In New Jersey, dormant oils (3-4%) are typically applied during March & April. However, many landscapers also apply dormant oils during the late fall months. Dormant oils have proven to be an effective material against a wide range of insect/mite pests & their eggs. Typical landscape pests targeted include spruce spider mites/eggs, southern red spider mites/eggs, oak spider mite eggs, aphid eggs, soft scales, armored scales (to a lesser degree), hemlock rust mites, spruce gall adelgids, lace bugs (deciduous plants), cankerworm eggs, psyllids, plant bugs, etc.

Effective dormant oil sprays require
coverage, coverage, coverage.
Photo credit: SK Rettke of RCE

Some overwintering eggs such as Cankerworm eggs can be effectively destroyed by dormant oils.
Photo credit: Utah Extension.edu

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Occasionally, observations of White Spruce (Picea glauca) or Colorado Spruce (Picea pungens) within landscapes, nurseries, & Christmas tree farms will show current needle growth having a blue or blue-green color, but with older, inner needles having lost the desirable color and turning pale or even yellow. Although sometimes seen on Norway Spruce, these symptoms are most common on the White & Colorado Spruce species. Sometimes symptoms can become dramatic and initiate both aesthetic and plant health concerns. Although the reasons for such symptoms can be from a complex number of conditions, a compromised root system is typically the underlying cause.

Colorado Spruce showing symptoms of undesirable discoloration of older, inner needles. Photo Credit: Steven K. Rettke of Rutgers Coop. Ext.

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During the later weeks of summer & early weeks of fall the mysterious removal of bark sections typically found on branches of Birch, Rhododendron, and Lilac can sometimes be observed. These girdled or stripped bark sections are probably being done by European Hornets. These vespids have been reported to potentially have a worse temperament than timber rattle snakes.

River Birch branch girdled by European Hornets.
Photo by SK Rettke of RCE

European Hornet actively foraging on bark & sap of Birch branch. Photo by SK Rettke of RCE

Armored scales are generally regarded by green industry plant managers as being one of the more difficult insect pests to control. The Cryptomeria scale (Aspidiotus cryptomeriae ‘Kuwana’) is an armored scale that is notorious for being especially difficult to detect because of the translucent waxy cover. The elongate hemlock scale species resembles this scale, but it has a waxy cover that is caramel brown in color. Although the hosts of Cryptomeria scale can potentially include numerous conifer species, they are most typically found on hemlocks & pines in the landscape and on true firs in production situations such as Christmas tree farms. The damage potential is especially high on true firs.

Signs of Cryptomeria scales beneath needles
(Photo: Steven K. Rettke, RCE)

Chlorotic banding & mottling symptoms produced by Cryptomeria scales on Fraser fir (Photo: Steven K. Rettke)

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Damage from previously active White Pine Weevil larvae (Pissodes strobi) has been evident for the past several weeks on Eastern white pine, Norway spruce, Siberian spruce, Colorado blue spruce, & Douglas-fir. The larvae began feeding within the terminal leaders last April. When the terminal leader is heavily infested, larvae feed side by side in a ring encircling the stem. By late spring or early summer, most White Pine Weevil larvae have pupated & emerged as adults. The terminal leader has become stunted and wilted. It is too late in the season to save the leader and it should be pruned out. To re-establish a new leader and retain the desirable Christmas tree shape read further & follow the procedures suggested.

The 2014 leader & laterals of this Eastern white pine were killed by White Pine Weevils this past spring. Photo Credit: Steven K. Rettke of RCE

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