Landscape - Spruce Spider Mites

Spruce spider mites can build up during cooler weather in late summer. The following is more information.

Spruce spider mites feed on fir, arborvitae, spruce, and other conifers. This mite feeds on older foliage first and damaged foliage has a yellow to bronze coloration. Spruce spider mites begin to feed about 2301- 3957 [3094 peak] GDD base 50 and usually continue until a hard frost. The mite is dark green to dark red after initial feeding and overwinters as a reddish colored egg. The
damage found during the summer on plants is the result of heavy feeding by this mite the previous fall and spring.

Spruce spider mite infestation with webbing. Photo from the USDA Forest Service - Northeastern Area Archive, USDA Forest Service, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Turf - Fall Control of Broadleaf Weeds

There is still time to apply broadleaf herbicides in turf this fall. Good control of many broadleaf weeds is obtained this time of year. The following is an article on the subject.

We are now in the prime season for broadleaf weed control. Actually there is plenty of time left for good control. Nebraska research reported in 2002 showed 2,4-D and/or dicamba were far more effective in controlling dandelions and Canada thistle when applied 1 to 10 days after the first fall frost than when applied 5 to 11 days before the frost. Earlier work by Bruce Branham at Michigan State showed that even though early September applications were effective in controlling broadleaves yet that same fall, Sept applications were less effective long-term than applications made in October and November. Our more recent work on ground ivy shows that herbicides like triclopyr (Turflon) that are very effective on ground ivy, retain their effectiveness when applied as late as early- to mid-November. However, herbicides with lower activity on ground ivy were most effective from Oct 1 through Nov 1, and efficacy decreased outside of this window. The take home message is broadleaf applications should be effective when made into the first week or two of November, but control may not be seen until spring. However, herbicides that contain carfentrazone (FMC’s Quicksilver, PBI Gordons’ Powerzone and Speedzone) will still give a response in 7 to 10 days even when applied in late October or early November.

Information from the September 27 Turf Tip by Zac Reicher, Professor/Turfgrass Extension Specialist, Purdue University.

Landscape and Nursery - Cool Season Mites

The following is information on cool season mites in the landscape. These mites will be more active now with the reduced temperatures.

COOL SEASON MITES.

As temperatures consistently return to the 60's and 70's during the next few weeks, spruce spider mite and southern red mite activity will increase. Spruce spider mites feed on fir, arborvitae, spruce, Douglas-fir, and other conifers, feeding on older foliage first. Spruce spider mites are olivedark red with reddish-yellow legs and two reddish eye spots with a pale stripe down the back (visible with a microscope). Spruce spider mites start feeding in the fall around 2301 3957 [3094 peak] GDD and continues until there is a hard frost. In the summer, damage appears as bleaching, yellowing, stippling or bronzing of the needles. Damage visible on trees in summer is from intensive fall feeding.

Southern red mites feed on a wide variety of plants including azaleas, camellias, hollies, clethra, juniper, elaeagnus, hibiscus, photinia and rose. Nymphs and adults are active starting around 2401 3584 [3034 peak] GDD and 1913 3518 [2933 peak] GDD respectively. This mite has a dark reddish to brown abdomen with a pinkish to red cephalothorax and a pale mid-stripe. It feeds on the lower leaf surface but during high populations may be found on upper surfaces. Damaged leaves may be brown to gray and drop prematurely.

Monitor with a clipboard and a white sheet of paper, looking for dots the size of periods. Watch for predatory mites and small lady beetles; both are predators of the spruce spider mite and should be conserved. Miticides available for control include hexythiazox (Hexygon, Savy), bifenazate (Floramite), abamectin (Avid) and others. Research has shown bifenthrin (Talstar) can cause mite 'resurgences' because natural enemies are killed; thus mite eggs are able to hatch without threat of predators.

Information from Dr. Brian Kunkel, Ornamental IPM Specialist, UD

Landscape and Nursery - Mites Present Now

The following are two mite pests to look for in the landscape and nurseries now and in the next 2 weeks. Information is from the University of Maryland.

Spruce Spider Mite, Oligonychus ununguis

Spruce Spider Mite. Photo by Petr Kapitola, State Phytosanitary Administration, Bugwood.org

Spruce spider mite hatches at about 30 - 50 degree days. We have reached this point in most of Delaware at this time.

Host: Look for spruce spider mites on junipers, spruce, arborvitae, cryptomeria, dawn redwood, hemlock, and pine.

Monitoring: Examine twigs for red eggs, usually near the base of the needles. The nymphs that are hatching are light colored. You can place a clipboard with white paper under the tree branches, rap the branches several times, and examine what’s crawling on the paper using a 10 -15 X magnification lens.

Control: Horticultural oil works very well on this mite. The mite growth regulators Hexygon and TetraSan work well when applied to young populations of mites. Avid, Floramite and Acari are some other options.

Boxwood Spider Mite, Eurytetranychus buxi

Boxwood Spider Mite. Photo from Rayanne Lehman, Pennsylvania Department of Agriculture, Bugwood.org

Boxwood spider mite overwinters as eggs and should be hatching in early April in most of Delaware. They have multiple generations per year but they become less active as we move into the hot part of the summer.

Hosts: English and European boxwood

Host resistance: Japanese and Korean boxwood tend to be less susceptible to boxwood mite

Monitoring: Use the clipboard/rap test for this mite. The mites will be tan colored with relatively long legs.

Control: Avid, Hexygon, horticultural oil, insecticidal soap

Information modified from the March 28 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers, University of Maryland Cooperative Extension. http://ipmnet.umd.edu/08Mar28L.pdf

Ornamentals Hotline Pictures for the "What's Hot" Section of Issue 26, October 12, 2007

Brown marmorated stinkb bug adults and nymph.

Photo by Gary Bernon, USDA APHIS, Bugwood.org

Western conifer seed bug.

Photo by Whitney Cranshaw, Colorado State University, Bugwood.org

Southern red mite.

Photo by John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org

Spruce spider mite with webbing.

Photo from USDA Forest Service - Region 4 Archive, USDA Forest Service, Bugwood.org

Ornamentals Hotline Insect Pictures for Issue 25, September 21, 2007

SPRUCE SPIDER MITES. Spruce spider mites are “cool season”
mites commonly found feeding on fir, arborvitae, spruce,
Douglas-fir, and other conifers. Their sucking mouthparts cause
bleaching, yellowing, stippling or bronzing of the needles.

Spruce Spider Mite Pictures from USDA Forest Service - Region 4 Archive, USDA Forest Service, Bugwood.org