Forest Health Management International Forest Health Issues By William M. Ciesla Forest Health Management International Forest Collins, CO Progreen Expo - 2018

Today’s Program Bark beetles Conifer defoliators Broadleaf defoliators Forest diseases Emphasis – how to recognize pest agent and its damage

Bark beetles (Coleoptera:Curculionidae:Scolytinae) Adult Larva

Major bark beetle pests of Colorado’s forests Common Name Scientific name Host tree(s) Mountain pine beetle Dendroctonus ponderosae Limber, lodgepole, ponderosa pines Spruce beetle D. engelmannii Engelmann spruce Douglas-fir beetle D. pseudotsugae Douglas-fir Western pine beetle D. brevicomis Ponderosa pine Pinyon ips Ips confusus Pinyon pine Fir engraver Scolytus ventralis White fir Western balsam bark beetle Dryocoetes confusus Subalpine fir

Pitch tubes are an indicator of host resistance Mass Attack Pitch tubes are an indicator of host resistance

Bark beetle galleries are distinct Douglas-fir beetle Fir engraver beetle Mountain pine beetle Pinyon ips.

Blue stain fungi introduced by bark beetles

Mountain pine beetle, Dendroctonus ponderosae

All native pines except pinyon are hosts of MPB Lodgepole pine Ponderosa pine Limber pine

MPB damage in ponderosa and lodgepole pines

Mountain pine beetle infestations – 1996-2016 Cumulative area of damage = 3.4 million acres Mountain pine beetle infestations – 1996-2016

Mountain pine beetle – 2013 (98,000 acres)

Aftermath of a mountain pine beetle outbreak

Mountain pine beetle attack in an urban area

Mountain pine beetle management Brood destruction Preventative sprays Anti-attractants Forest Management

Spruce Beetle, Dendroctonus rufipennis Eggs Pupa Immature adults Adult

Spruce beetle galleries

Windthrow – Sangre de Cristo Range

Spruce beetle “faders”

Spruce beetle infestations – 2000-2016 Cumulative area of damage = 1.7 million acres Spruce beetle infestations – 2000-2016

Douglas-fir beetle, Dendroctonus pseudotsugae Aerial view of damage Galleries

Pinyon ips, Ips confusus Adults Damage Galleries Damage

Fir engraver beetle, Scolytus ventralis Aerial view of damage Host tree – white fir, Abies concolor Galleries

Underlying causes of bark beetle outbreaks Condition of the forest Mature/overmature forests Overstocked forests Fresh windthrow Wildfire Outbreaks of defoliating insects Climatic factors Drought/excess precipitation Mild winter temperatures Climate change?

Western spruce budworm, Choristoneura freemani Larvae Pupa Adult

Defoliation by western spruce budworm

Douglas-fir tussock moth, Orgyia pseudotsugata Larva Pupa Adult female/egg mass Adult male

Douglas-fir Tussock Moth (DFTM) Outbreaks Outbreaks are cyclic – occur at 7-10 year intervals Duration – 1-3 years Outbreaks typically collapse due to a virus infection An outbreak in occurred CO between 2004-2008 Defoliation detected in 2014 Major outbreak – 2015, collapsed 2016

Douglas-fir tussock moth, Rampart Range - 2015

Douglas-fir tussock moth, Perry Park, 28 June 2015

Tussockosis due to exposure to DFTM larval hairs

DFTM activity in 2015 – 26,000 acres Boulder Denver Colorado Springs DFTM activity in 2015 – 26,000 acres

DFTM pupal cases and egg masses on building

Pine sawflies, Neodiprion spp, Zadiprion spp. Larvae Pupae Eggs Adult Male Adult female

Light defoliation by Neodiprion autumnalis, Elbert Co.

Heavy defoliation by Neodiprion autumnalis, Elbert Co. - 2014

Same stand - August 2015

Bull pine sawfly, Zadiprion townsendi, Stove Prairie

Defoliators of Aspen

Western tent caterpillar, Malacosoma californicum

Western tent caterpillar, Life stages Egg Larva Pupa Adult

Other host plants of western tent caterpillar Mountain mahogany Wild currant Bitterbrush Choke cherry Gambel oak Other woody plants

Large aspen tortrix, Choristoneura conflictata Larva Rolled leaf Pupa Adult

Defoliators of Gambel oak and other woody plants

Fall cankerworm, Alsophila pometaria, life stages Egg Larva Adult - male Adult - female

Defoliation of Gambel oak by fall cankerworm near Castle Rock

Oak leaf roller Archips semiferanus

Effects of Forest Defoliation Defoliation is unsightly Large numbers of larvae can be a nuisance Growth loss Branch dieback or top kill Tree death (usually following successive defoliation)

Tree mortality due to DFTM– northern Rampart Range

Aspen mortality following 7 years of WTC defoliation North Purgatory River Basin

Management of Forest Defoliators Larvae of moths and butterflies are susceptible to Bacillus thuringiensis (Bt) Sawfly larvae are not susceptible to Bt -use chemical insecticides (malathion, Orthene, Permethrin, Sevin, Warrior [Lambda-cyhalothrin]) Timing is critical for control of forest defoliators Aerial vs. ground spraying

Caterpillars vs. Sawflies Caterpillars: 5 or fewer prolegs Sawflies: 6 or more prolegs

Timing of application is critical Apply spray after egg hatch Not when larvae are mature Desired result Not this

Aspen discoloration, Bull Mountain

Marssonina leaf blight of aspen

Dwarf mistletoes, Arceuthobium spp. A. americanum – Lodgepole pine A. vaginatum – Ponderosa pine A. douglasii – Douglas-fir A. cyanocarpum – Limber pine Dwarf mistletoes, Arceuthobium spp.

Witches brooms caused by dwarf mistletoe infection

Damage caused by dwarf mistletoes Deformity Growth loss Tree mortality Increased susceptibility to bark beetle attacks

Dwarf mistletoe management Timely harvesting of infected stands Removal of infected regeneration

Questions, comments?

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