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Orgyia Pseudotsugata Defoliators II ÷ Lecture outline/goals: o The budworm complex – a closer look • Eastern spruce budworm • 2-year cycle budworm • Western spruce budworm – Past and present outbreak condiEons • Blackheaded budworm o Douglas-fir tussock moth 1 Defoliator acEvity 2015 Area of defoiation (ha) Defoliators BC Canada Eastern Spruce Budworm 0 6,726,007 2-yr Cycle Budworm 46,420 46,420 Western Spruce Budworm 9,135 9,135 Blackheaded Budworm 301 301 Conifers Douglas-fir Tussock Moth 0 0 Western Hemlock Looper 0 0 Aspen Leaf Miner 942,085 942,085 Forest Tent Caterpillar 609,999 5,199,101 Hardwoods Total = 12,923,049 Budworms Family Tortricidae o Complex of species o Complicated life cycles o Diverse Hosts o Extensive distribuEons C. fumiferana C. biennis C. orae C. freemani Eastern spruce budworm (Choristoneura fumiferana) ÷ Hosts o Subalpine fir, interior spruce (all ages) ÷ DistribuEon o Boreal forest (north-eastern BC) ÷ Injury paerns o Young larvae mine needles, buds, new cones; feed on young foliage following bud burst o Older larvae may feed on old foliage if young foliage is depleted (prefer young) o Crowns of damaged trees appear reddish-brown from June to Sept o IniEal symptoms of defoliaon visible in tree tops and at branch Eps o AZer several years of defoliaon – reduced cones, growth loss, top kill or mortality (esp. immature/suppressed trees) Eastern spruce budworm (Choristoneura fumiferana) ÷ Biology/ecology o UnivolEne (overwinter as L2’s) o Larvae develop through 6 instars (L1 to L6) before pupaon; foliage webbed together during feeding o Pupaon within foliage o Female moths lay eggs in masses on the underside of needles in a shingle-like paern o Larvae (L1’s) eclose 1 – 2 weeks aer egg lay, do not feed, spin hibernacula, moult to L2 and overwinter o Larvae (L2 – L6) feed the following spring on buds, developing cones, then new foliage Choristoneura fumiferana life cycle Egg hatch/L1’s spin hibernacula: Egg lay: August L2 feeding: August May Pupation: L2 – L6 feeding: July - August May - July 2-year cycle budworm (Choristoneura biennis) ÷ Hosts o Subalpine fir, interior spruce (all ages) ÷ DistribuEon o Subalpine and boreal habitats (W. of Rockies) ÷ Injury paerns o Young larvae mine needles, buds, new cones; feed on young foliage following bud burst o Older larvae may feed on old foliage if young is depleted o Crowns of damaged trees appear reddish-brown from June to Sept (every second year) o IniEal symptoms of defoliaon visible in tree tops and at branch Eps o AZer several years of defoliaon – reduced cones, growth loss, top kill or mortality (esp. immature/suppressed trees) 2-year cycle budworm (Choristoneura biennis) ÷ Biology/ecology o SemivolEne (overwinter as L2’s, L4’s) o Larvae develop through 6 instars (L1 to L6) before pupaon o Pupaon within foliage o Female moths lay eggs in masses on the underside of needles in a shingle-like paern o Larvae (L1’s) eclose 1 – 2 weeks aer egg lay, do not feed, spin hibernacula, moult to L2 and overwinter o Early instars (L2 – L4) feed the following spring on buds, developing cones, then new foliage o L4’s also spin hibernacula and overwinter o Late instar larvae (L4 – L6) feed, complete development during spring of year 2 – Eme of most injury Choristoneura biennis life cycle Egg hatch/L1’s spin hibernacula: Egg lay: August L2-L4 feeding: August May - July L4’s spin hibernacula: July Pupation: L4-L6 feeding: June to July May - June Western spruce budworm (Choristoneura freemani formerly C. occidentalis) ÷ Hosts o Douglas fir (occasionally spruce, western larch, lodgepole pine); all ages of trees ÷ DistribuEon o Southern BC, coast, montane, Columbia forest types ÷ Injury paerns o Young larvae mine needles, buds, new cones; feed on young foliage following bud burst o Older larvae may feed on old foliage if young is depleted o Crowns of damaged trees appear reddish-brown from June to Sept o IniEal symptoms of defoliaon visible in tree tops and at branch Eps o Several years of defoliaon = reduced cones, growth loss, top kill or mortality (esp. immature/ suppressed trees) Western spruce budworm (Choristoneura freemani formerly C. occidentalis) ÷ Biology/ecology o UnivolEne (overwinter as L2’s) o Larvae develop through 6 instars (L1 to L6) before pupaon o Pupaon within foliage o Female moths lay eggs in masses on the underside of needles in a shingle-like paern o Larvae (L1’s) eclose 1 – 2 weeks aer egg lay, do not feed, spin hibernacula, moult to L2 and overwinter o Early instars (L2 – L6) feed the following spring on buds, developing cones, then new foliage Choristoneura occidentalis life cycle Egg hatch/L1’s spin hibernacula: Egg lay: August L2 feeding: August May Pupation: L2 – L6 feeding: July - August May - July Western spruce budworm outbreak history: recent changes ÷ Outbreak first recorded 1909, Vancouver Island 1000 ÷ Increasing frequency and severity ) Western spruce budworm during past century? 3 10 800 o ≈20 years between outbreaks since × 1950 o >10 years outbreak duraon 600 • Note: data reliability good due to proximity of WSBW habitat to long- term human seTlements (but only 100 yrs) 400 o Due to changing climate? • Unknown, but… 200 • Northward shiZ due to shiZing Mapped outbreak area(ha phenological window o Fire suppression? 0 • Fewer ground fires = more understory, more food Year Western spruce budworm control efforts ÷ Btk applicaon ÷ 61,966 ha treated in 2008 (largest Btk applicaon in BC) ÷ Treatment prioriEes based on: o Predicted defoliaon o PotenEal for stands to recover o Stand value (investment) o Stand structure o Wildlife habitat o Recreaon/aestheEc values 15 Blackheaded budworm (Acleris gloverana) ÷ Hosts o Western hemlock and true firs (occasionally Douglas fir); all ages of trees ÷ DistribuEon o Throughout BC (except southern Okanagan); outbreaks most severe along coast ÷ Injury paerns o Larvae feed preferenEally on young foliage in the upper crown o Older foliage consumed when young depleted; enEre trees defoliated during outbreaks o “Wasteful” feeders – enEre needles seldom consumed o Defoliaon over two or more years may lead to top kill and mortality Blackheaded budworm (Acleris gloverana) ÷ Biology/ecology o UnivolEne (overwinter as eggs) o Egg hatch and bud burst synchronized o L1’s mine needles or buds unl L2 o L3’s construct shelters by webbing together parEally eaten needles o Larvae develop through 6 instars o Pupaon occurs during July o Moths emerge in August, mate, lay eggs and die o Eggs overwinter Acleris gloverana life cycle Eggs overwinter Egg lay: Egg hatch: August May Pupation: L1 – L6 feeding: July - August May - July Defoliation history of Acleris gloverana in BC Douglas-fir tussock moth (Orgyia pseudotsugata) ÷ Hosts o Douglas fir; all ages of trees ÷ DistribuEon o Warm, dry areas of southern BC ÷ Injury paerns o Larvae feed preferenEally on young foliage in the upper crown o Mature larvae require some feeding on older foliage; enEre trees defoliated during outbreaks o ConsumpEon of new and old foliage together increases likelihood of tree mortality o ATacked trees turn reddish-brown then greyish purple from July to Sept o Secondary agents oZen associated with DFTM Douglas-fir tussock moth (Orgyia pseudotsugata) ÷ Biology/ecology o UnivolEne (overwinter as eggs) o Egg hatch and bud burst synchronized o Newly emerged larvae disperse aerially (ballooning) o Larvae develop through 4 - 6 instars o Pupaon occurs during July in cocoons partly composed of larval hairs* o Moths emerge in August; females wingless, emit pheromones o Eggs laid in frothy mass mixed with female body hairs on old cocoons o Eggs overwinter *note: tussock moth hairs are significant irritants Orgyia pseudotsugata life cycle Eggs overwinter Egg lay: Egg hatch/larval dispersal: August May Pupation: Larval feeding: July May - July Douglas-fir tussock moth populaon dynamics ÷ Intrinsic cycles – every 8 to 9 years o Delayed density dependence between DFTM and natural enemies o Generalist predators, specific parasitoids, specific NPV o Site and weather condiEons – significant DI perturbaons • Warm, dry condiEons; shallow soils 23 Silivicultural management of Douglas fir tussock moth impacts Species composiEon, planEng; promotes tree/stand resistance (see IPM lecture) Site selecEon based on risk rang SuscepEble Sites Low elevaons East slopes Warm, dry (tree stress) Ridge tops High tree density Large crowns Larval dispersal High % DF, Fir Management Favour soil moisture and nutrient cycling processes Avoid compacEon Thinning Retain slash .
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