March 23, 2023

Some Early Spring Insect Pests of Christmas Trees

The accumulation of heat units (Growing Degree Days (GDD) will soon begin to increase rapidly in New Jersey as we approach the early weeks of April. If past histories or present-day monitoring indicate the need for interventions, then the best control windows for numerous insect/mite pests are beginning to occur. The following is an incomplete listing of a handful of some of our early-season Christmas tree insect pests that may need to be scouted & possibly controlled. Those included in this blog are the European pine sawfly, Eastern spruce gall adelgid, Cooley spruce gall adelgid, Nantucket pine tip moth, Pales weevil, White pine aphid, & Pine bark adelgid.

Christmas trees in field

After many years, these slow growing Colorado blue spruce trees are close to reaching their peak selling growth stage as Christmas trees. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

 

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Filed Under: Christmas Trees, Nursery, Plant Diagnostic Lab
March 13, 2023

White Pine Weevil: Overwintering Adults Become Active in March & April

Many arborists & landscapers often find it difficult to prevent white pine weevil pests (Pissodes strobi), because they are typically applying fertilizer & dormant oil treatments during the control window. In the state of NJ, the control window against feeding white pine weevil adults occurs in March & April. Adults over-winter in the duff beneath trees. The WPW adults will often crawl or sometimes fly to the top terminal leaders of pine, spruce, or Douglas-fir trees. Eastern white pine & Norway spruce species are the most severely attacked & the death of the terminal leaders of these trees will often occur.

Treatment timing is critical with this pest and controlling the adult female before egg laying is necessary. Apply preventative sprays (e.g., pyrethroids) only to the terminal leaders during this time. Before mating & egg laying, adults will feed by chewing holes within the central leader & cause a characteristic pitch flow that becomes white in color when dry. Then females will lay eggs in new cut-out holes within the top 12 inches of the leader just below the terminal bud. This blog will describe with the help of photographs the 7-stage lifecycle of this native weevil borer. Control & management options will also be provided.   

Beetle on stem

White pine weevil adults are about 1/4+ inch long & have a long snout with two white spots on back of wing covers. Adults feed at terminal leaders during March & April. Most eggs will then be laid during April & May. (Photo Credit: Michigan State University)

 

Infected pine tree

Severe white pine weevil infestations to terminal leaders can destroy two or more years worth of growth to pine, spruce, & Douglas-fir trees. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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Filed Under: Christmas Trees, Landscape, Nursery, & Turf, Nursery, Plant Diagnostic Lab
January 26, 2023

Nostoc in Nurseries: Herbicides to Control the Slippery Slime Threat

 

Nostoc is a cyanobacterium and is one of the oldest organisms on earth (over 3.5 billion years). It is a primitive growth, like algae, moss, and liverwort. Many years ago, it was incorrectly identified as blue-green algae. Nostoc has no roots, no vascular tissues & is not a plant but it is photosynthetic. It can be found growing within gravel, stones, limestone chips, granite, saturated soils & on-ground cloth within container nurseries. It can tolerate long periods of desiccation but requires plentiful amounts of water for establishment. This cyanobacterium growth can become common & persistent at certain nursery/greenhouse sites where long-term overhead irrigation is done.

Nostdoc growing in front of container

Nostoc growing in front of container bay opening. The opening allowed the overhead irrigation to saturate the soil/gravel at entrance. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Nostdoc on ground

Nostoc growing on ground cloth within a nursery container bay. Creates a serious slipping hazard for nursery personnel. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Nostoc is not toxic & does not directly compete with nursery/greenhouse crops or landscape plants, but it can harbor fungus gnats & snails. Nostoc first became a growing concern in nurseries approximately 30 years ago. Slipping hazards are the primary threat this organism poses to nursery & greenhouse personnel. It forms gelatinous masses composed of filaments linked together by protective jelly-like coverings. This creates a surface as slick as wet ice. Nostoc can occasionally be found growing within turf or landscape settings but is not common.

This blog will show with photographic images how Nostoc can be identified & will also review available control options.      

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Filed Under: Nursery, Plant Diagnostic Lab
October 12, 2022

Autumn Pest Review: Soft Scales, Leafminers, Aphids, Mites & Adelgids

AUTUMN PEST REVIEW: Although the season is beginning to wind-down, there are still a number of insect & mite pests that require scouting during the fall weeks. The pests discussed in this blog include soft scale nymphs, boxwood leafminers, white pine aphids, spruce spider mites, southern red spider mites, hemlock rust mites, eastern spruce gall adelgids & hemlock woolly adelgids. The use of low %-rates of horticultural oils this fall can be especially valuable against controlling many of these pests.

SOFT SCALE NYMPH MIGRATIONS: Most soft scale species (exceptions include magnolia, tuliptree, and globose) have 1st instar nymphs that spend July and August feeding along veins on the undersides of leaves of their deciduous host (the use of a hand lens may be needed). During the weeks of late summer and early fall, these nymphs migrate off the leaves onto woody stem tissue and molt into the overwintering 2nd instar stage. The size of the nymphs increases 3-times after molting and their presence is usually observable even without magnification (they can be as large as lenticels). Typically, overwintering soft-scale nymphs have a dark coloration, to help absorb sunlight and maintain body warmth.

European elm 1st-instar nymphs settled along the main vein underneath elm leaf. During the early weeks of fall they migrate from leaves onto the bark to overwinter. (Photo Credit: Cornell University)

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Filed Under: Landscape, Nursery, & Turf, Nursery, Plant Diagnostic Lab
October 7, 2022

Why Do Spruce Christmas Trees Show Interior Needle Discoloration?

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.

K & Blue Spruce2

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

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Filed Under: Christmas Trees
October 3, 2022

Spruce Spider Mites: A Key Cool Season Mite Pest

Spruce spider mite species (Oligonychus ununguis) are found in Christmas tree farms as well as landscapes & nurseries in the New Jersey region. The late weeks of September & early weeks of October are transition periods for this cool season mite. With the arrival of autumn & cooler temperatures, the spruce spider mites begin to “wake up” from their summer dormancy & will be observed feeding & laying eggs. Observations this past week in Christmas tree farms have shown increased activities of the spruce spider mites. This spider mite species will feed exclusively on various conifers including spruce, fir, Douglas-fir, hemlock, Cryptomeria, arborvitae, false-cypress, pine, & juniper.

Christmas tree farm

This Christmas tree farm is an ideal site for potential spruce spider mite infestations. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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Filed Under: Christmas Trees, Landscape, Nursery, & Turf, Nursery, Plant Diagnostic Lab