches and nectarines, at least, that usually means by March 1,” said Ward Upham, horticulturist with Kansas State University Research and Extension.

The latest deadline for spraying other plants is just before their buds start to break, he said.

A small infestation of just a few scales, which are tiny insects, won’t harm plants.

“You’ve got to keep an eye on them, though. Scale populations can increase dramatically during the growing season,” Upham said. “Heavy scale infestations can reduce plant vigor, destroy branches and even kill entire plants. They also can do a lot of damage to fruit crops.”

Among ornamental plants, Manhattan euonymus is notorious for scale problems, he said. The sap-sucking insects like all fruit trees and bush fruits, such as blackberries and raspberries.

The vulnerable tree and shrub list can include arborvitae, ash, crabapple, elm, juniper, lilac, linden, maple, oak, pine, spruce and yew. Scales also occasionally attack other ornamental plants, ranging from roses to hollies.

“The problem with identifying scales is they don’t look like your average insect. For example, you won’t see legs or antennae,” he said. “The different kinds of scale insects don’t necessarily resemble each other, either.

“To complicate things further, scales are small. And, for most of their lives, they don’t move – at all.”

Some scale types look much like a scar where a twig once grew, Upham said. Others demonstrate how the insect type got its name – they look like individual fish scales, tightly pressed against a plant part. Examined closely, some of these insects look a bit like small sea shells that are round or oval. But, some look like flare-bottomed oyster shells, and others have even more unusual shapes.

Their coloring varies, but white, tan and brown are fairly common, the horticulturist said.

Virginia’s Extension Service provides an array of scale photos and descriptions on the Web http://www.ext.vt.edu/departments/entomology/ornamentals/scaleinsects.html.

Dormant oil sprays are the only effective control for the overwintering stage of most scales, Upham added. The oils will also control any tiny, newly hatched scales before they have a chance to protect themselves with a covering that will make them impervious to sprays until late next winter.

“Plant injury can occur if the spray freezes,” Upham warned. “So, you’ve got to wait for a day when the temperature will be at least 40 degrees for a while, so the spray has a chance to dry before things drop below 32 F again. To increase the odds the spray will dry properly, apply it in the morning.”

Thorough coverage of limbs, branches and twigs is vital for control, he said.

More information about horticultural pest controls is available at any local K-State Research and Extension office. Upham also maintains an extensive Web library of photos and fact sheets called “Common Plant Problems in Kansas” at http://www.hfrr.ksu.edu/DesktopDefault.aspx?tabid=586.

-30-

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.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News