GardenLine | Common Saskatchewan Pests | Pine Needle Scale

Bonnie Willie

Description:

Pine needle scales are white, elongate to pear-shaped and approximately 3 mm in length. They resemble flecks of white paint on the needles of the host trees.

Hosts:

Although the name pine needle scale implies it as an insect of pine trees, the most common hosts for this insect are White and Colorado spruce. Scot's and Lodgepole pine, the Douglas-fir and other spruce species are also affected by pine needle scale in the prairie provinces.

Damage:

Scale insects feed by sucking sap from their host plant. Their feeding can reduce plant vigour, make it more susceptible to injury caused by drought, harsh winters, disease and other insect infestations.

In order for the scale insect to feed, it must pierce the needle to remove the sap. As it does, it causes yellowish green spots to develop. In a severe infestation, the spots will coalesce and needles will drop prematurely. The needle's size may be reduced to half of the normal length and the branches will take on an unhealthy - grey appearance. If the host tree is subject to severe infestations, year after year, twigs, branches or even young trees may die.

Control:

Natural control: Lady beetles and small wasp-like parasites offer important natural controls. Heavy rains in mid-June will destroy many of the newly hatched nymphs.

Chemical control:

Trees should be sprayed thoroughly, shortly after the new growth has appeared in early or mid June. A second application should be applied in early August to control any survivors. There are several chemical controls available for control of pine needle scale. They include: malathion, dimethoate (Cygon), diazinon, or carbaryl (Sevin). (Malathion should not be used when the air temperature is below 20 degrees C.) Whichever chemical control you choose, ensure that the product is mixed according to the directions on the label and follow all safety precautions specified for that product.

SOURCES:

Pine Needle Scale by D.S. Kusch; Northern Forest Research Centre; 1977.

The Scale Insect: A Pest Easily Overlooked by Grant Wood; Department of Extension, University of Saskatchewan.

Insect Pest of the Prairies by Hugh Philips and Ernest Mengersen; University of Alberta Environmental Centre; 1989.

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.