Fall 2019 Update

VCE - Culpeper Horticulture: Fall Update Volume 3, Issue 4 – Fall 2019 Comments or Questions? Please call or email: A Glance inside this Issue Ashley Appling, Extension Agent ANR, Horticulture: Culpeper County Office at What is up with my oak tree? 1 (540) 727-3435 Ext. 355 or [email protected] Also serving Madison and Orange Counties Bagworms 2 If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact Ashley Appling at 540-727- Look out for the Spotted Lanternfly 4 3435 during business hours of 8 a.m. and 5 p.m. to discuss accommodations 5 days prior to the event.*TDD number is (800) 828-1120. What is up with my oak tree? Our office fielded many questions throughout 2019 about oak trees dying in landscapes across Culpeper and Orange Counties. We have received numerous stories about white and red oaks looking fine in early summer and then declining suddenly. This decline is most apparent when leaves begin to brown, branches begin to die, and bark begins to peel away from the trunk. I have used the word decline throughout the last couple sentences, and it is appropriate because oak decline is the catch-all term for these issues. Oak decline is the gradual failure of a tree that results from a combination of predisposing factors, inciting factors, and contributing factors. Predisposing factors include poor soil (including soil compaction), topography, and competition (which would include grass competition). Inciting factors rarely kill the tree outright, but help initiate decline by reducing growth, food reserves in branches or roots, and canopy or root dieback. Some examples of inciting factors are frost, drought, defoliating insects (such as jumping oak gall, Figure 1. Armillaria root rot. Photo by Nicholas Brazee, UMass gypsy moth, and orange Extension (February 2018) striped oak worm), and root zone disturbance. Contributing factors come into play after predisposing factors and inciting factors have already weakened the tree. These factors are usually the last nail in the coffin and 1 are sometimes blamed for the death of the tree. Examples of contributing factors include secondary insects or diseases, such as two-lined chestnut borer and Armillaria root rot (Figure 1). The general observation over 2019, was that the majority of dying oaks were exposed trees, in yards or fields, not trees in forest settings. Trees in yards or fields have the predisposing factors of soil compaction and grass competition. White oaks seemed to have had a tougher time in the summer of 2019, compared to red oaks. White oaks in particular have had to deal with as much as five years of jumping oak gall (orange bumps on the underside of leaves caused by wasps), which leads to reduced leaf area or complete defoliation. Trees can handle this leaf damage for a year or two years but beyond that damage is significant. In addition to the jumping oak gall, 2018 and the spring of 2019 were record setting in the amount of rain fall we received. This record setting rain fall lead to saturated root zones in areas that are generally considered drier sites. White oaks in particular are not tolerant of wet feet, these saturated conditions help contribute to fungal root infections. Then we had our very dry summer of 2019, which was the final domino to fall for many oaks in our area. All of these factors mentioned and some factors that may be unique to your site, helped contribute to the decline and death of oaks across our area and Northern Virginia. It is very sad to see our mighty oaks decline and die, but sometimes all of these factors add up at just the right time. For more information, please view the following articles or contact your local extension office (http://ext.vt.edu/offices.html): • Chamberlin, L. Oak Decline in Virginia. Virginia Department of Forestry. 2018. https://forestupdate.frec.vt.edu/content/dam/forestupdate_frec_vt_edu/newsletter/archiv es/2018/32_2/Chamberlin.pdf • Frank, S. and S. Bambara. Orange striped oak worm. NC State Extension. 2016. https://content.ces.ncsu.edu/orangestriped-oakworm • Pellitteria, P. Two-lined chestnut borer. Wisconsin Horticulture Division of Extension. 2012. https://hort.extension.wisc.edu/articles/two-lined-chestnut-borer/ • Rajotte, E. Armillaria root rot. Penn State Extension. 2017. https://extension.psu.edu/armillaria-root-rot • Russell, H. and J. Smith. Jumping oak gall causing damage to white oak. MSU Extension. 2013. https://www.canr.msu.edu/news/jumping_oak_gall_causing_damage_to_white_oak Bagworms Thyridopteryx ephemeraeformis, commonly known as the common bagworm or evergreen bagworm, can be found feeding on 50 families of deciduous and evergreen trees and shrubs. The most commonly infested species in Virginia include junipers, arborvitae, cedars, pine, hemlock, spruce, Chinese elm, and honeylocust. Damage consists of increasing defoliation from late June to August. Stripping of the leaves is most noticeable in the upper branches of trees and shrubs, along with the presence of the 1 ½ in. bags (Figure 2) from late summer through the following spring. 2 Evergreen bagworms often go unnoticed in the landscape because the female is wingless and enclosed in her bag throughout her life. The bags for both females and males are a brown color that remain small (less than ¼ in.) for most of the year. The adult male does have wings and emerges from the bag in late summer as a hairy, charcoal brown moth (Figure 3). This is about the time when most people begin to notice the infestation in their trees and shrubs. The best time to treat for evergreen bagworms is in early to mid-June, as Figure 2. Evergreen bagworm. Photo by Eric Day, the larvae begin to construct their Virginia Cooperative Extension (VCE Publication 2808- bags. If left untreated, the larvae 1008) continue to feed and grow in size until August when pupation occurs. The adults are active in late August and September but the female remains protected by the bag, which is not easily penetrated with insecticidal sprays. The only control option in September through winter is to remove the bags by hand, burn or dispose of the bags in seal trash bags. Insecticidal sprays can be effective the following year in late May to early June. Please consult the 2017 Virginia Cooperative Extension (VCE) Pest Management Guide for chemical control options - Figure 3. Evergreen bagworm adult male. Photo by Curtis Young, Ohio State University http://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/456-018-17-home- grounds.pdf. For more information, please view the following articles or contact your local extension office (http://ext.vt.edu/offices.html): • Day, E. Bagworm. Virginia Cooperative Extension (VCE) Publication 2808-1008 (ENTO- 83NP). 2014. https://pubs.ext.vt.edu/2808/2808-1008/2808-1008.html • Moffis, B. and S. Arthurs. Featured Creatures Bagworm. University of Florida Department of Entomology and Nematology. 2016. Assessed August 11, 2017. http://entnemdept.ufl.edu/creatures/MISC/MOTHS/bagworm.htm • Spruce Problems (Pest and Cultural Issues). University of Illinois Extension Plant Clinic Report. Assessed August 11, 2017. https://web.extension.illinois.edu/plantclinic/downloads/Plant%20Clinic%20Report%20S pruce.pdf 3 Be on the lookout for Spotted Lanternfly 4 .

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