Integrated Pesticide Management

Plant Pests to be scouting for and be proactive against controlling now include:

Eriophyid Mites on Hemlock and White Pine are cool season mites that turn needles a yellow-green to an olive green color and if the infestation is high can eventually cause major leaf drop.

Spruce Spider Mites are also active in cool spring weather and can attack many of our conifer plants (Spruce, Arborvitae, Junipers, Firs, and Pine). Eggs can be seen with a hand lens in the bud area or look for yellowish to off white stippling on the undersides of needles.

Southern Red Mite, another cool season mite become visible on the undersides of Holly, Pieris, Camellia, Azalea and Rhododendrons leaves.

For all mite control, if detected early, use of a 2% horticultural oil to reduce egg and adult mite populations. Miticides may be required if populations go undetected and build to damaging levels.

Eastern Tent Caterpillar adults are not active until April but their eggs cases are easily detectable. Look for blackish ¾” styrofoam egg cases on branches of susceptible plants such as Crabapples, Cherry, Apple, Plum, and other deciduous trees. Simply prune out the masses during the dormant season. Once nests are visible in the tree in April, simply destroy the web contents.

Scale Insects such as Pine Needle Scale, White Peach Scale, White Prunicola Scale and Indian Wax Scale are easily detected on deciduous plants such as Spirea, Barberry, Quince, Lilac, Privet, Japanese Holly, Euonymus, Yews and Azaleas. Examine braches and look for white wax coverings. Look for branch dieback and prune off heavily infested branches if possible. Depending on the scale species, dormant oil applied during the crawler stage can reduce the use of residual pesticides later. Deep root systemic injections offer up to a year or two of control for plants heavily affected.

Boxwood Leafminer can cause blister-like botches to appear on infested leaves because feeding occurs in fall through late winter. Deep root systemic injections in March will reduce adult emergence in late April.

Diseases that are favored by wet weather and humidity include:

Kabatina and Phomopsis Tip Blight- both affect Junipers and symptoms often look alike but the development of infection and control are different. Kabatina blight requires a wound for the pathogen to enter primarily in late summer but visible symptoms don’t show up till spring, earlier than Phomopsis blight symptoms. Look for branches that turn dull green, then red or yellow.

Examine plants for small, ash gray to silver lesions at the base of discolored tissue. Phomopsis blight affected new needle growth and succulent branch tips and cause blighting of the terminals during the growing season. Foliage will turn dull red or brown and eventually a ash gray color. Pruning of diseased branches during dry summer weather is the best control option. Avoid excess pruning or shearing in early spring. Juniper varieties vary in susceptibility, so use resistant cultivars when possible.

Cedar Apple Rust- Cedar-apple rust is one of several similar fungal diseases which could be broadly classified as Juniper-Rosaceous rusts. Each species spends part of its life cycle on a juniper host and part on one or more hosts in the rose family, and require both hosts to complete their life cycles. Two other common juniper-rosaceous rusts are hawthorn rust and quince rust, although there are many more.


Examine for swollen growths or woody galls on branches or shoots. Once mature in spring, bright orange, gelatinous, spore-producing growths emerge from the galls. In severe cases these rusts may be managed with fungicides, however registered fungicides will vary by the type of plant(s) to be treated and their use or site. In addition, there are resistant varieties of juniper, apple, crabapple, and hawthorn available for use in new plantings or when replacing severely diseased specimens. There may also be some potential for control by eliminating nearby juniper hosts, or removing galls from hosts before sporulation occurs, however, this is not always practical because the spores can travel several miles by wind to infect the alternate hosts (Cornell Fact Sheet).