TREE TIPS TREE & SHRUB CARE FROM BARTLETT TREE EXPERTS

Damaging Mites by Gretchen V. Pettis, PhD Bronze Birch Borer in the Pacific Northwest A close cousin of the beneficial garden by Gretchen V. Pettis, PhD spider can cause extensive damage to many types of trees and shrubs. They are minute, plant-feeding arachnids appropriately called A small, native, metallic brown beetle has become more apparent in hot, dry weather. As you mites. These eight-legged arthropods feed on developed a big taste for European and Asian look closer, the bark may have a rippled, ridged chlorophyll, often on the undersides of leaves. white-barked birch trees (Betula spp.). But, it will texture due to the larval tunneling underneath. Mite feeding appears as bleached gladly feed on any birch in its path. The bronze Upon even closer inspection a telltale ¼ inch or bronzed foliage. birch borer (Agrilus anxius) is about ¼ inch to D-shaped hole will let you know that adult beetles ½ inch long and has become a wide-spread have bored their way out of the tree to produce landscape pest. Stressed or weakened birch trees another generation. On the sunny side of the tree are most susceptible to attack. The larvae of this in spring, you may even catch a glimpse of the flatheaded wood boring insect create extensive, beetle causing the damage. intricate feeding tunnels under the bark, cutting Because trees that are weakened or stressed are off nutrient and water flow. Beetle infestations prime beetle targets, it is particularly important can cause significant tree decline and, if left to control other birch pests such as aphids, scale unchecked, can lead to tree death in as little as insects and leafminers to minimize defoliation or two to three years. injury. Mulching and adequate watering of this With such a small insect hidden under the bark, shallow rooted species is particularly helpful. how will you know if your birch tree has been If discovered early enough, beetle populations targeted? The answer is to look up and then look can be successfully controlled with systemic Because mites can reproduce rapidly, damage closer. The first apparent damage due to birch insecticides and the tree restored to health. may not even be noticed until a vast population beetle borer infestation is sparse, yellowing is causing obvious damage and, often, leaving foliage at the crown of the tree. You may also These two trees are showing symptoms of birch borer see dieback of small branches. These symptoms infestation - sparse, yellowing foliage at the crown of the tree unsightly webbing on leaves. For this reason, and dieback of small branches. early season management is critical to prevent large infestations. Effective biological control with predatory mites is also possible when pest mite populations are low. Two particularly damaging mites in the Pacific Northwest are the spruce spider mite (Oligonychus ununguis), which affects many conifers, and the twospotted spider mite (Tetranycus urticae) which affects numerous species of broad leaf trees and shrubs. Hot dry weather seems to increase mite populations and drought stressed trees are more likely to be attacked. Keeping plants sufficiently healthy, hydrated and mulched, and being careful not to over-fertilize, is the best protection against infestation. Early season plant scouting vigilance and treatment will more than pay off by keeping harmful mite populations in check. Many people have a particular aversion to spiders even though these ‘creepy crawlies’ are considered among the top ten best natural enemies of plant pests. But, in this case, its the eight-legged critters you don’t see (mites!) that An adult birch borer and the telltale D-shaped may be the scariest…for your plants, that is! hole left where it bored out of the tree. Maintenance Calendar for Trees & Shrubs JUNE Add a thin (2") layer of mulch around trees and shrubs to conserve moisture and keep roots cool through summer. Deep water every 7-10 days when rain is lacking. Check plants for insect infestations. Apply a second application of tick treatment to landscape perimeters. Ornamentals - Remove faded flowers and seed pods from spring blooming woody ornamentals. Prune as needed. Evergreens, such as boxwood - Conduct maintenance pruning to maintain formal shape. Fruit trees - Thin fruit leaving 6-8" apart. Prop up heavily loaded fruit branches. Tree Focus- Roses - Apply foliar disease and insect control treatments. Japanese Maple (Acer palmatum) Azalea - Scout for and treat azalea lace bug History  Like many maples, prone to formation of infestations. Native to Japan and parts of Asia, Japanese girdling roots which can slowly lead to dieback maple has been cultivated in temperate areas and mortality. JULY around the world since the 1800s. This tree is one of the most common features in landscapes of the  Early season aphid infestations also occur. Deep water every 7-10 days when rain is lacking. Pacific northwest and British Columbia. There are  Armillaria is also known to cause decline and Add mulch around trees and shrubs if mulch is many varieties with differences in leaf color, leaf death of this species. shape, growth habit, and bark appearance. less than 2" deep.  Stressed plants may be attacked by ambrosia Culture beetles. Monitor and treat plants for spider mites.  Performs best in well-drained but moist organic Bartlett Management Practices Ornamentals - Prune as needed. soil, at slightly acidic pH.  There is no direct treatment for verticillium Fruit trees - Continue treatment for diseases and  Variable by species, but often suffers from leaf wilt, but potassium phosphite soil treatments insects. Remove water sprouts and suckers. margin scorching in full sun locations. will help prevent infection and slow decline in  Deep shade will cause colored foliage to revert infected plants. Roses - Continue foliar disease and insect back to green. Expose root collars and inspect for/remove any control treatments.   Shallow roots will benefit from mulch to reduce girdling roots. Holly - Monitor and treat for scale insects and soil temperature and moisture fluctuations.  Mature specimen should be pruned so that the leaf miners. Concerns unique branching architecture is visible. AUGUST  Verticillium wilt is the most common and lethal  When soil organic matter level is less than 5%, pathogen of this species. add mulch and organic matter. Continue deep watering every 7-10 days when rain is lacking.  Phytophthora root rot and anthracnose foliar  Treat preventatively against ambrosia beetles disease, defoliating caterpillars, and leaf when plants are stressed. Do not fertilize woody plants at this time. feeding beetles are also common health issues. Treat for fall webworm and tent caterpillars. Monitor newly planted shrubs and trees for insects and disease. Get Electronic Tree Tips It’s easy to enroll in our paperless program for electronic Tree Ornamentals - Conduct final pruning to shape Tips. Find your 7-digit client code in the yellow box on the shrubs. back page. Then, log on to www.bartlett.com/newsletter Fruit trees - Treat ripening fruit to prevent (select US), click on the registration link and sign up using brown rot. your client number and zip code. If you ever want paper service again, just advise us. Roses - Continue fungal disease management. Bartlett’s Tree Research on the West Coast Things To Do, Places to Go... Three years after expanding the Bartlett Tree Trials in Oregon are focused on managing with Trees! Research Laboratories to provide more local sucking insects such as lacebugs and aphids research and technical support to our Western using safe, non-neonicotinoid options. Western operations, many projects are in the works. Based Canada research is focused on fruit tree disease Hoyt Arboretum, in the San Francisco bay area, Dr. Drew Zwart has management, evaluating materials that induce Portland, Oregon been setting up trials throughout the west coast systemic resistance in the trees in order to reduce Founded in 1928 to to address local needs conserve endangered with local research. species and educate We are investigating the the community, Hoyt potential benefits of plant Arboretum encompasses growth regulators (PGRs). 189 ridge-top acres, accessible by 12 miles of Long used as a tool for hiking trails. The arboretum is home to over 200 slowing tree growth or plant families and 2,068 species - 63 of which keeping trees in proportion are listed globally vulnerable or endangered to their given space, by the International Union for Conservation of additional benefits of Nature and Natural Resources (IUCN). Beautiful PGRs include a reduction and serene in all seasons, Hoyt Arboretum is in water usage and more easily accessible from anywhere in the Portland tolerance to extended metropolitan area. moisture stress. Smaller www.hoytarboretum.org and thicker leaves and an increased wax layer are a few of the effects of PGRs that help treated plants Multiple shrub species are involved in the PGR vs. drought stress trials. cope better with dry periods. Washington Park Arboretum, We are looking at materials to reduce drought dependence on sprayed fungicides for managing Seattle, Washington stress in trees, using heat and drought sensitive diseases like apple scab or cherry brown rot. Japanese maples to expand on work done by our The Washington Park Bartlett Lab colleagues in the United Kingdom. Overall, the last few years have been busy but Arboretum is a hidden In San Jose we are also testing some recently rewarding. Addressing local needs with local gem on the shores of Lake registered systemic options for management research has always been a goal of the Bartlett Washington, jointly managed of sycamore anthracnose. In Napa we are labs, and we are happy to bring that tradition to by the University of Washington Botanic Gardens investigating new materials for management of our Western operations. and the City of Seattle. Its 230 acres contain a fireblight of pears. dynamic assortment of plants found nowhere else. Among them is one garden for Asiatic maples and another for Japanese maples. Wondering why? It’s because the Japanese Stihl Tour des Trees Coming to Our maple, Acer palmatum, has many, many unique North Carolina Research Laboratories cultivars - more than enough for an entire garden showcasing just this one species. by Frazer Pehmoeller, Arborist Representative There are free 60-90 minute arboretum tours on The Stihl Tour des Trees is a weeklong 500-600 mile cycling tour Sundays, from January through November. No to benefit the Tree Research and Educational Endowment Fund preregistration necessary. (TREE Fund). Last year’s tour raised over $340,000 to support tree depts.washington.edu/uwbg/gardens/wpa research and arboricultural education. We are honored that this year the Tour des Trees will start and finish at the Bartlett Tree Research Laboratories in Charlotte. In addition to cycling the bike route, there will be numerous educational outreach opportunities at schools and parks, and just like Johnny Appleseed, we’ll plant numerous trees along our trail throughout the Carolinas. While Bartlett employees have ridden for this cause before, for the first time we have an official TEAM BARTLETT. Each team member must raise a minimum of $3,500 along with training for their weeklong ride in October. Every dollar raised goes directly to the TREE Fund and its mission.

Tree planting events are part of the Tour des Trees.

For more information visit: www.stihltourdestrees.org or www.treefund.org To support Team Bartlett: www.crowdrise.com/stdtteambartlett2016/fundraiser/ Compliments of

TREE TIPS

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Structural Pruning: The Key to Strong Trees by Neil Hendrickson, PhD

Structural pruning is a type of pruning typically Structural pruning is the technique used to performed on living branches of young to middle- guide developing shade trees back into a strong aged shade and ornamental trees. The objective architecture. Live leaders and lateral limbs are is to create a strong and healthy structure so that “subordinated” or reduced, to slow their growth, so trees are sturdier under wind and other loads, and that the main stem can develop dominance again. less prone to failures, and so they can live full and Similar principles apply to pruning of ornamental useful lives in the landscape. trees. They can often grow to become wider than In a natural forest trees tend to crowd each other, they are tall, and more prone to breakage. and in their race for the sky, they tend to maintain Structural pruning can reduce the crown spread a single main stem with lateral limbs small so that the likelihood of failure under wind or relative to the main stem. When these trees grow storm loads is reduced. It can also shape the in the landscape, there’s less crowding, and they tree to fit its place in the landscape, providing can develop structural weaknesses such as co- desired benefits. dominant stems (or V-crotches), and lateral limbs that are more than half the diameter of the main The sooner in the life of the tree that structural stem and known to be more prone to failure. pruning is started, the easier and cheaper it is. Waiting until the tree is mature often means bigger As the name implies, structural pruning helps pruning cuts, cabling and much greater expense. trees develop strong structure. It also can shape a tree to fit its spot in a landscape.

published by THE F. A. BARTLETT TREE EXPERT COMPANY (877) BARTLETT (877-227-8538) in U.S. and Canada • www.bartlett.com © 2016 The F. A. Bartlett Tree Expert Company For Tree Tips information contact [email protected]. PNW2