WHAT’S WRONG WITH MY CONIFER? City of Seattle IPM Pest Recertification 2019, presented by Bess Bronstein, [email protected]

DISEASE / PEST AFFECTED PLANTS SYMPTOMS / SIGNS MANAGEMENT FUNGAL DISEASES western gall rust 2 & 3-needled pines • chlorotic and thinning foliage • prune out and destroy galls Endocronartium harknessii : jack pine (Pinus banksiana) • branch dieback • remove infected trees from Peridermium harknessii shore pine (P. contorta v. contorta) • poor shoot growth stands of susceptible pines lodgepole pine (P. contorta v. latifolia) • rough, globular galls on branches DESCRIPTION: Existing galls mugo pine (P. mugo) and trunk produce spores in spring and infect Scotch pine (P. sylvestris) • galls are orange or yellow when the youngest new terminal shoot Austrian black pine (P. nigra) the fungus is fruiting in spring growth. Cool moist weather is most ponderosa pine (P. ponderosa) conducive to infection. white pine blister rust 5 needled-pines: most susceptible are- ON PINES • remove alternate hosts near Cronartium ribicola whitebark pine (Pinus albicaulis) • needles turn yellow, drop early pines sugar pine (P. lambertiana) • diamond-shaped cankers develop • plant in sites with good air DESCRIPTION: The fungus Western white pine (P. monticola) at site of infected needles circulation requires 2 plant hosts (5-needled Eastern white pine (P. strobus) • abundant pitch flow at canker sites • prune and destroy infected pines and currants/gooseberries, limber pine (P. flexilis) • orange spore masses appear at branches or Ribes). There are multiple spore bristlecone pine (P. aristata) cankers in spring • remove severely infected producing stages. In late summer foxtail pine (P. balfouriana) • orange hyphae appear in fall at pines spores are spread by wind from base of infected needles • plant resistant pine species Ribes to pines. Needles are alternate host: and varieties infected, and over multiple years currant, gooseberry (Ribes spp.) ON RIBES the infection spreads down the • chlorotic leaf spots on top of leaves branch, forming new cankers. • orange spores appear on leaves of Cankers continue to expand, currants/gooseberries in spring causing branch dieback. and summer incense cedar-broom rust Rose family: common hosts are- ON ROSACEOUS PLANTS • remove the alternate host (pacific coast pear rust) serviceberry (Amelanchier spp.) • circular yellow-orange leaf spots on Gymnosporangium libocedri hawthorn (Crataegus spp.) leaves, fruit and shoots late spring quince (Cydonia spp.) through summer DESCRIPTION: The fungus apple / crabapple (Malus spp.) • fruit deformed, often drop from tree requires 2 plant hosts (Rosaceae pear (Pyrus spp) family and incense cedar). Incense mountain ash (Sorbus spp.) ON INCENSE CEDAR cedar infections produce spores in • gelatinous orange masses on early spring and infect the other alternate host: foliage in spring hosts. New spores that develop on incense cedar (Calocedrus decurrens) • occasional development of deciduous hosts infect the incense witches’ broom cedars in late spring, but do not appear until the following year.

juniper-pear trellis rust Rose family host: ON PEAR • remove the alternate host Gymnosporangium sabinae pear (Pyrus spp) • circular yellow-orange leaf spots on within a 1,000 foot radius top of leaves, fruit and shoots late DESCRIPTION: The fungus alternate host: spring through summer requires 2 plant hosts (pear and juniper (Juniperus spp.) • raised fungal growth on leaf juniper). Spores are released from underside in late summer perennial galls on junipers in early • fruit mummification spring and infect pears. Spores on the pear leaves disperse in late ON JUNIPER summer and can cause new • gelatinous orange masses on infections in junipers. foliage and elongated stem galls in spring diplodia tip blight 2 & 3-needled pines • new needles in spring are small • keep trees healthy (attacks Diplodia sapinea mugo pine (Pinus mugo) and discolored older, stressed out (Sphaeropsis sapinea) Scotch pine (P. sylvestris) • new shoot tip is distorted, specimens) Austrian black pine (P. nigra) continues to dieback into stem • prune out infected branches DESCRIPTION: The fungus enters ponderosa pine (P. ponderosa) • dead needles stay on tree during dry periods through wounds and stomata, Japanese black pine (P. thunbergii) • visible black fruiting bodies moving from lower branches (pycnidia) often seen on needles, upward. other conifers, when stressed cones and twigs Douglas fir (Pseudotsuga menziesii) Norway spruce (Picea abies) Colorado spruce (Picea pungens) keithia blight most susceptible is- • small light brown spots appear in • avoid planting susceptible Didymascella thujina western red cedar (Thuja plicata) wet spring on year old scales varieties (T. plicata • black fruiting bodies develop on the ‘Excelsa’, T. plicata DESCRIPTION: Spores infect new also may infect- infected scales, eventually drop out ‘Atrovirens’) foliage from spring through fall, eastern white cedar (Thuja occidentalis) and leave dark pits • clean out dead foliage whenever moisture is high. Pt. Orford cedar • dead foliage drops off in fall Symptoms (Chamaecyparis lawsoniana) juniper twig blight many juniper species • tips die back • avoid overhead watering (phomopsis tip blight) • lesions form where dead tissue • prune out and destroy Phomopsis juniperovora DESCRIPTION: While symptoms are meets live tissue infected twigs (Diaporthe juniperivora) similar from both pathogens, they do • black fruiting bodies visible on • avoid pruning during wet have some differences. Phomopsis dead tissue weather (kabatina tip blight) infections occur in wet springs and infect Kabatina juniperi young new growth, not older growth. Kabatina infections are in fall, but See DESCRIPTION next column. symptoms don’t appear until spring. They infect through wounds.

lophodermium needle cast Scotch pine (P. sylvestris) • yellowing and browning of needles GENERAL NEEDLE CAST Lophodermium seditiosum ponderosa pine (P. ponderosa) in spring, fall off in summer MANAGEMENT: • infected needles have black, Lophodermella needle cast lodgepole pine (P. contorta v. latifolia) football shaped fungal structures • do not plant in low areas or Lophodermella spp. ponderosa pine (P. ponderosa) with a center slit for spore release areas with poor air western white pine (P. monticola) • severely infected trees may have a movement DESCRIPTION: Symptoms of ‘lion-tail’ appearance as only • weed and thin canopy to these 2 pathogens are similar. current season needles remain reduce conditions that favor Needles are infected in fall, and humidity symptoms show the following • space plantings to provide spring. Needles fall off, or ‘cast’ good air circulation during summer. Lower branches • clean up and destroy fallen are more severely affected. needles in branch crotches and on the ground rhabdocline needle cast Douglas fir (Pseudotsuga menziesii) • newly infected needles may show • prune and destroy infected Rhabdocline spp. tiny yellow spots in late summer twigs and branches, as well and fall as lower branches DESCRIPTION: The fungus • needle spots develop into reddish- survives year to year on needles. brown splotches by the following Infection occurs in summer, with spring minimal visible symptoms. By the • orange fungal structures visible following spring, symptoms are when blotches swell and split visible, and new spores are released. Diseased needles drop by midsummer.

Swiss needle cast Douglas fir (Pseudotsuga menziesii) • infected needles vary from yellow- Phaeocryptopus gaeumannii green to brown and may hang on for 2-3 years DESCRIPTION: Infection occurs • older brown needles fall off in late in spring through stomata, but summer symptoms are generally seen on • tiny black fruiting bodies appear on one year old or older needles. the underside of the needle along the midrib in late winter to spring

INSECT PESTS balsam woolly adelgid silver fir (Abies amabilis) • swollen, knobby areas at nodes • prune out smaller affected Adelges piceae balsam fir (A. balsamea) and tips of branches branches fraser fir (A. fraseri) • sparse foliage and stunted growth • hose off infested trees with DESCRIPTION: These adelgids grand fir (A. grandis) • eggs are covered by white, cotton- strong stream of water are female, wingless insects. They alpine fir (A. lasiocarpa) like tufts • introduce predator beetles overwinter as nymphs, mature to and syrphid fly larvae adults in spring, and then lay eggs. They are immobile except in the crawler stage, so damage is often seen in the same areas of the tree year after year. There are 2-4 generations per year. hemlock woolly adelgid western hemlock (Tsuga heterophylla) • premature needle drop • prune out smaller affected Adelges tsugae • foliage color becomes a dull green branches • white, wooly tufts cover adults and • introduce predator beetles DESCRIPTION: This adelgid rarely eggs on needles, bark and stems • use insecticidal soap and kills trees in the PNW. Adult horticultural oil sprays in females overwinter under wooly dormancy prior to new tufts, and crawlers emerge in growth spring and early summer. cooley spruce gall adelgid several spruce species, but in PNW- • galls develop at tips of spruce • prune out small affected Adelges cooleyi Sitka spruce (Picea sitchensis) branches in spring areas, especially before • residual galls from previous years galls crack open DESCRIPTION: Immature females alternate host- stay on tree, resemble cones • introduce predator beetles overwinter either on spruces (near Douglas fir (Pseudotsuga menziesii) • discoloration and distortion of terminal buds) or on Douglas fir Douglas fir needles (on undersides of needles). Eggs • nymphs enclosed in new galls; are laid in the spring. Newly seen if gall is cut open hatched nymphs that eat on • galls that crack open once dried (in spruce cause galls to develop in summer) release adults the new growth, and nymphs on Douglas fir cause needle damage. eastern spruce gall adelgid several spruce species, but in PNW- • small galls (resemble pineapples) • prune out small affected Adelges abietis Norway spruce (Picea abies) develop at base of new growth in areas, especially before spring galls crack open DESCRIPTION: This adelgid does • galls can weaken stems, so may • introduce predator beetles not do excessive damage in the see breakage after storms PNW. Because galls are at the • nymphs enclosed in new galls; base of new growth, there is seen if gall is cut open occasional stem breakage.