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Shoot-Sucking-Galling-Insects

Douglas-fir tussock moth (orgyia pseudotsugata)

Biology/ecology

  • Univoltine (overwinter as eggs)
  • Egg hatch and bud burst synchronized
  • Newly emerged larvae disperse aerially ("ballooning" or "silking")
  • Larvae develop through 4-6 instars
  • Pupation occurs during July in cocoons partly composed of larval hairs*
  • Wings emerge in August; females wingless, emit pheromones
  • Egg laid in frothy mass mixed with female body hairs on old cocoons

Management of Douglas fir tussock moth impacts: Direct Control:

  • Aerial application of a biological insecticide
    • Nuclear polyhedrosis virus (NPV)
    • Will naturally occur over time

Indirect control:

  • Selectively harvesting of stands based on risk rating
    • Susceptible sites
    • Optimal larval development
      • Low elevations
      • East slopes
      • Ridge tops
    • Optimal larval dispersal
      • High tree density
      • Large crowns
      • High % DF, Fir

Shoot, sucking, and galling insects

General Introduction​

Seldom direct tree mortality (occasional seedlings)

  • Growth loss, longer rotation
  • Malformation, sawlog degrade
  • Impacts greatest on young trees
  • Indirect mortality via competition

Injury is often positively related to tree vigour

  • Injury increased by fertilization, irrigation
  • Injury greater in widely spaced stands

Native species in BC

  • Coleoptera
  • Lepidoptera
  • Diptera

Impact example​

  • Loss of merchantable volume, total volume might not be affected

White Pine Weevil (spruce weevil), Pissodes strobi (Coleoptera: Curculionidae)​

Hosts:

  • Sitka, white and Engelmann spruce
    • Trees 1.5 - 10m tall preference

Distribution

  • Transcontinental

Injury patterns:

  • Weevils prefer vigorous, open-growth trees
  • Larvae feed in the phloem tissue of leaders, causing dieback of at least 2-years growth
  • ** CONTINUE SLIDES

Biology/ecology:

  • Univoltine
  • Adults deposit their eggs in punctures near the tip of the previous years leader
  • Resin droplets associated with these wounds
  • Larvae feed gregariously down the leader in the phloem, girdling the stem
  • Mature larvae excavate cavities in the wood and pith and line them with wood chips
  • By mid-summer the current years leader will appear wilted

Life cycle:

Management

  • Intiate dense plantations (2.5m spacing or less)
  • Retain volunteer shade trees
  • Mixing spruce with other suitable species is recommended
  • Thinning and brush control should be delayed as much as possible (beyond 15 years where the trees are no longer as susceptible)
  • When available, resistant trees should be used, always in mixtures with susceptible stock
  • Pruning of multiple tops to leave only one leader should be conducted when economically feasible

Sucking/galling insects general introduction​

Nature of feeding

  • Piercing.sucking mouthparts
  • Plant part/tissue specialization
  • Often preference for healthy/vigorous hosts

Nature of injury

  • Nurient loss
    • Inefficient feeders due to low N of substrate
  • Patogen transmission
  • Phytotoxins and allergic reactions
  • Primarily hemiptera (gallers also = hymenoptera and Diptera)
  • Most serious pests are introduced

Hemiptera

  • Small
  • Polymorphic
    • Associated with different hosts, seasons, densities
  • Pronounced sexual dimorphism
  • Relatively short generation times
  • Many parthogenetic (asexual reproduction)
    • Obligate and facultative
  • Viviparous (produce live young) and/or oviparous (lay eggs)
  • Passive dispersal
  • High reproductive capacity
  • Greatly reduced body parts
  • Complex life cycles
  • Galls -- adaptation to sessile lifestyle

Terminology

  • Heteroecious = alternating between hosts
  • Monoecious = remains on one host
  • Holocyclic = complete life cycle, sexual reproduction
  • Anholocyclic = always asexual
  • Alate = winged insect
  • Apterate = wingless insect

General management considerations

  • Easily introduced (hard to detect)

  • Outbreaks closely associated with changing host susceptibility

  • Pheremones unknown/unavailable

  • Natura enemies often introduced

    • Ladybird beetles, lacewings

  • Some species protected from predators by ants

    • Some ants farm aphids

  • Injury/damage to:

    • Intensive production systems
    • Ornamentals, nurseries, christmas trees
    • Biodiversity (i.e. invasives)

Hosts

  • ALl true firs (all ages); abies amabilis and A. grandis attacked most frequently, A. lasiocarpa least tolerant to attack

Distribution

  • Introduced from Europe around 1900, expanding range;
  • Infestation expected throughout south-western BC; range expansion with CC

Injury patterns

  • crowns appear chloratic thin, with stunted terminals and possibly dead tops
  • Swellings (gouting) occur around buds and branch nodes

Balsam woolly adelgid​

Biology/ecology

  • Multivoltine (2-4 generations / year) parthonogenetic, monoecious, anholocyclic, oviparous
  • For 1-2 years, nymphs disperse to new locations by wind, birds and mammals, and by crawling
  • After dispersal, nymphs insert tube-like mouthparts into tree and remain sessile produce wooly secretions (need to add more notes from slides here)